| Summary: | 碩士 === 高苑科技大學 === 機械與自動化工程研究所 === 105 === General discharge machining could remove the material by the high temperature instantly generated from the conversion of electrical energy to heat energy that it is suitable for processing high-hardness and high-strength materials. Workpiece surface would appear residues after high temperature and the interaction between cold kerosene and extremely hot discharge in the discharge process to result in unstable discharge and cold-hot interaction caused by residues after the processing. The surface therefore would appear defects of shallow pits, pores, cracks, and affected layers, which would badly affect the quality of the workpiece surface roughness.
Discharge machining matched with ultrasonic auxiliary electrodes is mainly used for processing workpieces in this study to further discuss the effect on the workpiece surface roughness. Optimization experiment with Taguchi Method is first utilized for planning 16 sets of experiments, with 4 discharge machining control factors and 1 ultrasound control factor, on discharge machining to seek for major influence parameters on the discharge machining surface integrity. Such major influence parameters are used for the discharge machining experiment on the high speed steel SKH9 to calculate the standard deviation and signal-to-noise ratio. The optimal combination contains three machining methods, with the use of ultrasonic auxiliary electrodes, without using ultrasonic auxiliary electrodes, and traditional default discharge parameters, to compare the workpiece surface roughness. The results reveal that workpieces processed with traditional default discharge parameters appear the worse surface roughness. The surface roughness of the high speed steel SKH9, after the use of ultrasonic auxiliary electrodes, presents smaller standard deviation, reducing about 56.13%, than the one not using ultrasonic auxiliary electrodes, the S/N ratio improves about 4%, and the surface roughness decreases 5.23%.
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