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*STUDY ON FLUSHING FOR EDM (2nd Report), Analysis and Simulation of the Effect of Jet Flushing for EDM
In the previous report, we developed a dynamic jet flushing method which is called "scan flushing". Experimental results clarified the effectiveness of this method on the precision of machining over conventional jet flushing method. Although good resluts of the scan-flushing were obtained, several parameters may influence the process. To help to optimize these parameters, a computational method to simulate the process is proposed in this paper. It was confirmed that this simulation algorithm can represent the distribution phenomenon of debris with good correlation with the unevenness of the workpiece surface produced.
*SURFACE GENERATION MECHANISM IN ELECTRICAL DISCHARGE MACHINING WITH SILICONE POWDER MIXED FLUID
The surface generated by electrical discharge machining (EDM) appears to be generally mat finish. However, the machined surface in EDM with silicon powder mixed fluid becomes glossier and has a smaller surface roughness than that in conventional EDM with kerosene type fluid, which leads to the omission of hand finish lapping of metal molds. The quality of machined surface significantly depends on the kind of workpiece material, but the surface generation mechanism has not yet been made sufficiently clear. In this study, the effect of silicon powder mixing on the surface generation mechanism is experimentally investigated, analyzing the shape of crater generated by a single pulse discharge, the surface roughness, the machined surface and so on. The main coclusions obtained are as follows:
1. The gap distance in EDM with silicon powder mixed fluid
is larger than that with kerosene type fluid, because of the lower resistivity of the former and the influence of silicon powder arrangement in the gap. EDM with silicon powder mixed fluid leads to smaller undulation of a crater, because of the smaller impact force acting on the workpiece due to evaporation and expansion
of machining fluid. 3. The more the precipitated carbides in the workpiece are,
larger the surface roughness is, since the carbides come off because of crack propagation due to the frequent heat impact during EDM.
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