Tool Path Setup

[mgp1243]

The company I work for makes ultra high molecular weight polyethylene parts for orthopaedic devices, but unfortunately we are have to machine all our parts right now, even though our competitors are making comparable parts via compression molding. The problem is that we end up with an inferior finish on our part with visible marks from the cutter path. We are using a 1/4" ball cutter with a 0.01" step-over, but we are getting marks on the part that seem to coincide with lines from IGES mesh. We have a sample of a part similar to our own that was cut using a fly cutter, which has a very smooth finish, almost comparable to a compression molded part. The architecture on our part, though, rules out the use of a fly cutter. Are the marks we are getting actually result of the toolpath programing / part modeling, or is it more likely that it is a tooling problem?

[wjbzone]

I think you are going to get visible tool marks using a 3d machining operation with a ball end mill. Your ratio of ball/stepover looks ok.

In steel, I would go with that and add a polish operation to easily get 125 finish. Can you polish that material? What finish requirement do you have?
Bill

[gibbsman]

Do you have room to use a bigger endmill? If you have a larger radius on the ballnose the stepover amount will be less drastic.

[Ken_Shea]

I cant quite visualize the inferior finish you mention, but if it is scallops then that is likely due to excessive step over, or use, as gibbsman suggested a bigger ball mill.

I cant say experientially but from everything I read cutter geometry and cutter quality for a specific material can make all the difference in the world. Have you talked to tool cutter salesman about a specific tool for your material.?