More use of linear motors (+ complementary drives + linear bearings)

By William Fang • Engineer | Chieftek Precision USA

Chieftek Precision USA sees six trends in automation that are changing which kinds of motion components get used in new installations. Leading technologies include linear stages, linear encoders, servo drives in flexible formats, linear slides, direct-drive rotary tables, and linear motors.

Pre-integrated linear stages (and predesigned motion systems in general) see rising use. That’s because OEMs in particular are looking to focus on their primary competencies … and outsource motion engineering to get more complete automation solutions out of the box. To satisfy this demand, Chieftek products include our compact linear motor stage (CLS), compact linear motor stage (CLMS), and moving-magnet linear stage (MMLS).

Recall that unlike linear actuators that generally have lighter frames and employ a variety of motor-driven mechanisms, linear stages include a solid flat base of steel or granite for rigidity … and typically employ either motor-driven ballscrews or linear motors.

Direct measurement of linear-motion output with linear encoders has become indispensable for semiconductor, medical, and precision laboratory applications. Here, Chieftek offers linear encoders based on magnetic operation to (among other things) maintain design ruggedness and precision.

Today’s servo drives include unprecedented connectivity options to fully leverage motor capabilities. Case in point: Our Chieftek TC1-D servodrive and stock 8-A and 20-A (1.5 kW and 5 kW) TC-1 Series drives complement linear-motor applications; our TCB-1B Series drive supports all standard encoder formats with connectivity and functionality for sin/cos, resolver, Tamagawa Seiki, Nikon, Mitutoyo, EnDat, and bi-directional synchronous serial interface (BiSS) feedback. The inclusion of both sin/cos and resolver support is unique.

The compact single-axis TC1-D dc drive runs on 48 V with a continuous output of 30 A; target applications include electric vehicles, robot arms, and direct integration onto linear stages for embedded control. The servo drive has all the same encoder features of our TC1-B drive … far more than typical offerings on the market today (with limited digital-feedback options). The drive relies on a single microcontroller with a compact 2 x 2 in. board. Ultimately the goal is to offer the drive as naked core modules to integrate into users’ motherboards; as units for use with a breakout board using JST connectors (to integrate onto robot arms); and a more traditional version with a “bookshelf” format to go into control cabinets.

Customizable linear-slide technologies are core to next-generation medical machines and electronics-manufacturing facilities. In fact, Chieftek’s roots are this area, as our first products were miniature linear guides. Today, these precision offerings continue to lead in the medical industry. Besides the miniature slides, other Chieftek offerings include standard and wide four-row ball-bearing linear guides; four-row roller-type linear guides; and ST miniature stroke slides with two rows of balls and a gothic ball track with a 45° contact angle to deliver load capacity comparable to that of a mono block.

Direct-drive rotary tables and torque motors are helping to improve inspection and general positioning tasks. Our DD Motor is a newer offering in this area.

Linear motors are proliferating where other linear-actuation technologies once dominated. Here, Chieftek offerings include iron-core as well as ironless linear motors with specialized Y-beam forcer coils to shed heat and boost overall performance.

Migration towards ever-better precision is spurring use of these linear motors in medical, packaging, material handling, automotive, off-highway, and general automation. The direct-drive nature of these motors makes for quick and precise moves as well as slow and steady strokes where needed.

More specifically, linear motors have longer life than mechanical linear actuators in short-stroke applications, because they avoid wear, shock, and fatigue issues. In contrast, we’ve seen ballscrews and leadscrews on short-stroke axes that only last a year before failure.

On the opposite end of the spectrum (on long-stroke designs) linear motors also excel; in fact, precision linear motors for industrial applications have essentially unlimited stroke lengths. That’s in contrast with most mechanical devices such as leadscrews, which have speed limits due to their tendency to whip or thrash beyond a given value. No wonder linear motors are increasingly applied on long-stoke axes where such screws or rack-and-pinion sets might get used despite limitations — on robotic seventh-axis RTUs, for example. Here, linear-motor designs can be built and installed in 1-m sections — a level of modularity impossible with leadscrews.

Another benefit of direct-drive positioning with linear motors is how it allows processes to occur directly on production lines. Consider LCD-panel manufacture: Here, overall plant yield can increase when post-production processes detect (and save for commercial sale) nearly perfect panels. Linear motors move probes about flagged LCDs for pixel verification. Then the linear-motor-based system moves other tools such as cutters and lasers over the LCD’s pixels needing remanufacture. Here, the system cuts that transistor off and then replaces it … or might fix or replace the electronic traces. Such designs leverage the sub-micron positioning accuracy of linear-motor-based designs. For more information, visit chieftek.com.