Machining plastic with a CNC router

does anyone made experiences with cutting various plastics with a CNC router yet ? I’m in particular interested how the finish will look like; I’d also accept some manual grinding with sanding paper….

why I’m asking: I realized that there quite some people (incl. myself ) who want to build or buy all machines and also those relative expensive molds. I thought it could be much cheaper and easier for them to cut standard plastics (blocks, cylinders,…) – provided by the precious plastic community – on low-cost CNC routers (500-1000 euro). This is also the way with the other materials like steel & aluminum. In one or 2 years there are probably at least 1-10 shredder stations in most countries 🙂

I am not sure, but I think it would be even possible to make the CNC router from hard plastic, it should be rigid enough to cut plastic with it, no ? At worst you could enforce critical connections on the router with aluminum parts.

Anyways, the cutting possibilities of a CNC router are limited of course but still way cheaper and more flexible than molds & extrusions and even horrible slow 3D printing, though.


A few years ago I saw people at a local FabLab using a large CNC flat-bed router to cut sheets of Ecosheet** (or a similar brand).

It seemed to be relatively easy to cut, and no more difficult than cutting plywood or MDF.  However, they did find that the material could be rather brittle, when subjected to bending loads.


One observation that I would make is that industrial/commercial materials such as Ecosheet are of a consistent thickness, and are probably rolled in large sheets.  Trying to make large consistent sheets might be more difficult in a small Precious Plastic workspace, if all you can do is squeeze shredded plastic granules between heated platens.  But on a smaller scale, I’m sure milling would work.

I am just telling you what i have experienced working in a professional machine shop that make parts for companies all over the united states and some parts for the U.S. government. What happens when you machine plastic.

I talked to him today and he hate working with plastic. it is the material he likes machining the least.

I think it can be done, because plastic material is soft enough to process on CNC Router. our team has already done it

My professional opinion. CNCing plastic is extremely difficult. I currently work part time with my mentor at a machine shop that has been cnc machining for 34 years. The worst material he has ever worked with is plastic. We mainly work with delrin and abs.
When you machine plastic you cut away all the strength of the material. This is known as stress relieving. When you do this the plastic relaxes and flexes twords where the material is is now missing. When plastic is extruded it that whole mass is necessary to keep it straight when you weaking one side of the plastic the now stronger side pushes the material to the week side. Thus it is very hard to get good parts that are straight at the end.

Monday of this week we made 40 parts out of delrin 1 set of parts is a 15 count of around 2 feel long by 4 inch x 4 inch parts (pretty big). When it was all machined the bow (flex) in the middle was crazy. when you push 1 side down to the surface plate lets say the right side the left side is now bowed upwards 1/3″ from the table.

the other parts were about 30 count small peices made out of delrin that were 1.5″ x .25″ x 3″. They aswell had a massive bow in the center. I would bend the bow out of it. It would eventually bend itself back we ended up sending both the parts to the customer saying that next time they should probably use metal because for the most part metal is way more stable.

Also another side my mentor said that delrin is also not recycled from machine shops but metal shavings are.

I did not know this phenomenon before working at this machine shop.

100% possible, just look for “Plastic CNC Milling” on youtube


ok i see, then maybe try contacting
If i’m correct, they have an upgraded extruder and can do some beams !

Hi Imuh,
this topic is more about machining stock plastic, ready to use flat bars, or cylinders, etc… It’s interesting because then the workload of recycling plastic can be distributed more easily. Myself for instance has no space for the shredder, and extruder so I am looking for options to just buy the extruded plastic from my clients and take it to next stage: machining it to final products.
kind regards,

Hey there

There is a filter option on the bazar, you can select plastics only, it will bring you up here
hope it helps

yeah, had no chance to get recycled plastic yet, on the bazar there is mostly decoration and stuff like but no stock plastic at all, not even on request. next week our shredders are ready…

by custom mills i mean, grinded HSS roll bars as most folks do for their lathe works, it seems the softer the plastic, the less flutes you need, like with aluminium.

acrylic seems the best so far, nice finish but i have no idea this can be recycled or self-made.

Oh. I only now realize you were asking about milling plastics in general – not recycled plastic from the machine. In that case I can tell you: you can basically mill as good as any plastic with the right bit and settings.
I’ve milled acryllic, polycarbonate, polypropylene, corian, expanded pvc, expanded ps, and expanded PUR.
What do you mean with requiring a custom made drill bit?

so made the first tests (dhpi and acryl): absolute fantastic material to work with! it may require still custom made drill bits (one flute) and more optimization about speeds and feeds. i am back to you if the research is complete (videos/pictures).

I have a pretty strong CNC but i think the material could be done with 3d printer made of plastics as well, will tell you soon.

for now: it’s a go !

ps: I started collecting suitable products here. (products being ‘CNC’ friendly). Unfortunately there is no stock plastic to get in the bazar, if someone knows other sources, I’d be happy to test them to.

You rock!! Let’s see who makes first, haha just kidding. Probably you, in my university there is a lot of bureaucracy. Good luck pal

keep me in touch

i am something like 2 weeks away from doing proper tests, on various types of plastic.

Hi guys, greetings from Argentina.I had the same idea about using a cnc router over a plastic brick or something, in efforts to avoid molds (too expensive). Anyway, If you guys did some tests or uploaded some videos to youtube or something, please share it 🙂

Next week, if things go right, I’ll do some tests at my University’s Fablab with PP (5) bricks.

Awesome, looking forward to those tests! I think, since the amount of material I had was limited, I didn’t want to waste it on “just tests”. I think I wanted to make something useful out of it but in the process of coming up with something it slipped of my head.

Anyway, enough of me thinking out loud here.
I’m out of office until Tuesday, so I won’t have access to our cnc-machine. When I’m back I’ll try to schedule for some more tests. I subscribed here to get some occasional reminders. 😉

alright, let’s go for more tests. as soon i’ve got approved for the bazar, to place requests for plastic stock materials (bricks, cylinders) I will do some intense testing. I have quite some products in the pipe which are perfect match for plastic.

and yes: sending the chips back to the source would be awesome 🙂

Yes, I did 1 test which is seen in this topic. I said back then I would do more tests but I never got to it, and am wondering now how come. Would be nice if I could do some more tests soon.

But I agree with the topic starter. It’s definitely a good way to shape things without the use of molds. I think there’s a lot of potential for using this in some kind of system where I would be able to buy the material, mill it and return the chips/leftover material for recycling again.