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NEW!
MOTION SYSTEM APPLICATIONS
4 AXIS SERVO from
2.25”
IoT, smart components help
improve motion systems Welcome to the (now) 5th annual Motion System Applications special issue. Our editorial team here at Design World puts together four issues on motion control each year, with the last one of the year focusing on motion system applications. Here, we look at some top application examples and how many of the vast array of motion control components, separate or together, are used to tackle some of the most challenging applications in industries from medical devices to semiconductor manufacturing and beyond. One of the biggest and broadest trends impacting virtually all of manufacturing is the so-called Fourth Industrial Revolution, also referred to as the internet of things (IoT) or the industrial internet of things (IIoT). It continues to shape developments across a range of industries, including robotics. Industrial robots and their cobot cousins are being used in the manufacture and production of a broad range of products, including in the automotive industry. This is no surprise given that the first known use of a commercial robot for industrial purposes was in fact in the automotive industry way back in 1961; specifically, a robotic arm installed at a GM plant in New Jersey was used to lift hot pieces of metal from a die casting machine and stack them. In this issue, we look at the way in which motion components and developments therein continue to improve industrial robots, aiding in their adoption in so many new applications. The IoT is also playing a role in improving production processes via machine monitoring. Case in point: A story about a high-speed palletizer where machine monitoring helped increase uptime. Another benefit for material-handling applications is the presence of more powerful and intelligent drives packed with more functions. These smart VFDs are handling tasks that once were the domain of dedicated controllers such as PLCs, including many computation-heavy motion control functions. Such localized control architectures are also easier to troubleshoot than more traditional centralized controllers. Another story looks at the on-going trend of electric and mobile vehicles using more electric motors and other motion components. We hope you find useful what we’ve assembled in this special issue on motion system applications. Do you have any interesting challenges that you or your company overcame? Want to share it with our readers? Get in touch with me via email at mbudimir@wtwhmedia.com or on Twitter at @DW_Motion. And don’t forget that you can find all of the latest motion control news at our motionspecific sites motioncontroltips.com and linearmotiontips.com, as well as bearingtips.com and couplingtips.com.
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PRECISE. ROBUST. AVAILABLE. These new generation CD® Couplings feature zero backlash precision and high torsional stiffness. They answer today’s demanding needs in servo motor applications with high reverse loads and positioning requirements. New clamp style hubs handle increased torque on shafts without using keyways. Manufactured of RoHS compliant materials. Now size, select and see the right CD® Coupling solution for your coupling application with Zero-Max 3D CAD files. Check our FAST deliveries.
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VO LU M E 5 N U M B ER 4
CONTENTS
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MOTION SYSTEM APPLICATIONS IoT in discrete automation...............................8 Motion components in robotics.....................10 Motor drives and PT in AGVs.........................16 Actuators • electric........................................26
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Belts & chains in vertical designs...................28 Brakes • clutches • torque limiters.................30 Controllers in eBikes......................................32 Conveyors in warehouse automation.............34 Couplings in the solar industry.......................38 Drives AC............................................................44 DC............................................................46 Encoders in semiconductor production.........48 Gears..............................................................50
71
Gearmotors for conveying and more.............53 HMIs in cobotic palletizing.............................56 Linear guides • rails • slides • ways...............58 Motors DC............................................................64 Integrated.................................................68 Servo........................................................71
50
Positioning stages • tables • gantries............72 Sensors & transducers....................................76 Shocks & vibration dampers..........................78
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Springs — compression & wave.....................84
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S O LU T I O N S FO R L I N E A R M OT I O N
High precision, high load linear guides and Monocarrier™ actuators
Those are the goals for any automated system. Keep production moving for reliable output. Control quality and costs. In that effort, there’s no more committed partner than NSK. We’ve had our people on the ground and in the plant, for decades – delivering linear motion and integrated automation solutions for handling high loads with speed and repeatable precision. To get the results you need: Longer life. Enhanced productivity. Superior quality. And consistently lower operating costs. With NSK, you stay in motion. You stay in control.
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VP, Editorial Director Paul J. Heney pheney@wtwhmedia.com @dw_Editor
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VP, Digital Marketing Virginia Goulding vgoulding@wtwhmedia.com @wtwh_virginia
Events Manager Jen Osborne jkolasky@wtwhmedia.com @wtwh_Jen
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Senior Editor Miles Budimir mbudimir@wtwhmedia.com @dw_Motion
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VIDEOGRAPHY SERVICES
Senior Editor Mary Gannon mgannon@wtwhmedia.com @dw_MaryGannon Associate Editor Mike Santora msantora@wtwhmedia.com @dw_MikeSantora
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2011 - 2018
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PRODUCTION SERVICES
@DESIGN 6
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Power Transmission, Motion Control and Engine Braking Solutions
Creating A Premier Industrial Company Ameridrives
Deltran
Kilian
Portescap
Twiflex
Bauer Gear Motor
Formsprag Clutch
Kollmorgen
Stieber
Warner Electric
Bibby Turboflex
Guardian Couplings
Lamiflex Couplings
Stromag
Warner Linear
Boston Gear
Huco
Marland Clutch
Svendborg Brakes
Wichita Clutch
Delevan
Jacobs Vehicle Systems
Matrix
TB Wood’s
Nuttall Gear
Thomson
Delroyd Worm Gear
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MOTION SYSTEM APPLICATIONS
Machine monitoring
maximizes high-speed palletizer uptime
Recently, Emerson and Arrowhead Systems partnered on a machine-health monitoring solution to boost the uptime of a highspeed palletizer for container stacking and other primary products. The Busse SJI Viper bulk palletizer and Alpha Turbo depalletizer pair with Emerson’s machine-health monitoring to get greater overall equipment effectiveness (OEE) by monitoring (in real-time) critical motion and pneumatic system parameters — including mechanical actuation speeds, airflow, pressure, vacuum, and motor vibration. System analytics and health
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information is processed at the edge via a local data historian with both local display or remote monitoring on a tablet or smartphone giving operators an easily accessible tool to monitor health. “This solution offers the quickest and most scalable way to increase OEE and ultimately increase the overall production efficiency of plant operations,” says Dana Greenly, director of business development for food and beverage packaging with Emerson’s Automation Solutions business. The new edge-based system has the PACSystems CPL410 at its core to bring all sensor data together for accessibility,
motioncontroltips.com | designworldonline.com
11/18/19 3:37 PM
IoT IN MOTION DESIGNS
Aggressive Work Ethic Developing Leading Products BallscrewsState-of-the-art machining technology, providing in-stock solutions, solutions exact groove profiles by grinding or precision rolling, with protective coating options.
visualization, and analysis. It is customizable and scalable to adapt to any primary product palletizer or packaging line. Real-time monitoring of machine health and diagnostics at the operator’s fingertips eliminates reliance on reactive maintenance practices. Predictive maintenance enables planning for potential issues which otherwise negatively affect the OEE of the packaging line. “Because we have container-handling equipment running at some of the highest speeds in the industry — even to 4,000 cans per minute or more — predictive monitoring of machine health is vital,” says Busse-SJI general manager Scott Chehak. Emerson’s automation technologies impart packaging lines with flexibility by accommodating numerous package sizes and complexities; reducing losses from low product quality and waste; and improving operator and product safety. For more information, visit therobotreport.com and search Arrowhead.
Linear GuidewaysEffective linear motion utilizing precision rolling elements perfecting up/down and side-to-side loads.
For More Information: info@hiwin.com
One of several Emerson solutions for IoT functionality is the Rx3i CPL410 — an edge device combining logic and application in one controller. Its real-time deterministic control is complemented by physics-based analytics to securely connect, collect, and analyze industrial data directly at the machine.
Linear Guideways
Rotary Tables
Ballscrews Ball Splines Harmonic Gearing System
AC Servos & Drives Articulated Robots Crossed Roller Bearings
Linear Motors Single Axis Robots
Positioning
Torque Motors
Measurement Systems HIWIN Grease
Huntley, IL USA 847.827.2270
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Environmental effects on
motion components in robotics Here we outline leading factors affecting the longevity and performance of industrial robot joints.
Recent years have seen continuous demand in numerous industries — automotive manufacturing to computer, communication, and consumer electronics (3C) product fabrication — for industrial robots. Compared to dedicated equipment in traditional production lines, robots have superior operational flexibility and capabilities. So, they’re especially suitable for small-batch production to satisfy rapid response to market changes and consumer needs.
BACK TO BASICS: WHAT MAKES AN INDUSTRIAL ROBOT To review, industrial robots are automatically controlled programmable multipurpose manipulators that move loads in three or more axes. Advantages of using industrial robots include improvements in quality and productivity; reduction in manufacturing variability; savings in raw materials; reduced product lead time; and reduction in long-term total manufacturing costs. In addition, they have been widely used to free human workers from repetitive tasks and dirty or dangerous environments. Increased use of industrial robots has spurred demand for leveraging the technology’s full potential. Case in point: Industrial robots are increasingly used in the motion control industry for optimizing manufacturing throughput. That has in turn driven industrial and scientific efforts to design next-generation industrial robots. Significant advances in actuator and control technology have enabled the evolution of sophisticated modular robot joints. Modular robot joints are standardized yet capable of interfacing
Shown here is a robot in a semiconductor application. Motion controls increasingly take the form of industrial robots for maximizing manufacturing productivity and | courtesy Universal Robots throughput.
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MOTION COMPONENTS IN ROBOTICS
Innovation of Motion Control Components HIWIN® Ball Spline Rolling Guide Motion Component FS, FSR, FBR Type
Modular robot joints can improve robotic flexibility and reduce manufacturing time.
with a myriad other parts and systems. Modularity allows for versatility in design and machine capabilities; adaptability; and ease of assembly. Integrated mechatronic modular joints outperform conventional robotics as well — with higher power density, dynamic performance, and reliability along with lower weight. One caveat is that industrial robots can incur significant upfront investment. Decisive factors when considering the robots to replace expensive human labor are the payback period in capital investment and robot service life. Quick payback and long service life maximize return. Certain motion-component manufacturers are well versed in servomotion components used in the robotic industry. OEM collaborative robot (cobot) designs with light payloads are optimizable by the inclusion of one or more modular robot joints; some such modular robot joints integrate frameless torque motors in the form of alternating current permanent magnet (PMAC) servo motors for simple and safe designs. Careful engineering means some frameless motors are optimized to adhere to space or weight constraints or performance and reliability requirements. Now let’s outline various factors affecting the longevity and performance of industrial robot joints.
THERMAL EFFECTS REDUCE ROBOT LIFE High temperatures degrade industrialrobot life. Consider a mechatronic robot
joint module: This contains a frameless motor, servo drive, dedicated gearing system, brake, encoder or resolver, torque sensor, connection cables, and so on in a single compact housing. Normal operation causes heat generation inside this housing — mostly originating from the gearing, motor windings, and brake coil if applicable — along with other electric and electronic components. Gearing is the most significant heat source if strain-wave gearing is used — contributing up to 30% of the total power loss due to gear-mesh friction, viscous lubricant shear friction, and energy invested in repeatedly distorting the metallic flexspline every revolution. Ineffective heat dissipation will cause the robot to get hot and exhibit diminished performance.
COMMON IN ROBOT JOINTS: STRAIN WAVE GEARING A robot joint’s output shaft typically rotates at 10 to 40 rpm. A motor typically rotates at 1,000 to 4,000 rpm for short bursts during robot joint movements. So, gearing reduces speed and increases acceleration torque at the output … for high torque density relative to its dimensional footprint (torque per unit volume) and specific torque (torque per unit mass). Strain-wave gearing mechanisms offer distinct advantages that justify their use in industrial applications and robots … such as a high gear ratio in a single stage; at or near-zero backlash and simple structure; precise torque transmission; and high positioning accuracy and repeatability.
Effective Transmission of Torque High Speed Acceleration Precision with a Compact Design Advanced Lubrication Path
For More Information: info@hiwin.com Linear Guideways Ballscrews Ball Splines Harmonic Gearing System Linear Motors Single Axis Robots Torque Motors
Rotary Tables AC Servos & Drives Articulated Robots Crossed Roller Bearings Positioning Measurement Systems HIWIN Grease
Huntley, IL USA 847.827.2270
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MOTION SYSTEM APPLICATIONS Strain-wave gearing includes an ellipse-shaped wave generator, a flexspline, and a circular spline. The flexspline is the lifelimiting subcomponent. During operation, it sees constantly changing amounts of elastic deformation from the rotation of the ellipse-shaped wave generator — and must rotate with minimal angular deflection. So, the flexspline must be flexible in the radial direction but stiff in the tangential direction to accurately transmit rotational motion. Power losses in the strain-wave gearing are due to various mechanisms including: • Friction loss due to gear meshing between flexspline teeth and rigid circular spline in the three teeth meshing stages — engagement in, engagement, and engagement out. Unlike conventional gearing, teeth movement in a stain-wave mechanism is primarily sliding due to a small phase shift between the corresponding teeth in engagement. Sliding between the teeth causes energy losses and heats the assembly to an equilibrium of 60 to 70° C. • Molecular friction loss due to viscous friction in the lubricant. • Bearing friction loss in the cross-roller bearing, wave generator bearing, and other bearings. • Mechanical loss due to periodically repeated elastic strain energy, due to torsional and radial deformations of the flexspline. Some of these power losses are strongly influenced by operation temperature.
Conventional gearing systems usually exhibit some level of backlash. Backlash lowers the accuracy of gearing system but provides space for lubrication and thermal expansion. Given that strain wave gearing has nearly zero backlash, at high temperature thermal expansion on gear elements may spur interference between meshing gears — and increase tooth contact pressure and meshing friction. Wear characteristics of strain-wave gearing depend heavily on the condition of the lubricant — in turn affected by operating temperature. Excessively high temperatures may spur breakdown of the lubricant film which allows scuffing on the gear-teeth contact surfaces. The efficiency of strain-wave gearing is proportional to the load percentile (load torque to allowable average torque) and allowable operation temperature — and is inversely proportional to the input speed (gear ratio). Maximum temperature ratings are 50 to 70° C depending on the manufacturer and lubricant rating.
ELECTRICALLY ACTUATED BRAKES ARE ANOTHER HEAT SOURCE Electrically actuated brakes are common on industrial robots. Brakes in these applications typically include an electromagnetic inductive coil with a mechanical spring mechanism to engage a holding friction (interference) state upon voltage removal from the coil. Brake coils energized during motor movement generate heat. Then coil electrical resistance increases with coil resistance Rc at temperature T varying linearly with the temperature differential between the operation temperature T and ambient temperature Ta defined as: Rc,T = Rc,Ta [1 + α (T–Ta )] Where α = Material temperature coefficient (for copper magnetic wire α = 0.00393 per degree C) and Ta = Ambient temperature — with Rc,Ta = Electrical resistance of the coil at the ambient temperature So temperature rise 30° C above ambient temperature increases coil resistance 12%.
FRAMELESS-MOTOR TEMPERATURE CONSIDERATIONS Frameless motors fit applications where size and weight are top design objectives. Compared to housed motors, this motor type may offer end users commercial and technical competitive advantages — including high torque density, enhanced heat dissipation capabilities, and flexibility for customized designs. Integrating frameless (stator and rotor) motors directly onto the bearings already supporting the gearing components minimizes overall robot-joint size and eliminates redundant components. The latter might include extra bearings to support the rotor, separate shaft and coupling to between the motor shaft and gearset’s wave generator. Rated continuous-torque values listed in motor manufacturer catalogs are based on set ambient temperatures — usually 40° C. When actual ambient temperature exceeds rated values,
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Providing Value Through Technological Advancements
MOTION COMPONENTS IN ROBOTICS
motor performance deteriorates and at low speeds near stall the its output torque reduces: Tc,d = Tc
√
t max –t a,r t max –t a
Where tmax = Maximum motor winding temperature, ta = Rated ambient temperature, ta,r = Real ambient temperature, Tc = Rated continuous (low speed) torque, and Tc,d = Derated torque at real ambient temperature. So, with tmax = 80° C, ta = 40° C, and ta,r = 60° C, derated torque is 70.7% of the original continuous torque. At low speeds the frameless-motor power losses are dominated by the cooper losses in the motor windings. Power loss due to winding resistance Pl is related to current i and electrical winding resistance Rw according to the equation: Pl = ί2 Rw. As demonstrated by the Rc,T equation related to brake coils, higher temperature directly causes a higher winding resistance Rw and that in turn increases power loss in the robot joint arm. The torque derating formula doesn’t account for non-I2R motor losses such as iron losses … so as these iron losses
increase as a function of speed, the torque derating will be more pronounced than this calculation predicts. The iron losses in the motor’s core are a function of both the fundamental electrical frequency and flux density levels of the motor’s magnetic circuit. The pole count of the motor determines the fundamental frequency and the design of the stator core and permanent magnets set the flux density levels. In particular, the eddy current iron loss is a function of both the fundamental frequency squared and flux density squared. The operating speeds of the robot’s application are a key factor in the electromagnetic design of the framelessmotor as the selection of the motor pole count and design of the stator core determine the balance of I2R and iron losses. An optimized electromagnetic design results in the best motor efficiency across the robots operating speed range.
