外文翻译--机械专业机床基础

机床基础许多情况下，初步进行成型加工出来的工件必须在尺寸和表面光洁度方面进一步精整，以满足它们的设计技术要求。为了满足精密的公差，需要从工件上去掉小量材料。通常机床就是用于这种加工的设备。在美国，材料切削业是一个很大的企业费用每年超过36109 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术等级评定工作都跟机械加工工业有某些关系，或者通过买卖 设计或者机 作或在有关工业企业 加工， ， 于工程 业 来 ，在的 计 一 去 材料切削和机床， 是个 方 。机床通过切削工 去 工作成型以 所需的尺寸 了 。机床通过 基础 件的作用，以关系方currency1 “工 和工件，基fifl件下 床， 机。这是一个”要fl件，fl件为” 等 一个基础和 ，在作用下，它必须 和动 小。 和 。机床fl件 的动，通常是在精的 面 下 运动来 。 ”和 。 是 一个 的， 的 必须在机床 精的度 定， 是 精密的”和 来 。动力装 。动机是为机床所 用的动力装 。通过 个机的 定 ， 和 动装 。动 机 。 机 是个通用术，用来表机械 动或动机 的，这些机 定的 和 性 关联。加工工艺有两个”要组成fl分 粗加工工艺。粗加工，金属切除率高， 往往切削力也大，但所要求的尺寸精度低。精加工工艺。精加工，金属切除率低， 往往切削力也小，但所要求的尺寸精度和表面光洁度高。由 可见，静荷和动荷，例由不平衡的砂 引起的动荷，在精加工比粗加工 有着更为重要的意义。任何加工过程所获得的精度通常受 由于力的作用引起 的量的影响。机床座一般是用铸铁造的，然 有些也可用铸钢或 碳钢来造。选用铸铁是 为它便宜，刚性 ，受 强度高，并 有 弱机床 作 产 的动的力。为了避免床铸件硕大断面，精心地设计筋条 以便 大的抗弯曲和抗扭 应力的力。筋条的两种基fi类型是型结 和片状斜currency1撑。型结 便于 产，壁上有孔口便于 型芯定 和取出。片状斜currency1撑筋条有较大的抗扭刚度亦 截面上的碎屑掉落。它常常用于 床床。机床的 和是currency1撑和引彼 运动的零fl件，通常是改刀 于工件的 。运动一般以 运动的方，但也有 是 动，例 应于工件的螺纹上的螺 方向 万螺纹磨床上的砂 头 动一个 度。 件的基fi的几何结状是平的 V型槽 燕尾槽和圆柱的。这些 件可根据用途，以 种方分别 用或结 用。 的特性下1 运动精。于 是要按 动的，这 必定是由两个垂 的平面成 必定不存在 动。机床 的 度公差是每米00.02毫米在水平面上这个公差可以进行处理，以 得凸表面，这样就抵消 下凹的作用。调整 。为了便于装配 维护精度和在 磨损 便于动 件 的 动 ，有 在 装 条，这 条 条 。通常 条用 过 孔的 头螺 currency1 ， 用平头螺 调整 用 螺 上。 。 可用以下两种装 进行 1 ，通过 或 进行。这是一种 于运动 度低 不 的方 。2 ，例通过计量 和管 。用这种方 引 两表面 的 必定是很的，的是避免 起 。 表面currency1面平 ， 就 “出 表面。 在 fi上， 表面是用凹面砂 的fl进行磨削或进行。两种工艺都可产 小的表面凹，它就成为存 凹，配 的零件就不处处 起 分，这样 定 。 护。为了维护 处于 状，以下条件必须满足1 必须”面，碎屑进 。 有某一状的 是所 的。在这种 ，是不可进 的，例是 V的 ， 就不可存碎屑在 上。2 必须存 。在垂 或斜的 面上 用的 要有性， 很重要。为了这种 用的 出多种有用的 。 的性也要护，以免 切削 。3 必须用护来意”的损。一 机床 个”要1 的currency1工件或者刀和刀 2 在工件和刀 运动3 一定的刀和切削 度 。以去除切屑来加工金属的机床一般分为大类 用 刀 切削的机床 用多刀 切削的机床 用 机刀 切削的机床磨削和 用于特 的机床。fi上， 用 刀 切削的机床包括1 通 床2 床3 床 动 床 多 动 床6 头 和 床 床。用多刀 切削的机床包括1 床2 床3 床 床 切 机床。用 机刀 切削的机床包括1 ”圆磨床2 心磨床3平面磨床。用特 的方 进行金属切削的机床包括1 削机床2 花加工机床3 超加工机床。 床是 于 动的工件 着刀 来切去金属材料，以产 ”圆柱面或 圆柱面或 表面的。它 面切削也 用于加工平面。在 面切削加工 ，工件 ， 刀 作垂 于 方向动。通 床是基fi的 削机床，从这出 ， 出 削机床。 动机装在床基础上并通过 结 来 动”，以 每分2 1 00 的 。”是一根 的 心，装在重型 ， 用来装 动 花 ，以便 定的运动 工作。 动 可 螺纹 凸 机 或 一个螺纹和 定在”上。床的床是铸铁件。它 精的磨削的 动表面 ， 上有 床 是 型的铸件， 刀 就装在 上的刀上。 装在 面，并装有动刀 的 机 ， 着 或 过 以 所希 的刀 的运动。 上面的小刀 刀“ 所要求的任意 度。为 刀 作 2性运动，在小刀上装有 和丝。以 和 小刀垂 于 床 动的丝来 向进给。 的 系可为 沿着 和 跨 动力进给。进给 运动给 并刀 于工件的运动 度。典型的 床进给 是”每 从0.002 0.160英寸，大 有 0级 。由于进给的动运动是由” 动的， 进给量 ” 度有关。进给 动机 也用于加工螺纹并加工每英寸 22 扣螺纹。进给和 床 的 结是光和丝。许多 床造商 这两结为一， 际上 就以精的开currency1 机 的费用。进给光用于 刀 的运动，它 于精的工件和 的表面光洁度是很重要的。螺纹丝用于 精的螺纹程，这 于螺纹切削是必需的。光是通过摩擦 来 动的， 样在刀 切削超情况下够打 护。这一全装 不装在丝上， 为螺纹加工是不允许打 的。由于螺纹全深很难一次刀加工完成， 装设一螺纹指示 作为下几次刀加工 重新 刀用。床装有尾座，它 有一精的，有一 孔，以便装 头 “ 铰刀和 床顶针。尾座可以沿着 床 动以 应工件的不同 度以及加工 体或 表面。床基fi上是 有某种附加特性的通 床， 作为半 动加工和 人工 作误差的机。 床的 设有T槽以便在 床 两 装“刀装 ，当 ，要正地装设刀 以便进行切削。 也装设有 动停机装 以便刀 行程和 的切削的再 产。 床的尾座是六 结 ，在六 头 可以装六 刀 。虽然装刀和加工准备要花大量 ，但 床一次装刀以 需熟练工人就可以 地重复地 作加工， 刀 钝并需更换为。这样 床仅就 产工作在济上是可行的 理的，于 ，根据所造零件的数量，为加工准备需要花一定数量的 是 理的， 可非议的。跟踪 重复加工 床装有一个重复装 以 动 刀 纵向和 向的进给运动并可以一次或两次刀就 产出所需状和尺寸的光洁零件。 动 床 用一个立 和两个 向 。工件通过机床”孔 卡 ， 刀 是 凸 来 动 作。多 动 床装有 五 六或八根”，在每根” 装一个工件。 ” 着一根 心来 换 。以”刀 去近 ”。每根” 上都装有一侧向可以独立 作的刀 。由于 刀 都是 凸 作的， 加工准备可花几天 ， 至 需要 000件的批量 产 ，它的 用才是 理的。这种机床的”要优就是所有的刀 同 工作， 一个工人可以看管几fl机床。 于 简 的零件 言，多 动 床可以以每五秒一件的 度 产加工出成品来。头 床 用装在 枕一 的刀“上的 刀 。切削加工通常是以向 的行程来进行。刀 抬刀稍稍抬，以避免刀 过工件表面的严重 。在返 行程 ，刀 下面进给机 工件进给为下一次切削作准备。立床装有 头 的 作机 ，亦用作装currency1工件的工作 。工作 可在 枕垂 的两个方向上动。利用刀 块来切 深度并进行 动进给。它也可以在 向垂 的 侧 90度 ， 样就允许 于工作 表面成一个 度，再 刀 进给。头 床有两种类型的 动机 修正过的惠快 机 和 动机 。 3于惠机 ，动机 动大 ，大 动曲臂，通过可调节的曲柄销来行程 度。当大 ，摇臂受力 往复运动并 运动递给 头 枕。在 头 的动机，仅仅是用来 动 。 头 的残余运动是 的流向来。为机械所 动的 头 的切削行程只利用了大 的220度。 返 行程利用了1 0度。这就 成切削行程 返 行程 比为1.6比1。 度图表明切削行程 刀 的 度决不是 定的， 头 的 度图表明 于大多数切削行程，切削 度是 定的。 头 增加了一个优，切削 度可 级 。这类机床的”要缺是在 枕程的终 缺乏定的。 就可允许有千分 几英寸的行程 度误差。得由 型模 来再 廓成为可的双套装 是有效的。 模用来跟 配 。种规格和类型的立 床或 摇 床是很有用的，并配以有足够宽 的” 级， 动进给以满足大多数工业的需要。典型 床的 级 是从每分 6 每分202 。 