I have a bit of a conundrum - I make (a lot of) little acrylic boxes using an 80w 6040 C02 bodor machine. It works pretty well, but if I'm cutting a 6040 sized bit of 4mm thick acrylic, I get these tiny fractures at 90 degrees to the cut (see photo) (very enlarged, but you get the idea)
They're less than a mm long, but catch the light , so look a bit crap.
Has anyone come across this before? And (better still) figure out how to fix it?
I asked my local laser-cutting fraternity, and they all replied:
"have you cleaned the acrylic with meths/alcohol? - the only time I've seen this is when I've done that".
I wasn't doing this but I was cutting the acrylic on top of a carboard sheet to prevent fire/mess etc... and I think the witches-brew of condensation and toxic-chemicals were being trapped next to the cutt, and were having the same effect as using a solvent.
So when I stopped using cardboard and use a honeycomb (which acts as a fire-retardant) it stopped happening.... so I think this might have solved it.
I do not use the honeycomb table because of the tiny marks left by the grid. I have made a large number of acrylic standoffs with offcuts. 25mm square base with a about 30 x 4.5mm strips set into a tight cutout 4.5mm hole in the base. Probaby more like 4,3mm square hole with the kerf. Just spread them over the table and lay the working material on top. You can just throw them out when they get too damaged by the laser beam.We'll all have offcuts suitable which are only fit for scrap, so it's good to get some use before disposal.
Yea - I used to have terrible problems with honeycomb marks... but they seem not to be happening (touch-wood) at the moment.
The only thing that's changed is that I've gone from a 60w to an 80w tube, and have refitted the air-assist pipe so it delivers a LOT more air. This has had a huge (like 50%) benefit in terms of performance.
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Heat Stress Fractures in Acrylic
