When it comes to linear motion, there is always a tradeoff between speed, accuracy, load capacity, and length of travel. Nexen has created an innovative new technology that helps ease these tradeoffs. Their Roller Pinion System (RPS) combines the advantages of linear motors, ballscrews, and belt drives to provide fast linear motion with zero backlash, high accuracy, and long travels.
With traditional rack and pinion systems, the pinion gear teeth slide along the rack teeth as the pinion rotates. To reduce wear and friction, a small clearance is required between the rack teeth and pinion teeth. Depending on the application, this may introduce too much inaccuracy. For higher accuracy, a ballscrew might be used, but ballscrews have a limited length and speed. Linear motors address the speed and length issue, but the cost of long magnet tracks can be prohibitive.
The RPS system addresses the accuracy and wear issues by using bearing supported rollers and a special rack tooth profile. The rollers meet each tooth along a tangent path and smoothly roll down the tooth face, as opposed to a pinion which slaps into the tooth and then slides down its face. This increases life and lowers noise. The tooth profile is designed so that two rollers are loaded in opposition at all times, providing zero backlash.
The RPS system can achieve speeds up to 11 m/s and provide dynamic thrust up to 14000 N (3150 lbf). Racks can be assembled together in 0.5 and 1 meter increments, allowing unlimited travel lengths. As shown with the sample data below, the system’s accuracy is better than +/- 30 microns and does not vary with travel distance.
The video below shows the RPS system in action.
