PG acrylic burning... sometimes?

I’ve been reading through the forums for a bit but I haven’t found a post with an exact duplicate problem, so hopefully someone with more experience can answer this.

I’ve been cutting acrylic charms from a sheet of PG Medium Acrylic using the automatic PG settings. I’ve done this before with no issue, but today something is weird: All the charms are cut from the same sheet using the exact same SVG file and the same cut settings, yet half of them are burned on the back with the acrylic melted into scorched divots, making the charms unusable. The other half are perfectly cut with lovely smooth edges.

Top row clean cuts, bottom row burned cuts with and without masking. They were all laid out next to each other when cutting.


After reading other posts I wondered if this might be a flashback issue, but that doesn’t explain why it’s only happening on half of the cuts. These pieces are side-by-side on the same tray. What’s causing the 50% damage rate?

If it is a flashback issue, what material can I use to prevent it that won’t 1) alter the height of the acrylic to the point that it affects my engraving detail, or 2) flare up and cause further scorching of the masking material?

First, those are lovely charms. Second would you be able to take one of the top charms and swap it with one from the second row that scorched and just try those two. Unlikely, but maybe there is something quirky about the second row of charms in the file. Just trying to eliminate one possible source of the problem.

Might the sheet not have been completely flat?

That can happen if you are cutting near an edge or close to a hole in the material. The increased air flow coming up through the grid pockets makes the acrylic burn hotter at the cut. Laying a sheet of paper or masking tape down underneath the material to keep the air from coming up through the grid at the edges can cut down on that effect.

(Or something along those lines.) :slightly_smiling_face:

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Ah, OK, that makes sense. It’s weird that I’ve never seen it before, since I usually start cutting close to the edges to save material! I’ll try it again tomorrow and see if it’s cleaner with some paper under it.

Thanks for the help, everyone!

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I extracted the logs to investigate the problem you reported, and I noticed that in your design file, what looks like a single cut line, is actually two lines.

Reducing that down to a single line should improve your results.

I’m going to close this thread - if the problem reoccurs, go ahead and post a new topic. Thanks for letting us know about this!

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