[Solved]LinuxCNC is rounding corners, doesn't follow the original gcode

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26 Feb 2022 11:29 - 26 Feb 2022 21:40 #235842 by Twizzlermill
Hello all,

I'm not sure whether this is the right subforum; I'm not even usre that this is a LinuxCNC issue and not something I need to solve during CAM, but I figured I need to start somewhere.

I also apologize in advance that this post may be a bit incoherent, this issue is very new to me and I'm still figuring out where exactly the root cause is.

Setup:
I'm running LinuxCNC with a Mesa 7i7i6e card and JMC closed loop steppers. The CAM software I use is FreeCAD (Path job is set to "LinuxCNC" as output method).

Here's the problem:
Yesterday, I was cutting a 35mm block of aluminium, pretty much pushed my machine to the limit of what it is capable of. I'm still very much in the learning phase; most stuff I made so far worked out nicely, but yesterday, I had two issues that were related to the machine not following the gcode path 1:1, but taking shortcuts in the corners. The first one I assume was due to my machine not being calibrated properly. The toobit cut into the edge of the block during an admittedly sketchy 3d surfacing operation:

Last edit: 26 Feb 2022 21:40 by Twizzlermill.

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26 Feb 2022 12:24 #235843 by tommylight
Try using G64 P0.1
where 0.1 is 0.1mm of tolerance from he exact path, so use a value that is suitable to you.
That has to be at the top of the gcode file, although also check if CAM is adding some strange gcode.
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26 Feb 2022 14:08 #235847 by Twizzlermill

Try using G64 P0.1
where 0.1 is 0.1mm of tolerance from he exact path, so use a value that is suitable to you.
That has to be at the top of the gcode file, although also check if CAM is adding some strange gcode.
 


Thanks, I'll try that.

I don't see any strange gcodes, but maybe I'm missing something. This is the start or the code:
(Exported by FreeCAD)
(Post Processor: linuxcnc_post)
(Output Time:2022-02-20 16:13:03.348369)
(begin preamble)
G17 G54 G40 G49 G80 G90
G21
(begin operation: Fixture)
(machine units: mm/min)
G54 
(finish operation: Fixture)
(begin operation: 8mm_endmill001)
(machine units: mm/min)
(8mm_endmill001) 
M5
M6 T1 
G43 H1 
M3 S0 
(finish operation: 8mm_endmill001)
(begin operation: RampEntryDressup)
(machine units: mm/min)

Could it maybe have something to do with running a different code earlier? Maybe that some commands were still active and not revoked? Because I ran a different operation right before the pocketing one.

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26 Feb 2022 15:38 #235850 by tommylight
That all looks good and dandy, so give G64 a try.
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26 Feb 2022 15:54 #235851 by andypugh
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26 Feb 2022 21:40 #235878 by Twizzlermill
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