机械加工工艺夹具类外文翻译@中英文翻译@外文文献翻译

1 附录 翻译部分 Lathe and Turning The Lathe and Its Construction A lathe is a machine tool used primarily for producing surfaces of revolution flat edges. Based on their purpose ,construction , number of tools that can simultaneously be mounted , and degree of automation ,lathes or, more accurately, lathe-type machine tools can be classified as follows: (1) Engine lathes (2) Toolroom lathes (3) Turret lathes (4) Vertical turning and boring mills (5) Automatic lathes (6) Special-purpose lathes In spite of that diversity of lathe-type machine tools, they all have all have common features with respect to construction and principle of operation .These features can best be illustrated by considering the commonly used representative type, the engine lathe. Following is a description of each of the main elements of an engine lathe , which is shown in Fig.11.1. Lathe bed . The lathe bed is the main frame , involving a horizontal beam on two vertical supporis. It is usually made of grey or nodular cast iron to damp vibrations and is made by casting . It has guideways to allow the carriage to slide easily lengthwise. The height of the lathe bed should be appropriate to enable the technician to do his or her jib easily and comfortably. Headstock. The headstock is fixed at the left hand side of the lathe bed and includes the spindle whose axis is parallel to the guideways (the silde surface of the bed) . The spindle is driven through the gearbox , which is housed within the headstock. The function of the gearbox is to provide a number of different spindle speeds (usually 6 up to 18 speeds) . Some modern lathes have headstocks with infinitely variable spindle speeds, which employ frictional , electrical , or hydraulic drives. The spindle is always hollow , I .e ,it has a through hole extending lengthwise. Bar stocks can be fed througth that hole if continous production is adopted . A lso , that hole has a tapered 2 surface to allow mounting a plain lathe center . The outer surface of the spindle is threaded to allow mounting of a chuck , a face plate , or the like . Tailstock . The tailstock assembly consists basically of three parts , its lower base, an intermediate part, and the quill . The lower base is a casting that can slide on the lathe bed along the guidewayes , and it has a clamping device to enable locking the entire tailstock at any desired location , depending upon the length of the workpiece . The intermediate parte is a casting that can be moved transversely to enable alignment of the axis of the the tailstock with that of the headstock . The third part, the quill, is a hardened steel tube, which can be moved longitudinally in and out of the intermediate part as required . This is achieved through the use of a handwheel and a screw , around which a nut fixed to the quill is can be locked at any point along its travel path by means of a clamping device. The carriage. The main function of the carriage is mounting of the cutting tools and generating longitudinal and /or cross feeds. It is actually an H-shaped block that slides on the lathe bed between the headstock and tailstock while being guided by the V-shaped guideways of the bed . The carriage can be moved either manually or mechanically by means of the apron and either the feed rod or the lead screw. When cutting screw threads, power is provided to the gearbox of the apron by the lead screw. In all other turning operations, it is the feed rod that drives the carriage. The lead screw goes through a pair o half nuts , which are fixed to the rear of the apron . When actuating a certain lever, the half nuts are clamped together and engage with the rotating lead screw as a single nut, which is