數(shù)控車床畢業(yè)設(shè)計外文翻譯

1、latheslathes are machine tools designed primarily to do turning, facing and boring, very little turning is done on other types of machine tools, and none can do it with equal facility. because lathes also can do drilling and reaming, their versatility permits several operations to be done with a sin

2、gle setup of the work piece. consequently, more lathes of various types are used in manufacturing than any other machine tool.the essential components of a lathe are the bed, headstock assembly, tailstock assembly, and the leads crew and feed rod.the bed is the backbone of a lathe. it usually is mad

3、e of well normalized or aged gray or nodular cast iron and provides s heavy, rigid frame on which all the other basic components are mounted. two sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side. some makers use an inverted v-shape for all fou

4、r ways, whereas others utilize one inverted v and one flat way in one or both sets, they are precision-machined to assure accuracy of alignment. on most modern lathes the way are surface-hardened to resist wear and abrasion, but precaution should be taken in operating a lathe to assure that the ways

5、 are not damaged. any inaccuracy 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 left end of the bed. it provides a powered means of rotating the word at various speeds . essentially, it consists

6、of a hollow spindle, mounted in accurate bearings, and a set of transmission gears-similar to a truck transmissionthrough which the spindle can be rotated at a number of speeds. most lathes provide from 8 to 18 speeds, usually in a geometric ratio, and on modern lathes all the speeds can be obtained

7、 merely by moving from two to four levers. an increasing trend is to provide a continuously variable speed 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 t

8、apered roller or ball types. the spindle has a hole extending through its length, through which long bar stock can be fed. the size of maximum size of bar stock that can be machined when the material must be fed through spindle.the tailsticd assembly consists, essentially, of three parts. a lower ca

9、sting fits on the inner ways of the bed and can slide longitudinally thereon, with a means for clamping 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 aligning the assembly is the tailst

10、ock quill. this is a hollow steel cylinder, usually about 51 to 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 swing. thi

11、s is the maximum diameter of work that can be rotated on a lathe. it is approximately 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 centers. the swing thus indicates the maximum work piece

12、 diameter that can be turned in the lathe, while the distance between centers indicates the maximum length of work piece that can be mounted between centers. engine lathes are the type most frequently used in manufacturing. they are heavy-duty machine tools with all the components described previous

13、ly and have power drive for all tool movements except on the compound rest. they commonly range in size from 305 to 610 mm(12 to 24 inches)swing and from 610 to 1219 mm(24 to 48 inches) center distances, but swings up to 1270 mm(50 inches) and center distances up to 3658mm(12 feet) are not uncommon.

14、 most have chip pans and a built-in coolant circulating 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

15、f the time required 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 than 30% of the total cycle time. in addition, a skilled machinist is required for all the operations, and suc

16、h persons are costly and often in short supply. however, much of the operators time is consumed by simple, repetitious adjustments and in watching chips being made. consequently, to reduce or eliminate the amount of skilled labor that is required, turret lathes, screw machines, and other types of se

17、miautomatic and automatic lathes have been highly developed and are widely used in manufacturing.2 numerical controlone of the most fundamental concepts in the area of advanced manufacturing technologies is numerical control (nc). prior to the advent of nc, all machine tools ere manually operated an

18、d controlled. among the many limitations associated with manual control machine tools, perhaps none is more prominent than the limitation of operator skills. with manual control, the quality of the product is directly related to and limited to the skills of the operator. numerical control represents

19、 the first major step away from human control of machine tools. numerical control means the control of machine tools and other manufacturing systems through the use of prerecorded, written symbolic instructions. rather than operating a machine tool, an nc technician writes a program that issues

20、 operational instructions 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, known as a reader.numerical control was developed to overcome the limitation of human operators, and it has done

21、 so. numerical control machines are more accurate than manually operated machines, they can produce parts more uniformly, they are faster, and the long-run tooling costs are lower. the development of nc led to the development of several other innovations in manufacturing technology: electrical disch

22、arge machining,laser cutting,electron beam welding.numerical control has also made machine tools more versatile than their manually operated predecessors. an nc machine tool can automatically produce a wide of parts, each involving an assortment of widely varied and complex machining processes. nume

