外文翻譯--電動機和數(shù)控技術(shù)

1、<p>　　Motors and Numerical Control</p><p>　　Motors change electrical energy into mechanical energy .</p><p>　　This is simply the mechanical forces between magnets .when two magnets (or elec

2、tromagnets)approach each other ,one will be either pulled toward or pushed away from the other .</p><p>　　1.CONSTRUCTION</p><p>　　Each type of motor is built to do its own special job .All of th

3、em have two main parts .One part is called the stator .The stator is stationary ;it does not move .The other part ,the rotor ,is mounted on bearings so it can rotate .The rotor shaft sticks out beyond the housing .For a

4、motor ,the rotor shaft is coupled to a mechanical load .</p><p><b>　　2.MOTORS</b></p><p>　　The power input to a motor is electrical .Voltage is applied to a motor’s terminals resulti

5、ng in a current .The power output of a motor is mechanical .This power is transmitted by the rotor shaft as a torque .This torque tends to rotate a load , such as a fan or pump .</p><p>　　As a motor drives

6、a load , mechanical power is drawn from the motor .The motor ,in turn ,draws electrical power from the source at the same rate </p><p>　　3.NUMERICAL CONTROL</p><p>　　The major disadvantage of m

7、achine tool automation thus far described lies in the economics of the process .It is expensive to tool a installations for automatic production .Therefore ,unless the part is to be made in very large numbers ,the cost b

8、ecomes prohibitive .Great need exists for a method that permits rapid automatic production ,economical in job-lot amounts .The answer has been found in the numerical control of machine tools .</p><p>　　Compu

9、ter Numerical Control .Numerical control (NC) is a form of programmable automation in which the processing equipment is controlled by means of numbers ,letters ,and other symbols .The numbers ,letters ,and symbols are co

10、ded in an appropriate format to define a program of instructions for a particular workpiece or job .When the job changes ,the program of the particular workpiece changes .The capability to change the program is what mak

11、es NC suitable for low-volume and medium-volume product</p><p>　　There is a wide area of performance duplication between numerical control and automatics .Numerical control , however ,offers more flexibility

12、 ,lower tooling cost ,quicker changes ,and less machine down-time .</p><p>　　In machining contours ,numerical control can mathematically translate the defined curve into a finished product ,saving time and e

13、liminating templates .This can in turn improve accuracy .Another advantage appears to be great saving of machine time ,the equivalent og increasing productive capacity with no increase in facilities .</p><p>

14、;　　Numerical control (N/C) is a form of programmable automation in which the processing equipment is controlled by means of numbers , letters ,and other symbols .The numbers ,letters ,and symbols are coded in an qppropri

15、ate format to define a program of instructions for a particular workpart or job .When the job changes ,the program of instructions is changed .The capability to change the program is what makes N/Csuitable for low-and me

16、dium-volume production .It is much easier to write programs tha</p><p>　　There are two basic types of numerically controlled machine tools :point-to-point and continuous-path (also called contouring).Point-t

17、o-point machines use unsynchronized motors ,whit the result that the position of the machining head can be assured only upon completion of a movement ,or while only one motor is running .</p><p>　　The N/C sy

18、stem consists of the following components :data input ,the tape reader with the control unit ,feedback devices ,and the metal-cutting machine toll or other type of N/C equipment .</p><p>　　Data input ,also c

19、alled “man-to-control link” ,may be provided to the machine tool manually ,or entirely by automatic means .Manual methods when used as the sole source of input data are restricted to a relatibely small number of inputs .

20、Examples of manually operated devices are kryboard dials ,pushbuttons ,switches ,or thumbwheel selectors .These are located on a console near the machine .Dials are analog devices usually connected to a synchro-type reso

21、lver or potentiometer .In most cases ,push</p><p>　　In practically all cases , information is automatically supplied to the control unit and the machine too by cards ,punched tapes ,or by magnetic tape .Eigh

22、t-channel punched paper tape is the most commonly used form of data input for conventional N/C systems .The coded instructions on the tape consist of sections of punched holes called blocks .Each block represents a machi

23、ne function ,a machining operation ,or a combination of the two .The entire N/C program on a tape is made up of an accumulati</p><p>　　While the data on the tape is fed automatically ,the actual programming

