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POWER TRANSMISSION REFERENCE GUIDE
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POWER TRANSMISSION REF ERENCE GUI DE
EVs AS MOTION DESIGN KIN IT’S DEEPLY
satisfying when new (and burgeoning) industries adopt the electric motors we in the motion-control industry know so well — especially for
unmanned aerial vehicles (UAVs), autonomous ground vehicles (AGVs), passenger hybrid vehicles, and all-electric vehicles (EVs). Multiple decades in the motion industry have imparted in this author a reverence and irrational love for all types of electric motors (and their uses) whether induction, brushed, permanent magnet, stepper, direct drive, Lorenz force, or linear … and the list goes on. Of course, EVs constitute their own industry — as separate from motion control and discrete automation as process control employing electric motors in fans and pumps and the like. Even so, there is kinship between our industries because of this commonality in motors. Plus automotive uses for electric motors have proven an effective cross-pollinating source of innovation for various industrial automation applications. Consider fellows in motor appreciation at the National Electric Drag Racing Association (NEDRA) to inspire and capture imaginations like traditional American car culture once did. In fact, NEDRA’s mission is to boost public awareness of EV performance and (through safe dragrace competitions) spur new EV innovations. My own family from the Dubiel clan of Youngstown, Ohio won one such competition several years ago. Much like FIRST Robotics competitions, these events engage adults and young folks to consider the basics of engineering and get scrappy — in some cases using power-tool batteries, harvested golf-cart and dragster parts, and of course motors (typically permanent magnet) to build zippy electric speedsters for dead-silent speed. I’d argue that it’s through such tinkering that the highest understanding and reverence for technologies are born. Such programs will likely do little to reverse the much-covered trend of young folks (especially Millennials) relatively disinterested in car culture and getting drivers licenses … though postponed onset of driving is probably an overall win for roadway safety anyway. The pandemic didn’t help matters. The trend only emphasizes a practicality in young people who later welcome EVs even if these vehicles fail to satisfy old notions of what constitutes a cool car. More than 800,000 hybrid vehicles and 430,000 EVs were sold in the U.S. last year — representing nearly a hundredfold YoY increase and (for the first time) more than 10% of all new light-duty vehicle sales in the U.S. That’s a gratifying number of new electric motors out there.
LISA EITEL • @DW_LISAEITEL 4
DESIGN WORLD — MOTION
5 • 2022
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|
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CONTENTS V O L U M E
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N U M B E R
EDITORIAL STAFF CHAIN & BELT DRIVES ENCODERS GEARS & GEARMOTORS LINEAR ACTUATORS LINEAR GUIDE RAILS • SLIDES & WAYS MOTORS SHOCK & VIBRATION MITIGATION AD INDEX
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C H A I N & B E LT D R I V E S
POWER TRANSMISSION WITH BELT AND CHAIN DRIVES CHAIN DRIVES
actuate machinery axes and convey products with reliability. Now,
advances in precision and technology let designers use chains in more applications than ever. Remote installations benefit from long-life chain that requires no lubrication, for example. Chain-based setups vary, but the most common industrial designs use roller chain. This type of chain consists of five basic components: pin, bushing, roller, pin link plate and roller link plate. Manufacturers make and assemble each of these subcomponents to precise tolerances and heat treat them to optimize performance. More specifically, modern roller chains exhibit high wear resistance, fatigue strength and tensile strength. Roller-chain applications generally fall into two categories: drives and conveyors. Where chains operate as power-transmission components only (without doing double-duty as a conveyor) ASME/ANSI roller chain wraps around a driver sprocket (connected directly to the motor or reducer) and the driven sprocket (often connected to a machine’s conveyor head-shaft). This portion of the drive lets the designer build
motioncontroltips.com | designworldonline.com
a system that’s either faster or slower by simply changing the ratio of teeth between the drive and driven sprocket. The ratio of the teeth determines the reduction in rpm … so to reduce rpm, the driven sprocket must be larger than the driver sprocket. For example, if the driver sprocket has 15 teeth and the driven sprocket has 30 teeth, the ratio is 2:1, so the rpm is halved at the driven sprocket. The simplest way to select a roller chain is using horsepower charts. First, obtain the motor horsepower and rpm of the small driver sprocket. From this, determine the chain size and number of teeth for the driver sprocket. Where roller chain must drive applications that need long life without contamination, pick chain with self-lubricating subcomponents. Where roller chain must drive applications that need high precision, pick chain with precision roller bearings at each link connection.
COMMON POWER-TRANSMISSION CHAIN CHALLENGES Chain drives are often picked for their ability to withstand harsh environments. Some require clean operation without the contamination risk of lubrication. Others expose chain-driven machinery to weather, water, or chemicals. So, chain manufacturers offer several products to meet these challenges.