23、rical control has allowed manufacturers to undertake the production of products that would not have been feasible from an economic perspective using manually controlled machine tolls and processes.like so many advanced technologies, nc was born in the laboratories of the massachusetts institute of t

24、echnology. the concept of nc was developed in the early 1950s with funding provided by the u.s. air force. in its earliest stages, nc machines were able to made straight cuts efficiently and effectively. however, curved paths were a problem because the machine tool had to be programmed to undertake

25、a series of horizontal and vertical steps to produce a curve. the shorter the straight lines making up the steps, the smoother is the curve, each line segment in the steps had to be calculated. this problem led to the development in 1959 of the automatically programmed tools (apt) language. this is

26、a special programming language for nc that uses statements similar to english language to define the part geometry, describe the cutting tool configuration, and specify the necessary motions. the development of the apt language was a major step forward in the fur ther development from those used tod

27、ay. the machines had hardwired logic circuits. the instructional programs were written on punched paper, which was later to be replaced by magnetic plastic tape. a tape reader was used to interpret the instructions written on the tape for the machine. together, all of this represented a giant step f

28、orward 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 common for the paper tape containing the programmed instructions to break or tear during a machining pr

29、ocess. this problem was exacerbated by the fact that each successive time a part was produced on a machine tool, the paper tape carrying the programmed instructions had to be rerun through the reader. if it was necessary to produce 100 copies of a given part, it was also necessary to run the paper t

30、ape through the reader 100 separate tines. fragile paper tapes simply could not withstand the rigors of a shop floor environment and this kind of repeated use.this led to the development of a special magnetic plastic tape. whereas the paper carried the programmed instructions as a series of holes pu

31、nched in the tape, the plastic 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 breakage. however, it still left two other problems. the most important of these was that it was difficu

32、lt or impossible to change the instructions entered on the tape. to made even the most minor adjustments in a program 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 reader as many times as there were pa

33、rts to be produced. fortunately, computer technology became a reality and soon solved the problems of nc associated with punched paper and plastic tape.the development of a concept known as direct numerical control (dnc) solved the paper and plastic tape problems associated with numerical control by

34、 simply eliminating tape as the medium for carrying the programmed instructions. in direct numerical control, machine tools are tied, via a data transmission link, to a host computer. programs for operating the machine tools are stored in the host computer and fed to the machine tool an needed via t

35、he data transmission linkage. direct numerical control represented 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 host computer goes down, the machine tools also experience downtime.

36、 this problem led to the development of computer numerical control.3 turningthe engine lathe, one of the oldest metal removal machines, has a number of useful and highly desirable attributes. today these lathes are used primarily in small shops where smaller quantities rather than large production r

37、uns are encountered.the engine lathe has been replaced in todays production shops by a wide variety of automatic lathes such as automatic of single-point tooling for maximum metal removal, and the use of form tools for finish on a par with the fastest processing equipment on the scene today.toleranc

38、es 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 been produced on the engine lathe by a skilled operator. in redesigning an experimental part for production, economical tolerances should be

39、 used.turret lathes production machining equipment must be evaluated now, more than ever before, this criterion for establishing the production qualification of a specific method, the turret lathe merits a high rating. in designing for low quantities such as 100 or 200 parts, it is most economi

40、cal to use the turret lathe. in achieving the optimum tolerances possible on the turrets lathe, the designer should strive for a minimum of operations.automatic screw machines    generally, automatic screw machines fall into several categories; single-spindle automatics, multiple-spin

41、dle automatics and automatic chucking machines. originally designed for rapid, automatic production of screws and similar threaded parts, the automatic screw machine has long since exceeded   the confines of this narrow field, and today plays a vital role in the mass production of a variet

42、y of precision parts. quantities play an important part in the economy of the parts machined on the automatic screw machine. quantities less than on the automatic screw machine. the cost of the parts machined can be reduced if the minimum economical lot size is calculated and the proper machine is s

43、elected for these quantities. automatic tracer lathes   since surface roughness depends greatly on material turned, tooling , and feeds and speeds employed, minimum tolerances that can be held on automatic tracer lathes are not necessarily the most economical tolerances.in some cases, tole

