Black Smudge Marks on Some Prints

I’ve run into a new problem that I think has to do with the honeycomb bed, but want to see if anyone has run into this problem before. Attached are two photos of a batch print I just ran.

{Cutting 1/8" Birch wood with transfer masking on it}

First photo is the front of the prints

Second is where the issue remains. One of the shapes has a sludge black burn to the whole perimeter, while the other one came out just fine.

Does anyone know why this is happening? I’ve cleaned the bed with the recommended method on several occasions, but this still keeps happening.

Thanks you to anyone who has input here, still a newb and might be a newbie error.

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That’s called flashback - it happens when there’s too much power so the laser bounces off the tray and back up into your material.

Solutions include - lowering the power or raising the speed of your cut, masking your material so all the power gets absorbed by the masking, putting down a layer of sacrificial material (this one you have be extra careful because it raises the risk of fire)

Do a search for “flashback” and you’ll find even more advice!


That’s scorch marks from the laser hitting the honeycomb and reflecting onto your media. That’s a big reason we mask both sides of the media we are cutting, to protect it from the scorch marks.


Thanks for the quick reply! Will look into it

I’m so sorry to hear that you’re running into trouble.

It looks like @deirdrebeth and @marthajackson1970 provided some great information about this behavior. Please let me know if the suggestions do not help improve your prints. We’re here to help!

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Yup that is flashback. To be that bad your cut is way overpowered. Masking , sanding or cleaning is the choices available. If you want no flashback occuring you are asking that occasionally it does not cut through.

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