5 • 2022
DESIGN WORLD — MOTION
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LEADING THE MOVEMENT
C H A I N & B E LT D R I V E S DRIVE PULLEY Y
BELT-DRIVE EVOLUTION OF DESIGN AND PERFORMANCE
r1 X
r1
POINT MASS
DRIVEN PULLEY Consider roller chain: One critical area where roller chains need lubrication is the pin-bushing contact zone. Self-lubricating chains stay cleaner because the exterior of the chain is free of excess lube. These chains also attract less dust and particulates than regular chains. Such roller chains are useful where oil contamination is a concern, including paper-product or wood-processing industries. Nickel-plated chains offer another alternative for chain coatings, providing some protection for mildly corrosive environments. Stainless-steel chains offer superior corrosion resistance; however, designers must be aware that regular stainless steels cannot be hardened in the same manner as carbon steel. Therefore, the load carrying capacity of stainless steel is lower than carbon steel. Proper chain maintenance requires periodic inspection. All chains must be checked for damage, wear, and chemical attack on a regular basis. Another issue is wear elongation. Eventually roller chains wear so much that they necessitate replacement—typically at 1.5 to 2% (12.180 in./ft to 12.240 in./ft) elongation. Chains may work until they reach 3% elongation but are at increased risk for suboptimal performance. One final note: Besides chain strictly for power transmission, there are also conveyor chains that do double duty to accept a power input and move product horizontally, vertically, or even around curved radii. The most common conveyor chains are ASME-style (ANSI-style) attachment chains. These have pins or plates with tabs onto which parts or product-holding shoes can bolt. Common versions are singlemotioncontroltips.com | designworldonline.com
pitch attachment, double-pitch attachment, hollow-pin, curved-attachment, and plasticsleeve chain. The attachments let engineers put special fixtures or blocks onto the chain to serve specific conveyor functions. One subtype — accumulating chain conveyors — stop discrete products even while the chain is still moving without a lot of friction. Accumulating conveyors are suitable for applications (such as assembly lines) that have products ride through several stations. Belt drives in power-transmission and motion designs consist of rubber, engineered plastic, metal, or (most common) multi-material belts that wrap around drive pulleys — specially grooved or otherwise profiled wheels mounted on a shaft — in turn driven by electric motors. Powered by various motor types, these belt drives run axes transmitting fractional to 7,000 hp or more. Most belt drives in motion designs also wrap the belt around one or more idler pulleys that keep the belt taut and on track. While industrial belts are generally non-serviceable and can exhibit wear and vulnerability to oil as well as debris contamination, their benefits abound. The main reasons that engineers pick belt drives over other options is that modern varieties require little if no maintenance; they’re less expensive than chain drives; and they’re quiet and efficient, even up to 95% or more. In addition, the tensile members of today’s belts (cords embedded into the belt rubber that carry most of the belt load) are stronger than ever. Made of steel, polyester, aramid, fiberglass, or carbon fiber, these tensile cords render today’s belt drives thoroughly modern power-transmission devices. 5 • 2022
Flat belts are the original design for automated machinery — first applied in such designs during the first Industrial Revolution and before. In fact, flat belts were and remain especially important in pump and sawmill operations — and once reigned supreme in driving many axes off common steam-powered line drives through factories. Versions made of leather quickly gave way to rubber and neoprene — hastened by the innovations of the burgeoning automotive industry and new forms of independent pieces of machinery run off electric motors. Today, highly engineered flat belts still find myriad uses in conveying and material-handling applications. However, the faster axis speeds associated with many motor-powered designs necessitated belts with new geometry — so next came V belts having trapezoidal cross sections. Invented by John Gates in 1917, their easier tracking on pulleys and higher friction (which we’ll explain more on a moment) also allow high force transmission even at relatively low tension values. Reinforced cords embedded in belt backing — the tensioncarrying zone — was another innovation still core to modern belt variations. Combining flat and V-belt design elements are ribbed or poly-groove V belts — those with a cord-reinforced tension-bearing face and multiple trapezoidal profiles running the inner belt circumference. Drives based on ribbed V belts are exceptionally compact and necessitate lower tensions than flat belts. Other innovations came to include the introduction of toothed belts for synchronous chain-like operation; heat-resistant belt insulation layers; elasticized and other highly engineered working belt surfaces; and prestretched tensile cords of various materials. Recent years have seen convergence of specialty belt drive systems in mass-produced consumer and light industrial tools with the standard belt drives integrated into specialty machine designs. That’s because options have proliferated for belts with flat and round profiles as well as those with various V-shaped profiles and toothed belts for synchronous operation. The Association for Rubber Products Manufacturers (ARPM) originating from the Rubber Manufacturers Association (RMA) and the National Industrial Belting Association (NIBA) along with component suppliers dictate the details of how the DESIGN WORLD — MOTION
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POWER TRANSMISSION REF ERENCE GUI DE geometries and performance of these industrial belt drives are standardized and quantified. Many manufacturers describe belts and pulleys with five main geometries. Pitch diameter is the drive pulley’s diameter. Center distance is the distance between the two pulleys’ centers. Minimum wrap angle is a measure of how much the belt wraps around the smallest pulley. Belt length is how long the belt would be if cut and laid flat. Finally, in the case of toothed belts (also called synchronous belts) the pitch is the number of teeth per some length — so a 3-mm pitch means that the belt has one tooth every 3 mm, for example. Power ratings based on belt and pulley size (along with motor output) are adjusted for the belt-drive length and wrap diameters. Traditionally, charts of belt geometries and counts, horsepower ratings, and speed and force capabilities
assist design engineers in the specification process. Today, sizing and selection software tools abound to match required values to a machine axis’ geometry and torque (output force) and speed requirements. These also provide service-factor adjustments informed by the belt or other component supplier’s own historical experience with given industry and application type.
DIFFERENTIATING OTHER LESS COMMON BELT-DRIVE TYPES V belt and synchronous belt drives dominate motion power transmission and motion control (positioning and other precision). Following is a brief detailing of the other belt types used in industrial, robotic, and consumer designs. Modern flat belts are either endless (welded or otherwise closed into a hoop by the manufacturer) or open. Common on grinders, fans, grocery conveyors, and other power-
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transmission applications, drives based on flat belts rely on precisely set tension for maintaining the proper the friction coefficient between belt and drive pulley. Even today, many flat belts are made of natural materials as well as synthetic yarns featuring various filament structures. Flat belts made of polyurethane are common on the ends of conveyors consisting of roller arrays — to gang powered rollers (integrating a motor in its cylindrical body) to passive nonpowered rollers. Flat belts with polyester tension members excel where high tension (but little stretch) is required; coatings of PVC, polyurethane, and rubber enable high friction for use on highspeed axes running to 22,000 feet per minute. One specialty type of flat belt indispensable in settings subject to high temperatures and corrosive washdown (or other chemicals) is that made of thin stainless steel. These flat belts are precision welded closed to traverse just a few centimeters to dozens of meters — and often perforated to accept
the positive engagement of studded pulleys. Flat metal belts also exhibit no stretch or creep, so allow precision positioning of workpieces — and can protect workpieces sensitive to electrostatic charges with grounding. Round belts (sometimes called O-ring belts or O belts) have a circular cross section; they’re common on axes of consumergrade electronics with moving elements, office-grade printers and scanners, and light industrial equipment such as tabletop robotics with modest to moderate power-transmission requirements. Most round belts are extruded from neoprene, propylene, or cross-linked urethane (either reground or virgin) and then butt welded together into endless loops. Their elasticity makes them more forgiving of suboptimal installations, but at a sacrifice of power capability. Mating pulleys have semicircular grooves and diameters no less than sixfold the belt’s cross section. Texturized O-belts have lower coefficients of friction but are better able to resist abrasion and overheating.
