Cutting polypropelene ! inch thick

[dubliner]

Havent ever cut this material. Apx 24 square blank with a 14" square out of the center. Bit, feed & speed anyone? thanks Neville

[paul_z]

I've cut 1/2" polypropylene and it cut beautifully. I did get some acumulation of "thread" on the top of the bit but it didn't seem to matter. I used a tapered ball bit at 22,000.

Since things can vary so much bit to bit and machine to machine, I'd suggest cutting a 5 inch square in the middle first. Twiddle with the bits/parameters and cut a 5.5 inch square. twiddle cut 6.0 ... when it looks good, go for the final cut.

If it has to accurate, make the final cut in two passes using about 0.010 allowance on the first pass and zero allowance on the second pass.

You may get a bit of "flash" on the top if you use an upspiral bit. I was able to remove the "flash" by chasing the edge with a piece of hardwood. It came off easily and quickly.

Paul Z

[lcolburn]

I cut 6 sheets of this stuff late last year, and it cut beautifully. I used one of Onsrud's single flute 'soft plastic' bits (expensive, but great), 3/8" diameter. As I remember, my settings were as follows:

16500 rpm
climb cutting
200ipm plunge and feed (using spiral ramping), .25" depth of cut.

I did this in two passes- one with a .020" allowance, and a second pass at full cut depth right on the part. My only complaint was a small dwell mark at the point where the machine pulled up from the final pass.