機械工程專業(yè)畢業(yè)設計外文翻譯

1、英文原文名Lthes中文譯名 車床中文譯文:車床車床主要是為了進行車外圓、車端面和鏜孔等項工作而設計的機床。車削很少在其他種類的機床上進行，而且任何一種其他機床都不能像車床那樣方便地進行車削加工。由于車床還可以用來鉆孔和鉸孔，車床的多功能性可以使工件在一次安裝中完成幾種加工。因此， 在生產(chǎn)中使用的各種車床比任何其他種類的機床都多。車床的基本部件有：床身、 主軸箱組件、尾座組件、溜板組件、絲杠和光杠。床身是車床的基礎件。它能常是由經(jīng)過充分正火或時效處理的灰鑄鐵或者球墨鐵制成。 它是一個堅固的剛性框架，所有其他基本部件都安裝在床身上。通常在床身上有內(nèi)外兩組平行的導軌。有些制造廠對全部四條導軌都采用

2、導軌尖朝上的三角形導軌（即山形導軌），而有的制造廠則在一組中或者兩組中都采用一個三角形導軌和一個矩形導軌。導軌要經(jīng)過精密加工以保證其直線度精度。為了抵抗磨損和擦傷，大多數(shù)現(xiàn)代機床的導軌是經(jīng)過表面淬硬的，但是在操作時還應該小心，以避免損傷導軌。導軌上的任何誤差，常常意味著整個機床的精度遭到破壞。主軸箱安裝在內(nèi)側(cè)導軌的固定位置上，一般在床身的左端。它提供動力，并可使工件在各種速度下回轉(zhuǎn)。它基本上由一個安裝在精密軸承中的空心主軸和一系列變速齒輪（類似于卡車變速箱）所組成。通過變速齒輪，主軸可以在許多種轉(zhuǎn)速下旋轉(zhuǎn)。大多數(shù)車床有812 種轉(zhuǎn)速，一般按等比級數(shù)排列。而且在現(xiàn)代機床上只需扳動24 個手柄，

3、就能得到全部轉(zhuǎn)速。一種正在不斷增長的趨勢是通過電氣的或者機械的裝置進行無級變速。由于機床的精度在很大程度上取決于主軸，因此， 主軸的結構尺寸較大，通常安裝在預緊后的重型圓錐滾子軸承或球軸承中。主軸中有一個貫穿全長的通孔， 長棒料可以通過該孔送料。主軸孔的大小是車床的一個重要尺寸，因此當工件必須通過主軸孔供料時，它確定了能夠加工的棒料毛坯的最大尺寸。數(shù)字控制的機器比人工操縱的機器精度更高、生產(chǎn)出零件的一致性更好、生產(chǎn)速度更快、而且長期的工藝裝備成本更低。數(shù)控技術的發(fā)展導致了制造工藝中其他幾項新發(fā)明的產(chǎn)生：電火花加工技術、激光切割、電子束焊接數(shù)字控制還使得機床比它們采用有人工操的前輩們的用途更為廣

4、泛。一臺數(shù)控機床可以自動生產(chǎn)很多類的零件，每一個零件都可以有不同的和復雜的加工過程。 數(shù)控可以使生產(chǎn)廠家承擔那些對于采用人工控制的機床和工藝來說，在經(jīng)濟上是不劃算的產(chǎn)品生產(chǎn)任務。同許多先進技術一樣，數(shù)控誕生于麻省理工學院的實驗室中。數(shù)控這個概念是 50 年代初在美國空軍的資助下提出來的。在其最初的價段，數(shù)控機床可以經(jīng)濟和有效地進行直線切割。然而， 曲線軌跡成為機床加工的一個問題，在編程時應該采用一系列的水平與豎直的臺階來生成曲線。構成臺階的每一個線段越短，曲線就越光滑。臺階中的每一個線段都必須經(jīng)過計算。在這個問題促使下，于1959年誕生了自動編程工具（APT）語言。這是一 個專門適用于數(shù)控的編

