MC無機械手換刀刀庫設(shè)計【數(shù)控加工中心-12把刀】【3A0】【含CAD高清圖紙和說明書】
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畢 業(yè) 設(shè) 計(論 文)MC無機械手換刀刀庫設(shè)計學生姓名:許 亮學 號:0515011130所在系部:機械工程系專業(yè)班級:指導(dǎo)教師:李兆銓(高工)日 期:二九年六月 畢業(yè)設(shè)計(論文)任務(wù)書系部機械工程系指導(dǎo)教師李兆銓職稱高工學生姓名許亮專業(yè)班級05機制本學號0515011130設(shè)計題目MC無機械手換刀刀庫設(shè)計設(shè)計內(nèi)容目標和要求加工中心(MC)的自動換刀裝置(ATC)通常分為無機械手換刀和有機械手換刀兩類,前者結(jié)構(gòu)較為簡單、緊湊,常用于刀具數(shù)量不太多的MC中。無機械手換刀是利用刀庫與機床主軸的相對運動實現(xiàn)換刀動作的。設(shè)計一個裝有1216把刀具的刀庫,具有兩個直線運動和一個旋轉(zhuǎn)運動,能完成刀具拔、插和交換動作,并考慮刀庫的定位。一 設(shè)計內(nèi)容1 調(diào)研一個加工中心,了解其無機械手換刀刀裝置和結(jié)構(gòu)。2 參照調(diào)研的加工中心,進行刀庫布局總體設(shè)計。畫出機床總體布置圖和刀庫總裝配圖,要有方案分析,不能照抄現(xiàn)有機床。3 設(shè)計該刀庫的一個重要部分,如刀庫的轉(zhuǎn)位機構(gòu)(包括定位裝置,刀具的夾緊裝置等),畫出該部件的裝配圖和主要零件(如殼體、蝸輪、蝸桿等3張以上工作圖。4撰寫設(shè)計說明書。二 設(shè)計要求1 設(shè)計必須獨立完成,要有創(chuàng)造性,不要照抄照搬實習現(xiàn)場的工藝、工裝、設(shè)備等。2設(shè)計繪圖工作總量一般不少于2.5A0,其中用計算機繪圖不少于一張A1,但不超過總繪圖量的一半。3說明書的內(nèi)容應(yīng)是圍繞本人設(shè)計的內(nèi)容進行分析、計算和論證,不要抄書。說明書內(nèi)容一般不少于25頁,建議寫出英文摘要。4其它有關(guān)事項按院、系有關(guān)規(guī)定執(zhí)行。三 參考資料教材:數(shù)控機床 機械工程手冊(第二版)第8、9卷 機械工業(yè)出版社 指導(dǎo)教師簽名 2009-1-10 系部審核2-1畢業(yè)設(shè)計(論文)學生開題報告課題名稱MC無機械手換刀刀庫設(shè)計課題來源生產(chǎn)實踐課題類型AX指導(dǎo)教師李兆銓學生姓名許亮學 號0515011130專業(yè)班級05gb機制1本課題的研究現(xiàn)狀、研究目的及意義本課題開發(fā)設(shè)計的小型加工中心刀庫。隨著數(shù)控技術(shù)的發(fā)展和普及,加工中心的作用越發(fā)突顯它的重要性。為進一步提高數(shù)控機床的加工效率,數(shù)控機床正向著工件在一臺機床一次裝夾即可完成多道工序或全部工序加工的方向發(fā)展,因此出現(xiàn)了各種類型的加工中心機床,如車削中心、鏜銑加工中心、鉆削中心等等。這類多工序加工的數(shù)控機床在加工過程中要使用多種刀具,因此必須有自動換刀裝置,也就是所說的刀庫,以便選用不同刀具,完成不同工序的加工工藝。自動換刀裝置應(yīng)當具備換刀時間短、刀具重復(fù)定位精度高、足夠的刀具儲備量、占地面積小、安全可靠等特性。課題類型:(1)A工程實踐型;B理論研究型;C科研裝置研制型;D計算機軟件型;E綜合應(yīng)用型(2)X真實課題;Y模擬課題;(1)、(2)均要填,如AY、BX等。2-2本課題的研究內(nèi)容本論文是開發(fā)設(shè)計出一種體積小、結(jié)構(gòu)緊湊、價格較低、生產(chǎn)周期短的小型立式加工中心無機械手換刀刀庫。主要完成以下工作: 1 調(diào)研一個加工中心,了解其無機械手換刀刀裝置和結(jié)構(gòu)。2 參照調(diào)研的加工中心,進行刀庫布局總體設(shè)計。畫出機床總體布置圖和刀庫總裝配圖,要有方案分析,不能照抄現(xiàn)有機床。3 設(shè)計該刀庫的一個重要部分,如刀庫的轉(zhuǎn)位機構(gòu)(包括定位裝置,刀具的夾緊裝置等),畫出該部件的裝配圖和主要零件(如殼體、蝸輪、蝸桿等3張以上工作圖。4撰寫設(shè)計說明書。本課題研究的實施方案、進度安排本課題采取的研究方法為:(1)理論分析,參照調(diào)研的加工中心,進行刀庫布局總體設(shè)計。進度安排:2009.3.16-3.20 收集相關(guān)的畢業(yè)課題資料。2009.3.23-3.27 完成開題報告。2009.3.30-4.17 完成畢業(yè)設(shè)計方案的制定、設(shè)計及計算。2009.4.20-5.15 完成刀庫的設(shè)計2009.5.18-5.29 完成畢業(yè)設(shè)計說明書。2009.6.01-6.08 畢業(yè)設(shè)計答辯。2-3已查閱的主要參考文獻1 廉元國,張永洪. 加工中心設(shè)計與應(yīng)用 M. 北京:機械工業(yè)出版社,1995.3 2 惠延波,沙杰.加工中心的數(shù)控編程與操作技術(shù) M. 北京:機械工業(yè)出版社2000.12 3 勵德瑛.加工中心的發(fā)展趨勢 J. 機車車輛工藝,1994,6 4 徐正平.CIMT2001 加工中心評述J. 制造技術(shù)與機床,2001,6 5 劉利. FPC-20VT 型立式加工中心J. 機械制造,1994,7 6 李洪. 實用機床設(shè)計手冊 M. 沈陽:遼寧科學技術(shù)出版社,1999.1 7 劉躍南.機械系統(tǒng)設(shè)計M.北京:機械工業(yè)出版社,1998.8 8 Panasonic 交流伺服電機驅(qū)動器 MINASA 系列使用說明書 9 成大先.機械設(shè)計手冊第四版第 2 卷M. 北京:化學工業(yè)出版社,2001.11 10 成大先.