Introducing the HIWIN® Harmonic Gearing System, Datorker®
ROBOTS’ SENSOR SENSITIVITY TO HEAT Robots use many sensors — including encoders, resolvers, and torque sensors.
STRAIN-WAVE GEAR-ASSEMBLY SUBCOMPONENTS Elliptic cam on bearing
Compact and Light Weight
Ring gear
High Torque Variety of Reduction Ratios High Precision Motion Control
For More Information: info@hiwin.com Linear Guideways Ballscrews Ball Splines Harmonic Gearing System Linear Motors Single Axis Robots
Thin-walled flex gear
Torque Motors
Strain-wave gearing is indispensable in robotic applications but is not without its challenges.
Rotary Tables AC Servos & Drives Articulated Robots Crossed Roller Bearings Positioning Measurement Systems HIWIN Grease
Huntley, IL USA 847.827.2270
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MOTION SYSTEM APPLICATIONS
A key characteristic of these sensors is their sensitivity to temperature. For optical encoders, the increase in temperature causes a decrease in the LED’s light output. Thermal expansion also impacts optical encoder performance. In fact, thermal expansion can narrow the air gap between the disk and the source (detector) by 0.020 in. (0.51 mm) in some situations. Extreme instances of such thermal expansion can bring the subcomponents into contact and cause encoder damage or even catastrophic failure. For magnetic encoders, thermal expansion and contraction of the magnetic wheel can alter the pitch of the magnetic poles and thus alter the output.
SERVO DRIVE AND OTHER ELECTRONIC COMPONENTS Servo drives are key in a variety of robots including cobots, industrial articulated robots, and medical robots. But electronic component failure rates skyrocket at high temperatures. The Arrhenius law states that for every 10° C increase in operating temperature above the rated temperature, life expectancy will be halved. As one of the major sources of electric noise, thermal noise arises from the thermal fluctuations in the electron density within a conductor and thus is always present in electronic circuits. It highly depends upon the temperature — in other words, the higher the temperature, the higher the thermal noise level. The only way to reduce the thermal noise content is to reduce the temperature of operation.
BEARING LUBRICATION IN ROBOTIC JOINTS Lubrication has significant influence on the performance of both motors and strain-wave gearing. Bearing types used in robots include cross-roller bearings, wave generator bearings, and regular deepgroove ball bearings lubricated by mineral oil-base greases. Bearing friction is affected by temperature, velocity, load, lubricant properties, and operating conditions. Temperature changes cause significant grease-viscosity and molecular-friction changes. Cold can significantly reduce the oil-release characteristics of grease and lead to insufficient lubrication — with the potential for wear and failure. But high temperatures can sheer or crack the oil molecules into smaller molecules for decreased viscosity. This may induce oil leakage from the bearing. In fact, high temperatures can also trigger two other grease failure modes: Oil oxidation can lead to increased oil viscosity, deposits, and the loss of the ability to form a protective lubricant film. Or grease thickener can have a waning ability to retain the oil phase. Under extreme conditions, the latter can induce permanent loss of lubricating oil. One rule of thumb is that the rate of chemical reactions (including oxidative and thermal degradation) changes by a factor of two for every 10° C in temperature. That means increasing temperature by 10° C doubles the rate of reaction — halving expected life. Elevated temperatures drive grease failure modes quickly as they increase.
ROBOT MOTION COMPONENTS IN HARSH ENVIRONMENTS Some types of industrial robots are designed to operate in harsh environments such as spray painting robots, welding robots, and polishing and grinding robots. Such extreme conditions like wet or
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muddy terrain, dust, humidity, vibration and shock, corrosion, toxic conditions (such as radiation) and so on can significantly influence the robot’s performance and life. Industrial robots with different exterior coatings, materials, and seals differ in their ability to withstand harsh conditions. Most robots arrive at the end user already sealed. But after an extended period of service, thermal cycling may cause pressure changes and seal failures — for ingress paths and places that allow external debris to get inside the robot. Optical encoders detect rotary motion with optoelectronic components (including fine-pitch scales, LEDs, and photodetectors) that can be seriously harmed by contamination. Exposure to dust, dirt, water, or oil can cause partial or complete encoder failure over time. Optical encoders subject to significant vibration or shock can also fail if the optical disk cracks or shatters — especially those using a glass disk. Bearings are also sensitive to contamination. Dirt, dust, and other foreign objects that enter a bearing can cause scratches, pits, and lapping on the raceway surface — as well as premature damage. Moisture can degrade a bearing in several ways. Bearings exposed to moisture may corrode or become etched on its exposed surfaces for localized spots of corrosion. This pattern of corrosion in turn makes for excessive noise, unplanned clearances, and corrosion fatigue in corroded zones. All other robot parts, from electric motors to electronic components, can corrode when exposed to harsh environments. The miniaturizing design of the servo drive integrated into a robot joint has greatly reduced the space between electronic components, making them easier to integrate — but with heightened risk of exposure to corrosion. In fact, corrosion may occur during manufacturing, assembly, transport, and storage — and in field operations.
LOADING AND VIBRATION Robot payload and overall system inertia affect robot dynamic characteristics and position control accuracy. Robot payload refers to the weight a robot can lift and move beyond just its own structural mass. When a robot carries very high load, fractures may occur on the teeth of the gearing. In fact, tooth breakage is often caused by mechanical overloads that exceed the gear materials’ tensile strength. Overall system inertia is the sum of the load inertia and robot inertia. It plays a key role in rotational kinetics and represents the tendency of the loaded object and robot to resist changes in speed and direction. Higher system inertia generally makes for lower positioning control accuracy. That said, today’s latest high-bandwidth drive technology with high-resolution feedback has minimized these limitations. A robot arm in operation is subject to a variety of external loads and inertia forces depending on its position, orientation, and moving velocity. When the robot executes certain tasks — such as carrying payloads exceeding its published rating, performing fast maneuvers, and interacting large forces or moments within the unstructured Website: www.linmotusa.com environment — the robot may lose its dynamic balance and motion Phone: 262-743-2555 stability. Where a robot experiences an acceptable payload but a Email: usasales@linmot.com very high inertia, it may cause the robot to accelerate slowly, not motioncontroltips.com | designworldonline.com
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MOTION COMPONENTS IN ROBOTICS
work properly, or even render the robot incapable of making the commanded move. So safe robot operation depends on careful consideration of both the payload (inertia) and effective contact force control. A strain-wave gear may have several types of failure modes. Fatigue fracture of the flexspline is the most common failure mode. Testing on strain-wave gearing indicate that as early as four million input revolutions (for a motor running at 3,000 rpm this is equivalent to 22.2 service hours) the tooth profile was completely obliterated and damaged across the entire width of the flexspline teeth — and most of the width of the circular spline — from improper operation. What’s more, strain-wave gearing exhibits high-frequency oscillation (torque ripple) in its output torque. This mainly arises from gear-meshing vibration.
Every robot system has its own resonant frequency at which vibration occurs. For rotation-excited vibration, the resonance is known as the critical speed. End users must avoid operating robots near their inherent resonant frequencies. That's because dynamic stability is crucial to robot performance and workplace safety, especially for robots operating near humans or with large payloads, wide movement ranges, and high moving speeds. This feature was contributed by Kollmorgen Engineering Staff. For a full list of technical references, visit motioncontroltips.com and kollmorgen.com.
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MOTION SYSTEM APPLICATIONS
These are Allied Motion Technologies motors and integrated wheel assemblies for traction and steering applications in robots and automated vehicles.
Electric motors, sensors, mechanical components in
off-highway and mobile designs Automated mobile equipment, which transports items in warehouses and freight centers as well as assembly operations, continues to boost demand for power-transmission and motion control systems. In fact, the global mobile-robot market will reach $15 billion by 2026, according to researchandmarkets.com. Nearly all run off electric-motor drivetrains that are relatively expensive upfront but with high controllability, low cost of ownership due to economical electricity for power, and modest maintenance requirements. Utility task vehicles (UTVs) and all-terrain vehicles (ATVs) are a couple examples.
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Of course, many autonomous ground vehicles (AGVs) and other professional service robots (including those for logistics, remote inspection, and off-highway markets) carry subsystems to execute very specific tasks previously done manually. These require sophisticated motion controls. Geometries abound and include a wide variety of grippers, linear actuators, and multi-axis platforms and kinematic subsystems for manipulating and transporting payloads. Even for end-effecting tasks such as quickly picking items from storage racks and comingling them into shipment boxes, electric actuators are often more efficient than the pneumatics traditionally used for gripping. That’s because electric actuators draw power only when operating to let operators run (for example) electric forklifts and material-handling vehicles all day and only charge them overnight. motioncontroltips.com | designworldonline.com
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MOTION SYSTEM APPLICATIONS
Electric actuation allows tight control over position and imparts IIoT functionality. The latter is particularly useful on AGVs and other autonomous mobile designs. The traction drive shown here from Applied Motion Products includes onboard motion control and brushless servomotor, planetary gearbox, and flange to mount a drive wheel. I/O and communications network to vehicle computers and sensors without external drive (amplifier) electronics. The design’s high torque density (and low servomotors inertia) make powerful yet efficient drives for AGVs as well as autonomous mobile robots (AMRs), electric bicycles, and electric wheelchairs. Setup of motion controls is through Q Programmer software; programming includes commands for controlling motion and more.
Where mobile designs run off onboard rechargeable battery power — and in traditional off-highway vehicles that aren’t autonomous but also include automated systems and actuators — such efficiency is crucial. Direct-drive motion technologies including linear motors for end effectors (and traction motors for wheeled drives) are leading options for designs having particularly demanding requirements. Another motion profile that is typical of mobile-robot subsystems — especially for position-sensing assemblies such as light detection and ranging (LiDAR) and other tracking systems on autonomous vehicles — is that of precision rotary motion with high duty cycles. Recall that LiDAR serves to map a mobile robot’s surrounding environment to avoid other vehicles and hazards. Such motionsensing systems are core to the functionality of autonomous mobile robots (AMRs) that move items in factories and warehouses from origins to destinations often set on the fly. Complementing the frameless-motor-actuated laser-based sensing systems in these AMRs are usually PC-based motion controls that command wheel-drive servomotors while concurrently networking to facility ERP connections for IIoT functionality.
TRENDS IN BATTERY-POWERED AND MOBILE MOTION DESIGNS Allied Motion Technologies systems engineer Jeffrey Shearer confirmed some specifics about rising levels of automation in material handling. Much of this trend is the result of increasingly cost-effective material sourcing and production of robotic technologies first developed for aerospace and military applications. His company supplies subsystems for AGVs and other battery-powered equipment in this market. “We see many new motion designs for robotic systems aimed at automating material handling. In warehouse and material-handling AGVs, there’s increased demand for autonomous material-handling carts … and these often use bldc motors paired with encoders and electronics to drive their traction wheels,” said Shearer. Some designs also include Z-axis ballscrew actuators to raise and lower material-handling surfaces … and these usually require a power-off brake. Other designs such as grounds-maintenance carts for cutting grass, vehicles for solar-panel cleaning, and security cars must drive up and down steep slopes (exceeding ±30°) and run in fully autonomous mode. At their heart, these are motion designs, Shearer noted.
Nanotec compact wheel drives are for AGVs. They include a PD4-E brushless dc motor with integrated controller; magnetic single-turn absolute encoder with 1024 PPR and CAN interface; GPLEP 70 7:1 planetary gearbox; and mounting flange. With versions for right-side and leftside operation, the drive's gearboxes have reinforced ball bearings on the output side to withstand high radial and axial loads. The 100-mm wheel O.D. is PEVODYN-Soft 78° Shore A. Other motor-gearbox options and fieldbus interfaces are available.
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POWER-TRANSMISSION AND MOTION COMPONENTS IN AGVs GAM Enterprises has engineered gearboxes to fit in AGV wheel hubs and satisfy challenging design requirements — include the need for the wheel hub to support the vehicle’s weight. “We’ve also catered to these growth industries by providing dc-power drives to accompany our motors,” said Peter Zafiro of LinMot USA. “Vehicle designers can just use their own chosen incoming power — even battery power … or use power coming off rails. Then off that incoming power, a dc bus power supply in the vehicle design can run our motors. This setup — small dc drives distributed throughout the vehicle — is much better than having a large (and heavy) threephase inverter.” Of course, the motors in autonomous material-handling equipment must be reliable. According to Sensata Technologies V.P. of industrial solutions Matt Lesniak, Sensata BEI Kimco frameless brushless dc motors satisfy that requirement and fit quite well into the tight footprints of robotic joints.
After all, too much power in robotic designs is unnecessary and detrimental; each motor should only deliver the power that’s needed for its specific axis. Zafiro confirms that many of today’s designs achieve that with brushless dc motors … getting higher resolution at lower forces because there isn’t a large motor power factor. Such designs require more up-front application work, but that extra effort pays off big down the line, said Zafiro. “AGVs for automotive assembly use our bldc transaxles on their traction wheels,” said Shearer. “AGVs for aircraft assembly also use our bldc parallel-shaft gearmotors for their traction wheels … and some flatbed pallet-carrying AGVs could soon use our bldc motor wheels.” He cited other specific examples. In rail-guided high-density storage installations (also called AS/RS installations) that often work alongside mobile robotics, his company’s bldc gearmotors work on their traction wheels and surrounding conveyors. Though they aren’t autonomous mobile robots, increasingly heavy ATVs and UTVs as well as end-user demand
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MOTION SYSTEM APPLICATIONS Wheel angle limit switch Steering gear
Wheel angle sensor
Steering motor
Traction motor for more luxurious riding experiences have spurred an uptick in electric power steering (EPS) and even steer-by-wire designs where the traditional steering linkage is omitted from these electric vehicles. New forms of electric-motor actuation on construction, off-highway, and military equipment also abound. Some equipment for planting and harvesting now sports automated modules, so farmers no longer need to drive these vehicles. Where the efficiency gains and weight reductions justify the investment, many hydraulic applications are being replaced by electric on these vehicles as well. Brushless motors in mobile robotics example 1: Allied Motion Technologies recently supplied a bldc gearmotor to replace a hydraulic actuator for opening and closing an armored door on a troop transport vehicle. Brushless motors in mobile robotics example 2: The motor maker supplied an aftermarket bldc motor — with a controller — to couple to a steering wheel and autonomously drive farm equipment.
Brushless motors in mobile robotics example 3: One machine builder that makes a grape harvester is exploring the possibility of replacing their design’s hydraulic motors with electric onboard. The main reason here is that hydraulic motors and hoses can leak and contaminate food product. Brushless motors in mobile robotics example 4: One new electric riding lawn mower uses the manufacturer’s electric motors for its wheel and blade drives. Mass customization is also pretty typical of the motion components and subsystems that go into autonomous designs. Often a top objective is to reduce the design’s total part count. According to Shearer of Allied Motion Technologies, some LiDAR systems employ his company’s dual bldc MegaFlux motors paired with high speed encoders — in a completely custom design. “Another example of a totally custom motion solution is the seat actuator for a military vehicle. Our full system solution combines a brushless motor, drive electronics, a parallel-shaft gearbox, and a ballscrew,” he noted.
This integrated traction-wheel assembly with steering from Allied Motion Technologies includes a right-angle permanent-magnet gearmotor. The gearmotor turns a pinion that rotates the wheel about its centerline. The small white pinion and blue sensor (circled in red) send feedback on wheel position to a vehicle controller.
In cases like these, the manufacturer has had a lot of success modifying standard products with custom motor windings, electronics, and gearboxes to fit specific applications. “Small to medium-size companies are entering the realm of robotics — creating innovative technologies for medical, consumer, and industrial industries,” said Tomer Goldenberg of Elmo Motion Control. These smaller companies (unlike large robot manufacturers) don’t have specific sensing or feedback divisions, motion or servo divisions, or control divisions. “These smaller robot makers rely on motion technology manufacturers to provide them with products and tools to simplify implementation of motion system designs … and reduce time to market,” said Goldenberg. “So turning to servo manufacturers that can provide full solutions one technology is highly advantageous for small robotic manufacturers,” concluded Goldenberg.
Battery-powered mobile equipment employs motion components such as those from the Electric Clutches and Brakes Group of Altra Industrial Motion. This manufacturer’s AGV ERS Brake for static holding with limited e-stop braking is for OEMs wanting to incorporate brakes and clutches to eliminate manual processes and maximize mechanical control of automated tasks.
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MOTION SYSTEM APPLICATIONS
Frameless motors from Kollmorgen let robot builders make designs smaller and more precise. The motors work in robotic arms and joints, collaborative robots, and AGVs for picking and sorting as well as self-driving forklifts. The frameless motors integrate seamlessly with strain-wave gears, feedback devices, and servo drives to deliver lightweight and torque-dense motion solutions.
“We are also seeing lab-automation companies, consumerproduct companies, and even startups develop moveable collaborating robots; these are reasonably smaller than the offerings of typical robot companies,” agreed Jonas Proeger of Trinamic Motion Control. “Most of these designs focus on helping humans with repetitive or heavy-lifting jobs … and all aim to have teachable functions so the robots don’t need to be programmed — and anyone who can do a job can also teach the robot to do it or assist in that job,” said Proeger.
