# Matching Pieces Don't Cut Correctly

I’m trying to build a box as a part of a project design I downloaded from Etsy. I’ve built a few from the same guy and he is super accurite.
So, The Box measures, by Lightburn, 338.499mm wide X 120.092 deep X120.092 high. I’ve shown a photo of how my laser cut an end piece and the top piece. You can see in the photo that the slots don’t match. The screen shot shows the same 2 pieces. The short side is the issue. The end piece is cut correctly at about 210mm while the top measures about 212mm. I’ve recut several of these pieces with the same result. I don’t mind a little trimming here or there for a fit but I’m looking at 56 slots!

Any tips or tricks in Lightburn, to get this right?

Thanks!

Dale

Would need to check the way the preview shows the cutting order and direction
However seems that you might have a tiny slack on your motions and as direction is changed you get that small shift

I would suppose the top cut was done in 1 direction and the bottom in the opposite?

Thank You Gil,

I rotated the end pieces 90 degrees and confirmed your solution. I believe it’s the Y axis. The belts seem egually tensioned.v Any suggestions?

Thanks!

Dale

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Uncertain on your machine setup, but what you might want to do is void big rapids between the two big pieces.

I use this test to test belt tension but you have to adjust it to something that makes sense on your CO2 to mark only

Dot Test with Angle.lbrn (46.3 KB)

Something else you can do is try to have the cuts run in the same direction to avoid the backlash. Where basicly half of the reverse motion is taken to retension the belt (or any mechanical looseness)

you can on those matching pieces, make sure the offending axis are avoided by forcing the motions of the axis to follow a direction

So hypothetically
If you set the shape on the left to start bottom left corner and forced the same on right shape (This goes against natural rapids optimization) the finish position of the left motion would NOT move the Y axis, and would keep - in theory - the backlash in check.

Obviously this only matters much on large shapes but best to find the solution to the hardware issue than trying to “fix it” by trickery on software

Is the dot test cut or engrave?

Engrave so you need to adjust my diod settings for your Co2, or it will go right through your test piece

Than you for your help!

Good Morning,

I re-ran the project again understanding that doing the same thing over again and expecting a different result. is the definition of insanity.

While awaiting Omtech’s response, I thought I would send you a bit more detail. The screen shot shows the defective end panels on the second attempt, I rotated the shorter piece 90 degrees to see if it made a difference; it did not.

The long sides of the front, back, top and bottom were cut on the X axis and all fit perfectly. I have no idea about the short sides of these pieces. They may be off as well. I did note differences in the Lightburn sizes of these 6 pieces and then compared to actual dimensions. every piece is off.

I’ll have to wait for Omtech, or recut these pieces on my diode laser.

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