機械設(shè)計手冊第四版第 3 卷M. 北京:化學工業(yè)出版社,2001.11 指導(dǎo)教師意見指導(dǎo)教師簽名: 年 月 日3畢業(yè)設(shè)計(論文)學生申請答辯表課 題 名 稱MC無機械手換刀刀庫設(shè)計指導(dǎo)教師(職稱)李兆銓(高級工程師)申 請 理 由畢業(yè)設(shè)計任務(wù)已完成,說明書已編好。學生所在系部機械工程系專業(yè)班級05gb機制1學號0515011130 學生簽名:許亮 日期:畢業(yè)設(shè)計(論文)指導(dǎo)教師評審表序號評分項目(理工科、管理類)評分項目(文科)滿分評分1工作量外文翻譯152文獻閱讀與外文翻譯文獻閱讀與文獻綜述103技術(shù)水平與實際能力創(chuàng)新能力與學術(shù)水平254研究成果基礎(chǔ)理論與專業(yè)知識論證能力255文字表達文字表達106學習態(tài)度與規(guī)范要求學習態(tài)度與規(guī)范要求15總 分100評語 (是否同意參加答辯) 指導(dǎo)教師簽名: 另附畢業(yè)設(shè)計(論文)指導(dǎo)記錄冊 年 月 日4畢業(yè)設(shè)計(論文)評閱人評審表學生姓名許亮專業(yè)班級05gb機制1學號0515011130設(shè)計(論文)題目MC無機械手換刀刀庫設(shè)計評閱人評閱人職稱序號評分項目(理工科、管理類)評分項目(文科)滿分評分1工作量外文翻譯152文獻閱讀與外文翻譯文獻閱讀與文獻綜述103技術(shù)水平與實際能力創(chuàng)新能力與學術(shù)水平254研究成果基礎(chǔ)理論與專業(yè)知識論證能力255文字表達文字表達106學習態(tài)度與規(guī)范要求學習態(tài)度與規(guī)范要求15總 分100評語 評閱人簽名: 年 月 日5畢業(yè)設(shè)計(論文)答辯表學生姓名許亮專業(yè)班級05gb機制1學號0515011130設(shè)計(論文)題目MC無機械手換刀刀庫設(shè)計序號評審項目指 標滿分評分1報告內(nèi)容思路清新;語言表達準確,概念清楚,論點正確;實驗方法科學,分析歸納合理;結(jié)論有應(yīng)用價值。402報告過程準備工作充分,時間符合要求。103創(chuàng) 新對前人工作有改進或突破,或有獨特見解。104答 辯回答問題有理論依據(jù),基本概念清楚。主要問題回答準確,深入。40總 分100答辯組評語 答辯組組長(簽字): 年 月 日 答辯委員會意見答辯委員會負責人(簽字): 年 月 日6-1畢業(yè)設(shè)計(論文)答辯記錄表學生姓名許亮專業(yè)班級05gb機制1學號0515011130設(shè)計(論文)題目MC無機械手換刀刀庫設(shè)計答辯時間答辯地點答辯委員會名單朱森酉、李兆銓、王海濤、蔣小盼問題1提問人: 問題:回答(要點):問題2提問人: 問題:回答(要點):問題3提問人: 問題:回答(要點):記錄人簽名(不足加附頁)6-2問題4提問人: 問題:回答(要點):問題5提問人: 問題:回答(要點):問題6提問人: 問題:回答(要點):問題7提問人: 問題:回答(要點):問題8提問人: 問題:回答(要點):記錄人簽名7畢業(yè)設(shè)計(論文)成績評定總表學生姓名: 許亮 專業(yè)班級: 05gb機制1畢業(yè)設(shè)計(論文)題目:MC無機械手換刀刀庫設(shè)計成績類別成績評定指導(dǎo)教師評定成績評閱人評定成績答辯組評定成績總評成績40%+20%+40%評定等級注:成績評定由指導(dǎo)教師、評閱教師和答辯組分別給分(以百分記),最后按“優(yōu)(90-100)”、“良(80-89)”、“中(70-79)”、“及格(60-69)”、“不及格(60以下)”評定等級。其中, 指導(dǎo)教師評定成績占40%,評閱人評定成績占20%,答辯組評定成績占40%。文檔包括:說明書一份,31頁,15500字左右.任務(wù)書一份.開題報告一份.翻譯一份.圖紙共6張:A0-刀庫總裝配圖.dwgA0-機床聯(lián)系尺寸圖.dwgA0-槽輪.dwgA0-軸.dwgA1-刀盤.dwgA1-鎖止盤.dwg摘 要隨著數(shù)控技術(shù)的發(fā)展和普及,加工中心的作用越發(fā)突顯它的重要性。為進一步提高數(shù)控機床的加工效率,數(shù)控機床正向著工件在一臺機床一次裝夾即可完成多道工序或全部工序加工的方向發(fā)展,因此出現(xiàn)了各種類型的加工中心機床,如車削中心、鏜銑加工中心、鉆削中心等等。這類多工序加工的數(shù)控機床在加工過程中要使用多種刀具,因此必須有自動換刀裝置,也就是所說的刀庫,以便選用不同刀具,完成不同工序的加工工藝。自動換刀裝置應(yīng)當具備換刀時間短、刀具重復(fù)定位精度高、足夠的刀具儲備量、占地面積小、安全可靠等特性。本論文是開發(fā)設(shè)計出一種體積小、結(jié)構(gòu)緊湊、價格較低、生產(chǎn)周期短的小型立式加工中心無機械手換刀刀庫。首先介紹了國內(nèi)外加工中心研究現(xiàn)狀及發(fā)展趨勢,闡明了本課題研究的目的、意義。然后進一步介紹本小型加工中心刀庫總體結(jié)構(gòu)和各部件方案的選擇,并在此基礎(chǔ)上進行了小型加工中心刀庫的機械結(jié)構(gòu)的設(shè)計計算,主要包括刀盤部件設(shè)計(含刀盤,夾塊,刀爪),刀庫轉(zhuǎn)動定位機構(gòu)設(shè)計(含轉(zhuǎn)臂,槽輪,滾子,鎖止盤),刀庫總體機構(gòu)設(shè)計(含軸承套,軸,箱蓋,箱體)刀庫移動部分設(shè)計。