外文翻譯---電火花線切割工藝進(jìn)給率的控制

1、<p><b>　　附 錄</b></p><p><b>　　英文原文</b></p><p>　　Feed rate control of the wire-EDM process</p><p>　　1、Introduction</p><p>　　The CNC wire-EDM

2、 machines first appears in the market in the 1970s，Although the wire-EDM process has been playing an important role in the tooling and manufacturing industry，especially for the production of punches and dies，The metal re

3、moval process of wire-EDM is very complex with stochastic and time-varying characteristics。 Moreover， many machining conditions such as workpiece properties(material，thickness)，machining settings(wire feed， table feed， f

4、lushing pressure，etc。)and power settings(pul</p><p>　　In order to improve the machining efficiency，stability and quality，many efforts have been made by the researchers and manufacturers to develop pulse disc

5、rimination and control system。Liao et al。developed a pulse discrimination system to study the characteristics of pulse trains in the wire-EDM process。They also proposed an approximate method for estimating the variation

6、of the average gap width。Wire breakage and unstable machining drastically reduce the machining efficiency and accuracy in wire-</p><p>　　2、Feed rate control and the process parameters</p><p>　　T

7、he quality of feed rate control determines the stability of the gap width the machining process。 The following four process variables can be used for feed control：</p><p>　　A、Gap voltage This process charact

8、eristic is average value of the gap voltage。This mean value depending on the different burning voltage levels of spark and arc as well as on the ignition delay time。</p><p>　　The determination of the middle

9、gap voltage and its technical implementation for gap width control isrelatively easy in comparison with other methods。The gap voltage was directly proportional to the working gap width。</p><p>　　B、Ignition d

10、elay timeThe ignition delay time characterizes the conditions for the voltage breakdown of the gap。The theoretical consideration，that a small gap offers better conditions for a breakdown than a large gap leads therefore

11、to shorter ignition delay times。In this way， the ignition delays time can be used as a controlled variable for the feed rate control。The gap conditions at spark erosion are ideal if the voltage breakdown occurs after a s

12、hort ignition delay。Longer ignition delays，the d</p><p>　　The measurement of the ignition delay of the dielectric breakdown has the advantage compared to other procedures that critical states the gap before

13、the actual power pulse can be found，In addition，the disturbance afflicted current and voltage measurements are replaces by time measurement。The start of measurement is given by the generator control。 The time interval en

14、ds with reaching a reference voltage or a reference current。</p><p>　　C、Voltage breakdown The voltage breakdown is characteristic of subsequent discharge because the slope of this breakdown is determined by

15、 the dominating mechanism of conducting。</p><p>　　D、High-frequency parts of the burning voltage The practical investigations show that the spark voltage has a high-frequency part while the arc burning volta

16、ge does not have this one。Using this， process analyses and feed rate controls achieving a sufficiently good machining result were developed。 Today the feed rate control is carried out via the analysis of the above-mentio

17、ned process parameters。 There are hardly problems if a sufficiently good process analysis determines the “critical” process</p><p>　　3、Pulse discriminating and control system</p><p>　　A new puls

18、e discriminating and control system has been developed for wire-EDM process as shown in Fig.1。</p><p>　　Fig.1 The developed pulse discriminating and control system of wire-EDM</p><p>　　In the sy

19、stem，it consists of two parts。Those are gap states examination module and motion control module。 In the Gap states examination module，a high voltage in the gap can be changed into a low voltage by a voltage divider for d

20、igital circuits。There are three voltage levels 70，50 and 10V labeled as Vh，Vm and Vl，respectively。A comparator is used produce three different states by comparing the gap voltage signal。A complex programmable logic devic

21、e(CPLD)，which allows easy modification of the desig</p><p>　　There are four kinds of gap states in the Wire-EDM process。These are open circuit，normal spark，arc discharge and short circuit。When the work piece

22、 and wire electrode contact with each other， the short circuit happens。Arc discharges and short circuits can be caused by poor flushing，gap contamination and short ionization because the spark debris can not be flushed a

23、way and it allow reionization of the dielectric。Arc discharges and short circuits are dangerous to machining process and achieve the s</p><p>　　4、Conclusion</p><p>　　In this paper，a wire-EDM pul

24、se discriminating and control system has been developed for the identification of gap states，more precise on-line quantitative pulse train analysis，machining condition monitoring and process control。From the experimental

