"Flash back" scarring acrylic

[Mike Mackenzie]

I learned a trick that the big laser boys use. We are talking about 1000 watt systems but I tried it and it worked pretty good.

What they do when cutting acrylic is to wet an old cloth towel lay that down on the table and then place the acrylic on top of it without any masking be sure the the towel is wet enough not to catch fire but not dripping wet.

We tried it and it seemed to work pretty good but we really don't have to much of an issue with flashback with the honeycomb so we don't use it to much only when we cut 1".

The other really important thing to be sure of is to keep the honeycomb cells CLEAN when liquid acrylic builds up in the cells it can cause flash points.

[Richard McMahon]

Hi Belinda.
I bought some 1/2" aluminum angle and cut it to the length I want and then lay them on their backs (like a pyramid) spaced as far apart as you like and I haven't had any problems with any burn back on the 6mm Acrylic I have cut.
I remove the paper from small parts as it's hard to get off after cutting but I leave the paper on for bigger pieces.
Rich.

[Andrea Weissenseel]

So far I did not have any problems with flashbacks. I don't place my acrylic directly on the honeycomb - I have a plastic grid, something like a plastic honeycomb about 15mm high, that I got from my dealer when I bought the laser. With that I have the poblem though that the edges of the acrylic are sometimes clouded also the plastic grid didn't withstand my machine for too long so I have it already in a couple of pieces.

A couple weeks ago I read a thread by Dave - he wrote that he uses rivets, that works excellent and Frank's tip with the golf pegs is a very good one too. You can place them on your table wherever you want to and you also have clearance underneath, so your exhaust can blow out the fumes so theay don't settle on the acrylic.

Andrea

[Belinda Barfield]

Thanks for the replies Rich and Andrea. The golf peg system never worked for me as I couldn't achieve a consistent level over the entire bed of the laser (20 x 38). My honeycome grid tended to sag in spots. Problem solved for the most part with a Corian vector grid based on a design on an original grid design by Keith Outten. I added holes for air flow and dowel placement for alignment.