Polypropylene

[chuckster]

Has anyone ever cut 1/2" thick polypropylene? I have an opportunity to pick up a job cutting parts out of this material. Thanks!

[Brady Watson]

You shouldn't have too much diffficulting cutting polypro on your tool. If you want a good finish, use the largest diameter tool you can (EG 3/8 or 1/2 in leiu of 1/4"), do multiple Z passses with allowance, then come back and cut to exact size in a single pass, full depth to get a nice finish. You'll want to use a single or double O-flute cutter to get proper chip extraction and to avoid chips melting to the finished parts.

-B

[chuckster]

Thank you very much for your input, Brady. I'll pick up the bit today! I have cut both acrylic and polycarbonate with lots of practice. We mostly cut wood, and since plastic has gotten so much more expensive these past few years, I kind of hesitate to try the cuts.
Thanks again, and I'll post the results.

[chuckster]

While I am still on this subject, why use a 1/2" bit and not a 1/4" bit? I haven't picked up the 1/2" bit yet....just wondering!

[Brady Watson]

Chuck,
If the design isn't too intricate, then a larger diameter bit is favored over a smaller diameter bit to reduce deflection, and in turn, increase cut quality on the part. If the part to be cut out needs to be cut with a 1/4 to capture all of the detail, or get into a tight spot, then that's what you'll have to use. A 3/8" bit is a good compromise since you only give up an extra 1/8" of kerf. Smaller diameter tools in thicker materials often result in 'chatter' marks around the perimeter of the part. You'll want to experiment with stepdowns and move speed to get it in the right range for the bit you are using.

-B

[2talltary]

If you need small pieces for practice and not cost a lot try http://hightechplastics.com/ They have lots of plastic bits and chunks for cheap.

[geometree]

I may be mistaken but I believe the plain white semi-translucent plastic cutting boards you can get just about anywhere are polypropylene. They are cheap and cut great with an O-flute tool. Good for shop fixtures or just to practice on.