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Date of Award

2-2001

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Supervisor

Dr. M. A. Elbestawi

Abstract

A generic mechanistic approach for simulating multi axis machining of complex sculptured surfaces is presented. A generalized approach is developed for representing an arbitrary cutting edge design, and the local surface topology of a complex sculptured surface. A NURBS curve is used to represent the cutting edge profile. The local surface topology of the part is defined as those surfaces generated by previous tool paths in the vicinity of the current tool position. The local surface topology of the part is represented without using a computationally expensive CAD system. A systematic prediction technique is then developed to determine the instantaneous tool/part interaction during machining. The methodology employed here determines cutting edge in-cut segments by determining the intersection between the NURBS curve representation of the cutting edge and the defined local surface topology. These in-cut segments are then utilized as integration limits for a comprehensive force modeling methodology. A systematic model calibration procedure that incorporates the effects of varying cutting edge geometry, cutting speeds, and feed rates is developed. Experimental results are presented for the calibration procedure. Model verification tests were conducted with these cutting force coefficients. These tests demonstrate that the predicted forces are within 5% of experimentally measured forces. An enhanced approach for dynamic mechanistic modeling for multi-axis machining is developed. The dynamic process simulation methodology is presented as a continuous solution for complex sculptured surface machining. The simulation results demonstrate how the continuous dynamic process simulation methodology is capable of predicting the cutting force and tool deflection for variable tool/workpiece immersions that occur during complex sculptured surface machining operations. The generic simulation approach for multi-axis machining has been demonstrated as a process optimization tool. Feed scheduling was used to demonstrate the process optimization for multi-axis machining. A feed scheduling methodology for multi-axis machining was developed. A case study for process optimization of machining an airfoil-like surface was used for demonstration. Based on the predicted instantaneous chip load and/or a specified force constraint, feed rate scheduling was utilized to increase metal removal rate. The feed rate scheduling implement at ion results in a 30% reduction in machining time for the airfoil-like surface without any sacrifice in the surface quality or part geometry. (Abstract shortened by UMI.)

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