Cutting PETG for face shields

So, it appears i’ll have a large order of PETG parts to cut.
My laser is still in pieces (rubbish engineering out of the box), so i’m kicking into high gear to get it fixed (or at least putting it back into somewhat operable condition) for this.
My question is regarding the material, not the machine itself.
Parts in question to be cut from PETG sheet, 500micron(0.5mm) thick.
Machine is 900x600mm bed 80w sustained (100w peak) CDWG tube, ruida 6442s controller.
I havent cut PETG before, but as times dictate i need to help to get rid of the big nasty COVID-19.

Any advice on how to proceed ? Speeds/power, pulse frequencies etc.
Anyone here cut something like this ?

Newbie, here. I’m here for another problem for my new 50watt laser.
I’ve been using RDWorks to cut my 0.5mm sheets of Face Shield PETG. The settings I use are: Speed=35, Power=30
I cut two side by side shields at a time an only run one sheet per pass. The run time is 1 minute.
First time using this machine so the values may be different for more experienced users.
Ok, now to see if I can solve my Lightburn problem. Or user problem.

You’ve mentioned some settings, but you haven’t mentioned any problem. What is the issue?

Fast. I’ve only used a co2 glass tube laser before, and I don’t think we change pulse frequencies at all.
EDIT: I see that’s just a glass tube too, but with more metal on the end. What’s the difference there?

What do you normally cut?

A post was split to a new topic: Problem getting Ruida to cut

I had this laser for a year and it was not cutting properly, so i redesigned Y, need to change belts, beef up motors etc, but thats different story (major resonance, bad arc cuts etc…).

As for frequencies… Today i read an article that cutting PETG you need to lower frequencies to 2-3khz, same as with paper. Less charring/less burning, kinda like perforation mode(which i’m yet to try in LB). I did run my machine at lowest 2khz allowed in LB (at the time i tried, maybe it changed) and it worked wonders on heavy paper, but i couldnt keep cuts straight due to machanical shenanigans (resonance in arcs and off-90-degree cuts).

Just asking for general experiences with PETG and maybe some on point advice about this specific material.

#Edit# It is a glass tube, DCWG 100W peak (80W sustained). Normal operation of CO2 lasers today defaults to 20kHz.

#Edit2# Article i read:

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I cut 5 mil PETG for face shields at 175 mm a second with power at 24% on my 80W glass tube CO2 laser. Air assist was dialed back to a minimal amount just to keep the lens clean. I had to take my honeycomb bed out about every 75 sheets (150 pieces) to clean off the white dust. At that point, the buildup was getting thick enough that during flashback it was getting deposited back up on the PETG. The end-users probably didn’t care but it bothered me!

Also, another fellow volunteer pointed out an easy tip for handling PETG which can “float” around when stacked together and thus make it hard to keep all the sheets in the stack aligned. Use nails or dowels inserted into a piece of wood spaced to match the holes in the face mask. This makes for easy “pin registration” of the pieces so they are easier to keep in orderly stacks.

Do you cut straight on honeycomb ? What about flashback ?
Why air assist minimal ?
Good tip on cleaning bed.
As for fastening, i can use neodymium magnets to stick things to the honeycomb. Its steel.

If you cut multiple sheets, dont they stick together ? As in melt-welding to underlayer ? PETG is melty afaik.

I started with wanting to use my laser to cut shields, tried one, then redesigned the shield. I’m now making face shields from 1/2mm polycarbone (BUT) not cutting with the laser, refined the design to use a single sheet 8X12 with 4 bends. Cuts are score/snap, and I don’t have to cut sheets down to fit the laser.
Love my K40 but sometimes there are better ways.

Do you cut straight on honeycomb ?<<

What about flashback ?<<
Not a problem until the cutting dust build up that I mentioned.

Why air assist minimal ?<<
You don’t want the white dust being blown back down on to the PETG.

If you cut multiple sheets, dont they stick together ?<<
I did not cut multiple layers at once for the reason you mentioned.

I am at present 3D printing Covid-19 face shields but they are too slow at 1 per hour, so looking for other cheap technologies I can use in my home so I’m not even sure if laser, knife cutting machines are suitable. Your solution looks particularly interesting, can you explain a little more about it please?

#Work Update 1#
Well, it has been a fun day. ~400 mask visors cut in about 3 hours. Three separate tests, hour long, changing method of loading, learning to be efficient.

Test 0 (no production cutting): Just figuring speeds and power. Settled on cutting at 190mmps @55% power. Note, that my CDWG tube has been limited in controller to 80% output, before the actual power setting is assigned to the cut, which makes it 55% of 80% of 80W total available power. I know its a bit confusing as i dont have amp meter installed at the moment and dont want to accidentally overdrive the tube. Meter goes in sometone this week.

Test 1 (First production run, 1 hour): I got a portion of the big roll rewound onto smaller tube to help me with setting up the production, as the whole roll weighs in excess of 300kg and is not really manageable for a single old me (2 burly blokes maybe :D). Set up a simple stand made of 2 trestles and a steel pipe through the centre of the roll. Only can use close half of the bed as Y motor is getting in the way of flattening fed in material, so had to resort to doing only 2 visors at t time, although 4 would fit just fine.
Used 20mm flat neodymium magnets for hold downs while cutting. 4 at the corners on the outside of the cut, 2 inside to keep material flat. First hour yielded 80 mask visors.
Comments on first run - OW MY BACK. Machine is too low for comfortable operation, it takes a while to setup new chunk of PETG and position magnets, all bent over.