POWER-TRANSMISSION DESIGNS ALSO TAILORED TO AGVS The varied designs of AGVs and mobile robots also necessitate specialized drivetrains. That’s according to president of GAM Enterprises Craig Van den Avont. His company has supplied custom reinforced gearbox subassemblies that are capable of high load bearing (to support the weight of an AGV) even while fitting into compact vehicle wheel hubs. Here’s one of the challenges: The way in which vehicle weight rests on the wheel drive shaft makes for significant radial loading on the assembly’s bearings. Standard groove ball bearings installed in close proximity don’t fit the bill. That’s because wheel loads on nonspecialized assemblies cause output-shaft and gear deflection, which in turn accelerates wear. Pretensioned tapered-roller bearing pairs do resolve hefty radial loads but are relatively heavy and degrade efficiency — unacceptable tradeoffs for designs running off battery power. Another solution to this problem from German
gear manufacturer Framo Morat is a narrow wheel-hub gear design using standard ball bearings to absorb vehicles’ radial loading on the wheel assembly. Within its gearbox, a motor-input shaft and hollow drive-output shaft are concentric … so radial forces through the hollow shaft are centered between twin ball-bearing supports. Tight clearance between these bearings maximizes the output shaft’s bending stiffness. Of course, not all mobile designs have a four-wheels-and-acar morphology. Robot and AI supplier Autonomous Solutions Inc. (ASI) continues to offer their Chaos “high mobility” robot. It has four continuous tracks that are free to swing like arms — as if the tracks on a tank were cut loose from the tank body at an idler-pulley end. Here, eight Parker Bayside frameless torque motors drive these freemoving tracks to make them paddle over rocks, logs, and aquatic obstructions. Speeds are to 6.5 mph and continuous load capacity is to100 lb (or 275 lb with slightly limited capabilities) for real-world applicability in surveillance, mine exploration, explosive ordnance disposal (EOD), and other dangerous missions. GAM Enterprises has also supplied subsystems for these
This mobility-robot wheel drive achieves a compact design and high efficiency with a brushless dc motor from Dunkermotoren and a specialty gear assembly from German gear manufacturer Framo Morat.
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MOTION SYSTEM APPLICATIONS
Though not mobile (so beyond this feature’s focus) large-scale Cartesian arrangements in automated storage and retrieval (AS/RS) systems often complement mobile robotics in automated-warehousing installations. | courtesy Dunkermotoren kinds of automated designs. In such rough outdoor terrains, the way in which vehicle wheels traverse rocks, curbs, and mud necessitates specialized power-transmission subassemblies capable of withstanding significant shock loading. But even in more controlled indoor environments, ruggedized wheel drives are helpful. “We currently see rapid rise in technologies bound for automated-warehouse applications, especially those destined for automated transport vehicles,” said Proeger. “These are occasionally on rails, but many designs run independently and on Mecanum wheels. None of these are projects we may name, though we know such designs are employed by industry leaders.” Omni-directional Mecanum wheels were invented in the 1970s and through the 1990s were primarily used by the U.S. Navy. The wheels are quite useful on transport vehicles such as AGVs, as they allow motion in any direction without a turning circle. That makes for nimble moves in confined intralogistics installations as well as settings where mobile robots must navigate around lots of conveyors. Like omni wheels (a fairly similar design) Mecanum wheels are now manufactured and employed by a wide range of OEMs and organizations, including FIRST Robotics teams on educational-grade
robotic vehicles and those building far more sophisticated industrial designs as well. In fact, another design challenge for the wheel drives of AGVs and similar designs is that axially installed electric motors with multi-stage spur or planetary gears (common in conventional wheel and belt drives) are often too large. So to address this problem, one customizable and compact wheel drive includes a brushless dc motor from Dunkermotoren and specialty gearing from Framo Morat mentioned earlier. The planetary gearing complements electronically commutated (brushless) dc motors from the BG series of Dunkermotoren; a bevel gearbox connects motor to hub gears’ input shaft for a very power-dense wheel drive. Motor efficiency of better than 90% and lightweight low-loss gearing maximize efficiency. The Dunkermotoren motors run off 10 to 60 Vdc; versions accepting 24 V can output 1,100 W and 2,600 W intermittently. Built-in speed control and positioning electronics are also available. Optional safe torque off (STO) functionality via software on its motor control can protect nearby personnel and machinery where needed. Other motor suppliers supply complete wheel assemblies to the AGV market as well. Design World has covered the Wittenstein iTAS in the past; this modular servo-driven wheel axis has twin servomotors and helical planetary gearheads that accommodate Vulkollan wheels — not unsimilar to the Vulkollan wheels on the Framo Morat and Dunkermotoren offering. The iTAS motors allow wide tilting moments and have high power density to serve on AGVs that move especially heavy trolleys around.
This is a customized drive unit from Nabtesco Corp. with a Mecanum wheel. Nabtesco offers compact RF-P series solid-shaft cycloidal gears for Delta and SCARA robots as well as AGV wheel drives. The two-stage RF-P series gears allow output speeds to 200 rpm and exhibit hysteresis loss of less than 2 arc-min.
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MOTION SYSTEM APPLICATIONS
Actuator applications Electric actuators are integrated motion designs that include an electric motor and rotary-to-linear device for repeatable motion to given positions. Many linear actuators deliver multiple outputs with programmable controls that adapt to changing conditions. Applications with similar dynamics often make use of the same actuator types — those that pair motors with ballscrews or leadscrews; incorporate brushless dc motors and belt-and-pulley setups; take a rodstyle morphology; use motors with planetary roller screws; or integrate built-in guides. Consider four representative application examples from PBC Linear for leadscrewbased actuators.
Bimba now sells fully electric IntelliPress benchtop presses to expand the possibilities of factory automation. This press complements Bimba’s existing hydraulic and pneumatic press families by offering the benefits of electric motion (including energy savings, dynamic force and speed control, an infinitely variable stroke, reduction in oil and associated hydraulic mess) at an affordable price. The IntelliPress delivers force ranges to 3,000, 6,000, or 12,000 lb … and comes in configurations with varying degrees of electronic control integration for off-the-shelf operation and configurability.
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Case study — High-precision Z axis: A manufacturer of a highly precise SLA style 3D printer needed to hold layer resolutions to an exacting level of 10 µm. The mechanical accuracy of the constant-force anti-backlash nut and leadscrew coupled with the high performance of a smart step-servo motor made for a system well within the specification at lower overall system cost — as this assembly needed no linear encoder for feedback from the point of interest.
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Case study — X-Y contouring and dispensing: A fused deposition modeling (FDM) 3D printer tends to produce a part that shows ridges or the beads from each layer as it is placed on the printed part. Working with an FDM machine builder and using the consistent performance of the constant-force anti-backlash nut features, engineers were able to decrease the surface finish and layer resolution of prints while using the control commutation capabilities of a smart step-servo motor to improve performance resulting in twice the process output of a typical FDM printer. Case study — Medical syringe pump: A leading manufacturer of syringe pumps for medical applications needed the highest levels of fluidic control with minimal flow variance over time. This was critical to their lifesaving equipment. Specific life tests were conducted with a constant-force zero-backlash nut and screws operating side-by-side with competitive screwand-nut assemblies using a conventional coil spring and collet. In the end, all the conventional designs failed to complete the test due to loss of preload, but the final results showed the leadscrew assembly with the constant-force nut to be 200% better for fluidic accuracy over the full 1.5 million cycles targeted. Case study — Metals additivemanufacturing platform: Ballscrews are proven to be the product of choice for
motioncontroltips.com | designworldonline.com
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ELECTRIC ACTUATORS
Tolomatic’s RSX096P electric linear actuator increases the force range of the RSX product family to 40,000 lbf. Optimized for force in the extend direction, the RSX press-model electric actuator excels in metal-forming and assembly — including pressing, punching, stamping, riveting, fastening, and joining.
heavy load and high duty-cycle applications, and ground ballscrews offer extremely high precision. Even so, there are a growing range of applications for which the choice between rolled ballscrews and leadscrews isn’t as clear. One leader in metal additivemanufacturing machines tested leadscrew and motor assemblies head-to-head with a
similar rolled ballscrew unit. A leadscrew assembly with superior thread rolling, a polymer nut, and a motor optimized for linear performance exhibited less backlash and higher accuracy than a comparable ballscrewbased actuator. What’s more, the polymer nut’s self-lubricating nature eliminated the need for added lubricants … making the machine process cleaner and safe from printed-part contamination. Secondly, metalto-metal contact was eliminated between the nut and screw. This reduced noise for much quieter operation. In the end, the integrated leadscrew delivered superior cost advantages and print quality.
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MOTION SYSTEM APPLICATIONS
Belts and chains in
vertical arrangements BEMA Series synchronized XYZ gantries from IntelLIDrives use motorized belt mechanisms on their axes to deliver speeds to 2 m/sec — making the gantries suitable for high-speed positioning of medium payloads. Load capacity in X-Y is 30 kg; on the vertical axis it is 2 kg.
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So what options are suitable? Actuation based on motor-driven ballscrews and leadscrews works in many arrangements, though it’s not the leading choice for particularly tall installations. Here, trouble with backdriving, buckling, or keeping lubrication evenly distributed over the full stroke may indicate other motion technologies. Belt drives and chain drives are suited to the varied forces of working with and then against gravity — even while resolving other loads.
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Vertical applications employing belt drives often include actuator assemblies complete with twin linear-bearing blocks and guide rails. Such bearings primarily address moment loading during deceleration and acceleration. Safety mechanisms can help keep the machine axis under control, even in the unlikely event of catastrophic actuator failure. For example, Macron Dynamics offers a timing-belt accessory system called the cam-lock arresting wedge system (CLAWS).
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BELTS & CHAINS
This mechanical design has a shuttle that can slide forward up an incline ... and that incline sets itself into any part of a vertical travel to lock and hold the carriage or payload when required.
CABLES AND CHAINS IN ELEVATORS AND HOISTS More common for hoists and elevators is steel-cable actuation employing direct-drive motors with integrated output-shaft sheaves. Such solutions can reach thousands of feet — and execute such strokes in less than a minute in some instances. Where elevators must bear heavy loads, worm gearsets on the motor are common to magnify torque capacity. But no matter the motor or gear arrangement, VFDs have become industry standard for motor driving capable of dynamic braking and regenerative operation. These and ultra-efficient clutches and brakes maximize the safety and efficiency of cable-actuated vertical designs. Another mechanical option to boost efficiency and safety is vertical lifts based on rigid-chain actuation. That’s because resolution of lifting and side loading in complete actuation systems make for more efficient operation. International standards tend to dictate requirements for these designs.
Consider such chain to automate orchestral platforms and theater scenery in shows with high production value: Such rigidchain actuators might raise and lower seating to accommodate various audiences — or platforms and substages during a live show. Carried loads can reach many tons. Such rigid chain includes links (having a square cross section) that coil in a housing and mate when extended to lock into rigid structural columns. This geometry addresses the loads mentioned earlier with optimally positioned center of gravity. All such rigid-chain systems include feedback devices that sense obstructions and switches that communicate data back to controls. Safety gates underneath actuated stages provide further protection … and operator control pendants can trigger immediate halts to the vertical lifts. Another safety function of rigid chain is avoidance of contamination by hydraulic fluid.
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MOTION SYSTEM APPLICATIONS
Brakes and clutches in
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Brakes, clutches and torque limiters work in medical equipment, packaging machinery, industrial hoists, and installations. Recall that brakes stop and hold loads. Clutches and torque limiters disengage and engage power-transmission outputs to transfer torque from an input. Torque limiters modulate power transmission to protect mechanical equipment from overload.
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When selecting clutches, brakes, and torque limiters for an application, options include mechanical, electric, fluidic or self-actuation. Electric brakes are easy to control and cycle, even to a couple thousand cycles per minute. In contrast, common air-actuated brakes and clutches run coolly and maintain hold with minimal power. Friction brakes with disc, drum and cone morphologies work well as emergency brakes because of their failsafe holding — essential on conveyors, escalators, airport-baggage handlers, elevators and other safety-critical designs. The size and type of brake most suitable for a given design depend on whether the machine needs emergency stops or softer stops that sacrifice brakes to protect loads from shock. Then, other application criteria (including the machine envelope, thermal capacity, cycle rates, and inspection and repair schedules) dictate the final selection. In other machines, it’s more important that brakes prevent shifting loads and misalignment. In most cases, it’s best to size brakes and clutches to the motor torque of the machine axis. But especially for axes where the brake must stop a vertical load, engineers should account for the fact that motors can temporarily draw added current to output
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BXW spring-applied brakes from Miki Pulley excel in large SCARA applications.
more than their rated torque. Helpful resources include published performance curves from brake and clutch manufacturers. These list dynamic torque ratings for various operating speeds to help engineers match brakes and clutches to peak motor-output torque. 11 • 2019
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BRAKES & CLUTCHES
Beyond these general guidelines, fast, hot and other extreme applications require extra evaluation. Some tips: Spring-set brakes benefit motion designs that slow loads with the motor before the brake engages; they’re also suitable as holding mechanisms. Machinery that runs beyond a few hundred cycles per minute may require brakes and clutches that are larger than performance curves indicate. Industrial designs that operate in hot environments may benefit from friction brakes with specialty frictionsurface geometries and materials (such as phenolic resin or ceramic). Motion applications that don’t get a lot of maintenance also benefit from the longer life these friction materials get. Brakes that use permanent magnets for operation automatically adjust for wear. Consider one technology for high-cycle robotic applications. BXW spring-applied brakes from Miki Pulley for larger robotic arm applications can brake heavy loads as well as hold them in position. These functions let the brakes work even during power failures — to protect the robot from system collisions and mechanical system collapse that can cause costly equipment damage and manufacturing downtime. An optional release lever lets operators release the brake from a hold position when restarting the servo motor and the robot’s operation. The friction brakes handle speeds to 5,000 rpm and torques to 5.2 Nm with compression springs that engage and capture the brake rotor hub to immediately stop arm movement. A heavy-duty design reduces idling wear in articulating joints; rmature engagement is smooth, quiet, and sans chatter.
TOO MUCH ON YOUR PLATE?
Don’t eat up valuable time searching for friction brakes, clutches and torque limiters. For more than 45 years, machine designers have relied on us for made-to-order products that meet their exact requirements. We are easy to reach, quick to respond, and deliver both catalog and custom products within reliable lead times. › Pneumatic and mechanical models › Torque capacities to 60,000 lb.in. › Experienced application assistance One call or email connects you with an engineer: USA 859-291-0849 engineering@machiii.com
BRAKES • CLUTCHES • TORQUE LIMITERS DESIGN WORLD — MOTION
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Improved range, performance, and usability are helping modern eBikes enjoy growing popularity as commuter, commercial, and recreational vehicles.
Next-generation eBikes use
BLDC motors and advanced controls
Since their emergence in the early 1990s, eBikes have undergone a steady series of improvements in range, reliability, and performance that have won them a growing number of loyal users worldwide. Yet despite nearly 30 years of technical evolution, there’s still room for innovation. Some innovations in next-generation eBikes relate to better frame designs and mechanical systems. Others include advances in electronics for the motor drive and energy-storage systems. But the most dramatic changes are in eBike controls and user interfaces for maximally enjoyable user experience (UX). Most modern eBikes use permanent magnet motor (PMM) propulsion, with brushless dc motors being especially common. BLDC motors are one of the simplest forms of synchronous motor: These have a permanent-magnet rotor assembly surrounded by a wound stator having several (usually three) winding sets. BLDCs are lighter and more efficient that equivalent brushed motors — plus need little maintenance. The catch is they need a motor controller to provide a drive waveform (commutation). The controller does this by monitoring the rotor position and supplying power to the stator windings in the correct sequence to start and maintain rotor motion. BLDC motor drive technology for eBikes is relatively mature but there are still a few places where designers can differentiate products through lower cost or better performance and efficiency. For example, a growing number of eBike designers are using motor controllers capable of supporting vector control-based commutation — also known a field-oriented control (FOC). The FOC algorithm can decouple control of torque and flux by transforming the stator current values (phase currents) from a stationary reference frame to a rotating reference frame.
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This speed and torque-sensing crank shaft, manufactured by THUN-X, provides two digital outputs for the digital sin/cos speed signal and an analog output for the torque signal. With this arrangement, the eBike’s motor controller requires only two digital inputs and one analog input. | courtesy Enviado
motioncontroltips.com | designworldonline.com
11/19/19 11:05 AM
CONTROLLERS An FOC motor controller requires a processor powerful enough to support this compute-intensive algorithm as well as some means of accurately sensing rotor position — typically an analog or digital Hall-effect sensor or optical interrupter. In return, FOC helps the motor deliver excellent performance, a wide speed range, high operating efficiency, and high torque and low current at startup — characteristics that in turn boost eBikes’ drivability and range. Because the sensors that determine rotor position can add cost and complexity to a design, eBike designs sometimes employ controllers that support sensorless operation. In this mode, current readings and the back EMF generated by the motor’s windings can be used to estimate position and speed of the motor. Unfortunately, while this is a relatively easy task above a certain velocity, it is much more difficult at standstill and low velocities which occur every time the rider stops or starts. Although this is acceptable for some appliances and other applications, so-called sensorless FOC controllers for eBikes remain in the development stage.
