A Study Of The Debris Exclusion For Various Cross-Section Electrodes In Linear Motor Equipped Deep Cavity Edm Process

A linear motor equipped EDM machine provides a high speed jump motion for improving debris removal. The debris exclusion characteristics of different width electrodes in deep cavity EDM were studied by fluid dynamics analysis and by no discharge but similar debris exclusion conditions experiments. A setup is designed, and images of the dielectric and debris particles during the electrode jump are captured by a high speed camera. The results of a square cross section electrode show that large bubbles would generate beneath the electrode leading to poor debris removal under a high jump speed or jump height, or a large machining depth condition. Mixing of the debris particles and the dielectric by an auxiliary small jump prior to a large jump facilitates debris exclusion. However, the effect becomes ineffective once over 50% of the space beneath the electrode is occupied by the bubbles. Double-jumps with debris exclusion for both jumps results in very satisfactory debris exclusion with almost no debris particles left in the cavity under the appropriate jump height and speed conditions. Large bubbles are less likely to generate for the rectangular cross section electrodes. But the debris exclusion is less effective since it is more difficult to flush and bring up the debris particles accumulated at the bottom of the cavity due to a too low dielectric speed in the gap. Hence higher jump heights and speeds are required in double-jumps in this case. For a very thin-wall electrode, the debris exclusion is limited by the maximum speed of the linear motor. The ratio of the machining depth to the width of the cavity achievable for effective debris exclusion is around 9, and four consecutive jumps are needed. (C) 2018 The Authors. Published by Elsevier B.V.