機床基礎許多情況下，初步進行成型加工出來的工件必須在尺寸和表面光潔度方面進一步精整，以滿足它們的設計技術要求。為了滿足精密的公差，需要從工件上去掉小量材料。通常機床就是用于這種加工的設備。在美國，材料切削業(yè)是一個很大的企業(yè)費用每年超過36109 美元，包括材料，勞動力，管理費，機床裝運費等所花的費用。由于60%機械和工業(yè)工程以及技術等級評定工作都跟機械加工工業(yè)有某些關系，或者通過買賣 設計或者機 作或在有關工業(yè)企業(yè) 加工， ， 于工程 業(yè) 來 ，在的 計 一 去 材料切削和機床， 是個 方 。機床通過切削工 去 工作成型以 所需的尺寸 了 。機床通過 基礎 件的作用，以關系方currency1 “工 和工件，基fifl件下 床， 機。這是一個”要fl件，fl件為” 等 一個基礎和 ，在作用下，它必須 和動 小。 和 。機床fl件 的動，通常是在精的 面 下 運動來 。 ”和 。 是 一個 的， 的 必須在機床 精的度 定， 是 精密的”和 來 。動力裝 。動機是為機床所 用的動力裝 。通過 個機的 定 ， 和 動裝 。動 機 。 機 是個通用術，用來表機械 動或動機 的，這些機 定的 和 性 關聯(lián)。加工工藝有兩個”要組成fl分 粗加工工藝。粗加工，金屬切除率高， 往往切削力也大，但所要求的尺寸精度低。精加工工藝。精加工，金屬切除率低， 往往切削力也小，但所要求的尺寸精度和表面光潔度高。由 可見，靜荷和動荷，例由不平衡的砂 引起的動荷，在精加工比粗加工 有著更為重要的意義。任何加工過程所獲得的精度通常受 由于力的作用引起 的量的影響。機床座一般是用鑄鐵造的，然 有些也可用鑄鋼或 碳鋼來造。選用鑄鐵是 為它便宜，剛性 ，受 強度高，并 有 弱機床 作 產(chǎn) 的動的力。為了避免床鑄件碩大斷面，精心地設計筋條 以便 大的抗彎曲和抗扭 應力的力。筋條的兩種基fi類型是型結 和片狀斜currency1撐。型結 便于 產(chǎn)，壁上有孔口便于 型芯定 和取出。片狀斜currency1撐筋條有較大的抗扭剛度亦 截面上的碎屑掉落。它常常用于 床床。機床的 和是currency1撐和引彼 運動的零fl件，通常是改刀 于工件的 。運動一般以 運動的方，但也有 是 動，例 應于工件的螺紋上的螺 方向 萬螺紋磨床上的砂 頭 動一個 度。 件的基fi的幾何結狀是平的 V型槽 燕尾槽和圓柱的。這些 件可根據(jù)用途，以 種方分別 用或結 用。 的特性下1 運動精。于 是要按 動的，這 必定是由兩個垂 的平面成 必定不存在 動。機床 的 度公差是每米00.02毫米在水平面上這個公差可以進行處理，以 得凸表面，這樣就抵消 下凹的作用。調(diào)整 。為了便于裝配 維護精度和在 磨損 便于動 件 的 動 ，有 在 裝 條，這 條 條 。通常 條用 過 孔的 頭螺 currency1 ， 用平頭螺 調(diào)整 用 螺 上。 。 可用以下兩種裝 進行 1 ，通過 或 進行。這是一種 于運動 度低 不 的方 。2 ，例通過計量 和管 。用這種方 引 兩表面 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進行磨削或進行。兩種工藝都可產(chǎn) 小的表面凹，它就成為存 凹，配 的零件就不處處 起 分，這樣 定 。 護。為了維護 處于 狀，以下條件必須滿足1 必須”面，碎屑進 。 有某一狀的 是所 的。在這種 ，是不可進 的，例是 V的 ， 就不可存碎屑在 上。2 必須存 。