When it comes to high feed milling cutters, trochoidal milling and radial chipping thinning you have to be careful of "calculated" metal removal rates. They use very high feed rates (IPM) to achieve high metal removal rates despite their low axial or radial depths of cut. In the case of circular trochoidal tool paths, half of the time the tool is cutting air as it makes its return arc to the workpiece. As for high feed face mills and peel milling using chip thinning, the high programmed feed rates are not constant. For each change in direction, the tool must decelerate to a zero feed rate, reverse and accelerate back up to the programmed feed rate. If the feature is small, it may never get up to the programmed feed rate. The formula for MRR is Depth x Width x Feed Rate (IPM). If the IPM is not constant the MRR may be a lot lower than you think.
