THE PREDICTION OF CUTTING FORCES AND SURFACE ACCURACY FOR THE END MILLING PROCESS

The end milling or peripheral milling process is a metal cutting process that uses a multi-tooth cutting tool. This process finds application in many industries and is widely used in the aerospace industry for rough and finish machining of aircraft structural components. In these applications, many machining operations are perfomed on thin workpiece sections with long, flexible cutters. The cutting forces cause cutter and workpiece deflection which produce inaccuracies in the finished surface dimension.; Mathematical models are developed for cutter runout, cutting forces, cutter deflection, workpiece deflection, and the surface generation mechanism for end milling. Cutting forces are computed with the assumption that cutting forces are proportional to the chip area on the cutter. It is shown that cutter runout will drastically increase the maximum forces on the cutter and shift the frequency content of the force signal away from the tooth passing frequency to the spindle rotation frequency. Cutter and workpiece deflection are computed assuming static force loading of a point cutting force. The cutter is modeled as a cantilever beam, and the workpiece is modeled as a variable thickness plate clamped on three sides and free on the fourth. Workpiece deflection has been computed by both the finite element and finite difference approaches. It is shown that variations in the magnitude and location of the cutting force as the cutter rotates produce curvatures on the finished surface. The proposed models are verified through a comparison of measured and predicted force and surface error data for 7075 aluminum.; The cutter runout and surface generation models provide new insights into the mechanics of the end milling process. The models also serve as useful tools to improve productivity in process planning applications where it is desired to select machining conditions that are economically attractive yet satisfy constraints on cutting force, surface accuracy, or machining time.