24、steps are done manually .Before the coded tape may be prepared ,the programmer ,often working with a planner or a process engineer ,must select the appropriate N/C machine tool ,determine the kind of material to be machi

25、ned ,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 prog</p>

26、<p>　　The 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 stored .When the entire number has been dialed ,the equipmen

27、t becomes activated and the call is completed .</p><p>　　Silicon photo diodes ,located in the tape reader head on the control unit ,detect light as it passes</p><p>　　through the holes in the mo

28、ving tape .The light beams are converted to electrical energy ,which is amplified to further strengthen the signal .The signals are then sent to registers in the control unit ,where actuation signals are relayed to the m

29、achine tool drives .</p><p>　　Some photoelectric devices are capable of reading at rates up to 1000 characters persecond. High reading rates are necessary to maintain continuous installations motion; other-w

30、ise,dwell marks may be generated by the cutter on the part during contouring operations. The reading device must be capable of reading data blocks at a rate faster than the control system can process the data.</p>

31、<p>　　A feedback device is a safeguard used on some N/C installations to constantly compen-sate for errors between the commanded position and the actual location of the moving slides of the machine tool .An N/C mac

32、hine equipped with this kind of a direct feedback checking device has what is known as a close-loop system .Positioning control is accomplished by a sensor which ,during the actual operation, records the position of the

33、slides and relays this information back to the control unit .Signals thu</p><p>　　In an alternative system ,called an open-loop system, the is installations positioned solely by stepping motor drives in resp

34、onse to commands by a controller. The degree of work precision depends almost entirely upon the accuracy of the lead screw and the rigidity of the installations structure. With this system, there is no self- correcting a

35、ction or feedback of information to the control unit . In the event of an unexpected malfunction, the control unit continues to put out pulses of electrica</p><p>　　The original N/C used the closed-loop syst

36、em. Of the two system, closed and openloop, closed loop is more accurate and, as a consequence , is generally more expensive. Initially, open-loop systems were used almost entirely for light-duty applications because of

37、inherent power limitations previously associated with conventional electric stepping motors. Recent advances in the development of electrohydraulic stepping motors have led to increasingly heavier machine load applicatio

38、ns. </p><p><b>　　電動機和數(shù)控技術(shù)</b></p><p>　　電動機將電能轉(zhuǎn)換為機械能。 </p><p>　　簡單來說電動機就是兩塊磁鐵間的機械力作用。當兩塊磁鐵（或電磁鐵）相互靠近時，一塊將吸引或排斥另一塊。</p><p><b>　　1.結(jié)構(gòu)</b></p&g

39、t;<p>　　人們制造的各種類型的電動機都有其特定的功能。它們都由兩大部分構(gòu)成：一部分稱為定子。定子是靜止的，它不產(chǎn)生運動。另一部分稱為轉(zhuǎn)子，它安裝在軸承上，可以轉(zhuǎn)動。轉(zhuǎn)軸伸出機殼外。對于電動機而言，轉(zhuǎn)軸聯(lián)接機械負荷。</p><p><b>　　2.電動機</b></p><p>　　輸入電動機的是電能。施加到電動機端子上的電壓產(chǎn)生電流。電動機輸出機

40、械功率。機械功率通過轉(zhuǎn)軸以轉(zhuǎn)矩形式輸出。轉(zhuǎn)矩可以驅(qū)動負荷轉(zhuǎn)動，諸如一臺泵。</p><p>　　需要一定的轉(zhuǎn)矩才能驅(qū)動負荷以特定的速度轉(zhuǎn)動。若電動機輸出的轉(zhuǎn)矩足夠大，負載將轉(zhuǎn)動。若電動機輸出的轉(zhuǎn)矩太小，則不能驅(qū)動負載。在選擇電動機時所考慮的最重要的一個指標就是轉(zhuǎn)矩要求。</p><p>　　電動機驅(qū)動負載時，電動機輸出機械功率。而電動機又從電源得到等量的電功率。</p>&l