Regenerative braking is another promising feature for some types of eBikes. Here, field windings of the eBike’s drive motor serve as a generator/brake to recover some of the bicycle’s kinetic energy as electrical power to charge the battery. The algorithms needed to support regenerative braking are relatively straightforward, but this function is only practical to implement in direct-drive systems where the motor is directly coupled to the wheel. Unfortunately, many eBike motors include a planetary gear drive (often coupled with a freewheel function) making regenerative operation impossible.
NATURAL CYCLING FEEL “Creating natural-feeling response to rider pedaling is a multi-faceted design challenge,” says Trinamic team leader software Development Enrico Dressler. He says the controllers of nearly all early eBikes and pedelecs used a pedal speed sensor (typically Hall effect sensors and a disc with magnets) as their primary input. As the rider pedaled faster, a controller algorithm increased support provided as inceased power to the motor. This simple control scheme was reliable and easy to implement but had several unpleasant drawbacks. The controller only functioned when the pedals turned, so could not assist the user from a dead stop — precisely when it’s needed most. In addition, controllers that provided assist based solely on pedal speed gave riders an odd sensation. Processing delays and the nature of the algorithms themselves caused small but noticeable delay between the rider’s inputs and the bike’s response — so it felt as if the pedals were connected to the rear wheel via a large rubber band. Pedal speed sensing also raised potential marketing issues in some countries with strict definitions on how
This module, based on Trinamic’s TMC4671 motor controller IC, works in BLDC-based eBike drive systems. Its integrated MCU can be programmed to deliver custom speeds and responses to pedaling. | courtesy Trinamic Motion Control
mopeds, motorcycles, and other twowheeled vehicles are taxed and licensed. Because a pedal-assisted eBike could, theoretically, provide assist even if there was no chain between the pedals and the rear wheel, it can be technically defined as an electric moped according to some countries’ laws ... thereby needing it to be licensed, regulated, and taxed accordingly. So eBike motor controllers have evolved to make power-assisted riding more natural and enjoyable. In an suitable world using a pedal-assisted eBike should feel just like cycling on superpowers. Of course, the motor controller must be able to sense the torque being applied at the pedals and use it as the primary means of determining how much assist to deliver ... Read the rest of this feature — including more on eBike user interfaces, electric cargo bikes, and hybrid wheelchairs — by visting motioncontroltips.com and serching Trinamic eBike.
LeichtLast is an experimental e-cargo eBike, developed by Trinamic as a testbed for a new generation of e-cargo bikes. Thanks to its high-efficiency drive control system, regenerative braking, and other new capabilities these vehicles are expected to become a highly practical alternative to fossil-fueled delivery vehicles in cities and | courtesy TRINAMIC Motion Control some suburban settings.
motioncontroltips.com | designworldonline.com
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DESIGN WORLD — MOTION
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MOTION SYSTEM APPLICATIONS
| courtesy Sidel
Conveyors in
warehouse automation
Conveyor functions are as varied as the applications they complete. Conveyors for discrete product transport benefit from customization to satisfy requirements — including chain and belt size, morphology and material; support frames; controller, drive, and motor or motors; mode of engagement with the drive; encoder, vision, and switch feedback; tracks, bumpers, and gates; and HMIs and plantlevel IT integration. Consider warehouse automation where the objective is ultra-fast sorting and tracking. Such applications need conveyors with servomotor functionality integrated with inspection stations fitted with machine
| courtesy Sidel
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vision. Or consider pharmaceutical manufacturing — now a trilliondollar industry, even while standards such as FDA CGMP regulations are more stringent than ever. Here, conveyors must deliver top-notch warehouse automation functions and have stainless and aluminum parts to pose no risk of contamination to expensive pharmaceutical products such as pills. Likewise, medical-device manufacture must adhere to FDA regulations that dictate equipment-sterilization schedules so conveyors in these applications withstand harsh washdowns.
WHITE VINEGAR LINES EMPLOY DRY LUBRICATION AND OTHER CONVEYORS Rising demand for white vinegar recently prompted French condiment and seasoning company Charbonneaux-Brabant to install a Sidel PET line in their new Vauvert production plant. There the company bottles white vinegar in 1 and 1.5-l formats in a flexible operation that continuously changes to satisfy supply chain and distribution demands. In fact, growing use of white vinegar as a natural and effective cleaning product spurred the expansion. As with other natural cleaning products such as baking soda and rubbing alcohol, white vinegar is also an affordable choice. Charbonneaux-Brabant three existing plants couldn’t keep pace with demand for product sold under the Charbonneaux-Brabant name as well as supermarket and private labels. “All of those sites were nearly saturated and incapable of coping with the growing demand for white vinegar without a potential risk of production shortages,” says industrial director Loïc Dionis. The main challenge in outfitting the new facility was maintaining the stringent packaging conditions required for edible product while leveraging PET packaging processes similar to those for edible oils, sauces, and dressings — all while ensuring the equipment could withstand the high acidity of white vinegar sold as a homecare product. “Charbonneaux-Brabant wanted to employ inline PET bottle blowing and turnkey solutions for a fully automatic high-speed line for the production of vinegar,” says Sidel key account manager Loïc Leon. motioncontroltips.com | designworldonline.com
11/19/19 11:09 AM
Improve Quality and Output by streamlining applications with pallet-handling conveyor systems
www.mkversamove.com OUR CUSTOMIZABLE PRODUCTS
105-125 Highland Park Drive, Bloomfield, CT 06002 860.769.5500 | info@mknorthamerica.com
mkNorthAmerica 8-19.indd 35
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MOTION SYSTEM APPLICATIONS
| courtesy Sidel
Besides the variations in bottle sizes and labels, the product is grouped into packs of six, nine, or 12 — either in complete wrap-around blanks or in shrink-wrapped film. Product also ships in 10 different palletizing configurations with four pallet patterns. The system Sidel supplied includes a complete PET line capable of running at 23,000 bottles per hour with 90% efficiency. A Sidel Matrix Combi blow molding + filling + capping machine has a compact footprint. A cold-glue labeler quickly processes labeling. Twin overwrapping machines include a continuous packer (for wrapping of blanks at 37.5 cases per minute) and a shrink wrapper to bundle bottles in packs. A layerby-layer palletizer at the end of the line employs an infeed system with electronic spacing to prevent damage. But at the heart of the installation are conveyors. A system of conveyor sections (including inclines) feeds the plastic tubes called parisons up into the blow-molding machine for bottle forming. A superhighway takes formed, filled, and capped bottles off the Matrix Combi and sends them down a narrowing funnel for accumulation before an inline labeling station. Another conveying section at a wrap-around station transports groups of bottles into a stream of cardboard as it’s folded into boxes around the bottles. A trio of conveyors at the end of the line allow the assembly of finished boxes of product with wooden skids (from another steel-roller conveyor) with cardboard sheets (supplied from above by a gantried pneumatic-gripper frame) and onward. Twin conveyors feed these completed skids into the wrappers.
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| courtesy Sidel
motioncontroltips.com | designworldonline.com
11/19/19 11:09 AM
| AT11-14USA |
A revolution in linear transport systems: XTS NEXTSTEP The XTS advantage circulatory movement flexible modular system individually movable movers
User benefits reduced machine footprint software-based changeovers improved machine flexibility increased throughput shorter time to market
www.beckhoff.us/xts Manufacturers around the world need to offer increasingly customized products – with machines that deliver reduced footprint and improved productivity. Available now in the U.S., the eXtended Transport System (XTS) from Beckhoff answers these machine design challenges and more. In combination with PC- and EtherCAT-based control technology, the XTS features a high level of design freedom for machine builders to develop game-changing concepts for product transport, handling and assembly. A stainless steel hygienic XTS version is ideal for use in the pharmaceutical and food industries. Take your next step in machine design with XTS: total freedom of installation position compact design integrates directly into machinery freely selectable track geometries few mechanical parts and system components
Beckhoff Automation 11-19.indd 37
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Bright coupling uses RBI Solar, a designer and manufacturer of solar-panel mounting for commercial applications, needed a reliable coupling for its new single-axis tracker. The Sunflower mount rotates rows of photovoltaic modules on the east-west axis to follow the sun and maximize energy production. In large-scale commercial installations, rows can be 400 ft long consisting of a dozen or so 35-ft sections. Breaking up the long rows into smaller sections lets the new system accommodate various topographic conditions. The couplings connect the drive motor to the drivetrain at the end of each row of photovoltaic modules.
RBI Solar Sunflower mounts rotate photovoltaic modules to follow the sun. The motion designs to spur this action employ precision couplings.
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During the tracking-system development, RBI Solar engineers determined that an L-Jaw coupling was the most economical choice that met the system requirements. They began searching for a coupling source offering the right coupling type and quality level — and convenient face-to-face support. Ultimately, they decided to work with TB Wood’s of Altra Industrial Motion. To meet the application specifications and torque requirements, the RBI Solar used modified TB Wood’s LO95 L-Jaw couplings with a Hytrel spider element and torque capacity of 401 lb-in. The couplings feature standard sintered steel hubs. TB Wood’s worked closely with RBI to revise the standard L-Jaw coupling bore design to accommodate the unique shaft geometry and provide a secure hub-to-shaft connection. Beyond superior coupling quality and performance, the interactions TB Wood’s had with RBI Solar provided added value. RBI was able to rely on the TB Wood’s team for engineering expertise and timely delivery.
11 • 2019
motioncontroltips.com | designworldonline.com
11/19/19 8:17 AM
CONTROLFLEX COUPLINGS WHAT IS A CONTROLFLEX COUPLING?
WHY RULAND?
• Lightweight, low inertia, and balanced design for speeds up to 25,000 RPM.
• Widest variety of standard Controlflex sizes in the world – over 550 hubs that make over 11,000 combinations.
• Ideal for encoders or other light duty applications. • Single insert style for fit in compact spaces and high misalignment. • Double insert style for added torque. • Consistent zero-backlash operation. • Manufactured by Schmidt-Kupplung in Wolfenbüttel, Germany.
• Large stock on hand in our Marlborough, MA USA factory. • In-house rebore allows for quick turnaround on out of stock items. • Easy to navigate website with full product data, CAD, and install videos.
Want to try Controlflex for yourself? Go to ruland.com/samples and we will send you up to 4 couplings to test in your next design.
Ruland Manufacturing Co., Inc. 11-19.indd 39
CONTROLFLEX COUPLINGS
New
www.ruland.com 11/15/19 3:47 PM
Your Design, Your Way, F Fast! Standard Shafting Next Day*
Custom
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*Cut to length shafting orders up to 20 pieces received by 1pm EST **Special machined orders up to 25 pieces that do not require outside processing
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Lee Linear 11-19.indd 40
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COUPLINGS
RBI Solar engineers used modified TB Wood’s LO95 L-Jaw couplings with a Hytrel spider element for their design.
coupling type though: Never use rigid couplings to replace flexible servocouplings on axes where the latter seem to fail frequently. Here, this issue is most likely insufficient alignment between the motor-output shaft and next component in the powertrain. There’s sometimes a misconception that rigid couplings are exceptionally strong, so can address issues in such situations. The fact is that rigid couplings only work when shafts are perfectly aligned, because these couplings transmit to connected motion components (potentially extreme) forces that arise from misalignment.
2 COUPLING SERVO-APPLICATION CONSIDERATIONS Couplings for servo applications usually connect precision drives to sensitive loads, so they can’t induce any error. That’s why servocouplings should be zero backlash — to prevent issues with timing and predictability (not to mention failures due to hammering on reversing axes). Couplings for servo applications must also have high torsional stiffness while imparting slight forgiveness of misalignment (within specifications) of rotating shafts … even while holding transmitted rpm steady to motor output rpm.
Sizing for torque (and speed): After specifying the coupling type, the design engineer must select a coupling size. This is heavily dependent on axis rpm, the levels of torque the axis must transmit, and the service factor the application requires. Axes that transmit steady torque are simpler to specify; in contrast, axes that transmit variable torque need additional consideration. Here, define the application’s average operating torque and the peak torque. Also consider the parameters listed in Ability to handle reversals. One tip to avoid servocoupling oversizing: Quantify actual system
But these are just a couple servocoupling considerations. Consider a typical application for servocouplings — to connect a servomotor to a ballscrew. Here, couplings with low inertia let the axis deliver faster acceleration and deceleration without unnecessarily degrading overall system efficiency. In fact, couplings for servo designs must often compensate for subtle power-transmission issues to minimize errors down to 1 arcmin. or lower. That’s especially true where servo systems take the form of exacting positioning axes. Here’s a more complete list of parameters to consider for proper coupling operation in such designs:
1
Coupling type: Couplings shouldn’t be the last motion component specified because proper servo-machine function relies on having a suitable coupling in place. Torsionally rigid options (suitable for motion designs) include specialty bellows couplings, rubber-jaw couplings, and disc couplings. Curved-jaw couplings have good damping characteristics to optimize performance of axes with quick acceleration and deceleration. Elsewhere, both disc-type couplings and certain bellows couplings excel on high-speed axes. Other offerings abound to serve other design objectives. One caveat on 11 • 2019
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DESIGN WORLD — MOTION
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MOTION SYSTEM APPLICATIONS
THE COUPLING.
ST
FOR RELIABLE OVERLOAD PROTECTION
INDUSTRIAL SAFETY COUPLINGS
requirements and base coupling selection on those values — and avoid defining a whole axis by the connected gearmotor’s peak torque output.
3
Stiffness: Along with exacting control of position, force, or output velocity, it’s often essential to maintain high efficiency. Couplings that exhibit windup or backlash degrade this efficiency because they must overcome load inertia every move cycle. This can be a significant drawback in some setups ... which is why (especially on axes employing rigid couplings) couplings should be prevented from inadvertently functioning as flywheels. Note that if a coupling’s torsional stiffness is insufficient, other system functions must compensate. One standard solution is to adjust PID controls and reduce servo gain, though that degrades system response and performance. In contrast, excessive torsional stiffness compromises the ability of an axis to withstand quickly reversing loads. That’s because servocouplings with excessive stiffness can be brittle and prone to failure on demanding axes that must make frequent and sudden directional reversals. Servo-application tip: Balance coupling characteristics for stiffness. Excessive torsional stiffness may induce premature failure. On the other hand, axes that must hold timing (as for positioning commands) benefit from incorporation of torsionally stiff couplings.
4 5
Inertia: As mentioned, this is an important parameter for a few reasons. Applications with particularly aggressive motion profiles rely on low servocoupling inertia most of all. Damping capabilities: Disc couplings, certain bellows couplings, and high-gain rubber-type couplings are all options for coupling-based damping in servo applications. In fact, the most demanding servo applications have in recent years spurred improved response frequencies
RW-AMERICA.COM
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COUPLINGS SERVOFLEX SFS-G
Shown here are Servoflex couplings from Miki Pulley on a printing machine with stringent line-shaft specifications.
... but vibration (and hunting) arise with high gain settings on assemblies using torsionally stiff couplings. Visit couplingtips.com and search on “damping” for more on this issue and some solutions.
6
Shaft connections: Most servocouplings connect shafts with clamping or locking mechanisms (and not keyways). Though keyways are often offered as an option to prevent shaft slippage, the truth is that they can be a liability — adding concentrations of stresses in shaft connections, unnecessary cost, risk of imbalance, and other potential drawbacks.
7
and stopping. Service factors can often quantify the effect this value will have on assembly dynamics. Another aspect of reversing loads to consider is couplingmaterial fatigue. Keep in mind that some servocouplings that perform for years in regular applications with fail within weeks or sooner when forced to transmit power under reversing conditions.
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Ability to handle reversals: Servo applications that must make quick directional changes need special consideration. Here, consider torque associated with system inertia starting
motioncontroltips.com | designworldonline.com
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SERVOFLEX SFH-G
9
A realistic understanding of allowable misalignment: Flexible couplings for servo applications do accommodate misalignment. However, OEMs must be realistic about the level of permissible misalignment for a given axis — and specify assembly techniques and mounting that ensure levels that ever exceed the rating of the coupling. Otherwise, coupling or another component failure may occur.
Function to protect more expensive subcomponents: Though system failures are best avoided, couplings can be designed to protect the axis actuator or motor and gearbox by breaking if there’s a machine crash or catastrophic overload. That’s especially useful in high-speed servo applications where drive-based current limits aren’t fast enough to address existing kinetic energy associated with the drivetrain and load upon a jam or sudden impact.
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The AutomationDirect VFD here controls local conveyor functions. This is just one application for VFDs having logic capabilities — which often eliminate the need for a PLC.
AC drives
in conveying
Today’s VFDs perform far more than just traditional motor controls. Some include computing, I/O handling, and even motion-control capabilities. Such intelligent drives excel in smaller and localized systems.
Yaskawa America offers software called Singular to coordinate custom and off-the-shelf motion and robotic functions on conveying installations. It can optimize packing speed with more queuing flexibility and placement precision using servo axes and VFDs. Visit youtube.com and search "Design World Yaskawa Singular" for more information.
