外文翻译--车床

外文翻译--车床 车 床 用于车外圆、端面和镗孔等加工的机床称作车床。车削很少在其他种类的机床上进行，因为其他机床都不能像车床那样方便地进行车削加工。由于车床除了用于车外圆还能用于镗孔、车端面、钻孔和铰孔，车床的多功能性可以使工件在一次定位安装中完成多种加工。这就是在生产中普遍使用各种车床比其他种类的机床都要多的原因。 两千多年前就已经有了车床。现代车床可以追溯到大约1797年，那时亨利•莫德斯利发明了一种具有把主轴和丝杆的车床。这种车床可以控制工具的机械进给。这位聪明的英国人还发明了一种把主轴和丝杆相连接的变速装置，这样就可以切削螺纹。 车床的主要部件:床身、主轴箱组件、尾架组件、拖板组、变速齿轮箱、丝杆和光杆。 床身是车床的基础件。它通常是由经过充分正火或时效处理的灰铸铁或者球墨铸铁制成，它是一个坚固的刚性框架，所有其他主要部件都安装在床身上。通常在球墨铸铁制成，它是一个坚固的刚性框架，所有其他主要部件都安装在床身上。通常在床身上面有内外两组平行的导轨。一些制造厂生产的四个导轨都采用倒“V”，而另一些制造厂则将倒“V”形导轨和平面导轨结合。由于其他的部件要安装在导轨上并(或)在导轨上移动，导轨要经过精密加工，以保证其装配精度。同样地，在操作中应该小心，以避免损伤导轨。导轨上的任何误差，常常会使整个机床的精度遭到破坏。大多数现代车床的导轨要进行表面淬火处理。以减少磨损和擦伤，具有更大的耐磨性。 主轴箱安装在床身一端内导轨的固定位置上。它提供动力。使工件在各种速度下旋转。它基本上由一个安装在精密轴承中的空心轴和一系列变速齿轮---类似于卡车变速箱所组成，通过变速齿轮，主轴可以在许多中转速的旋转。大多数车床有8,18中转速，一般按等比级数排列。在现代车床上只需扳动2,4个手柄，就能得到全部挡位的转速。目前发展的趋势是通过电气的或机械的装置进行无级变速。 由于车床的精度在很大程度上取决于主轴，因此主轴的结构尺寸较大，通常安装在紧密配合的重型圆锤滚子轴承或球轴承中。主轴中有一个贯穿全长的通孔，长棒料可以通过该孔送料。主轴孔的大小是车床的一个重要尺寸，因为当工件必须通过主轴孔供料时，它确定了能够加工棒料毛坯的最大外径尺寸。 主轴的内端从主轴箱中凸出，其上可以安装多种卡盘、花盘和挡筷。而小型的车床长带有螺纹截面供安装卡盘之用。很多大车床使用偏心夹或键动圆锥。这些附 件组成了一个大直径的圆锥体，以保证对卡盘进行精确地装配，并且不用旋转这些笨重的附件就可以琐定后松开卡盘或花盘。 主轴由电动机经V带或无声链装置提供动力。大多数现代车床有5,15马力的电动机，为硬质合金和金属陶瓷合金刀具提供足够的动力，进行高速切削。 尾座组件主要有三部分组成。底座与床身的内侧导轨配合，并可以在导轨上做纵向移动，底座上有一个可以使整个尾座组件夹紧在任意位置上的装置。尾座安装在底座上，可以沿键槽在底座横向移动，使尾座与主轴箱中的主轴对中并为切削锥体提供方便。尾座组件的第三部分是尾座套筒，它是一个直径通常在2,3英寸之间的刚制空心圆柱轴。通过手轮和螺杆，尾座套筒可以在尾座体中纵向移入和移出几英寸。活动套筒的开口一端具有莫氏锥度，可以用于安装顶尖或诸如钻头之类的各种刀具。通常在活动套筒的外表面刻有几英寸的刻度，以控制尾座的前后移动。锁定装置可以使套筒在所需要的位置上夹紧。 拖板组件用于安装和移动切削工具。拖板上一个相对平滑的H形铸件，安装在床身外侧导轨上，并可在上面移动。 大拖板上有横向导轨，使横向托板可以安装在上面，并通过丝杆使其运动，丝杆由一个小手柄和刻度盘控制。横拖板可以带动刀具垂直于工件的旋转轴线切削。 大多数车床的刀架安装在复式刀座上，刀座上有底座，底座安装在横拖板上，可绕垂直轴和上刀架转动。上刀架安装在底座上，可用手轮和刻度盘控制一个短丝杆使其前后移动。 溜板箱装在大拖板前面，通过溜板箱内的机械装置可以手动和动力驱动大拖板以及动力驱动横拖板。通过转动溜板箱前的手轮，可以手动操作拖板沿床身移动。手轮的另一端与溜板箱背面的小齿轮连接，小齿轮与齿条啮合，齿条倒装在床身前上边缘的下面。 利用光杆可以将动力传递给大拖板和横拖板。光杆上有一个几乎贯穿于整个光杆的键槽，光杆通过两个转向相反并用键连接的锤齿轮传递动力。通过溜板箱前的换向手柄可使啮合齿轮与其中的一个锤齿轮啮合，为大拖板提供“向前”或“向后”的动力。适当的离合器或者与齿条小齿轮连接或者与横拖板的螺杆连接，使拖板纵向移动或使横拖板横向移动。 对于螺纹加工，丝杆提供了第二种纵向移动的方法。光杆通过摩擦离合器驱动拖板移动，离合器可能会产生打滑现象。而丝杆产生的运动是通过溜板箱与丝杆之间的直接机械连接来实现的，对开螺母紧紧包合丝杆。当对开螺母闭合时，可以沿丝杆直接驱动拖板，而不会出现打滑的可能性。 现代车床有一个变速齿轮箱，齿轮箱的输入端由车床主轴通过合适的齿轮传动驱动。齿轮箱的输出端与光杆和丝杆连接。主轴就是这样通过齿轮传动链驱动变速齿轮箱，在带动丝杆和光杆，然后带动拖板，刀具就可以按主轴的转数纵向地或横向地精确移动。一台典型的车床的主轴每转一圈，通过光杆可以获得从0.002到0.118英寸尺寸范围内的48种进给量;而使用丝杆可以车削从1.5到92牙/英寸范围内的48种不同螺纹。一些老式的或廉价的车床为了能够得到所有的进给量和加工出所有螺纹，必须更换主轴和变速齿轮箱之间的齿轮系中的一个或两个齿轮。 LATHES The basic machines that are designed primarily to do turning , facing and boring are called lathes . Very little turning is done on order types of machines tool , and none can do it with equal facility .Because lathe can do boring , facing , drilling , and , reaming in addition to turning ,their versatility permits several operations to be performed with a single setup of the work-piece . This accounts for the fact that lathes of various types are more widely used in manufacturing than any other machine tool . Lathes in various forms have existed for more than two thousand years . Modern lathes date from about 1797 , when Henry Maud-sley developed one with a lead-screw . It provided controlled , mechanical feed of the tool . This ingenious Englishman also developed a change-gear system that could connect the spindle and lead-screw and thus enables thread to be cut . Lathe Construction . The essential components of a lathe are depicted in the block diagram of Fig.15-1. These are the bed , headstock assembly , tailstock assembly , carriage assembly , quick-change gear box , and the lead-screw and feed rod . The bed is the backbone of a lathe .It is usually made of well-normalized or aged gray or nodular cast iron and provides a heavy , rigid frame on which all the other basic components mounted . Two sets of parallel , longitudinal ways , inner and outer , are contained in the bed , usually on the upper side . Some makes use an inverted V-shape for all four ways , whereas others utilize one inverted V and one flat way in one or both sets . Because several other accuracy of alignment . Similarly , proper 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 ways on most modern lathes are surface hardened to offer greater resistance to wear and abrasion . The headstock is mounted in a fixed position on the inner ways at one end of lathe bed . It provides a powered means of rotating the work at various speeds . It consists , essentially , of a hollow spindle , mounted in accurate bearings , and a set of transmission gears-similar to a truck transmission-through which the spindle can be rotated at a number of speeds . Most lathes provided from eight to eighteen 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 provided 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 . A longitudinal hole is an important size dimension of a lathe because it determines the maximum size of bar stock that can be machined when the material must be fed through the spindle . The inner end of the spindle protrudes from the gear box and contains a means for mounting various types of chucks , face plate , and dog plate on it . Whereas small lathes often employ a threaded section to which the chucks are screwed , most large lathes utilize either cam-lock or key-drive taper noses . These provide a large-diameter taper that assures the accurate alignment of the chuck , and a mechanism that permits the chuck or face plate to be locked or unlocked in position without the necessity of having to rotate these heavy attachments . Power is supplied to the spindle by means of an electric motor through a V-belt or silent –chain drive . Most modern lathes have motors of from 5 to 15 horsepower to provide adequate power for carbide and ceramic and ceramic tools at their high cutting speeds . The tailstock 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 fit on the lower one and can be moved transversely upon it on some type of keyed ways . This transverse motion permits aligning the tailstock and headstock spindles and provides a method of turning tapes . The third major component of the assembly is the tailstock quil . This is a hollow steed cylinder , usually about 2 to 3 inches in diameter , that can be moved severed inches longitudinally in and out of the upper casting by means of a handwheel and screw . The open end of the quill hole terminates in a Morse taper in which a lathe center , or various tools such as drills , can be held . A graduated scale , several inches in length , usually is engraved in the outside of the quill to aid in controlling its motion in and out of the upper casting . A locking device permits clamping the quill any desired position . The carriage assembly provides the means for mounting and moving cutting tools . The carriage is a relatively flat H-shaped casting that rest and