机床基础机械加工工艺夹具类外文翻译/中英文翻译/外文文献翻译

          外文翻译   专        业     机械设计制造及自动化   学  生  姓  名         孙   道   德          班        级        BMZ 机制 031       学        号          0361440120        指  导  教  师         刘   必   荣            1 附  件 1: 机  床  基  础   范云涨  著  孙道德  译  摘  要 : 在许多情况下初步加工成型的产品必须在尺寸和表面光洁度方面经过 进一步的加工以满足设计要求。为了满足这么高要求的尺寸，去除少量的材料是必需的。机床通常用于执行这样的操作。   关键字： 机床；车床  机床介绍： 机 床 加工作为 产生形状的一种方法是所有制造过程中最普遍使用的 并 且是最重要的方法。机 床 加工 是一种成型的过程通过电机驱动， 材料以切屑的形式被去除。  大多数的机床加工是通过既支承工件又支承刀具的装备来完成。 尽管在某些场合，工件无支承情况下，使用移动式装备来实现加工 。  小批量生产低费用。 机 床 加工在制造过程中有两 个 方面。对于铸造、锻造和压力加工，每一个要生产的具体工件形状，即使是一 个零件，几乎都要花费高额的加工费用。靠焊接来产生的结构形状，在很大程度上取决于有效的原材料的形状。一般来说，通过利用贵重设备而又无需特种加工条件下，几乎可以从任何种类原材料开始，借助机 床 加工把原材料加工成任意所要求的结构形状，只要外部尺寸足够大，那都是可能的。因此对于生产一个零件， 通常选择机床加工 甚至于当零件结构及要生产的批量大小上按理都适于用铸造、锻造或压力加工来生产的 。  高 的精度和良好表面光洁度。机械加工的第二方面用途是建立在高精度和可能的表面光洁度基础上。许多零件，如果用别的其他方法来生产属大批量生产 的话，那么在机械加工中则是属低公差且又能满足要求的小批量生产了。另方面，许多零件靠较粗的生产加工工艺提供其一般表面形状，而仅仅是在需要高精度的且选择过的表面上才进行机械加工。例如内螺纹，除了机械加工之外，几乎没有别的加工方法能进行加工。 再 如已锻工件上的小孔加工，也是 在 被锻后进行机械加工才完成的。  在美国材料切削业是一个很大的产业 费用每年超过 36 109 美元，包括材料，劳动力，管理费，机床装运费等所花的费用。由于 60机械和工业工程以及技 2 术等级评定工作都跟机床加工工业有某些关系，或者通过买卖、设计或者机器 车间中操作或在有关工业企业中加工，因此，对于工程专业学生来说，在他的学习计划中集中一段时间去学习研究材料切削和机床是个明智的做法。  机床为通过切削工具使工件成型以达到所需的尺寸提供了方法。机床通过其基础构件的功能作用，以控制相互关系方式支持、夹紧工具和工件，现将基本结构部件列举如下：  a）床身，构架或机架。这是一个主要部件，该部件为主轴、拖板箱等提供一个基础和连接中介，在负载作用下，它必须使变形和振动保持最小。  b）拖板箱和导轨。机床部件（如拖板箱）的移动，通常是在精确的导轨面约束下靠直线运动来实现。  c） 主轴和轴承。角位移是围绕一个旋转轴线发生的，该轴线的位置必须在机床中极端精确的限度内保持恒定，而且是靠精密的主轴和轴承来提供保证。  d）动力装置。电动机是为机床所普遍采用的动力装置。通过对各个电机的合适定位，使皮带和齿轮传动装置减少到最少。  e）传动连杆机构。连杆机构是个通用术语，用来代表机械、液压、气动或电动机构的，这些机构与确定的角位移和线性位移相关联。  加工工艺主要有两个组成部分：  a）粗加工。粗加工，金属切除率高，因而往往切削力也大，但所要求的尺寸精度低。  b）精加工。精加工，金属切除率低，因而往往 切削力也小，但所要求的尺寸精度和表面光洁度高。  由此可见，静载荷和动载荷，例如由不平衡的砂轮引起的动载荷，在精加工中比粗加工中有着更为重要的意义。任何加工过程所获得的精度通常将受到由于力的作用引起发生的变形量的影响。  机床座架一般是用铸铁制造的，然而有些也可能用铸钢或中碳钢来制造。选用铸铁是因为它便宜，刚性好，受压强度高，并且有减弱机床操作中产生的振动的能力。为了避免床身铸件硕大断面，精心地设计筋条构架以便提供最大的抗弯曲和抗扭转应力的能力。筋条的两种基本类型是：箱型结构和片状斜支撑式。箱型结构便于生产，箱 壁上有孔口便于使型芯定位和取出。片状斜支撑筋条有较大的抗扭刚度亦能使截面上的碎屑掉落。它常常用于车床床身。机床的拖板箱和导轨是支撑和引导彼此相对运 3 动的零部件，通常是改变刀具相对于工件的位置。运动一般以直线运动的方式，但也有时是转动，例如对应于工件的螺纹上的螺旋角方向而使万能螺纹磨床上的砂轮头转动一个角度。拖板箱构件的基本的几何结构形状是平的、 V 型槽形、燕尾槽形和圆柱形的。这些构件可根据用途，以各种方法分别使用或结合使用。导轨的特性如下：  （ a）运动精确。于此拖板是要按直线移动的，这直线必定是由两个相互垂直的平面形成而且拖板必定不存在转动。机床导轨的直线度公差是每米 0 0.02 毫米，在水平面上这个公差可以进行处理，以使得到凸形表面，这样就抵消导轨下凹的作用。  （ b）调整手段。为了便于装配、维护精度和在发生磨损后便于限制移动构件之间的“窜动”，有时在拖板内装入扁条，这扁条被叫做“锒条”。通常该锒条用穿过长孔的沉头螺钉支住，而用平头螺钉调整好后用锁紧螺母上紧。  （ c）润滑。导轨可用以下两种装置进行润滑：  1）间歇润滑，通过润滑脂嘴或油嘴进行。这是一种适于运动速度低而不频繁场合的方法。  2）连续润滑，例如通过计量阀和 管道将润滑油泵送到润滑点。用这种方法引入两表面间的油膜必定是很薄的，目的是避免使拖板“浮起”。如果滑移表面似镜面平滑，油就会被挤出而导致表面粘贴。因而在实践上，拖板滑移表面是用凹面砂轮的刃进行磨削或进行刮研。两种工艺都可产生微小的表面凹痕，它就成为存油凹陷，相配合的零件就不会处处因“浮起”而发生分离，这样使拖板确定保持接触导轨。  （ d）防护。为了维护导轨处于良好状态，以下条件必须满足：  1）必须防止外面物质，如碎屑进入。具有某一形状的导轨那是所期望的。在这种场合，是不可能进入杂物的，例如是倒 V 形的导轨时，那 就不可能保存碎屑杂物在导轨上。  2）必须保存润滑油。在垂直或倾斜的导轨面上使用的油要有粘性，那很重要。为了这种使用目的已经专门研制出多种有用的润滑油。油的粘性也要保护，以免被切削液冲毁。  3）必须用防护罩来防止意外的破坏。  车床：  一台机床有三个主要功能：（ 1）牢固地支持工件或者刀架和刀具；（ 2）在工件和刀具之间提供相对运动；（ 3）提供一定的走刀和切削速度范围。以去除切屑形式来加工金属的机床一般被分为四大类：使用单点刀具切削的机床；使用多点刀具切削的机 4 床；使用随机点刀具切削的机床（磨削）和考虑用于特殊场合的 机床。  机床本质上使用单点刀具切削包括：（ 1）普通车床；（ 2）塔式车床；（ 3）仿形车床；（ 4）单轴自动车床；（ 5）多轴自动车床；（ 6）牛头刨床和龙门刨床；（ 7）镗床。  使用多点刀具切削的机床包括：（ 1）钻床；（ 2）铣床；（ 3）拉床；（ 4）锯床；（ 5）齿轮切割机床。  使用随机点刀具切削的机床包括：（ 1）外圆磨床；（ 2）无心磨床；（ 3）平面磨床。  普通车床是基本的旋削机床，从这点出发，已经研制出其他旋削机床。驱动电机装在床身基础上并通过齿轮、皮带相结合来驱动主轴，以提供每分钟 25 到 1500 转的转速。主轴是一根坚 固的空心轴，装在重型轴承之间，其前端用来安装驱动盘（花盘），以便把确定的运动传到工件。  该驱动盘可借助螺纹、凸轮锁紧机构或借助一个螺纹垫圈和键固定在主轴上。  