Warped/ variable thickness workpeice compensation

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25 Jul 2014 00:56 #49100 by geo01005
So I'm planing on doing a fair amount of V-carving with my linuxcnc powered CNC router table. As you may know the width of a V-Carved segment is a function of the depth the tool penetrates the surface of the workpeice. Many pieces of wood have variable thickness or might be warped. This isn't so be a problem when using less detailed "wide and deep" carving strokes. But when doing fine engraving work you can end up with a stroke that is .015" wide on one side of a workpiece and .045" wide on the other side of the workpiece if that side is only .015" thicker, or higher.

One answer to the problem is simply only use "high quality" raw materials. I would like to look at a different answer to the problem. I'm thinking that I ought to be able to use a touch probe to do a grip probe routine before cutting that can then be used to modify the Z coordinates in the G-code to compensate for workpiece warping and variable thickness.

Is there any existing feature in Linuxcnc that does something like this? The closest thing I know if is torch height compensation for plasma cutters. Or has anybody done something similar outside of linuxcnc?

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25 Jul 2014 02:27 #49104 by alan_3301
Search for probekins
It is a kinematics module for linuxcnc that uses a touch probe to create a surface offset for the gcode to do exactly what you want.
It works very well too!

I have posted my experience with it in this thread
www.linuxcnc.org/index.php/english/forum...-and-using-probe2stl

don't get discouraged, it will take some effort to get it working, but it is totally worth it.

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25 Jul 2014 13:51 #49117 by geo01005
Cool, just what I was looking for!

Anybody used this with a gantry machine? I currently use gantrykins for my router.

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25 Jul 2014 19:05 #49120 by andypugh

I currently use gantrykins for my router.


In that case you probably have to combine the two into a gantryprobekins.
As the modifications are to different axes it probably isn't too hard (and your special kins could hard-code the gantry linking to suit your specific machine, rather than being generic like gantrykins)

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26 Jul 2014 11:17 #49160 by geo01005
Ok, that doesn't look to hard. Where is the most "official" place to get the probekins code? I didn't find it on the Linux cnc gig repository.

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26 Jul 2014 17:39 #49166 by andypugh

Ok, that doesn't look to hard. Where is the most "official" place to get the probekins code? I didn't find it on the Linux cnc gig repository.


I think here: git.mah.priv.at/gitweb?p=emc2-dev.git;a=...507e9820146e36eb7a0f

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