Mirror acrylic troubles

Hello!
I am new to GF and after testing out many settings and masking tape options, I thought I figured out how to cut out my mirror acrylic without any flashback . I put the settings on 155 speed and full power; I put the reflective side down covered in paper masking tape and I have a double sided tape with a protective film on the back. I successfully cut out a small word and when I repeated the same steps for a bigger piece; it left marks everywhere - not sure what these are, the corners are all fine it just looks like maybe something melted on to it? Tried cleaning but it’s part of the mirror now.
If anyone has any input or suggestions, they would be so appreciated!

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Those marks are from too much heat and if you’re using full power, that’s the likely culprit. I cut it with the mirror facing up and I find that a speed of 140 and 85 power generally works well for me. I usually just put masking on the back (non-reflective) side that rests on the tray. I don’t cut mine with the tape on the back though so I’m not sure how that’ll effect things and it may take some more testing to get it dialed in. Another option to prevent flashback from marking the back is to place the acrylic on top of a little cardboard or scrap material so it’s not sitting on the hot metal tray.

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You may also find this posting and subsequent discussion of interest, I think you are seeing the same thing.

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Thanks for your insight! I had actually seen you mention your settings on another thread (I think I’ve read everything on here with the words ‘acrylic mirror’ ) and with the 140/85, but it didn’t cut all the way through for me… I tried aluminum foil underneath and that was very bad, I will definitely give the cardstock underneath a try (this isn’t a fire hazard right? Regular greeting card cardstock will do?). I haven’t understood the logic between speed and power yet so I’ve just been blindly testing everything… I agree that full power is too much heat; but not sure if I should speed up or slow down (I have the pro). I want to find the perfect setting with the reflective side down so I can engrave at same time when need be.

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Sometimes doing more than one pass helps, too.

Some cutters use a “bed of nails” support to minimize contact with the work piece, which helps with flashback.

Any way you go, masking front and back is probably a good idea.

So, yes and no - I mean, yes, layering material will always increase the likelihood of fire - but when you’re cutting acrylic you should always be watching because acrylic, when it flares, flares fast and HOT - so it shouldn’t change your workflow to have the 2nd layer, and having it there should absorb any flashback

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Yeah, reflective foil probably wouldn’t help with the heat issue. :stuck_out_tongue: I get weird about cutting paper or cardboard, but just watch it and it’ll be ok. And yes, cardstock would work. I would make sure to pin things down though to minimize any gaps between material.

If the 140/80 didn’t quite cut through I’d try slowing it to 130 speed first or upping the power to 85 or 90. Just keep adjusting by 5 until you hit a sweet spot.

If you haven’t seen it, this is great info on what all the setting do. Even knowing them won’t beat just testing and playing with things, but it’s a great starting point.