This proposal is to conduct research on high speed high power milling (HSHP Milling) in the following three interrelated parts: Sensing of Milling Cutter Breakage, Dynamics of HSHP Milling, and Design of HSHP Spindles. This proposal is based on recommendations resulting from a prior NSF grant. In the part on Sensing of Milling Cutter Breakage the algorithm developed and tested in the prior grant will be used which is based on sampling of the cutting force, synchronized with the cutter teeth and generating first differences of averages per tooth. Breakage is clearly recognized by this method and the breakage is distinguished from changes due to milling transients like entry into a cut. In the current proposal an accelerometer signal will be used to reconstruct the force through simulation and reverse transfer across the spindle dynamics. This indirect force measurement approach is necessary because the cutter tooth frequency in high speed milling is beyond the dynamic response capability of direct force measuring dynamometers. In the part on Dynamics of HSHP Milling the procedures developed in the prior grant and aimed at determining the most dynamically stable spindle speed will be automated in the current proposal by means of sensors and calibration cuts so that the optimum speed for various operations and tools will be automatically adjusted. In the part on Design of HSHP Spindles research on damping in pairs of angular contact bearings will be conducted in order to include this important aspect in the optimization of spindle dynamics. The proposed research is necessary for the development of HSHP milling into a practical process. Solutions to the three problems being addressed are not available, these being cutter breakage detection, automatic adjustment to the most stable speed, and design of dynamically rigid high speed high power spindles. HSHP milling has application to milling of industrial components where large amounts of metal has to be removed, for example pocketing operations on aircraft structural panels, face milling of steel parts in Army arsenals, and milling of cast iron stamping dies for automotive parts.