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Case in point from material handling: Some VFDs with onboard PLCs work for motion control on infeed conveyors. In one specific case, a photoeye and tower light wired locally into the VFD I/O provide operator data and response. When the conveyor is empty and idle, the motor is stopped — and the tower light illuminates to prompt operators to load the conveyor. When operators place product totes on the conveyor, the photoeye detects the totes and triggers the conveyor to start. Then the conveyor runs to transport totes according to a preset routine. After the cycle is complete (and no new totes are sensed) the conveyor stops. This minimizes energy consumption and system wear. Such localized automation can be easier to setup and troubleshoot than those employing centralized controls integrated into larger systems. Consider another process application for irrigation. Smart VFDs here can perform all local start, stop, level and pressure control using onboard logic. In this case, controls onboard the VFD can operate a pump with an alternating on and off time — and use local I/O to stop pumping when the supply tank runs low. Precise control over pump speed maintains ideal system pressure. What’s more, because a VFD is already necessary for the application, any additional control functionality is has with no additional hardware. Such a VFD might also have IoT connectivity to trigger alarms if system limits are exceeded. There are caveats: A larger water treatment skid is likely to need a standalone PLC, even if there are one or more VFDs onboard capable of executing controls. That’s because more complex applications have higher I/O counts to accommodate the signal monitoring and control of valves, level sensors, and chemical injection devices. Technical information provided by Jeff Payne — drives and motors group product manager at AutomationDirect. 11 • 2019
motioncontroltips.com | designworldonline.com
11/19/19 3:28 PM
POWER HAS COME FULL CIRCLE NEW! Introducing the GA800 AC Drive Your time is valuable. The new, easy-to-use GA800 AC Drive from Yaskawa gives you the power to make all of your operations better. • Rest easy with legendary Yaskawa quality and embedded functional safety. • Experience ultimate ease-of-use with DriveWizard® Mobile and optional Bluetooth ® connectivity. • Enjoy incredible torque production and network connectivity. Your days are complicated enough. Let us help simplify them. To learn more, visit or call Yaskawa today at 800-YASKAWA.
Yaskawa America, Inc. Drives & Motion Division 1-800-YASKAWA yaskawa.com
Yaskawa Electric America 11-19.indd 45 YAI-DW_11.2019.indd 1
For more info: http://go.yaskawa-america.com/yai1343
11/15/19 3:49 PM 10/16/2019 9:38:07 AM
MOTION SYSTEM APPLICATIONS
Intelligent drives
power IoT applications The most basic function of a dc drive is to control the speed of a dc motor. The best way to control the speed is by varying either the armature voltage or the field current. This is because the speed of dc motors is directly proportional to the armature voltage and inversely proportional to motor flux, which is a function of field current. Known for providing tight speed control and full torque at any speed, dc drives have an edge over more traditional ac drives that have a more narrow speed range and limited torque control. Also, dc drives are simple to start up, troubleshoot and maintain. Even dc motor brushes have become more robust and are less likely to require maintenance or replacement than they once were. On the other hand, ac drives are used to control the speed of an ac motor. For an ac motor, speed is determined by the number of motor poles and the frequency. A typical way to control frequency is via pulse width modulation (PWM). A PWM drive outputs a train of pulses to a motor and by modulating the pulse width, making it either narrower or wider, delivers an ac current waveform to the motor. One of the most common types of ac drives is the variable frequency drive (VFD). They operate by switching output devices on and off, which can be transistors, IGBTs (insulated gate bipolar transistors), or thyristors. VFDs can be either constant voltage or constant current, with constant voltage types being more common. They use PWM to control both the frequency and the voltage applied to the motor. VFDs have a number of significant benefits including energy savings. Controlling the amount of current drawn by the motor can decrease energy costs because the motor will not run at full load all of the time. This is becoming more important as motor efficiency continues to be a top design priority. Also, on motor start-up, VFDs can provide a crucial advantage. Without a VFD, an induction motor on start-up has to handle a high initial in-rush current. As the motor speeds up and approaches a constant speed, the current levels off from the peak in-rush values. With a VFD, the motor’s input starts off with low voltage and a low frequency, avoiding the problem of high in-rush currents. Eliminating the in-rush currents upon start-up also gets rid of the excessive torque on components, increasing the life of the motor and reducing maintenance costs and the need for repair.
INTELLIGENT DRIVES FOR THE IIOT Both ac and dc drives continue to evolve, adding functions and offering more intelligence across a range of industrial applications. Intelligent
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The NORD DRIVESYSTEMS application test area consists of an oval conveyor belt with rising and falling sections, as well as a bypass section with input and discharge points from the main route.
drive technology is key to digitalization and production automation, because it enables networked and autonomous production processes in smart factories. Companies like NORD DRIVESYSTEMS supply drive solutions (both hardware and software) and communications and application support for Industry 4.0 environments. NORD DRIVESYSTEMS drive units support intelligent IIoT digitalized production with advanced maintenance services. The industrial motor drives are built for easy integration with internal PLCs and a host of communication options for decentralized motion designs. In fact, the drives work with all common fieldbuses and Ethernet-based protocols and include analog and digital interfaces for sensors and actuators. The integrated PLC in the drive electronics allows autonomous control of sequences and movements to reduce the computational burden on the central controls. The drives also facilitate scalable design to accommodate changes to automation installations’ complexity, quantity, and size. NORD drives are prepared for integration into a cloud and can be connected to various external cloud systems. Fast, efficient and comprehensive evaluation of analog and digital data by the intelligent PLC in the drive electronics forms the basis for modern maintenance and servicing concepts such as condition monitoring and predictive maintenance. Due to continuous monitoring of the field level, linking of communication, sensors, process data, and vital parameters of the drive, deviations from the normal state can be quickly detected. Drive operators can motioncontroltips.com | designworldonline.com
11/19/19 9:39 AM
DC DRIVES
Intelligent, networked drives from NORD enable continuous condition monitoring, helping lay the groundwork for predictive maintenance.
then respond in good time before damage or breakdowns occur. Condition-oriented maintenance replaces time-based maintenance. This results in many benefits for users such as an increase in plant availability, prevention of unscheduled down times, improved planning of service and maintenance as well as a significant reduction in maintenance and repair costs.
motioncontroltips.com | designworldonline.com
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NORD is also investigating sensorless monitoring of oil aging and the condition of geared motors with virtual sensors. The aim is new predictive-maintenance designs to track when it might be best to change a gearmotor’s oil — based on the actual condition of the geared motor and the gear oil. For this, intelligent algorithms evaluate the operating
11 • 2019
data of the frequency inverter and determine the oil temperature from this information. Without the hardware costs for external sensors, oil aging and the optimum time for replacing the gear unit lubricant can be determined with great reliability. Tests have shown that the oil temperature as measured in tests can be reliably calculated.
DESIGN WORLD — MOTION
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MOTION SYSTEM APPLICATIONS
The new TELICA dual gantry motion system combines ETEL motion control technology with HEIDENHAIN encoders into a highly integrated solution that merges accuracy and throughput for the semiconductor and electronics industries. It features 1-µm placement accuracy at throughput rates of 10 kUPH (units per hour) for a typical flip-chip die bonding application.
Encoders help boost
semiconductor production
Encoders are essential to accurate positioning in many motion systems, particularly where high precision is most needed. For instance, applications like semiconductor manufacturing typically have nanometer precision requirements. Some new solutions for front-end and back-end processes in semiconductor manufacturing and electronics applications take advantage of developments in motion control, especially encoder technology. A newly developed motion system from ETEL, the TELICA, features an absolute position accuracy down to less than 1 µm, combined with extremely high accelerations and precision motion. The high-performance characteristics of these motion systems are due in no small part to optical encoders from HEIDENHAIN. Specifically, the low interpolation error of HEIDENHAIN encoders improves the performance of the linear motors and thus reduces heat transfer to the machine—even in highly dynamic applications. Through the resulting reduction in thermally induced error, the system exhibits greater accuracy and the same high dynamics. Measurement accuracy is further
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enhanced by the encoders’ non-thermally expanding ZERODUR scales. Low position noise and a low baseline error of less than ± 0.175 µm over a 5 mm interval also contribute to the exceptional accuracy and high dynamics of these motion systems. The motion systems were designed with extreme position stability in mind. In close collaboration, HEIDENHAIN and ETEL have developed a special solution for integrating the measurement systems. This design succeeds in protecting the encoders from possible heating, such as through the drive system, thereby shielding the measurement loop from thermally induced linear error. motioncontroltips.com | designworldonline.com
11/19/19 8:08 AM
Reliability Quantified
Accurate Precision
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Most complete line of rotary and drive encoders on the market Enabling automation technology in your most challenging motion control applications. Encoder solutions providing absolute speed and position accuracy along with condition monitoring, functional safety and lightning fast cycle times.
Check out our new Encoder Selector Tool
HEIDENHAIN CORPORATION, 333 East State Parkway, Schaumburg IL, 60173
www.heidenhain.us
847-490-1191
heidenhain.us
HEIDENHAIN | LEINE & LINDE | RENCO
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MOTION SYSTEM APPLICATIONS
Gears for torque Open gearing Intech Power
| courtesy
and tuning
Gears complement electric motors in industrial and consumer designs. For example, everything from amusement rides to consumer-grade beard trimmers make use of spur gears. These roll through meshing for up to 98% or higher efficiency per reduction. The only caveat is that they exhibit tooth sliding and noise due to initial tooth-to-tooth contact and audible shock loads. Helical gear reducers are costlier upfront than spur sets, but work in designs needing high horsepower and efficiency. Textile machinery, conveyor drives, rolling mills, and elevators all use helical gear teeth to engage gradually over the tooth faces for smooth operation and high load capacity. The only caveat is that the machine setup must include framing or supports to resolve thrust loads originating from the gears. Non-parallel and right-angle gears go into motion applications for material handling, aerospace and defense, packaging equipment and food-processing machinery. Input and output shafts protrude in different directions; gear teeth are worm, hypoid, bevel (straight, spiral or zerol), skew or crossed-axis helical. Common bevel gearsets often go into material-handling and packaging equipment. Hypoid gears (useful for high-toque applications) are like spiral-bevel gearsets, but output and input shaft axes don’t intersect — and that simplifies integration of supports. Common in aerospace, zerol gearsets have curved teeth that align with the shaft to minimize thrust loads.
Middle left: DieQua Corp. PGW Series reducers come in variations that are particularly suitable for belt and leadscrew-driven axes. Ratios are 3:1 to 1,000:1. Backlash is to ≤ 6 arc-min. and efficiency is to 95% or better. The PGW speed reducers are also quiet — generating operating noise that is less than or equal to 63 dB(A). Lower left: Consider a consumer-grade application. The Hoover Rogue 970 robot vacuum is capable of up to two hours of cleaning before recharging. Note the precision geartrain on the wall-edge brush assembly. | HOOVER • Techtronic Industries TTI
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motioncontroltips.com | designworldonline.com
11/19/19 1:23 PM
GEARING
BEHIND THE SCENES: MAKING GEARS TO MAKE GEARS Consider another machine-tool application. When Taiwanese company Chien Wei Precise Technology needed new CNC grinders to manufacture gears for robotics, they partnered with CNC supplier NUM. NUM’s Flexium+ 68 CNC systems on their machines let Chien Wei make both involute and cycloidal precision gears. Chien Wei makes vertical grinders, jig grinders, machining centers, coordinate measuring machines, and now gearing for robotic automation. The latter is typically planetary gearing (with involute gears) or cycloid gearing (with a reduced-epitrochoid rotor and cycloid stator). Planetary gearboxes are an industry mainstay, but cycloid drives have fewer moving parts and are more efficient at high reduction ratios. That’s because a speed reducer with a ratio of 200:1 might need three planetary stages with 12 involute gears. 200:1 with a cycloid drive needs just a single stator-rotor pair. The catch is that cycloid gears are difficult and expensive to manufacture. In 2015, Chien Wei brought gear manufacturing in-house for integration in its machines and for sale to machine builders. Initially its gear-grinding machine included a Fanuc series 0i-MF CNC, Mastercam CAD/CAM software, and a Chien Wei CMM. But the profile complexity of cycloidal gears meant that CMM data was inadequate — and customers purchasing the machines also had to buy expensive CAD/CAM software. So now, Chien Wei gear grinders include NUM profile grinding technology for simple, accurate, and flexible manufacture of both cycloid and involute gears. Chien Wei’s internal gear grinder is a nine-axis machine. A workpiece table rides a linear axis that moves towards a belt-driven grinding wheel on a linear-motor-driven vertical axis. The grinding wheel spins as the linear motor moves it up and down … all while the workpiece table continually advances. Both gear flanks are ground simultaneously. The machine also handles gear dressing with a disc and grinding wheel. The external gear grinder is an eight-axis machine — also with a direct-drive grinding wheel. Both machines include Flexium+ 68 CNC controls, FS153i HMIs, DXF file compatibility, and extensive machining databases. For more Planetary gearing is a mainstay information, visit designworldonline.com and in myriad applications. search Chien Wei.
Cycloidal gearing has few moving parts and efficiencies of 93% or better. Single stator-rotor combinations have ratios to 300:1.
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Honey, I’m home! Tired of working nights and weekends on motion control projects? It’s time to contact an automation specialist at SEW-EURODRIVE! We provide as little or as much help as needed, including a complete package from start to finish with project planning, software, components, commissioning, troubleshooting, and worldwide support. Get your free time back!
seweurodrive.com | 864-439-7537
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GEARMOTORS
Integrated gearmotors solve
material-handling needs
Gearmotors have long been
an industry
workhorse. Their greatest advantage is relatively high torque at low speed, making them suitable for a range of uses across industries with those requirements. Changes in machine design are impacting what gearmotor manufacturers are offering. For instance, the growth of compact machine designs makes space considerations a critical design priority. So in some cases, designers may have to sacrifice features — for example, to implement the needed gearmotor size while accepting use of less efficient gearing. Other trends impacting designs include more customized offerings based on end-user requests for more customized solutions that precisely fit design requirements. More manufacturers are offering customized solutions using more of their in-house engineering resources. This helps simplify the design process from the customer’s point of view. In addition, more custom offerings mean greater integration with other components in a design — leading to overall improved connectivity as well as fewer compatibility issues.
GEARMOTORS IN CRANE APPLICATIONS Consider one application — that of a slew crane made by Zurich-area-based Swiss crane manufacturer WOLFFKRAN. In fact, WOLFFKRAN is a world leader in slewing tower cranes, and its trolley (saddle) and luffing jib cranes are employed around the world for their robustness and easy assembly at construction sites. Slew cranes typically include a stationary base, undercarriage, mast, slewing ring, and jib and hoist — at the top of the mast to place loads within the jib's circumference of reach. Now, WOLFFKRAN uses standard hoist gear units as well as custom gear units from SEW-EURODRIVE for power transmission optimized to the tight footprint of its slew cranes — and the harsh outdoor settings that all cranes must endure. Hoist winches on the cranes are a key subsystem ... often transporting loads of 6 to 60 metric tons several hours a day. Plus the trend toward ever-taller buildings means that cranes' lifting distances are steadily increasing … so now it’s not unusual to see hoist winches that wind and unwind 1,000 meters of cable to execute load-transporting functions. Such cranes (and their drives) see considerable load.
Permanent-magnet ac motors (also called synchronous motors) from Bison Gear impart advanced velocity control to designs previously necessitating full servo control. The motors accept mounting of worm or high-efficiency hypoid gearing in various orientations to accommodate the needs of industrial machinery, conveying, and packaging applications.
DESIGN WORLD — MOTION
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Australia-based BCS Group chose NORD’s 92.1 series two-stage helical-bevel gearmotors with integrated ac drives for a sorting application at a customer’s material-handling facility.
SEW-EURODRIVE gear and gearmotor drive units power axes on WOLFFKRAN cranes.
For one such crane design, WOLFFKRAN required a hoist drive capable of delivering a nominal torque range of 27.5 to 175 kNm; it also needed an increased center distance to arrange the motor and rope drum on one side of the gear unit. Gear and gearmotor solutions from SEW-EURODRIVE satisfy these parameters. Oversizing of gear units is unnecessary because a U-shaped arrangement of rope drum and motor is implemented with a larger center distance; a protruding intermediate shaft accommodates the mounting of a disk brake. In fact, besides the hoist gear units, SEW-EURODRIVE also supplies the drive units for WOLFFKRAN’s crane trolleys.
GEARMOTORS IN INTRALOGISTICS The intralogistics industry is a fast-growing market — and motion-component suppliers aim to address the industry’s needs. One solution for large-scale intralogistics is the NORD LOGIDRIVE, a highefficiency gearbox integrated with an IE4 permanent-magnet synchronous motor and decentralized variable frequency drive. The VFD and IE4 motor support large speed ranges through a single gearbox-and-motor combination. The decentralized drive units are also service friendly thanks to plug-and-play technology. The modular design means all of the integrated motor’s components can be individually serviced — in turn minimizing maintenance and repair costs. With an aluminium housing and compact design, the integrated motor is also lightweight and unobtrusive. Another option for intralogistics applications is a line of two-stage helicalbevel gearmotors paired with VFDs for distributed control. In fact, Australia-based systems builder BCS Group recently employed these motors in a new materialhandling facility run by freight-transport company Toll IPEC. The facility can sort 35,000 parcels per hour. Such operations require an extensive conveyor system to move parcels around the facility. BCS chose upwards of 1,000 of NORD’s 92.1 series two-stage helicalbevel gearmotors with integrated ac drives for the job.
