微細放電加工線上監視系統之開發

Abstract

伺服進給控制是微細放電加工中重要的技術。平均間隙電壓值大致可反映出放電狀況，所以目前控制系統多以此值作為伺服控制之依據。本研究發展出一套微細放電加工線上監視系統，此系統包括了差動探棒、資料擷取卡、RC波形鑑別程式、以及個人電腦。研究中先在不同之加工條件下擷取並觀察RC放電波列，從中分類出正常波、電弧波、短路波、以及複合波等四種不同波形，再提出以三種不同電壓準位切割波形，利用在不同準位下波形寬度之組合將波形鑑別的方法，最後依此鑑別邏輯建立出人機介面，讓使用者容易透過此介面了解目前加工狀況。建立出之系統以輸入模擬訊號之方法驗證其功能性，證明此系統符合要求。在微線切割放電加工、微細深孔放電加工、以及微銑削放電加工之實際加工過程中，發現此系統可成功地鑑別其放電波列。在微線切割放電加工以及微銑削放電加工中，其波列組成主要為正常波，且波列組成較穩定；而在微細深孔放電加工中，波列組成隨著加工深度增加而有所變動。隨著微細深孔加工深度漸增，複合波所佔波列之百分比重逐漸上升，而極間狀況惡化時，複合波百分比停止上升而開始下降，其後加工程序即無法繼續進行。因此，此監視系統可應用於日後微細深孔加工伺服控制系統之設計。

The servo feed control is important for micro electrical discharge machining (Micro-EDM) process, and the average gap voltage is commonly taken to reflect discharge condition for this purpose. A system to monitor the process of Micro-EDM is developed and implemented in this paper. The system is composed of a differential probe, a data acquisition card, a RC pulse trains discriminating program and a personal computer. From the observation of the pulse trains obtained under various machining conditions, features of different pulses are sorted, and the pulses can be classified into four types, namely, normal, arc, short, and complex. An approach to distinguish each pulse type in accordance with three pulse durations measured at three pre-determined voltage levels is proposed. The man-machine interface for easy understanding of the machining process is constructed as well. The developed system is verified by using simulated signals. Actual machining by micro wire-EDM, micro-EDM drilling and micro-EDM milling are conducted and their corresponding pulse trains are tested. It is found that the pulse trains can be successfully discriminated. The pulse trains of micro wire-EDM and micro-EDM milling are mainly normal type. The pulse type distribution varies during the process of micro-EDM drilling. It is also noted that the percentage of complex pulse increases monotonically with the depth of drilling. It starts to drop when the gap condition is deteriorated that drilling is no longer possible. Accordingly, this monitoring system is used to design the servo feed control system of micro-EDM drilling process, and it is under way.