Not Square (skewed)

Based on the nature of a CNC device like the glowforge, I was very surprised by this bug. (At least I’m hoping it’s not a hardware issue.)

I was trying my first attempt at double sided printing today. I’m doing a series of tiles that have a simple scored pattern on one side and engravings on the other. My file has both sides, but I ignored the layers for the front and I first scored the back. I then cut out a rectangle that was the size of all the tiles plus a bit more for good measure.

My hope was to then carefully flip the cut out part and then swap the ignored layers and do the engraving and cutting of the tiles. Theoretically it would align perfectly. However when I got to this step I found that even though the file was a perfect rectangle, it cut at a slightly skewed angle. So when I placed it back into the space it fit on one side, but not the other. There was about a 1/4" gap on one side.

Has anyone else run into a problem like this?


Is it skewed or kerf causing the issue? (I would think a rectanlge is a rectangle as long as the drawing was correct) :thinking:

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There is this one topic where issues of being out of square are addressed and it gets into lots of possible reasons.

Have you tried to repeat this behavior using cardboard? Also, have you tried to move the rectangle to a different place on the bed. Doesn’t seem like much room to work with to position further back, but perhaps a bit a little room to go further left with it. Something about the lower right corner issues might be popping up.


It’s definitely skewed. I double check the file and it’s square, so it should fit back perfectly into the space, but it doesn’t. There’s a gap at the bottom right and it overlaps on the top right.

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Sounds like your gantry is out of square.

The gantry on my PRU was out of square as well. I had to fix it manually.

Get a carpenters square or something else and double check it against the Y rails in your machine.


Thanks @takitus. I think I can manage that, but have never done anything like it before. Any direction you might have would be very appreciated.

Well, the other side just finished. As expected, the alignment was not what I was hoping for. And to add insult to injury the proofgrade medium maple ply failed and didn’t cut all the way through in a lot of places. Some areas will be fine with a bit of sanding, but others pulled off the veneer when I tried to separate the cut.

I have noticed this also. I will have to manually check my gantry - several projects I have run ended up slightly out of square. I didn’t notice until I flipped one part and suddenly everything fit together perfectly.


GF says camera alignment is defective if more than 1/4". I wonder what they consider a defective level of gantry skewness?


After trying to square my gantry, I am not sure a perfectly square gantry is in the design possibility. There seems to be about 2 degrees of slop in my gantry with the power off. I doubt we will be able to square to anything more than that with machine vision.


Has anybody seen it adjust the gantry skew during the homing sequence? I have been wondering if / how it does it without limit switches. There are two separate Y motor drives with their own step and direction signals but the motion plans only have one Y step and direction.

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Thanks for letting us know about this, @mheiselt, and I apologize for the delayed response. Based on the details you’ve provided, it’s possible that this piece of Proofgrade may not have been lying completely flat.

Proofgrade material can develop a curve (called ‘warp’), and warped material may not cut as expected, especially if your print or the warp are large.

Could you please lay the piece of plywood that you used for the print on top of your Glowforge, and take a photo facing the edge of the material?

It’s been a little while since I’ve seen any replies on this thread so I’m going to close it. If you still need help with this please either start a new thread or email