rookie having problems with cutter compensation

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28 Jun 2020 22:26 #173044 by mphle
Hi all!

I'm new to g-code and linuxcnc so I apologize in advance for what may be a stupid question...

I've installed Linux Mint 19.2 and linuxcnc 2.8 combo from BeagleBrainz as linked by tommylight here;

forum.linuxcnc.org/9-installing-linuxcnc...nd-easy-installation

and everything I've tried so far has been working great except G41 and G42 commands.

If I install a tool with a diameter of 0.125" via

T1 M6

and then use either G41 or G42 and try to program a lead-in move like:

G0 Z1

I get a lead-in move cutter radius error no matter what I put in for the Z distance.

If I put an X or Y move in like:

G1 X1 F10

the machine does not move at all. I don't get any error code but I get no movement from any axis.

when I then type G40 however, the machine immediately moves to the previous commanded place (ie x1) but with the correct cutter compensation in Y (ie +/- 0.0625" if using a 0.125 diameter mill depending on G41/G42)

Any thoughts or help is greatly appreciated!

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29 Jun 2020 05:58 - 29 Jun 2020 06:38 #173054 by Aciera

If I install a tool with a diameter of 0.125" via

T1 M6

and then use either G41 or G42 and try to program a lead-in move like:

G0 Z1

I get a lead-in move cutter radius error no matter what I put in for the Z distance.


I don't use cutter compensation a lot but I think you need to do the G0 Z1 movement before you activate G41 or G42. The lead in move needs to be at least as long as the radius of the active tool. In your case the lead in move in XY is zero. That is why you get an error message.

As to your other problem: Is this in a program or in MDI mode?

[edit]
I think you are trying to use cutter compensation in MDI mode.

Check out the docs (section 6.1.3) linuxcnc.org/docs/2.8/pdf/LinuxCNC_Documentation.pdf
The end point of each move depends on the next move.  If the next move creates an outside corner the move will be to the endpoint of the compensated cut line. If the next move creates in an inside corner the move will stop short so to not gouge the part.The following figure shows how the compensated move will stop at different points depending on the next move.

So just commanding G1 X1 F10 does not provide enough information to execute the move.
Last edit: 29 Jun 2020 06:38 by Aciera.

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29 Jun 2020 12:14 #173078 by mphle
Yes, I am only working in MDI mode at the moment as I try to learn the basics. I'll try a short program with cutter compensation invoked. Thank you!

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30 Jun 2020 01:38 #173162 by mphle
All sorted - works great when part of a program. Thanks!

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