Lead Screw Not Going Expected Distance

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Cattmy
Posts: 10
Joined: Fri Dec 28, 2012 4:28 am

Lead Screw Not Going Expected Distance

Post by Cattmy » Fri Jul 17, 2015 9:27 pm

I got my hands on an indicator from Little Machine Shop to find out how much backlash my new lead screw machine has. To my surprise, when I sent a command through Chilipeppr for the X axis to go 0.01", it only went ~0.0088".

I have 8mm/rev lead screws and have my TinyG set accordingly. My machine is under a month old and is not equipped with anti-backlash screws.

Am I being too picky or can this be fixed?

cvoinescu
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Location: Camberley, UK
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Re: Lead Screw Not Going Expected Distance

Post by cvoinescu » Fri Jul 17, 2015 9:55 pm

Measure over a much longer travel, say 2" or so, using calipers. The error you see could be backlash, or simply measuring error. An indicator is a great tool to measure repeatability, not so great for measuring scale errors (because of the very limited travel).
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

Cattmy
Posts: 10
Joined: Fri Dec 28, 2012 4:28 am

Re: Lead Screw Not Going Expected Distance

Post by Cattmy » Fri Jul 17, 2015 10:14 pm

Looks like it was measurement error. Tried again and it worked well. Is a backlash of 3.2 thou normal for these smaller lead (M8) lead screws with non anti-backlash screws. Is there anyway I can make this better on my machine without upgrading the nut? Are there any CAM scripts that can compensate for backlash? HSMWorks and Chilipeppr don't seem to have any compensation built-in.

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