25、 results of process monitoring and control， the following conclusions are observed。</p><p>　　A、Discharge pulses can be classified into four pulse types by combining some of the time periods and gap voltage c

26、haracteristics。The proportion of short circuits(short ratio)and the sparking frequency can be used to monitor and evaluate the gap condition。 </p><p>　　B、For controlling the feed rate while spark erosion mac

27、hining the four process variables：middle gap voltage，ignition delay time，high-frequency part of the gap voltage and voltage breakdown are suitable as controlled variables。A combination of process variables has to be used

28、 for powerful control strategies。</p><p>　　C、A feed rate control strategy has been proposed to improve the abnormal machining condition。 Experimental results not only verify the effectiveness of the proposed

29、 control method，they also indicate that the developed pulse discriminating and control system is capable of achieving stable machining under the condition where there exists an unexpected disturbance during machining。<

30、;/p><p><b>　　中文翻譯</b></p><p>　　電火花線切割工藝進(jìn)給率的控制</p><p><b>　　簡介</b></p><p>　　數(shù)控電火花線切割機(jī)在十九世紀(jì)七十年代在市場出現(xiàn)。盡管線切割在模具行業(yè)與制造業(yè)中發(fā)揮了重要的作用，尤其是對(duì)凸模和凹模的制造。線切割的金屬切割工藝是非

31、常復(fù)雜的，而且具有隨機(jī)性，隨時(shí)間不同而具有不同的特點(diǎn)。而且，很多切削條件如工件性能（材料，厚度），切削裝置（送絲，工作臺(tái)進(jìn)給，沖壓力等）和功率設(shè)置（脈沖，脈沖間隔等）對(duì)切削工藝有很大影響。</p><p>　　為了改進(jìn)切削效率，穩(wěn)定性，和質(zhì)量，研究人員和制造者在開發(fā)脈沖識(shí)別和控制系統(tǒng)上做了很大努力。廖等人開發(fā)了一種脈沖識(shí)別系統(tǒng)來研究線切割工藝中脈沖序列的特征。他們也建議一種測量平均距離寬度變化的近似方法。在線切割

32、中金屬絲斷掉和不穩(wěn)定的切削條件會(huì)嚴(yán)重的減少切削效率和精度。用模糊控制方法控制的一些調(diào)適性控制系統(tǒng)利用通過開發(fā)的脈沖識(shí)別和控制系統(tǒng)檢測的傳感參數(shù)來監(jiān)視和控制金屬絲破裂和保持穩(wěn)定的切削條件。盡管這些 自適應(yīng)性控制系統(tǒng)能被應(yīng)用到很大范圍的切削條件，但是當(dāng)有一個(gè)意想不到的干擾時(shí)如在切削一個(gè)階梯形的工件時(shí)，它們不能對(duì)距離條件進(jìn)行準(zhǔn)確的反應(yīng)。為了運(yùn)用具有不同高度的工件的加工工藝，Rajurkar等人提出了一種調(diào)適性控制系統(tǒng)，即通過運(yùn)用多輸入模型估計(jì)

33、工件高度來在線優(yōu)化電火花頻率。這篇論文提出了一種新的計(jì)算機(jī)輔助脈沖識(shí)別和控制系統(tǒng)來監(jiān)測和控制線切割工藝。通過運(yùn)用脈沖識(shí)別和控制系統(tǒng)，我們可以定量分析切削設(shè)置和傳感參數(shù)。根據(jù)以確定的距離狀態(tài)，提出通過實(shí)時(shí)調(diào)整進(jìn)給率來達(dá)到穩(wěn)定的切削狀態(tài)的控制方法被來了。</p><p>　　進(jìn)給率控制和工藝參數(shù)</p><p>　　進(jìn)給率的質(zhì)量控制決定了切削工藝的距離寬度的穩(wěn)定性。下面四種工藝變量可以用來進(jìn)行

34、進(jìn)給控制：</p><p><b>　　縫隙電壓 </b></p><p>　　這個(gè)工藝特性是縫隙電壓的平均值。這個(gè)平均值取決于電火花、電弧和燃燒延遲時(shí)間的不同燃燒電壓水平。中間縫隙電壓的確定和距離寬度控制與其他方法相比比較容易控制。縫隙電壓與工作距離寬度呈正比例關(guān)系。</p><p><b>　　B．引燃延遲時(shí)間 </b&g