fed , together with carriage, along the bed . when the lever is disengaged , the half nuts are released and the carriage stops. On the other hand , when the feed rod is used, it supplies power to the apron through a wrom gear . The latter is keyed to feed rod and travels with the apron along the feed rod , which has a keyway extending to cover its whole length. A modern lathe usually has a quick-change gearbox located under the headstock and driven from the spindle through a train of gears. It is connected to both the feed rod and the lead screw and enables selecting a variety of feeds easily and rapidly by simply shifting the appropriate levers, the quick-change gearbox is employed in plain turning, facing and thread cutting operations. Since that gearbox is linked to spindle, the distance that the apron (and the cutting tool) travels for each revolution of the spindle can be controlled and is referred to as the feed. Lathe Cutting Tools The shape and geometry of the lathe tools depend upon the purpose for which they are employed. Turning tools can be classified into tow main groups,namely,external cutting tools and 3 internal cutting tools , Each of these groups include the following types of tools: Turning tools. Turing tools can be either finishing or rough turning tools . Rough turning tools have small nose radii and are used for obtaining the final required dimensions with good surface finish by marking slight depth of cut . Rough turning tools can be right hand or left-hand types, depending upon the direction of feed. They can have straight, bent, or offset shanks. Facing tools . Facing tools are employed in facing operations for machining plane side or end surfaces. There are tools for machining left-hand-side surfaces and tools for right-hand-side surfaces. Those side surfaces are generated through the use of the cross feed, contrary to turning operations, where the usual longitudinal feed is used. Cutoff tools. Cutoff tools ,which are sometimes called parting tools, serve to separate the workpiece into parts and/or machine external annual grooves. Thread-cutting tools. Thread-cutting tools have either triangular, square, or tranpezoidal cutting edges, depending upon the cross section of the desired thread .Also , the plane angles of these tools must always be identical to those of the thread forms. Thread-cutting tools have straight shanks for external thread cutting and are of the bent-shank type when cutting internal threads . Form tools. Form tools have edges especially manufactured to take a certain form, which is opposite to the desired shape of the machined workpiece . An HSS tools is usually made in the form of a single piece ,contrary to cemented carbides or ceramic , which are made in the form of tipes. The latter are brazed or mechanically fastened to steel shanks. Fig.1indicates an arrangement of this latter type, which includes the carbide tip , the chip breaker ,the pad ,the clamping screw (with a washer and a nut ) , and the shank. As the name suggests, the function of the chip breaker is to break long chips every now and then , thus preventing the formation of very long twisted ribbons that may cause problems during the machining operations . The carbide tips ( or ceramic tips ) can have different shapes, depending upon the machining operations for which they are to be employed . The tips can either be solid or with a central through hole ,depending on whether brazing or mechanical clamping is employed for mounting the tip on the shank. 