Cutting 3/4" Acrylic

[Paul Phillips]

Hi guys,
I discovered something that my laser can do that I wasn't sure it would be able to. Successfully cutting through 3/4" Acrylic in one pass and look clean enough for some painted letters. I had a job come in that needed a lot of detail that I would not have been able to achieve with my CNC machine so I thought what the heck, it's worth a try, I have 150watts, let's see what this sucker will do! The results were surprisingly good. There was some distortion visible close up but, a little sanding and some paint and the end result is more than acceptable. Here are some close-up pics of the edges, I tried to get a profile shot so you can see that the amount of distortion was not too bad.
Picture1 001.jpgPicture3 003.jpgPicture1 003.jpg

And here are the final results with some paint.
Picture1 005.jpgPicture1 004.jpg
For those interested, the settings I used were: 100power, .5 speed, 1000ppi. I turned the air assist up to 40psi so I could make sure it was blowing through the material. The actual thickness of the material was about .695, and I set the focus at .625.
I sure am glad I got the extra power up front, I cut a lot of Rowmark but when I cut any acrylic, or pretty much anything else, it definitely cuts fast. I cut some 1/2" Maple last week and it came out very clean with little charring.
My only question after this is, how much cleaner and at what speed would I be able to do this if I bought the 4" lens? I realize that it has a longer focal length but as I understand, it also takes a lot more power because of the larger beam. Anyone have any experience with using 4" lens on similar material?
Thanks,
Paul

[Dan Hintz]

With that kind of power, it doesn't surprise me in the least you can cut 3/4". Next time, try focusing about 150-200 mils into the material, see if you get a little less kerf variation. Play with different values, but you shouldn't have any problems with cutting 1"...

[Martin Boekers]

Nice work! what type of paint did you use?

I wish someone would come up with a good high-density foam
that is laserable. Similar to the sand blast signage material.

[Paul Phillips]

Martin,
we use the Matthews paint system which for those not familiar with it, is the the highest quality sign paint you can buy. It is a catalyzed automotive grade urethane paint formulated for the sign industry. We do a lot of custom aluminum signage which it is ideal for but it also works great for acrylics and just about anything else you can put a good primer coat on. The best part is that we have the mixing station and a color database for mixing and matching literally thousands of colors.

I agree with you though, a nice inexpensive, thick, light but sturdy foam like material that lasers easily would be great. Hurry, someone invent it! ;-)

[Martin Boekers]

Martin,
it also works great for acrylics and just about anything else you can put a good primer coat on. The best part is that we have the mixing station and a color database for mixing and matching literally thousands of colors.

I agree with you though, a nice inexpensive, thick, light but sturdy foam like material that lasers easily would be great. Hurry, someone invent it! ;-)

I think in the time being I'll stick with Fusion!

The more lasers out there the more viable it becomes for new products to hit the market.

Someday we may see it!

[Frank Corker]

Personally I think with that kind of fire power you should well be able to cut this and a lot neater. The distortion mid way before you get to the bottom drag is caused by the laser being moved too quickly along it's course. Slow it down to about 2 (yes it will take longer, but less rubbing down to be done afterwards) and you should see little or no striation marks

[Paul Phillips]

Thanks for the tip Frank, I'll give it a try.
Paul

[Paul Phillips]

Frank,
I tried your suggestion and ran it at .2 but it was a bit too slow and caught fire so I tried it again at .3, a little fire but not as bad, tried again at .4, no fire and a little bit cleaner, this seems to be the sweet spot for my machine. Thanks for the help, it's always good to learn something new.
paul

[Scott Shepherd]

Paul, I posted this in another thread, but it would apply here as well. On your "Raster" tab, make sure Image Density is set to "6". On your vector tab, make sure the "Vector Performance" is set to "Quality" (all the way to the left).

I know it doesn't make sense to have the Image Density set to 6, since that's a raster setting, but it affects the quality of the file that is sent over.

If you're not already using those 2 settings, change them and try it again and see if it does any better.

Oh, and you might turn that air down too. Some times it can cool the material too fast and cause all those striations. Try 10-20 psi for that thick.

[Paul Phillips]

Scott,
Thanks for the tips, I tried what you suggested, I did already have the "Vector Performance" set to "Quality", but it didn't make it any better, in fact it left more noticeable striations on the bottom of the cut, I could actually see the beam cut through the material and leave an "S" shape as it cut, with the tail of the "S" leaving the striations. I'm thinking this is because of using less air? Maybe the higher air pressure helps blow the molten Acrylic out as it cuts even though it cools it faster? It wasn't a big difference but noticeable. Still, the overall quality is better than I thought it would do with only a 2" lens. I'm still interested to know if anyone cuts 3/4" Acrylic using a 4" lens and if there is a big difference in quality?
Thanks,
Paul

[Kevin L. Waldron]

Paul,

We have a Universal 150 watt ULS 12-175 and we have the ability to use gas and air. If you want to stop most of the fire..... go to some gas like nitrogen etc. We use a 4.0 lens almost all the time and we can cut 3/4" material but it requires 2 passes with the 4.0 lens and typically we reverse cut the material that is 3/4" thick. We regularly cut 3/16" -1/4" at 85% power and speed of 8 and a ppi of 600-800 and we typically set the z height to 15% less than actual thickness ( we use green edge acrylic ). 4.0 lens does require more power....... With the 4.0 lense the air cone is not very effective ..... the tube air works somewhat better. ULS will fix you a special 3.0 lens if you request them to ( standard extra lens for our model is a 3.0 but they made us the 4.0), which would give you more distance away from the head an a little better power advantage. I personally would recommend getting more distance away from the head if your going to be cutting this thickness and the chance of fire / flare-up, and heat ( first thing to go will be the Auto-Focus..... we know!.... even though we don't use auto-focus.......for sure don't try the HPDFO lens!!). (We also have ULS 460 with 60 watts and can cut 3/4" material.)

Hope this helps,

Kevin