Self-contained linear motors
Though small, the linear-motor slice of the overall motor-market pie is sizzling. While linear motors continue to expand into new areas, one factor limiting growth is the complexity of integrating ancillary components. It's not uncommon for the added cost and time of aligning and assembling rails, slides, bushings, and feedback devices to offset any gains in speed, acceleration, and accuracy. But three linear motor suppliers, LinMot, Linear Drives Ltd. (LDL), and California Linear Devices have recently introduced 'self-contained' linear motor designs. By integrating magnets, coils, bearings, and in one instance feedback into a single device, these new designs promise to make linear drives easier and less costly to use.
With prices starting at $600/axis, LinMot's small-diameter (23- and 37-mm) cylindrical design makes it a strong contender in the pneumatics arena. Achieving forces up to 45 lbs, LinMotP drives target cost-sensitive applications involving high throughput and light loads that don't require micron-level accuracy. To keep size and cost down, the design uses internal Hall-effect positioning sensors to achieve 0.004-inch linear resolution.
LDL's ThrustTube(TM)exploits a simple patented design based around a tubular magnetic thrust rod and a moving thrust block that carries a set of thrust-generating, circular armature coils. Without forced cooling, the design can achieve 292-lb forces. It's speed ranges from a few microns/sec to greater than 10 m/sec, it delivers up to 20-g accelerations, and with the addition of a linear scale it achieves micron-level accuracy.
Providing up to 750-lb peak force (with 30-A excitation) over a 2- to 12-inch stroke range in 2-inch increments, California Linear Device's 5020-4 direct drive linear tubular motor is a contender in the low-end hydraulic market. The compact linear servomotor develops a maximum frequency (accelerating and decelerating) response of 60 Hz over a 1/8-inch distance. With a 50-inch/sec top speed, its sensing probe extends the length of the motor running through the center to achieve positioning accuracy of 0.001-inches.
Linear-motor-driven positioning table is created for use in single- or multi-axis positioning applications that require speeds up to 3,000 mm/sec and precision meeting plus or minus 0.5 micron repeatability. The 406LXR is powered by a slotless linear servo motor, which provides smooth motion. It can accelerate up 5g, travel as far as 2m at velocities to 3 m/sec, and offer controlled resolutions of 0.1, 0.5, 1.0, and 5.0 micron.
Parker Hannifin , 1140 Sandy Hill Rd., Irwin, PA 15642; FAX (724) 861-3330; www.daedalpositioning.com
The IP65 SilverMax(TM)delivers up to 1,700 inch-oz of torque and 700W of power at only 48V. The unit supports electronic gearing, registration moves, serial communications, and seven configurable I/O. The servomotor also handles up to 100:1 inertial mismatches. This control system combined with the high-torque magnetic gearing of the motor reduces or may eliminate the need for gearheads.
Quicksilver Controls , 712 Arrow Grand Circle, Covina, CA 91722; FAX (626) 915-2836.
The PX790 Series transducers use thin-film technology and precision machining and electropolishing to meet 3A standards. These high-reliability devices include NEMA 4X enclosures and are constructed from 300-series stainless steel. Operating temperatures are -20 to 180F with compensated temperature from 30 to 130F. The gauge type uses a stainless-steel diaphragm and a diffused silicone sensor.
OMEGA Engineering , Box 4047, Stamford, CT 06907-4047; FAX (203) 359-7700; www.omega.com
SmartMotors incorporate the controller, amplifier, encoder, PLC, power supplies, and a network manager into a brushless dc servomotor. The maximum resolution of 256,000 counts can be retained, even at speeds in excess of 5,000 rpm. Because the controller is inside the motor, data transfer problems are eliminated along with signal integrity issues in electrically noisy, industrial environments.
Animatics Corp. , 3050 Tasman Dr., Santa Clara, CA 95054; FAX (408) 748-8725 www.animatics.com
Motor and driver
The AXH Series is a family of 30W (2.36 inches sq) and 50 W (3.15 inches sq) mini brushless dc motor and board-level driver packages. The motor and driver package provides speed regulation of plus or minus 1% maximum over a 25:1 speed range (100 rpm to 2500 rpm). The packages are UL and CUL approved.
Oriental Motor Corp. , 2570 W 237th St., Torrance, CA 90505; FAX (310) 325-4146; www.orientalmotor.com
New SFERAX SL series linear ball bearings feature a self-locking retention mechanism that reduces assembly and maintenance costs. These bearings can be pushed into place by hand, potentially eliminating the need for C-clips, grooves, bonding, and other traditional flange retention measures.
Schneeberger Inc. , 11 DeAngelo Dr., Bedford, MA 01730; FAX 781-275-4749; www.schneeberger.com