[畢業(yè)設(shè)計精品]全球電火花活動的有關(guān)研究 英語翻譯(電火花)

1、全球電火花活動的有關(guān)研究曾經(jīng)電火花加工被認(rèn)為是非傳統(tǒng)加工過程，但是電火花在世界范圍內(nèi)許多工業(yè)方面已經(jīng)取代了鉆孔、銑削、磨削和其它傳統(tǒng)加工方法。盡管50年以前的早期它是“tapbusting”的方式，但是電火花已經(jīng)發(fā)展成為最先進(jìn)加工技術(shù)之一?，F(xiàn)代電火花加工設(shè)備運用先進(jìn)的計算機(jī)數(shù)字控制，可達(dá)六軸同時工作和不同的電源技術(shù)。這些能夠作為一面鏡子高精度完成加工。來自世界頂尖研究所和研究中心主要的電火花建設(shè)者和研究者雇傭的許多專業(yè)工程師通過共同努力實現(xiàn)了電火花技術(shù)的巨大先進(jìn)性。這篇報道為學(xué)者、研究所的發(fā)展、專職社會和世界范圍內(nèi)對電火花的先進(jìn)性不斷做出貢獻(xiàn)的其它組織提供了研究綱要。技術(shù)的改革根據(jù)聯(lián)邦實驗協(xié)會

2、調(diào)查，從政府、私人研究中心到工廠有許多帶來技術(shù)轉(zhuǎn)變的渠道。以下就是不同加工技術(shù)應(yīng)用的抽樣調(diào)查：1.工業(yè)和實驗室之間合作性研究項目。2.車間、研究會和簡報。3.獨家的/非獨家的許可。4.工廠為工作設(shè)備設(shè)立實驗室進(jìn)行贊助性研究。5.咨詢實驗室人員。6.實驗室和工廠貿(mào)易為了相互的利益，職員交換任務(wù)。7.在一家具體的公司里，實驗室設(shè)備使用能力不可獲知。8.實驗室參觀、分享信息并討論技術(shù)上的問題。9.出版社和其他的印刷文獻(xiàn)。10.工業(yè)成員與那些和實驗室相關(guān)的組織聯(lián)合在一起。如項目 9 和 10 所定義的,電火花技術(shù)轉(zhuǎn)變(edmtt)的目的之一是從有關(guān)電火花項目的研究中心提供技術(shù)或信息源，而且使這些可得信

3、息有利于電火花過程的任何一個環(huán)節(jié)。由電火花轉(zhuǎn)變技術(shù)出版的一個參考信息是電火花技術(shù)專欄系列，它包括由大學(xué)、電火花制造業(yè)者和其它世界各地技術(shù)研究中心提供的電火花技術(shù)報道。不久以前的目標(biāo)電火花運行時，電極的低溫處理的效果這個計劃嘗試研究電火花運行時，工具電極的低溫處理效果。在俄亥俄州的公司，工件材料和電極的低溫處理是由prm碳化物完成的。在低溫處理時候，材料在77k溫度24小時冷卻到周圍環(huán)境的溫度。已經(jīng)完成了正確對待已處理的金屬線和未處理的金屬線的wedm實驗。實驗時發(fā)現(xiàn)，低溫處理金屬線，使金屬線破壞的危險性減小了30%。關(guān)于電火花沉淀和wedm的實驗性工作一直在繼續(xù)。復(fù)晶體金剛石的電火花線切割(p

4、cd)已經(jīng)實行的一項實驗性研究決定了wed加工過程在運行時參數(shù)設(shè)置的效果。wedm 運轉(zhuǎn)在切削材料的不同層面時，在工作件中，像 pcd和wc這樣的材料,是由實驗和理論共同決定的。熱應(yīng)力的數(shù)學(xué)模型一直在繼續(xù)，它理論上解釋了基于stefan數(shù)學(xué)問題的金剛石晶粒機(jī)械切削。鈹銅合金的wedm這個計劃的主要目的是發(fā)展一個在 wedm 的時候，為不同硬度的鈹銅合金選擇最佳加工參數(shù)設(shè)置的而設(shè)立的數(shù)據(jù)庫。這個計劃由charmilles robofil 100機(jī)器引導(dǎo)。機(jī)器設(shè)定和切削特點之間的關(guān)系如同加工速度、表面粗糙度、切削余量一樣，都是由實驗決定的。機(jī)器參數(shù)設(shè)定需要知道周期、當(dāng)前狀態(tài)、脈動持續(xù)時間、功率、金