關(guān)鍵詞:數(shù)控系統(tǒng) 加工中心 刀庫AbstractAlong with the numerical control technology development and the popularization, the processing center function reveals its importance even more suddenly. For further enhances the numerical control engine laths the processing efficiency, the numerical control engine laths is clamping to the work piece in an engine laths attire then completes the multi-channel working procedure or the complete working procedure processing direction develops, therefore appeared each kind of type processing center engine laths, ike the turning center, the boring mill processing center, drills truncates center and so on. This kind of working procedure processing numerical control engine laths must use many kinds of cutting tools in the processing process, therefore must have trades the knife installment automatically, also is the knife storehouse which said, in order to select the different cutting tool, completes the different working procedure the processing craft. Trades the knife equipment to have automatically to have trades the knife time short, the cutting tool repetition pointing accuracy high, the enough cutting tool margin, the area small, safe reliable and so on the characteristics. The present paper is the development designs one kind of volume slightly, the structure compact, the price is low, production cycle short small vertical processing center knife storehouse this article. Then further introduced this small processing center knife storehouse overall structure and various parts plan choice, and has carried on the small processing center knife storehouse mechanism design calculation in this foundation, mainly includes the knife storehouse overall organization design, the electrical machinery selection, the knife storehouse rotation detent mechanism design knife storehouse migration part design and so on. Keywords: numerically controlled lathe machining centers cut database目 錄摘要iAbstractii1 緒論1 1.1 國內(nèi)外的研究現(xiàn)狀和發(fā)展趨勢1 1.1.1 當前世界NC機床的研究現(xiàn)狀1 1.1.2 我國數(shù)控機床產(chǎn)業(yè)的發(fā)展狀況2 1.1.3 加工中心的發(fā)展動向3 1.1.4 我國數(shù)控機床研究存在的問題3 1.2 加工中心概論4 1.2.1 自動換刀系統(tǒng)產(chǎn)品化的意義和前景6 1.3 本論文研究的目的和意義6 1.4 本論文完成的主要工作6 2 總體方案的設(shè)計8 2.1 運動方案的設(shè)計8 2.1.1 運動數(shù)目的確定8 2.1.2 運動方案的確定8 2.2 功能部件的設(shè)計方案9 2.2.1 主傳動系統(tǒng)9 2.2.2 進給伺服系統(tǒng)10 2.2.3自動換刀系統(tǒng)11 2.2.4 基礎(chǔ)部件13 2.2.5 數(shù)控系統(tǒng)14 2.2.6 輔助裝置142.3 總體布局142.4 主要技術(shù)參數(shù)14 2.5 小結(jié)16 3 刀庫的設(shè)計17 3.1 刀庫的結(jié)構(gòu)設(shè)計17 3.1.1 刀庫主要參數(shù)的確定17 3.1.2 刀盤部分的設(shè)計17 3.1.3 刀庫轉(zhuǎn)動定位機構(gòu)的設(shè)計18 3.1.4 軸的設(shè)計21 3.1.5 滾動軸承的選擇計算24 3.1.6 鍵的選用與計算25 3.1.7 刀庫的支承部分的設(shè)計25 3.2 刀庫移動部分的設(shè)計26 3.2.1 刀庫支承橫梁和導(dǎo)軌的設(shè)計26 3.2.2 刀庫移動絲杠和電機的選擇27 3.3 刀庫、橫梁的安裝27 3.4 小結(jié)38 結(jié)論29 致謝30 參考文獻31 ivThe MC inorganic manipulator trades the knife knife storehouse designByXu LiangJune 2009NUMERICAL CONTROLNumerical