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Pete Thomas(UK)
11-20-2008, 6:46 PM
Hi all. I have liiked through the past posts to see if I could find an answer to my problem. No luck.

I bought some 3mm mirror acrylic a couple of months ago. Today I wanted to cut out some animal shapes for a local primary school fair. Problem no one was that the acrylic was not flat. It had cupped, bent in both directions. I tried heating it gently with a hot air gun and applied a bit of pressure to straighten it out, it did help a bit. When I had vector cut the acrylic two months ago the back surface was getting marked with smoke damage. I thought that putting transfer paper on the back would help. Disaster, when I peeled the paper off it took the plain mirror backing off as well. This was in the area that I had warmed with the hot air gun. Not a good idea.

I started to vector cut the acrylic and then noticed that the reflective surface was blooming, losing its reflectivness away from the cut edge for about 3/8".

Is this caused by moisture? Does acrylic absorb moisture slowly. I still have most of an 8 x4 sheet that at the moment I cant use. Any suggestions what I could do?

Joe Pelonio
11-20-2008, 6:58 PM
I think the heat caused the transfer paper to stick, and probbaly the same for the peeling edges. There are several levels of transfer tape, always use low or medium tack, not high. I find that it cuts cleanest if you do it transfer taped face down, silver up.

As for the warpage, that's very typical of acrylic, especially when not stored flat. Usually for cutting most "regular" acrylic that is not so much of an issue, but for detailed engraving can really mess it up.

Your best plan is to cut the full sheet to the size that fits your machine immediately when you buy it, then stack flat to store.

Frank Corker
11-20-2008, 8:26 PM
I have cut quite a lot of acrylic mirror without issues. If it's peeling it might be that the piece is getting too hot, either from you going way too slow or air assist not doing too well. Reduce your power by half and see if it cuts through, if it does, then you have been going too slow. Try more than one pass to cut but lower power settings.

Marc Myer
11-21-2008, 1:08 PM
I just discovered an unexpected result of vectoring acrylic mirror, as has probably been mentioned here before.
It's lovely, but I used a black spray paint on the back to darken the letters. The spray got too close to the edges and the chemical interaction caused stress fractures.
So that's another on my lengthening list of 'Dont's.'

Scott Challoner
11-21-2008, 1:57 PM
Marc

If I spray acrylic after engraving, I use Krylon H2O paint. It's a water based latex that doesn't cause the crazing like solvent based paints.

Frank Corker
11-21-2008, 3:58 PM
I'd always recommend that you use acrylic paint. It was made for it.

Benedict Roussos
11-22-2008, 2:03 PM
when an acryllic sheet is cuped try to fix it on your table with a sticky tape. It really works. I had the same problem with mirror acryllic and I solvee it that way.