進度報告 學校 : 南台科技大學 報告者 : 陳思懿 報告日期 : /15

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Figure 1.Schematic diagram of experimental apparatus. Wire electrode :brass ψ0.2mm Workpiece: polysilicon 15X15X15mm 3/15

discharge waveform1/2 Figure 2. Waveform of wire electric discharging when cutting polysilicon (V = 240v, pulse-on time = 8μs,pulse-off time = 25μs) 4/15

discharge waveform2/2 Figure 4. Waveforms of WEDM with single and dual pulse voltage power. (Pulse-on time = 8μs, Pulse-off time = 25μs) 5/15

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Fig. 5. WEDM of insulating ceramics. 7/15

discharge waveform Fig. 6. Continuously discharge waveform. 8/15

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Table 1 Adjustable parameters of the WEDM machine Items Range _________________________________________________ workpiece: SKD11 tool steel wire electrode: brass, φ 0.25 mm wire feed: 7 m/min wire tension: 1000 gf upper water pressure: 6.5 bar lower water pressure: 11 bar On-time: 0.1–0.9 ms (9 steps) Off-time: 8–50 ms (43 steps) Arc on-time: 0.1–0.5 ms (5 steps) Arc off-time: 9–50 ms (42 steps) Servo voltage: 30–70 V Feed rate over-ride: 0-310% Wire speed: 1–15 mm/min (15 steps) Wire tension: 500–2500 gf (15 steps) 10/15

discharge waveform1/4 Fig. 7. (a) Real feed rate, (b) average gap voltage and (c) total sparking frequency with a gap voltage control system when cutting a workpiece with a sudden increase in height. 11/15

discharge waveform2/4 Fig. 8. (a) Real feed rate, (b) average gap voltage and (c) total sparking frequency with a gap voltage control system when cutting a workpiece with a sudden decrease in height. 12/15

discharge waveform3/4 Fig. 11. (a) Real feed rate, (b) average gap voltage and (c) total sparking frequency with adaptive parameters setting when cutting a workpiece with a step decrease in height. 13/15

discharge waveform4/4 Fig. 12. (a) Real feed rate, (b) average gap voltage and (c) total sparking frequency with adaptive parameters setting when cutting a workpiece with a step increase in height. 14/15

Conclusions With respect to polysilicon polishing with single pulse voltage power higher open voltage improves cutting speed at the expense of wider grooves after machining. The reason for this is that greater open voltage leads to greater electric field and easier insulation breakthrough. Long discharges are usually observed in case of EDM of high- resistance materials. 15/15