CPVC Pocket Surface Finish

[mpuvdd]

Hey everyone,

Young machinist here, having some trouble with surface finish on a CPVC part.

I'm only cutting 0.1" deep into the part with a 0.05" finish pass. O-flute 1/4" spiral single flute at 18,000 rpm x 200 ipm.

Notice the dwell marks that show up at points where the cutter changes direction. These marks are over .01 deep. I have tried creating a toolpath that starts outside of the part and only makes radiused turns but have not figured out a way to completely avoid tight corners.

50hp vacuum pump pulling plenty of vacuum. Newer Onsrud machine. Spoil board is getting a bit thin but I don't think that's the issue as I pocket UHMW parts just fine. Perhaps a different cutter would be recommended (I'll talk to my tooling guy on Monday).

Any recommendations for you all is more than welcome!

 

[plastikdreams]

Cpvc likes to get gooey when cut. What are you using for coolant? The cpvc will stick to the cutter briefly then knock off when the machine moves again. I'd get something with more flutes at the least. Look at the chips in the pic, you can tell they were soft.

 

[Scruffy887]

You are melting it. Lower RPM to 1000 and see what happens. I have not done CPVC in a long time, but I remember that it is not a lubricating plastic like HDPE or UHMW. Sounds like you are using a router so flood lube not possible.
With correct speeds/feeds the cut will be perfect with no burr on top.