Y-Axis ~2mm off on Cut, Accurate on Move?

I don’t know what to think about this… I’ve only had my Ortur LM2 Pro LF about 2 months and had not noticed this until I cut some layers for a shadow box and found the distance in a cut for the Y axis off (short) by about 2mm at a 100mm cut. I initially thought this was just an axis calibration issue, so I used that tool (in Lightburn)… but the Y-axis was off only a fraction of a mm for a 300mm move. I still calibrated it and it’s pretty much spot on for a 300mm move.

I then cut a couple of squares, a 100x100mm and 75x75mm. X-axis is pretty spot on, but the Y-axis cut is short by about 2mm.

I don’t know where to go from here, other than to add 2mm to my vertical height in Lightburn.

Thoughts, suggestions, recommendations?? Thanks in advance!

Likely something mechanical. I would first check the pinions on the stepper shaft. My guess is that the one on the Y stepper is loose and is shifting by 1 mm in either direction before settling. Check the placement of the pinion and resecure grub screws making sure that one of them is properly secured to the flat portion of the shaft.

I shall check that. Thanks for the tip. Fingers crossed.

There did not seem to be any looseness in the pinions. I also attempted to tighten the belts some, but there didn’t seem to be any slack there.

Any other suggestions would be appreciated. I’ll make another test cut tomorrow. Light’s too bad in the garage now. :wink:

Thank you!

When you get back to it try burning some circles. Do the ends of the circle meet? If so, then likely not an issue with backlash (e.g. from pinions being loose). If they don’t then still likely a backlash issue somewhere in your mechanical chain. Going from joint to joint to figure out where slop is being introduced.

Separately try manually moving the laser head around the entire frame. It should be smooth and consistent through all corners with no binding. If you notice anything, try to isolate the source of the anomaly and eliminate it.

Great, appreciate the suggestions! I’ll try the circles; suspect they’ll be ovals in the y directions.


Follow-up: Nothing mechanical seems amiss. I re-calibrated the Y-axis using burn distance instead of just a move. Works great. Burn distance is more important to me than just moving.

$64,000 question is why is there a difference between move distance and burn distance??

Final follow-up:

OK, I’m an idiot (actually, more of a NOOB). I contacted Ortur support (who replied fast enough for me to call it ‘prompt’). They suspected loose belts (heard that before) or the rotary was enabled.
As I had just re-set up for flat vs rotary, that was my Duh-Oh moment. Disabled the rotary, reset GRBL, and rechecked calibration. I redid that a bit, but now both X and Y axis move and burn the same distances.

TIL: disable the @#$% rotary setting!


Gil is great and is active on this site as well.

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Great to know, thanks!!