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DESIGN WORLD — MOTION
5 • 2022
ENCODERS
POSITION MEASUREMENT IN MOTION SYSTEMS MEASURING
position, travel distance, and
speed are essential to motion control systems. There are numerous ways of
Their suitability for applications requiring high precision and durability make them a good choice for the semiconductor, electronics, medical, and defense industries.
measuring position including with encoders
INDUCTION-BASED ENCODERS
and other types of sensors. Typically, these
Another type of encoder/sensor is based on the principle of mutual induction. Some position measuring devices that rely on the principle of mutual induction include resolvers, linear variable differential transformers (LVDTs), and inductive encoders. Two of these technologies — resolvers and LVDTs — are based on the construction and operation of a transformer. In the case of an LVDT, voltage is applied to a primary winding and induced in two secondary windings — located on either side of the primary — via a ferromagnetic core. Distance is determined by the differential voltage output by the two secondary windings, and direction is determined by whether the output voltage is in phase or out of phase with the primary voltage. In the case of a resolver, a rotary transformer applies voltage to the primary winding, which is located on the rotor. Voltage is then induced in two secondary windings,
sensing devices are grouped according to a number of distinguishing features including operating principle, whether they are linear or rotary, or whether they output absolute or incremental data. There are three major categories of encoder based on the operating principle; optical, magnetic, or capacitive. Optical encoders were some of the first types of encoders and work using a light source for detection. Magneticbased encoders don’t use any optical means and can achieve resolutions down to a micron and compete with optical technology in a host of applications. They’re also more robust than optical technology, making magnetic encoders more common in harsh industrial environments. Capacitive encoders offer resolution comparable to optical devices, with the ruggedness of magnetic encoders.
oriented at 90 degrees as sine and cosine, on the stator. Position is determined by the ratio of the voltages in the secondary windings, and direction is determined by analyzing which secondary voltage (sine or cosine) is leading. Inductive encoders are similar to LVDTs and resolvers, but instead of using traditional windings, they use flat coils (sometimes referred to as “traces”) manufactured onto printed circuit boards. Rotary inductive encoders contain two main parts — a stator (also referred to as the sensor) and a rotor (also referred to as the target). The stator contains a transmitter coil and two (or sometimes more) receiver coils, printed onto the circuit board – or in some cases, directly onto the stator substrate. The receiver coils are printed so that they produce sine and cosine waves. In many designs, electronic circuitry for signal processing is also integrated onto the stator. The rotor, or target, is passive and is either made of ferromagnetic material or made of a substrate containing layers, or patterns, of conductive material such as copper. When voltage is applied to the transmitter coil on the stator, or sensor, an electromagnetic field is produced. As the rotor, or target, passes over the sensor, eddy currents are generated on the surface of the target. These eddy currents generate an opposing field, which reduces the flux density between the sensor and the target, causing a voltage to be generated at the receiver coils on the sensor. The amplitudes and phases of the receiver INDUCTIVE ENCODERS CAN BE INTEGRATED WITH PROFILED RAIL LINEAR GUIDES, SUCH AS THESE FROM BOSCH REXROTH, FOR ROBUST, HIGH-ACCURACY MEASURING OF THE LOAD POSITION.
motioncontroltips.com | designworldonline.com
5 • 2022
DESIGN WORLD — MOTION
15
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THE BASIC SETUP FOR A LASER INTERFEROMETER REQUIRES A BEAM SOURCE, MIRRORS, AND DETECTORS. (IMAGE COURTESY OF RENISHAW)
voltages change as the target moves, and the position of the target can be determined from these voltages. Inductive encoders are also available in linear versions. Here, the target is a linear scale with ferromagnetic (or electrically conducting) gratings, or stripes. The sensor (also referred to as the read head) contains the transmitter and receiver coils as well as electronics for signal processing. As the read head travels along the scale, the gratings of the scale cause variations in the voltages induced in the receiver coils, and these voltages indicate the sensor’s linear position. Inductive encoders provide absolute position information and have accuracies that fall between that of magnetic and optical technologies — without the strict mounting considerations of optical encoders. And they’re insensitive to nearly all forms of contamination or interference, including liquids,
dirt and dust, magnetic fields, EMI, and even severe vibrations. For rotary measuring applications, the printed circuit board construction of inductive encoders gives them a much smaller form factor and more design flexibility than their resolver counterparts.
INTERFEROMETRIC LASER ENCODERS Optical encoders such as glass scales are often used for linear position measurements that require micronlevel resolution. But applications in industries such as semiconductor and aerospace — especially those that involve optics — require measuring capabilities in the nanometer and even picometer ranges, beyond the resolution of most scalebased optical encoders. For these applications, direct, non-contact measuring technologies, such as interferometric laser encoders, can provide resolutions down to the picometer range.
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ENCODERS Interferometric laser encoders — also referred to as laser interferometer encoders or laser displacement sensors — interpret the interference of two laser beams to determine the position or motion of a target object. The operating principle relies on a laser source whose beam is split into two beams that are identical but directed along different paths. One beam is sent to a reference mirror while the other is sent to a mirror on the object being measured (the measurand). The two beams are then reflected back by their respective mirrors and combine before reaching a detector. However, the differing travel distances of the two beams puts them out of phase, so when they’re recombined, they create an interference pattern. The interference can be constructive, where the combined wavelengths produce a bright fringe, or destructive, where the combined wavelengths produce a dark fringe. This variation in the intensity of the combined light is cyclic, and one cycle of variation occurs every time the measurement beam (and, therefore, the measurand) is displaced by one-half of the laser’s wavelength. The detector uses this variation in intensity and its relationship to the laser’s wavelength to determine the amount of movement of the measurand. The resolution and repeatability of a laser interferometer encoder are directly related to the wavelength of the laser beam and the stability of the wavelength. Because wavelength stability is affected by environmental conditions such as changes in temperature, pressure, or humidity (all of which affect the refractive index of air), laser interferometer encoders include environmental compensation electronics to ensure a consistent wavelength, even under changing environmental conditions. In addition to high accuracy and resolution, one of the primary benefits of a laser interferometer encoder is that the measurement mirror can be mounted directly at the point of interest, reducing or eliminating Abbé error due to offset between the measurement location and the point of interest. And although laser interferometry requires numerous components — a beam source, splitters, mirrors, and detectors — laser interferometer encoders typically use just two or three components — a laser source and one or two detectors, with functions such as environmental compensation and beam steering integrated into these main components. Although applications that require position measurements at the nanometer and sub-nanometer level typically have small travel distances, such as linear motor or piezo stages used in semiconductor lithography, interferometric laser encoders can also provide high-resolution measurements over long travel distances. Typical measurement capabilities are up to several meters, and some laser interferometer encoders can measure lengths up to 30 or 40 meters. The ability to measure positions in the sub-micron range over long distances is especially useful for gantry systems, such as CNC and CMM (coordinate measuring machines) applications, where high resolution feedback is required over several meters and multiple axes.
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INDUCTIVE ENCODERS, SUCH AS THESE INCODERS FROM ZETTLEX, ARE SIMILAR TO RESOLVERS AND LVDTs, BUT IN A MORE COMPACT FORMAT.
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PERFORMANCE CURVES TO SPECIFY SUITABLE GEARMOTORS ONE TOOL
central to gearmotor selection is the
performance curve. Published in data sheets and sometimes called speed-torque curves, these plot gearmotor torque against speed and in many cases efficiency as well. Motor manufacturers calculate the values underpinning performance curves to make the sizing and specifying process easier for design engineers. In fact, performance-curve values are fully verified by motor manufacturers through extensive testing to prevent failures from miscalculations or improper component matching.
