【机械类毕业论文中英文对照文献翻译】数字控制和车削加工
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机械类毕业论文中英文对照文献翻译
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数字控制
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加工
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【机械类毕业论文中英文对照文献翻译】数字控制和车削加工,机械类毕业论文中英文对照文献翻译,机械类,毕业论文,中英文,对照,文献,翻译,数字控制,车削,加工
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附件1：外文资料翻译译文数字控制和车削加工 1、车床车床是一种主要被用来车削，车端面，钻孔等工作而设计的机床，车削很少在其他类型的车床上工作，在其他种类的机床上进行车削都不像在车床上那么方面。由于车床也能够用来钻孔和铰孔，车床的多功能特性允许工件在一次装夹中进行多种操作。因此，在生产中使用的各种类型的车床比其他任何种类机床都要多。 车床的基本组成部分有：床身、主轴箱部件、尾架部件、丝杠和光杠。床身是车床的主要组成部分。它通常是经过正火处理或者球墨铸铁制成，其他所有基本部件都安装在床身上。在床身上通常有两组平行的导轨，有些制造厂全部四条导轨采用三角形导轨，而有些制造厂在一组或两组中采用一个三角形导轨和一个矩形导轨，导轨经过精密加工以保证其精度。大多数现代机床的导轨是经过表面淬硬的，但在操作时还是应该小心，以避免导轨受到损坏。导轨的任何误差通常意味着整个机床的精度收到破坏。主轴箱安装在内导轨的固定位置上，通常在床身的左侧。它提供动力并可以使工件以不同速度旋转。大多数机床有818种转速，通常以等比数列排列，而且现代车床只需移动24个手柄就能得到全部转速。一种不断增长的趋势是通过电气或者机械装置来进行无级变速。由于机床的精度很大依赖于主轴，所以主轴的尺寸比较大，通常安装在圆锥滚子轴承和球轴承中，主轴中有一个穿过整个主轴的长孔，通过这个孔长棒料可以送料，当工件必须通过主轴孔送料时，确定了能够被加工的棒料的最大尺寸。尾架部件主要有三部分组成，底板与床身的内导轨配合着，并可以在导轨上做纵向移动，底板上有一个可以是整个尾架加紧在任何位置的装置。尾架固定在底板上可以在某种类型键槽的底板上横向移动，可以允许尾架与主轴箱中的主轴对正。这是一个直径通常大约在5176mm（23英寸）之间的空心钢制圆柱体，通过手轮和螺杆，尾架套筒可以在尾架中移入和移出几英寸。车床的规格被设计成两个尺寸，第一个被称为车床床面上最大加工直径。这是在车床上所能旋转的工件的最大直径，它大约是两项顶尖连线和导轨上最近点之间距离的两倍，第二个规格尺寸是两顶尖之间的最大距离，车床床面的最大加工直径表示在车床上能够车削的最大工件直径，而两顶尖之间的最大距离表示的是两顶尖之间能够安装的工件的最大长度。普通车床是最经常使用到的车床种类。它们具有前面介绍的所有那些部件的重型机床，并且除了小刀架之外，全部刀具的运动都有机会进给。它们通常的尺寸：车床床面上的最大加工直径为305610mm（1224英寸）；两顶尖之间的距离为6101219mm（2448英寸）。但是，车床床面上最大加工直径达到1270mm（50英寸）和两顶尖距离达到3658mm（12英尺）的车床也并不少见。这些车床大多数都有切削盘和一个内置冷却循环系统。较小的普通车床，车床床面的最大加工直径一般不超过330mm（13英寸），其中一些也能够被设计成台式车床，即床身可安装在工作台或者柜子上。虽然普通车床功能很强大，有很多用途，由于更改和设置调整刀具及对工件进行测量需要花费大量时间，所以它们不适合批量生产。通常情况下，它们的实际加工时间要少于总时间的30%。此外，需要熟练的操作工人来操作所需要的所有操作，这种人工资很高而且往往供不应求。然而操作工人的大部分时间却花费在简单的重复劳动和观察切削过程中。因此，为了减少或者完全不顾用这类熟练操作工人，转塔车床、螺纹加工车床和其他类型的自动或半自动车床已经很好的研制了出来并在生产制造中得到了广泛的应用。 2、数字控制先进制造技术中一个最基本的概念就是数字控制。在数控技术出现之前，所有的机床都是由人工操纵和控制的。在人工操纵机床的很多限制中，操作者技能的限制是一个最突出的问题。采用人空控制时，产品的质量直接和操作者的技能有关，数字控制代表了从人工控制走出来的第一步。数字控制意味着采用预先录制和存储的指令来控制机床和其他制造系统。一个数控工程师的不是去操作一台机床而是编写出能够发出机器操作指令的程序。对于一台数控机床，上面必须安装有一个叫做阅读机的装置，用于接收和解码编程指令。数控技术的发展是为了克服人工操作的局限性，并且它已经很好地这么做了。数字控制的机器比人工操纵的机器有更高的精度，生产出的零件一致性更好，生产速度更快，而且长期工艺成本更低。数控技术的发展导致了制造技术中其他几项发明创新的产生：电火花加工技术，激光切割，电子束焊接。数字控制还使得机床比它们人空操纵的前辈们的用途更为广泛。一台数控机床能够自动生成很多种零件，每一个零件都有各种不同的复杂的加工过程。数字可以使生产厂家承担那些对于采用人工控制的机床和工艺来说，在经济上是不划算的产品生产任务。同很多先进技术一样，数控技术诞生于麻省理工学院的实验室里。数控这个概念是在20世纪50年代初在美国空军的资助下提出的。在最初阶段，数控机床只能够做出有效的直线切割。然而，曲线加工在机床加工中是一个难题，在编程时应该采用横向与竖向的一系列步骤来生成一个曲线，构成步骤的直线越短，曲线就越光滑。步骤中的每一个线段都必须经过计算。这个问题导致了1959年自动编程（APT）语言的诞生。这是一门专门用于数控的编程语言，它使用一种特殊的类似英文符号的语言来定义几何零件，描述切削是刀具的形状和规定必要的运动。APT编程语言的发展是在数控技术进一步发展中的一大进步。那时候的机床只有硬线逻辑电路，指令程序被写在穿孔纸带上，后来它被塑料带所取代。带阅读机被用来把写在纸带上的的指令给机器翻译出来，所有的这一切都代表了机床数控的巨大进步。然而，在数控发展的这个阶段还是有很多问题。一个主要问题就是打孔纸带的易碎坏性。在机械加工过程中，载有程序指令的纸带断裂或者被撕裂是一件很常见的事情。在机床上每加工一个零件，都需要将载有程序指令的纸带放入阅读机中重新运行一次，因此，这个问题变得更加严重。如果需要制造100个某种零件，则要将纸带通过阅读机100次。脆弱的纸带根本无法承受这样残酷的车间环境和这种重复使用。这就导致了一种磁性胶带的发展，在纸带上通过一系列的小孔来载有编程指令，在塑料胶带上通过采用一系列的磁点来载有编程指令。塑料纸带的强度要比纸质纸带的强度要强很多，这就解决了常见的断裂和撕裂问题。然而，仍然有两个问题。其中最重要的一个问题是很难或者说几乎不可能修改磁带上输入的指令。即使对指令程序进行很轻微的调整，也有必要中断加工并制作一条新带。而且带通过阅读器的速度必须要和加工的零件个数相同。幸运的是，计算机技术已经变成现实，并且很快地解决了数控加工与穿孔纸带和塑料纸带相关的问题。在形成了直接数字控制（DNC）这个概念之后，可以不再采用纸带或塑料带作为编程指令的载体，这样就解决了与之有关的问题。在直接数字控制中，机床通过数据传输线路连接到一台主计算机上。操纵这台机床所需要的程序都存储在主计算机中，当需要时，通过数据传输线路提供给每台机床。直接数字控制在穿孔纸带和塑料纸带的基础上迈出了一大步。然而，它有着同其他依赖于主计算机技术一样的限制性。当主计算机发生故障时，由其控制的所有机床也会停止工作。