cutting clear acrylic with a 445 diode?

[Blarg King]

So using a Co2 cutter at work really has me wanting a laser cutter of my own, but due to monetary and space constraints I think a Co2 cutter is out of the question for the time being. So the next obvious choice would be a nice diode laser, probably a 445nm since those are the most powerful diodes you can get easily.

Thing is though, I'm really digging doing acrylic engraving with the Co2 laser, but I tried even putting a mark into some acrylic scrap with my 1.7 Watt 445 and it didn't do anything except go through the acrylic and burn my desk.

Is it a matter of power or lack thereof, would one of those beefy 7 Watt 445 diodes work? Or is it more with acrylic being pretty transparent to 445 and I would need an obscene amount of power to etch acrylic with 445 light?

Or is there some other laser type besides a diode or Co2 that would be better suited? I imagine a YAG could do it, but thats probably more of a challenge than a Co2 laser.

Would an IR diode be better suited perhaps? And if so, anyone know a source for high power IR diodes?

Thanks!

 

[paul1598419]

I believe you are stuck with the fact that 445nm light will always be transmitted through clear acrylic or glass. You won't be better off with 7 watts of 445nm light than you were with 1.7 watts of it. I have a large sheet of 1000 l/mm diffraction grating on plastic and many watts of visible light goes right through that with no problems.

 

[Blarg King]

That's what it's looking like sadly from what little I can find about it. Looks like Co2 is the only real viable way of cutting it. Apparently UV below 300nm would work but deep UV means either an expensive and exotic diode or an expensive and exotic gas laser.

Ah well. Maybe coating the acrylic with a thin dark paint or something would allow enough energy to go into the plastic? I'll give that a try.

 

[RA_pierce]

Adding a dark coating wont help much. The laser will ablate the coating and still pass through the plastic.

 

[Cyparagon]

Yes, acrylic doesn't discolor as much as it burns or melts, so it might be tricky. Certain coatings would be resistant to vaporization. Graphite perhaps?

 

[Blarg King]

Yeah I was thinking of trying to mix some fine graphite powder with a clear base of some kind to make a dark paint.

I don't expect it to work well, but the only way to know for sure is to try.

 

[GSS]

I wonder how it would burn if you put a dark coating on both sides of the sheet?

 

[Blarg King]

I wonder how it would burn if you put a dark coating on both sides of the sheet?

Thats a good idea. Ill give that a try too.

 

[WizardG]

Yeah I was thinking of trying to mix some fine graphite powder with a clear base of some kind to make a dark paint.

I don't expect it to work well, but the only way to know for sure is to try.

It's called aquadag.

 

[CurtisOliver]

The problem with cutting clear acrylic with visible wavelengths is that even if you do make a mark on the surface. Clear acrylic turns frosted white, which reflects visible light still. You’ll struggle getting the power density absorbed high enough to cut through. It’s not impossible but is impractical.

 

[Blarg King]

Alright, I gave a couple types of coating a test.

From left to right: "wrought iron" black paint, black acrylic paint, white acrylic mixed with graphite, and clear nail polish mixed with graphite.

After hitting each area with my 1.7 Watt 445:

After washing off the paint:

So not the greatest quality photos, but you can still see the laser did manage to decently etch into the acrylic with the "iron" black, black acrylic, and graphite. The best performer was definitely the graphite, although the nail polish doesn't easily wash off like the other 3 did. Perhaps a better clear base would be more ideal. Both the "iron" black and black acrylic did equally well, and the white with graphite did not work at all.

So it seems that with a simple black coating it is possible to at least engrave acrylic with a visible spectrum laser. I did notice that even after the paint had burnt off the laser was still able to keep burning the acrylic underneath, so with a more powerful laser it might actually be possible to cut through.

 

[paul1598419]

Yeah the best solvent for fingernail polish is acetone. Unfortunately, it also dissolves acrylic too.

 

[hakzaw1]

I have cut a lot of clear plexiglass and always used a powered jigsaw. (it is easy to mess up if you move the plexi too fast or too slow (it melts)

If you try again' myb marking the cut line on both sides of the acrylic where you want to make the cut with a black sharpie. (or get a powered small jigsaw) a hand hobby jigsaw would work fine but take a longer time IMHO