Some creations and a bit of learning

30 degree V bit, 2 mm DOC, 15mm/s feed rate, 5% stepover.
I did notice theat the gcode file is HUGE at 1.3 MB, might that be a clue

Would you mind sharing the .gcode file?

Not at all, what’s the best way to share it?

Just post it here. You can use the upload button.

I like this theory a lot. It looks like it was working back and forth on the M, then it took off toward Y=0 (or wherever the bottom was), then it has a command to move only in X, then it had a new Y command, so it went tearing back to the top.

How are you sending the gcode? SD card from the LCD? Repetier Host? cncjs?

New Pub.gcode (1.3 MB)

My gcode files, saved on my laptop, are associated with repetier host, I assume that’s normal and OK.
I save to an SD card and then use the LCD.

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Tried a new SD card (Blank, new, 16Gb, 80 MB/s), no improvement. Of the two fails today, one has the vertical additional cut, one has a horizontal ‘bonus’ cut.
I tried breaking the job up into smaller pieces, but this also had the extra cut (but in a different place).
Did a quick check of the gcode for that fail and there’s definitely no ‘Y0’ other than at the beginning and end. All very puzzling.
It can’t be a coincidence that this has restarted (it happened a few times right after I’d built the CNC) after I just increased the bed size and reorgnised things (tidied up wiring etc).

Gcode looks good. It simulates just fine in both the locations that is messed up in the cuts above. You might be getting power brownouts. I had that happen a couple times with my v1 lowrider. Had a funky connection inside the power supply.

That’s my next job, strip down all the electrics and check for any weaknesses.
Which is doubly annoying because I finally got round to some decent cable management, but I keep reminding myself, there must be a reason for this, it’s science, not voodoo.

A little voodoo helps…

I’ve cursed at it animatedly, so that should help.

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I don’t think a Y0 is appearing in the gcode. I’m guessing a read error from the SD card is losing a bit of random data. Could be the SD card, card reader, cable from LCD to Mini-Rambo…

If you have the ability to try sending the gcode from a computer (Repetier Hose, Cncjs, etc) that might help narrow it down.

@barry99705’s Brownout problem seems plausible too.

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I haven’t used Repetier host to control the CNC directly, so I will have to do a bit of reading first, but right now that seems preferable to unwrapping and inspecting all the cabling.
Thanks for your help all.

Check the cables from the display to the controller esy to get interference on them

@timonjkl, stupid question: what am I looking for, proximity to other cables…?

Overnight I got to thinking about static. I’ve just put the machine in an mdf cabinet and we have had unseasonably dry and warm weather. I’m going to earth everything.

Possible also just bad connections after being moved

I’ve checked all the connections are seated properly, but it’s worth rechecking. Thanks.

I had this happen with my laser about 5 years ago and dont remember the cause . Gcode error or sender or noise in line its skipping code line and getting shot off but resumes the next line in correct spot not skipping steps just misdirected I dont remember the cause though

Does it happen randomly or same spot? It is not going to x or y 0 is it ?

Different spots when I run the same job, heads down to Y0, then back up to resume the job.
Less frequently it goes to X0. It seems to happen once or twice in each run.