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View Full Version : How thick an Acrylic can I reasonably cut



Paul Grothouse
12-15-2010, 10:30 PM
I have a 150 Watt CO2 laser, what thickness of Acrylic can I reasonably expect to cut? I have a 2.0" focal length.

I need to build some jigs. Figured I'd ask before I went out and dropped some money on material.

Dan Hintz
12-16-2010, 6:35 AM
You'll have no problem with 1", 1.5-2" may be your limits... I've never had that much power at my disposal to try, but the kerf is going to get nasty at that thickness.

Oh, and above that 1" you'll want something longer than a 2"FL lens.

Robert Farrell
12-16-2010, 9:18 PM
My 30w LaserPro Spirit cut a 1.5" thick acrylic very clean. You should have no problem cutting 2" with 150w.

Richard Rumancik
12-16-2010, 10:22 PM
Robert, there's got to be a typo there - how can you cut 1.5" acrylic with 30 watt?

Robert Farrell
12-17-2010, 6:48 AM
174130174128174128174127174126174125Very slow I was just testing, it was a straight cut. I cut 3/4 through then flipped and finish the cut174129

Dan Hintz
12-17-2010, 7:01 AM
My 30w LaserPro Spirit cut a 1.5" thick acrylic very clean. You should have no problem cutting 2" with 150w.
There's something seriously wrong with this picture... many people with 30W systems have serious issues cutting 1/2" acrylic, and you're claiming to do it on a piece three times as thick? I don't even want to get into the possibilities of catching that piece on fire having to go so unbelievably slow.

Robert Farrell
12-17-2010, 7:42 AM
Dan. what did they say about a picture? Something about a thousand words. With the auto focus on my machine i was dead on, there was no flareup not even a spark. It took about 20 5 seconds passes.As it cut deeper i adjusted the hight of the table, and as i said i was testing I was both surprised and happy. These pics are of 3/8" acrylic.174131174133174132

Dan Hintz
12-17-2010, 7:59 AM
Do you have any clear pics of that 1.5" acrylic's edge? I expect 3/8" to look okay...

Robert Farrell
12-17-2010, 8:16 AM
174138174137174136 The ridge is when i flipped it i was off a little but again it was just a test

Scott Shepherd
12-17-2010, 8:36 AM
I couldn't sell that finish to my customers. Forget the ridge, the striations are bad.

Dan Hintz
12-17-2010, 8:45 AM
174138174137174136 The ridge is when i flipped it i was off a little but again it was just a test
That's what I thought... there's no way I could let that out of my shop without some serious post-processing. At that point, I might as well cut it with a bandsaw (or a scrollsaw) and skip the laser altogether. That will require serious sanding/scraping, followed by a good flame polishing.

Robert Farrell
12-17-2010, 8:59 AM
Scott, it was just a test. I think the reason for the Striation was i did not support the piece that was to be cut and it moved as it cut deeper. If you look at pic #3 on the right the cut is smooth because i supported it when it was flipped. I believe with your 60w you will get a cleaner cut. So the lesson i learned was Support both pieces when cutting.

Scott Shepherd
12-17-2010, 9:02 AM
1/2" is as thick as I have cut with 45W, and even then, I had to do some work on them.

Robert Farrell
12-17-2010, 9:14 AM
I agree with you guys I will not let it out either. I believe the next time i cut 1.5" it will be a smooth cut now that i know what to do and that it can be done. The purpose of the exercise was see if it could be done. PS I did sand and put some flame on the cut piece after and it came out ok check pic #2 on my second post.. Paul I would give it a try.

paul mott
12-17-2010, 12:53 PM
Hi Robert,

Great job with the acrylic.

What is your lens focal distance please.

Paul.

Doug Griffith
12-17-2010, 1:18 PM
My 30w LaserPro Spirit cut a 1.5" thick acrylic very clean. You should have no problem cutting 2" with 150w.

To cut that thick is one thing, to cut it efficiently, cleanly and without flipping is another. Also, in this post, you fail to mention the post processing you clarify in a later post so "very clean" doesn't apply.

Newbies take note: don't purchase a 30w machine expecting to (reasonably) cut acrylic much thicker than 3/8".

Scott Shepherd
12-17-2010, 2:03 PM
I have a sample on my desk from Trotec. It's 3/4" thick acrylic. It was cut on a 400W laser. It's crystal clear, no post processing and the sides are pretty straight.

Robert Farrell
12-17-2010, 3:17 PM
Thanks Paul, It is a 2.5" lens. I just realised if i had taken off the nozzle of the air-assit i would be able to go all the way through with-out flipping

Robert Farrell
12-17-2010, 3:42 PM
All i am saying guys is the answer to the first post by Paul Grothouse if i could cut 1.5" clean cut or not with my 30w he can more than likley cut it with his 150w and get an acceptable result. Lets not stray from the original post. Merry Christmas to All.