车床的床身是铸铁件，它提供精确的磨削的滑动表面（导轨），其上放有拖板。该车床拖板是 H 型的铸件，而刀具就安装在拖板上的刀架上。溜板箱装在拖板前面，并装有移动刀具的齿轮机构，而拖板顺着导轨或横过导轨以提供所希望的刀具的运动。拖板上面的小刀架能使刀夹回转所要求的任意角度。为使刀具作线性运动，在小刀架上装有手轮和丝杆。以手轮和使小刀架垂直于车床导轨移动的丝杆来 提供横向进给。溜板箱中的齿轮系可为拖板沿着导轨和横跨导轨提供动力进给。进给箱齿轮将运动传给拖板并控制刀具相对于工件的运动速度。典型的车床进给范围是主轴每转从0.002 到 0.160 英寸，大约有 50 级转速。由于进给箱的移动运动是由主轴齿轮驱动的，因此进给量直接与主轴速度有关。进给箱齿轮传动机构也用于加工螺纹并能加工每英寸 4 到 224 扣螺纹。  进给箱和车床溜板箱之间的连结轴是光杆和丝杆。许多车床制造商把这两杆结合成一杆，实际上那就以精确的开支减少机器的费用。进给杆（光杆）用于提供刀具的运动，它对于精确的工件和好的表 面光洁度是很重要的。螺纹导杆（丝杆）用于提供精确的（螺纹）导程，这对于螺纹切削是必需的。光杆是通过摩擦离合器来驱动的，那样在刀具切削超载情况下能够打滑保护。这一安全装置不能装在丝杆上，因为螺纹加工是不允许打滑的。由于螺纹全深很难一次走刀加工完成，因此装设一螺纹指示盘作为下几次走刀加工时重新对刀用。  车床装有尾座，它具有一精确的轴，该轴有一锥孔，以便安装钻头、钻夹、铰刀和车床顶针。尾座可以沿着车床导轨移动以适应工件的不同长度以及加工锥体或锥形 5 表面。  转塔车床基本上是具有某种附加特性的普通车床，提供作为半自动加 工和减少人工操作误差的机会。转塔车床的拖板设有 T 形槽以便在车床导轨两端安装夹刀装置，当转塔转入到合适位置时，要正确地装设刀具以便进行切削。拖板也装设有自动停机装置以便控制刀具行程和提供良好的切削的再生产。转塔车床的尾座是六角形结构，在六角头中可以装六把刀具。虽然装刀和加工准备要花大量时间，但转塔车床一次装刀以后无需熟练工人就可以连续地重复地操作加工，直到刀具变钝并需更换为止。这样转塔车床仅就生产工作在经济上是可行的、合理的，于此，根据所制造零件的数量，为加工准备需要花一定数量的时间那是合理的，无可非议的。  单轴自动车床使用一个立式转塔和两个横向溜板。工件通过机床主轴孔被送入卡盘，而刀具是靠凸轮来自动操作控制。  多轴自动车床装有四、五、六或八根主轴并且在每根主轴中装一个工件。各主轴围绕着一根中心轴来转换位置。以主刀具溜板去接近各主轴。每根轴位上都装有一侧向可以独立操作的刀具滑板。由于各刀具滑板都是靠凸轮操作的，因此加工准备可能花几天时间，因而至少需要 5000 件的批量生产，它的使用才是合理的。这种机床的主要优点就是所有的刀具同时工作，并且一个工人可以看管几部机床。对于相对简单的零件而言，多轴自动车床可以以每五秒钟 一件的速度生产加工出成品来。    6 附  件 2: Fundamentals of Machine Tools Abstract:  In many cases products from the forming processes must undergo further refinements in size and surface finish to meet their design specifications. To meet such precise tolerances the removal of small amounts of material is needed. Usually machine tools are used for such operation. Key words: machine tools； Lathes Introduction of Machining Machining as a shape-producing method is the most universally used and the most important of all manufacturing processes. Machining is a shape-producing process in which a power-driven device causes material to be removed in chip form. Most machining is done with equipment that supports both the work piece and cutting tool although in some cases portable equipment is used with unsupported workpiece. Low setup cost for small Quantities. Machining has two applications in manufacturing. For casting, forging, and press working, each specific shape to be produced, even one part, nearly always has a high tooling cost. The shapes that may he produced by welding depend to a large degree on the shapes of raw material that are available. By making use of generally high cost equipment but without special tooling, it is possible, by machining； to start with nearly any form of raw material, so tong as the exterior dimensions are great enough, and produce any desired shape from any material. Therefore .machining is usually the preferred method for producing one or a few parts, even when the design of the part would logically lead to casting, forging or press working if a high quantity were to be produced. Close accuracies, good finishes. The second application for machining is  7 based on the high accuracies and surface finishes possible. Many of the parts machined in low quantities would be produced with lower but acceptable tolerances if produced in high quantities by some other process. On the other hand, many parts are given their general shapes by some high quantity deformation process and machined only on selected surfaces