Linear Positioners Catalog_en-US_revA - Kollmorgen

L I N E A R P O S I T I O N E R SLinear Motion Terminology: Linear Positioner PrecisionBacklashThe clearance between elements in a drive train or leadscrew assembly which produces a mechanical “dead band”or “dead space” when changing directions, is known as thebacklash in a system.In most mechanical systems, some degree of backlash isnecessary to reduce friction and wear. In a Kollmorgen LinearPositioner System, system backlash will typically be 0.010– 0.015 inches. Usually 0.006 – 0.008” is attributed to the ballscrew/ lead screw assembly. For ballscrews this will remainconstant throughout the life of a cylinder, while for leadscrews it will increase with wear.Reducing the Effects of Backlash1. Approach a stop position from the same direction.2. Apply a constant linear force on the cylinder thrust tube orcarriage. This is done automatically for cylinders used invertical orientations with a backdriving load.3. For programmable positioning devices it is possible toprogram out backlash by specifying a small incrementalmove (enough to take out the backlash) prior to makingyour normal moves in a particular direction.4. Use a preloaded nut on a ballscrew to counteract thebacklash. Contact Kollmorgen about the precision groundscrew option which reduces backlash in the drive nut.5. An inline positioner with the motor directly coupled tothe ballscrew has less backlash than parallel or reverseparallel units which utilize a gear train or drive belt/pulley.Primary Sources of Backlash1. Ballscrew/Lead screw Assembly2. Drive Train (Gears, Timing Belt/Pulley)BacklashBallnutBacklash3. Timing Belt/PulleyBacklash4. CouplingBacklash92K O L L M O R G E N