於高品質的塑膠產品上進行後處理加工已是目前製造業的趨勢。由於傳統加工法不易在塑膠材料上加工非圓形特徵如四個角均為直角的方孔，而塑膠為不導電材質，無法使用線切割和放電加工等非傳統加工方式進行加工。因此本論文之目的為研究使用超音波加工技術在塑膠材料上製作方孔，我們是以壓克力材料做為研究對象。加工機台係自行組裝之單軸超音波加工機，主要是由超音波主軸、單軸線性運動平台、磨料供應系統和力量量測系統所組成。本研究並自行設計與製造超音波刀具，因為刀具幾何及質量都會影響系統的共振頻率，所以在設計階段我們使用有限元素分析軟體作為輔助工具。為了提升加工壓克力之效率，我們使用田口方法來進行實驗以決定加工時的最佳製程條件，控制因子分別為磨料種類、進給率、刀具材質及刀頭設計，實驗結果為面積擴大比，即我們希望加工出方孔的面積和由刀具截面積及磨料大小所計算出來的面積越接近越好。使用變異數去分析實驗結果顯示四個控制因子皆為影響面積擴大比的顯著因子，其中磨料種類有最大之貢獻度約76 %，刀具材質貢獻度最小約2 %，其餘二因子之貢獻度在7-8 %間。將實驗結果轉為信號雜訊比，然後再進行變異數分析，可知降低實驗結果變異的最佳因子組合為:磨料種類為氧化鋁、進給率為0.02 mm/s、刀具材質為不銹鋼、以及刀頭類型為尖頭。

Post-processing on plastic products of quality has become the trend in current manufacturing. Because it is difficult to create non-circular features, such as square holes with sharp corners, on plastic materials with traditional machining, and the non-conductive plastic cannot be processed with non-traditional machining such as wire electrical discharging machining or electrical discharge machining, the objective of this research was to study the uses of ultrasonic machining on plastic materials to fabricate square holes. PMMA was selected to be the material of the plastics. The ultrasonic machine tool used in this research was a self-made one-axis ultrasonic machine, which consists of an ultrasonic spindle, a one-axis linear motion platform, a slurry supply system, and a force measurement system. Because the resonance frequency of the ultrasonic system is influenced by the geometry and the mass of the ultrasonic tool, finite element analysis software was utilized as a tool at the design stage. In order to increase the efficiency of processing PMMA, Taguchi’s methods were used in the experiment to determine the optimal machining conditions. Control factors are types of abrasive, feed rate, tool materials, and types of tool. Accuracy is the target of the experiment. Results from analysis of variance show that types of abrasive, feed rate, tool materials, and types of tool are significant factors. Furthermore, types of abrasive had the greatest contribution. According to the single-to-noise ratio results, we can obtain the optimal factor combination, for which abrasive is Al2O3, the feed rate is 0.02 mm/s, the tool material is stainless steel, and the tool design is pointed.

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