How to measure backlash

[slinky]

Hi all,

Is there a way to measure backlash?
Is there some equipment I could buy or something?

Has anyone done it or have experience in this?

Thanks in advance all

 

[Robo Guru]

Ive used a simple dial indicator with magnetic base

[slinky]

Thanks RG. 

So I assume, You just set the DTI in a fixed position for each axis and physically move each axis (push backwards and forwards) and measure the maximum deflection for that axis.
Obviously being careful to only move one axis at a time.

Then, using the measured distance from the centre of that axis I should be able to calculate the arc minutes?
I'm also assuming the best time to do this is after a grease exchange.

Please tell me if I'm going down the wrong path here.

 

[Robo Guru]

Sounds about right... although I have never quantified it in Arc Minutes.... only measured it in mm.

Typically when I have done the backlash measurement it was part of a PM package so I would grease, batteries, backlash, etc....

RoboGuru

[SkyeFire]

Depends on what you're trying to measure.  I did it using a laser tracker and a target on the TCP, but that was to measure Cartesian-space backlash under various conditions.

Simply grabbing an axis and pushing it back and forth may not give you what you're looking for.  I did backlash measurement for a single axis by moving an axis to a given position from both the positive and negative directions, and measuring the difference in the two endpoints.  For backlash in Cartesian space, I moved the robot to the same programmed point from a "sphere" of different start points, and measured the spherical distribution of the robot's stopping points.

[DHawk]

make sure your axis is parallel with gravity otherwise your backlash measurements will be influenced.