Backlash settings on an axis with scales

Here is why axis backlash settings should be left at zero on an axis with a scale.  These videos were made from a newly installed 5-axis machine.

An axis without a scale positions the mechanics using the servo motor encoder.  The servo motor has no idea how much mechanical slop exists in the axis.  It’s only direct connection is to the backend of the servo motor.  Backlash values (1851 parameter setting value) basically inject or throw a few extra microns of axis movement into a motor direction reversal to try and get the mechanics quickly through the slop and into mechanical contact again as the axis is driven in the opposite direction.  Backlash parameter 1851 is really suited for a machine without scales.

An axis with a scale, however, feeds back exact mechanical axis movement using the positioning feedback loop to maintain axis accuracy based off of the actual movement of the mechanism (or scale). If a value is placed in parameter 1851 the control will be adding the extra compensation on reversal then the positioning feedback loop will move the axis immediately back to actual position as shown in the clip "CW&CCW Backlash at 68.mp4". 

Click the button below to see the clip ‘CW&CCW Backlash at 0.mp4’ for the operation of the Maxxis (using scales) with the backlash of all axes set at 0.  It is a much smoother movement on axis reversal as shown by the test indicator.