control(NC)is a form of programmable automation in which the processing equipment is controlled by means of numbers,letters,and other symbolsThe numbers,letters,and symbols are coded in an appropriate format to define a program of instructions for a particular workpart or jobWhen the job changes,the program of instructions is changedThe capability to change the program is what makes NC suitable for low-and medium-volume productionIt is much easier to write programs than to make major alterations of the processing equipmentThere are two basic types of numerically controlled machine tools:pointtopoint and continuouspath(also called contouring)Pointtopoint machines use unsynchronized motors,with the result that the position of the machining head Can be assured only upon completion of a movement,or while only one motor is runningMachines of this type are principally used for straightline cuts or for drilling or boring The NC system consists of the following components:data input,the tape reader with the control unit,feedback devices,and the metalcutting machine tool or other type of NC equipmentData input,also called“mantocontrol link”,may be provided to the machine tool manually,or entirely by automatic meansManual methods when used as the sole source of input data are restricted to a relatively small number of inputsExamples of manually operated devices are keyboard dials,pushbuttons,switches,or thumbwheel selectorsThese are located on a console near the machineDials ale analog devices usually connected to a syn-chro-type resolver or potentiometerIn most cases,pushbuttons,switches,and other similar types of selectors aye digital input devicesManual input requires that the operator set the controls for each operationIt is a slow and tedious process and is seldom justified except in elementary machining applications or in special casesIn practically all cases,information is automatically supplied to the control unit and the machine tool by cards,punched tapes,or by magnetic tapeEightchannel punched paper tape is the most commonly used form of data input for conventional NC systemsThe coded instructions on the tape consist of sections of punched holes called blocksEach block represents a machine function,a machining operation,or a combination of the twoThe entire NC program on a tape is made up of an accumulation of these successive data blocksPrograms resulting in long tapes all wound on reels like motion-picture filmPrograms on relatively short tapes may be continuously repeated by joining the two ends of the tape to form a loopOnce installed,the tape is used again and again without further handlingIn this case,the