41、t;p><b>　　3.數(shù)控技術(shù)</b></p><p>　　迄今所敘述的設(shè)備的主要不利條件是這項技術(shù)的經(jīng)濟性。裝配一臺進行自動化生產(chǎn)的設(shè)備是很費錢的。因此，除非設(shè)備就會因成本過高而邊的不可行。非常需要一種既快速，在單批量生產(chǎn)中又經(jīng)濟的自動化生產(chǎn)方法。這種方法已經(jīng)有了，這就是數(shù)控技術(shù)。</p><p>　　數(shù)控（NC）是可編程自動化的一種表現(xiàn)形式，它以數(shù)字，字母

42、和其他符號來控制加工設(shè)備。這些數(shù)字、字母和符號按適當?shù)母袷骄幋a，形成用于某一工件或任務(wù)的加工程序。當任務(wù)改變了，某一工件的加工程序也隨之改變。這種改變程序的能力使得NC適用于中小批量生產(chǎn)，更新程序要比大量改變加工設(shè)備要容易的多。</p><p>　　數(shù)控原理首先用銑削加工中，然后用在車削加工、火花切削、鉆削和磨削之中，數(shù)控基數(shù)越來越多地應(yīng)用在其他的加工過程中，如成形加工（精密制造，滾壓等加工）、雕刻或激光切割。&

43、lt;/p><p>　　目前數(shù)控基數(shù)相對成熟，許多數(shù)控設(shè)備具有多種加工功能，如銑削中心可以進行垂直和水平銑削、鉆削、鉸孔、插削、成形和車削等加工過程，當然，在配有大容量的自動化刀具庫后，CNC機床的功能將更加豐富</p><p>　　數(shù)控和自動化之間很多性能是一樣的。然而，數(shù)控技術(shù)更靈活，裝配設(shè)備的花費更少，更換更快，而且停機維修時間更短。在加工外形輪廓時，數(shù)控能夠用數(shù)學(xué)方法將確定的曲線轉(zhuǎn)換成

44、成品，即節(jié)省時間，又無需樣板，還可提高加工精度。另一個優(yōu)點是能大大節(jié)省機時，也就是說不增添設(shè)備就能提高生產(chǎn)率。</p><p>　　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。</p>&l

45、t;p>　　數(shù)控設(shè)備有兩種基本形式：點位控制和連續(xù)控制（也稱為輪廓控制）。點位控制設(shè)備采用異步電動機，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)。</p><p>　　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，反饋裝置和數(shù)控設(shè)備。</p><p>　　數(shù)據(jù)輸入裝置，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)。人工方法作為輸入數(shù)據(jù)唯一

46、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，這是一個即慢又單調(diào)的過程，除了簡單加工場合或特殊情況，已很少使用。</p><p>　　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

47、數(shù)控系統(tǒng)中，八信道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)單元連續(xù)而成。帶有程序的長帶子象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續(xù)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

48、的上、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的紙帶穿孔裝置上作成的，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。</p><p>　　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)控設(shè)備，決定加工材料，計算升降

49、速度，決定所需電動機。</p><p>　　控制單元接受和存儲編碼數(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)設(shè)備得到所需運動。</p><p>　　為了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，就存儲一個，當整個數(shù)字撥好后，電話就被激活，也就完成了呼叫。</p><p>　　裝在控制單元里的紙帶閱讀機，通過其內(nèi)的硅光二極管，

50、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設(shè)備驅(qū)動裝置。</p><p>　　有些光電裝置能以高達每秒1000個字節(jié)的速度閱讀，這對保持設(shè)備連續(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。</p><p>　　反饋裝置是

51、用在一些數(shù)控設(shè)備上的安全裝置，它可連續(xù)補償控制位置與設(shè)備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)控設(shè)備有一個閉環(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。</p><p>　　在另一個稱為開環(huán)的系統(tǒng)中，設(shè)備僅由響應(yīng)控制器命令的步進電動機驅(qū)動定位，繞線部分的升降幾乎完全取決于絲杠的

52、精度和設(shè)備結(jié)構(gòu)的剛度。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，步進電動機對載荷變化不敏感，所以許多數(shù)控系統(tǒng)設(shè)計允許電動機停轉(zhuǎn)。然而，盡管有可能損壞設(shè)備機構(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。</p><p>