Determination of finish-cutting operation number and machining-parameters setting in wire electrical discharge machining

Wire electrical discharge machining (WEDM) plays an important role in precision manufacturing. To obtain a precise workpiece with good surface quality, some extra repetitive finish cuts along the rough cutting contour are necessary. An attempt has been made to unveil the influence of the machining parameter (pulse-on time, pulse-off time, table feed-rate, flushing pressure, distance between wire periphery and workpiece surface, and machining history) on the machining performance of WEDM in finish cutting operations. The gap width, the surface roughness and the white layer depth of the machined workpiece surface are measured and evaluated. Based on the Taguchi quality design method and numerical analysis, it is found that the pulse-on time and the distance between the wire periphery and the workpiece surface are two significant factors affecting the machining performance. Mathematical models relating machining parameters and performance are established by regression, and non-linear programming using the Feasible-direction algorithm was used to obtain the optimal machining parameters. A strategy of optimal multi-cut WEDM process planning from rough to finish cutting operations, including the number of machining operations and their corresponding machining-parameters setting for each operation, has been proposed. Experimental results show that the proposed approach can achieve better performance than that achieved by a well-skilled operator. A better surface quality and accurate dimension value can be obtained in less machining time. (C) 1999 Published by Elsevier Science S.A. All rights reserved.