本文選題：電火花加工 + 溫度控制　； 參考：《南京航空航天大學》2017年碩士論文

【摘要】：電火花加工是一種不存在宏觀力的特種加工方法,可以加工各種難加工材料、復雜形狀零件和有特殊要求的零件。但是電火花加工也存在電極損耗大、加工過程不穩(wěn)定、仿形精度低和加工表面質量差等缺點,尤其是加工比強度高、熱導率低的難加工材料如鈦合金時,缺點更明顯。針對常規(guī)電火花加工過程中存在的問題,本文提出一種在工具電極上加裝強制散熱系統(tǒng)的冷電極溫度控制加工方法,通過兩極間不對稱散熱控制電極處于較低溫度,使極間快速消電離,降低電弧放電概率,達到改善加工穩(wěn)定性,降低電極損耗,提高仿形精度和表面加工質量的目的。本文主要研究內容如下:(1)設計冷電極結構和溫度控制系統(tǒng),設計搭建單脈沖放電試驗平臺。對熱管型冷電極和半導體制冷片型冷電極裝置進行性能分析,最終選擇半導體制冷片型冷電極組成電極冷卻裝置。設計了電極溫度控制系統(tǒng),能夠對電極溫度進行有效控制。設計搭建了基于放電電流檢測的單脈沖試驗平臺,為研究冷電極電火花加工材料蝕除機理奠定了良好的基礎。(2)分析了電極溫度對極間放電特性的影響。從理論上分析了電極溫度對放電通道半徑、電蝕坑半徑和極間電子發(fā)射電流密度的影響,解釋了冷電極對放電通道的壓縮作用和冷電極低損耗和小間隙的特性。(3)仿真分析電極溫度對極間溫度場的影響,并通過單脈沖試驗驗證仿真結果。建立了電火花極間放電模型,利用ANSYS軟件對不同電極溫度下電火花放電極間溫度場進行有限元分析。分析了電極溫度對電火花加工材料蝕除的影響,仿真結果驗證了冷電極低損耗特性。利用單脈沖試驗平臺進行不同電極溫度下單脈沖放電試驗,研究了電極溫度對電蝕坑形貌的影響。(4)研究了電極溫度對放電間隙的影響。利用單脈沖裝置對極間放電間隙進行檢測,并通過冷電極與常規(guī)電極成型加工對比試驗,表明了降低電極溫度可以使放電間隙變小,進而提高仿形精度。(5)對冷電極電火花加工的工藝性能進行對比分析。進行了冷電極與常規(guī)電極加工鈦合金工藝性能對比試驗,對放電波形、電極損耗、材料去除率、加工表面粗糙度和表面裂紋進行了對比分析,驗證了冷電極加工具有電極損耗較低、加工穩(wěn)定性較好、材料去除率較高和表面加工質量較好的特性。通過冷電極加工航空螺旋錐齒輪試驗,驗證了冷電極具有較高精度的復雜曲面加工能力。
[Abstract]:EDM is a kind of special machining method without macroscopic force. It can process all kinds of difficult materials, complicated shape parts and parts with special requirements. However, EDM also has some disadvantages, such as large electrode loss, unstable machining process, low copying accuracy and poor surface quality, especially when machining materials with high specific strength and low thermal conductivity, such as titanium alloy. In view of the problems existing in conventional EDM, this paper presents a method of controlling the temperature of cold electrode by adding a forced cooling system to the tool electrode, which is controlled by asymmetric heat dissipation between the two poles at a lower temperature. It can quickly deionization between electrodes, reduce the probability of arc discharge, improve the stability of machining, reduce the loss of electrode, and improve the copying accuracy and surface machining quality. The main contents of this paper are as follows: (1) the cold electrode structure and temperature control system are designed and the monopulse discharge test platform is built. The performance of heat tube cold electrode and semiconductor cooling plate cold electrode device is analyzed. Finally, the semiconductor refrigeration sheet cold electrode type is selected to make up the electrode cooling device. The electrode temperature control system is designed, which can effectively control the electrode temperature. A monopulse test platform based on the detection of discharge current is designed and built, which lays a good foundation for studying the erosion mechanism of cold electrode EDM materials. (2) the influence of electrode temperature on the discharge characteristics between electrodes is analyzed. The effects of electrode temperature on discharge channel radius, electroetching pit radius and electron emission current density between electrodes are analyzed theoretically. The effect of cold electrode on discharge channel compression and the characteristics of cold electrode with low loss and small gap are explained. The effect of electrode temperature on the temperature field between electrodes is simulated and the simulation results are verified by monopulse test. The model of discharge between electrodes is established and the finite element analysis of the temperature field between electrodes at different electrode temperature is carried out by ANSYS software. The effect of electrode temperature on EDM material erosion is analyzed. The simulation results verify the low loss characteristics of cold electrode. The influence of electrode temperature on the morphology of electroetching pit was studied by using single pulse test platform. The effect of electrode temperature on discharge gap was studied. By using monopulse device to detect the discharge gap between electrodes, and by comparing the cold electrode with the conventional electrode, it is shown that the discharge gap can be reduced by lowering the electrode temperature. Furthermore, the process performance of cold electrode EDM is compared and analyzed by improving the copying accuracy. The technological properties of titanium alloy processed by cold electrode and conventional electrode were compared and analyzed. The discharge waveform, electrode loss, material removal rate, surface roughness and surface crack were compared and analyzed. The results show that cold electrode machining has lower electrode loss, better processing stability, higher material removal rate and better surface processing quality. The experiments of cold electrode machining of spiral bevel gear show that the cold electrode has high precision and complex curved surface machining ability.
【學位授予單位】：南京航空航天大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG661

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