35、t;</p><p>　　引燃延遲時(shí)間描述了縫隙間的擊穿電壓情況。理論研究表明，小的縫隙與大的縫隙相比，能提供更好的擊穿條件，因此導(dǎo)致更短的引燃延遲時(shí)間。用這種方法，引燃延遲時(shí)間能作為進(jìn)給率控制的一個(gè)控制變量。如果電壓擊穿發(fā)生在短的引燃延遲之后，電火花侵蝕的縫隙條件是理想的。引燃延遲時(shí)間越大，發(fā)生電弧放電的危險(xiǎn)越大。</p><p>　　與其他實(shí)際功率脈沖被發(fā)現(xiàn)之前的縫隙的臨界值相比，介電

36、擊穿的引燃延遲的測量有其優(yōu)點(diǎn)。而且，影響電流和電壓測量的干擾可以替換為對(duì)時(shí)間的測量。通過控制電動(dòng)機(jī)來開始測量。達(dá)到一個(gè)電壓參考值和電流參考值后時(shí)間間隔停止。</p><p><b>　　C．擊穿電壓 </b></p><p>　　計(jì)算電壓是連續(xù)放電特點(diǎn)，因?yàn)閾舸┑男甭嗜Q于主控系統(tǒng)。</p><p>　　D．燃燒電壓的高頻部分 </

37、p><p>　　實(shí)際研究表明計(jì)算電壓有高頻部分，而電弧的燃燒電壓并沒有高頻部分，利用這一點(diǎn)工藝分析和進(jìn)給速率控制取得相當(dāng)好的切削效果?，F(xiàn)在進(jìn)給速率控制是通過分析上述工藝參數(shù)來實(shí)現(xiàn)的。一個(gè)足夠好的工藝分析決定臨界工藝狀態(tài)，通過工藝控制估計(jì)上述參數(shù)不是問題，新的進(jìn)給率控制必須在最短的時(shí)間內(nèi)適應(yīng)這些非穩(wěn)態(tài)。</p><p>　　3、脈沖識(shí)別與控制系統(tǒng)</p><p>　　為了

38、改進(jìn)電火花線切割工藝，我國開發(fā)了一種新的脈沖識(shí)別系統(tǒng)，如圖1所示：</p><p>　　圖1 研制的電火花線切割脈沖識(shí)別控制系統(tǒng)</p><p>　　這個(gè)系統(tǒng)包括兩個(gè)部分：第一部分是間隙狀態(tài)檢測裝置;第二部分是移動(dòng)控制部分，在間隙狀態(tài)檢測裝置，通過數(shù)字電路分壓器間隙中的高壓可以被變成電壓，有三個(gè)電壓值，它們分別是70、50和10（v），分別在標(biāo)為Vh、Vm、Vl。通過比較間隙電壓信號(hào)可以對(duì)

39、三種不同的狀態(tài)進(jìn)行比較，一個(gè)復(fù)雜的程序邏輯裝置（CPLD）(允許對(duì)其結(jié)構(gòu)稍作調(diào)整，有4MH的晶體振蕩器來計(jì)時(shí))。這種裝置不但用于產(chǎn)生脈沖控制信號(hào)（i.e.P1和P2），也用來區(qū)別間隙的狀態(tài)，個(gè)人微機(jī)常常用來用戶對(duì)接、數(shù)據(jù)的傳輸和計(jì)算。在VC的集成開發(fā)研究環(huán)境下，設(shè)計(jì)用戶界面。</p><p>　　在運(yùn)動(dòng)控制裝置中， PCI—1240芯片通過一個(gè)容量為8KB雙埠隨機(jī)存取存儲(chǔ)器(RAM)連接到PCI總線，實(shí)現(xiàn)與奔騰微

40、機(jī)交換數(shù)據(jù)，它常常通過C語言編程軟件來計(jì)算脈沖寬度。基于這個(gè)結(jié)構(gòu)的基礎(chǔ)上，通過微機(jī)可以同時(shí)顯示、分析和記錄脈沖數(shù)據(jù)。正如圖2顯示，Vg是間隙電壓，Ig是間隙電流，因?yàn)殡娏鳒y量裝置是比較昂貴的，所以間隙電流在識(shí)別系統(tǒng)輸入信號(hào)中不給與考慮。P1是放電電路脈沖控制信號(hào)。Ql，Qm 和 Qh是比較器的輸出狀態(tài)。當(dāng)間隙電壓分別比Vl， Vm 和 Vh更高時(shí)，Ql，Qm 和 Qh的狀態(tài)將是高態(tài)。當(dāng)P1處于高態(tài)和Q1處于高態(tài)時(shí)，時(shí)間在t1階段。當(dāng)Qm