5、屬線速度、金屬線拉力和金屬材料。最佳化參數(shù)設(shè)定有兩個目的,也就是取機(jī)制速度最大值和取表面光滑最大值。對于兩者標(biāo)準(zhǔn)的輸入?yún)?shù)數(shù)據(jù)庫正在發(fā)展。使用分開電極放電方法排泄分布電火花沉淀的研究這個計劃的主要目的是研究加工參數(shù)（峰值電流和瞬時脈動）和火花特征的閃爍方法的影響，如加工間隙之間的閃爍效率和幾何分布。峰值電流和瞬時脈動使加工間隙的環(huán)境改變導(dǎo)致閃爍效率和幾何分布。一種火花探視系統(tǒng)的新方法用于獲得火花數(shù)據(jù)。完整的工具被分為許多小部分去識別不同間隙不同領(lǐng)域的每一個電火花?；鸹ㄌ揭暱萍挤椒ㄔ诓煌募庸きh(huán)境下，還能夠有效地用于發(fā)現(xiàn)加工的效率。電火花沉淀模的自適應(yīng)控制系統(tǒng)電火花沉淀過程的電弧損害減少了加工效

6、率、降低了加工表面質(zhì)量和提高了加工成本。這個項目的主要目的是為電火花提高加工過程的穩(wěn)定性、避免電弧損害和增加加工效率，開發(fā)自適應(yīng)的控制系統(tǒng)。在這個項目中，已經(jīng)發(fā)明了數(shù)字化電火花間隙監(jiān)測，用于精確地探測間隙所隔時間效率，包括間隙開始、常態(tài)火花、短暫的電弧、穩(wěn)態(tài)電弧和短路。圖1所示為監(jiān)視器的線路線圖。這個系統(tǒng)的獨有特征是高頻率(hf)的監(jiān)測技術(shù)，它不僅監(jiān)測當(dāng)前的電弧損害，而且也監(jiān)測瞬時電弧視為電弧損害的預(yù)測信號。hf探測是所有edm電弧損害探測技術(shù)中最容易實現(xiàn)的方法。一個自適應(yīng)的控制系統(tǒng)和電火花自動調(diào)節(jié)管理的參考模型已經(jīng)建立了。這些自適應(yīng)的控制系統(tǒng)經(jīng)過電火花間隙監(jiān)視器和時實控制伺服來監(jiān)測間隙參數(shù)。

7、擁有這些系統(tǒng)，在條件差的電火花加工環(huán)境下，生產(chǎn)率都能得到50%的提高。一個使用了pi自動調(diào)節(jié)方法的電火花自動調(diào)節(jié)監(jiān)視器已經(jīng)發(fā)展成為三菱 k35 ed 機(jī)器。這個系統(tǒng)能夠根據(jù)電火花探測間隙參數(shù)自動地調(diào)節(jié)主軸周期縮進(jìn)的周期時間。電弧損害能夠完全地避免，而且與人工設(shè)置跳躍周期相比，生產(chǎn)率提高50%。先進(jìn)電火花線切割控制系統(tǒng)在 wedm 加工過程中，金屬線破壞減少加工效率。這個問題由沿著金屬線的密度高功率所引起的，這被視為電火花頻率和工件高度決定的電火花分布長度的比例。在大多數(shù)wedm設(shè)備里，電火花頻率不能時實監(jiān)視、控制和最佳脈沖時間，從而不能根據(jù)制造者提供的數(shù)據(jù)庫，決定給定高度工件的電火花頻率。這個

