機械設(shè)計制造及其自動化專業(yè)英語

1、機械設(shè)計制造及其自動化專業(yè)英語Chapter One Materials and Mechanical Elements Lesson 1Introduction for Materials Designers and engineers are usually more interested in the behavior of materials under load or when in amagnetic field in why they behave as they do.Yet the better one understands the nature of materials

2、and the reasons for their physical and mechanical properties the more quickly and wisely will he/she be able to choose the proper material for agiven design.Generally,a material property is the measured magnitude of its response to astandard test performed according to astandard procedure in agiven

3、environment.In engineering materials the loads are mechanical or physical in nature and the properties are recorded in handbooks or,for new materials,are made available by the supplier.Frequently such information is tabulated for room-temperature conditions only,so when the actual service conditions

4、 are at subfreezing or elevated temperatures,more information is needed.第一章材料和機械零件第一課材料介紹設(shè)計者和工程師們通常都會對在加載狀態(tài)下或處于磁場中的材料的性能更感興趣，而不關(guān)心它們?yōu)槭裁淳哂羞@個性能。然而，一個人若能更好地理解這些材料的性質(zhì)和它們的物理和機械的性能原因，了解得越清楚，他/她就能更快速和準確地選擇合適的材料。通常，材料性能是在給定的環(huán)境條件下按照規(guī)定的方法進行的標準試驗所獲得的測定值。事實上，工程材料中的加載實質(zhì)上是機械的或物理的加載，并且性能是記錄在手冊上的，或者，對于新材料來說，是應(yīng)由供應(yīng)商來提

5、供性能手冊的。一般來說類似的信息僅僅是在室溫條件下被列表顯示的，因此，當實際的操作條件是在冰點以下或在高溫條件下，則會需要更多的信息。Lesson 4Gears Helical gears have certain advantages；for example,when connecting parallel shafts they have ahigher loadcarrying capacity than spur gears with the same tooth numbers and cut with the same cutter.Because of the overlappi

6、ng action of the teeth,they are smoother in action and can operate at higher pitch-line velocities than spur gears.The pitch-line velocity is the velocity of the pitch circle.Since the teeth are inclined to the axis of rotation,helical gears create an axial thrust.If used singly,this thrust must be

7、absorbed in the shaft bearings.The thrust problem can be overcome by cutting two sets of opposed helical teeth on the same blank.Depending on the method of manufacture,the gear may be of the continuous-tooth herringbone variety or adouble-helical gear with aspace between the two halves to permit the

8、 cutting tool to run out.Double-helical gears are well suited for the efficient transmission of power at high speeds.第四課齒輪斜齒輪有某些優(yōu)點；例如，在具有相同齒數(shù)且用同樣的刀具來加工的情況下，連接平行軸的斜齒輪的承載能力要比直齒輪更高一些。由于輪齒的重疊作用，斜齒輪在運動中比直齒輪更平穩(wěn)，并且能夠以更高的節(jié)線速度來運行。節(jié)線速度就是節(jié)圓的線速度。由于輪齒向軸線的旋轉(zhuǎn)方向傾斜，故斜齒輪產(chǎn)生了一個軸向推力。如果是單個的齒輪，這個推力必定會被軸向軸承吸收。通過在同一個坯件上切削兩組

9、相對的斜齒輪，能夠克服推力的問題。根據(jù)不同的制造方法，齒輪可以是連續(xù)的人字形齒輪，或者是在兩列斜齒之間留一間隙的雙斜齒形齒輪，以便切削刀具通過。雙斜齒形齒輪更適合以高速度進行高效地傳送。Lesson 6Dimensioning The design of amachine includes many factors other than those of determining the loads and stresses and selecting the proper materials.Before construction or manufacture can begin,it is

10、necessary to have complete assembly and detail drawings to convey all necessary information to the shop men.The designer frequently is called upon to check the drawings before they are sent to the shop.Much experience and familiarity with manufacturing processes are needed before one can become conv