where high accuracies are needed. Internal threads, for example, are seldom produced by any means other than machining and small holes in press worked parts may be completed. In the United States material removal is a big business in excess of $ 36 X 109 per year, including material, labor, overhead, and machine tool shipments, is spent. Since 60 percent of the mechanical and industrial engineering and technology graduates have something connection with the machining industry either through sale, design, or operation of machine shops, or working in related industry it is wise for an engineering student to devote some time in his curriculum to studying material removal and machine tools. A machine tool provides the means for cutting tools to shape a workpiece to required dimensions； the machine supports the tool and the workpiece in a controlled relationship through the functioning of its basic members, which are as follows: (a) Bed, Structure or Frame. This is the main member, which provides a basis for, and a connection between, the spindles and slides； the distortion and vibration under load must be kept to a minimum. (b) Slides and Slideways. The translation of a machine element (e.g. the slide) is normally achieved by straight-line motion under the constraint of accurate guiding surfaces (the slideway). (c) Spindles and Bearings. Angular displacements take place about an axis of rotation； the position of this axis must be constant within extremely fine limits in machine tools, and is ensured by the provision of precision spindles and bearings. (d) Power Unit. The electric motor is the universally adopted power unit  8 for machine tools. By suitably positioning individual motors, belt and gear transmissions are reduced to a minimum. (e) Transmission Linkage. Linkage is the general term used to denote the mechanical, hydraulic, pneumatic or electric mechanisms, which connect angular and linear displacements in defined relationship. There are two broad divisions of machining operations：  (a) Roughing, for which the metal removal rate, and consequently the cutting force, is high, but the required dimensional accuracy relatively low. (b) Finishing, for which the metal removal rate, and consequently the cutting force, is low, but the required dimensional accuracy relatively high. It follows that static loads and dynamic loads, such as result from an unbalanced grindingwheel, are more significant in finishing operations than in roughing operations. The degree of precision achieved in anymachining process will usually be influenced by the magnitude of the deflections, which occur as a result of the force acting.    Machine tool frames are generally made in cast iron, although some may be steel casting or mild-steel fabrications. Cast iron is chosen because of its cheapness, rigidity,compressive strength and capacity for damping the vibrations set-up in machine operations.To avoid massive sections in castings, carefully designed systems of ribbing are used to offer the maximum restance to bending and torsional stresses. Two basic types of ribbing are box and diagonal. The box formation is convenient to produce, a apertures in walls permitting the positioning and extraction of cores. Diagonal ribbing provides grater torsional stiffness and yet