Linear Positioners Catalog_en-US_revA - Kollmorgen

Linear Actuation Operation: Rotary to Linear ConversionLinear motion systems driven by rotating electric motorscommonly employ one of three rotary-to-linear conversionsystems: ballscrew, belt drive, or lead screw.BallscrewThe majority of linear motion applications convert motortorque to linear thrust using ballscrews due to their ability toconvert more than 90% of the motor’s torque to thrust. As seenbelow the ballnut uses one or more circuits of recirculatingsteel balls which roll between the nut and ballscrew threads.Ballscrews provide an effective solution when the applicationrequires:• High efficiency - low friction• High duty cycle (> 50%)• Long life - low wearBall / Lead ScrewScrew-drive mechanisms, whether lead screw or ballscrew providehigh thrust (to thousands of pounds), but are often limited by criticalspeed, maximum recirculation speed of ball nut circuits, or slidingfriction of lead nut systems.BallscrewL I N E A R P O S I T I O N E R SLead ScrewThe lead screw uses a plastic or bronze solid nut that slidesalong the threads of the screw, much like an ordinary nutand bolt. Since there are no rolling elements between thenut and the lead screw, lead screws yield only 30-50% of themotor’s energy to driving the load. The remaining energy islost to friction and dissipated as heat. This heat generationlimits the duty cycle to less than 50%. A great benefit of thelead screw is its ability to hold a vertical load in a power-offsituation (refer to the Backdrive specifications for lead screwpositioners). The lead screw is a good choice for applicationsrequiring:• Low speeds• Low duty cycles (50%)• The ability to hold position while motor power is offLead Screwwww.kollmorgen.com81