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Old 07-26-2010, 05:39 AM   #1
jeffmorris
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Plastic on CNC machine?

I have a computer-controlled router used for wood. Is it possible to machine plastic or similar material on my machine? The router has variable-speed control. I think that I saw a thread on this forum about someone using a CNC machine to create a Corvair van from plastic but I couldn't find that thread. This forum can't find threads using "van" as search word.
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Old 07-26-2010, 03:41 PM   #2
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Re: Plastic on CNC machine?

As long as the rpm is low (and the tool head moves nice and slow) it shouldn't be a problem. I'd use chunks of 2 pack polyurethane resin moulded vaguely to the shape you want first. I'm guessing that the usual kit polystyrene may get too hot and clog (has a lower glass transition temp).

Polyurethane cuts beautifully with milling tools designed for metal (and they don't go blunt too quick either)!

Have a look at my RS60 thread - there are shots of me milling some polyurethane brake drums using a 1mm milling flute - around 300 rpm. I cast round resin shapes inside shaving can caps etc. ready to fit in the mill/lathe chuck.

Good luck and let us know how you get on!
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Old 07-27-2010, 05:43 AM   #3
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Re: Plastic on CNC machine?

Is there a material that is similar to wood so that woodworking tools can be used but has smooth surface like plastic? I wish to make model cars. Where do I buy polyurethane sheets?
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Old 07-27-2010, 10:46 AM   #4
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Re: Plastic on CNC machine?

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Originally Posted by jeffmorris View Post
Is there a material that is similar to wood so that woodworking tools can be used but has smooth surface like plastic? I wish to make model cars. Where do I buy polyurethane sheets?
You might be better of with a product like Renshape:

http://www.sovereign-publications.com/renshape.htm

Don't know how it behaves with powered wood tools, but can be shaped like wood using hand tools. Problem is; it is only available in big (expensive) chunks and is not easy to find in the USA.

I think some American modellers were getting small supplies as off-cuts from their local art & design colleges...may be worth a try?

A silly question, but why not make the master buck in something like pearwood and then take a rubber mould off it to cast the plastic?
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Old 07-28-2010, 01:42 PM   #5
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Re: Plastic on CNC machine?

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Originally Posted by cinqster View Post
As long as the rpm is low (and the tool head moves nice and slow) it shouldn't be a problem.
Quite the contrary in my experience. I usually machine plastics (delrin, HPDE, acyrlic, ABS, polyurethane) at high RPM (3000+) on full rapid. Any slower and I get crappy surface finish due to melting.
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Old 07-28-2010, 06:51 PM   #6
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Re: Plastic on CNC machine?

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Originally Posted by GTmike400 View Post
Quite the contrary in my experience. I usually machine plastics (delrin, HPDE, acyrlic, ABS, polyurethane) at high RPM (3000+) on full rapid. Any slower and I get crappy surface finish due to melting.
Yikes...that's a weird one Mike!

I can only guess that the melting is occurring because the cutting tool is getting hot? Try a very slow speed if you haven't done so already, you may find a cooler tool cuts better. I've found the same thing with cutting plastic sheet with a hand saw. Slow is good...get too fast and the blade sticks.
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Old 08-15-2010, 01:15 AM   #7
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Re: Plastic on CNC machine?

cutting plastic should be no problem with a cnc router. Mike is correct on a vertical or horizontal cnc machine they use coolant so you do run above 3000rpm. You want a very sharp cutting tool... dull tool will make a bad part.
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Old 10-27-2010, 05:39 PM   #8
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Re: Plastic on CNC machine?

I master parts by cutting corian with a carbide mill at 30,000 rpm. The stuff machines very well, also sands and takes primer easily. Ettore
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