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Sean Bullock
03-07-2008, 5:09 PM
I have a job coming up that requires cutting and engraving PETG 3/8" thick. Never worked with this material before. How does it behave under the laser? Comments? Suggestions?

Brian Robison
03-07-2008, 5:25 PM
Hi Sean,
I wonder what the heck it is.
If I had to guess it would be Poly Pro with talc and glass fillers?

Scott Challoner
03-07-2008, 5:43 PM
Are you sure it's not supposed to be PETG? I just got a sheet of PETG to play with, but I haven't tried it yet. It's supposed to cut nicely and is called "an economical alternative to polycarbonate." I believe it's a type of polyester.

Brian Robison
03-07-2008, 5:50 PM
Now that would be.....are you ready?
Polyethylene Terephthalate Glycol Comonomer

Scott Challoner
03-07-2008, 5:57 PM
Of course. Everyone knows that. :D

Mike Null
03-07-2008, 6:24 PM
And it cuts sloppy. Melts easy.

Doug Griffith
03-07-2008, 7:15 PM
I have cut a ton of PETG and it is very sloppy. Smells pretty bad too.

Larry Bratton
03-07-2008, 7:18 PM
I've never tried PETG, but I was told by a representative of a company that makes it, that it melts when lasered and is not good product for it. Subsequently, I took his word and never tried working with it.

Jack Harper
03-07-2008, 8:17 PM
I too have tried cutting on the laser and found the same results. It cuts quite nice on the waterjet though.

Sean Bullock
03-07-2008, 10:02 PM
You are absolutely right. I must have misunderstood the gentleman as I was discussing his project over the phone. PETG it is.

So, here is another question: why would he want to use PETG (keep in mind he is an optical engineer) for a wave guide, ex. edge-lit sign, rather than use acrylic? What properties does PETG have that might create some advantage over acrylic? Or is he just using it because he doesn't know what else to use?

Mike Null
03-07-2008, 11:09 PM
If he's an optical engineer he knows how to check the characteristics of materials. It is an FDA approved material for food contact for whatever that's worth.

It is also very much resistant to certain chemicals which was the spec of my customer.

This is Brian's field so I'm sure he can offer documentation.

Richard Rumancik
03-08-2008, 12:25 AM
I have cut PETG .062" thick. It will cut but tends to turn a bit whiter at the cut line, in my experience. The edge tended to stay a bit sticky for some reason. There will also be some raising along the edges. For a "light pipe" application acrylic is commonly used and will laser with a glossier edge than will PETG. I don't think you will have good success with trying to engrave it. You can make a mark but it won't have a good appearance.

Although it may not be a common name lots of soda bottles are made from this material.

Martin Reynolds
03-08-2008, 3:50 AM
I cut lots of PETG. It is a dirty material, and your laser will need frequent cleaning to catch all the white dust that settles. Plus, you need a good ventilation system as the smell can get around a bit more than acrylic odors. Edge quality can be very nice, but it is also very sensitive to flashback and air assist.

I would not expect much from the engraving, but it is worth a try.

It is a very tough material, but it also scratches easily.

Bill Cunningham
03-08-2008, 2:34 PM
Now that would be.....are you ready?
Polyethylene Terephthalate Glycol Comonomer

On no!! Not another one of those chemical names!!:D it took me quite a while to remember pentaerythritol tetranitrate (PETN)!! Although cutting it on a laser could be a real blast :eek::D

Sean Bullock
03-08-2008, 2:48 PM
I cut lots of PETG. It is a dirty material, and your laser will need frequent cleaning to catch all the white dust that settles. Plus, you need a good ventilation system as the smell can get around a bit more than acrylic odors. Edge quality can be very nice, but it is also very sensitive to flashback and air assist.

I would not expect much from the engraving, but it is worth a try.

It is a very tough material, but it also scratches easily.


Can you suggest a setting for the cutting? working with 3/8" thk material.

I will be engraving, but only to about .004". He wants a frosted effect for the engraving much like one might get with acrylic, so I figure I will go about 80% black on the graghic. How does that sound?

Brian Robison
03-10-2008, 9:38 AM
I'm guessing it will try to melt back together after you laser through it. This is just a guess but I think I'd try a low frequency, maybe around 400 to start. Also be careful, polypro and polyethylene are the materials that will stick to your skin when melted. :rolleyes:
I think your right too, acrylic would be optically much better.
BTW, I lasered some polypro "squeeze bottles" a while back, it took way more power than I would have thought, but the result was very interesting, it gave a "swelled up" look to the rastering. Pretty cool.

Sean Bullock
03-10-2008, 1:24 PM
I'm guessing it will try to melt back together after you laser through it. This is just a guess but I think I'd try a low frequency, maybe around 400 to start. Also be careful, polypro and polyethylene are the materials that will stick to your skin when melted. :rolleyes:
I think your right too, acrylic would be optically much better.


I talked to the engineer since my last post. He suggested that the PETG had the specific optical properties cut at the right size, as well as its FDA properties.



BTW, I lasered some polypro "squeeze bottles" a while back, it took way more power than I would have thought, but the result was very interesting, it gave a "swelled up" look to the rastering. Pretty cool.

I have heard of this process. I believe it is called 'foaming'.

The occurs when the surrounding temperature is raised enough to cause the polymer to degrade to gasses, forming small bubbles.

What settings did you use?

Brian Robison
03-10-2008, 2:23 PM
It's been a couple years. I know it was 100 power and pretty slow speed. I'll look around and see if i have the numbers.

Brian Robison
03-10-2008, 2:25 PM
Looks like 100% Power 20% Speed, probably 300dpi.

Sean Bullock
03-10-2008, 6:13 PM
Just a heads up on how the project is going.

1) This material smells really bad!

2) I tried cutting a 3/8" thk sheet. No good. Just as was predicted, there was much reflow. Areas where the laser passed over simply rejoined and solidified. Thinner material may cut better. I might suggest a high power and high speed to get it done in one cut.

3) Lots of browning of material at cut edge.

4) Engraving the surface went pretty well. I engraved at about an 80% black to give the area some refractive properties. Will know later this week if that worked out well enough for the client.


Overall, this is not a material that I would want to work with on a regular basis, but as my luck would have it they seem to want me to work with this material on a regular basis. At least until the the project is fine'.