4 Fig.1 Lathe Operations In the following section , we discuss the various machining operations that can be performed on a conventional engine lathe. It must be borne in mind , however , that modern computerized numerically controlled lathes have more capabiblities and do other operations ,such as contouring , for example . Following are conventional lathe operations. Cylindrical turning . Cylindrical turning is the the simplest and the most common of all lathe operations . A single full turn of the workpiece generate a circle whose center falls on the lathe axis； this motion is then reproduced numerous times as a result of the axial feed motion of the tool. The resulting machining marks are , therefore ,a helix having a very small pitch, which is equal to the feed . Consequently , the machined surface is always cylindrical. The axial feed is provided by the carriage or the compound rest , either manually or automatically, whereas the depths of cuts is controlled by the cross slide . In roughing cuts , it is recommended that large depths of cuts (up to 0.25 in. or 6 mm, depending upon the workpiece material) and smaller feeds would be used. On the other hand , very fine feeds, smaller depth of cut (less than 0.05in. , or 0.4 mm) , and high cutting speeds are preferred for finishing cuts. Facing . The result of a facing operation is a flat surface that is either the whole end surface of the workpiece or an annular intermediate surface like a shoulder . During a facing operation ,feed is provided by the cross slide, whereas the depth of cut is controlled by the carriage or compound rest . Facing can be carried out either from the periphery in ward or from the center of the workpiece outward . It is obvious that the machining marks in both cases tack the form of a spiral. Usually, it is preferred to clamp the carriage during a facing operation, since the cutting force tends to push the tool ( and , of course , the whole carriage ) away from the workpiece . In most facing operations , the workpiece is held in a chuck or on a face plate. Groove cutting. In cut-off and groove-cutting operations ,only cross feed of the tool is 5 employed. The cut-off and grooving tools , which were previously discussed, are employed. Boring and internal turning . Boring and internal are performed on the internal surfaces by a boring bar or suitable internal workpiece is solid, a drilling operation must be performed first . The drilling tool is held in the tailstock, and latter is then fed against the workpiece. Taper turning . Taper turning is achieved by driving the tool in a direction that is not paralled to the lathe axis but inclined to it with an angle that is equal to the desired angle of the taper . Following are the different methods used in taper-turning practice: （ 1） Rotating the disc of the compound rest with an angle to half the apex angle of the cone . Feed is manually provided by cranking the handle of the compound rest . This method is recommended for taper turning of external and internal surfaces when the taper angle is relatively large. （ 2） Employing special form tools for external , very short ,conical surfaces . The width of the workpiece must be slightly smaller than that of the tool ,and the workpiece is usually held in a chuck or clamped on a face plate . I n this case , only the cross feed is used during the machining process and the carriage is clamped to the machine bed . （ 3） Offsetting the tailstock center . This method is employed for esternal tamper turning of long workpiece that are required to have small tamper angles (less than 8 ) . The workpiece is mounted between the two centers ； then the tailstock center is shifted a distance S in the direction normal to the lathe axis. （ 4） Using the taper-turning attachment . This method is used for turning very long workpoece , when the length is larger than the whole stroke of the compound rest . The procedure followed