Mechanically preloaded split-pinion drives have an axial spring to load one pinion half against the other. And electrically preloaded dual-pinion drives have two motors, each driving one pinion, which are loaded against each other through a motor controller. The drives have ultraprecise positioning and repeatability, and maintain these characteristics during acceleration and deceleration, as well as when they reverse direction.
Atlanta Drive Systems, 1775 Route 34, Unit D-10, Wall Township, NJ 07727, (800) 505-171, atlantadrives.com