头进给 度为”每 从0.002英寸 每 0.020英寸。摇臂 床是用来 削 种很笨重以至于不便搬动的工件。有 度调节和进给调节机 的” 装在摇臂上。通过 臂 立柱的 动同”组件沿摇臂的动结 ，可 ”和 头 准机床可 的任何上。于太大 不便于在 床工作 上的工件，可 ”组件摆 地面上方并摆 在机床旁边地上的工件上方。通摇臂 床只 ”垂 运动， 万摇臂 床允许” 垂 于摇臂的 ， 摇臂可 着水平 ，这样就可以在任何 度方 下 削。多 床 有一个或多个通过万向头和可伸缩的花来 动”的装 。所有的”通常都由同一fl动机 动并同 进给以便 削出所要求的孔数。在大多数 床 ，每根”都 装“在一可调节 ，以便它 于 ”动。邻”所 准的区域fl分交叠以便 床可在 任何 孔削工艺是以 的刀 来切去金属。它包括从工件表面上切去金属，扩大孔眼和成切削，例螺纹加工和 加工。升降 的床 ，立柱是为 零件的”要currency1乘 件，并包括装有 动机 ”和刀 的基础件。刀 装于”的刀上，并 通过悬臂 的 currency1 在 ” 。升降 用燕尾槽装在立柱上，鞍座用燕尾槽 升降 上， 工作 则 座上。这样，升降 的 立 立柱 床 于刀 的个运动。 工作 着鞍座上的垂 ，就可以 个运动。床 定的床设计的 有比升降 和立柱的更 的刚性。这工作 装在机床基础 上，为了 重大切削力，工作 有 的刚性， 是必要的， 仅允许 工作 作纵向运动。垂 运动 动整个刀头获得。型床的特是刀 和跟踪元件的 运动的 调或同步。在典型 型床，跟踪指针跟 模型的状 廓， 刀头重复着 型运动。4Fundamentals of Machine ToolsIn many cases products from the primary forming processes must undergo further refinements in size and surface finish to meet their design specifications.To meet such precise tolerance the removal of small amounts of material is needed.Usually machine tools are used for such operation.In the United States material removal is a big businessin excess of 36109 per year,including material,labor,overhead,and machine-tools shipments,is spent.Since 60 percent of the machanical and industrial engineering and technology graduate 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 provide 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 distorion 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 surface(the slideways).(c)Spindles and Bearings.Angular displacement 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 for machine tools.By suitably positioning individual motors,belt and gear transmissions and 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 and surface finish relatively high.It follows that static loads and dynamic loads,such as result from an unbalanced grindingwheel,are rmore significant in finishing operations than in roughing operations.The degree of precision achieved in any machining process will usually be influenced by the magnitude of the deflections,which occur as a result of the force 5acting.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 resistance to bending and torsional stresses.Two basic types of ribbing are box and diagonal.The box formation is convenient to produce,apertures in walls permitting the positioning and extraction of cores.Diagonal ribbing provides greater 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 move relative to each other,usually changing the position of the tool relative to the workpiece.The movement genenally takes the forms of translation in a straight line,but is sometimes angulai rotation,e.g. tilting the wheel-head of a universal thread-grinding machine to an angle corresponding with the 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 ways according to the applications.Features of slideways 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 effect of “sag”of the slideway.(b)Means of Adjustment.To facilitate assembly,maintain accuracy and eliminate “play” between slideing members after wear has taken place,a strip is something inserted in the slides.This is called a gib-strip.Usually,the grib is retained by socket-head screw passing through elongated slots；and is adjusted by grub-screws secured by lock nuts.(c)Lubrication.Slideways may be lubricated by either of the following systems:1)Intermittently through grease or oil nipples,a method suitable where movements are infrequent and speed low.2)Continuously,e.g. by pumping through a metering value 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 slide “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 depresssions,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:1)Ingress of foreign matter,e.g. swarf,must be prevented.Where this is no possible,it is desirable to have a form of slideway,which does not retain swarf,e.g. the inverted vee.62)Lubricating oil must be retained.The adhensive 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 guards.