Acrylic cutting vapors popping or combusting
Posted: Wed Jul 15, 2015 9:29 pm
I'm working on a personal project , the project is a Catan board game, inspired by the versions on thingverse but 95% newly designed (only used the sheep and ship lol) anyways none of that is important.
When I'm cutting the outline with 1/4" acrylic directly on the honeycomb bed the laser will hit the honeycomb and sometimes ignite the acrylic vapors causing the whole sheet to pop up blowing out some of the smaller already cut parts. I tried raising the honeycomb off of the bed with a few chunks on angle iron thinking it might pop but the pressure would have somewhere to go instead of up and now instead of popping it just ignites and burns causing a smoked appearance on the acrylic. The same thing happened when I turned on the bed vacuum with the honeycomb sitting on the bed. Adjusting power, speed, and air pressure for the cut assist did not help.
Will a nitrogen air assist stop the ignition of the vapors? Google has failed me, I can't find any references to using a nitrogen assist on any sort of plastic. What sort of CFM will I need for a flame polished edge? I know that too high of a CFM will cause a white edge and too low probably would not induce enough nitrogen into the backside of the cut where it is igniting. Will leaving the paper on the backside of the sheet help with the burning or at least minimize the smoked effect? Will raising the acrylic off of the supporting surface help? if so how would I support the entire workpiece with 1/2" support spacing? the smallest pieces are 1" circles and I wouldn't want them to partially fall with an end sticking up to hit the nozzle. I also don't yet know how to order the cuts to start at one edge and work my way across, doing a perimeter cut first could be bad.
When I'm cutting the outline with 1/4" acrylic directly on the honeycomb bed the laser will hit the honeycomb and sometimes ignite the acrylic vapors causing the whole sheet to pop up blowing out some of the smaller already cut parts. I tried raising the honeycomb off of the bed with a few chunks on angle iron thinking it might pop but the pressure would have somewhere to go instead of up and now instead of popping it just ignites and burns causing a smoked appearance on the acrylic. The same thing happened when I turned on the bed vacuum with the honeycomb sitting on the bed. Adjusting power, speed, and air pressure for the cut assist did not help.
Will a nitrogen air assist stop the ignition of the vapors? Google has failed me, I can't find any references to using a nitrogen assist on any sort of plastic. What sort of CFM will I need for a flame polished edge? I know that too high of a CFM will cause a white edge and too low probably would not induce enough nitrogen into the backside of the cut where it is igniting. Will leaving the paper on the backside of the sheet help with the burning or at least minimize the smoked effect? Will raising the acrylic off of the supporting surface help? if so how would I support the entire workpiece with 1/2" support spacing? the smallest pieces are 1" circles and I wouldn't want them to partially fall with an end sticking up to hit the nozzle. I also don't yet know how to order the cuts to start at one edge and work my way across, doing a perimeter cut first could be bad.