Tuesday, April 24, 2001
Tired of the same old technology for rotary indexers? Brakes, clutches, cams,
gears, and controllers that have hardly changed in years? Well, several
suppliers may have the answer. NSK, Kollmorgen, and Bayside Motion Group, have
all recently introduced rotary indexers designed to help engineers improve the
design of automatic machines.
With these designs engineers can:
*Reduce parts count
*Eliminate gearboxes, belt/pulleys, ball screws, couplings, and brackets
*Reduce cost of stocking, purchasing, and support
*Reduce machine size
According to Hartford-CT based AutomationSolutons' Richard Manders; they are all based on similar technology to linear motors, and provide massive amounts of torque for their size. "By moving the motor coil to a ring around the outer diameter of the motor, the force being produced is far greater due to the leverage created by moving the force point out," Manders explains.
The Megatorque motor from NSK (www.nsk.com) has no cams, clutches, and brakes to wear. The smallest YS series rotary indexer churns out 44 inch-lbs of torque in a package less than 1-inch thick and 6-inches in diameter. The largest provides 4,000 inch-lbs of torque at 3 rps. It supports up to 4,500 lbs, and moment loads up to 3,400 inch-lbs. Positioning repeatability of 2 arc-min and encoder resolutions up to 614,000 counts per revolution make it suitable for robots, measuring instruments, or machining centers.
Another high performance servo solution with zero maintenance is the GOLDLINE(r) DDR from Kollmorgen (www.kollmorgen.com). "There will be no gearbox lubrication, belt tensioning, seal leakage, and replacement," explains Kollmorgen Director of Product Line Management Tom England, "because the only wearing component is the bearing in the motor." And for the DDR this is an oversized, rugged, crossed-roller bearing. The D081 provides up to 225 lb-ft peak torque, up to 100 LB-ft continuous torque, speeds up to 500 rpm (8.3 rps), resolution up to 2,097,152 counts/rev, and repeatability down to 0.62 arcsec. It handles axial dynamic loading up to 7,900 lbs, and moment loads to 322 LB-ft
Interested in low friction rotary motion? Then check out the RD series direct-drive rotary stage from Bayside Motion Group (www.baysidemotion.com). Its brushless dc servomotor achieves speeds up to 200 rpm. "By replacing traditional worm gears, the design reduces wear, friction, and eliminates backlash," says Bayside's VP Technology Alan Feinstein. A built-in encoder achieves high positioning accuracy with repeatability between ±2 encoder counts, and resolutions to 0.5 arcsec.