5、程語言，使用類似于英語的語句來定義零件的幾何形狀，描述切削刀具的形狀和規(guī)定必要的運動。APT 語言的研究和發(fā)展是在數(shù)控技術進一步發(fā)展過程中的一大進步。最初的數(shù)控系統(tǒng)下今天應用的數(shù)控系統(tǒng)是有很大差別的。在那時的機床中，只有硬線邏輯電路。指令程序?qū)懺诖┛准垘希ㄋ髞肀凰芰蠋〈?采用帶閱讀機將寫在紙帶或磁帶上的指令給機器翻譯出來。所有這些共同構成了機床數(shù)字控制方面的巨大進步。然而， 在數(shù)控發(fā)展的這個階段中還存在著許多問題。一個主要問題是穿孔紙帶的易損壞性。在機械加工過程中，載有編程指令信息的紙帶斷裂和被撕壞是常見的事情。在機床上每加工一個零件，都需要將載有編程指令的紙帶放入閱讀機中重新運行

6、一次。因此， 這個問題變得很嚴重。如果需要制造100 個某種零件，則應該將紙帶分別通過閱讀機100次。易損壞的紙帶顯然不能承受嚴配的車間環(huán)境和這種重復使用。這就導致了一種專門的塑料磁帶的研制。在紙帶上通過采用一系列的小孔來載有編程指令，而在塑料帶上通過采用一系列的磁點瞇載有編程指令。塑料帶的強度比紙帶的強度要高很多，這就可以解決常見的撕壞和斷裂問題。然而， 它仍然存在著兩個問題。其中最重要的一個問題是，對輸入到帶中指令進行修改是非常困難的，或者是根本不可能的。即使對指令程序進行最微小的調(diào)整，也必須中斷加工，制作一條新帶。 而且?guī)ㄟ^閱讀機的次數(shù)還必須與需要加工的零件的個數(shù)相同。幸運的是， 計算

7、機技術的實際應用很快解決了數(shù)控技術中與穿孔紙帶和塑料帶有關的問題。在形成了直接數(shù)字控制（DNC）這個概念之后，可以不再采用紙帶或塑料帶作為編程指令的載體，這樣就解決了與之有關的問題。在直接數(shù)字控制中，幾臺機床通過數(shù)據(jù)傳輸線路聯(lián)接到一臺主計算機上。操縱這些機床所需要的程序都存儲在這臺主計算機中。當需要時，通過數(shù)據(jù)傳輸線路提供給每臺機床。直接數(shù)字控制是在穿孔紙帶和塑料帶基礎上的一大進步。然而，它敢有著同其他信賴于主計算機技術一樣的局限性。當主計算機出現(xiàn)故障時，由其控制的所有機床都將停止工作。這個問題促使了計算機數(shù)字控制技術的產(chǎn)生。微處理器的發(fā)展為可編程邏輯控制器和微型計算機的發(fā)展做好了準備。這兩種

8、技術為計算機數(shù)控（CNC）的發(fā)打下了基礎。采用CNC技術后，每臺機床上都有一個可編程邏輯控制器或者微機對其進行數(shù)字控制。這可以使得程序被輸入和存儲在每臺機床內(nèi)部。它還可以在機床以外編制程序，并將其下載到每臺機床中。計算機數(shù)控解決了主計算機發(fā)生故障所帶來的問題，但是它產(chǎn)生了另一個被稱為數(shù)據(jù)管理的問題。同一個程序可能要分別裝入十個相互之間沒有通訊聯(lián)系的微機中。 這個問題目前正在解決之中，它是通過采用局部區(qū)域網(wǎng)絡將各個微機聯(lián)接起來，以得于更好地進行數(shù)據(jù)管理。3.車削加工普通車床作為最早的金屬切削機床的一種，目前仍然有許多有用的和為人要的特性和為人們所需的特性。現(xiàn)在， 這些機床主要用在規(guī)模較小的工廠中