One caveat: Manufacturers use a wide array of techniques to quantify gearmotor capabilities beyond just torque and speed. That’s why in some instances, only generalized empirical data is available for a gearmotor’s thermal characteristics, full-load torque, gearbox yield strength, and output capabilities for intermittent duty cycles. So many OEMs opt to test samples of a gearmotor before mass adoption. Extreme motor heat, unusual noises, and other obvious signs of motor stress should prompt motor reselection — and in many cases, additional help from the motor manufacturer. Summary of the specification process: To select a gearmotor for an application, start by determining the axis’ required torque. Next determine whether
the duty cycle for the axis is intermittent or if the axis will need to run continuously. Note that when the periods of runtime for a gearmotor axis are sufficiently long and close together, the duty cycle qualifies as continuous duty. Though specific applications require engineering support from the gearmotor supplier, continuous duty is defined by industry as that which runs 8 to 10 hours a day … intermittent duty run several minutes per hour … and occasional duty runs for two minutes or less every cycle for 15 to 30 minutes total per day. Next define the axis speed ranges and refer to gearmotor performance curves to identify viable models and sizes. Of course, the specification process doesn’t end there. Design engineers
IMAGE COURTESY PHUCHIT • DREAMSTIME
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essentially try to drive the motor … and the motor will struggle to get the load to its target position, speed, or torque. That in turn will prompt the motor to draw higher current … which decreases efficiency and increases wear on the motor and electrical components. On the other hand, if the motor’s inertia significantly exceeds the load’s inertia, it’s likely that the motor is oversized. That in turn has negative implications throughout the system — including higher initial cost, higher operating cost, larger footprint, and the need to oversize other components such as mounting hardware, couplings, and cables. If the inertia ratio is too high, load inertia far exceeds motor inertia and will cause problems with positioning accuracy, settling time, or control of velocity or torque. If this is the situation at hand, load inertia that is seen by (reflected to) the motor can be decreased by adding a gearset or gearbox between the motor and the load. Adding a gearset or a gearbox to a motor-driven system reduces the load inertia by the inverse square of the gear ratio … meaning that even a relatively low gear ratio can have a significant effect on the inertia ratio. Note that the inertia of the gearset or
NOTE ON MOTOR INERTIA CONSIDERATIONS Any system using a motor to drive a load with precise positioning, velocity, or torque requires consideration of inertia. That’s because the ratio of load inertia to motor inertia significantly impacts a motor’s ability to control attached loads effectively and efficiently. That’s especially true during the acceleration and deceleration portions of the motion profile. In this context, the inertia to which we’re referring is mass moment of inertia, sometimes called rotational inertia — an object’s resistance to change in rotational speed. An object’s mass moment of inertia depends on its mass and geometry … usually the radius defined by the object’s center of mass and the point around which the object rotates. If the load’s inertia significantly exceeds the motor’s inertia, that load will
gearbox is added to the load inertia, but its effect is typically small compared to the reduction provided by the gear ratio. In addition to optimizing the loadmotor inertia ratio, gearboxes are often used in motion control applications to increase the torque delivered to the load from the motor, but they also decrease the rotational speed delivered to the driven component from the motor, by an amount equal to the gear ratio. Therefore, gearboxes are often called gear reducers or speed reducers. In other words, if a motor running at 1,200 rpm is driving a load through a 3:1 gearbox, the rotational speed delivered to the load will be 1,200 ÷ 3 = 400 rpm. This reduction in speed can enable the system to operate at a more favorable location on the motor’s speed-torque curve. Although it is possible to use a gearbox or gearset that is configured to reduce torque (and increase speed) in motion control applications, a more typical solution here is to choose a smaller motor.
SPEED-TORQUE CURVES FOR THREE GEARMOTOR TYPES PERMANENT-MAGNET SERVO MOTOR
INDUCTION (SQUIRREL-CAGE) MOTOR
AC SYNCHRONOUS MOTOR
Breakdown torque
Locked-rotor torque
Peak rated torque
TORQUE
Pullup torque Continuous torque
Va
ria
ble
Maximum motor torque
Peak stall torque
Motor curr ent
to
r
qu
o el
ad
Continuous stall torque Continuous rated torque
Peak torque Intermittent duty (to a few seconds) Continuo
us torqu
e
IEC 60034-1 Type S3 intermittent periodic duty Torque (with forced ventilation) Torque rque s to (self-ventilated motor) uou n i t Con IEC 60034-1 Type S1 continuous running duty
Continuous duty Maximum speed (full voltage • no load)
No-load speed
SPEED (RPM)
GEARMOTOR CURVES UNIFY INFORMATION (INCLUDING THAT ABOUT SPEED, TORQUE AND EFFICIENCY) TO SUMMARIZE THE PERFORMANCE OF THE MOTOR-GEARSET COMBINATION. IF AN OEM OR END USER BUYS A COMPLETE GEARMOTOR ASSEMBLY FROM A MANUFACTURER, THE LATTER SUPPLIES ITS PERFORMANCE CURVE.
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LINEAR ACTUATORS – FOCUS ON D IRECT-DRIVE MOTORS DIRECT-DRIVE LINEAR ACTUATORS, SUCH AS THE ACT140DL LINEAR SERVOMOTOR DRIVEN ACTUATOR FROM AEROTECH, ARE FASTER AND MORE ACCURATE THAN BALL-SCREW OR BELT-DRIVE ACTUATORS, AND DON’T REQUIRE COSTLY AND TIME-CONSUMING MAINTENANCE.
THERE ARE
many types of linear actuators – from
traditional screw-based actuators, to belt and pulley or chain-based, to actuators that rely on fluid power like pneumatic and hydraulic actuators. Another kind of actuator is electricbased. These include electric motors that convert rotary motion into linear motion, one example of which is a direct-drive motor. A direct drive motor is any motor — rotary or linear — in which the load is connected directly to the motor, without mechanical transmission elements such as gearboxes or belt and pulley systems. In other words, the motor directly drives the load.
LINEAR DIRECT-DRIVE MOTOR VARIATIONS
control but produce less force than other designs. Another construction variation for ironless motors uses two magnet tracks facing each other (sometimes referred to as U-channel or air core linear motors). The ironless secondary part, or forcer, rides between the magnet tracks. These motors have no cogging and can produce very high acceleration and deceleration rates. Flat iron core linear motors can be either slotted or slotless, with slotted iron core designs being the more common variation. The secondary part of a slotted iron core linear motor consists of a back iron plate and iron teeth, or laminations, around which the coils are wound. They have the highest force capabilities, but they can experience significant cogging. Slotless designs are considered to be a hybrid between ironless and traditional slotted iron core designs, because they have coils that are wound without iron lamination but are mounted to a back iron plate. The secondary part is often contained in an aluminum housing. These motors have less cogging and lower inertia than slotted iron core designs, but they also have lower force capability.
