| 摘要: | 由於陶瓷具有高硬度、高強度、耐磨耗、易脆等加工特性，使其難以採傳統之切削方式加工，放電加工 (EDM; Electrical Discharge Machining) 加工過程中不會受到材料機械性質影響，故本實驗採超音波輔助複合介電液中添加鋁粉的方式對二氧化鋯陶瓷進行放電加工實驗，加工參數為超音波功率段數(Ultrasonic Power Level)、高壓電流(High Voltage Current)、放電週期時間(Pulse Duration)與低壓電流(Low Voltage Current) ，以了解各個實驗參數對二氧化鋯陶瓷工件放電加工結果之影響，而加工品質特性則包括有加工時間、加工深度、溝槽槽寬、電極損耗量及表面粗糙度，實驗後係以影像測定儀對加工深度進行量測，再以雷射共軛焦表面形貌量測儀進行表面粗糙度及加工槽寬的量測，另使用掃描式電子顯微鏡觀察加工後表面形貌，使用X射線能量散布分析儀對加工區元素進行分析，探討各加工參數對二氧化鋯陶瓷放電加工之加工品質特性之影響。
實驗之結果顯示，在超音波功率輔助下，利用其泵吸作用有助於添加鋁粉之介電液進入加工區域內及利於排渣，降低加工過程中集中放電的發生，能獲得較佳加工後之工件表面粗糙度，且高壓電流與低壓電流大小對加工時間、加工深度、加工槽寬有顯著之影響，而放電週期時間則對表面粗糙度有顯著之影響，於本研究最佳的加工參數組合下，即為超音波功率2段、高壓電流2.4A、放電週期時間50μs及低壓電流1A，獲得1.23μmRa之加工後表面粗糙度，比超音波功率段數0時之表面粗糙度1.41μmRa下降了12.7%，本實驗結果可作為後續加工非導電材料之參考依據。
;Due to their high hardness, high strength, favorable wear resistance, and brittleness, ceramics are difficult to process by using conventional cutting methods. In electrical discharge machining (EDM), the mechanical properties of the material being machined do not affect the machining. This experiment was conducted to investigate the effect of adding aluminum powder to a composite dielectric fluid used in the ultrasonic vibration assisted EDM of zirconia ceramic. The effects of processing parameters ultrasonic power level, high voltage current, pulse duration, and low voltage current on the results of EDM for zirconia ceramic workpieces were investigated. The quality characteristics of the machining included the machining time, machining depth, kerf width, electrode wear quantity, and surface roughness.
The machining depth was measured using an optical measuring instrument, whereas the surface roughness and kerf width were measured using laser scanning confocal microscopy. The surface morphology after machining was observed using a scanning electron microscope, and the elements in the processing zone were analyzed using an energy-dispersive X-ray spectrometer.
The experimental results revealed that when ultrasonic power assistance was applied, the pumping effect facilitated the infiltration of the machining zone by the aluminum powder-enhanced dielectric fluid and helped discharge debris. This led to less-concentrated discharge during EDM, resulting in more favorable surface roughness of the machined workpieces. Additionally, the magnitudes of the high voltage current and low voltage current significantly affected the machining time, machining depth, and kerf width, and the pulse duration strongly affected the surface roughness.
The optimal combination of processing parameters was determined to be an ultrasonic power level of 2, high voltage current of 2.4 A, pulse duration of 50 μs, and low voltage current of 1 A. This combination resulted in a post machining surface roughness of 1.23 μmRa. The surface roughness achieved without any ultrasonic power stages was 1.41 μmRa; thus, the assistance achieved a 12.7% reduction in roughness. The results of this experiment can serve as a reference for the subsequent processing of nonconductive materials. |