11、ersant with all phases of production drawings.Drawings should be carefully checked to see that the dimensioning is done in amanner that will be most convenient and understandable to the production departments.It is obvious that adrawing should be made in such away that it has one and only one interp

12、retation.In particular,shop personnel should not be required to make trigonometric or other involved calculations before the production machines can be set up.第六課標注要設(shè)計一個機床除了要考慮那些已確定的負載和應(yīng)力并且選擇合適的材料以外，還包括很多其他的因素。在構(gòu)造和加工開始以前，必須要把完整的裝配圖和詳細的零件圖的全部有用的信息傳達給工人。設(shè)計者經(jīng)常要在圖紙未被送到車間以前檢查核對圖紙。每個人在熟悉生產(chǎn)圖紙的各個階段之前都必須具有豐富

13、的經(jīng)驗并精通加工工藝。應(yīng)該仔細檢查圖紙，為生產(chǎn)部門作標注時須用一種最合適和最易理解的方式進行，很明顯，一張圖紙應(yīng)該是有且只有一種解釋的。尤其是不能要求車間工人先進行三角或其他復(fù)雜的計算后才能去調(diào)整機床。Chapter Two Machine Tool,Cutting Tool,Jig and Fixture Lesson 1Engine Lathe(Center Lathe)An engine lathe is shown diagrammatically in Fig.2.1a：it consists of ahorizontal bed supporting the headstock,t

14、he tailstock,and the carriage.All machine tools must have ameans of supporting or holding the workpiece.In Fig.2.1 the workpiece is gripped at one end by achuck mounted on the end of the main spindle of the machine and is supported at the other end by acenter mounted in the tailstock.The tailstock c

15、an be clamped at various positions along the bed to accommodate workpieces of various lengths.Short workpieces need only be gripped by the chuck.Primary motion,the rotation of the workpiece(motion C),is provided by the movement of aseries of gears driving the main spindle,the gears being driven by a

16、n electric motor mounted at the rear of the machine.The main spindle and the gears are all mounted in the headstock.Levers on the front of the headstock allow various rotational speeds to be sele cted.第二章機床，切削刀具，鉆模和夾具第一課車床(普通車床)一個普通車床的結(jié)構(gòu)如圖2.1a所示：它由支撐著主軸箱的臥式床身、尾座以及拖板三部分組成。所有的機床必須都要有一種支撐或夾緊工件的方式。在圖2.1

17、中，工件通過安裝在機床主軸末端的卡盤在一端被夾緊，并且由裝配在尾架上的頂尖在另一端被支撐。根據(jù)被加工工件長度的不同，尾架沿著床身被裝夾在不同的位置。短的工件僅需要由卡盤夾緊。主運動，即工件的旋轉(zhuǎn)運動(也就是C點的運動)，是由輪系驅(qū)動主軸實現(xiàn)工件旋轉(zhuǎn)的，齒輪通過裝夾在車床尾部的電機來帶動它旋轉(zhuǎn)。主軸和齒輪都裝夾在主軸箱中。主軸箱前部的手柄能夠根據(jù)實際需要選擇不同的旋轉(zhuǎn)速度。Lesson 2Horizontal Milling Machine(Horizontal Miller)There are two main types of milling machines：horizontal and

18、vertical.These words again refer to the orientation of the main spindle.In the horizontal-milling machine shown in Fig.2.5 the milling cutter is mounted on ahorizontal arbor driven by the main spindle.The tools are therefore rotated(motion C)and the work fed continuously(motions Xor Y).The simplest

19、operation,slab milling,is used to generate ahorizontal surface on the workpiece,as shown in Fig.2.5.The figure shows the conventional slab-milling operation；if the workpiece had been fed in the opposite direction,it would tend to climb onto the work surface,and this type of slab milling is calledcli

