Laser cutter "pitting" on the back side

[mbasch]

We are new to laser cutting and are still learning. We have a Boss CO2 laser. On the most recent project, we have what i describe as "pitting". It is little chips of the acrylic getting knocked out of the back of the cut. Anyone know what might be causing this? It is hard to get a good photo since they are so small and my phone wouldn't let me get that close. I've circled some in red. Any help or advice would be greatly appreciated.

 

[ikarasu]

Are you using a honeycomb table?

That's called flashback. You can raise the acrylic off the metal so the beam doesn't hit it and bounce back, or put a wet cloth under the acrylic to minimize / stop the flashback as well.

 

[mbasch]

Awesome! thanks. Yes it was a honeycomb.

 

[CanuckSigns]

You can also purchase acrylic honeycomb instead of the metal, this will eliminate the issue.

 

[VizualVoice]

if you're like me and get whacky ideas to try and see the grid pattern fluorescent ceiling light diffuser panels at Lowes or Home Depot and think "hey I bet I can use that as an acrylic honeycomb because it's way cheaper", I'll save you the trouble of finding out yourself that your pieces will wind up stuck to it when it melts from the laser beam.

 

[ikarasu]

You can also purchase acrylic honeycomb instead of the metal, this will eliminate the issue.

Hmm.. never thought of acrylic honeycomb.

What thickness is it / where do you buy it from? How long does it last?


I do a ton of acrylic these days and I cover the table with wypall and spray it with water... It works but is a pain, having an acrylic honeycomb I can just drop on-top of my existing one would speed things up.

I guess you could cut your own in theory - might try to cut a honeycomb pattern out of quarter inch... Since it's just going on-top of my old honeycomb it might be thick enough.

 

[CanuckSigns]

Hmm.. never thought of acrylic honeycomb.

What thickness is it / where do you buy it from? How long does it last?


I do a ton of acrylic these days and I cover the table with wypall and spray it with water... It works but is a pain, having an acrylic honeycomb I can just drop on-top of my existing one would speed things up.

I guess you could cut your own in theory - might try to cut a honeycomb pattern out of quarter inch... Since it's just going on-top of my old honeycomb it might be thick enough.

I've always cut them from 0.25" thick acrylic. But I think some people use those plastic grids used in fluorescent light fixtures as a diffuser.

 

[ikarasu]

I bought a pack of 100 golf tees and I usually throw them in the honeycomb, it raises it off the bed by about a quarter inch. Not bad for bigger parts... but I have 300 2"x6" Acyrlics to cut, and I'm not putting 500 golf tees in. I'll cut a sheet of quarter inch out and give it a test - As long as it doesnt warp from the heat, which I imagine it'll be getting very little heat it should work good.

I was thinking of buying a sheet of the protective acyrlic that Co2 Lasers cant go through... CNC out a honeycomb pattern, and theoretically it'd last forever. I havent found a good supplier in Canada that sells it for under a grand a sheet though...

 

[BigNate]

I bought a pack of 100 golf tees and I usually throw them in the honeycomb, it raises it off the bed by about a quarter inch. Not bad for bigger parts... but I have 300 2"x6" Acyrlics to cut, and I'm not putting 500 golf tees in. I'll cut a sheet of quarter inch out and give it a test - As long as it doesnt warp from the heat, which I imagine it'll be getting very little heat it should work good.

I was thinking of buying a sheet of the protective acyrlic that Co2 Lasers cant go through... CNC out a honeycomb pattern, and theoretically it'd last forever. I havent found a good supplier in Canada that sells it for under a grand a sheet though...

let's talk acrylic.... the laser can't go through it? - meaning the laser light is fully absorbed, right?... then the laser will cut through the acrylic.