operator simply loads and unloads the partsPunched tapes ale prepared on type writers with special tapepunching attachments or in tape punching units connected directly to a computer systemTape production is rarely error-freeErrors may be initially caused by the part programmer,in card punching or compilation,or as a result of physical damage to the tape during handling,etcSeveral trial runs are often necessary to remove all errors and produce an acceptable working tape While the data on the tape is fed automatically,the actual programming steps ale done manuallyBefore the coded tape may be prepared,the programmer,often working with a planner or a process engineer, must select the appropriate NC machine tool,determine the kind of material to be machined,calculate the speeds and feeds,and decide upon the type of tooling needed. The dimensions on the part print are closely examined to determine a suitable zero reference point from which to start the programA program manuscript is then written which gives coded numerical instructions describing the sequence of operations that the machine tool is required to follow to cut the part to the drawing specificationsThe control unit receives and stores all coded data until a complete block of information has been accumulatedIt then interprets the coded instruction and directs the machine tool through the required motionsThe function of the control unit may be better understood by comparing it to the action of a dial telephone,where,as each digit is dialed,it is storedWhen the entire number has been dialed,the equipment becomes activated and the call is completedSilicon photo diodes,located in the tape reader head on the control unit,detect light as it passes through the holes in the moving tapeThe light beams are converted to electrical energy,which is amplified to further strengthen the signalThe signals are then sent to registers in the control unit, where actuation signals are relayed to the machine tool drivesSome photoelectric devices are capable of reading at rates up to 1000 characters per secondHigh reading rates are necessary to maintain continuous machinetool motion;otherwise dwell marks may be generated by the cutter on the part during contouring operationsThe reading device must be capable of reading data blocks at a rate faster than the control system can process the dataA feedback device is a safeguard used on some NC installations to constantly compensate for errors between the commanded position and the actual location of the moving slides of the machine toolAn NC machine equipped with this kind of a direct feedback checking device has what is known as a