Linear direct-drive motors are often simply referred to as “linear motors.” These include ironless and iron core versions, depending on the construction of the primary part (the part that contains the windings). Ironless versions have a primary made of windings embedded in an epoxy resin, whereas iron core versions have windings that are mounted in an iron lamination stack. Another distinguishing feature of a linear direct drive motor is whether it has a flat or a tubular construction.
FLAT LINEAR DIRECT-DRIVE MOTORS Ironless flat linear motors have a flat magnet (secondary part), with a primary part, or forcer, consisting of coils mounted to an aluminum plate. These motors have excellent velocity
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FLAT LINEAR DIRECT-DRIVE MOTORS CAN HAVE AN IRONLESS (TOP), SLOTTED IRON CORE (MIDDLE), OR SLOTLESS IRON CORE (BOTTOM) CONSTRUCTION. (IMAGE COURTESY PARKER HANNIFIN CORPORATION)
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TUBULAR LINEAR DIRECT-DRIVE MOTORS Another construction variation of the direct drive linear motor is to contain the magnets within a cylindrical tube and house the windings in a forcer, or thrust block, that surrounds the tube. Like their flat counterparts, tubular linear motors can be constructed with or without iron in the secondary part (i.e. iron core or ironless). The primary benefit of a tubular linear motor is that its symmetrical designs allows all the magnetic flux to be used for generating thrust force.
DIRECT-DRIVE MOTOR BENEFITS AND APPLICATIONS Regardless of its design — rotary or linear, flat or tubular, iron core or ironless — a direct- drive motor has the benefit of eliminating mechanical components that can introduce backlash or compliance and degrade positioning accuracy and repeatability. The elimination of mechanical connections also reduces load inertia and allows more dynamic moves — i.e. higher acceleration and deceleration rates with heavier loads — with less overshoot and oscillation. Direct-drive motors also have lower noise production than conventional motors, which is important for noise-sensitive applications, like those in the medical and laboratory industries. Without additional transmission elements, direct-drive motors tend to be more compact than traditional motors, making them easier to integrate into machines and systems with tight spaces. And with fewer mechanical components (often, the only wear components are linear guides), maintenance is reduced and mean time between failures (MTBF) is increased. Rotary direct-drive motors are used to drive goniometers, gimbals, rotary tables, and SCARA and 6-axis robot arms. Many designs have a center bore, which allows electrical cables and pneumatic lines to be routed through the center of the motor. Linear versions are used in numerous automation applications, including packaging machines that require rapid strokes on a continuous basis, machine tools that require extreme positioning accuracy and high load carrying capability, and semiconductor manufacturing equipment that requires ultrasmooth and precise motion. motioncontroltips.com
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LINEAR BEARINGS FOR HIGH-PRECISION MOTION DESIGNS THE BASIC
distinction between standard and miniature
profiled-rail linear guides is the width of the guide rail: Profiled rails with a width of 15 mm or less — and the carriages that fit on them — are generally considered miniature by bearing manufacturers. However, some manufacturers also produce 15-mm rail guides in standard versions, as we’ll explain.
NOTICE THE MINIATURE LINEAR GUIDES ON THIS SCANNING ELECTRON MICROSCOPE (SEM) LASER STAGE. (IMAGE COURTESY WAIHENG • DREAMSTIME)
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In addition to the width of the rail, there are other key differences between standard and miniature profiled rail guides and carriages of which designers and users should be aware when specifying linear motion components. Ball and raceway construction: First is the basic construction of the carriage (also called the runner block). Most standard profiled rail carriages use four rows of balls — two on each side of the carriage. But because of their compact dimensions, miniature versions use only two rows of balls — one row on each side of the carriage. This means that miniature profiled rail carriages have relatively lower load and moment capacities than would be expected of four-row carriages. To help counter the loss of two ball rows, miniature guides typically use Gothic arch raceway geometry, which provides four points of contact between the balls and the raceway. This ball-raceway geometry gives the carriage the same load capacity in all four directions — downward, lift-off, and side loading — and provides relatively high moment load capacities. Note that not all miniature profiled rails incorporate retainers to secure the balls in the carriage. Keep this in mind when assembling and disassembling miniature rail and carriage assemblies. If there’s no retainer, the balls will fall out of the carriage when it’s removed from the rail. Materials: Another difference between standard and miniature profiled rail guides concerns materials. Where standard profiled rail guides and carriages are made primarily from steel, miniature versions are offered as motioncontroltips.com
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LINEAR GUI DE RAI LS • SLI D E S & W AY S standard in stainless or corrosion-resistant steel — for both the guide rail and carriage and in some cases, even the balls and recirculation pieces. This is especially beneficial in applications where corrosion-resistance is necessary — involving chemicals, occasional exposure to water or high humidity, or even industry-specific requirements for stainless-steel materials, such as those found in the food and packaging and medical industries. Sealing: Manufacturers also take different approaches to sealing for standard and miniature profiled rail guides and carriages. For standard versions, manufacturers often focus on ways to keep even the fi nest dust and fl uid mist out of the carriage and to retain lubrication as efficiently as possible. But miniature versions are often used in applications in the electronics, semiconductor, and medical industries, where the environment is relatively clean or may even be a certified cleanroom. Therefore, miniature profiled rail carriages are typically offered with several sealing options, including the option to omit seals altogether. For those applications that do require protection against contamination and loss of lubrication, some manufacturers now offer miniature rail carriages with end cap seals that incorporate a lubrication reservoir, to reduce maintenance intervals and ensure sufficient sealing for contaminated environments.
SOME SERIES OF MINIATURE PROFILED RAILS HAVE RAIL WIDTHS OF JUST A FEW MILLIMETERS OR SMALLER AND TWO ROWS OF RECIRCULATING BALLS. THIS ONE ALSO HAS ENCODER FEEDBACK.
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“
MINIATURE RAIL GUIDES USE GOTHIC ARCH GEOMETRY FOR FOUR-POINT CONTACT BETWEEN THE BALLS AND RACEWAYS.
Gothic-arch profiles have four points of contact.