Dan Hintz
12-17-2010, 4:16 PM
Robert,

I think we're just trying to clarify that your earlier statement of a 30W system giving a "clean cut" is nowhere close to being realistic. Plenty of newbies will read this thread in the coming years and we don't want to give them a false impression about the capabilities of a machine, particularly since the most common question for laser newbies is "How much power do I need to cut 'X'".

A second point to keep in mind is power is not all of the equation. At 1.5-2", we're talking about a serious amount of kerf to deal with, which means a longer focal length lens, even with the helpful waveguide properties of acrylic. I wouldn't want to cut a 3" thick piece with a 1kW system unless I had an 10-12" focal length lens.

Robert Farrell
12-17-2010, 5:29 PM
174205174204174203174202174201Ok This is a cut without flipping.

Dan Hintz
12-17-2010, 5:56 PM
Yep... and it will need a lot of prep sanding/scraping before flame polishing.

Scott Shepherd
12-17-2010, 6:47 PM
Robert, I have to give you credit, that's the thickest piece of acrylic I have ever seen cut on a CO2 laser, not to mention a 30W laser. That's pretty remarkable.

If I had to cut that, I'd be using a CNC router, as it would be much faster and require less edge work to finish, but I do give you credit. I cut a load of 1/2" thick some time ago and it appeared to be at the very limit of what I could cut, as sometimes it wouldn't cut all the way through. Any slower and it would fry the bottom edge really bad. It would actually blister it. So if I could barely cut 1/2" thick with 45W and you're cutting that thick with 30W, you're doing far more than I could!

Very interesting.

Lee DeRaud
12-17-2010, 7:21 PM
Robert, I have to give you credit, that's the thickest piece of acrylic I have ever seen cut on a CO2 laser, not to mention a 30W laser. That's pretty remarkable.
At this point, I have to point out that the key word in the thread title is "reasonably".

Double-digit passes, sanding, and flame polishing all exceed any definition of "reasonable" I'm willing to accept.

Robert Farrell
12-17-2010, 8:43 PM
This is weird no one gave any advice to Paul Grothouse

Keith Outten
12-17-2010, 9:41 PM
Paul,

At 150 watts you have one of the most powerfull laser engravers here at The Creek. Xenetech has a video of their 60 watt laser clean cutting a one inch thick piece of acrylic, your machine will surely cut much thicker material.

As the price of acrylic goes up real quick when it gets over 1/2" thick I doubt many here could afford the material if they could cut it :)
.

paul mott
12-18-2010, 2:53 AM
Thanks for the info Robert, you have shown that cutting through 1.5" form the same side with such low power is possible (I didn't think it could be done) and I have learn't something here.


This is weird no one gave any advice to Paul Grothouse

This forum is rather unique in so far as "thread hijacking" (exactly what I am doing here) appears to be the norm and unlike other forums not considered to be rude.

Paul.

Scott Challoner
12-18-2010, 2:50 PM
This forum is rather unique in so far as "thread hijacking" (exactly what I am doing here) appears to be the norm and unlike other forums not considered to be rude.
Paul.


It's because we're all like a big family here, talking over the top of one another like at a big family Christmas dinner. :)

Frank Corker
12-18-2010, 5:14 PM
I have to admit 1 and a half inch of acrylic with a 30w laser is amazing, yes it was in multiple passes, but he is proving that his machine can do stuff that the books say that he can't. Theoretically my machine is not supposed to be able to cut 20mm acrylic in one pass, but it can! Not only that, but with different tests I was able to cut 20mm at 1 speed, 5000 frequency and 75% power and it was as smooth if not smoother than the 100% power.... that's not supposed to happen either. Maybe not the greatest finish but for one pass it was pretty bloody amazing. So the books will tell you one thing but the lesson shown here is, try your machines for yourself and test them to the max, you might be suprised at what you find.

Paul Grothouse
12-18-2010, 10:17 PM
Thanks for the advice guys 3/4" will be more than plenty for me. It's hard to machine the arylic in our CNC without cracking it. Lexan works much better for machining, but it is big bucks. Plus the laser is much faster.

Doug Griffith
12-19-2010, 12:39 PM
Thanks for the advice guys 3/4" will be more than plenty for me. It's hard to machine the arylic in our CNC without cracking it. Lexan works much better for machining, but it is big bucks. Plus the laser is much faster.

With the proper cutter, tool path strategy and speed/feed settings, CNC machining should work fine. Your only issue might be the inability to fixture thin walls or small parts. An Onsrud single-flute downward spiral cutter may be what you need. You are right. The laser is much faster. Especially if kerf angles aren't an issue.