View Full Version : Positive backlash???

18-08-2010, 12:39 AM
Hi All..

Finally getting down to some fine tweaking... In trying to measure any slop, and I am sure I have some as my X and Y are chain driven, I have been machining some slots 100mm long..

First I move the X axis in the +ve direction, then machine a slot also in the +ve direction.. Reckon there should be no backlash at this point.. Then I move a few mm across the y axis and machine a slot in the -ve direction of the X axis.. This should, by my reckoning, then show up any backlash and I was expecting the second slot to be shorter...

But no..! It was 0.2mm longer... Have repeated this several times with the same result..

And, as always, when I get to scratching my head too much, I pop here to see what silliness you guys can point out that I am doing..


18-08-2010, 07:47 AM
Hi Steve

what happens if you zero a DTI next to the machine before it cuts the first slot, then send it away in +ve X to cut the slot, then just come back to the start position again (i.e. cut the slot twice with no Y movement)?

what happens if you do this without cutting (just jogging away and back again) to a fixed DTI?

Lost steps? Binding axes?

Robin Hewitt
18-08-2010, 09:19 AM
Cogging maybe? A chain is moving slightly faster when a roller passes perpendicular to the sprocket axle.

18-08-2010, 05:04 PM

Things to look at.. Things to try... Will try/look at later this afternoon... Thanks guys!!