“
Preload and accuracy class: Miniature rail carriages also have limited preload and accuracy class options. First, because of the small size of the balls used in miniature versions, preload is typically limited to 1 to 2% of the dynamic load capacity (as opposed to 8 or even 13% for standard versions) with clearance (slight play between the carriage and the rail) or light preload being the most common options. Similarly, miniature profiled rails are typically offered in normal and high accuracy classes, with some manufacturers offering “precision” as the highest accuracy class — unlike standard profiled rail assemblies, which are also offered in super-precision and ultraprecision accuracy classes. In fact, another option for miniature and nanopositioning designs is air bearings. Bearings are often assumed to be mechanical rolling or sliding elements, but both linear and rotary bearings can also use a thin film of pressurized air to support load. With no mechanical elements to generate friction or heat, air bearings are ideal for applications that require extremely high precision and stiffness. Pressure generation and air delivery: Depending on how pressure is generated, air bearings are classified as either hydrodynamic or hydrostatic.
corrosion on the bearing surfaces. When the quality of supplied air is a concern and corrosion would be detrimental, another gas (typically nitrogen) can be used in place of compressed air. This is often the solution for cleanroom environments. Preload on an air bearing: Adding
MINIATURE CARRIAGES (JUST LIKE THOSE OF STANDARD LINEAR GUIDES) COME IN SHORT AND LONG VERSIONS … WITH WIDE VERSIONS SOMETIME ABLE TO ELIMINATE THE NEED FOR TWO PARALLEL RAILS IN SOME OVERHUNG LOADING SITUATIONS. THE ABILITY TO SUPPORT LOADS WITH A SINGLE RAIL IS KEY IN APPLICATIONS WHERE SPACE IS AT A PREMIUM.
Hydrodynamic air bearings depend on relative motion between the bearing surfaces to generate pressurized air. In contrast, a hydrostatic air bearing relies on an external supply to deliver pressurized air — or other gas. Because they can maintain an air gap even when there is no relative motion between the bearing surfaces, virtually all air bearings used in industrial applications are hydrostatic. The gaseous medium used for air bearings is typically compressed air, which is readily available in most industrial plants and processes. However, any moisture in the air supply can develop into condensation as the air transitions from high pressure to atmospheric pressure, resulting in
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preload to an air bearing increases stiffness and helps maintain a constant air gap. As air bearings are loaded, the air gap gets smaller and the pressure in the air film rises — both of which contribute to higher stiffness. There are four common methods for preloading air bearings: by adding weight, through magnetic attraction, through vacuum, and by using two opposed air bearings. The simplest method for creating preload in an air bearing is to use a weight that is heavier than the load to be applied. This makes the air gap smaller, which increases the system stiffness. The drawback of the weight method of preloading is just that — it adds mass to the system. It is also suitable only for
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horizontal applications — not inclined or vertical orientations. Magnetic attraction between the moving and stationary parts can also induce preload. But most air bearings are made of non-magnetic material, so this method requires that that a magnetic material be added to both bearing surfaces. A third way to induce preload is to add a vacuum to the bearing surface, which creates a pressure differential and causes the external atmospheric pressure to exert force on the bearing. However, this method is only useful if a vacuum source is available and practical to install. The most common preloading method is to configure two air bearings opposite each other. Because stiffness is additive, an assembly preloaded in this manner will have double the stiffness of a single bearing. Another benefit is that the errors on either bearing will be averaged — resulting in much higher accuracy than other preload methods can achieve. The drawback to using opposing bearings is that the load capacity will be reduced by approximately half. This method also requires additional space and doubles the mass of the bearing components.
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DESIGN WORLD ONLINE EVENTS AND WEBINARS Check out the DESIGN WORLD WEBINAR SERIES where manufacturers share atheir experiences and expertise to help design engineers better understand technology, product related issues and challenges.
WEBINAR SERIES
FOR UPCOMING AND ON-DEMAND WEBINARS, GO TO: www.designworldonline.com/design-world-online-events-and-webinars
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SERVO MOTORS OF THE DC VARIETY MECHANICAL
power transmission
depends in large measure on electric motors. Whether ac or dc motors, brushed or brushless, stepper or servo, each has unique properties and characteristics best suited for particular applications. Take servo motors, for example. They’re used in applications where precise control of position, speed, or torque is required. But many different types of motors can be considered servo motors — the defining feature of a servo motor is that it incorporates or reads feedback in a closedloop system. In fact, although many servo applications use synchronous ac motors, dc motors can also be used in servo systems. Synchronous ac motors are typically brushless, with the exception being universal motors, which are mechanically commutated with brushes and can run on either an ac or dc power supply. Likewise, the dc motors used in servo systems are most commonly brushless types, typically referred to as BLDC motors. Recall that brushless dc motors use permanent magnets on the rotor and coils in the stator to produce rotation and torque. This configuration is similar to a synchronous ac motor, but a key difference between BLDC motors and synchronous ac motors is in how the stator coils are wound. In a synchronous ac motor, the coils are wound sinusoidally and commutation is a continuous, sinusoidal waveform. This gives synchronous ac motors smooth performance. BLDC motors, on the other hand, have trapezoidally wound stator coils
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and commutation that takes place in six steps (every 60 degrees), which can lead to torque ripple.
BLDC MOTOR CONSTRUCTION VARIATIONS Brushless dc motors are typically constructed with a stator made from slotted steel laminations and copper windings inserted into the slots. Slotted designs can be constructed with the rotor at the center of the motor and the stator surrounding the rotor (sometimes referred to as an “inrunner,” or internal rotor, design). This reduces the motor’s inertia and allows for dynamic performance. Alternatively, slotted BLDC motors can be constructed with the slotted stator at the center of the motor and the rotor magnets surrounding the stator (sometimes referred to as an “outrunner,” or external rotor, design). This allows the motor to produce high torque and to be constructed with a short overall length (referred to as a “flat” design), but at the
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AN EXAMPLE OF A SLOTTED BRUSHLESS MOTOR (LEFT) AND A SLOTLESS MOTOR (RIGHT).
expense of reduced dynamics due to higher rotor inertia. Whether constructed with an internal or external rotor, slotted BLDC motors suffer from cogging torque due to the permanent magnets in the rotor attempting to line up with the slots of the stator. The primary effect of cogging torque is that it causes motor rotation to be jerky, especially at low motor speeds. A newer permutation of the BLDC motor is the slotless design. This does away with the slotted steel laminations and instead uses a stator constructed of steel rings stacked together, with the windings encapsulated in an epoxy resin. The winding is placed in the air gap between the stator lamination and the rotor (which resides in the center of the motor). The slotless design eliminates cogging torque, reduces audible noise,
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Meeting Customer Needs with Diverse Product Categories and Customized Products
Linear Piezo Motor
DC Brushless Servo Motor
Canon Precision proprietary technology and internal production systems provide our partners with micro-motor design flexibility, quality control and rapid delivery. Canon Precision motors can also be equipped with optional gear units and encoders and can be optimized to meet your size, speed, gear ratio and reliability requirements. CANON U.S.A., INC. Motion Control Products 3300 North 1st Street • San Jose, CA 95134 TEL: 1-408-468-2320 • Email: motors@cusa.canon.com www.usa.canon.com/ Canon is registered trademark of Canon Inc. in the United States, and may also be registered trademarks or trademarks in other countries. All other referenced product names and marks are trademarks of their respective owners. Specifications and availability subject to change. Not responsible for typographical errors. ©2021 Canon U.S.A., Inc. All rights reserved.