这个问题导致了计算机数控的发展。 3、车削加工普通车床作为最古老的切削车床之一，目前仍然有很多有用的和重要的特性。现在，这些机床主要用于一些小规模的工厂中，进行小批量的生产而不是进行大规模的量产。在现在的生产车间中普通车床已经被种类繁多的自动车床所代替，比如自动仿形车床。现在，实用这种加工方法的生产速度和工厂中使用的最快的加工设备的速度相等。普通车床的公差主要依赖于操作工人的熟练程度。设计工程师应该认真地确定由熟练工人在普通车床上加工的试验件的公差。在把试验件重新设计成生产零件时，应选用经历的公差。六角车床 对生产加工设备来说，目前比过去更注重评价其是否具有精确的快速的重复加工能力。应用这个标准来评价具体加工方法，六角车床可以获得较高的质量评定。在为小批量的零件（100200件）设计加工方法时，采用六角车床是最经济的。为了在六角车床上获得尽可能小的公差，设计人员应尽量将加工工序的数量减到最小。自动螺丝车床 一般来说，自动螺丝车床分为以下几种：单轴自动、多轴自动和自动加紧车床。自动螺丝车床最初被用来对螺钉和类似的带有螺纹的零件进行自动化和快速加工的。但是，这种车床的用途早就超过了这个狭窄的范围。现在，它在许多种类的精密零件的大批量生产中起着重要的作用。工件的数量对采用自动螺丝车床所加工的零件的经济性有较大的影响。如果工件的数量少于1000件，在六角车床上进行加工比在自动螺丝车床上加工要经济得多。如果计算出最小经济批量，并且针对工件批量正确地选择机床，就会降低零件的加工成本。自动仿形车床 因为零件的表面粗糙度在很大程度上取决于工件材料、刀具、进给量和切削速度，采用自动仿形车床加工所得到的最小公差一定是最经济的公差。在某些情况下，在连续生产过程中，只进行一次切削加工时的公差可以达到0.05mm。对于某些零件，槽宽的公差可以达到0.125mm。镗孔和休用单刃刀具进行精加工时，公差可达到0.0125mm。在希望获得最大主量的大批量生产中，进行直径和长度的车削时的最小公差值为0.125mm是经济的。附件2：外文原文NC control and cutting1 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 single 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 made 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 four 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 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 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 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 tapered 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 casting 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 tailstock 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. This 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 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 previously 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. 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 of 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 such 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 semiautomatic 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 and 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 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 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 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 discharge 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. Numerical 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 Technology. 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 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 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 today. 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 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 common for the paper tape containing the programmed instructions to break or tear during a machining process. 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 tape 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 punched 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 difficult 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 parts 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 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 the 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. 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 runs 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.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 been 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,
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