44、rances of 0.05mm are held in continuous production using but one cut . groove width can be held to 0.125mm on some parts. bores and single-point finishes can be held to 0.0125mm. on high-production runs where maximum output is desirable, a minimum tolerance of 0.125mm is economical on both diameter

45、and length of turn.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(shè)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(chǔ)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導軌尖朝上的

46、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，就能得到全部轉(zhuǎn)速。

47、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(jié)構(gòu)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。尾座組件主要由三部分組成。底板與床身的內(nèi)側(cè)導軌配合，并可以在導軌上作縱向移動。底板上有一個可以使整個尾座組件夾緊在任意位置上的裝置。尾座體安裝在底板上，可以沿某種類型的鍵槽在底板上橫向移動，使尾座能與主軸箱中的主軸對正。尾座的第三個組成部分是尾座套筒。它是一個直徑通常大約

48、在5176mm（23英寸）之間的鋼制空心圓柱體。通過手輪和螺桿，尾座套筒可以在尾座體中縱向移入和移出幾個英寸。 車床的規(guī)格用兩個尺寸表示。第一個稱為車床的床面上最大加工直徑。這是在車床上能夠旋轉(zhuǎn)的工件的最大直徑。它大約是兩頂尖連線與導軌上最近點之間距離的兩倍。第二個規(guī)格尺寸是兩頂尖之間的最大距離。車床床面上最大加工直徑表示在車床上能夠車削的最大工件直徑，而兩頂尖之間的最大距離則表示在兩個頂尖之間能夠安裝的工件的最大長度。普通車床是生產(chǎn)中最經(jīng)常使用的車床種類。它們是具有前面所敘的所有那些部件的重載機床，并且除了小刀架之外，全部刀具的運動都有機動進給。它們的規(guī)格通常是：車床床面上最大加工直徑為30

49、5610mm（1224英寸）；但是，床面上最大加工直徑達到1270mm（50英寸）和兩頂尖之間距離達到3658mm的車床也并不少見。這些車床大部分都有切屑盤和一個安裝在內(nèi)部的冷卻液循環(huán)系統(tǒng)。小型的普通車床車床床面最大加工直徑一般不超過330mm（13英寸）-被設(shè)計成臺式車床，其床身安裝在工作臺或柜子上。雖然普通車床有很多用途，是很有用的機床，但是更換和調(diào)整刀具以及測量工件花費很多時間，所以它們不適合在大量生產(chǎn)中應用。通常，它們的實際加工時間少于其總加工時間的30%。此外，需要技術(shù)熟練的工人來操作普通車床，這種工人的工資高而且很難雇到。然而，操作工人的大部分時間卻花費在簡單的重復調(diào)整和觀察切屑過

50、程上。因此，為了減少或者完全不雇用這類熟練工人，六角車床、螺紋加工車床和其他類型的半自動和自動車床已經(jīng)很好地研制出來，并已經(jīng)在生產(chǎn)中得到廣泛應用。2.數(shù)字控制先進制造技術(shù)中的一個基本的概念是數(shù)字控制（nc）。在數(shù)控技術(shù)出現(xiàn)之前，所有的機床都是由人工操縱和控制的。在與人工控制的機床有關(guān)的很多局限性中，操作者的技能大概是最突出的問題。采用人工控制是，產(chǎn)品的質(zhì)量直接與操作者的技能有關(guān)。數(shù)字控制代表了從人工控制機床走出來的第一步。數(shù)字控制意味著采用預先錄制的、存儲的符號指令來控制機床和其他制造系統(tǒng)。一個數(shù)控技師的工作不是去操縱機床，而是編寫能夠發(fā)出機床操縱指令的程序。對于一臺數(shù)控機床，其上必須安有一個

51、被稱為閱讀機的界面裝置，用來接受和解譯出編程指令。發(fā)展數(shù)控技術(shù)是為了克服人類操作者的局限性，而且它確實完成了這項工作。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(shù)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(shù)、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(shù)一樣，數(shù)控誕生于麻省理工學院的實驗室中。數(shù)

52、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(gòu)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(shù)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〈捎脦ч喿x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(gòu)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