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and reduces inductance, so acceleration and dynamic response are improved over slotted designs. BLDC motors are often used in servo applications that require high efficiency, high reliability, and good torque density (torque production for a given size), but without the magnitude of torque production that can be provided by larger, synchronous ac motors. Common applications for BLDC servo motors include robot joints, medical devices, and packaging equipment. Brushless dc motors are also ideal for battery-powered equipment and for applications that require direct integration of the motor into the mechanical design, thanks to their numerous design options and the myriad ways they can be customized.
BRUSHED DC MOTORS IN SERVO SYSTEMS The idea of brushed servo motors may seem a bit counterintuitive—we tend to think of servo motors as high-performance devices used in highly dynamic applications, while brushed dc motors are low-cost solutions for mass-produced consumer devices. And, to a large extent, this is correct. But remember that “servo motor” is a fairly broad term that applies to any motor used in a closed-loop system with feedback. In other words, whether a motor can be classified as a “servo motor” has less to do with the motor type and construction than it does with the type of system the motor is used in. Brushed dc motors are also referred to
BRUSHLESS DC SERVO MOTORS ARE COMMONLY AVAILABLE AS INTEGRATED PROGRAMMABLE UNITS COMBINING THE MOTOR WITH A CONTROLLER AND DRIVE, SUCH AS THIS IDEA MOTOR SERIES FROM AMETEK HAYDON KERK PITTMAN.
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MINI BRUSHLESS DC MOTORS, SUCH AS THE ULTRA EC 16ECS MOTOR FROM PORTESCAP, ARE SUITED FOR MANY MEDICAL APPLICATIONS WHERE SPACE IS LIMITED. THESE MOTORS ARE 16-MM WIDE WITH LENGTHS UP TO 52 MM AND ARE CAPABLE OF SPEEDS UP TO 75,000 RPM.
as permanent magnet dc (PMDC) motors, because the stator incorporates permanent magnets on its inner diameter. The rotor (also referred to as the armature) consists of a slotted iron core with windings that are attached to a commutator. PMDC motors are mechanically commutated, with brushes that carry current to the windings, in contrast to BLDC motors which are commutated by electronic means rather than by a commutator and brushes. While the mechanical commutation of brushed dc motors is often seen as a drawback—the brushes are wear parts which must be maintained and replaced— this design is typically less expensive than that of a BLDC motor. And in terms of performance, brushed servo motors have smooth speed output (especially at low speeds), a wide speed range, and good speed control, with the added benefit of using regenerated energy to brake the motor. They can also produce high torque for startup or acceleration. Compared to other dc motors, brush types are generally smaller and more energy efficient, because there is no field coil. There are two important characteristics of brushed servo motors that engineers and designers need to keep in mind. First, the rotor is located inside the motor, and the thermal path for heat dissipation from the rotor is not especially efficient, so pay close attention to the thermal characteristics of the motor. Second, the permanent magnets on the stator can be partially demagnetized if excessive current is applied.
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Manufacturers of PMDC motors— i.e. brushed servo motors—often cite automotive applications such as power seats and windows or windshield wipers, as their main area of use, due to low cost and a simple control method. These characteristics also make them a common choice for household appliances and small consumer electrics. In industrial applications, PMDC motors are commonly used for equipment where torque is only, or primarily, required during acceleration and deceleration.
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Unique system solutions for motor & drive technology. The facts at a glance: – Highly diverse motor range for virtually all drive applications: – AC or DC motors – Internal or external rotor – Mechanical or electronic commutation – EC motor with integrated or external operating electronics – System solutions including transmission, brake and encoder – Drive units capable of communication with bus interface – Customized motor solutions, motor parts sets and drive assemblies – Motors for automotive applications: Power steering drives, drives for clutch actuators and various pumps in the areas of transmission lubrication and exhaust aftertreatment and more
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SHOCK, VIBRATION CONTROL AND DAMPING IN MOTION SYSTEMS VIBRATION
in industrial machinery usually comes
SHOCK AND VIBRATION DAMPING
from inherent imbalances within motors,
Most shock absorbers deliver their damping characteristics by using hydraulic fluids. The fluid is pushed by a piston and rod through small orifice holes to create damping, and this action compresses some type of gas. This in turn creates a spring force to return the rod back to its starting position when the load is removed. Shock absorbers and dampers are generally made of highstrength steel to handle the pressures from the internal hydraulic forces. Aluminum, stainless steel, or thermoplastic may also be used. These other materials provide varying balance between strength and corrosion resistance. Additionally, the rods can be treated with chrome to provide corrosion resistance and increase surface hardness. Nitride will increase the hardness by introducing nitrogen into the outer surface of the rod. There are also a number of important shock absorber features to consider. Adjustable shock absorbers allow the stiffness of the response to be monitored and fine-tuned. This is usually accomplished by adding or removing hydro/pneumatic medium from the shock absorber by way of a valve. Locking capability allows the position of the rod to be fixed at a given position. The general criteria when selecting a shock absorber are the dampening method and damping direction. The dampening method can be elastomeric, pneumatic or hydraulic. The damping direction can be either in compression or extension.
gearboxes, and other rotating equipment. Additionally, when highspeed, heavy-duty industrial automation systems must decelerate and stop, they release kinetic energy, which induces long-term vibration and fatigue and sudden shock in a system. Smooth deceleration of a system should be done with shock and vibration attenuation components to prevent damage to the load and the machine. Based on the type of inputs present in the application, vibration and shock attenuation components can include shock absorbers, linear dampers, wire rope or spring isolators, elastomeric isolators, air springs, or structural damping treatments. These devices help manufacturers reduce equipment downtime and costly cycle time limitations. These products work in a broad range of applications — from the rate control mechanisms that slow the motion of overhead luggage bins or seat recline on commercial aircraft, to the isolators that keep GPS from losing signal or becoming damaged on farm and construction equipment as they harvest crops or pave roadways.
SHOCK ABSORBERS FROM ACE CONTROLS FEATURE INNOVATIONS SUCH AS DIAPHRAGM ACCUMULATORS, LONG LIFE SEALS, AND HARDENED INNER PRESSURE CHAMBERS FOR LONG SERVICE LIFE.
