Acrylic: 1/8" - Raster, then Cut - Care!?!?!

[Gary Gilbert]

Hi folks,

I have a job that requires 1/16th inch of acrylic to be engraved away, leaving a flange for mounting, then cutting the outside.
Note: This acrylic is not clear - it is gray or bronze tinted for small panel windows.

I have seen a post about fire, danger, etc.
I do not have air assist on this machine.
Should I work something out so I do?

What precautions should I take?

Should I spray the paper backing with water? Maybe spray only for the cutting part?

Any ideas on settings?
Should I multi-pass the engraving to avoid flame ups?

Thanks and regards,

Gar

[Kevin Huffman]

Fires are usually caused by 1 of two things.
1. No air assist, something to keeps the flames out. (this is usually not the cause though).
2. Walking away while it is engraving. That is how every story I have ever heard about a machine catching on fire started. I went to ........ and the laser caught on fire.

If you stay by the machine and watch it carefully you shouldn't have any issue with this. Most lasers have safety switches on them. If you open a door the laser will stop firing. If you see a fire start to get out of control simply open the door and remove the burning piece from the machine. Put it out, outside of the machine.

I am not sure about the air assist. All the machines we have, have it built in.

The main precaution I would take, it not leaving it unattended.

I have never been a fan of wet anything into a laser. The heat the laser makes, turns water into steam and steam can possibly damage the optics of the machine. I have hear of people using all kinds of different applications to make stuff come out and none of them has said anything about optics damage. Not say it doesn't happen, just I haven't heard about it.
Since you do not have air assist, I would suggest multiple pass. Start off with a higher speed and lower power. Makes a couple of passes increasing the power, until you get to 100%. Then start lowering the speed. If you ever find a speed that starts creating a large flame, you have found the limit. Speed it up until you don't have the flame and keep making passes until you get the desired depth.

[Joe Pelonio]

I have never seen any kind of flaming when engraving, so that part, which will probably take several passes to go that deep, should not be a problem.

The only time I have seen flame cutting 1/8" acrylic is when it's really close to the edge so it gets additional combustion air from the side. This is even with the air assist. Kevin has a good suggestion, but I'll add that you should try to keep the parts about 1/2" apart and 1/2" from the edges of the material even if it means more wasted material.

[Mike Null]

Gary

I think you've been given good advice by Kevin and Joe. I would add that it may take as many as 5 or 6 passes to remove the 1/16" of material.

If you have some spare material by all means experiment with your settings.

[Mike Hood]

Got a router? Might be easiest to cut the material with the laser, and then route the bevel in afterwards?