THE EFFECTS OF MACHINING SETTINGS ON THE BEHAVIOR OF PULSE TRAINS IN THE WEDM PROCESS

A pulse discrimination system has been developed to study the characte ristics of pulse trains in the WEDM process under various machining co nditions. The effects of on-time, off-time and feed on the variations of the proportions of short sparks, are sparks, and normal sparks in t he total sparks (defined as short ratio, are ratio, and normal ratio, respectively); the distribution of the ignition delay time of the norm al sparks the average ignition delay time; and the proportion of machi ning time in a specific sampling period were investigated. An approxim ate method for estimating the variation of the average gap width is al so introduced. It is found that a short on-time, or a long off-time, o r a large feed, results in the decrease of both normal ratio and avera ge ignition delay time, and an increase of short ratio. On-time has th e largest effect on the are ratio, whilst off-time has the least effec t. The ignition delay time of the normal sparks displays a reverse J-s hape distribution. On-time is the most prominent factor amongst all of the machining settings under consideration affecting this distributio n. In addition, the distribution becomes more left skew with a higher peak and a shorter tail under the condition of a shorter on-time setti ng. Based on the analysis results, the instability during the WEDM pro cess can be attributed to an apparent increase of either are sparks, s hort sparks, or both. A strategy to improve machining stability with r espect to each case is proposed accordingly. (C) 1997 Elsevier Science S.A.