9、，進行小批量的生產(chǎn)，而不是進行大批量的和產(chǎn)。在現(xiàn)代的生產(chǎn)車間中，普通車床已經(jīng)被種類繁多的自動車床所取代，諸如自動仿形車床，六角車床和自動螺絲車床?，F(xiàn)在， 設計人員已經(jīng)熟知先利用單刃刀具去除大量的金屬余量，然后利用成型刀具獲得表面光潔度和精度這種加工方法的優(yōu)點。 這種加工方法的生產(chǎn)速度與現(xiàn)在工廠中使用的最快的加工設備的速度相等。普通車床的加偏差主要信賴于操作者的技術熟練程度。設計工程師應該認真地確定由熟練工人在普通車床上加工的試驗件的公差。在把試驗伯重新設計為生產(chǎn)零件時，應該選用經(jīng)濟的公差。六角車床對生產(chǎn)加工設備來說，目前比過去更注重評價其是否具有精確的和快速的重復加工能力。應用這個標準來評價具

10、體的加工方法，六角車床可以獲得較高的質(zhì)量評定。在為小批量的零件（100200 件）設計加工方法時，采用六角車床是最經(jīng)濟的。 為了在六角車床上獲得盡可能小的公差值，設計人員應該盡量將加工工序的數(shù)目減至最少。自動螺絲車床自動螺絲車床通被分為以下幾種類型：單軸自動、多軸自動和自動夾緊車床。自動螺絲車床最初是被用來對螺釘和類似的帶有螺紋的零件進行自動化和快速加工的。但是， 這種車床的用途早就超過了這個狹窄的范圍?，F(xiàn)在， 它在許多種類的精密零件的大批量生產(chǎn)中起著重要的作用。工件的數(shù)量對采用自動螺絲車床所加工的零件的經(jīng)濟性有較大的影響。如果工件的數(shù)量少于1000 件，在六角車床上進行加工比在自動螺絲車床上

11、加工要經(jīng)濟得多。如果計算出最小經(jīng)濟批量，并且針對工件批量正確地選擇機床，就會降低零件的加工成本。自動仿形車床因為零件的表面粗糙度在很大程度上取決于工件材料、刀具、 進給量和切削速度，采用自動仿形車床加工所得到的最小公差一定是最經(jīng)濟的公差。在某些情況下，在連續(xù)生產(chǎn)過程中，只進行一次切削加工時的公差可以達到0.05mm。對于某些零件，槽寬的公差可以達到0.125mm。鏈孔和休用單刃刀具進行精加工時，公差可達到 0.0125mm。在希望獲得最大主量的大批量生產(chǎn)中， 進行直徑和長度的車削時的最小公差值為 0.125mm是經(jīng)濟的。英文原文：LathesLathes are machine tools d

12、esigned primarily to do turning, facing and boring, Ver y little turning is done on other types of machine tools, and none can do it with equal f acility. Because lathes also can do drilling and reaming, their versatility permits sever al operations to be done with a single setup of the work piece.

13、Consequently, more lat hes of various types are used in manufacturing than any other machine tool.The essential components of a lathe are the bed, headstock assembly, tailstock as sembly, and the leads crew and feed rod.The bed is the backbone of a lathe. It usually is made of well normalized or age

14、d gray or nodular cast iron and provides s heavy, rigid frame on which all the other basi c components are mounted. Two sets of parallel, longitudinal ways, inner and outer, ar e contained on the bed, usually on the upper side. Some makers use an inverted V-sha pe for all four ways, whereas others u

15、tilize one inverted V and one flat way in one or both sets, They are precision-machined to assure accuracy of alignment. On most mod ern lathes the way are surface-hardened to resist wear and abrasion, but precaution sh ould be taken in operating a lathe to assure that the ways are not damaged. Any

16、inaccu racy in them usually means that the accuracy of the entire lathe is destroyed.The headstock is mounted in a foxed position on the inner ways, usually at the le ft end of the bed. It provides a powered means of rotating the word at various speeds . Essentially, it consists of a hollow spindle,