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 random-point tools(abrasive),and those that 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-single 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)gear-cutting machines.Machines using random-point cutting tools include:1)cylindrical grinder, 2)centreless grinders, 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.It is also commonly used for the production of flat surfaces by faing,in which the workpiece is rotated while 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 from 25 to 1500 rpm.The spindle is a sturdy hollow shaft,mounted between heavy-duty bearings,with the forward end used for mounting a drive plate to impart positive motion to the workpiece.The drive plate may be fastened to the spindle by threads,by a cam lock mechanism,or by a thread collar and key.The lathe bed is cast iron and provides accurately ground sliding surfaces(way)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 provides for rotation of the tool holder through any desired angle.A hand wheel and feed screw are 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 7provides from 4 to 224 threads per in.The connecting shaft between the feed box and the lathe apron are the feed rod and the lead screw.Many lathe manufacturers combine these two rods in one,a practice that reduces the cost of the machine at the expense of accuracy.The feed rod is used to provide tool motion essential for accurate workpiece and good surface finishes.The lead screw is used to provide the accurate lead necessary for the thread cutting.The feed rod is driven through a friction clutch that allows slippage in case the tool is overloaded.This safety device is not provided in the lead screw,since thread cutting cannot tolerate slippage.Since the full depth of the thread is seldom cut in one pass,a chasing dial is provided to realign the tool for subsequent passes.The lathe tailtock is fitted with an accurate spindle that has a tapered hole for mounting drills,drill chucks,reamers,and lathe centers.The tailstock can be moved along the lathe ways to accommodate various lengths of workpieces as well as to advance a tool into contact with the worpiece.The tailstock can be offset relative to the lathe ways to cut tapers or conical surfaces.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 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 of hexagonal design,in which six tools can be mounted.Althogh a large amount of time is consumed in setting up the tools and stops for operation,the turret lathe,once set,can continue to duplicate operations with a minimum of operator skill until the tools become dulled and need replacing.Thus,the turret lathe is economically feasible only for production work,where the amount of time necessary to prepare the machine for operation is justifiable in terms of the number of part to be made.Tracing and duplicating lathes are equipped with a duplicating device to automatically control the longitudinal and cross feed motions of the single-point cutting tool and provide a finished part of required shape and size in one or two passes of the tools.The single-spindle automatic lathe uses a vertical turret as well as two cross slids.The work is fed through the machine spindle into the chuck,and the tools are operated automatically by cams.The multispindle automatic lathe is provided with four,five,six,or