Height warning with tray in and material thickness at .020 *PETG"

I finally got my PETG material to make proto face shields. I cut about 15 of the face shields and one of the headbands. The shields material is .020 PETG while the head bands are .060 PETG (just like the template specs call for). I get the settings from the Glowforge community and they work like a charm. Now I get the height error message despite doing nothing different than before. I am using magnets that are 4.01 mm in thickness to hold .020 material in place as it does bend easily.

I’ve done everything I can think of including cleaning glowforge so now I’m sitting here ready to make face masks but I’m stuck… after waiting weeks to get material.

Not sure if it is what is causing the problem, but try taping the material down instead of using the magnets. Strong ones can cause issues.

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Taping won’t work because once the outer edge is cut (for some reason this part cuts first) the shield will pop up off the tray. With the magnets the shield stays flat after the outer edge is cut so the holes can still be cut. It’s bad enough that the thin waste excess pops up and ends up close to where the material is still being cut. Maybe I’ll see about getting thinner magnets. Seems like always hicups for me.

Try putting some tape in an area that won’t be cut, and using “set focus” on that.

The machine can’t check focus on clear material.

Magnets won’t hurt unless you’re extremely unlucky. Mine are so strong I need to pry them off the bed if they come in direct contact.


What might work is something like a Seklema mat. It’s sticky to hold everything down, and it’s made for lasering thin materials. (Works great for things like paper and fabric, which also pop up and blow around.)

Alternatively, make the stroke color for the inside lines Black. Make the outside cutline Red. That will create different operations, and you can cut the interior lines first, the outside shape last. (No more popups.)

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this. it doesn’t need to be a big piece. i put on a little 2x2 square of blue tape and focus on it.


I had four magnets originally so went with two further away from the cut line. I also put thin tape on the curved most edges. Seemed to do the trick as I’m cutting again. I’m going to look into the mat as well as that looks like a great idea. Thanks again.

A possible solution:
If you change the outer cut line to a different color than the holes (in your design software) they’ll be separate steps and you’ll be able to set the inner holes to cut first.

I like this idea too! Thank you.


I’m sorry that you ran into trouble while trying to set up your print. It’s great to see that the advice from other community members got you back up and printing! Thanks folks!

I’m going to close this thread. If you run into trouble again, or have any questions, please post a new topic on the form or email us at support@glowforge.com and we’ll be happy to help.