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Understanding Backlash in the Context of Precision Gearboxes

POSTED 05/27/2022

What is Gearbox Backlash?

Backlash is defined as the play resulting from the clearance that exists between gears or other mechanical elements of a gearbox.  This clearance is most commonly seen or experienced when changing the direction of the input shaft.
The beginning of the linked video very simply depicts backlash in a screw and nut.  In gearing, the concept is essentially the same. Video


Methods of Reducing Backlash

Backlash is minimized in planetary gearboxes by maximizing the quality of the gear geometry and precisely controlling the mating parts.  Grinding the faces of each individual gear tooth ensures that when components are assembled, minimal clearance between parts exist without creating interference which would impact the efficiency and smooth operation of the gearbox.

In Onvio’s Cycloidal Reducers, backlash is removed in the assembly process, by individually pre-loading cam followers so that they are in full and constant contact with the cam.  This eliminates the clearance that results in backlash. 


Measuring Backlash in Cycloidal and Planetary Gearboxes

Backlash Unit of Measure

  • Backlash is commonly measured in arc-minutes
  • 1 arc-minute = 1/60th of 1 degree or .0167 degree

Backlash in any gearbox is measured by locking the input shaft against rotation and applying a measured force to the output shaft. By using a load cell and potentiometer, a plot can be created. Backlash occurs at close to zero load when rotation is reversed.