20、mbmilling.Some evidence suggests that the forces and power consumption are less in climb milling than in conventional milling.However,high rigidity of the machine tool and work and tool-holding devices is required for this operation.第二課臥式銑床銑床有兩種主要類型：臥式和立式。這兩種銑床再一次提到了主軸的方向。如圖2.5所示的臥式銑床，銑刀被裝在水平方向的刀桿上，

21、這個刀桿由主軸來驅(qū)動。刀具因此是旋轉(zhuǎn)的(C運動)，并且工件是連續(xù)地進給(X、Y方向的運動)。平面銑的加工方式最簡單，用來加工工件的水平表面，如圖2.5所示。該圖給出了平面逆銑加工；如果工件以相反的方向進給，刀具就像在工件表面上爬行一樣，這種類型的平面銑也叫順銑。一些證據(jù)表明，順銑中的力和功率的消耗比逆銑中的少。然而，這就要求機床、工件和夾具要具有更高的硬度。Lesson 3Shaping Machine(shaper)The shaper is asmall machine on which the primary motion is linear(Fig.2.17).The single-p

22、oint tool is gripped in atoolhead mounted on the end of aram.The ram is made to move backward and forward(X motion)either by amechanical drive system or ahydraulic piston and cylinder.The cutting stroke is the forward stroke,and with either mechanical or hydraulic shapers the forward ram speed is sl

23、ower than the speed on the return stroke,causing the production time to be reduced as much as possible.A quick-return mechanism often used in mechanical shapers is shown in Fig.2.18.In all shapers the length of the stroke can be adjusted to suit the particular workpiece being machined.The feed is ap

24、plied to the workpiece in increments at the end of the return stroke of the ram by arachet-and-pawl mechanism driving the lead screw in the crossrail.Shapers are most commonly used to machine flat surfaces on small components and are only suitable for low-baton quantities.For the machining of ahoriz

25、ontal surface(Fig.2.17),the workpiece is fed horizontally(Ymotion)；for vertical surfaces,the workpiece is fed vertically(Zmotion).第三課牛頭刨床(成型機)牛頭刨床是一個小型機床，它的主運動是直線運動(圖2.17)。它的單刃刨刀被夾緊在刀架上，裝卡在滑枕的末端。機械的驅(qū)動或者液壓的活塞缸使得滑枕在X軸方向上進行前后移動。它向前供進的行程即為切削行程，并伴隨著機械或者液壓的成型機，滑枕向前的速度要比它回程的速度慢得多，這就會使加工時間盡可能的快，以提高工作效率。通常，用

26、在機械牛頭刨床的快回機械如圖2.18所示。在所有的牛頭刨床中，回程的長度均可根據(jù)需要做出相應(yīng)的調(diào)整以適應(yīng)不同的待加工工件。在滑枕返程的末端，進給被應(yīng)用于工件的增量上，通過橫導(dǎo)軌內(nèi)的絲桿來驅(qū)動棘輪棘爪機構(gòu)。牛頭刨床大多用于加工普通的小零件的平面表面，并且僅適合小批量加工生產(chǎn)。對于一個機件的水平表面的加工(圖2.17)，工件沿水平方向進行進給(沿Y軸方向運動)；對于垂直表面的加工，工件以垂直的方向進給(Z軸方向)。Lesson 4Automatic Machines Afinal class of automatic lathe is the multispindle automatic.Thes

27、e lathes are basically flexible,rotary-transfer machines where each spindle holding acollet or chuck is indexed around the various tooling positions so that during each indexing cycle acompleted component is produced.Drum cams instead of disk cams are used in these machines.Another class of machine

28、tool that can be mechanized is the internal or external cylindrical grinder.When fitted with mechanisms for loading workpieces automatically and with automatic wheel-dressing devices,these machines can continually produce finished components.The workpieces are often stacked in amagazine,and the oper