41、保持高態(tài)時(shí)，時(shí)間處于tm階段。當(dāng)間隙狀態(tài)處于空載狀態(tài)時(shí)，t1和tm被測量，這時(shí)它們的值將被記錄，而且標(biāo)記分別為t1s和tms。如圖2所示，當(dāng)間隙狀態(tài)處于一個(gè)空載和一個(gè)火花放電時(shí)，它是很困難區(qū)分，而且也很難區(qū)分一個(gè)弧形火花從一個(gè)短弧火花中僅僅通過三種被標(biāo)識(shí)的電壓V1,Vm和Vh。從圖2中可以看出，短路狀態(tài)t1階段是最長時(shí)間段與其他間隙狀態(tài)相比。此外，tm階段正?；鸹ㄊ敲黠@更短比任何一個(gè)空載。因此，不僅間隙電壓的標(biāo)識(shí)而且時(shí)間段t1和tm都可

42、被</p><p><b>　　表1 信號(hào)邏輯分析</b></p><p>　　圖2脈沖識(shí)別信號(hào)的時(shí)間表</p><p>　　電火花線切割加工過程中會(huì)出現(xiàn)四種不同的間隙狀態(tài)，它們是空載，火花放電，弧形放電，短路。當(dāng)工件電極與線電極相互接觸時(shí)，就會(huì)發(fā)生短路?；⌒畏烹姾投搪房赡軙?huì)引起沖洗不良，間隙不均勻，電離不強(qiáng)，因?yàn)殡娀鸹ㄇ邢餍疾荒鼙粵_洗掉，它會(huì)

43、形成二次放電的介質(zhì)。因?yàn)榛⌒畏烹姾投搪穼?duì)切削加工和獲得穩(wěn)定切削過程是不利的，所以在實(shí)際生產(chǎn)中應(yīng)避免。根據(jù)被確認(rèn)的間隙狀態(tài)，控制部分可以用來實(shí)時(shí)調(diào)節(jié)進(jìn)給率。圖3顯示的為時(shí)間圖的脈沖控制信號(hào)。當(dāng)間隙狀態(tài)被鑒定為空載，火花放電，弧形放電，短路中任何一種狀態(tài)時(shí), Do，Dn，Da 和 Ds則代表識(shí)別電路的輸出信號(hào)。 正如圖3顯示，當(dāng)間隙狀態(tài)被確定為空載或一種正常放電時(shí)，進(jìn)給率被控制在一個(gè)預(yù)定的值以內(nèi)，而當(dāng)間隙狀態(tài)被確定為一種弧形放電或短路狀態(tài)時(shí)

44、，則進(jìn)給率被控制在另一個(gè)預(yù)定的值以內(nèi)，前者的進(jìn)給率比后者更小。</p><p>　　圖3脈沖控制信號(hào)的時(shí)間表</p><p><b>　　4、結(jié)論</b></p><p>　　在這片論文中，為了鑒定脈沖間隙的狀態(tài)，開發(fā)了電火花線切割脈沖識(shí)別與控制系統(tǒng)，為了更多精確的線上量化脈沖序列分析，為了切削狀態(tài)檢測與工藝控制。由工藝檢測與控制的實(shí)驗(yàn)結(jié)果得到

45、如下結(jié)論：</p><p>　　A、根據(jù)時(shí)間與間隙電壓特點(diǎn)放電脈沖可以分為四類，短比率和激發(fā)頻率可以用來檢測和分析間隙的狀態(tài)。</p><p>　　B、在火花腐蝕切削中有四個(gè)工藝變量應(yīng)該進(jìn)行控制：中間間隙電壓、燃燒與延遲時(shí)間、間隙電壓高頻部分、擊穿電壓。工藝變量的結(jié)合不得不用來強(qiáng)有力的控制加工過程。</p><p>　　C、提出進(jìn)給率控制方案是為了改進(jìn)非正常切削狀態(tài)