| Summary: | 碩士 === 龍華科技大學 === 機械工程系碩士班 === 106 === In this study, a micro electro-discharge system was used to trim a 300-μm tungsten carbide electrode (WC) into a 200-μm one by the technique of wire electro-discharge grinding (WEDG). The characteristics of micro electro-discharge milling were investigated by conducting micro-discharge milling (slot size 200 μm × depth 20 μm × length 600 μm) upon the workpiece of high speed steel (SKH 59). By using Taguchi method, L9 (34) orthogonal array, signal-to-noise ratio (S/N), and analysis of variance (ANOVA), the effect of micro electro-discharge milling parameters combination (Discharge current 0.2~1.0 Ampere, Pulse duration 6~25 μs, Pulse off 3~13 μs, Jumping distance 5~15 mm) on the characteristics of micro electro-discharge milling (electrode removal rate, material removal rate and overcutting amount) is discussed. By using the Grey-Taguchi Method analysis, characteristics of multiple qualities were obtained as well as the optimal combination of micro electro-discharge milling parameters (discharge current 0.2 Ampere, pulse time 25 μs, pulse rest time 3 μs, slag height 5 mm). The results showed that the electrode removal rate was reduced from 8.0×10-6 mm3/min to 4.0×10-6 mm3/min (improvement rate 50%), the material removal rate was increased from 1.94×10-4 mm3/min to 1.96×10- 4 mm3/min (improvement rate 1.03%), and the undercutting amount was reduced from 7.5×10-3 mm to 7.3×10-3 mm (improvement rate 2.67%).
The Ag and Cu thin films were deposited on the WC microelectrode by a sputtering system. Sputtering parameters are DC power (100 W), working pressure (1×10−2 torr), pulse time (3 μs), pulse frequency (30 kHz), film deposition rate ~10 nm/min, deposited film thickness ~300 Nm. The results show that the conductivity of Ag and Cu thin film microelectrodes is better than that of uncoated WC microelectrodes, which can effectively improve the characteristics of micro electro-discharge milling.
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