does it matter what direction im doing it, Should i be checking a larger or smaller distance
In general:
A short distance is fine and you only move in one direction and then measure the non movement (backlash) of the axis when going in the opposite direction.
Some things and refinements to be aware of:
1. Steps per unit need to be correct for best accuracy of backlash measurement.
2. Backlash can vary some due to mechanical items.
3. There is no such thing as ZERO backlash, may be small but it is there, just a matter of amount
4. Bearing preload can affect backlash location along the axis since you need to apply opposite force to load up
the bearing. You need adjust / remove any play in the bearing and yet minimize amount of torque used post adjustment.
5. Backlash can vary due to the quality of the screw / nut. You will have what you got. Some screws are not linear, IE
+- accuracy over say 3 feet, but that +- can be happening in say a 12" section of the screw! Or the screw pitch can be slightly
different in the opposite direction.
6. Belt tension, quality of belt/pulley/gears / rack etc come into play etc
So rather easy to get the backlash down to some small amount,but, to really minimize it you got to get very meticulous
about everything. Thus in the end you got what you have and overall mechanical system affects backlash.
RICH
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