Rolamite Linear Actuator Cuts Friction and Complexity

May 23, 2014

Engineers at NASA first developed the rolamite bearing as a way to get motion with less friction than possible with roller bearings and to eliminate cogging. It was to replace leadscrews and linear ball slides, which require lubrication. The resulting device did the trick, cutting friction by an order of magnitude and totally eliminating cogging during linear motions. An inventor then converted the bearing into a linear actuator powered by a servomotor.

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The payload can mount to either the carriage, a gantry-type actuator, or the housing (for pick-and-place applications). A tensioning band woven through the rolamite bearing, which is turned by a servomotor through a worm drive, propels the carriage along a track. The housings and track are made of aluminum to reduce weight.

The bearing is formed from rollers constrained by a Mylar-film or stainless-steel tension band wrapped in an “S“ configuration. The band is perforated to prevent slipping and provide precise position control. A double “S” wrap ensures the pure rolling motion is completely converted to ripple-free linear motion. Positioning is governed by a linear scale or encoder.

The bearing includes the drive, reportedly reducing complexity, cutting costs in half, and extending the operational life because most friction is eliminated. Payloads under 2 lb can be moved by a 5-W motor. Nominal speeds range up to 20 ips with strokes as long or short as the application requires.