Print And Cut Double Sided Issues

After a major problem with my laser power supply and stepper motor failure I decided to upgrade and rebuild everything and when I got everything back together and aligned and working it seems there is something strange going on with the print and cut alignment. in the past i did have a issue spacing items evenly in lightburn but learned from that :wink:.

I upgraded to the Ruida 6445S controller from the 6442g because it was having issues uploading and starting jobs over the network. i also upgraded the steppers with Stepperonline closed loop motors which work great engraving and cutting but this double sided problem is driving me crazy and any help is appreciated.

here you can see i can cut 100mm squares out in each corner of the bed and tolerance wise it is great.

but from the pics below you can see that after the print and cut alignment on the back it is shifting as it gets towards the bottom but is ok at the top which has me baffled to where to look.

here is the test file i was working with.
Print-Cut-Test.lbrn2 (37.8 KB)

So did more testing today and double checked my backlash and dont really see any. but did a couple tests which the results i dont know what to think of. any help is appreciated…

One test i did was i just cut the squares and alignment markers and did not flip the card stock but i did run it through the print and cut process and recut the squares and all the squares were lined up and you could not tell it was 2 passes with one being the original and the second with the cut and print.

Here the strangest of all. I moved the alignment markers to the middle of the job and it looks like the skewed cuts also moved and almost made the error less noticible and spread out over all the squares instead of just the bottom ones but it is still off which i dont really what to make of it.

This sort of issue has some of the hallmarks of a racked (not square) axis, or a bowed X gantry. Given that the error occurs only in one location of your workpiece, I’d lean strongly towards a physical issue here.

With that said, Print and Cut does rely on precision marking of fiducials, if your marks are very close together your chances of getting skew in your work is higher.

My laser bed is 500x700 and found no problems with cutting squares in any bed location and other stuff i was testing and when i tested 100,150 and 200mm squares i never seen any curved/bowed edges. so this has me scratching my head. before my steppers and controller changes i did not have any issues (other than my own mistakes spacing items evenly which i learned from) which again is puzzling as well.

As for the x/y gantry I actually used many 123 blocks bolted together and clamped to the actual x/y linear rails on each side to keep the gantry for x/y square when i assembled it back. also i know it is pretty much square as i can do the print and cut and when i use the jog to next position button it lines up all the time without any adjustments assuming that i have the item on the bed square and the stock is not skewed in some way or another.

i guess i will test again with a stock piece that extends all the way across the bed and make a cut then use a straight edge to see if is bowed as you say.

i have ran 6 jobs on trotec multi color acrylic using this method and stock size with the alignment marks in the exact positions before the controller/stepper upgrades and they all worked fine.


While i did not have any stock long enough i wanted to destroy i just taped together 2 of my testing card stock which is 305mm x 305mm x1.25mm. you can see from the pics there is really no bow and while there are some gaps they measure around .06-.08mm but not in a bow type fashion across the entire axis.

thinking about the whole problem alignment shifting when I moved the alignment marks to the middle it kind of does not make sense if there was any bow in the axis or any squareness issues because all it seemed to do is take the already misaligned cut and move it pretty much the same amount i moved the alignment marks down thus moving the problem upwards the same amount.

here is the x axis agains a straight edge.

here is the y axis agains the straight edge too.


here is more strange things to add. I tried to take any linear travels out of the picture by turning the back side and it results in the same thing and it shows the print and cut is somewhat working correctly and compensating on the turned stock but it still has the offset problem towards the bottom. Now I am even more puzzled :rage:

here is the back side turned after print and cut alignment

Left side results from the 1st cut side.

Right side results from the 1st cut side.

So more testing this morning and nothing resolved, this is driving me crazy and not sure where to go now… :rage:

another test i did was move the alignment marks to the bottom of the project and on the back side with the cut and print wizard aligned up the marks to the stock and sure enough the problem shifted to the top of the stock when it was finished and it was off the same amount as it was normally when cut when the marks were at the top.

I basically reset the closed-loop steppers back to factory as well as my 6445s controller. i recalibrated everything again and even tested the bed squareness to the laser/gantry and i think it is great and should not be influencing any cut jobs.

here you can see the cut path from each corner and they pretty much meet up showing the bed frame is pretty much square with the laser head/gantry. i only reference the parts from the left and bottom bed frame rails using blocks that are exactly the same size to space them away from the rails.

i have a question about the Show Last Position button, when it is used to show the laser head position after aligning the first or second markers with the print and cut wizard is it supposed to also align with the marker?

i have moved the laser head over to the first marker which is centered on the alignment marks and hit the get position button but the last position does not represent the location of the laser head in relation to the alignment markers.

here is the first postion aligned to the center of the marker and head location lightburn thinks it is at.

here is the second positon, when i used the jog to position in the wizard it lined up perfectly to the second marker but in lightburn it does not show that either even after using the get position button.

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