29、ator simply ensures that the magazine is replenished with workpieces at suitable intervals.Because the components are small and the machining forces light,magnetic chucks are often employed to facilitate automatic work holding.第四課自動機床最后一組的自動車床是多主軸自動機床。這類機床基本上是靈活的旋轉(zhuǎn)自動機，它的每一根軸上都有一個夾頭或卡盤，可以繞不同位置的刀具轉(zhuǎn)位，因

30、此，每轉(zhuǎn)位一次就加工出一個零件。在這類機床中，凸輪軸取代了盤形凸輪被使用。另一類可以實現(xiàn)機械化的機床是內(nèi)部的或外部的外圓磨床。當裝上帶有自動砂輪修整裝置的自動裝載工件的機械時，這些機床能夠不斷地生產(chǎn)成品組件。工件堆放在自動儲存送料裝置上，而操作者只需在適當?shù)臅r間內(nèi)將工件補放到送料裝置上。因為這些組件很小，并且加工力道很輕，磁性夾頭通常采用自動方式，以方便運行。Lesson 5Jigs and Fixtures When several identical workpieces are to be produced the need to mark out each part is elimin

31、ated by the use of jigs and fixtures,but if acasting or forging is involved,a trial workpiece is marked out,to ensure that the workpiece can be produced from it,and to ensure that ribs,cores,etc.have not become misplaced.Jigs and fixtures are alike in that they both incorporate devices to ensure tha

32、t the workpiece is correctly located and clamped,but they differ in that jigs incorporate means of tool guiding during the actual cutting operation,and fixtures do not.In practice,the only cutting tools that can be guided while actually cutting are drills,reamers,and similar cutters；and so jigs are

33、associated with drilling operations,and fixtures with all other operations.Fixtures may incorporate means of setting the cutting tools relative to the location system.第五課鉆模和夾具當若干相同的工件需要加工時，通過使用鉆模和夾具可不必對每個工件都進行劃線。但如果加工的是鑄件或鍛件，則仍需對試件進行劃線，以確保加工出合格的樣件，而不致造成加強筋、內(nèi)孔等位置偏移。鉆模和夾具類似，都是確保工件正確定位和夾緊的裝置，但也有不同之處，鉆模

34、具有在實際加工過程中仍能導(dǎo)引刀具的元件，而夾具則沒有。實際上，在切削過程中只有對鉆頭、鉸刀以及類似的刀具才能進行導(dǎo)引，所以鉆模通常與鉆削加工相關(guān)聯(lián)，而夾具是與其他所有加工方法相關(guān)聯(lián)的。夾具可納入設(shè)置相對定位系統(tǒng)的調(diào)刀手段。Chapter Three Conventional and Nonconventional Machining Lesson 1Term and Definitions All metal-cutting operations can be likened to the process shown in Fig.3.1,where the tool is wedge-sha

35、ped,has astraight cutting edge,and is constrained to move relative to the workpiece in such away that alayer of metal is removed in the form of achip.Fig.3.1b depicts the general case of cutting known as oblique cutting.A special case of cutting,where the cutting edge of the tool is arranged to be p

36、erpendicular to the direction of relative work-tool motion(Fig.3.1a),is known as orthogonal cutting.Since orthogonal cutting represents atwo-dimensional rather than athree-dimensional problem,it lends itself to research investigations where it is desirable to eliminate as many of the independent var

37、iables as possible.The relatively simple arrangement of orthogonal cutting is therefore widely used in theoretical and experimental work.The tool flank plays no part in the process of chip removal；however,the angle between the flank and the new workpiece surface can significantly affect the rate at

38、which the cutting tool wears and is defined as the clearance angle or,more precisely,the working normal clearance.Thus from Fig.3.2 the sum of the rake,clearance,and wedge angles is equal to 90 deg,where the wedge angle is the included angle between the face and the flank.第三章常規(guī)和非常規(guī)加工第一課術(shù)語和定義所有的金屬切削加

