廖運炫臺灣大學:機械工程學研究所伍國瑋Wu, Guo-WeiGuo-WeiWu2010-06-302018-06-282010-06-302018-06-282009U0001-1408200915293400http://ntur.lib.ntu.edu.tw//handle/246246/187091放電加工向來被視為具有高度的隨機性，本文之目的在於瞭解看似隨機的現象背後是否有隱藏的規律與特徵。自製放電延遲時間(簡稱Td)擷取電路能夠擷取連續16384發放電Td，在固定進給的情況下逐漸提高進給速率觀察到間歇的放電漸漸轉變為正常的連續放電，由此發覺材料的移除步調與工作台進給並非同步，其中暗藏玄機，細查Td序列，但線索仍然不足，於是再進行無進給加工實驗獲得更多線索幫助推斷極間狀況的動態變化，詳細瞭解了極間渣分佈狀況與二次放電在線切割放電加工中所扮演的角色。實際上連續加工幾乎完全是透過動態分佈的放電渣發生二次放電，渣分佈狀況的穩定性決定了加工狀況的穩定與否，並以顯微鏡觀察放電渣尺寸，足以佐證放電渣對極間狀況影響極大。隨後又研究了正常穩定加工時的微觀穩定性，發現即使宏觀來看放電狀況穩定，但微觀來看變動幅度仍然很大，很可能是進一步改善控制的方向，故於文末基於本研究對連續放電現象更進一步的瞭解提出可能改善微觀穩定性的方法。Ignition delay time (Td) has been widely used to research the state between wire electrode and workpiece in wire EDM. This paper focus on the effect between neighbor discharge and how these effect cause macro phenomenon. The non-synchronism between stage feed and material remove rate has been researched, and the role debris distribution play in discharge gap has been understood, also explain the self-stable mechanism of continuous discharge. By observing the spectral and autocorrelation function of ignition delay time series particularly, it shows continuous discharge is not fully stochastic process but with some characteristics, the author describe the main characteristics by a diagram. Finally propose a possible strategy to stabilize the micro discharge state.目錄謝....................................................................................................................................i要...................................................................................................................................iiBSTRACT.....................................................................................................................iii錄..................................................................................................................................iv目錄..............................................................................................................................vi目錄............................................................................................................................viii號說明..........................................................................................................................ix一章 緒論.....................................................................................................................1.1 研究動機................................................................................................................1.2 文獻回顧................................................................................................................2.3 研究目的與研究方法............................................................................................5.4 本文結構................................................................................................................6二章 放電加工原理介紹.............................................................................................7.1 放電加工原理簡介................................................................................................7.2 放電電弧的發展過程............................................................................................9.3 放電火花結構......................................................................................................10.4 放電迴路的種類..................................................................................................12.5 放電參數與放電波形..........................................................................................13.6 快速傅利葉轉換意義簡介..................................................................................16.7 相關係數與自相關函數簡介..............................................................................18三章 實驗設備與實驗設計.......................................................................................22.1 實驗設備架構......................................................................................................22.2 實驗設備與材料..................................................................................................23.3 放電訊號之擷取與處理......................................................................................31四章 實驗結果與討論...............................................................................................34.1 定速切割下初步觀察Td序列.............................................................................34.2 固定進給下發生放電中斷的機制......................................................................37.3 無進給實驗..........................................................................................................40.4 固定進給穩定加工的Td序列.............................................................................48.5 放電狀態的微觀穩定性......................................................................................59五章 結論與展望.......................................................................................................62.1 線切割式放電加工連續放電機制之重新詮釋..................................................62.2 未來展望..............................................................................................................63考文獻.........................................................................................................................64錄A..............................................................................................................................68錄B..............................................................................................................................69者簡歷.........................................................................................................................70目錄2.1 放電加工材料去除機制示意圖........................................................................82.2 引弧過程之電壓電流特性曲線........................................................................92.3 放電火花之結構圖..........................................................................................112.4 雙電源放電迴路示意圖..................................................................................122.5 電晶體式放電之正常電波形說明..................................................................132.6 波形分類..........................................................................................................152.7 範例離散資料..................................................................................................162.8 範例離散資料的頻譜(經過FFT)....................................................................172.9 相關係數的計算公式......................................................................................182.10 相關係數圖例..................................................................................................182.11 自相關函數範例資料序列..............................................................................192.12 自相關函數範例..............................................................................................202.13 原始資料與落後1期的資料所繪成的座標圖...............................................202.14 隨機亂數資料序列..........................................................................................212.15 隨機亂數的自相關函數..................................................................................213.1 實驗設備架構圖..............................................................................................223.2 本實驗所採用的沖水式線切割放電加工機..................................................233.3 PINTEK DP-100 高壓差動示波器探棒........................................................253.4 設備3,4,5之照片.............................................................................................263.5 自製Td擷取電路............................................................................................273.6 擷取連續16384發放電Td程式流程圖.........................................................283.7 擷取斷線前或放電中斷前最後16384發放電Td之程式流程圖.................293.8 KEYENCE雷射掃瞄顯微鏡...........................................................................303.9 訊號流程圖......................................................................................................313.10 波形整形與Td計算......................................................................................323.11 自撰VB程序介面.........................................................................................334.1 F=0.2放電中斷前之Td序列..........................................................................384.2 F=0.3放電中斷前之Td序列..........................................................................394.3 無進給實驗步驟說明......................................................................................404.4 無進給實驗想像上的Td序列變化................................................................414.5 無進給實驗 頭16384發Td序列...................................................................434.6 無進給實驗 尾16384發Td序列...................................................................444.7 Td能非常不連續地劇烈變動可能機制示意圖.............................................464.8 放電渣照片1...................................................................................................474.9 放電渣照片2...................................................................................................474.10 F=0.4穩定加工之Td序列............................................................................484.11 由簡單移動平均線窺見自我穩定機制..........................................................494.12 F=0.4穩定加工下Td序列之頻譜..................................................................504.13 F=0.4穩定加工之Td序列，先轉成100MA，再做FFT..................................514.14 F=0.4穩定加工之Td序列的自相關圖..........................................................524.15 F=0.4穩定加工狀況下細部觀察Td的變化模式(1)......................................534.16 F=0.4穩定加工狀況下細部觀察Td的變化模式(2)......................................534.17 F=0.4穩定加工狀況下細部觀察Td的變化模式(3)......................................544.18 F=0.4穩定加工狀況下細部觀察Td的變化模式(4)......................................544.19 F=0.4穩定加工狀況下細部觀察Td的變化模式(5)......................................554.20 F=0.4穩定加工狀況下細部觀察Td的變化模式(6)......................................554.21 導致長短Td交替特性的可能原因................................................................564.22 F=0.4穩定加工之Td序列的統計分佈圖......................................................574.23 定速穩定加工下Td序列主要特徵示意圖....................................................584.24 穩定加工下的Td序列微觀穩定性................................................................594.25 伺服進給下的Td序列微觀穩定性................................................................604.26 利用Off Time做更細膩的控制......................................................................61目錄3.1 線切割放電加工機可設定的主要參數..........................................................244.1 定速切割實驗參數表......................................................................................344.2 無進給實驗參數表..........................................................................................424755089 bytesapplication/pdfen-US線切割式放電加工放電延遲時間隨機性wire EDMignition delay timeseries analysisstochasticthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/187091/1/ntu-98-R96522727-1.pdf