在垂 或斜的 面上 用的 要有性， 很重要。為了這種 用的 出多種有用的 。 的性也要護，以免 切削 。3 必須用護來意”的損。一 機床 個”要1 的currency1工件或者刀和刀 2 在工件和刀 運動3 一定的刀和切削 度 。以去除切屑來加工金屬的機床一般分為大類 用 刀 切削的機床 用多刀 切削的機床 用 機刀 切削的機床磨削和 用于特 的機床。fi上， 用 刀 切削的機床包括1 通 床2 床3 床 動 床 多 動 床6 頭 和 床 床。用多刀 切削的機床包括1 床2 床3 床 床 切 機床。用 機刀 切削的機床包括1 ”圓磨床2 心磨床3平面磨床。用特 的方 進行金屬切削的機床包括1 削機床2 花加工機床3 超加工機床。 床是 于 動的工件 著刀 來切去金屬材料，以產(chǎn) ”圓柱面或 圓柱面或 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 方向動。通 床是基fi的 削機床，從這出 ， 出 削機床。 動機裝在床基礎上并通過 結 來 動”，以 每分2 1 00 的 。”是一根 的 心，裝在重型 ， 用來裝 動 花 ，以便 定的運動 工作。 動 可 螺紋 凸 機 或 一個螺紋和 定在”上。床的床是鑄鐵件。它 精的磨削的 動表面 ， 上有 床 是 型的鑄件， 刀 就裝在 上的刀上。 裝在 面，并裝有動刀 的 機 ， 著 或 過 以 所希 的刀 的運動。 上面的小刀 刀“ 所要求的任意 度。為 刀 作 2性運動，在小刀上裝有 和絲。以 和 小刀垂 于 床 動的絲來 向進給。 的 系可為 沿著 和 跨 動力進給。進給 運動給 并刀 于工件的運動 度。典型的 床進給 是”每 從0.002 0.160英寸，大 有 0級 。由于進給的動運動是由” 動的， 進給量 ” 度有關。進給 動機 也用于加工螺紋并加工每英寸 22 扣螺紋。進給和 床 的 結是光和絲。許多 床造商 這兩結為一， 際上 就以精的開currency1 機 的費用。進給光用于 刀 的運動，它 于精的工件和 的表面光潔度是很重要的。螺紋絲用于 精的螺紋程，這 于螺紋切削是必需的。光是通過摩擦 來 動的， 樣在刀 切削超情況下夠打 護。這一全裝 不裝在絲上， 為螺紋加工是不允許打 的。由于螺紋全深很難一次刀加工完成， 裝設一螺紋指示 作為下幾次刀加工 重新 刀用。床裝有尾座，它 有一精的，有一 孔，以便裝 頭 “ 鉸刀和 床頂針。尾座可以沿著 床 動以 應工件的不同 度以及加工 體或 表面。床基fi上是 有某種附加特性的通 床， 作為半 動加工和 人工 作誤差的機。 床的 設有T槽以便在 床 兩 裝“刀裝 ，當 ，要正地裝設刀 以便進行切削。 也裝設有 動停機裝 以便刀 行程和 的切削的再 產(chǎn)。 床的尾座是六 結 ，在六 頭 可以裝六 刀 。雖然裝刀和加工準備要花大量 ，但 床一次裝刀以 需熟練工人就可以 地重復地 作加工， 刀 鈍并需更換為。這樣 床僅就 產(chǎn)工作在濟上是可行的 理的，于 ，根據(jù)所造零件的數(shù)量，為加工準備需要花一定數(shù)量的 是 理的， 可非議的。跟蹤 重復加工 床裝有一個重復裝 以 動 刀 縱向和 向的進給運動并可以一次或兩次刀就 產(chǎn)出所需狀和尺寸的光潔零件。 動 床 用一個立 和兩個 向 。工件通過機床”孔 卡 ， 刀 是 凸 來 動 作。多 動 床裝有 五 六或八根”，在每根” 裝一個工件。 ” 著一根 心來 換 。以”刀 去近 ”。每根” 上都裝有一側向可以獨立 作的刀 。