17、 mounted in accurate bearings, and a set of t ransmission gears-similar to a truck transmission through which the spindle can be r otated at a number of speeds. Most lathes provide from 8 to 18 speeds, usually in a ge ometric ratio, and on modern lathes all the speeds can be obtained merely by movin

18、g f rom two to four levers. An increasing trend is to provide a continuously variable spee d range through electrical or mechanical drives.Because the accuracy of a lathe is greatly dependent on the spindle, it is of heavy construction and mounted in heavy bearings, usually preloaded tapered roller

19、or ball t ypes. The spindle has a hole extending through its length, through which long bar stoc k can be fed. The size of maximum size of bar stock that can be machined when the m aterial must be fed through spindle.The tailsticd assembly consists, essentially, of three parts. A lower casting fits

20、on the inner ways of the bed and can slide longitudinally thereon, with a means for clamp ing the entire assembly in any desired location, An upper casting fits on the lower one and can be moved transversely upon it, on some type of keyed ways, to permit alignin g the assembly is the tailstock quill

21、. This is a hollow steel cylinder, usually about 51 t o 76mm(2to 3 inches) in diameter, that can be moved several inches longitudinally in and out of the upper casting by means of a hand wheel and screw.The size of a lathe is designated by two dimensions. The first is known as the swi ng. This is th

22、e maximum diameter of work that can be rotated on a lathe. It is approxi mately twice the distance between the line connecting the lathe centers and the nearest point on the ways, The second size dimension is the maximum distance between cent ers. The swing thus indicates the maximum work piece diam

23、eter that can be turned in the lathe, while the distance between centers indicates the maximum length of work pi ece that can be mounted between centers.Engine lathes are the type most frequently used in manufacturing. They are heav y-duty machine tools with all the components described previously a

24、nd have power dr ive for all tool movements except on the compound rest. They commonly range in siz e from 305 to 610 mm(12 to 24 inches)swing and from 610 to 1219 mm(24 to 48 inch es) center distances, but swings up to 1270 mm(50 inches) and center distances up to 3658mm(12 feet) are not uncommon.

25、Most have chip pans and a built-in coolant circu lating system. Smaller engine lathes-with swings usually not over 330 mm (13 inches )-also are available in bench type, designed for the bed to be mounted on a bench on a bench or cabinet.Although engine lathes are versatile and very useful, because o

26、f the time require d for changing and setting tools and for making measurements on the work piece, thy are not suitable for quantity production. Often the actual chip-production tine is less th an 30% of the total cycle time. In addition, a skilled machinist is required for all the o perations, and

27、such persons are costly and often in short supply. However, much of th e operator s time is consumed by simple, repetitious adjustments and in watching chi ps being made. Consequently, to reduce or eliminate the amount of skilled labor that i s required, turret lathes, screw machines, and other type

28、s of semiautomatic and autom atic lathes have been highly developed and are widely used in manufacturing. 2 Nume rical ControlOne of the most fundamental concepts in the area of advanced manufacturing tec hnologies is numerical control (NC). Prior to the advent of NC, all machine tools ere manually

29、operated and controlled. Among the many limitations associated with manu al control machine tools, perhaps none is more prominent than the limitation of operat or skills. With manual control, the quality of the product is directly related to and limit ed to the skills of the operator. Numerical cont

30、rol represents the first major step away from human control of machine tools.Numerical control means the control of machine tools and other manufacturing s ystems through the use of prerecorded, written symbolic instructions. Rather than ope rating a machine tool, an NC technician writes a program t

31、hat issues operational instru ctions to the machine tool. For a machine tool to be numerically controlled, it must be interfaced with a device for accepting and decoding the programmed instructions, kno wn as a reader.Numerical control was developed to overcome the limitation of human operators, and

32、 it has done so. Numerical control machines are more accurate than manually oper ated machines, they can produce parts more uniformly, they are faster, and the long-ru n tooling costs are lower. The development of NC led to the development of several ot her innovations in manufacturing technology:El

