Best plastic material for machining on CNC routers?

[jeffmorris]

I am looking for best plastic material for machining on CNC routers. I wish to make parts for model cars. I have 3D printer but a job like an engine block for 1/4th scale model cars can take 24 or more hours. Any suggestions? I know that there are different kinds of plastic materials. I want a plastic material that can be machined as if it is plywood.

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[Paul-JB]

Hdpe cuts like butter and is fairly inexpensive. It is tough to glue though if the parts need that for assembly.

[peteeng]

Hi Jeff - Acetal (POM) is very good for detailed work. Takes threads well and has a nice hard sharp feel. I've used it a lot for aluminium replacement in mining instruments...Peter

[joeavaerage]

Hi,
the biggest problem with machining plastics is they heat up and then gum up the tool. They all do it to a certain extent but some are easier than others.

Hard acrylics and polycarbonates machine reasonably well especially if you can use an air blast to remove chips from the cutzone, recutting chips is
a sure recipe for disaster.

I go with Peteng, I like acetal. Its hard enough to form chips rather than long strings and yet has just enough flex to be a tough material, especially for small parts.
I now regularly use flood cooling on acetal, in fact ALL plastics, it flushes the chips out of the cutzone and vastly reduces the propensity for loading up the tool.

The hardest to machine (without tool build up) is polyethylene (with plasticizers) or teflon (PTFE). I reduce the surface speeds somewhat but maintain a fairly
aggressive chip load with as open a toolpath and as much blast and/or coolant as I can muster.

Craig

[CitizenOfDreams]

Polycarbonate and acetal are my favorite plastics to machine. ABS also cuts very easy, but I have only tried thin sheets - does it come in thick blocks too?

[jeffmorris]

Will the board shown at https://smile.amazon.com/gp/product/...010_em_1p_5_lm work?

[joeavaerage]

Hi,
yes it will work....its really a question of how well. Why don't you buy a piece and try it out.

Then go to a engineering plastic supplier and get some offcuts of acetal, acrylic and maybe some HDPE. A box of beer will get enough offcuts to
fill a wheelbarrow!

I suspect that you'll find its less about the type of plastic but more about the tools, feeds and speeds and MOST importantly air blast/flood coolant.
If you can keep plastic cool and stop it from gumming up your tools then machining plastic is a breeze.

Craig.

[routalot]

I agree that acetal and hdpe cut very nicely,just be aware that if you machine a lot off them,they may curl up a bit.I have machined a long taper on acetal on a vacuum hold down and when the vacuum was turned off exactly that happened.Fortunately the piece was a through bolted spacer and the clamping pressure returned it to the intended shape.