eight spindles,with one workpiece mounted in each spindle.The spindles index around a central shaft,with the main tools slide accessible to all spindles.Each spindle position is provided with a side tool-slide operated independently.Since all of the slides are operated by cams,the preparation of this machine may take several days,and a production run of at least 5000 parts is needed to justify its use.The principal advantage of this machine is that all tools work simultaneously,and one operator can handle several machines.For relatively simple parts,multispindle automatic lathes can turn out finished products at the rate of 1 every 5 sec.A shapers utilizes a single-point tool in a tool holder mounted on the end of the 8ram.Cutting is generally done on the forward stroke.The tool is lifted slightly by the clapper box to prevent excessive drag across the work,which is fed under the tool during the return stroke in preparation for the next cut.The column house the operating mechanisms of the shaper and also serves as a mounting unit for the work-supporting table.The table can be moved in two directions mutually perpendicular to the ram.The tool slide is used to control the depth of the cut and is manually fed.It can be rotated through 90 deg. On either side of its normal vertical position,which allows feeding the tool at an angle to the surface of the table.Two types of the driving mechanisms for shapers are a modified Whitworth quick-return mechanism and a hydraulic drive.For the Whitworth mechanism,the motor drives the bull gear,which drives a crank arm with an adjustable crank pin to control the length of the stroke.As the bull gear rotates,the rocker arm is forced to reciprocate,imparting this motion to the shaper ram.The motor on a hydraulic shaper is used only to drive the hydraulic pump.The remainder of the shaper motions are controlled by the direction of the flow of the hydraulic oil.The cutting stroke of the mechanically driven shaper uses 220 deg. of rotation of the bull gear,while the return stroke uses 140 deg.This gives a cutting stroke to return stroke ratio of 1.6 to 1.The velocity diagram shows that the velocity of the tool during the cutting stroke is never constant,while the velocity diagram for a hydraulic shaper shows that for most of the cutting stroke the cutting speed is constant.The hydraulic shaper has an added advantage of infinitely variable cutting speeds.The principal disadvantage of this type of machine is the lack of a definite limit at the end of the ram stroke,which may allow a few thousandths of an inch variation in stroke length.A duplicating device that makes possible the reproduction of contours from a sheet-metal template is available.The sheet metal template is used in conjunction with hydraulic control.Upright drilling machines or drill presses are available in a variety of sizes and types,and are equipped with a sufficient range of spindle speeds and automatic feeds to fit the needs of most industries.Speed ranges on a typical machine are from 76 to 2025 rpm.,with drill feed from 0.002 to 0.20 in. per revolution of the spindle.Radial drilling machines are used to drill workpieces that are too large or cumbersome to conveniently move.The spindle with the speed and feed changing mechanism is mounted on the radial arm；by combing the movement of the radial arm around column and the movement of the spindle assembly along the arm,it is possible to align the spindle and the drill to any position within reach of the machine.For work that is too large to conveniently support on the base,the spindle assembly can be swung out over the floor and the workpiece set on the floor beside