Prediction Algorithm for WEDM Arced Path Errors Based on Spark Variable Gap and Nonuniform Spark Distribution Models

Abstract

Wire electrical discharge machining (WEDM) is a demanding high-precision process for machining of hard-to-machine materials. The main issue is manufacturing errors in shape and radius of small arcs generation. In this paper, a novel model about spark variable gap sizes and nonuniform spark distribution around the wire on arced path machining is first theoretically developed using spark angle domain and WEDM dynamic analysis. Applying spark-force distributed around the wire and resulting wire deflection are estimated by the WEDM conditions influenced by plasma channel specifications, discharge frequency, wire guide clearance, wire tension, and arc radius. Total theoretical arced machining errors including wire deflection and spark gap size variation around the wire interface are calculated based on the proposed model. In addition, machining errors of straight and small arced paths are experimentally analyzed under variation of WEDM influential parameters including discharge frequency, arced path radius (150, 300 and 450 μm), and wire tension through the statistical full factorial. Comparison of the results for different sets of variable parameters shows that the theoretical values of the arced machining errors can be consistent with the experimental one by a coefficient which depends on the machining conditions and the WED machine type. Finally, based on the theoretical and experimental results, a theoretical algorithm and an operational method with mean accuracy of 84.8% are proposed for predicting and compensating the errors of WEDM on the arced paths. Findings of this research can be used in high-accurate WEDM applications and industries.