39、工過程都可以用圖3.1所示的過程來表示，即刀具是楔形的且具有直線切削刃，并且刀具相對于工件運動，每運動一次便會切下一層切屑。圖3.1b描述了斜刃切削作為切削刀具的一般情況。切削中有一個特例，即刀具的切削刃相對于刀具的運動方向是垂直的(圖3.1a)，這也叫直角切削。由于直角切削反映的是二維而不是三維的結(jié)構(gòu)問題，這樣相對簡單的直角切削也因此被廣泛地用于理論和實驗的工作中。刀具后刀面在切屑被去除的過程中不起作用；然而，后刀面與新加工工件表面所夾的夾角嚴重地增加了刀具的磨損率，這個角被定義為后角，或者，更確切地說，稱為工作法向后角。然而從圖3.2可以看出，前角，后角和楔形角三者的和正好等于90，這個楔

40、形角包含了前刀面和后刀面所夾的夾角。Lesson 2Production Turning Operations The era of modern machine tools is relatively recent,dating back to the Industrial Revolution in England.The first screw-cutting lathe was invented by Maudsley in 1798.The modern engine lathe takes its name from its gear-driven headstock that t

41、ypically provides 16 spindle speeds.Although an engine lathe can bring one to four tools mounted in its one toolpost to bear on aworkpiece,it can provide only asingle feed motion at one time.A typical turned part frequently requires several operations,each of which needs adifferent tool and feed mot

42、ion.The replacement and resetting of the tooling and handling of the work in and out of the machine adds asignificant cost to the finished part.Moreover,the cost per piece may be three to six times the cost of using amore specialized machine tool.When anumber of identical parts are needed,positionin

43、g of the tools for each operation not only involves time but may also result in workpieces that will not pass inspection.Thus,an engine lathe is suitable for low production only.第二課車削加工現(xiàn)代車床的年代并不遙遠，可追溯到英國工業(yè)革命時期。世界上第一臺螺紋切削車床是由莫茲利于1798年發(fā)明的?，F(xiàn)代主軸車床得名于它的齒輪驅(qū)動主軸箱運動且具有典型的16種主軸速度。雖然一個車床的一個刀架在加工一個工件時可攜帶一至四把刀具，

44、但在一段時間內(nèi)它只能實現(xiàn)一次進給運動。一個典型的車削零件需反復(fù)加工多次才能完成，每一次加工都需要一把不同的刀具和進給運動。換刀和重新調(diào)刀以及工件的裝卸都給工件增加了巨大的成本。此外，每一步所花費的成本可能會是使用一個更加專業(yè)化機床成本的三至六倍。當需要加工一定數(shù)目的相同零件時，對每一次加工的對刀和調(diào)刀來說不僅僅浪費時間而且還會導(dǎo)致很多工件不合格。因此，車床只適合于小批量生產(chǎn)。Lesson 4Electrical-Discharge Machining Electrical-discharge machining(EDM),or spark machining,as it is also cal

45、led,removes material with repetitive spark discharges from apulsating DC power supply,with adielectric flowing between the workpiece and the tool.The principle of the EDM process is illustrated by the simplified diagram in Fig.3.17.The tool is mounted on the chuck attached to the machine spindle who

46、se motion is controlled by aservo-controlled feed drive.The workpiece is placed in atank filled with adielectric fluid；a depth of at least 50mm over the work surface is maintained to eliminate the risk of fire.The tool and workpiece are connected to apulsating DC power supply.Dielectric fluid is cir

47、culated under pressure by apump,usually through ahole(or holes)in the tool electrode.A spark gap of about 0.025 to 0.05 mm is maintained by the servomotor.第四課放電加工放電加工(EDM)，也叫電火花加工，顧名思義，它是通過從脈沖直流電源中反復(fù)的電火花釋放來去除工件的材料的，且在工件與刀具之間有絕緣液體介質(zhì)的存在。放電加工過程的原理如圖3.17所示的簡圖。裝配在卡盤上的刀具，連接到機床主軸上，且機床主軸的運動是由伺服控制進給驅(qū)動的。工件被放置