8、計劃的主要目的是發(fā)展一個先進(jìn)的wedm監(jiān)測和控制系統(tǒng)，它能夠時實監(jiān)測工件高度的變化和把電火花頻率控制在一個最佳水平。最新發(fā)明的控制系統(tǒng)包括數(shù)字式電火花頻率監(jiān)視器和擁有電源和伺服系統(tǒng)控制的pc主控制器。pc時實監(jiān)控電壓、電火花頻率和根據(jù)工件高度工作臺自動進(jìn)給。這個系統(tǒng)將工作臺進(jìn)給控制在最佳速率，并且根據(jù)工件高度時實調(diào)整脈沖將電火花頻率控制在最佳水平。電火花頻率總是根據(jù)安全性和高效率來進(jìn)行調(diào)整，而且能夠根據(jù)高度變化而變化，從而避免了金屬線損害，維持了最佳切削速度。如圖2所示為切削工件時，在這個系統(tǒng)的控制下，根據(jù)高度變化而時實記錄的數(shù)據(jù)。高度識別誤差為1mm，隨高度變化的識別反應(yīng)誤差為1秒。擁有這個

9、控制系統(tǒng)使數(shù)控編程的生產(chǎn)者和機(jī)器操作員的工作簡化，在切削多種高度的工件時，機(jī)器操作員不需要將工件高度數(shù)據(jù)輸入到機(jī)器中，而且也不必將電源設(shè)置命令輸入數(shù)控程序中。附屬于先進(jìn)材料的電火花磨削的內(nèi)布拉斯加-林肯的大學(xué)的未來計劃先進(jìn)材料的機(jī)械磨削，包括可導(dǎo)電的陶器、燒結(jié)碳化物和多晶體金剛石（pcd），由于它們的高硬度和高韌性 ，機(jī)械效率非常低。電火花加工提供了一個有效的加工先進(jìn)材料的方法。然而，由于電火花加工而造成的表面重鑄層和微裂痕，表面質(zhì)量非常低。這個計劃的目的是發(fā)展電火花磨削加工（edg），配有機(jī)械研磨作用的設(shè)備提高放電環(huán)境和切除加工先進(jìn)材料時的損毀層。如圖3所示的加工過程。這個加工方法是使用焊有

10、金剛石的金屬磨輪作為電極。在加工時，磨輪電極高速旋轉(zhuǎn)，電火花在工件與電極之間間隙釋放，加工間隙由電火花伺服系統(tǒng)控制。初步的實驗研究表明研磨作用不僅能夠提高電火花的表面質(zhì)量，而且能夠通過有效地切除腐蝕層和微粒子和提供高速的常態(tài)放電比例與更好的加工穩(wěn)定性來提高放電間隙的條件。先進(jìn)的時實電火花沉淀的監(jiān)測和控制系統(tǒng)因為石墨電極具有比較高的機(jī)械效率和容易制造，所以它在美國的電火花沉淀操作中應(yīng)用比較廣泛。在有石墨電極的電火花中，電弧損害經(jīng)常發(fā)生，而且很難避免。這個計劃的主要目的是電火花沉淀在使用石墨電極時，發(fā)展一個先進(jìn)的監(jiān)測和控制系統(tǒng)。在這個計劃中,可獲得先進(jìn)的和商業(yè)化的數(shù)字式電火花監(jiān)視器，它將被發(fā)展成為