由于 刀 都是 凸 作的， 加工準備可花幾天 ， 至 需要 000件的批量 產(chǎn) ，它的 用才是 理的。這種機床的”要優(yōu)就是所有的刀 同 工作， 一個工人可以看管幾fl機床。 于 簡 的零件 言，多 動 床可以以每五秒一件的 度 產(chǎn)加工出成品來。頭 床 用裝在 枕一 的刀“上的 刀 。切削加工通常是以向 的行程來進行。刀 抬刀稍稍抬，以避免刀 過工件表面的嚴重 。在返 行程 ，刀 下面進給機 工件進給為下一次切削作準備。立床裝有 頭 的 作機 ，亦用作裝currency1工件的工作 。工作 可在 枕垂 的兩個方向上動。利用刀 塊來切 深度并進行 動進給。它也可以在 向垂 的 側 90度 ， 樣就允許 于工作 表面成一個 度，再 刀 進給。頭 床有兩種類型的 動機 修正過的惠快 機 和 動機 。 3于惠機 ，動機 動大 ，大 動曲臂，通過可調(diào)節(jié)的曲柄銷來行程 度。當大 ，搖臂受力 往復運動并 運動遞給 頭 枕。在 頭 的動機，僅僅是用來 動 。 頭 的殘余運動是 的流向來。為機械所 動的 頭 的切削行程只利用了大 的220度。 返 行程利用了1 0度。這就 成切削行程 返 行程 比為1.6比1。 度圖表明切削行程 刀 的 度決不是 定的， 頭 的 度圖表明 于大多數(shù)切削行程，切削 度是 定的。 頭 增加了一個優(yōu)，切削 度可 級 。這類機床的”要缺是在 枕程的終 缺乏定的。 就可允許有千分 幾英寸的行程 度誤差。得由 型模 來再 廓成為可的雙套裝 是有效的。 模用來跟 配 。種規(guī)格和類型的立 床或 搖 床是很有用的，并配以有足夠寬 的” 級， 動進給以滿足大多數(shù)工業(yè)的需要。典型 床的 級 是從每分 6 每分202 。 頭進給 度為”每 從0.002英寸 每 0.020英寸。搖臂 床是用來 削 種很笨重以至于不便搬動的工件。有 度調(diào)節(jié)和進給調(diào)節(jié)機 的” 裝在搖臂上。通過 臂 立柱的 動同”組件沿搖臂的動結 ，可 ”和 頭 準機床可 的任何上。于太大 不便于在 床工作 上的工件，可 ”組件擺 地面上方并擺 在機床旁邊地上的工件上方。通搖臂 床只 ”垂 運動， 萬搖臂 床允許” 垂 于搖臂的 ， 搖臂可 著水平 ，這樣就可以在任何 度方 下 削。多 床 有一個或多個通過萬向頭和可伸縮的花來 動”的裝 。所有的”通常都由同一fl動機 動并同 進給以便 削出所要求的孔數(shù)。在大多數(shù) 床 ，每根”都 裝“在一可調(diào)節(jié) ，以便它 于 ”動。鄰”所 準的區(qū)域fl分交疊以便 床可在 任何 孔削工藝是以 的刀 來切去金屬。它包括從工件表面上切去金屬，擴大孔眼和成切削，例螺紋加工和 加工。升降 的床 ，立柱是為 零件的”要currency1乘 件，并包括裝有 動機 ”和刀 的基礎件。刀 裝于”的刀上，并 通過懸臂 的 currency1 在 ” 。升降 用燕尾槽裝在立柱上，鞍座用燕尾槽 升降 上， 工作 則 座上。這樣，升降 的 立 立柱 床 于刀 的個運動。 工作 著鞍座上的垂 ，就可以 個運動。床 定的床設計的 有比升降 和立柱的更 的剛性。這工作 裝在機床基礎 上，為了 重大切削力，工作 有 的剛性， 是必要的， 僅允許 工作 作縱向運動。垂 運動 動整個刀頭獲得。型床的特是刀 和跟蹤元件的 運動的 調(diào)或同步。在典型 型床，跟蹤指針跟 模型的狀 廓， 刀頭重復著 型運動。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