Linear guides, PT, and actuators see unexpected applications

Our 2020 survey of the industry indicates an unabated trend towards more automation of previously static or manually tended systems. Key to these new offerings is installation simplicity for OEMsand end users of linear components for linear axes … as well as positioning stages and Cartesian robots.

In fact, Cartesian robots (also called linear robots) increasingly serve as turnkey solutions where tasks were previously done manually. That’s in part because (where suitable) linear-based solutions offer simplicity and precision at a price point that’s unrivaled by other solutions. So linear motion adherents want these multi-axis arrangements to come to mind when laypeople and engineers alike discuss robotics.

“When discussing robotics, some people think of walking robots. Others picture consumer-grade designs or even toys and Japanese companion robots. Those in automation often conjure a 6-DOF robot or SCARA in their mind’s eye. I’d really like to change such preconceived notions — at least in our industry. After all, a gantry qualifies as a robot. It is taking human motion and it’s repeating it and it’s programmable,” says Macron Dynamics national sales manager Michael G. Giunta.

Giunta considers it a core mission to help industry recognize Cartesian arrangements as robotics.

“The official definition of robot is a machine capable of automatically replicating certain human motions and functions. So a linear-motion installation in a fast-food kitchen that picks up a fryer basket and moves it to a second location as a human would do is in fact a robot. In contrast, the Da Vinci surgical system is often called a robot, but technically it does not qualify — because its movements are ultimately controlled by a human being,” explains Giunta.

Trends in linear guides and guide rails, slides, and ways include more uses for profile rails and linear bearings with plain bearings and linear guide wheels. Our experts reported more configurability for both rails and shafts as well as carriages and runner blocks that traverse them. That’s to satisfy demand for flexible machines that employ modularity to adjust to changing processes for material-handling machinery, packaging, and other forms of factory automation. This year has also brought increased focus on hygienic component designs. Those in turn are supporting some newer automation industries — such as that for CBD or cannabis-related products.

“Machine builders are now using our products for automated watering systems as well as the positioning of lights and a whole range of tasks in the vertical and indoor farming industries,” says Matt Mowry, DryLin product manager at igus. DryLin products are also used in automated installations to support planting — especially for seeding and (after harvest) the pressing out of plant oils.

“Designers use our lead screws because they continuously run clean. If dirt does get on them, they still perform well,” adds Mowry. The self-lubricating screws need no oil, which is important to the CBD and cannabis market for meeting the standards for products meant for human consumption. “Plus the linear actuators are much lower in cost than actuators based on ballscrews … and maintenance free.”

These are IMA-S integrated electric servo actuators from Tolomatic that meet hygienic standards with no harborage points for bacterial growth. 316 stainless-steel construction resists corrosion and withstands hot and high-pressure caustic washdown. IP69K ingress protection makes these linear actuators suitable for open machine designs. A hollow-rotor motor design outputs up to 11.1 kN and strokes to 450 mm with options for planetary roller screws or ballscrews. Feedback is via a multi-turn absolute encoder (Hiperface DSL, Hiperface Sin- Cos, EnDat 2.2), incremental encoder, or resolver to integrate with most PLCs or control systems.

Home hobbyists making routers and 3D printers are other users of these components. "Frequently, they get plans online and swap out the steel ball bearings with our bearings for higher consistency and self-lubricating nature,” adds Mowry.

ACTUATION TREND TO MORE PRECISION

Ballscrew-based and newer belt-based linear actuators are associated with high precision on large motion axes ... and miniature designs can in some cases employ leadscrew-based actuation to satisfy the same design objective.

“Laboratory automation has always been a great fit for linear motion … especially stepper linear actuators. Of course, within certain laboratory devices, precision is required for moving samples into position, adding reagents, and withdrawing samples,” explains Dave Beckstoffer of Portescap. “Now, advancements in the linear force and speed capabilities of stepper linear actuators let device manufacturers increase their throughput with these actuators without sacrificing quality.”

The terms stepper linear actuator and stepper-motor linear actuator typically refer to can-stack stepper motors with a built-in leadscrew. “The laboratory devices are also rendered more adaptable to additional tasks and analysis thanks to the miniaturization of stepper-based linear actuators,” adds Beckstoffer.

ACTUATOR TREND TO EASE OF INSTALLATION

The past year has brought new electric actuators that complement battery-powered designs for mobile and off-highway vehicles, medical equipment, and transportation systems. These eliminate efforts related to successful integration for OEMs and end users. Check out the Design World 2020 Trends article on shocks for another example of new motion applications in the offhighway industry.

“We recently developed a longlife electromechanical linear actuator to withstand harsh environments such as those associated with pantographs for the connection and disconnection of electric power in mass-transport applications,” says Anders Karlsson, product line specialist for linear actuators at Thomson Industries.

During the day, the left side of the living room wall slides into the living room to open the home office. A screen on the partition rotates to provide teleconferencing for home office or entertainment in the living room.

Karlsson also sees more buses, trams, and trains incorporating hybrid powertrains employing externally supplied electric power and batteries. “This means vehicles charge on overhead lines when available and then disconnect from the charging system to run systems off batteries ... so there are high cycle counts for actuators in these vehicles. “Our Electrak LL delivers long life here — and meet rigorous railway standards.”

Another battery-powered application making use of linear actuators is automated guided vehicles (AGV) for material handling. Some AGVs necessitate 24/7 operation even if duty cycles never exceed 25% or so. “The stroke our compact HD actuator excels here — and with 10 times the life of a standard actuator, our LL is durable enough for inclusion on AGVs,” adds Karlsson.

