Black cast 5mm acrylic - HELP!

Hello, I don’t seem to see a post for what I am looking for, so hoping someone can assist.

I am using 5mm black cast acrylic.

  • I have removed the paper masking, and applied the 3M as I need to apply this to wood.
  • I removed the clear plastic masking, as I have read that it melts. and instead applied the vinyl ease paper masking. should I have left it on??

I am using 130 speed, full power, one pass. it’s cutting through perfectly.

my issue:
-cut with 3M down, raised off bed, with paper masking side up : the paper masking is leave a burn line and melting. solution: remove (duh) but the laser is actually leaving a slight melt line contouring the cut.

  • cut with paper masking down, 3M up, raised off bed : similar result.
  • cut with damp paper towels, no paper masking side down, and 3M up. : similar result. but now the exposed acrylic melted.

Changed speed to 135
-cut with damp paper towel, no masking side down, 3M up : still melting the face of the acrylic
-cut with damp paper towel, masking side down, 3M up : not melted, but still leave a slight melt line all around the laser edge.

am I being picky? What am I doing wrong! I need this for a commissioned boardroom sign…

Which machine do you have? The proofgrade cut settings for thick black acrylic on the pro model is 125/full. I just cut a small square of Proofgrade thick black acrylic at that setting, and I think the result is acceptable.

As for the “melt line” I am not sure what you mean by this. Can you share a photo of the item that you find unacceptable? Perhaps you are hoping for a more flame polished appearance.

I have never elevated black acrylic nor used the wet paper towel or any other modification of the process of simply putting the item on the tray and cutting. Applying the 3M tape will change things a bit, but not very much, in my experience. The tape is so expensive, however, that you want your settings dialed in to minimize the waste.


I have rarely seen clear plastic masking except on extruded material, and the problems you are having are common on extruded material. I have some purple acrylic that was supposed to be cast but kept melting like extruded.

There is a point where it does not make it through if 135 also cuts perfectly then I would try 140 etc. and back down to the highest speed that cuts all the way.


I was thinking the same thing…sounds like extruded.


Thanks all. I have the Pro. I’m a complete newbie (Jan 22). Hoping these photos show what I was trying to explain above.

The letters that I’m going to be cutting out are only about an inch and a half tall.

Processing: 562F224F-C510-4341-85B1-8BA3032655EA.jpeg…
Uploading: D5602C5F-B86E-4B9F-99E3-C3F6DE46A355.jpeg…
Uploading: AED19E7A-A245-4A6B-8C24-EA6F13C10B8E.jpeg…
The star was just a sample to see what would happen.

Additional samples

I believe your problem is the material. This doesn’t look anything like what my sample cut at 125 looks like. Yours would melt even more at 125 than it has at 135.


Also, try masking front and back with paper masking tape. (Yeah, I know it seems like extra work, but you’re trying to compensate for flashback.)


ugh. thank you for trying! I was completely shocked! I have had amazing luck with mirrored gold compared to this. the masking on the back clearly says cast acrylic on it…

thanks, I did sadly. the 3M side is good… it’s the shiny up side that I had masked is the paper was melting to the acrylic. I’m going to try playing around with a few more settings and contact my supplier… they suggested I do 130 with 2 passes! my goodness, who knows what it would look like then! lol

Try putting the 3m side down on the honeycomb tray and leaving the other side unmasked and cut at 125/full. If it is cast acrylic, it should look fine.

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Man I wish this was easy. I did two test…. Both with 3M down.

One with no top masking and then one with the paper masking.

Here’s a sample as well as what happens to the surrounding acrylic so if I try to cut out a word my worry is, it’s just ruining the rest of the acrylic with some sort of flashing.

Is this black mirror acrylic?

it’s not supposed to be! at least that’s not what I asked for. i was told it flat one side, shiny the other. but it is very shiny :slight_smile: the backing on it says Cast Acrylic.

I may just switch to wood and paint them myself :frowning:

What does this mean, exactly?

I placed some acrylic underneath (equally) to lift it hoping to prevent any flashback on the back. Someone else has suggested this in another group. I stopped that suggestion as it didn’t work.

Good to not do that…a fire hazard, for sure.


thanks! I’ve tried masking, unmasking, speed at 125, 130, 135, I’m not sure why the edges a melting a bit. I’m reaching out to my supplier to find out what could be wrong, as i started with the setting she suggested (minus the second pass, as I don’t seem to need that. )

Try faster - the over melted edges mean too much power is hitting the acrylic. You can always use more passes to get all the way through.