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motioncontroltips.com | designworldonline.com
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The DieQua Advantage We offer the widest range of servo gearheads and gearboxes, along with the experience and expertise to help you select the best solution for your application requirements. Right angle or inline, economy or precision, we have the gearhead to meet your needs!
Planetary Gearheads
• • • • •
Multiple backlash levels Precision and economy models Sizes from 42 to 220 mm Round or square face mounting Ratios from 3:1 to 1000:1
Precision Servo Gearheads
• • • • • •
Low backlash Right angle or inline Widest range of ratios Revolutionary motor mount Cast iron housings Special Designs
Precision Right Angle
Economy Right Angle
• • • • • •
• • • • • •
1 arc minute of backlash 5 output shaft options 10 sizes available Aluminum housing High radial capacity Maintenance-free
NEMA 23 & 34 motor interface Metric 40 & 60 motor interface Standard or hollow shafts Ground worm gears Flexible coupling connection Light weight aluminum
High Torque Gearheads
• • • • • •
Low backlash Right angle or inline Shaft, flange, or foot mounting High efficiency Cast iron housings Wide range of ratios
Precision Cycloidals
• • • • • •
Zero Backlash Precise Positioning High Repeatability High Stiffness Supports Tilting 10 Sizes
www.diequa.com 630-980-1133 DieQua 11-19.indd 55 motion control handbook 2019.indd 1
11/15/19 3:52 PM 11/12/19 10:37 AM
MOTION SYSTEM APPLICATIONS
HMIs play key role in
cobot/robot palletizing application A human machine interface — or HMI for short — is a control terminal on machinery to let operators monitor machine functions and adjust them as needed. This interaction is through a graphical user interface (GUI) that allows communications to and from supervisory controls and machine HMIs. HMI hardware consists of compact controllers with embedded functions, usually in the form of ruggedized touchscreens such as LCDs with tempered glass and cast-aluminum frames or even sealed enclosures for outdoor applications or indoor plant applications where oil, dirt, and machining byproducts are present. Today’s HMI technologies include increasingly flexible setups as well as ever-increasing resolution. There’s also been an uptick in affordable touchscreens and steady replacement of resistive displays with capacitive ones. These capacitive displays are used in medical and food-and-beverage applications needing bezelfree designs, as they’re sleeker and allow sterilization and easier cleaning. Solid-glass capacitive touchscreens also last longer than HMI hardware based on resistive technologies, because the screens don’t use pressure points to form circuits, so don’t wear or lose sensitivity over time. What’s more, many HMIs with capacitive displays have the multitouch capabilities of smartphones, which lets OEMs leverage user familiarity to offer intuitive interfaces.
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Newer HMI designs now offer advanced connectivity options as well as signal and data processing capabilities. This means that HMIs only a few years old are being superseded by new HMI software and hardware systems capable of supporting IoT functionality. These new HMIs let operators make more use of plant and machine data in increasingly automated operations. One recent example of a robotic application highlights the important role the HMI played in the selection process. Nestlé recently installed two units of CoboAccess_Pal, an industrial, safe and easy-to-use cobotic palletizing solution from Sidel, at their site in Orbe, Switzerland. By automating the palletizing of their Special.T capsules, Nestlé Suisse SA Orbe gained higher pallet quality while offering increased ease-of-operations for their workers. The latter benefit was ensured by the solution’s automation platform; based on the combination of PC and PLC, it allows better-controlled trajectories for improved cobot picking and placing. motioncontroltips.com | designworldonline.com
11/18/19 3:33 PM
HMIs
Nestlé Suisse SA Orbe was looking to use cobotics or collaborative robotics palletizing, an innovative Industry 4.0 technology. They required a robust, precise and user-friendly cobotic solution. Cédric Rey, Fill & Pack Maintenance & Improvement Manager at Nestlé, describes the implementation: “At our Orbe site, best in class pallet quality is absolute key, as our cases with the tea capsules are very light, long, and narrow. This is why accurate case placement on the pallet and tight layers are major requirements to guarantee pallet stability, given that products are moving through the complete supply chain, respecting their full integrity and ultimately ending up in consumers’ hands without any damage. We also needed to ensure the safety of our operators so it was imperative that the same level of safety would be maintained after switching from manual labor to a cobotic technology, ensuring that the solution is working safely with no fences around it. For us, the user friendliness of the new cobotic solution was extremely important as well: for instance, an intuitive navigation of its HMI was a must.” At the Orbe site, two cobotic palletizers have now been installed downstream along two Cermex SW21 compact side-loading case packers. What’s more, CoboAccess_Pal’s HMI is well suited to meet the customer’s requirement for a user-friendly solution. Based on an intuitive tablet approach to navigation, the HMI facilitates the daily jobs for Nestlé Suisse SA Orbe operators, as they can access Standard Operating Procedure (SOP) and maintenance sheets for easier and faster trouble shooting and root cause analysis. Sidel made sure to get the safety of the CoboAccess_Pal objectively validated by Apave in addition to the equipment’s full compliance with European Machinery Directive 2006/42/EC. CoboAccess_Pal always performs case handling above the conveyor or the pallet station, which ensures that cases never fall on the floor, therefore adding to maximum protection.
WE’RE MORE THAN YOU THINK
BASIC & ADVANCED HMI
SMART IoT HMI
EASY MACHINE CONTROL From basic to advanced features, our HMIs provide options that meet today’s changing requirements. Class I, Div 2 is also available on select models.
HMI CONTROL FOR SMART FACTORIES The Smart cMT HMI series makes it easy to monitor & control industrial processes from remote devices such as PCs, smartphones, and tablets.
HMI + PLC
INDUSTRIAL PC
COMBINING HMI AND PLC This series supports high-speed counters and timers, provides serial and Ethernet communications, and allows for Native Ladder or IEC programming.
CONFIGURABLE & POWERFUL Our Industrial PC series features both Panel and Box industrial options for projects requiring greater horsepower. Storage upgrades are also available.
PLC FIXED & EXPANDABLE OPTIONS Our Class I, Division 2 PLCs offer digital and analog I/O and support high-speed counters and PWM. Analog modules support voltage & current modes and connection to thermocouple sensors.
DESIGN WORLD — MOTION
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maplesystems.com · (425) 745-3229
11/15/19 2:57 PM
MOTION SYSTEM APPLICATIONS
Linear guides and slides
in designs light and large
Linear guide systems include guide rails, slides and ways. Industry categorizes them into a few basic types as well — including profile rails, drawer slides, linear bearings, guide wheels and plain bearings. A typical arrangement includes a rail or shaft, and carriages and runner blocks. They can also be distinguished by the method of contact, either sliding or rolling. A major function of rolling guides is to reduce friction in machines. They’re used in various applications ranging from advanced semiconductor manufacturing devices to large machine tools and construction equipment. Semiconductor manufacturing equipment or inspection apparatus that requires high precision positioning is a good application for linear guides. In the case of a machine tool for cutting, linear guides are used instead of sliding-contact linear-motion bearings to cope with temperature rise and durability issues associated with ever-increasing feed speeds. The classic application for profile rails is in the machine tool industry where load capacity, stiffness and accuracy are paramount. In medical equipment such as CAT scan, MRI and x-ray machines, square rails are more common. On the other hand, round rails can offer several advantages, one of which is the ability to run smoothly when mounted to less than perfect surfaces—defined as having a flatness error of over 150 μm/m. For cleanroom and food-processing applications that can’t tolerate contamination, linear guides that use rolling elements (as well as plain bearing systems) are unsuitable because of their need for lubrication requirements. Some applications demanding extremely high precision and accuracy use fluid-floated bearings for the highest accuracy and precision possible. These are hydrostatic or aerostatic bearings using a highpressure fluid between the rail and carriage. They’re more expensive and harder to manufacture than other linear options but get top precision and accuracy.
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Festo software and hardware simplify the design of multi-axis linear motion. More specifically, the Handling Guide and Motion Control Package online tools slash the cost of engineering, assembling, and programming Cartesian robots. Festo slides in such systems include the mini slide EGSC (for interoperability and quick assembly) and the DGSL mini slide for pick-and-place axes.
SCHNEEBERGER MONORAIL AMS linear guideways include an integrated measuring head and scale. Combining guidance and linear-motion feedback helps applications that have space constraints but need top performance.
motioncontroltips.com | designworldonline.com
11/18/19 3:31 PM
Precision Linear Motion
when you need it
NOW! ISO 9001:2015/ AS9100D CERTIFIED MADE IN USA
Whether it’s
Custom Engineered or
Standard Slides...
OEM’s choose Del-Tron! Order Today! 800.245.5013 Solid Models Available for all Del-Tron Model Numbers
Del-tron — 03-19.indd 59
www. b uyd el t ro n.co m
11/15/19 3:55 PM
MOTION SYSTEM APPLICATIONS
Important considerations for choosing a linear-motion rolling guide include the loading (both static as well as applied), the stroke and speed, as well as the desired precision and accuracy and the required life. Preloading is sometimes needed as well depending on application requirements. Lubrication is another important consideration, as is any method to minimize contamination of the linear guide system from environmental factors such as dust and other contaminants using bellows or special seals.
MORE ON THE GEOMETRY OF DUAL GUIDE RAILS Linear guide rails and bearings offer high stiffness and good travel accuracy. They can support not only downward, upward, and side loads, they can also withstand overhung, or moment loads. Of course, the larger the linear rail and bearing system, the more moment capacity it has, but the arrangement of the bearing raceways — face-to-face or back-to-back — also influences the amount of overhung load that it can support. While the face-to-face design (also known as the X arrangement) provides equal load capacities in all directions, it results in a shorter moment arm along which overhung loads are applied, which reduces moment load capacity. The back-to-back arrangement (also known as the O arrangement) provides a larger moment arm and gives higher moment load capacities.
This is an IKO slide on a long-stroke axis.
For Material Handling,
we’ve got your motion feedback solution From raw material to finished product, EPC’s encoders provide motion control to keep your manufacturing process moving. When you call EPC, you talk to engineers and encoder experts who can help you find the right encoder for almost any material handling application, including: Cranes · Conveyors · Gantries · Lifts · Motor Speed Feedback · Palletizers Call us today. We’ll help you find your motion feedback solution.
Standard lead time: 4-6 days Same day shipping on many models
1-800-366-5412 | encoder.com
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LINEAR GUIDES • SLIDES • RAILS
Solving cleanliness and reliability issues on linear axes with bearings 3D printers are a cutting-edge manufacturing technology, but they must adhere to traditional equipment design rules. They need bearings to allow motion, and these bearings require lubrication. Oil and grease are typically used … but both are notoriously messy and can migrate from the bearing — in turn contaminating the machine and workpieces. Such contamination is tolerable on certain industrial equipment, but contamination of a product in a 3D printer setting can degrade the product itself during the building phase. One 3D printing company in the southeastern U.S. recently had this oil-contamination problem with bearings on their printer-wheel carriage arms. The linear-motion axis bears relatively light load (20 kg) but runs at high speed (500 mm/sec) which leads to temperatures reaching 662° F. So bearing lubrication was transferring onto finished product during tests — an unacceptable contamination. The additive-manufacturing company tried running the axis unlubricated, but the high speeds and temperatures quickly caused bearing failure. The company’s engineers also unsuccessfully attempted to design their own auto-lube system to fix the problem. They even tried oil-impregnated metal bushings ... but these wore out too quickly. That is when the 3D-printing service provider turned to Graphalloy, a specialty-bearing company offering a
graphite-metal alloy by the same name. Graphalloy comes in more than 100 grades, and all are self-lubricating, non-galling, and dimensionally stable. This stood out as a bearing solution for a couple of reasons. The material does not require traditional lubricants that can contaminate the precision process. It could also handle the high linear speed and emperature of the application. More specifically, Graphalloy materials can operate to 1,000° F, far above the operating temperature of traditional industrial lubricants. The company’s engineers tested Graphalloy GM 111.3 bushings in this application for more than a year and remain very satisfied with the bushings’ life. In fact, the original test bushings still work on their prototype 3D printers with virtually no wear. Currently the design engineers forecast a life of one year on the new bushings with the machines running at full production capacity. The company uses the 3D printers for on-demand manufacturing, which includes anything from prototypes to replacement parts for all types of industries — including the fast-growing medical-device industry. This is a world where research, design, and production are happening at lightning speed. Such innovations should not be limited by motion components.
Graphalloy supplies bearing and lubrication technology to let 3D printers work cleanly and reliably.
s
16 AM
motioncontroltips.com | designworldonline.com
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DESIGN WORLD — MOTION
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MOTION SYSTEM APPLICATIONS FACE-TO-FACE RACEWAY: SHORT MOMENT ARM
The face-to-face raceway arrangement results in a shorter moment arm and lower moment capacities. The face-to-face design is also known as the X arrangement because the contact lines between the balls and the raceways point inward, forming an X inside the rail.
a
BACK-TO-BACK RACEWAY: LONGER MOMENT ARM
The back-to-back raceway arrangement produces a longer moment arm and higher moment capacities. The back-to-back design is also known as the O arrangement because the contact lines between the balls and the raceways point outward, forming an O around the rail.
a
DUAL GUIDE RAILS AND MOMENTS
F r1
When dual guide rails with one bearing each are used, no roll moments (Mr) are induced; only pitch (Mp) and yaw (My) moments. F Z (X Z Y Z Z Z ) Y F Y (X Y Y Y Z Y )
MP
F S1
F S1
F r2
F S2
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F X (X X Y X Z X )
F r1
F r2
CENTER OF DRIVE
DESIGN WORLD — MOTION
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But even with the back-to-back arrangement, linear guides have a relatively short distance between the raceways (essentially equal to the width of the rail) which limits their ability to handle roll moments, which are caused by loads overhung in the Y direction. To counter this limitation, using two rails in parallel — with either one or two bearings on each rail — allows the roll moment to be resolved into forces on each bearing block. Because linear bearings have much higher capacity for forces than for moments (especially roll moments), bearing life can be significantly increased. Another benefit of using dual guide rails and allowing moments to be resolved into forces is that linear bearings generally deflect less under pure forces than under moment loads. Many linear actuator designs include two rails in parallel with the drive mechanism — belt, screw, or linear motor — incorporated between the rails. While it’s not imperative that the drive be centered between the guide rails, doing so helps ensure even loading on all of the bearings, and reduces cogging, or uneven drive forces on each rail and bearing set. This arrangement also reduces the height of the actuator, making it relatively compact given the high load and moment capacity provided by the dual guide rails.
MY
F S2
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X
Above: THK America roller-based linear-motion (LM) guides from the manufacturer’s Type HRX series include a duplex face-to-face structure for top performance even in harsh settings. A synthetic resin cage with a patented curvature cradles and separates the rollers. Space between the rolling elements retains grease for maintenance-free operation.
motioncontroltips.com | designworldonline.com
11/18/19 3:32 PM
UTILITRAK ® VC WHEEL PLATE
UTILITRAK ® VEE & C CHANNEL
WE’RE MORE THAN 4 We invented the DualVee® guide wheel over 50 years ago in four sizes of carbon steel as a component based problem solver for harsh, debris-laden environments. It’s 2019. As part of our ever-growing collection of innovations, we now offer Vee/Crown Series UtiliTrak® which incorporates a versatile wheel design that can run on both vee and C-profile channels. It is ideal for medium to heavy duty transport applications, and offers high speeds, excellent load capacity, smooth antifriction operation, and debris tolerance. UtiliTrak® VC Series is now available as part of our QuickShip Program. The Bishop-Wisecarver QuickShip Program guarantees UtiliTrak® VC Series with qualifying configurations to be on its way to you within 3 business days of order placement. UtiliTrak® linear guides are designed for commercial applications where easy installation and minimal maintenance requirements are the primary design objectives. The new vee/crown wheel plate is the best of both the 90° wheel and MadeWell® crown roller designs. It provides high reliability, easy installation, is low in maintenance requirements, and allows up to 2° of misalignment to accommodate imprecise mounting of parallel channels.