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S H O C K A N D V I B R AT I O N C O N TROL When choosing a shock absorber, one must specify the stroke length, compressed length, extended length, cylinder diameter, and rod diameter. The stroke length is the distance between the compressed and extended length. The cylinder diameter is an important factor in determining whether the cylinder will fit into the desired housing, or what housing to use. The rod diameter is used to determine how the shock absorber will be affixed to a given component. The performance of the shock absorber can be determined from the maximum force, energy per cycle and maximum cycles per minute. The maximum force, also called the P1 force, is the greatest rated force that the shock absorber can supply. The energy per cycle is the amount of energy that the component can absorb, and will also depend on the stroke length. The maximum cycles per minute is a measure of how quickly the shock absorber can return to its unstretched length. Elastomeric seals prevent the fluid from leaking out of the cylinder, and special plating and coatings keep the units protected from harsh operating environments. Recent and ongoing developments in sealing technologies and in the internal designs of shock absorbers and dampers have allowed for longer service life and more compact designs. Miniaturization is a growing trend in these devices, as systems require tighter tolerances and smaller machine footprints. In machine automation and robotics, motion stabilization requires the use of hydraulic dampers, particularly micro-hydraulic designs. A two-part system is used for the upper piston rod seal in one-tube shock absorbers. An acrylonitrile butadiene
rubber (NBR) ring, connected to the housing, keeps a dynamic seal made of fluoro rubber in place. Three seal lips seal the piston rod. The retaining ring applies the required pressure on the lips, continually pushing against the seal’s outer edge and compressing it in the process. An alternative sealing concept for onetube shock absorbers from Freudenberg Sealing Technologies — a wedge seal — leads to a highly simplified seal structure since it makes the retaining ring used in conventional two-part systems unnecessary. The design makes logistics and installation easier during the absorber manufacturing process because fewer components need to be stocked, assembled and joined together.
VIBRATION ISOLATION Vibration-isolation products rely generally on mechanical designs to achieve their isolation characteristics. A spring function provides support for the mounted equipment, while decoupling it from the vibration source. Friction and elastomeric material properties give the isolators their damping characteristics. Isolators can be made from a variety of materials. Wire rope and spring isolators can be made from carbon steel, stainless steel or aluminum. Elastomeric isolators generally have metallic components that function as mounting brackets, separated by an elastomeric material that provides the stiffness and damping desired. Common elastomeric compounds include natural rubber, neoprene, and silicone but many compounds and blends deliver various characteristics specific to satisfy different applications.
INDUSTRIAL GAS SPRINGS ARE THE SMART WAY TO LIFT AND LOWER • Enhance operator and machine control through the entire range of motion without excess strength • Perfect support of muscle power with forces from 2 to 2,923 lbs. • Stainless steel options for wash down and sterile environments • A variety of accessories allows for universal application
SORBOTHANE LEVELING MOUNTS FEATURE UNIQUE VIBRATION DAMPING PROPERTIES THAT ALLOW IT TO BEHAVE LIKE A FLUID BUT RETAIN ITS SHAPE FOR MILLIONS OF CYCLES, FAR EXCEEDING THE LIMITS OF OTHER MATERIALS LIKE SILICONE, RUBBER, AND NEOPRENE. THEY ARE DESIGNED FOR COMPRESSION APPLICATIONS WHERE VERY LOW SHEAR FORCE IS PRESENT.
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ACE Controls · Farmington Hills, Michigan www.acecontrols.com
POWER TRANSMISSION REF ERENCE GUI DE Air springs include metallic end fittings coupled by a composite elastomeric-based bladder that contains the compressed air to provide isolation. These single-acting designs have a pressurized bladder and two end plates. As air is directed into the air bladders, they expand linearly. All of these reusable designs are self-contained, offering a number of advantages over any other technology that may require outside componentry. For example, hydraulic systems may require plumbing while electrical systems may require wiring and power. Energy or power dissipation is key when selecting a damper or shock-absorbing device. The size and characteristics of the device are based on these inputs, so it is generally the first consideration to make. Dynamic spring rate and damping are the two biggest considerations when selecting an isolator. These characteristics define system natural frequency (resonant frequency) and the most suitable isolation system.
ELASTOMER, RUBBER PADS FOR VIBRATION AND SHOCK REDUCING A NEW DESIGN CONCEPT FROM FREUDENBERG SEALING TECHNOLOGIES SIMPLIFIES THE INSTALLATION OF THE SEAL BETWEEN THE HOUSING AND THE PISTON ROD INSIDE THE ABSORBER. THE WEDGE-SHAPED SEAL ALSO REDUCES FRICTION, LEADING TO LESS WEAR.
PROVEN SHOCK, VIBRATION & NOISE REDUCING SOLUTIONS
STANDARD PRODUCTS GUIDE OVER 600 PARTS 800.838.3906
sorbothane.com
Elastomer and other synthetic and rubber pads can also damp vibration and isolate shock loads. They come in tubes, bushings, blocks, pads and washers. These components work in heavy-duty applications to deliver strong cushioning for cranes, presses, and pipelines and bridges; they also excel in vibration reduction for lab and testing equipment and designs for aerospace. Rubber-like materials let these padding elements satisfy specific requirements related to natural frequency, load, and area. Because they are soft, they are also forgiving. Predicting the natural frequency of an AL I R E application lets material manufacturers target T MA known disturbance frequencies to dissipate energy. The lower the ratio of natural system frequency to disturbance frequency, the more it’s possible to isolate problem vibrations. These cushioning plates can protect machinery subsystems against impacts and isolate vibration and structure-borne noise. For example, PAD plates from ACE Controls withstand compressive loads to 10,000 psi or 69 N/mm2 depending on plate form and size. Another product called Sorbothane (from a company with the same name) is a thermoset that attenuates shock with nearfaultless memory. Deformation is elastic and not plastic, so pads of the material reliably return to their original shape. Custom pieces of the material work for vibration and acoustic damping and isolation. Sorbothane turns mechanical energy into heat as the material is deformed. Molecular friction generates heat SORBOTHANE® energy that translates perpendicularly away MADE IN THE U.S.A. from the axis of incidence.
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AD INDEX POWER TRANSMISSION REFERENCE GUIDE 2022
Ace Controls .......................................................... 33 AutomationDirect..................................................... 1 Bodine Electric Company ......................................... 9 Canon U.S.A., Inc. .................................................. 29 CGI Inc. ................................................................. 19 CMT ....................................................................... 10 Del-tron..................................................................BC Diequa ................................................................... 21 Digi-Key Electronics ................................................. 3 Dodge Industrial ...................................................... 7 ebm-papst .............................................................. 31 PBC Linear ............................................................. 23 PM B.V.................................................................... 25 Pyramid Inc. ........................................................... 14 Renishaw ................................................................ 16 SEW-Eurodrive ......................................................... 5 Sorbothane ............................................................ 34 Stock Drive Products/Sterling Instrument .............IBC THK America Inc ................................................... IFC US Tsubaki .............................................................. 12 Whittet-Higgins ........................................................ 8 Zero-Max, Inc. .......................................................... 2
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