I doubt this pertains to Lightburn directly but I’ve tried other groups and zero help. I have an OMTech 60 2028 red n black. I find that it if set multiple passes on a cut line it ‘appears’ to be ok. if i set multiple passes on an engraving, the head goes back to origin then proceeds to perform second pass. It’s always off just a tad making a 2 or 3 pass engraving impossible.
I’ve tightened belts, calibrated axis(s) and ensureed mirrors are dead on. I’m totally stumped on how to fix this.
Just trying different avenues for help. Thanks
Origin or home? Is there a difference on your machine? On GRBL, it’s two different locations. Home trips the endstops. Origin does not. Mine are separated by 4mm.
Why is it returning to “origin”? This shouldn’t be necessary if your machine is otherwise accurate. Do the steppers idle down during this process? If so, you may be losing microsteps or even full steps.
If going to "home’, depending the homing switch type and mounting, homing accuracy can be less precise than axis motion. Any little flex, bounce, delay, etc in the switch setup (both mechanical and electrical) can change zero relative to the workspace. Not sure what setup variables you can adjust on your machine (I don’t have a CO2), but on a GRBL machine, after verifying/eliminating any mechanical flex, I’d try slowing down the home seek rate at $24.
I have a similar laser and you have more places to check. 
Assuming the motion is off in the Y-axis direction, check all the setscrews holding all the couplers & pulleys to the shafts. The motor is tucked in the back of the laser where you (well, I) can barely see it, but one of the shaft couplers looks like this:
The pulleys are probably press-fit on the shafts, but if they have setscrews (perhaps hidden in the teeth of the belt path), make sure those are tight.
I marked the couplers / pulleys and the shafts to make any motion obvious, but I admit to being compulsive about that sort of thing.
While you’re in there, make sure the brackets / pillow blocks holding the shafts are snugly screwed in place.
The entire laser head must be firmly attached to the X-axis slide, which apparently isn’t always the case. Grab the nozzle and give a firm wiggle: if you feel any motion, fix it.
It’s possible a mirror can loosen in its mount; use a pin wrench to verify the lock ring is tight.
The focus lens can be loose inside the laser head or, in one case, shattered in just the right way to continue kinda-sorta working while rattling around.
Less likely will be loose linear rails along either of the axes; all those screws must be snug.
Good hunting!
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Thanks for you recommedation. I’m going to get into it this weekend and see what happens. Just to clarify, I position where I want the ehad to start from and set that as Origin. When the the job is done the head is set to return to oring. I can change that in Lightburn and have it return to 0,0 and see if that helps. Thanks again!
I’m going to look at this, this weekend. I’m excited to see if that’s the proble.
Thanks for your reply. I intend to do a follow up post if I gett his working properly and the solution. Thanks again!
I’ve cleaned, lube and check tightness of everything I possibly can. It seemed to improve some but still randomly a bit off. I’m wondering its the best I can get with stepper motors?
The motor step distance is on the order of 10 µm, roughly the wavelength of infrared light, so the problem is not “stepper motors” but other part(s) of the mechanical drivetrain.
Because the situation improved after snugging things down, but is not yet spot on, you probably missed a few opportunities for further improvement.
You’re looking for something that is slightly loose, so you must work methodically from the motor mounts outward to the laser nozzle and take nothing for granted. This is tedious and seems unrewarding, but it’s what you must do to eliminate all the possibilities.