moves on the outer set of ways on the bed . The transverse bar of the carriage contains ways on which the cross slide is mounted and can be moved by means of a feed screw that is controlled by a small hand-wheel and a graduated dial . Through the cross slide a means is provided for moving the lathe tool in the direction normal to the axis of rotation of the work . On most lathes the tool post actually is mounted on a compound rest . This consists of a base , which is mounted on the cross slide so that it can be pivoted about a vertical axis , and an upper casting . The upper casting is mounted on ways on this base so that it can be moved back and forth and controlled by means of a shout lead screw operated by a hand-wheel and a calibrated dial . Manual and powered motion for the carriage , and powered motion for the cross slide , is provided by mechanisms within the apron , attached to the front of the carriage . Manual movement of the carriage along the bed is effected by turning a hand-wheel on the front of the apron , which is geared to a pinion on the back side . This pinion engages a rack that is attached beneath the upper front edge of the bed in an inverted position . To impart powered movement to the carriage and cross slide , a rotating feed rod is provided . The feed rod , which contains a keyway throughout most of its length , passes through the two reversing bevel pinions and is keyed to them . Either pinion can be brought into mesh with a mating bevel gear by means of the reversing lever on the front of the apron and thus provide “forward” or “reverse” power to the carriage . Suitable clutches connect either the rack pinion or the cross-slide screw to provide longitudinal motion of the carriage or transverse motion of cross slide . For cutting threads , a second means of longitudinal drive is provided by a lead screw . Whereas motion of the carriage when driven by the feed-rod mechanism takes place through a friction clutch in which slippage is possible , motion through the lead screw is by a direct , mechanical connection between the apron and the lead screw . This is achieved by a split nut . By means of a clamping lever on the front of the apron , the split nut can be closed around the lead screw . With the spit nut closed , the carriage is moved along the lead screw by direct drive without possibility of slippage . Modern lathes have a quick-change gear box . The input end of this gear box is driven from the lathe spindle by means of suitable gearing . The output end of the gear box is connected to the feed rod and lead screw . Thus , through this gear train , leading from the spindle to the quick-charge gear box , thence to the lead screw and feed rod ,and them to the carriage , the cutting tool can be made to move a specific distances , either longitudinally or transversely , for each revolution of the spindle . A typical lathe provides , through the feed rod , forty-eight feeds ranging from 0.0012 inch to 0.118 inch per revolution of the spindle , and , through the lead screw , leads for cutting forty-eight different threads from 1.5 to 92 per inch . On some older and some cheaper lathes , one or two gears in the train between the spindle and the change gear box must be changed in order to obtain a full range of threads and feeds .