in such cases involves complete disengagement of the cross slide from the carriage , which is then guided by the taper-turning attachment . During this process, the automatic axial feed can be used as usual . This method is recommend for very long workpiece with a small cone angle , i.e. , 8 through 10 . Thread cutting . When performing thread cutting , the axial feed must be kept at a constant rate , which is dependent upon the rotational speed (rpm) of the workpiece . The relatio nship between both is determined primarily by the desired pitch of the thread to be cut . As previously mentioned , the axial feed is automatically generated when cutting a thread by means of the lead screw , which drives the carriage . When the lead screw rotates a single revolution, the carriage travels a distance equal to the pitch of the lead screw rotates a single revolutional speed of the lead screw is equal to that of the spindle ( i. e . , that of the workpiece ), 6 the pitch of the resulting cut thread is exactly to that of the lead screw . The pitch of the resulting thread being cut therefore always depends upon the ratio of the rotational speeds of the lead scew and the spindle : w o rk p ie ceofp it ch s cr e w le a d t h eofP it ch D esired = s c rew le ad of w o rkp iec e th eof rpmrpm = spindle-to-carriage gearing ratio This equation is usefully in determining the kinematic linkage between the lathe spindle and the lead screw and enables proper selection of the gear train between them . In thread cutting operations , the workpiece can either be held in the chuck or mounted between the two lathe centers for relatively long workpiece . The form of the tool used must exactly coincide with the profile the thread to be cut , I . e . , triangular tools must be used for triangular threads , and so on . Knurling . knurling is mainly a forming operation in which no chips are prodyced . Tt involves pressing two hardened rolls with rough filelike surfaces against the rotating workpiece to cause plastic deformation of the workpiece metal. Knurling is carried out to produce rough , cylindrical ( or concile )surfaces , which are usually used as handles . Sometimes , surfaces are knurled just for the sake of decoration ； there are different types of patterns of knurls from which to choose . Cutting Speeds and Feeds The cutting speed , which is usually given in surface feet per minute (SFM), is the number of feet traveled in circumferential direction by a given point on the surface (being cut ) of the workpiece in one minute . The relationship between the surface speed and rpm can be given by the following equation : SMF= DN Where D= the diameter of the workpiece in feet N=the rpm The surface cutting speed is dependent primarily upon the machined as well as the material of the cutting and can be obtained from handbooks , information provided by cutting tool manufacturera , and the like . generally , the SFM is taken as 100 when machining cold-rolled or mild steel ,as 50 when machining tougher metals , and as 200 when machining sofer materials . For aluminum ,the SFMis usually taken as 400 or above . There are also other variables that affect the optimal value of the surface cutting speed . These include the tool 7 geometry, the type of lubricant or coolant , the feed , and the depth of cut . As soon as the cutting sped is decided upon , the rotational speed (rpm) of the spindle can be obtained as follows : N = DSFW The selection of a suitable feed depends upon many factors , such as the required surface finish , the depth of cut , and the geometry of the tool used . Finer feeds produce better surface finish ,whereas higher feeds reduce the machining time during which the tool is in direct