USE EXAMPLE: ACTUATORS RECONFIGURE HOMES

Traditional residential construction is fraught with inherent inefficiencies. Bedrooms are infrequently used during the day, while living rooms are unoccupied overnight. At a time when real-estate prices are climbing (especially in urban areas) the desire for single-purpose rooms inflates prices. Plus energy consumption is rising in many parts of the world … so the need to heat and cool unused space adds cost and degrades environmental sustainability.

So one group of Virginia Tech University engineering faculty and students aimed to design a solution to these issues. Now their smart house prototype has rooms that can reconfigure on command by touch, voice, gesture or smartphone. Their design includes electric-motor-driven linear motion from Thomson Industries to move room-sized load-carrying walls smoothly and quietly.

“Some of the modules have sliding walls to adjust room sizes to suit various purposes as they change throughout the day,” said Virginia Tech architecture professor and director of the FutureHaus project Joe Wheeler.

A FlexSpace demonstration home Wheeler and his team built essentially delivers 1,500 ft 2 of living space in a 900-ft 2 footprint. The area of the prototype’s home office, living room, and bedroom are fully adjustable by sliding the partitions that separate them.

“If a person operates a business out of the home and requires conference space, he or she can just command a partition to move into unused living room,” said Wheeler. “At the end of the workday the partition slides back to re-expand the living room. Embedded in the partition between the office and the living room is a large viewing screen, which can be rotated into the home office (for use in teleconferencing during the day) or back into the living room for TV in the evening.”

The FlexSpace system allows the adjustment of living spaces. This is one floorplan from above. The bathroom and kitchen modules form the top row, and the home office, living room, and bedroom are the lower row. Sliding walls in the lower row (alternate orientation shown in blue) let homeowners transform their living space based on time of day and activity.

The partition between the living room and the bedroom can also move to provide a larger living room during the day or a larger bedroom in the evening. For these adjustments to work easily, the partitions must be able to move easily, quietly and smoothly, while also carrying a heavy load. For example, one side of the partition between the living room and bedroom carries the living room sofa with it as it slides. The bedroom side would carry a fully stocked room-length closet and drawer storage. To handle such loads, the team chose two electronic linear-motion systems from Thomson.

CHOOSING THE RIGHT LINEAR-MOTION SYSTEM

The university team already knew of Thomson motion technology from their research on an earlier, similar model of a solar-powered housing project.

“We needed to have the strength to move load-carrying walls easily and the intelligence to be do it on demand,” said Wheeler. Thomson linear-motion technology provides that robustness ... and the actuators’ built-in electronics and communications allows connectivity with the home network.”

The FutureHaus engineering team chose the Thomson Movopart M55 linear system for each moving wall. A smaller unit would not have done the job, and a bigger one would’ve added unnecessary cost and energy consumption. These units are belt driven and incorporate engineered polymer bearings for smooth motion. Each unit is about 7 ft long with a movable area of 5.8 ft to add about 10 ft to the living room when both walls are repositioned. Within the actuators, low-cost servomotors pair with Micron NemaTrue planetary gearheads designed for highprecision motion-control applications requiring a high torque-to-volume ratio, torsional stiffness and low backlash. Errorfree attachment of the motor shaft to the gearheads is via a Thomson RediMount adapter kit, which connects in about five minutes.

A bedroom partition (left) slides to open living room space (as seen in the living-room image of this article.

Safety is fundamental to the FutureHaus designs, so engineers ran all actuator selections through a LinearMotioneering sizing tool to verify a safety factor ten times higher than needed for the specified load and speed. Once verified, Thomson delivered the preassembled linear motion system.

In operation, users glide each wall along rollers suspended from the ceiling on both ends of the wall. The linear motion systems sit above the ceiling on one end of the wall only, providing the thrust needed to move the wall back and forth along the rollers. Built-in sensors stop the wall if it meets any resistance.

Besides being a highly functional and economical living space, the FutureHaus is prefabricated so that components can be produced by efficient mass production and then shipped and assembled onsite.

“We’re just scratching the surface of where we can go with this,” says Wheeler. “We’re now working on a model optimized for affordability.”

The Thomson Movopart M55 linear system with RediMount motor mounting adapter smoothly moves walls to add about 10 feet of living room space.

Linear shaft motors see increased force capabilities thanks to advances in magnets

By Paul Denman • Applications engineer and business development Nippon Pulse America

Today most linear-motion designs executetheir strokes with actuators based on steppermotors or brushless dc (BLDC) servo motors. Such designs have an inherent complexity dueto the fact that the motors and its gearing and encoder must essentially hang off the machine design and out of the needed motion space. One fast-growing trend is migration towards linear shaft motors — a more compact solution that only requires space for an encoder and linear bearing inside the motion space.

Linear shaft motor adoption has grown faster in the last decade due to the increased performance of their magnets — which in turn has made them more power dense than early-generation versions. How do these linear motors work? In short, the motor’s magnetic shaft consists of a hollow nonferrous stainless-steel tube housing a stack of doughnut-shaped magnets. Because the forcer coils wrap a full 360° around the shaft’s magnetics field, these linear motors deliver 40% more power than competitive offerings. What’s more, one shaft can accommodate several forcers — for even more compact and flexible solutions.

Some manufacturers of linear shaft motors even stack the magnets with their poles north to north and south to south (in a rather advanced assembly process) for even higher force and efficiency. That results in linear motors with exceptionally high force capabilities. This design arrangement and the fact that magnets have become increasingly strong mean that some linear shaft motors can output more than 6,000 N.

One last benefit of linear shaft motors is that they exhibit zero cogging so maintain high accuracies — even up to the accuracy of the selected encoder. Resolutions better than 10 µm are possible without increased motor price.

Nippon Pulse America can supply linear shaft motors up to 14 feet long.Applications of these higher-power shaft motors are expanding as engineersdiscover their availability and use.