11、監(jiān)測間隙狀態(tài)間的時間比。神經(jīng)網(wǎng)絡(luò)技術(shù)將會用來分析由電火花監(jiān)測系統(tǒng)得來的間隙電壓、當(dāng)前信號和間隙狀態(tài)的數(shù)據(jù)。神經(jīng)網(wǎng)絡(luò)和模糊邏輯的識別系統(tǒng)在石墨電極的電火花加工過程中，將會發(fā)展成能夠預(yù)測電弧損害的系統(tǒng)。先進(jìn)的控制系統(tǒng)將會發(fā)展為時實控制放電電源、電極工具的自動轉(zhuǎn)換和伺服系統(tǒng)。先進(jìn)材料的電火花電源當(dāng)使用電火花加工耐高溫材料時，包括鎢碳化物、導(dǎo)電陶器、pcd和pcb等材料，放電波形很大程度地影響加工運轉(zhuǎn)過程。大多數(shù)通過商業(yè)可獲得的電火花電源僅僅提供方形放電電流脈沖。但是，使用方形放電脈沖，高溫能量不能夠高度集中，因此，許多先進(jìn)材料包括鎢碳化物和導(dǎo)電陶器的材料切除率非常低。這個計劃被建議發(fā)展成為一個電火花

12、脈沖觸發(fā)器，提供特殊的放電波形以適合先進(jìn)材料的加工。所建議的脈沖電源標(biāo)準(zhǔn)將會發(fā)展成為比商業(yè)上的電火花電源擁有更廣的峰值電流和電壓變化范圍，提供 rc脈沖控制的晶體管和多水平波形。計算機(jī)能夠?qū)Ψ烹姴ㄐ尉幊毯瓦x擇不同的脈沖參數(shù)。不同材料和加工設(shè)備有最佳的波形，將通過熱模型的理論研究和對先進(jìn)材料電火花過程的分析決定波形。加州/戴維斯大學(xué)一些電火花研究領(lǐng)域中,包括(但是不僅僅是)先進(jìn)的電火花控制系統(tǒng)，目的在于增加生產(chǎn)，減少操作注意事項和wedm上的金屬線破壞的研究。德克薩斯a&m大學(xué)電火花的難點在于對加工材料的研究，如鎢碳化物/鈷合成、鈦合金和其它陶器合成材料。 田納西州科技大學(xué)電火花加工的陶瓷材料。

13、日本工業(yè)科學(xué)研究所,東京大學(xué)在教授t. masuzawa的指導(dǎo)下，這個研究所被譽為日本領(lǐng)導(dǎo)級電火花研究所。它們的研究涵蓋了所有的電火花領(lǐng)域，包括：高的表面質(zhì)量、微加工的金屬線電極放電磨削（wedg）、摩爾電火花、電火花閃爍的研究、微孔電火花和其它范圍的電火花研究。工業(yè)科學(xué)研究所、日本科技研究所和toyama大學(xué)聯(lián)合在一起研究和發(fā)展直接的或粘有金剛石的金屬磨的電火花加工。這種方法生產(chǎn)與普通的磨輪方法相比，有較高效率的磨削和較低的磨削力。最近工業(yè)科學(xué)研究所出版的研究有一篇報導(dǎo)，是關(guān)于微孔電火花電極使用壓電平移裝置的發(fā)展。他們也發(fā)展了3軸數(shù)控微電火花，它能夠生產(chǎn)出表面精度高達(dá)0.1毫秒。另外的最近報

14、告報道了在加工不同種類型的碳鋼時，銅電極金屬線的比例研究。據(jù)了解電極金屬線比例很大程度上不僅受結(jié)構(gòu)的影響，而且也受包圍電極的碳層質(zhì)量的影響。如果有電極表面產(chǎn)生足夠厚度的碳層，較低金屬線比例就能很容易實現(xiàn)。 科技大學(xué)nagaoka最近一些研究工作(也和豐田技術(shù)學(xué)院連同日立生產(chǎn)公司一起研究)有一項關(guān)于絕緣體陶瓷的電火花模型的有趣報道。除了有限的電火花方法外，通常只有具有導(dǎo)電性能的陶瓷材料才能用電火花加工。因此，研究者正在研究最近已經(jīng)發(fā)明的使用標(biāo)準(zhǔn)電火花加工的深孔加工和絕緣陶瓷的切削加工方法。日本技術(shù)研究所加工中心調(diào)查電火花沉淀運行的可能性以減少制造壓鑄模所需的加工時間。大阪縣工業(yè)科技研究所 最近大

