Tips for cutting very small holes in acrylic, please.

[Doug Fisher]

I am trying to cut three .854 mm holes spaced about 4 mm apart in a triangle pattern using .060" thick acrylic with my laser. The holes are not coming out very well defined no matter what I try. If I go all the way down to 20% power and 1.5 mm speed the top side looks decent and I don't have too much flare/excess burning on the back side but the holes are not cleanly defined all the way through. If I go to 25% power I get decent entry holes on the top side, a better percentage of clean cuts through (but still some odd-shaped holes but the back side of the holes is irregular and larger, almost like it heat melted. 27.5 and 30 continue with slightly better through holes but worse exit on the back side. I have turned down the "laser through mode" to be the same percentage as the regular laser power. I even tried turning the "laser through mode" off but that didn't help.

Laser alignment still appears good, air assist is on, laser has 67 degree water going through it. Using RDWorks 8.01.18 for my software.

Thanks.

[Bert Kemp]

your melting plastic so its going to be hard to get perfection.
what is your table? Honeycomb? Try a knife edge or get the material off the table a little.
Is there paper back on the material. try masking the back side.

[Joe Pelonio]

I would put transfer tape on both sides of such thin acrylic, and mist the top with water before cutting.

[Kev Williams]

Echo what Bert said--

You're trying to cut a 1/32" diameter hole (very small) into plastic (that expands and melts) with a .006" diameter drill bit that's few thousand degrees (or however hot they get) --

Simply, that combination of tools, dimensions and materials don't play well together.

You could use the laser to start the holes, to which a 1/32 drill bit or ball-endmill in a drill press would track and finish up nicely....

[David Somers]

Doug,

Silly question, but do you have a CNC available to you? That might make this wayyyyyy easier.
Or
Have you tried a plastic other than acrylic? Polycarbonate for example? Or extruded vs Cast Acrylic? Perhaps PetG?

[Dave Sheldrake]

Simple answer is you won't on that machine. Holes that small are the mandate of laser drills.

[John Blazy]

Ive been amazed at the tiny holes made into acrylic just from pulsing the laser test fire button. Maybe 100% power with just the pulse, and might need multiple pulses, but then you would rather program the pulses by drawing dots in program. Maybe run the program several times at different focus settings to widen out the hole til you hit your .8 mm hole.

[Dave Sheldrake]

Ive been amazed at the tiny holes made into acrylic just from pulsing the laser test fire button. Maybe 100% power with just the pulse, and might need multiple pulses, but then you would rather program the pulses by drawing dots in program. Maybe run the program several times at different focus settings to widen out the hole til you hit your .8 mm hole.

Can't remember on Ruidas but leetro controls have a hole function and a time duration setting for it, .8 is a weird size, too big to pulse and get it straight and too small to interpolate. Soon as you go outside of the depth of field things get funky if the laser doesn't fire at the exact same output every time (most don't) and even 1/10th of a watt will vary the hole size if you are relying on an out of DOF position.

[Lee DeRaud]

All the good suggestions have already been made IMHO.

That said, I've never tried anything quite that small, but I had occasion to cut 1/16" holes in 0.092" smoked acrylic recently: worked fine. The application was alignment holes in a laminated glue-up, and the holes were good enough that the 1/16" drill bits I was using as pins stood up straight when inserted plain-end first into a single thickness.

[Kim Vellore]

You can fill the hole in Corel and try to raster it. Vectoring a hole so small usually gives a oval in my laser.

[Doug Fisher]

Thanks to everyone for taking the time to contribute your thoughts. Here are some answers to the questions asked:

Bert: Yes, it is a steel honeycomb table. I do get some bounceback off of that that I can see on longer straight cuts. The acrylic I am cutting has paper on both sides so I have tried cutting both with the paper and without it. No real difference in the holes themselves but less hazing with the paper.

Joe: Please tell me more about the misting with water procedure. Just in the areas where you are cutting? Is that supposed to keep things cooler during cutting?

Kev: I too was wondering if I was asking/expecting too much. I have had a commercial laser service create nice cuts of this with their big 4'x8' table laser but they have things other than air they blow through the assist that I think help.

Dave: No CNC. I am not sure if this is cast or extruded acrylic. It is the cheaper one so it is probably extruded?

John: Good point. I am trying come up with a way to confirm the correct focus height. While I used the "gauge" that was supplied by the manufacturer to set the correct gap I realized it may not be as accurate as needed because I flipped the lens in order for the round side to face away from the cutting table.

Thanks again for all of the comments. I will continue to work the issue.

[Joseph Shawa]

So the hole are round. What is the tiniest hole you can punch using one pulse set to 100power for just a short time? Do it manually.
Set the Mode to cut/engrave/grade engrave/hole (LaserCut5.3) to hole and run the pattern. I haven't used this so I can't give instruction.
Use a drill after you mark the spots? : (

[Doug Fisher]

I can drill the holes but I was just hoping there was a way to adjust the parameters on my laser so it would do them for me and do them well.

[Dwyane Ward]

Doug,

Not sure my FSL GEN 5 45W settings will relate to your laser but 56% spd and 60% power for the 46 thru 56 drill hole template I use for layout of servo and limit sw and such for my hobby. material is .06" can not remember if cast or extruded.

[Joseph Shawa]

I like it. I need to start labeling my test cuts.