Steps Appear to Shift Mid Engrave


We have been running laser cutters for many years now and have decided to switch over to LB as a common software. We have an issue though on one of our lasers where the steps appear to shift while it is engraving. We engrave many identical small parts laid out on a jig in the laser. The laser was off by a few mm (the engrave was not centered on the part) so we ran the calibration tool to fix that.

Now here is the fun part. The engravements are aligned to the center on the left side of the jig, but on the farthest right side, they are not. The engravement slowly shifts over as the laser goes farther and farther over to the right side. In my head, it sounded like a belt slipping issue, but the engravements are good quality and not skewed in any way which I believe would be present if the laser was slipping.


Perhaps it’s the classic Ruida skew problem:

That can occur on either axis, although it seems to be more obvious on X because that’s most often used for engraving passes.

In “standard” CO₂ machine configurations, both PWM Rising Edge Valid switches will be False, so if either of the ones in your machine are set True, flip them without changing anything else and run the failing job in the same position.

Bonus weirdness: it’s triggered by specific positions of specific patterns, so a machine that has worked perfectly can sometimes develop a hitch in its git-along without any provocation.

Thank you for the tip.

Unfortunately, that did not work. They were both false, so I turned them both on and ran the same job but no luck.

Well, we’ve ruled out one possibility … :ballot_box_with_check:

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Another less likely possibility is that your laser head is not square to the travel of the gantry, the further it travels the more out of focus it will be, and the difference in focus will cause the illusion it is more out of position than it actually is. If it was a diode laser it would be easy to test and fix, not sure even where to begin with a tubular lens housing in how to test but I am sure there are some out there smarter than me that could find a way to do it.

Check the physical hardware of the machine. If you only have this issue on a single machine, it’s likely that there is something wrong with it. It could be a stretched belt, missing belt tooth, a loose motor pulley, or something else that requires physical adjustment.