closed-loop systemPositioning control is accomplished by a sensor which,during the actual operation,records the position of the slides and relays this information back to the control unitSignals thus received ale compared to input signals on the tape,and any discrepancy between them is automatically rectifiedIn an alternative system,called an openloop system,the machine is positioned solely by stepping motor drives in response to commands by a controllersThere are three basic types of NC motions, as follows: Point-to-point or Positional Control In point-to-point control the machine tool elements (tools, table, etc.) are moved to programmed locations and the machining operations performed after the motions are completed. The path or speed of movement between locations is unimportant; only the coordinates of the end points of the motions are accurately controlled. This type of control is suitable for drill presses and some boring machines, where drilling, tapping, or boring operations must be performed at various locations on the work piece. Straight-Line or Linear Control Straight-Line control systems are able to move the cutting tool parallel to one of the major axes of the machine tool at a controlled rate suitable for machining. It is normally only possible to move in one direction at a time, so angular cuts on the work piece are not possible, consequently, for milling machines, only rectangular configurations can be machined or for lathes only surfaces parallel or perpendicular to the spindle axis can be machined. This type of controlled motion is often referred to as linear control or a half-axis of control. Machines with this form of control are also capable of point-to-point control.Continuous Path or Contouring Control In continuous path control the motions of two or more of the machine axes are controlled simultaneously, so that the position and velocity of the can be tool are changed continuously. In this way curves and surfaces can be machined at a controlled feed rate. It is the function of the interpolator in the controller to determine the increments of the individual controlled axes of the machines necessary to produce the desired motion. This type of control is referred to as continuous control or a full axis of control.Some terminology concerning controlled motions for NC machines has been introduced. For example, some machines are referred to as four-or five-or even six-axis machines. For a vertical milling machine three axes of control are fairly obvious, these being the usual X, Y, Z coordinate directions. A fourth or fifth axis of control would imply some form of rotary table to index the work