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 preci sion manufacturing. To obtain a precise workpiece with good surface quality , some extra repetitive finish cuts along the rough cutting contour are nec essary. An attempt has been made to unveil the influence of the machining p arameter (pulse-on time, pulse-off time, table feed-rate, flushing pressure , distance between wire periphery and workpiece surface, and machining hist ory) 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 a nd the distance between the wire periphery and the workpiece surface are tw o significant factors affecting the machining performance. Mathematical mod els relating machining parameters and performance are established by regres sion, and non-linear programming using the Feasible-direction algorithm was used to obtain the optimal machining parameters. A strategy of optimal mul ti-cut WEDM process planning from rough to finish cutting operations, inclu ding the number of machining operations and their corresponding machining-p arameters setting for each operation, has been proposed. Experimental resul ts 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.