Good machinable plastics

[Smooth90]

I have a fireball V90 CNC router (w/ bosch colt) and right now I am having a little bit of trouble finding plastics to cut on it.

Just for testing purposes I have been using 3/8in thick LDPE cutting boards that I had lying around. They cut very well on the router at about 35,000 rpm with a 1/8in fishtail end mill. There was no melting, and everything worked very smoothly.

Now I went to Walmart yesterday to get some more cutting boards but they didn't have any LDPE boards in stock all they had was .3in thick "poly" boards. They were very stiff/hard and seemed stronger and were a bit translucent so I figured I would give them a shot. All I know is that they are "poly" boards it didn't say anywhere what type of plastic it was made of. I tried cutting a basic 2d design and immediately noticed that as the bit was plunging in (at 35,000 rpm) the plastic was melting. Once it started making passes the plastic was removed just fine but eventually plastic started to wrap around the bit and I had to pause it a few times to remove the junk off the bit. Afterwords I noticed that the cuts were rougher than that of the LDPE (I did run it at a faster feedrate though) and that the plastic wrapping around the bit damaged the surface (like sandpaper). Whatever this plastic is it seems to be very unfriendly with the router and tough on the bit.

I have looked around at places for good machinable plastics and most people recommend acetal, LDPE, and HDPE. I like LDPE but its a bit too flexible for my uses, I need something that is stiffer (HDPE). I know for a fact that LDPE works just fine with my setup but my question is will HDPE work just as well? Like will it melt during plunge cutting or clump around the bit at a high rpm?


Check out this link

HDPE (HDPE) Sheets & Rods - Order Online

If I were to buy a 12x24 sheet of 3/8in natural HDPE from there would I be able to machine it just like I did with the LDPE (at high rpm's, plunge cutting with no melting).


I'm just trying to get some opinions from people who have been doing this for a while! Don't really want to buy a bunch of plastic I can't cut......


Thanks in advance!

[awerby]

That's probably what Walmart meant by "poly". I don't think that's really the place to find plastic stock for machining, especially if you're in the experimental stage, where it's important to know what you're dealing with.

Try going to a real plastics outlet, like the one in your link, or if they all too far away, order some samples off the net. Get some acetal (Delrin), some polycarbonate (Lexan), some cast acrylic (Plexiglass), a verifiable piece of HDPE, a hard polyurethane, some ABS, and some expanded polyurethane (Renshape). Try them all out, and see which one works best with your machine, and best fulfills the requirements of your project.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

Originally Posted by Smooth90 I have a fireball V90 CNC router (w/ bosch colt) and right now I am having a little bit of trouble finding plastics to cut on it. Just for testing purposes I have been using 3/8in thick LDPE cutting boards that I had lying around. They cut very well on the router at about 35,000 rpm with a 1/8in fishtail end mill. There was no melting, and everything worked very smoothly. Now I went to Walmart yesterday to get some more cutting boards but they didn't have any LDPE boards in stock all they had was .3in thick "poly" boards. They were very stiff/hard and seemed stronger and were a bit translucent so I figured I would give them a shot. All I know is that they are "poly" boards it didn't say anywhere what type of plastic it was made of. I tried cutting a basic 2d design and immediately noticed that as the bit was plunging in (at 35,000 rpm) the plastic was melting. Once it started making passes the plastic was removed just fine but eventually plastic started to wrap around the bit and I had to pause it a few times to remove the junk off the bit. Afterwords I noticed that the cuts were rougher than that of the LDPE (I did run it at a faster feedrate though) and that the plastic wrapping around the bit damaged the surface (like sandpaper). Whatever this plastic is it seems to be very unfriendly with the router and tough on the bit. I have looked around at places for good machinable plastics and most people recommend acetal, LDPE, and HDPE. I like LDPE but its a bit too flexible for my uses, I need something that is stiffer (HDPE). I know for a fact that LDPE works just fine with my setup but my question is will HDPE work just as well? Like will it melt during plunge cutting or clump around the bit at a high rpm? Check out this link HDPE (HDPE) Sheets & Rods - Order Online If I were to buy a 12x24 sheet of 3/8in natural HDPE from there would I be able to machine it just like I did with the LDPE (at high rpm's, plunge cutting with no melting). I'm just trying to get some opinions from people who have been doing this for a while! Don't really want to buy a bunch of plastic I can't cut...... Thanks in advance!