contact with the workpiece . Therefore ,it is generally recommended to use high feeds for roughing operations and finer feeds for finishing operations. Again, recommend values for feeds , which can be taken as guidelines , are found in handbooks and information booklets provided by cutting tool manufacturers. Here I want to introduce the drilling: Drilling involves producing through or blind holes in a workpiece by forcing a tool , which rotates around its axis , against the workpiece .Consequently , the range of cutting from that axis of rotation is equal to the radius of the required hole .In practice , two symmetrical cutting edges that rotate about the same axis are employed . Drilling operations can be carried out by using either hand drills or drilling machines . The latter differ in size and construction . nevertheless , the tool always rotates around its axis while the workpiece is kept firmly fixed . this is contrary to drilling on a lathe . Cutting Tool for Drilling Operations In drilling operations , a cylindrical rotary-end cutting , called a drill , is employed . The drill can have either one or more cutting edges and corresponding flutes , which can be straight or helical . the function of the flutes is to provide outlet passages for the chips generated during the drilling operation and to allow lubricants and coolants to reach the cutting edges and the surface being machined . Following is a survey of the commonly used drills. Twist drill . The twist drill is the most common type of drill .It has two cutting edges and two helical flutes that continue over the length of the drill body , The drill also consist of a neck and a shake that can be either straight or tapered .In the latter case , the shank is fitted by the wedge action into the tapered socket of the spindle and has a tang , which goes into a slot in the spindle socket ,thus acting as a solid means for transmitting rotation . On the other hand , straight shank drills are held in a drill chuck that is , in turn , fitted into the spindle socket in the same way as tapered shank drills. 8 The two cutting edges are referred to as the lips , and are connected together by a wedge , which is a chisel-like edge . The twist drill also has two margins , which enable proper guidance and locating of the drill while it is in operation . The tool point angle (TPA) is formed by the lips and is chosen based on the properties of the material to be cut . The usual TAP for commercial drills is 118 , which is appropriate for drilling low-carbon steels and cast irons . For harder and tougher metals , such as hardened steel , brasss and bronze , larger TPAs (130 OR 140 ) give better performance . The helix angle of the flutes of the commonly used twist drills ranges between 24 and 30 . When drilling copper or soft plastics , higher values for the helix angle are recommended (between 35 and 45). Twist drills are usually made of high speed steel ,although carbide tipped drills are also available . The size of twist drills used in industrial range from 0.01 up to 3.25 in . (i.e.0.25 up to 80 mm ) . Core drills . A core drill consists of the chamfer , body , neck ,and shank . This type of drill may be have either three or four flutes and an equal number of margins , which ensure superior guidance , thus resulting in high machining accuracy . It can also be seen in Fig 12.2 that a core drill has flat end . The chamfer can have three or four cutting edges or lips , and the lip angle may vary between 90 and 120 . Core drills are employed for enlarging previously made holes and not for originating holes . This type of drill is characterized by greater productivity , high machining accuracy , and superior quality of the