QUALIFYING CONFIGURATIONS • (Vee/Crown) Series • Sizes: 0 – 3 • Quantity: Up to 15 wheel plates
• Channel Length (m) & Quantities: > .5
Up to 8
.5 – 1.0
Up to 6
1.0 – 1.5
Up to 4
1.5 – 2.0
Up to 4
2.0 – 2.5
Up to 2
Expertly Designed, Delivered to Perform
Contact us to discuss your specific guided motion needs
Bishop-Wisecarver 11-19.indd 63
888.580.8272
| BWC.COM
11/15/19 3:55 PM
MOTION SYSTEM APPLICATIONS
Automotive, medical, robotic applications
benefit from dc motors
Among motors used in industrial and motion applications, dc motors are still some of the most common including brushed, permanent magnet, as well as brushless dc motors. Thanks to continuing improvements, dc motors have found their way into a wide range of applications. For instance, they’re common in automotive manufacturing, particularly as the number of motors used for various systems and subsystems in cars goes up – for everything from window and door controls to seat adjustment. Other areas have also been seeing increased usage of dc motors, particularly in medical applications. The fact that many of these applications are limited in space and need small motor designs to fit makes them particularly attractive. That, and that they offer a balance of power and torque in a compact package makes them well suited to uses in many medical applications, such as in surgical hand tools. Aside from their prevalence in automotive and medical applications, industrial applications involving robotics are using dc motors to solve the unique challenges of building the next generation of robots and collaborative robots, or cobots. Case in point: As collaborative robots have proliferated, the need for a wide variety of grippers and end effectors suited for a range of uses has also grown. One of the most challenging applications is for automated gauging and measurement of small parts. Here, end effectors must provide high-resolution positioning with resolutions as low as 2.5 micrometers. This information must also be continually available to decision-making software in many different automation applications.
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The Precision Parallel Gripper from New Scale Robotics is shown here attached to the end of a robot arm.
motioncontroltips.com | designworldonline.com
11/19/19 2:38 PM
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MOTION SYSTEM APPLICATIONS The NSR-PG-10-20 Precision Parallel Gripper incorporates maxon’s EC-20 flat motor for high precision operation in gripping and positioning.
maxon’s EC-20 flat motor provides the smallest size motor with the proper torque capabilities to best handle the requirements of the precision grippers.
New Scale Robotics (NSR), a division of New Scale Technologies, designed and manufactured their latest gripper for the smallest collaborative robots. The NSR-PG-10-20 Precision Parallel Gripper is a mechatronic system that integrates a motor, sensors, precision bearing guides, a drive and control electronics along with embedded firmware for automation all into one device. An important design feature that NSR included in the gripper is the ability to offer plug-and-play integration that could be installed quickly on the Universal Robotics (UR) line of small cobots. The NSRPG-10-20 offers users the smallest size and mass with the highest precision. All power and control circuitry is located through the robot tool port and slip rings so that no external cable or electronics boards are required. The gripper mounts to the UR robot tool flange and connects via a single cable to the UR tool I/O port. Motion commands are received through the robot’s 8-pin tool I/O interface. No external wires or separate electronics are needed, which allows for full 360-degree or infinite rotation of the UR robot wrist joint without cable interference. The Precision Parallel Gripper incorporates an internal absolute position sensor specifically for automated metrology applications offering high precision for intricate small part handling, measurement, sorting, and assembly. The grippers had to provide fast, precise movements repeatedly over a long life cycle. The motor for the Precision Parallel Gripper is the EC-20 flat brushless dc (BLDC) motor from maxon.
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The motor offers up to five winding types as well as built-in encoders and multiple power outputs. The motors were selected because of their torqueto-mass ratio. Specifically, they weigh only 15 g and feature high continuous torque of 3.75 mN-m. This helps the gripper attain a gripping force of +/- 3 to 10 N while using a modest gear ratio of 16:1. The gripper also incorporates a symmetric timing belt drive with a range of 20 mm. Plus, the operational voltage, current, and torque were a good match with the internal robot power supply. The BLDC rotary motor drives gear reduction to a timing belt that converts rotation to linear motion. A separate angle sensor is used to measure the motor shaft angle, while separate digital electronics are used to generate the three-phase drive current needed for operation. This mechanism provides the linear motion necessary to open and close the gripper fingers used to grab and release small parts. Gripper fingers are able to grip from the outside or inside of the part depending on the application. Through the use of an embedded sensor, the linear part measurement resolution of the gripper is 2.5 micrometers. The open/close speed of the gripper is 20 mm/sec and the open/close range is 20 mm.
11 • 2019
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MOTION SYSTEM APPLICATIONS
Integrated motors
pack more punch Well established by now, integrated motors (also referred to as smart motors) are a more common option in many motion control and automation system designs. Basically, an integrated motor is a combination of a motor and a number of other components combined together into one physical unit. Common configurations include a motor and drive, but can also consist of integrated encoders and controllers as well as cabling and communication ports. Communication options can include serial communication links such as RS232 or RS485 and advanced network topologies for complex motion control tasks—CANopen, DeviceNet, or Ethernet protocols. For machine builders, integrated motors help reduce machine size and complexity. That’s because smart motors significantly reduce the amount of space required for a machine by consolidating components, eliminating cabling, and possibly the need for entire enclosures. Integrated motors can also in some cases eliminate external controllers such as PLCs. With the increased use of decentralized motion-control architectures, applications using integrated motors have only proliferated. As an alternative to centralized motion control, decentralized architectures distribute motion control to a number of individual motion axes (in this case, to individual integrated motors), eliminating the need for a central controller. This means that individual motors can execute the control closer to the actual axis of motion or load, thereby taking the computational burden off of a central controller and distributing it to individual integrated motors. Adding to their appeal, new integrated motor products featuring improved networking capabilities are making them even more attractive for applications where space is at a premium or for uses in remote locations. For instance, a new
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StepSERVO motors from Applied Motion Products are IP65 rated to handle challenging wet or dusty environments such as in factories or food and beverage applications.
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MOTION SYSTEM APPLICATIONS
RELIABLE MOTION SOLUTIONS. HIGHLY COMPACT SMARTMOTOR™ SERVO SOLUTIONS FOR AUTONOMOUS VEHICLES.
integrated motor from Applied Motion Products features Power over Ethernet (PoE), which provides dc power and Ethernet communications on a single cable. Such a function is commonly used in IT applications such as wireless access points, IP cameras and VoIP phones. The TSM14POE StepSERVO integrated motor combines a motor with an encoder, drive and controller, all combined into a single integrated package. The motor gets power and Ethernet over a single cable, eliminating the need to connect motor power and feedback cables to an external motor controller and simplifying design and installation. Built upon the company’s StepSERVO closed-loop stepper technology, the motors provide a number of benefits over conventional open-loop stepper motors including higher torque and greater efficiency. Specifically, the motors are NEMA 14 frame size and feature an integral 4,096-count magnetic encoder providing high position and velocity accuracy. Applied Motion’s Q Programming language lets the motor run motion control profiles on its own as well as react to messages on the Ethernet network. One of the significant benefits of integrated motors is the ability to execute control programs stored within the motor. Having the ability to execute stored programs created with the Q Programming language lets designers apply complicated logic and motion sequences to solve challenging motion control problems. For instance, in a product labeling application in a food and beverage plant, a product sensor can be tied to one of the motor’s digital inputs, triggering a WI (wait input) command when the product nears the labeling position. To prevent wrinkling or tearing, the label must be applied at the same speed that the product is traveling on the conveyor. To accomplish this, the motor measures the conveyor speed from a master encoder whose A/B quadrature signals feed into the motor’s X1 and X2 digital inputs. The FE (follow encoder) command automatically ratios the label speed to the master encoder frequency while monitoring the label sensor to position the label at exactly the right location on the product. The math capability built into the Q Programming language offers additional customization and control options for a range of other applications as well.
• Fully integrated designs • Most compact, power-dense solution on the market • Complete servo system
Learn how our easily deployable programming language gets your machine to market faster at animatics.com
www.animatics.com
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TITLE GOES HERE
The stainless-steel housing and smooth surface of the Kinetix VPH hygienic servomotors from Rockwell ensure they meet strict hygienic standards.
Servomotors see action in
food and beverage manufacturing Servomotors are used on machine axes that need to make complex moves or position loads with really high precision. Servomotors can also run at zero rpm while holding torque to keep a load at a set position. For these reasons and more, servomotors are a common choice in a diverse array of applications including those involving conveying and material handling. But for equipment used in food and beverage manufacturing, they must also be able to withstand washdown and cleansing conditions and meet certain hygienic standards. Case in point: In food and beverage manufacturing, demand for more product varieties is creating a need for smaller, more flexible machines with the HMI located in close proximity to the process. But such products must also stand up to the rigors of contamination and cleaning. motioncontroltips.com | designworldonline.com
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Food and pharmaceutical makers can protect their products (and meet regulatory requirements) with hygienic industrial control hardware. The Allen-Bradley Kinetix VPH hygienic servomotors and a new stainless-steel version of the Allen-Bradley PanelView Plus 7 graphic terminal help minimize contamination during production and ease compliance. The stainless-steel PanelView terminal can be used on a machine in a splash or contaminant zone without the need to be covered or isolated. This helps protect product quality and simplifies the cleaning processes, while removing obstructions to the HMI, so operators can better monitor production. The general-purpose HMI terminal is certified by the National Sanitation Foundation (NSF). It has an ingress-protection rating of IP69K to support high-pressure, hightemperature chemical wash downs and also uses a food-grade silicone gasket with a distinct blue color to help production workers notice if it’s been damaged and needs to be replaced. 11 • 2019
The Kinetix VPH hygienic servomotors can improve machine reliability while enhancing consumer safety by meeting stringent hygienic standards. The hygienic design – including high-grade stainless-steel housing and a smooth surface – can withstand washdowns and reduce the risk of contamination. The servomotors are designed per the EHEDG and 3-A sanitary standards and are IP69K rated and NSF certified. They also seamlessly integrate with the Allen-Bradley Kinetix 5500 and 5700 servo drive platform, using single-cable technology to help optimize a machine’s speed and accuracy. And they’re available in a range of sizes and options to help meet a variety of application needs in food and pharmaceutical production.
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MOTION SYSTEM APPLICATIONS
Güdel gantry robots add gentle touch
to bakery automation
In the U.S., about 50 million people a day eat at fast-food restaurants — and about 60,000 of those establishments sell hamburgers. That requires epic volumes of fresh buns every day … and only commercial bakeries with automated operations can output sufficient production volumes. Workhorse Automation Inc. (based in Oxford, Pa.) supplies machines to this commercial-bakery industry, including panstacking and storage equipment such as four-axis palletizing robots. But Workhorse Automation saw that the industry needed automation solutions with even greater throughput and reach than that of stationary robots. Established in 2003, Workhorse Automation specializes in the engineering of automated solutions for commercial baking. The machine builder sells turnkey automated bakery solutions that excel on new lines and can be retrofitted into existing lines. Top design goals are flexibility, reliability, and productivity with automated and robotic systems. After extensive R&D, Workhorse Automation began offering equipment that includes a two-axis Güdel ZP-4 gantry robot using Allen-Bradley motion and programmable logic controls. This new solution lets Workhorse Automation end users increase stacking speeds while maintaining gentle, safe, and accurate operations. Workhorse Automation engineers made the equipment both user and maintenance-friendly by integrating the conveying systems, end-of-arm tooling, and Allen-Bradley control to the gantry robot. The first such Güdel gantry-based system was installed in 2011 and is still in successful operation. In fact, Workhorse Automation supplied such a Güdelbased system to the award-winning Clayton, N.C. facility of Northeast Foods – Automatic Rolls. This facility produces 1,400 buns per minute (2 million every 24 hours, primarily for McDonald’s restaurants) using Güdel gantry-based pan-stacking systems and Workhorse Automation automated storage and retrieval systems (AS/RSs). Each Workhorse Automation system includes as many Güdel ZP-4 gantry Z-axis arms as necessary to meet the throughput requirements. In some cases, two gantry arms operate over one bun-pan conveying system. Each Z-axis arm can stack and destack pans. Each customer’s application necessitates pans of different sizes and quantities — in turn needing the setting of gantry strokes in Z and Y-axes to customer-specific parameters.
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Here, grippers suspended from a Güdel robotic gantry handle bun pans for stacking.
Pan stacking and destacking are critical functions because pans are specific to bun type being produced. Case in point: To ensure freshness, the Northeast Foods facility makes four different bun styles every day — each requiring a different style of pan. The pan-changeover process is automatically handled by the Workhorse equipment. A human operator only needs to visually confirm that pans clear the system at production-run ends. Even changing between pan types doesn’t reduce throughput. motioncontroltips.com | designworldonline.com
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AEROTECH NANOPOSITIONERS Linear Stages • Rotary Stages • Vertical Lift and Z Stages • Goniometers Aerotech nanopositioners provide the nanometer-level linear accuracy and sub-arc-second rotary accuracy required for today’s leading research, development, and production efforts.
Our linear nanopositioners offer: • 1 nm resolution • <1 nm in-position stability • ±75 nm repeatability • ±250 nm accuracy • Up to 160 mm travel
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Visit aerotech.com or Call 412-963-7470 Since 1970, Aerotech has designed and manufactured the highest performance motion control, positioning tables/stages, and positioning systems for our customers in industry, government, science, and research institutions around the world. AF0119B-RAD
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MOTION SYSTEM APPLICATIONS
Here Güdel ZP-4 gantry Z-axis arms handle loaf pans.
“Güdel gantry systems let us significantly improve pan-stacking processes,” says Workhorse automation sales manager Ken Mentch. “With the gantry robots, we can increase pan size and weight — and handle multiple pans simultaneously — even while reducing motion speed requirements. The optimized design footprint of the gantry serves just the work envelope needed for the application," Mentch adds. Replacing the conventional magnetic machines used previously for pan stacking — facetiously nicknamed pan crushers by the industry — reduces damage to pans and the clatter of the pan-handling process. “The gantry lets us create gentler, quieter, and smoother automation," Mentch says. Especially over the last couple years, the bakery industry come to recognize how gantry systems improve operation and reliability — and has begun migrating from pan crushers to this type of robotic automation. Güdel has supported Workhorse Automation through this growth. For more information, visit gudel.com and www.workhorseautomation.com.
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MOTION SYSTEM APPLICATIONS
Sensors and transducers
in die casting and more
Sensors and transducers for motion designs and related systems abound. Consider the monitoring of mold deformations in aluminum die-casting. Here, inductive eddyNCDT displacement sensors from Micro-Epsilon use eddy currents to track gaps in aluminum die-casting processes. These precision sensors increase the service life of the tools involved and product quality, while rejects and expenses are reduced. Their robust sensor design also enables gap measurements in harsh ambient conditions. In the production of aluminum die-cast parts, liquid aluminum is pressed into a mold under high pressure. The two mold halves must be held together with significant force. Despite this high contact force, the tool halves are pressed apart minimally. This process is also called mold breathing. Although minimal openings are normal and intended during this process, a gap causes fraying on the component if it is too large. These splinters must be reworked to meet the high quality requirements of the final product. If aluminum residues remain on the tool, they also lead to increased wear, which reduces tool life. Monitoring tool deformation using inductive displacement sensors based on eddy current enables high product quality combined with improved tool life and reduced rework. Usually, three to four eddyNCDT 3005 eddy current systems are used to ensure consistent gap monitoring at several measuring points. A system consists of a compact and robust controller, which together with the cable and sensor form a unit. The integrated system design increases robustness and resistance to external factors, making the system insensitive to high temperatures, dust, dirt or pressure, and delivers accurate results regardless of the environment.
The compact design of Micro-Epsilon eddyNCDT 3005 sensors mean they can integrate into existing machines. PLASTIC INJECTION MOLDING FORCE FEEDBACK
Mold core
Stationary platen
Clamping motor Rear platen
Molded part
LCF Series load cell
CLAMPING CONTROL WITH SENSORS
Consider another application of sensors in die casting as well as IAAA Series amplifier injection molding. During these additive-manufacturing processes, the mold is clamped together to resist the rapid thermal expansion and contraction caused by the molten material filling the mold PLC cavity. Flawed parts can be created if the mold is not kept properly data acquisition clamped to resist thermal loading throughout the molding and USB Series Here, FUTEK’s LCF Series universal casting process. To mitigate pancake load cells pair with an IAA Series these thermal effects, some analog amplifier for feedback into a PLC. designs include pancake load The sensor provides force feedback for cells at the clamp contact precise control over a plastic injectionpoints — enabling a machinery molding process. monitoring processes to adjust clamping forces.
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Mold cavity
IHH500 and IPM650 digital displays
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SENSORS & TRANSDUCERS
The harsh settings of mobile equipment include sustained exposure to heat, cold, shock, vibration, water, ice, mud, and dust. Now a line of sensors from SIKO called PURE.MOBILE includes ruggedized kits specifically designed to withstand these conditions. All PURE.MOBILE sensors meet EMC requirements for construction, agricultural, and forestry machines. They also satisfy E1 (UN ECE R10) for road vehicles. The robust wear-free designs employ magnetic sensing technology to withstand temperatures from -40 to +85° C (and even to 105° C in some cases) and provide sealing to IP65 or IP69K. Design engineers can also select option cards to add functionalities to SIKO rotary encoders with PURE.MOBILE technology — for an integrated inclination sensor, DIP switch for easy parameterization, or digital inputs and outputs. The sensor core is the same for these customer-specific adaptations for cost-effectiveness — even for smaller quantities. Safety version to Performance Level d (PLd) are also available. In addition to familiar analog current or voltage interfaces, engineers can also choose from CANopen, CANopen Safety, or SAE J1939 interfaces.
Hexapods for Multi-Axis Precision Motion PI Hexapod 6-axis parallel positioning systems with userprogrammable pivot point speed up alignment, complex positioning, and motion simulation tasks. With load capacities from 1kg to 2,000kg and precision from nanometers to microns, Hexapod success stories include photonics, medical, and automotive applications since 1993.
