How to get a smooth surface finish of Engineering Plastic Materials

Hi,

I am working for a manufacturing industry that specializes in medical products for Orthopaedic surgery. I've been recently working out on a project to machine the component that comes in MS-000002 F648 VHMWPE – a sort of engineering plastic material. I am using a CNC Lathe to machine the component but unfortunately, I couldn't get the surface finish I need at the internal hole. I want to get a surface finish of below Ra 40μin after machining but it turns out the actual data measures 50 - 60μin which is not acceptable. I tried to regrind the insert and put synthetic coolant to take away the heat but the surface finish doesn't seem to improve. Also, no matter what I can do to the parameters on the CNC program, the actual surface finish remains not lowering at all. Any suggestions on how to bring back the surface finish (Ra) to below 40μin? Any helpful information that you can provide me with will be much appreciated.

Thanks,

Richard Orthopaedic