permits.swarf to fall between the sections； it is frequently used for lathe beds. The slides and slideways of a machine tool locate and guide members which more relative to eachother, usually changing the position of the tool relative to the workpiece. The movement generally takes the form of translation in a straight line, but is sometimes angular rotation e.g, tilting the wheel-head of a universal thread-grinding machine to an angle corresponding with the  9 helix angle of the workpiece thread. The basic geometric elements of slides are flat, vee,dovetail and cylinder. These elements may be used separately or combined in various according to the applications Features of slidewys are as follows: (a) Accuracy of Movement. Where a slide is to be displaced in a straight line, this line must lie in two mutually perpendicular planes and there must be no slide rotation. The general tolerance for straightness of machine tool slideways is 00.02mm per 1000mm； on horizontal surfaces this tolerance may be disposed so that a convex surface results, thus countering the sffsct of “sag” of the slideway.  (b) Means of Adjustment. To facilitate assembly, maintain accuracy and eliminate “play” between sliding members after wear has taken place, a strip is sometimes inserted in the slides. This is called a gibstrip. Usually, the gib is retained by socket-head screws passing through elongated slots； and is adjusted by grud-screws secured by lock nuts. (c) Lubrication. Slideways may be lubricated by either of the following systems: 1) Intermittently though grease or oil nipples, a method suitable where morements are infrequent and speed low. 2) Continuously, e.g. by pumping though a metering valve and pipe-work to the point of application； the film of oil introduced between surfaces by these means must be extremely thin to avoid the slid “floating”. If sliding surfaces were optically flat oil would be squeezed out, resulting in the surfaces sticking. Hence in practice slide surfaces are either ground using the edge of a cup wheel, or scraped.Both processes produce minute surface depressions, which retain “pocket” of oil, and complete separation of the parts may not occur at all points； positive location of the slides is thus retained. (d) Protection. To maintain slideways in good order, the following conditions must be met:  10 1) Ingress of foreign matter, e.g. swarf, must be prevented when this is no possible, it is desirable to have a form of slideway, which does not retain swarf, e.g. the inverted vee. 2)Lubricating oil must be retained. The adhesive property of oil for use on vertical or inclined slide surface is important； oils are available which have been specially developed for this purpose. The adhesiveness of oil also prevents it being washed away by cutting fluids. 