piece or possibly to provide angular motion of the work head. Thus, in NC terminology an axis of control is any controlled motion of the machine elements (spindles, tables, etc). A further complication is use of the term half-axis of control; for example, many milling machines are referred to as 2.5-axis machine. This means that continuous control is possible for two motions (axes) and only linear control is possible for the third axis. Applied to vertical milling machines, 2.5axis control means contouring in the X, Y plane and linear motion only in the Z direction. With these machines three-dimensional objects have to be machined with water lines around the surface at different heights. With an alternative terminology the same machine could be called a 2CL machine (C for continuous, L for linear control). Thus, a milling machine with continuous control in the X, Y, Z directions could be termed be a three-axis machine or a 3c machine, Similarly, lathes are usually two axis or 2C machines. The degree of work precision depends almost entirely upon the accuracy of the lead screw and the rigidity of the machine structureWith this systemthere is no self-correcting action or feedback of information to the control unitIn the event of an unexpected malfunction,the control unit continues to put out pulses of electrical currentIf,for example,the table on a NC milling machine were suddenly to become overloaded,no response would be sent back to the controllerBecause stepping motors are not sensitive to load variations,many NC systems are designed to permit the motors to stall when the resisting torque exceeds the motor torqueOther systems are in use,however,which in spite of the possibility of damage to the machine structure or to the mechanical system,ale designed with special hightorque stepping motorsIn this case,the motors have sufficient capacity to“overpowerthe system in the event of almost any contingency The original NC used the closedloop systemOf the two systems,closed and open loop,closed loop is more accurate and,as a consequence,is generally more expensiveInitially,openloop systems were used almost entirely for light-duty applications because of inherent power limitations previously associated with conventional electric stepping motorsRecent advances in the development of electro hydraulic stepping motors have led to increasingly heavier machine load applications.數(shù)控技術(shù)數(shù)控是可編程自動化技術(shù)的一種形式,通過數(shù)字、字母和其他符號來控制加工設(shè)備。數(shù)字、字母和符號用適當?shù)母袷骄幋a為一個特定工件定義指令程序。當工件改變時,指令程序就改變。這種改變程序的能力使數(shù)控適合于中、小批量生產(chǎn),寫一段新程序遠比對加工設(shè)備做大的改動容易得多。數(shù)控機床有兩種基本形式:點位控制和連續(xù)控制(也稱為輪廓控制)。