drilled surfaces . Gun drills . Gun drills are used for drilling deep holes . All gun drills are straight fluted , and each has a single cutting edge . A hole in the body acts as a conduit to transmit coolant under considerable pressure to the tip of the drill . There are two kinds of gun drills , namely , the center cut gun drill used for drilling blind holes and the trepanning drill . The latter has a cylindrical groove at its center , thus generating a solid core , which guides the tool as it proceeds during the drilling operation. Spade drills . Spade drills are used for drilling large holes of 3.5 in .(90 mm ) or more . Their design results in a marked saving in cost of the tool as well as a tangible reduction in its weight , which facilitates its handling . moreover , this type of drill is easy to be ground .13 9 车床和车削 车床及它的结构 车床是一个主要用来生产旋转表面和端面的机床。 基于他们的目的，结构，能同时装夹刀具的数量，自动化的程度，车床， 或更正确的说， 车床类型的机床依下列各项被分类 为 : (1) 普通车床 (2) 刀剖车床 (3) 六角转塔车床 (4) 立式的车削和镗铣机床 (5) 自动化车床 (6) 专用车床 尽管车床类型机床的多种多样，他们结构和工作的原则都有很大程度上的相似性。通过具有代表性的普通车床这些特征能最好地被说明。 床身 车床的床身是主要的框架，包括在二个垂直支撑架上的水平横梁。它通常由铸铁或者球墨铸铁通过铸造加工而成的用于减少振动。车床上的导轨让床鞍容易地沿纵长滑动。车床床身的高度应该适中，这样使操作人员能够容易地而且舒适地做他或她的工作。 主轴箱 主轴 箱安装在车床床身的左手边位置而且主轴与导轨 (床的滑动表面 )平行。 主轴由齿轮箱驱动，齿轮箱安装在主轴箱中。齿轮箱的功能将提供一些不同的主轴转速 (通常由 6到 18 速度 )。一些现代的车床具有无级调速的功能，由摩擦力、电或液压来驱动。 主轴箱通常为中空的，举个例子而言，它在整个长度方向上是空的。如果采取连续生产杆状坯料可以通过这个洞进给。当然，这个洞有一个锥形表面用于安装车床顶尖。这个外部表面由螺纹连接吸盘，尖盘以及类似的东西。 尾座 尾座基本上三个部份组成，下部分的基础，一个中间的部份和套筒。下部份的基 础是沿着机床床身导轨上滑动的铸件，而且它有一个夹紧装置使其锁定在整个尾座的任何需要的位置，根据工件的长度。中间部分是一个能沿着横向移动用的铸件。第三个部份套筒，是一个淬火处理的钢管，它可以根据需要滑进滑出中间部分。它可以通过手轮实现，在它的周围螺母固定在套筒上，在套筒开放一端的洞中能够固定车床中心线或者其他的像麻花钻镗杆一类的东西，通过夹紧装置套筒能够加紧在任何位置。 刀架 刀架的主要功能是用在刀具的安装和纵向和横向的进给。当被机床 V形导轨引导的时候，它实际上是在主轴箱和尾座之间滑动的一个 H 形块。 刀架可以用手动或机械方式通过托板箱和丝杠或光杠移动。 10 当用于加工螺纹的时候，动力是由托板箱的齿轮箱提供的。在所有的其他车削操作方面，它是由光杠提供动力驱动刀架的。丝杠通过一对半合螺母固定。这个螺母安装在托板箱的后面，当操作特定的杠杆时两个半螺钉一起被夹紧而且与旋转的丝杠构成一个完整的螺钉，当进给时沿床身和刀架一起。当杠杆脱离的时候，这两个半螺钉离开并且刀架停止运动。另一方面，当使用光杠的时候，它经过蜗轮提供力量给托板箱。后者对于光杠和沿着光杠移动的丝杠是关键的，它在整个长度是关键的一部分。一个现代的车床通 常在主轴箱之下位于一个快速变速的齿轮箱和经过一列齿轮传动的主轴。刀架被连接到丝杠和光杠而且能够通过操作杠杆迅速简单地选择一系列的进给，变速齿轮箱应用于普通的车削、平面和螺纹的切削操作。因为那齿轮箱被连接到主轴上的，对于托板箱移动的距离可以被控制。 车刀 车刀的形状和几何尺寸根据车床应用的目的而决定。车削刀具可以分为两种主要的类型即外部的切削刀具和内部的切削刀具，每一个这些小组包括刀具的有下列类型 : 车刀 车刀能用于精加工或者粗加工的工具。粗加工的车刀具有小的刀尖圆弧半径用于大的切削用量。另一方面精加工的 车刀具有大的刀尖圆弧半径用于获得最终需要的尺寸这个尺寸通过小的切削深度获得高的表面质量。粗车刀具有用右手或左手的两种类型，根据进给的方向而定。它们能有直的，弯的，或偏置的刀柄。 端面刀 端面车刀用于待加工的表面或者端面的平面加工。这些刀具有用左手边操作加工表面的和用右手边操作加工表面的。这些表面通过刀具的横向进给实现，和车削刀具相反的是，纵向进给通常被应用。 切断刀 切断刀具，有时叫做分离刀具，可用于切断工件以及 /或以机器制造外的凹槽。 螺纹车刀 螺纹车具有三角形的，正方形，或梯形的刃口，取决于需要 的螺纹的横截面的样式。同时，这些刀具的面角度总是和那些螺纹现状相同的。螺纹切削刀具的直刀柄用于外部的螺纹切削而偏置刀具用于外部螺纹的切削 。 成形车刀 成形车刀是特别用于加工特殊形式截面的加工刀具，与被加工的工件的形状相反。高速钢刀具通常是做成单独的一块整体，和硬质合金刀具或陶瓷刀具相反的是 ， 它们是做成刀尖的形式。后者是由焊接的或者机械方式夹紧与刀柄构成一个整体。图一指出了一系列后者的类型，这些包括碳化物顶尖、断屑器、刀片，紧固螺丝钉 (一个垫圈和一个螺钉 ) 和刀柄。当做名字所说的那样，断屑器的功能 是时不时的切断切屑，如此避免长的带状切屑形成这些带状切屑在操作时可能会带来问题。 碳化物顶尖 ( 或陶瓷的顶尖 ) 可以有不同的形状，根据他们应用的机床操作。顶尖可以是一个整体或者是中央有一个洞，根据这个顶尖是焊接还是用机械夹紧方式使其安装在刀柄上。 11 车床操作 在下列的部分中，我们将讨论能在传统的车床上被运行的各种不同的机床操作。 这个必须铭记于心，然而，现代的数控车床具有更多的功能 并且能做其他的操作，举例来说，比如曲面仿型。下列各项是普通的车床操作。 外圆车削 外圆车削是最简单的和最通常的车床操作。 工件每旋转一周就在工件上产生一个圆心在车身轴线上的轨道 ； 这个动作的多次产生才能实现切削加工。 加工的结果是一个具有很小螺距的螺旋线。结果，已加工表面是圆形的。 轴向进给是由刀架或者是小刀架提供，可用手动或自动化方式实现，然而削减的深度由横向进给实现。在粗车加工时，一般推荐大的切削深度 (从 0.25 到 6 毫米左右，取决于工件的材料 ) 并且会采取较小的进给量。 另一方面，非常小的进给量，非常小切削深度 (小于 0.05 或 0.4 毫米 )，和高的切削速度应用于精加工。 平面车削 平面加工的结果是一平 表面这个表面既可以是整个端面或或者是轴间处的一个环形表面 。 在平面车削过程中，进给量是由横向进给提供的，然而削减的深度是有刀架或者小刀架提供的。平面车削可以从工件的外圆向中心也可以从工件的中心向外圆。很明显这两种加工都产生螺旋形的加工轨迹。通常，在平面加工过程中最好要夹紧刀架，因为切削力容易推动刀具 ( 当然 ， 整个的刀架 ) 远离工件。在大多数平面加工过程中，工件被夹紧在吸盘上或者工作台上。 凹槽切削 在切断和切槽的加工中，只应用刀具的横向进给。那切断和切槽工具，在先前已经讨论过了，用过了。 钻孔和 内表面车削 钻孔和内表面车削是在工件内表面上有钻杆或者是适当的内表面切削刀具， 如果最初的工件是实心的，必须先进行钻孔加工。 钻孔刀具安装在刀架上， 而后刀架相对于工件进行进给。 圆锥面车削 圆锥面车削是通过驱动刀具沿着与车床轴线方向不平行而是与轴线倾斜方向即想得到的圆锥角。下列各项是用圆锥面车削的不同的方法 : （ 1）旋转小刀架上的刀盘使其达到半顶角的度数。进给是通过手动方式旋转小刀架上的手柄方式完成的。这一个方法大多数应用于较大的内圆锥角和角大的外圆锥角切削。 （ 2）采用专用成形刀