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Motion Control/Power Transmission

Motion Control/Power Transmission

SIX AXIS, HIGH-RES POSITIONER

Aerotech FiberMax(TM) Nano Positioner. Developed for high-volume manufacturing and testing of fiber optic components, the FiberMax positioner directs four to six drive axes with resolutions of 10 nm (X-Z axes), 2 nm (Y axis), and 0.027-0.058 arc sec (roll, yaw, and pitch). Such performance begins with Aerotech's patented small direct-drive, brushless and slotless dc motors and linear motors, notes Tom Markel, product manager for the Precision Positioning Group. Low noise, high-bandwidth control electronics for the optical encoders (40 MHz input B/W on the encoder signal) allows such tight stage control. "The big challenge was getting all the direct drives into such a small package, roughly 224 x 150 x 168 mm, with high accuracy," he adds. A patented stacking system allowed integration of six stages into one unit. (www.aerotech.com) Enter 582

DIMINUTIVE DC BRUSHED MOTOR

Faulhaber Group DC Micromotor Series 0615. This may be the world's smallest brushed dc motor at 6 mm in diameter and 15 mm long. What allows such a small size are neodymium (NdFeB) rare earth magnets and a coreless rotor with the self-supporting System Faulhaber(R) skew winding. Applications Engineer Ken Porterfield notes development was an evolutionary process of fabricating smaller and smaller windings, resulting in smaller packages. Depending on the winding chosen, the coreless motor runs on a loaded current ranging from 100-300 mA thanks to its low inertia without a rotor core and low contact-resistance precious metal brushes. Rotor inertia is only 1.42 x 10-7 oz-in-sec 2 (a third that of the company's previous generation 8-mm coreless brushed motor) with an 8-10 ms mechanical time constant. Performance includes a stall torque of 0.23 mNm, output power of 0.12W, and no-load speed of 19,900 rpm. (www.micromo.com) Enter 583

MORE TORQUE, SAME GEARMOTOR VOLUME

Exlar SLG Series Gearmotor. The T-LAM(TM) individual-phase, segmented-lamination stator design in the SLG Series' brushless servo motor results in 35-50% more torque/volume than conventional brushless servos, according to John Walker, engineer and sales manager. Three frame sizes (60, 90, and 115 mm) provide maximum torque outputs of 340 lb-inches at 1,250 rpm; 1,550 lb-inches at 1,000 rpm; and 2,900 lb-inches at 750 rpm, respectively. Cutting heat allows greater current for more torque. With T-LAM there is extra copper wire (along with thermally conductive epoxy) to dissipate heat, as well as no energy-wasting end turns. In addition, the planetary gearset uses the output shaft of the motor as the sun gear for an integrated package that eliminates an extra set of bearings and any couplings, increasing stiffness up to 25%. As a result, performance is maintained at lower rms current levels than for conventional, bolt-on planetary gearbox designs. (www.exlar.com) Enter 584

HIGH SPEED AND TORQUE ROTATION

Bayside Motion Group RD Series Direct Drive Rotary Stages. Featuring a resolution down to 1.37 arc sec (R200D, 200-mm diameter model), brushless dc servo motors crank up the rotation of these rotary stages to 700 rpm (R100D). Key to the design is integration of a high-resolution encoder, brushless inside-out motor, and stiff one-piece rotor/top plate shaft into an extremely low (down to 75 mm) profile. "Speed is limited by the maximum frequency of the encoder read head," notes Tom Gianni, senior application engineer. He adds the encoder is an inline rotary type (ring scale) surrounding the motor for compactness. With fewer parts than traditional worm gear stages, direct drive increases reliability and dynamic performance-worm gear friction limits rotation to 30 rpm and RD stiffness is ten times the 24 Nm/deg of a worm gear. (qp.baysidemotion.com) Enter 585

LOW PROFILE, HIGH PRECISION STAGE

Primatics PDR Rotary Stage. Fitting a precise rotary stage into a volume 55-60 mm high, with table diameters of 110-210 mm, was a challenge for mechanical engineer Darren Froschel. He was able to do it, relying on a "good glass, high res optical encoder" and a direct drive brushless dc servo motor, tightly surrounded by a laser read head and control electronics. By coupling an encoder disk-featuring a 20-micron grating, for 18,000 divisions-with on-board electronic interpolation, engineers achieved a resolution of 0.25-16 arc sec, depending on optical hardware and software options. Oversized cross roller bearings increase stiffness, smoothness, and load capacity. The motor is a 12-pole count for minimal cogging. Stage prices start at $3,800. (www.primatics.com) Enter 586

PRECISE VELOCITY AND POSITION CONTROL

Anorad RDR-160 Direct Drive Rotary Positioning Stage. The brushless rotary motor in the RDR-160 rotary stage eliminates gear drives for smoother motion in a compact 80-mm-high envelope. A high-res optical encoder (18,000 lines/rev for 0.36 arc-sec resolution) and 4-point contact bearing set add to accuracy ( plus or minus 15 arc sec) and repeatability ( plus or minus 1 arc sec), allow speeds up to 90 rpm, and result in lower maintenance costs (thanks to upper and lower labyrinth seals) compared to gear-driven units. A single row of 4-point-contact bearings provides the same support in a lower height as two conventional bearing rows with 2-point contact of each ball with its race, notes Project Manager Mike Pitka. Applications include laser machining, wafer processing, and high-accuracy inspection. (www.Anorad.com) Enter 587

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