點位控制機床采用異步電動機,因此,主軸的定位只能通過完成一個運動或一個電動機的轉(zhuǎn)動來實現(xiàn)。這種機床主要用于直線切削或鉆孔、鏜孔等場合。數(shù)控系統(tǒng)由下列組件組成:數(shù)據(jù)輸入裝置,帶控制單元的磁帶閱讀機,反饋裝置和切削機床或其他形式的數(shù)控設(shè)備。數(shù)據(jù)輸人裝置,也稱“人機聯(lián)系裝置”,可用人工或全自動方法向機床提供數(shù)據(jù)。人工方法作為輸人數(shù)據(jù)唯一方法時,只限于少量輸入。人工輸入裝置有鍵盤,撥號盤,按鈕,開關(guān)或撥輪選擇開關(guān),這些都位于機床附近的一個控制臺上。撥號盤通常連到一個同步解析器或電位計的模擬裝置上。在大多數(shù)情況下,按鈕、開關(guān)和其他類似的旋鈕是數(shù)據(jù)輸入元件。人工輸入需要操作者控制每個操作,這是一個既慢又單調(diào)的過程,除了簡單加工場合或特殊情況,已很少使用。幾乎所有情況下,信息都是通過卡片、穿孔紙帶或磁帶自動提供給控制單元。在傳統(tǒng)的數(shù)控系統(tǒng)中,八信道穿孔紙帶是最常用的數(shù)據(jù)輸入形式,紙帶上的編碼指令由一系列稱為程序塊的穿孔組成。每一個程序塊代表一種加工功能、一種操作或兩者的組合。紙帶上的整個數(shù)控程序由這些連續(xù)數(shù)據(jù)單元連接而成。帶有程序的長帶子像電影膠片一樣繞在盤子上,相對較短的帶子上的程序可通過將紙帶兩端連接形成一個循環(huán)而連續(xù)不斷地重復(fù)使用。帶子一旦安裝好,就可反復(fù)使用而無需進一步處理。此時,操作者只是簡單地上、下工件。穿孔紙帶是在帶有特制穿孔附件的打字機或直接連到計算機上的紙帶穿孔裝置上做成的。紙帶制造很少不出錯,錯誤可能由編程、卡片穿孔或編碼、紙帶穿孔時的物理損害等形成。通常,必須要試走幾次來排除錯誤,才能得到一個可用的工作紙帶。 雖然紙帶上的數(shù)據(jù)是自動進給的,但實際編程卻是手工完成的,在編碼紙帶做好前,編程者經(jīng)常要和一個計劃人員或工藝工程師一起工作,選擇合適的數(shù)控機床,決定加工材料,計算切削速度和進給速度,決定所需刀具類型,仔細閱讀零件圖上尺寸,定下合適的程序開始的零參考點,然后寫出程序清單,其上記載有描述加工順序的編碼數(shù)控指令,機床按順序加工工件到圖樣要求??刂茊卧邮芎蛢Υ婢幋a數(shù)據(jù),直至形成一個完整的信息程序塊,然后解釋數(shù)控指令,并引導(dǎo)機床得到所需運動。為更好理解控制單元的作用,可將它與撥號電話進行比較,即每撥一個數(shù)字,就儲存一個,當整個數(shù)字撥好后,電話就被激活,也就完成了呼叫。 裝在控制單元里的紙帶閱讀機,通過其內(nèi)的硅光二極管,檢測到穿過移動紙帶上的孔漏過的光線,將光束轉(zhuǎn)變成電能,并通過放大來進一步加強信號,然后將信號送到控制單元里的寄存器,由它將動作信號傳到機床驅(qū)動裝置。有些光電裝置能以高達每秒1000個字節(jié)的速度閱讀,這對保持機床連續(xù)動作是必須的,否則,在輪廓加工時,刀具可能在工件上產(chǎn)生劃痕。閱讀裝置必須要能以比控制系統(tǒng)處理數(shù)據(jù)更快的速度來閱讀數(shù)據(jù)程序塊。反饋裝置是用在一些數(shù)控設(shè)備上的安全裝置,它可連續(xù)補償控制位置與機床運動滑臺的實際位置之間的誤差。裝有這種直接反饋檢查裝置的數(shù)控機床有一個閉環(huán)系統(tǒng)裝置。位置控制通過傳感器實現(xiàn),在實際工作時,記錄下滑臺的位置,并將這些信息送回控制單元。接受到的信號與紙帶輸入的信號相比較,它們之間的任何偏差都可得到糾正。在另一個稱為開環(huán)的系統(tǒng)中,機床僅由響應(yīng)控制器命令的步進電動機驅(qū)動定位,工件的精度幾乎完全取決于絲杠的精度和機床結(jié)構(gòu)的剛度。有幾個理由可以說明步進電機是一個自動化申請的非常有用的驅(qū)動裝置。對于一件事物,它被不連續(xù)直流電壓脈沖驅(qū)使,是來自數(shù)傳計算機和其他的自動化的非常方便的輸出控制系統(tǒng)。當多數(shù)是索引或其他的自動化申請所必備者的時候,步進電機對運行一個精確的有角進步也是理想的。因為控制系統(tǒng)不需要監(jiān)聽就提供特定的輸出指令而且期待系統(tǒng)適當?shù)胤磻?yīng)的公開- 環(huán)操作造成一個回應(yīng)環(huán),步進電機是理想的。 一些工業(yè)的機械手使用高抬腿運步的馬乘汽車駕駛員,而且步進電機是有用的在數(shù)字受約束的工作母機中。 這些申請的大部分是公開- 環(huán) ,但是雇用回應(yīng)環(huán)檢測受到驅(qū)策的成份位置是可能的。 環(huán)的一個分析者把真實的位置與需要的位置作比較,而且不同是考慮過的錯誤。 那然后駕駛員能發(fā)行對步進電機的電脈沖,直到錯誤被減少對準零位。在這個系統(tǒng)中,沒有信息反饋到控制單元的自矯正過程。出現(xiàn)誤動作時,控制單元繼續(xù)發(fā)出電脈沖。比如,一臺數(shù)控銑床的工作臺突然過載,阻力矩超過電機轉(zhuǎn)矩時,將沒有響應(yīng)信號送回到控制器。因為,步進電機對載荷變化不敏感,所以許多數(shù)控系統(tǒng)設(shè)計允許電機停轉(zhuǎn)。然而,盡管有可能損壞機床結(jié)構(gòu)或機械傳動系統(tǒng),也有使用帶有特高轉(zhuǎn)矩步進電機的其他系統(tǒng),此時,電動機有足夠能力來應(yīng)付系統(tǒng)中任何偶然事故。最初的數(shù)控系統(tǒng)采用開環(huán)系統(tǒng)。在開、閉環(huán)兩種系統(tǒng)中,閉環(huán)更精確,一般說來更昂貴。起初,因為原先傳統(tǒng)的步進電動機的功率限制,開環(huán)系統(tǒng)幾乎全部用于輕加工場合,最近出現(xiàn)的電液步進電動機已越來越多地用于較重的加工領(lǐng)域。
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