One thing to look at would be the triangle/polygon count of your stl. It could be a low count and this would give you a surface that has many large facets. On top of that, if you scale it up, it could get worse. From your description, I'd say it would be better and faster to do it as a 2d cut or just a 3d cut around the bumps (whatever they are) and 2d for the rest. For the holes, a 1.5º 0.125" tapered ballnose would do the trick and by using a spiral ramp, it would be fast. For this toolpath, I'd set your rapid for the Z axis as fast as possible (standard or alpha will dictate how fast) and remove the dust foot. This way, when the toolpath for each hole is finished, it will rise up fast and without the dust foot, the waste piece won't 'jam' the tool. Doing it this way saves a lot of time by not having to pocket out the hole. For SB's, we generally use inches per second, so 3 ipm would be .05 ips, and that would be sloooow. Perhaps you meant ips.

Using a 0.25" downcut endmill will never give good results for finish toolpaths, as it needs a ballnose to follow the contour properly.


As Kyle demonstrated, just use the spiral down toolpath and let the waste piece stay or pop out and clean up later. Saves a lot of pocket time.