15、部分工作包括表面整體性研究，它幫助電火花表面實現(xiàn)高性能、抗腐蝕和抗磨損。早期的工作包括變壓器聯(lián)結(jié)線路的發(fā)展，用來穩(wěn)住wedm的電解效果。應(yīng)用力學(xué)的研究所,kyushu 大學(xué)陶瓷材料的加工和陶瓷金屬合金的發(fā)展，使用電火花增加黏結(jié)強(qiáng)度，減少殘留應(yīng)力。豐田技術(shù)學(xué)院通過日本電火花制造業(yè)者的聯(lián)合努力，他們過去的研究在電火花的電介流體中使用硅粉、鋁粉和石墨粉，增強(qiáng)電火花表面光滑度，使其像一面鏡子一樣光潔，這是最早的徹底研究。通過懸浮粉末釋放電流的分散，他們早期的研究使加工表面精度達(dá)到0.8微米甚至更高，但加工時間明顯下降?，F(xiàn)在一些電火花制造業(yè)者在電火花沉淀和線切割中提供一個粉狀混合物電介體系統(tǒng)。最近豐田技

16、術(shù)學(xué)院的大部分工作包括微孔電火花、碳在電火花電極上沉淀的研究、絕緣陶瓷的電火花加工和電極磨損研究。toyama縣大學(xué)最近出版的研究中含一個報告，它是關(guān)于wedm的金屬線彎曲和它如何影響加工精度的研究。金屬線變化是用光學(xué)纖維來測量，正在研究一項電火花脈沖對金屬線的力學(xué)作用的調(diào)查。toyama大學(xué)通過和三菱電力的聯(lián)合努力,最近完成了另一項計劃，它嘗試對電火花線切割溫度分布的測量。盡管wedm由于加工過程中的金屬線破壞，最大切削速度受到限制，然而知道金屬線的真實溫度對于wedm加工速度的發(fā)展是很重要的。金屬線溫度分布是通過wedm釋放的電流和電壓測量的。資訊科技發(fā)現(xiàn)釋放濃度僅僅發(fā)生在金屬線被破壞之前

17、，因此釋放濃度可以作為金屬線破裂的主要原因。結(jié)果也表明平均的金屬線溫度在100左右。岡山大學(xué)最近的旋轉(zhuǎn)圓板電極研究為mrr提高深槽加工能力。鈦、英高鎳和銅合金材料等的其它研究。yamagata 大學(xué)有關(guān)氧化物-超導(dǎo)體的陶瓷的電火花研究。歐洲技術(shù)轉(zhuǎn)變公司(英國伯明罕)transtec把車輛作為大學(xué)和其它工業(yè)制造業(yè)研究所來研究、發(fā)展和銷售先進(jìn)技術(shù)?？茖W(xué)和商業(yè)計劃已經(jīng)在transtec與伯明罕、愛丁堡和諾丁漢之間建立。transtec的研究和發(fā)展集中在下列三個有名的產(chǎn)品種類和控制技術(shù)領(lǐng)域內(nèi)：1.電火花加工2.電化學(xué)加工3.電火花質(zhì)地產(chǎn)品含:柔性加工單元擁有多軸電火花、電火花質(zhì)地加工、電火花無線電電波

18、頻率自適應(yīng)控制、電火花數(shù)控自適應(yīng)控制、ram-type電火花和自適應(yīng)控制系統(tǒng)的數(shù)控電火花鉆孔加工。cul最近的大多數(shù)電火花研究工作包括:電火花的計算機(jī)輔助加工計劃和制造研究計劃的目的是使cad/cam和電火花加工成為一個整體。整體包括特征模型單元的發(fā)展、capp（計算機(jī)輔助過程規(guī)劃）單元的發(fā)展、cam-edm單元（計算機(jī)輔助制造業(yè)）和數(shù)控傳遞過程。在這項研究工作中，已經(jīng)定義了新的特點去完全或部分地描述電火花加工工件。電火花加工熱效應(yīng)的金屬結(jié)構(gòu)學(xué)調(diào)查此研究是為了更好地理解haz的金屬結(jié)構(gòu)和微結(jié)構(gòu)特征，從而提高加工表面質(zhì)量。這個研究有兩個主要的應(yīng)用領(lǐng)域：1.暴露在外的工具的沖擊、彎曲和拉力。當(dāng)前的