Test 2 (second production run, 1 hour): Figuring out particular problems while cutting. One of which was reloading/positioning/clamping speed, repeatability, etc.
Magnets were not particularly good solution as theres lots of them to position, guestimate or “frame” every time. Decided to mask off some bits on the honeycomb to help me with positioning next cut in a roll, aligning/clamping went quicker after that.
Also, the fact that i need to manually move the head away from “start position” to pull the roll down without hitting it was anoying me some. Have to figure out a way for the head automatically move away in x direction after the cut to let me pull on the waste and roll down without hitting JOG RIGHT button on the machine…
Extraction was a major time wasting factor as i needed to wait for smoke/dust to clear until lifting the lid. On that later.
Still too much time wasted (in my opinion), but was getting practice in.
Managed 100 visors this run.

Test 3 (Production run, 52 minutes, with improvements mulled overnight): Last thing i did after test2 was to run a laser with lid completely up, disabled hatch safety switch with a magnet (here’s stupid :smiley: ). Nearly all of the smoke went into the table right away, none of that lingering when hatch is down. Some wisps escaped but it was MUCH better completely open, even though i do have a chunky gap under the lid with it closed.
The whole smoke being slow situation prompted me to ask extraction questions here. Thought things over, nicked two chunks of 160mm sewer pipe, taped it in place of 160mm corrugated+100mm corrugated+120mm rigid pipe combo and put an external blower to suck on the end of that pipe. It is not sealed to the pipe at the moment - no flange on intake of that fan (it’s a small bouncy castle blower, 300W @240V). This whole new setup helps IMMENSLY.
Another improvement i made was to get rid of the magnet placing step, as it was eating into the run time and making my back go all OWWW… So, i took visor design, stepped it inside by 20mm and cut it out of 6mm acrylic to make hold-downs. Now i only got 2 things to place on bed instead of 6.
Ran this 1hr(*) run with hatch wide open, new extraction, new hold-downs.
Asterisk means i didnt manage one hour because i ran out of small roll 52 minutes in :smiley:
This run i managed to near double the production to 180 per hour (well, 52 minutes).
Its obvious open hatch and hold-downs cut my cycle time in half.

Clean cuts. Lots of white dust though.
Dust only settles, doesnt stick, so only some warm water is needed to rinse visors away.

Today got the full remaining roll. Holy cow, that thing is heavy. Will do minor adjustments to some things and will probably manage 200+ visors an hour, running with hatch open, using hold-downs and having plenty of uninterrupted material to work with. Will report back after i finish later today.

Some pics:

On the left 2 stacks 100 each, middle 180something, right no idea :smiley: Thats sum total over all the tests i described here. White dust comes off with water, condensate not sticking.

Extraction “before”. Lots of “whatever” taped together.

Extraction “after”, all 150+mm diameter, straight.

Blower thing sucking on the exhaust. Not taped/sealed, just sits against the pipe. No flange, will have to come up with something.

This is my setup as it stands after Test3, right before burly dudes with 300kg roll of PETG rocked up to my gate…

So, this is how it is now. Anyone got any suggestions ? Comments ? Advice ?

Take note that PETG creates the following hazardous combustion products:

nitrogen oxides (NOx)
carbon monoxide (CO)
carbon dioxide (CO2)
hydrogen cyanide (HCN, prussicacid)

When using PETG for 3D Printing, the material is only being melted and extruded (not combusted). Laser’s on the other hand, well you’re making hydrogen cyanide. ABS does this as well.

Sere are some MSDS on PETG indicating what I have just shared:

Listed as a banned substance for use in their lasers:

The level of HCN is negligible. Acrylic also emits HCN when cut. Same negligible amounts.

If I had to do mass-production…

Can you place the roll behind the maschine and feed material through the machine? Hopefully!


I would create an outer frame, perhaps out of MDF (weight). As thick as possible by watching my clearance of the cutting head.

I would mount this frame with some quick release bolts (the style similar to the quick disconnect for bicycle wheels (essentially with an excenter head). Using large washers underneath to not to damage your homecomb bed.


Drill holes through the MDF for these excenter bolts + some kind of spiral spring strong enough to lift the MDF just a little / relieve the pressure enough.

Here the sequence of parts from above to below:

1–Excenter head bolt.
2–Washer larger than the hole in the MDF frame (bolt + spring + clearance) to firmly apply pressure to the MDF.
3–Appropriate spiral spring.
4–Washer on top of the honeycomb (to mitigate the pressure from the spring. Perhaps you need to
counterbore a little the bottom of the upper frame to avoid a gap.
5–Washer underneath the honeycomb.
6–Nylon insert stop nut.

You have to watch the position of the excenter heads to not create a head crash. That means stay clear of the homing path of your machine!!!

To make it perfect I would use some thin mdf or even better thin airplane plywood on top of the honeycomb and attach some felt to it. The plywood and the felt needs to be cut according to your product + an offset outbound to stay clear of the beam.

The underside of your upper MDF frame would get also a layer of felt.

Depending on how rigid you can make the upper MDF frame you might only need 4 of the fasteners in each corner.


Cut ---- release the 4 excenter bolts ---- pull more material toward the front ---- fasten the excenter ---- repeat.

This should give you the fastest job prep time for an ongoing production without the cost of a professional setup which probably would use an aluminum frame with fance upper structure and just 2 excenter…

Just a thought of what I came up with.

Good luck!

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#Work update 2#

Took out built-in fan yesterday and left only piping and 300W bouncy castle blower sucking on the exhaust end outside. Done wonders to improve evacuation of fumes. Dont even need to close the lid for anything. If not for the PETG film covering part of the back of the machine all smoke would disappear into the table instantly. And this is considering PETG cutting is SMOKY. Unless i waft air in with my hands no fumes/smoke escapes the enclosure.

Topped out at 240 masks an hour yesterday.