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Author Topic: Possible G2, G3 bug  (Read 3727 times)

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Possible G2, G3 bug
« on: March 05, 2011, 10:29:21 AM »
G'day guys and gals,

I was trying out Cambam plus a couple of nights ago to make a 2.5D bracket for the mill.
After generating the G-code in Cambam I ran it through CutViewer Mill to check it and then as a final check loaded the G-code into Mach3 that I have on the house computer (Version R3.042.022 I think, certainly low 20's).
All looked good.
I then popped out to the shed and loaded it onto the mill computer (Version R3.042.028 from memory. definitely high 20's). It came up with a large circle in one of the outside corners. (image attached)
I ran an air cut thinking it was just an display artifact, but it wasn't. I then upgraded to the current lock down version (Version R3.043.022) and loaded the G-code again. Still had the circle. Finally I upgraded to the latest beta version (Version R3.043.028) and still no change.
I looked at the G-code to try and see the problem and tracked it down to the G3 statement "G3 X159.7813 Y-42.3477 I1.75 J0.0"
The G-code seems correct and this is backed up by a run in CutViewer, but Mach has an issue with that line. I edited the G-code and changed it to a G2 command. That solved the problem in Mach but leaves CutViewer following the correct definition of G2 and taking a bite out of the part.

I don't think it is hardware related, I get the same results in Mach3 both in the house ( Win7 64bit) and shed (XP 32bit).

The pictures and G-code with the suffix "raw" are as outputed by CamBam with tool and stock defined in CutViewer.
The pictures and G-code with the suffix "edited" are the ones I changed to G2.
Black circle in CutViewer images indicates the problem corner.
Mach images has the offending code line highlighted

Has anyone come up against this problem B4?

Cheers,
Phil
Re: Possible G2, G3 bug
« Reply #1 on: March 05, 2011, 10:31:12 AM »
Here is the G-code and my XML file.

Cheers,
Phil

Offline Tweakie.CNC

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Re: Possible G2, G3 bug
« Reply #2 on: March 05, 2011, 10:52:10 AM »
Try changing the IJ Mode setting on the General Logic Configuration page and see if this cures it.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Hood

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Re: Possible G2, G3 bug
« Reply #3 on: March 05, 2011, 11:11:02 AM »
Or better still have CAMBAM put the correct IJ mode ( G91.1) in the preamble :) That way it will always be correct even if some previous code has changed the IJ mode to G90.1 (Abs)
Hood
Re: G2, G3 unwanted large arc issue
« Reply #4 on: March 05, 2011, 11:26:25 PM »
Ahh, thanks Hood and Tweakie for taking the time to address such a newbie issue,
I had no idea that it was a G90/91 issue.

It all boils down to RTM or in this case RTGCM
Read The G Code Manual

Quote
Mach Summary of G-codes

Incorrect settings of this mode will generally result in large incorrectly oriented arcs in the tool path display

Thanks again,
Phil


Offline Tweakie.CNC

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Re: Possible G2, G3 bug
« Reply #5 on: March 06, 2011, 03:03:21 AM »
Phil,

I think we have all been caught out by this one sometime or another   ;)

Don't spend too long with the manuals either, life is far too short to read all the manuals  ;D

Tweakie
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.