Black scorch marks in bright-colored acrylic

[BeamGeeks]

Hey all! Back for some more advice. I cut some Proofgrade acrylic, and on the Medium Red and Medium Yellow, you can see black scorch marks in the corners of sharp angles, and in the text. I can’t seem to get it out. I started with warm soapy water in my ultrasonic cleaner, giving them a good 5-7 minutes in the bath, then scrubbing them with a toothbrush. No dice. I then tried out some 91% isopropyl alcohol since I remembered some folks talking about using that. Still nothing. At this point I’m not sure what chemical to throw at the problem, or maybe it’s soot that’s now fused with the acrylic and no scrubbing will get it out? I wonder if I need to adjust my process to prevent it in the first place. I had the backing on the front and back, and a thin piece of card under it to prevent melting around the text.

Have any of you seen this? What steps might I test to resolve it?

[mad_macs]

Have you tried a polishing compound, or rubbing compound? Soft Scrub, baking powder, Bon Ami?

[GrooveStranger]

I cut a lot of acrylic and have never seen that. It sounds like the power is too high or speed too low, which doesn’t make sense with Proofgrade.

For a plastic cleaner with mild abrasive, get some Novus #2. However, it will fog a shiny surface, so be careful. (For general plastic cleaning with no abrasive, Novus #1 is the stuff. Anyone working with acrylic should have a bottle of #1 handy!)

[kittski]

I wonder if I need to adjust my process to prevent it in the first place. I had the backing on the front and back, and a thin piece of card under it to prevent melting around the text.

I don’t think you’ll find a real practical way to get rid of any deep scorch marks , at least I never had. It’s hard to know what happened with yours without seeing the file. If you’d like, you can post is and I can try to cut it ans see if I have the same issue. (If it’s not too big ) I do a lot of acrylic cutting and have had good success so far.

I find I get the best results with removing the top masking for sure when cutting and it’s a must if engraving. I typically leave the back masking on to help with any minor flashback, but don’t use any cardboard or other backing other than that. There will always be a little melted lip becasue that’s just what acrylic does. You can avoid scorch marks though.

If you can, try and avoid sharp corners with close overlapping lines in the file. If I have something like the corner on the left in the below pic, I’ll ease the corners a bit to avoid over-heating it. Another method is to overrun the lines past the corner like you see in the far right example. If I can’t adjust the file, I try to speed things up to the point of just barely cutting through.

Just to give you hope, here’s an PF yellow cut I was pretty successful with.

[geek2nurse]

Toothpaste is my go-to for acrylic. It’s mildly abrasive and does a good job of polishing up minor fogging and such. Plus it smells nice. Not sure it would be up to taking off your scorch marks, but you probably have some in the house, and it’s worth a try.

[BeamGeeks]

Nope, but I should do that.

[cynd11]

Yeah, for the corners you could try toothpaste applied to a string, then just pull it back and forth in the corner.

[vee]

Thanks for letting us know about this, and I’m so sorry for the late reply. We’re looking into this now, and we’ll update this thread as soon as we have more details.

In the meantime, could you please let me know if you’ve experienced this issue when using other Proofgrade materials, or if you see the same scorching when printing without the piece of card under?

[BeamGeeks]

I’ve seen the issue with red and yellow Medium Acrylic. I tried the 2-ply newspaper trick and that definitely helped get rid of the black lines. I’d prefer to not need anything, but there was a fair bit of melting and scorching without the card/newspaper, of course.

[jaz]

Thank you for your reply.

Have you seen the issue across multiple sheets of Medium Red and Yellow Acrylic?

Could you measure the pieces of acrylic that have this issue with a pair of precision calipers (or another precise measuring tool) if you have them, and send me the values you record? Be sure to remove the protective layer on both sides before measuring.

[BeamGeeks]

There are really two issues. One was the scorching and melting of the material itself. I only saw this with the Medium Red PG acrylic. In the pic below you can see some examples. I know the serif on the font was causing some heat, but really I feel this is unacceptable for PG material. 1 of the bottom 3 had the original backing, one had no backing, and one had a piece of thin card below it. All of them look about the same. The one on top was cut with two-ply newspaper under it based on a recommendation from a forum member. That’s the best by far, but it’s still not perfect obviously. There’s also quite a bit of heat bloom on these pieces which you can see in the reflection. I measured this piece of red without the paper backing on either side, and it was coming up .114 with digital calipers. The piece of yellow I have to hand is .121

The other, separate issue is (or was) some black lines I was seeing in the corners and lettering of this red and, more noticeably, a piece of Medium Yellow PG. I’m still seeing a bit of it on the red, but putting 2-ply newspaper under the yellow completely eliminated the issue. It looks totally clean. I really think there’s something funky going on with this red. Do you think it would be possible to get a replacement piece to test?

[jaz]

Thanks for your reply and for the measurements.

I took a second look at your design and I noticed there are two layers of lettering in your file. Is this part of the design? I suggest removing one of the sets of lettering and seeing if that helps with the black scorching.

Let me know how it goes!

[BeamGeeks]

That’s an old file. I changed up the font, but I added a second pass, slightly offset, to thicken the lines. Again, though, if I can’t do things like that with Proofgrade that seems like a problem. I cut the second pass later in the process to allow the first pass to cool. It works fine in yellow and black.

[jaz]

Thank you so much for the feedback. We’re seeing this, too, and we’ll continue looking into it.