19、研究嘗試發(fā)展新的電火花電源，并定義最佳加工和觸發(fā)設(shè)置，以便于完全去除電火花加工過程中的白色層。在 edm 程序的時候。2.暴露在外的工具的磨料磨損和化學(xué)磨損。當(dāng)前的研究嘗試?yán)冒讓拥膬?yōu)點（硬度、耐化學(xué)腐蝕）當(dāng)作一層保護(hù)膜。這個研究需要agie 和 charmilles 技術(shù)的合作。加工刀具和生產(chǎn)工程學(xué)研究所與生產(chǎn)技術(shù)fraunhofer研究所（德國）電火花加工的電拋光鑄模和壓鑄模。水庫電介質(zhì)鍛造模的研究。電火花加工后的陶瓷性能。半導(dǎo)體材料的電火花加工。超級先進(jìn)的電火花加工和提高工具生產(chǎn)的涂料科技。電火花線切割拋光。linkoping大學(xué)(瑞典)為了監(jiān)視電火花加工過程中的放電位置，發(fā)明了一個系統(tǒng)

20、廣泛地分析電火花加工過程。這個方法的使用是基于火花釋放的能量轉(zhuǎn)化為工件中的超聲波脈沖這樣一個猜想。dundee大學(xué)(dundee,蘇格蘭)早期在高頻率ac源的使用上，和三菱電力公司的共同合作(日本名古屋)實現(xiàn)wedm的亞微米表面光潔度。布加勒斯特工藝學(xué)院(羅馬尼亞)為了實現(xiàn)較高性能的電火花加工，研究通過冷卻含氟利昂和氮的電極來改變電極材料的性能。技術(shù)學(xué)會 (布達(dá)佩斯,匈牙利)電火花加工沉淀的計算機(jī)輔助規(guī)劃。中央機(jī)械工程學(xué)會(保加利亞) wedm自適應(yīng)控制系統(tǒng)的研究。結(jié)論這些所列舉大學(xué)的研究計劃只是全世界電火花加工技術(shù)研究結(jié)果的一小部分。美國正在進(jìn)行的電火花研究工作的數(shù)量被認(rèn)為在其它國家之后，如

21、果工業(yè)和政府為研究和其它計劃提供資金加入更多先進(jìn)技術(shù)的積極興趣，那么美國將會擴(kuò)張研究數(shù)量。通過全世界的大學(xué)和研究所的電火花制造業(yè)者和研究者先進(jìn)的研究和發(fā)展集體的共同努力，電火花加工將會朝更高水平的機(jī)器運轉(zhuǎn)和能力方面繼續(xù)發(fā)展。這些一直持續(xù)的計劃將會產(chǎn)生更高機(jī)械性能、更高精密度和更高表面光潔度的電火花加工技術(shù)，為全世界加工刀具工業(yè)提供與其它加工方法無法相比的獨一無二的加工。worldwide research and activities in edmalthough once considered a “nontraditional” machining process, edm has bee

22、n replacing drilling, milling, grinding and other traditional machining operations in many industries throughout the world. since its early days as a “tap busting” method over 50 years ago, edm has developed into one of the most advanced machining technologies. todays edm equipment uses advanced com

23、puter numerical control (cnc) with up to six-axes simultaneous operation and state of-the-art power supply technology, which can produce a mirror surface finish and “split-tenth” accuracy.the tremendous advancements in edm technology have been achieved through the collective efforts of many dedicate

24、d engineers employed by the major edm builders and by researchers from some of the worlds leading institutions and research centers. this report provides an overview of the research studies and developments of these institutions and the activities of professional societies and other organizations th

