Laser Cutting Impact Modified Acrylic

I am looking for feedback from anyone that has experience with laser cutting impact modified acrylics (polymethyl methacrylate, PMMA).

Our team has a 130W Thunder Nova 51 laser cutter and a Velox VR-5050 CNC router. We use the laser cutter to make lots of prototype parts, mock-ups, etc. out of acrylic for testing because it is very fast to go from idea to CAD to physical part literally in minutes. When we settle on a design we then cut the part out of aluminum or polycarbonate as appropriate on the CNC router. This work flow has been very effective for our team.

However, I would love to find a more durable plastic that can be cut as nicely as acrylic on the laser cutter with material properties closer to polycarbonate that could actually be used as a “polycarbonate substitute” where appropriate on the actual FRC competition robot. Acrylic has very limited use cases on FRC robots in my experience.

I have researched some on impact modified acrylics such as “Acrylite Resist” and “Duraplex”. There are other brands. They all seem to be much more durable than standard acrylic.

Each of these brands of impact modified acrylics come in different grades like 45, 65, 70, 75, 100. The “100” grades seem to be comparable to polycarbonate in terms of impact and resistance to breaking.

https://www.acrylite.co/3059b-acrylite-resist-physical-properties.html

The “Resist 65” grades seem to be fairly commonly used in store displays and such. Here is the MatWeb for “Acrylite Resist 65”:

http://www.matweb.com/search/datasheettext.aspx?matguid=4ab46e240b6644ea81fc3687f011ba6e

It also seems to be easily laser cut like regular acrylic sheets, however, when it is laser cut it tends to leave a sticky/tacky edge. Supposedly this sticky/tacky edge can be removed by wiping the edges with VM&P Naptha to clean them up:

https://www.acrylite.co/3060b-resist-fabrication-manual.html

Does anyone have any experience laser cutting impact modified acrylics and using the resulting parts on actual competition FRC robots? How durable is this material compared to polycarbonates or maybe acetals? Is it a viable laser cuttable “polycarbonate alternative” for FRC use in appropriate applications? If you have experience with using impact modified acrylics on FRC bots what grade(s) and brands have you used? 65?, 75?, 100? Acrylite Resist? Duraplex? Some other brand? If you have experience laser cutting impact modified acrylics, how sticky/tacky do the edges come out of the laser cutter? What secondary processes have you found work well to remove the stickiness? Naptha? Lightly sanding?

With laser cutters becoming more and more common in FRC shops I’m wondering if impact resistant acrylics may become a more useful material to teams. I just have no experience working with impact modified materials but am willing to get some and run some tests but would value any insights others with experience would be willing to share.

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1923 has shifted our workflows to laser cut parts wherever we can. However we find that laser cut Delrin is best for us. We tried a few parts in impact resistant acrylic in the early goings and found that it was too much of a risk to put on a competition robot. Great for prototypes though.

We have access to a few 400 watt CO2 Lasers through my work with VERY powerful fume extraction. For that reason we actually even use the occasional laser cut polycarbonate part.

A 130W laser should be more than powerful enough to cut 1/8" or even 1/4" delrin if you cut slowly enough. I highly suggest going this route. I’ll see if I can dig up some pictures, but we actually used Delrin for our entire shooter hood and turret assembly as well as our climber gearboxes.

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I’ve cut airplane windows on a 100W laser. It went slow, but mostly okay. Not sure what kind of acrylic they were. They were about 0.2 inches thick.

We’ve extensively used laser cut 1/4" Delrin as a substitute for 1/8" thick aluminum gussets and gearbox plates, without too many issues

Our team used a lower power laser to cut thin petg shields for ppe production. I heard it worked well, but I don’t know how well that would scale up with more powerful lasers and thicker sheets. I’m also not sure how petg stacks up against delrin mentioned by others.

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We cut 0.25” PETG on a 100W laser. Bottom edges of parts were sometimes rough and slightly melted back onto the workpiece, but dimensions held up well (for prototyping and non-integral mechanisms). Doesn’t smell or look good either. We ran the same settings we used for 0.25” acrylic so I’m sure finish and performance could be improved. I can’t make any comparisons to Delrin either, but it is significantly cheaper than it and polycarbonate and replaced most of our acrylic prototyping last season (shoutout to the 95 build thread for inspiring us).

As a practical example, we prototyped beyond-bumper intake arms with 0.25” PETG which took quite a beating before moving to a polycarbonate iteration.

Where do you buy that 1/4" Delrin?

This past season we used our Inventables voucher for delrin. Good way to get different material for cheep. https://www.inventables.com/categories/materials/plastic

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Out of curiosity, why don’t you just laser cut your parts from lexan? We started making robot parts from delrin, but stopped that when they would fail our toughness testing. (Throw the part on a concrete floor as hard as you can.) We switched to lexan for most of our parts and haven’t looked back. This year our bot was almost entirely lexan.

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Polycarbonate absorbs the radiation from the laser and thus tends to melt and get goopy rather than cut cleanly.

Our edges end up a little charred. Clean them up with a deburring tool, and some light hand finishing and you’re good to go. Small price to pay for the toughness of lexan parts in your bot.

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I’m glad that’s been your experience. I’ve never personally laser cut PC but have always heard it’s a no-no.

Also ventilation can be very important – check out the guidance from your laser vendor before cutting any new material. https://cpl.org/wp-content/uploads/NEVER-CUT-THESE-MATERIALS.pdf.

We had heard that too, but were unable to find anything in writing that pointed to a safety hazard from toxic chemicals. We did find plenty of commercial laser cutting companies who cut polycarb, though. We use plenty of ventilation because it smells awful.

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+1 for PETG. Cheaper, faster, same cleanliness. Use tons at work for prototyping.

https://www.makeitfrom.com/compare/Glycol-Modified-Polyethylene-Terephthalate-PETG-PET-G/Unfilled-POM-C

End result is as clean and mechanically similar to Delrin, but cuts about 4 times faster in my experience, and is about 3 times cheaper. PETG is also extremely formable with heat which lets you pull some neat tricks, even if all you have is a hair dryer.

(Haze is from dry flim lubrica- er, non-stick clear coating https://www.amazon.com/DuPont-Teflon-Snow-Ice-Repellant/dp/B07Q7DD2YC)

Acrylic, for me, is relegated only to anything that needs that extra stiffness, cleanliness, or scratch resistance.

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We’ve never had any issues with delrin parts (1/4" thick). Also, the majority of laser cutters can’t actually cut lexan for some reason (I believe it messes with the optics), so lexan isn’t really an option for most

The trouble with Delrin is that it burns with a nearly invisible flame and is non self-extinguishing. Many materials stop flaring up when the laser beam is removed. Not the case with Delrin, it keeps going and growing. If your laser focus if off, power too high, or travel speed too slow, you’ll soon find yourself with a sheet of Delrin that is morphing into a giant hole dripping hot liquid Delrin inside your machine. You really have to keep an eye on your settings and cut progress, and maintain a good air blast to prevent a flame from developing. If you do it right though, it can cut fairly clean.

All Combustion [1] products Are Bad – polycarb does not appear to be special in that regard. Keep your exposure low.

[1] and vaporization and other mechanisms

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Combustion of 2H₂ + O₂ —> H₂O which I don’t generally consider an inherently Bad chemical…

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I thought laser cutting PC was a bad idea due to the fumes ability to cloud up the lens on the laser? Not the end of the world but definitely increases the maintenance load.