In wire EDM, better exclusion of debris generated in the working gap is very important in order to achieve stable machining performance. When a lot of debris stagnates in the gap, the discharges easily concentrate on the same location, which causes unstable machining performances including frequent wire breakage, low machining rate and low shape accuracy. The debris exclusion from the gap has been conventionally done by jet flushing with upper and lower nozzles. However, the effects of jet flushing on the debris exclusion in the wire EDMed kerf and wire behavior have not yet been clarified sufficiently.
In this study, the flow fields and the distributions of pressure applied on the wire surface due to jet flushing were analyzed by computational fluid dynamics (CFD) analysis, and the deflection of wire was calculated by a structural analysis using the distributions of the forces obtained by the CFD analysis. Furthermore, the effects of machined kerf length on the wire deflection and wire breakage were discussed. As a result, when the machined kerf length is as short as a few mm, the fluid flow in the kerf is significantly disturbed by nozzle jet flushing, which causes unstable large wire vibration. Then, wire breakage frequently occurs. Therefore, it is essential to select the optimum jet flushing conditions in order to prevent wire breakage when the machined kerf length is short. |
