I'm using a 3 flute 1/2" ball mill to do some surfacing in a mold. First I do a rough surface finish 0.007" from the drive then a surface finish contour at 0.007" from drive to prep the cavity for finishing. I then use a surface finish project with a 0.015" step over to clean up the more horizontal surfaces and a surface finish contour with a .02" step down to get more resolution on the vertical surfaces. Both finish steps are set to leave 0.000 material on the drive surface. Every time I do this with the ball mill, no matter which of the two operation I run first, the surface finish contour digs 0.002"-0.003" deeper than the project. I've attached an image of an example.

Is there something I can do to prevent this? Leaving 0.002" on the drive for the surface finish contour might do it but it seems like a poor solution. Are there other operations that I should be using all together for this kind of surfacing? I'm using X8.

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