25、roughout the world that are contributing to the continued advancements of electrical discharge machining.projects conducted over past two yearseffect of cryogenic treatment of electrode on edm performancethis project attempts to study the effect of cryogenic treatment of work and tool electrodes on

26、edm process performance. cryogenic treatment of the work piece material and electrodes (for edm and wedm) was done by rpm carbide, inc. of ohio. during cryogenic treatment, the material is cooled at 77 k for 24 hours and brought back to ambient temperature. experiments on wedm have been carried out

27、using treated wire and untreated wire. it was experimentally found that the risk of wire rupture was reduced by 30% when using cryogenically treated wire. experimental work on die-sinking edm and wedm is continuing. wire edming of polycrystalline diamond (pcd)an experimental study has been carried o

28、ut to determine the effects of parameter settings in a state of the art wed machine on the machining performance. the wedm performance in cutting different layers of materials, such as pcd and wc, in the workpiece have been experimentally and theoretically determined. the mathematical model(s) of th

29、ermal stress for a theoretical explanation of the removal mechanism of diamond grain based on the numerical solution of stefan problem is continuing. wedm of beryllium copper alloysthe main objective of this project is to develop a database of optimal machine parameter settings for machining of bery

30、llium copper alloys of different heights during wedm. this project is conducted with a charmilles robofil 100 wed machine. the relationships between the machine settings and machining characteristics such as machining speed, surface roughness, and overcut are determined experimentally. the machine s

31、etting parameters are charge frequency, charge current, pulse duration, capacitance, wire speed, wire tension and wire material. the optimization of parameter settings consists of two objectives, i.e. to maximize the machining speed and to maximize surface finish. a database of input parameters for

32、both criteria is being developed.study of discharge distributions in die-sinking edm using divided electrode spark detection methodthe principal objective of this project is to study the influence of machining parameters (peak current and pulse on-time) and flushing methods on spark characteristics

33、such as sparking efficiency and geometrical distribution of sparks in the machining gap. peak current and pulse on-time change the machining conditions in the gap leading to changes in the sparking efficiency and spark distribution. a new method of spark detection system is employed to obtain the sp

34、ark data. the solid tool is divided into number of smaller sections to identify each spark in different areas in the gap at different instants. this spark detection methodology can also be effectively used to find the efficiency of machining when subjected to different machining conditions.adaptive

35、control systems for die-sinking edmthe arc damage in the die-sinking edm process reduces the machining productivity, decreases the machined surface quality, and increases the machining cost. the main objective of this project is to develop adaptive control systems for edm to improve the process stab

36、ility, avoid arc damage, and increase the machining rate. in this project, a digital edm gap monitor was developed to precisely detect the time ratios of gap states including gap open, normal spark, transient arc, stable arc and short circuit. the unique feature of this system is the high frequency

37、(hf) detecting technology that detects not only the occurrence of arc damage, but also the transient arc regarded as the forecasting signal of arc damage. the hf detection is the most reliable method in all edm arc damage detecting technologies. a model reference adaptive control system and a self-t

38、uning regulating system for edm have been developed. these adaptive control systems detect gap state parameters through the edm gap monitor and control the servo feed in real-time. the productivity with these control systems has been shown to be improved by 50% when machining under poor flush condit

39、ions. an edm auto jumping controller using the pi self-tuning approach has also been developed on a state-of-the-art mitsubishi k35 ed machine. this system adaptively adjusts the cycle time of the periodical retraction of the main spindle according to the detected edm gap parameters. the arcing dama

40、ge can be completely avoided, and the productivity is improved by 50% as compared to the manually set jumping cycle time.advanced wire-edm control systemin the wedm process, wire rupture reduces the machining rate. this problem is caused by high power density along the wire, which is regarded as the

41、 ratio of sparking frequency to spark distribution length determined by the workpiece height. with most of the state-of-the-art wedm equipment, the sparking frequency can not be on-line monitored and controlled, and an optimal pulse off-time to determine the sparking frequency for a given workpiece

