In wire electrical discharge machining (wire EDM), debris tends to stagnate around the wire electrode, since the machined kerf is very narrow. Then, secondary discharges often occur and discharges easily concentrate on the same location, which leads to unstable machining performance, such as frequent wire breakage, low machining rate and low shape accuracy. Thus, better exclusion of debris and bubbles from the gap is very important to obtain stable electrical discharges and high machining accuracy. Conventionally, the debris exclusion from the gap has been carried out by jet flushing of working fluid from upper and lower nozzles. However, in the case of conventional nozzle flushing method, a vortex flow area around middle region behind the wire electrode always generates by inclined flows from the upper and lower nozzles. Therefore, much debris generating in the front surface of wire electrode stagnates in the area. In order to improve the wire EDM characteristics, the vortex flow area should be eliminated or reduced, for improvement of the wire EDM characteristics. This study aims to propose new jet flushing methods for smooth debris exclusion from the gap in wire EDM, leading to high-performance wire EDM characteristics. In this paper, a nozzle jet flushing method with a fine insert following behind the wire electrode is newly proposed, considering smooth debris exclusion by utilizing computational fluid dynamics (CFD) analysis, and the effectiveness of the jet flushing method are experimentally investigated.The analysis results clarify that debris exclusion can be greatly improved by the insert nozzle flushing method, since the working fluid flow around the wire electrode is optimally controlled with a reduced stagnation area, resulting in low debris stagnation. It is also confirmed that the wire EDM characteristics can be improved practically by using the insert nozzle flushing method.
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