48、在一個充滿了絕緣介質(zhì)的槽箱中；要確保絕緣介質(zhì)沒過工件表面至少50毫米，以消除火災(zāi)隱患。將刀具和工件連接到脈沖直流電源的兩端。絕緣介質(zhì)是在一個泵的壓力下開始循環(huán)的，通常經(jīng)由刀具電極中的一個孔(或幾個孔)中開始?；鸹ǖ拈g隙大約是0.025至0.05毫米，是在伺服電機工作的狀態(tài)下保證的。Chapter Four Manufacturing Lesson 4Assembly After individual parts have been manufactured,they are assembled into aproduct.Assembly is an important phase of th

49、e overall manufacturing operation and requires consideration of the ease,speed,and cost of putting parts together.Many products are also designed so that they can be taken apart for maintenance and servicing.There are several methods of assembly,each with its own characteristics and requiring differ

50、ent operations.The use of abolt and nut,for example,requires preparation of holes that must match in location and size.Hole generation requires operations such as drilling or punching,which take additional time,require separate operations,and produce scrap.Furthermore,the presence of holes could red

51、uce the useful life of components because of stress concentration,leading to fatigue failure of the part.On the other hand,products assembled with bolts and nuts can be taken apart and reassembled with relative ease.Parts may be assembl ed by hand or by automatic equipment.The choice depends on fact

52、ors such as the complexity of the product and the number of parts to be assembled,the protection required to prevent damage or scratching of finished surfaces of the parts,and the relative costs of labor and machinery required for automated assembly.Variations in the dimensions of parts may be toler

53、ated in hand assembly since the operator can make minor adjustments.In automated assembly,however,parts must have consistently uniform dimensions.Otherwise,their movement through the assembly equipment can be impeded and parts not assembled properly.第四章制造業(yè)第四課裝配在單個零件被加工完成以后，就要被裝配成產(chǎn)品。裝配在整個的制造加工過程中至關(guān)重要

54、，需要考慮將零件裝配到一起的難易程度、速度以及成本。很多產(chǎn)品也會為方便日后的維修和保養(yǎng)被設(shè)計成易于拆卸的形式。裝配有很多種方法，每一種方法都有其自己的特點且需要不同的操作方式。例如，螺栓和螺母的使用，要求孔與孔之間必須在位置和尺寸上相互匹配?？椎纳尚枰喾N加工形式，像鉆孔或沖孔等，這會花費額外的時間且需要單獨操作，并很容易產(chǎn)生廢料。再者，由于應(yīng)力集中，孔的存在可能會減少零件的使用壽命，從而導(dǎo)致零件的疲勞失效。另一方面，用螺栓螺母裝配起來的產(chǎn)品拆卸和重組都比較容易。零件的裝配方法可采用手工加工法或自動化設(shè)備加工法兩種。選擇哪種裝配方法取決于許多因素，如產(chǎn)品的復(fù)雜程度及待裝件的數(shù)量、需防止零件受

55、損或防止精加工表面被劃傷的情況，勞動力和自動化裝配所需機械設(shè)備的相對成本等。零件尺寸的變化在手工裝配中是可以允許的，因為工人可以做一些微小的調(diào)整。然而在自動裝配線中，零件的尺寸就必須要完全一致。否則，裝配設(shè)備就會阻礙這些零件的運動，并且零件也不能被正確的裝配。Chapter Five Control and Computer Technology in Manufacturing Lesson 1Control System Closed-loop control Closed-loop control system requires negative feedback be create a

56、n error and subsequent control action.The plant responds with an output which is returned via negative feedback,and the process continues in an endless loop.The following are the main benefits of closed-loop control：1.Increases accuracy.2.Reduces effects of noise.3.Increases plant bandwidth.4.Can be applied with minimal input/output relationships of the plant under control.There are two disadvantages in terms of practical implementation of this control system：1.High cost.2.Requires qualified personnel to ensure stability.The accur