Hexapod Alignment Applications Radio Telescope Reflectors
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Image: FormFactor
Physik Instrumente www.pi-usa.us 508-832-3456 AskPI@pi-usa.us
PI designs and manufactures precision motion systems at locations in the USA, Europe, and Asia. With over 40 years of experience developing standard and custom products based on piezoceramic and electromagnetic drives and more than 1,300 employees in 13 countries, PI can quickly provide a solution for your positioning and automation projects in industry and research.
DESIGN WORLD — MOTION 11 • 2019 PRECISION | SPEED | STABILITY - MOTION CONTROL & POSITIONING SOLUTIONS
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MOTION SYSTEM APPLICATIONS
Shock-absorber technologies
for automated applications By Larry Cavalloro • ACE Control • www.acecontrols.com
A top objective for designers of industrial-automation machinery is to build and tune axes for minimal vibration (free or forced); gently and precisely slow axes’ moving masses; and render unavoidable machinery vibration either isolated or damped — in other words, fully dissipated. These techniques let machine axes settle back to equilibrium as quickly as possible — which is especially useful for those running high-speed reciprocating, positioning, or other precise automation tasks. The vast host of options for damping and vibration isolation include industrial and safety shock absorbers, profile dampers, rotary dampers, industrial gas springs, hydraulic dampers, vibration isolators, air springs and hydraulic feed controls. We put the technologies into four broad categories. Automation control with shock absorbers and dampers include miniature shock absorbers, industrial shock absorbers, heavy industrial shock absorbers, profile dampers, and damping pads. Options for motion control include push-type and pull-type industrial gas springs, hydraulic dampers, hydraulic feed controls, door dampers, and rotary dampers.
Variations classified as vibration control include rubbermetal isolators, vibration-isolating pads, and low-frequency pneumatic leveling mounts. Safety products include safety shock absorbers, safety dampers, and clamping elements. In this feature, we focus on one leading option from the first category — that of automation control with industrial shock absorbers.
INDUSTRIAL SHOCK AND DAMPING OPTIONS COMPARED
Hydraulic dashpots deliver a high stopping force at the stroke start. With only one metering orifice, moving loads under the control of a hydraulic dashpot sees abrupt slowdown at the start of the stroke. Braking force rises to a high peak at the start of the stroke (giving high shock loads) and then falls away rapidly. Springs and rubber buffers exhibit high stopping forces at end of stroke. At full compression, they also store energy rather than dissipating it … causing loads to rebound. Air buffers and pneumatic cylinder cushions output high stopping force at end of stroke. Due to the compressibility of air, these exhibit sharply rising force towards the stroke end … so most of the energy is absorbed near the end of the stroke. Industrial shock absorbers deliver uniform stopping force through the entire stroke. The moving load is smoothly and gently brought to rest by a constant resisting force throughout the entire shock absorber stroke. The load is decelerated with the lowest possible force in the shortest
Industrial shock absorbers from ACE Controls include MC33 to MC64 models for high energy absorption. Capacity is 155 to 5,100 Nm per cycle and impact velocity range is 0.15 to 5 m/sec and beyond for custom builds. The shock absorbers mount in any orientation and include an integrated positive stop. The damping medium is automatic transmission fluid (ATF) that circulates through the pressure chamber with metering orifices (colored here in red). Applications include linear slides, swivel units, turntables, and portal systems. Noise reduction of 3 to 7 dB is possible with the inclusion of a special impact button.
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Slow down to speed up
...with ACE industrial shock absorbers. · Decelerate moving loads · Protect against wear and tear on machines · Increase throughput & reduce downtime 800-521-3320 | www.acecontrols.com 23435 Industrial Park Drive, Farmington Hills, MI 43885
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MOTION SYSTEM APPLICATIONS STOPPING WITH RUBBER BUFFERS, SPRINGS, DASHPOTS, OR CYLINDER CUSHIONS Production Rubber Raw material buffer
STOPPING WITH INDUSTRIAL SHOCK ABSORBERS Production Shock absorber Finished product
Finished product
Raw material Shock absorber
Scrap
Rubber buffer
Advantages of using industrial shock absorbers include safe and reliable production; longer service life than otherwise be possible; inexpensive construction; quiet and inexpensive operation; and less machine wear. In contrast, conventional dampers can sometimes incur loss of production and machine damage (for increased maintenance costs) as well as noisier and costlier operation — especially where conventional dampers are unsuitable for the automated design.
possible time — which in turn eliminates damaging force peaks and shock damage to machines and equipment. When plotted, the deceleration force-stroke curve is linear. Such smooth and gentle shock absorbing also serves to reduce noise generated by automated machinery.
HOW INDUSTRIAL SHOCK ABSORBERS WORK
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It’s clear that automated applications requiring the slowing of moving masses with constant damping force through the stroke benefit from the use of industrial shock absorbers. But how do they operate? In short, industrial shock absorbers work by converting kinetic energy into heat for controlled deceleration. In short, a piston acts as the interface between external moving masses requiring deceleration and the shock’s internal system of components. When an external mass impacts the piston, the latter retracts into the shock body. That in turn pressurizes hydraulic fluid such as automatic transmission fluid (ATF) inside … and forces this fluid to flow through a pressure chamber with metering orifices. The labyrinth of orifices serves to progressively restrict the fluid — causing it to rise in temperature. This heat is then expended to the shock outer body and outward to the surrounding environment. In industrial shock absorbers with some adjustability, a secondary pressure chamber with its own labyrinth of orifices fits around the primary pressure chamber — to create channels of variable restriction. Upon release of the mass from the piston, usually a return spring resets the piston to its extended position. In some cases, the return spring is internal to the shock absorber … or it’s externally located around the piston shaft.
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SHOCK MITIGATION & VIBRATION DAMPING
HOW TO SIZE INDUSTRIAL SHOCK ABSORBERS Let’s walk through an example of how a design engineer might select a shock absorber for an automated machine axis. Consider a mass horizontally driven from one side and riding on a frictionless surface such as a passive-roller conveyor: W1 = m · v 2 · 0.5 W2 = F · s W3 = W1 + W2 W4 = W3 · c vD = v me =
2 · W3 v D2
Where W1 = Kinetic energy per cycle, Nm m = Mass to be decelerated and me = Effective weight, both in kg v = Velocity at impact and vD = Impact velocity at shock absorber, both in m/sec s = Shock-absorber stroke, m W2 = Propelling force energy per cycle and W3 = Total energy per cycle, both in Nm W4 = Total energy per hour, Nm/hr — listed in capacity charts for room temperature (and reduced values at higher temperature ranges) n = Number of shock absorbers (in parallel) Note that final impact velocity can be 1.5 to
Now assume we have m = 36 kg and v = 1.5 m/sec ... and F = 400 N and c = 1,000 /hr with s = 0.025 m (chosen) That means we have W1 = 36 · 1.52 · 0.5 = 41 Nm W2 = 400 · 0.025 = 10 Nm W3 = 41 + 10 = 51 Nm W4 = 51 · 1,000 = 51,000 Nm/hr me = (2 · 51) / 1.52 = 100 kg
If m = 1,000 kg and v = 1.1 m/sec with M = 1,000 Nm and we choose s = 0.050 m — with L = 1.25 m, R = 0.8 m, and c = 100 /hr we get: W1 = 1,000 · 1.12 · 0.25 = 303 Nm W2 = (300 · 0.025) / 0.8 = 63 Nm W3 = 303 + 63 = 366 Nm W4 = 366 · 100 = 36,600 Nm/hr vD = (1.1 · 0.8) / 1.25 = 0.7 m/sec me = (2 · 366) / 0.72 = 1,494 kg
At this point, the engineer can choose a shock-absorber model based on manufacturer charts. Consider another example — that of a rotary index table with propelling torque. W1 = m · v 2 · 0.25 = 0.5 · I · ω2 W2 =
At this point, the engineer can choose a shock-absorber model based on manufacturer charts — accounting for side load angle (tan α = s/R) and shock-absorber capacity to handle such loading to ensure long and reliable operation. Where the assembly requires additional support due to side-load impact angles exceeding 3° (even to 25°) a side-load adaptor can protect the shock absorber’s rod bearings from increased wear that would otherwise reduce useful component life. Now consider a real-world iteration of an automated rotary-indexing table with
M·s R
W3 = W1+W2 W4 = W3 · c vD =
v·R =ω·R L
me =
2 · W3 v D2
EXAMPLE TWO: ROTARY INDEX TABLE v(ω)
EXAMPLE ONE: MASS WITH PROPELLING FORCE
s
F
Where ω = Angular velocity at impact, rad/sec M = Propelling torque, Nm R = Radius at which the shock absorber engages item of table, m L = ½ the indexing table total radius, m
twice that of average velocity — something for which engineers must account when calculating kinetic energy.
L
m
R
M
m
vD s
Shown here are the two example applications we use for our calculations. Note that the resultant values for weight and energy suggest use of an ACE Controls Model MC3325-2 self-compensating shock absorber for example one. Capacity charts from ACE Controls suggest the use of a Model MC4550-3 self-compensating shock absorber for example two.
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MOTION SYSTEM APPLICATIONS GENERAL FUNCTION OF THE PRESSURE CHAMBER v = 2 m/sec
*4 p = 400 bar
*3 p = 400 bar
v = 0.5 m/sec
v = 0 m/sec
*1 p = 400 bar
*2 p = 400 bar
*0 p = 0 bar
F = force (N) ... and p = internal pressure (bar) s = stroke (m) ... and t = deceleration time in sec v = velocity in m/sec
F/p
s/t
v
If a moving mass hits an industrial shock absorber, the piston puts the oil in the pressure chamber into motion. The oil presses through the metering orifices, which converts the discharged energy into heat. The metering orifices are arranged on the stroke so that mass motion is retarded with constant damping force. Hydraulic pressure is held constant throughout the entire braking process.
v = 1 m/sec
v = 1.5 m/sec
t
COMPARISON OF DAMPING TECHNOLOGIES Hydraulic dashpot STOPPING FORCE (N)
propelling torque — that of a large telescope’s optical system. Here, industrial shock absorbers boost the safety of swivel and braking functions. The moveable 15,000 kg telescope can sweep through two DOFs with a motor-driven turntable and twin wheel discs that ride on bearings for ±90° rotation from horizon to horizon. Industrial shock absorbers protect the telescope’s delicate subcomponents from shock from overshooting swivel limits … so if the telescope inadvertently overshoots its permissible swivel range, the shock absorbers safely damp the travel. In much the same way, industrial shock absorbers improve the positioning accuracy of a machine-loading design by serving as precision limit stops. Rodless pneumatic cylinders and twin gripper slides move independently at 2 to 2.5 m/sec. The shock absorbers work as brakes to stop a 25-kg mass up to 540 times per hour. The specific model employed for this task allows quick endposition adjustments … with higher travel speeds and shorter cycle sequences than comparable brake systems as well.
Pneumatic cylinder cushions Industrial shock absorbers
Springs Rubber buffers STOPPING STROKE Note the differences in damping as expressed by stopping force to stopping stroke. When slowing moving masses with constant force through a stroke, industrial shock absorbers excel.
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MOTION SYSTEM APPLICATIONS
Applications for
wave springs Wave springs are essential to an ever-growing lineup of consumer products … especially in electronics, safety, and automotive designs. They’re also in nearly all motion-control applications — including gearboxes, actuators, rotary unions, and clutches. Wave springs operate as load bearing devices. They suit applications with special space needs to take up play or compensate for dimensional variations within assemblies. They also work in designs that need loads to move either gradually or abruptly to reach a predetermined working height. A wave spring always applies load in an axial direction. Wave springs also apply consistent loads within a small tolerance range at different work heights. These capabilities let design engineers adjust the application to meet given requirements when needed. One wave spring is the single-turn. Versions with overlapping ends save axial space so there’s more space for travel. Here, the spring clings to the bore. In contrast, nested wave springs suit applications requiring higher forces to meet safety regulations, such as those in government or military applications. A nested-wave spring provides a higher load than a single-turn wave spring (a stamped wave washer) and uses the same radial space as a single-turn design. Use of multiple-turn wave springs can save 50% in axial space compared to a traditional coil spring. What’s more, these springs eliminate the risk of torsional movements during compression to work height.
Shown here are wave-spring application examples. From top to bottom, these include clutches, automotive vehicle mirrors, rolling doors, airbag inflators, water sprinklers, general airbag assemblies, night-vision lenses, and bayonet | courtesy Rotor Clip Company Inc. connectors.
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MOTION SYSTEM APPLICATIONS
Applications for
compression springs
Compression springs are typically used to resist linear compressing forces (such as a push force) where space is limited, where uniform bearing pressures are required, or to reduce buckling. These ubiquitous motion components are in automotive seats, pedals, transmission springs and windshield wipers. Buildingautomation applications for compression springs include industrial doors, fasteners, and dampers. In electric-distribution applications, they are indispensable for the function of contact switches and other electromechanical components. Medical uses for compression springs also abound — in simple mechanical equipment, such as beds, to those in advanced actuators for precision medical devices. In consumer devices, they are found in major appliances, lawn mowers, cell phones and so on. The most common compression spring, the straight metal coil spring, bends at the same diameter for its entire length, so has a cylindrical
This cord-free Dyson V8 Absolute vacuum cleaner includes a compression | Dyson spring in its assembly.
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| courtesy Lee Spring shape. Cone-shaped metal springs are distinct in that diameter changes gradually from a large end to a small end; in other words, they bend at a tighter radius at one end. Cone-shaped springs generally go into applications that need low solid height (the total height when compressed) and higher resistance to surging. Whether cylindrical or cone shaped, helical compression springs often go over a rod or fit inside a hole that controls the spring’s movement. Other configuration types include hourglass (concave), barrel (convex), and magazine (in which the wire coils into a rectangular helix). Most compression springs have squared and ground ends. Ground ends provide flat planes and stability under load travel. Squareness is a characteristic that influences how the axis force produced by the spring can be transferred to adjacent parts. Although open ends may be suitable in some applications, closed ends afford a greater degree of squareness. Squared and ground end compression springs are useful for applications that specify high-duty springs; unusually close tolerances on load or rate; minimized solid height; accurate seating and uniform bearing pressures; and minimized buckling. The key physical dimensions and operating characteristics of these springs include their outside diameter (OD), inside diameter, wire diameter, free length, solid height, and spring rate or stiffness. Free length is the overall length of a spring in the unloaded position. Solid height is the length of a compression spring under sufficient load to bring all coils into contact with adjacent coils. Spring rate is the change in load per unit deflection in pounds per inch (lb/ in.) or Newtons per millimeter (N/mm). The dimensions, along with the load and deflection requirements, determine the mechanical stresses in the spring. When the design loads a compression spring, the coiled wire is stressed in torsion and the stress is greatest at the wire surface. As the spring is deflected, the load varies, causing a range of operating stress. Stress and stress range affect the life of the spring. The higher the stress range, the lower the maximum stress must be to obtain comparable life. Relatively high stresses may be used when the stress range is low or if the spring is subjected to static loads only. The stress at solid height must be low enough to avoid permanent damage because springs are often compressed solid during installation.
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AD INDEX
MOTION SYSTEM APPLICATIONS ACE Controls............................................................. 79 Aerotech..................................................................... 73 AllMotion...................................................................... 2 Altra Industrial Motion................................................. 7 Applied Motion Products, Inc.................................... 23 AutomationDirect.....................................................IFC Bansbach Easylift....................................................... 83 Beckhoff Automation................................................. 37 Bishop-Wisecarver..................................................... 63 C-Flex Bearing Co., Inc.............................................. 41 Carlyle Johnson.......................................................... 30 CGI Inc....................................................................... 17 Chieftek Precision........................................................ 8 Del-tron...................................................................... 59 Diequa........................................................................ 55 Encoder Products Company...................................... 60 FAULHABER MICROMO.................................Cover, 67 Festo.......................................................................... 21 Fluid Line Products, Inc.............................................. 47 HEIDENHAIN CORPORATION.................................. 49 HIWIN................................................................. 9,11,13 igus............................................................................... 1 Intech......................................................................... 51 Lee Linear................................................................... 40 Lee Spring Company................................................. 87
LinMot USA Inc.......................................................... 15 Mach III Clutch Inc..................................................... 31 Maple Systems........................................................... 57 Master Bond............................................................... 12 maxon......................................................................... 65 Mitsubishi Electric Automation.................................. 25 mk North America, Inc............................................... 35 Moog Animatics......................................................... 70 MW Industries - ServoMeter......................................BC NSK Precision............................................................... 5 Pepperl+Fuchs........................................................... 19 Physik Instrumente L.P............................................... 77 Pyramid Incorporated................................................ 28 R+W America............................................................. 42 Rotor Clip Company, Inc............................................ 85 Ruland Manufacturing Co., Inc.................................. 39 Schneider Electric Motion USA.................................. 69 Serapid Inc................................................................. 29 SEW Eurodrive........................................................... 52 Sorbothane................................................................. 80 THK America, Inc......................................................IBC Tolomatic.................................................................... 27 Vlier............................................................................ 74 Yaskawa Electric America.......................................... 45 Zero-Max, Inc............................................................... 3
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