33、ectrical discharge machining,Laser cutting,Electron beam welding.Numerical control has also made machine tools more versatile than their manuall y operated predecessors. An NC machine tool can automatically produce a wide of par ts, each involving an assortment of widely varied and complex machining

34、 processes. Numerical control has allowed manufacturers to undertake the production of products that would not have been feasible from an economic perspective using manually contr olled machine tolls and processes.Like so many advanced technologies, NC was born in the laboratories of the Mas sachuse

35、tts Institute of Technology. The concept of NC was developed in the early 195 0s with funding provided by the U.S. Air Force. In its earliest stages, NC machines we re able to made straight cuts efficiently and effectively.However, curved paths were a problem because the machine tool had to be progr

36、 ammed to undertake a series of horizontal and vertical steps to produce a curve. The s horter the straight lines making up the steps, the smoother is the curve, Each line seg ment in the steps had to be calculated.This problem led to the development in 1959 of the Automatically Programmed Tools (AP

37、T) language. This is a special programming language for NC that uses state ments similar to English language to define the part geometry, describe the cutting too l configuration, and specify the necessary motions. The development of the APT lang uage was a major step forward in the fur ther develop

38、ment from those used today. The machines had hardwired logic circuits. The instructional programs were written on pu nched paper, which was later to be replaced by magnetic plastic tape. A tape reader wa s used to interpret the instructions written on the tape for the machine. Together, all of this

39、represented a giant step forward in the control of machine tools. However, there were a number of problems with NC at this point in its development.A major problem was the fragility of the punched paper tape medium. It was co mmon for the paper tape containing the programmed instructions to break or

40、 tear duri ng a machining process. This problem was exacerbated by the fact that each successiv e time a part was produced on a machine tool, the paper tape carrying the programme d instructions had to be rerun through the reader. If it was necessary to produce 100 co pies of a given part, it was al

41、so necessary to run the paper tape through the reader 100 separate tines. Fragile paper tapes simply could not withstand the rigors of a shop floo r environment and this kind of repeated use.This led to the development of a special magnetic plastic tape. Whereas the paper carried the programmed inst

42、ructions as a series of holes punched in the tape, the plast ic tape carried the instructions as a series of magnetic dots. The plastic tape was much stronger than the paper tape, which solved the problem of frequent tearing and breaka ge. However, it still left two other problems.The most important

43、 of these was that it was difficult or impossible to change the instructions entered on the tape. To made even the most minor adjustments in a progra m of instructions, it was necessary to interrupt machining operations and make a new tape. It was also still necessary to run the tape through the rea

44、der as many times as the re were parts to be produced. Fortunately, computer technology became a reality and s oon solved the problems of NC associated with punched paper and plastic tape.The development of a concept known as direct numerical control (DNC) solved t he paper and plastic tape problems

45、 associated with numerical control by simply elimin ating tape as the medium for carrying the programmed instructions. In direct numerica l control, machine tools are tied, via a data transmission link, to a host computer. Prog rams for operating the machine tools are stored in the host computer and

46、 fed to the ma chine tool an needed via the data transmission linkage. Direct numerical control repre sented a major step forward over punched tape and plastic tape. However, it is subject to the same limitations as all technologies that depend on a host computer. When the h ost computer goes down,

47、the machine tools also experience downtime. This problem l ed to the development of computer numerical control. 3 TurningThe engine lathe, one of the oldest metal removal machines, has a number of use ful and highly desirable attributes. Today these lathes are used primarily in small shop s where sm

48、aller quantities rather than large production runs are encountered.The engine lathe has been replaced itnoday s production shops by a wide variety of automatic lathes such as automatic of single-point tooling for maximum metal rem oval, and the use of form tools for finish on a par with the fastest

49、processing equipme nt on the scene today.Tolerances for the engine lathe depend primarily on the skill of the operator. The design engineer must be careful in using tolerances of an experimental part that has be en produced on the engine lathe by a skilled operator. In redesigning an experimental part for production, economical tolerances should be used.Turret Lathes Production machining equipment must be evaluated now, more th anever before, this criterion for establishing the pr