3) Accidental damage must be prevented by protective guardchined following the press working operations .Lathes A machine tool performs three major functions: (1) it rigidly supports the workpiece or its holder and the cutting tool； (2) it provides relative motion between the workpiece and the cutting tool； (3) it provides a range of feeds and speeds. Machines used to remove metal in the form of chips are classified in four general groups : those using single-point tools, those using multipoint tools, those using randompoint tools, and those that are considered special. Machines using basically the single-point cutting tools include: (1) engine lathes, (2) turret lathes, (3) tracing and duplicating lathes, (4) single-spindle automatic lathes, (5) multi-spindle automatic lathes, (6) shapers and planers, (7) boring machines. Machines using multipoint cutting tools include: (1) drilling machines, (2) milling machines, (3) broaching machines, (4) sawing machines, (5) boring machines. Machines using random-point cutting tools include: (1) cylindrical grinder, (2) milling machines, (3) surface grinders. Special metal removal methods include: (1) chemical milling, (2) electrical discharge machining, (3) ultrasonic machining. The lathe removes material by rotating the workpiece against a cutter to produce external or internal cylindrical or conical surfaces. Ti is also  11 commonly used for the production of flat surfaces by facing, in which the workpiece is rotated whiled the cutting tool is moved perpendicularly to the axis of rotation. The engine lathe is the basic turning machine from which other turning machines have been developed. The drive motor is located in the base and drives the spindle through a combination of belts and gears, which provides the spindle speeds, with the forward end used for mounting a drive plate to impart positive motion to the workpiece. The drive plate may be fastened to be the spindle by threads, by a cam lock mechanism, or by a threaded collar and key. The lathe bed is cast iron and provides accurately ground sliding surfaces on which the carriage rides. The lathe carriage is a H-shaped casting on which the cutting tool is mounted in a tool holder. The apron hangs from the front of the carriage and contains the driving gears that move the tool and carriage along or across the way to provide the desired tool motion. A compound rest, located above the carriage provided for rotation of the tool holder through any desired angle. A hand wheel and feed screw are provided on the compound rest for linear motions of the tool. The cross feed is provided with a hand wheel and feed screw for moving the compound rest perpendicular to the lathe way. A gear train in the apron provides power feed for the carriage both along and across the way. The feed box contains gears to impart motion to the carriage and control the rate at which the tool moves relative to the workpiece. On a typical lathe feeds range from 0.002 to 0.160 in. per revolution of the spindle, in about 50 steps. Since the transmission in the feed box is driven from the spindle gears, the feeds are directly related to the spindle speed. The feed box gearing is also used in thread cutting and provides from 4 to 224 threads threads per in. The turret lathe is basically an engine lathe with certain additional features to provide for semiautomatic operation and to reduce the opportunity for human error. The carriage of the turret lathe is provided with T-slots for mounting a tool-holding device on both sides of the lathe ways with tools  12 properly set for cutting when rotated into position. The carriage is also equipped with automatic stops that control the tool travel and provide good reproduction of cuts. The tailstock of the turret lathe is