42、height is selected in accordance with manufacturer supplied database. the main objective of this project is to develop an advanced wedm monitoring and control system that monitors on-line the change of workpiece height and control the spark frequency at optimal levels. a recently developed control s

43、ystem consists of a digital spark frequency monitor and a pc used as the main controller with an interface for power generator and servo system control. the pc monitors on-line the gap voltage, spark frequency, and the table feed rate to identify the workpiece height. this system regulates the table

44、 feed at optimal rates and adjusts the pulse off-time in real-time to control the spark frequency at optimal levels determined by the identified workpiece height. the spark frequency is always adjusted at a safe and highly productive level, and is able to follow the change in workpiece height to avo

45、id wire rupture and to maintain an optimal cutting speed. the error of the workpiece height identification is 1 mm and the response of the identification to changes in workpiece height is 1 second. with this control system, procedures of nc programming and machine operations are simplified, and the

46、machine operator does not need to input the workpiece height data into the machine and insert the power generator setting commands into the cnc program when cutting a multiple height workpiece.future projects at the university of nebraska abrasive assisted electrical discharge grinding for machining

47、 advanced materialsthe machining rate with mechanical grinding of advanced materials, including electrically conductive ceramics, sintered carbides, and polycrystalline diamonds (pcd), is very low due to their high hardness and toughness. the edm process provides an effective alternative to machine

48、advanced materials. however, the surface quality generated by edm is poor due to the recast layer and micro-cracks on the machined surface. the objective of this project is to develop an electrical discharge grinding (edg) process with an assistance of mechanical abrasive effects for improving the f

49、lushing condition and removing the damaged layer when machining advanced materials. during machining, the grinding electrode rotates in high speed, the spark discharges take place in the gap between the electrode and workpiece, and the machining gap is controlled by an edm servo system. the prelimin

50、ary experimental study indicates that the abrasive effect not only improves the surface quality of edg, but also improve the gap flushing condition by effectively removing the eroded chips and particles, and providing higher normal spark ratio and better machining stability. advanced on-line monitor

51、ing and control system for die-sinking edmgraphite electrodes are popular for die-sinking edm operations in u.s. industries because of higher machining rates and easy of fabrication. during edm with graphite electrodes, the arc damage occurs frequently and is difficult to avoid. the main objective o

52、f this project is to develop an advanced monitoring and control system for die-sinking edm when using graphite electrodes. in this project, an advanced and commercial available digital edm monitor will be developed to detect the time ratios of gap states. the neural network technology will be used t

53、o analyze the gap voltage and current signals and the data of gap states collected from the edm monitoring system. a neural network and fuzzy logical identification system will be developed to predict the arc damage during the edm process with graphite electrodes. an advanced control system will be

54、developed to control on-line the discharge power, auto-jumping of tool electrode, and the servo system. edm power generator for advanced materialswhen using edm to machine the high thermal resistant materials including tungsten carbide, conductive ceramics, pcd and pcb, the discharge waveforms stron

55、gly influence the process performance. most commercially available edm power generators provide only square discharge current pulses. however, with square discharge pulses, the thermal energy can not be highly concentrated, therefore, the material removal rates for many advanced materials including

56、tungsten carbide and conductive ceramics are very low. this project is proposed to developed an edm pulse generator to provide particular discharge waveforms suitable to machine advanced materials. the prototype of the proposed pulse power generator will be developed to provide the transistor contro

57、lled rc pulse, multi-level waveforms with wider peak current and voltage ranges than current commercially available edm power generators. a computer can program the discharge waveform and select different pulse parameters. the optimal waveforms for different material and machining requirements will

58、be determined by the theoretical study of thermal modeling and analysis of the edm process for advanced materials.university of california/davisresearch in several edm fields, including (but not limited to) advanced edm control systems aimed at increasing production and reducing operator attention and studies in wire breakage on wedm.texas a&m universityedm studies on difficult to machine materials such as tungsten carbide/cobalt composites, titanium diboride or other ceramic composite materials.tennessee technological universitymachining of cera