Application of micro-EDM combined with high-frequency dither grinding to micro-hole machining Advisee Jyong-Sian Lai Southern Taiwan University, Tainan, TAIWAN Date ﹕2011/05/30

Outline Experimental design Experimental results and discussion Conclusions

Experimental design

HFDG mechanism

Schematic of HFDG after micro-EDM.

Effect of electrode gap voltage on electrode depletion

Effect of electrode gap voltage on DVEE

Effect of electrode gap voltage on hole expansion

Relationship between dither input voltage and amplitude of dither vibration.

SEM cross-sections of micro-holes after HFDG using circular and stepped circular tools

Fig. 9. The surface roughness of micro-holes cross-section using different peak current of micro-EDM. Fig. 10. SEM cross-sections of micro-holes machined under different peak currents followed by HFDG at 40 V for 15 min.

Entrance of micro-hole machined under 100 mA followed by HFDG at 40 V.

SEM cross-sections of micro-holes machined by HFDG at different input voltage.

SEM cross-sections of micro-holes machined under peak current 500 mA followed by HFDG at 40 V for different duration.

Surface roughness of workpiece before and after HFDG.

Conclusions Conclusions of this study are summarized below. 1. When applying micro-EDM to high-nickel alloy, the peak current must be coupled with the optimum electrode gap voltage in order to achieve precise machining effects. 2. HFDG employs electrode as the lapping tool and involves no dismounting or re-clamping of the microelectrode in the process. This can ensure accurate diameter size and precise geometric shape of the micro-hole machined. 3. Using stepped circular electrode with the addition of alumina slurry in-situ, HFDG can effectively remove discharge craters on the rugged surface after micro-EDM, thus achieving better surface roughness. 4. At 500 mA peak current and 40 V dither voltage, micro-EDM coupled with HFDG can obtain micro-holes of precise shape and smooth surface after 6–8 min of lapping.

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