Lightburn file and resulting cut don’t quite match…

[Hairyspooner (Pete)]

I have an issue that sometimes occurs with specific files, haven’t been able to find answers online (maybe I’m not using the right words). When cutting certain files my finished cut will not quite match Lightburn file. But as the difference is so small, and I only experience this issue with specific files (no other cutting/burning issues) I don’t believe it can be a problem with my Omtech laser.Files are always bits with living hinge, so lots of parallel lines. I cut one yesterday, design had 31 curved parallel lines; 30 of them cut correctly, 1 was a couple of mm down from where it should have been. Other occurrences: a design had 33 vertical parallel lines, 32 cut completely fine then 1 cut at a very slight angle. Had one that did just one line about 5 mm to the left of where it should have been. I go back and check the files and Lightburn is dead on. All designs are my own, I only use Lightburn as well so not an imported file from somewhere. Any ideas?

[MikeyH (Mike Hembrey)]

@Hairyspooner

All designs are my own, I only use Lightburn

Three possibilities: [1] Lightburn, [2] Ruida controller, and [3] mechanical.

Lightburn, nope. Ruida, very unlikely. That leaves mechanical.

1. Is the final line that shifts in the same place physically on the machine grid?
2. Is it possible that something loosens up after 30 or so lines, like a thermal issue?
   1. Couplings
   2. Pulleys
   3. Laser tube holder
   4. Mirror holder
3. Does it ever mess up when doing only 10 lines?

Exclude the impossible and what is left, however improbable, must be the truth.

[ednisley]

@Hairyspooner

then 1 cut at a very slight angle

This could be another oddball case of the Ruida PWM Rising Edge Valid settings problem. It generally shows up with images, but dense vector patterns can also expose it.

More discussion and what to do:

Image shifting and bunching up but cut out is OK

Red-Black 90w Laser Ruida controller engrave 400mm/s 25% Fill 450mm/s 20% Cut 25mm/s 65% Birch ply held down pins belts are tight so are stepper motors When doing a engrave/fill and cut I get the fill shift while the engrave bunches up, cut out in just fine. This is repeatable, and all come out the same, like it was meant to be, how do I attach image?

Many more examples …

If that’s not the case, then upload one of the failing lbrn2 files along with a screenshot of the (presumably correct) Preview and a crisp photo of the (incorrect) results to help us see what you’re seeing.