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南京理工大學泰州科技學院
畢業(yè)設計(論文)外文資料翻譯
系 部： 機械工程系
專 業(yè)： 機械工程及自動化
姓 名： 陳游
學 號： 05010113
(用外文寫)
外文出處： http://www.mapeng.net
附 件： 1.外文資料翻譯譯文；2.外文原文。
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附件1：外文資料翻譯譯文
車床與銑削加工
車床
用與車外圓、端面和鏜孔等加工的機床叫車床。車削很少在其他種類的機床上進行，某些機床不能像車床那樣方便地進行車削加工。由于車床除了用于車外圓外還能用于鏜孔、車端面、鉆孔和鉸孔，車床的多功能性可以使工件在一次定位安裝中完成多種加工。這就是在生產中普遍使用各種車床比其他種類的機床都要多的原因。
很早就已經有了車床?，F(xiàn)代車床可以追溯到大約17世紀，那時亨利·莫德斯利發(fā)明了一種具有絲杠的車床。這種車床可以控制工具的機械進給。聰明的英國人還發(fā)明了一種把主軸和絲杠相連接的變速裝置，這樣就可以切削螺紋。
車床的主要部件：床身、主軸箱組件、尾架組件、拖板組件、變速齒輪箱、絲杠和光杠床身是車床的基礎件。它通常是由經過正火處理的灰鑄鐵或者球墨鑄鐵制成，它是一個堅固的剛性框架，所有其他主要部件都安裝在床身上。通常在床身上面有內外兩組平行的導軌。一些制造廠生產的四個條導軌都采用倒“V”形，而另一些制造廠則將倒“V”形導軌和平面導軌相結合。由于其他的部件要安裝在導軌上或在導軌上移動，導軌要經過精密加工，以保證其裝配精度。同樣地，在操作中應該小心，以避免損傷導軌。導軌上的任何誤差，常常會使整個機床的精度破壞。大多數現(xiàn)代車床的導軌要進行表面淬火處理，以減小磨損和擦傷，具有更大的耐磨性。主軸箱安裝在床身一端內導軌的固定位置上。它提供動力，使工件在各種速度下旋轉。它基本上由一個安裝在精密軸承中的空心主軸和一系列變速齒輪，通過變速齒輪，主軸可以在許多種轉速下旋轉。大多數車床有8—18種轉速，一般按等比級數排列。在現(xiàn)代車床上只需扳動2～4個手柄，就能得到全部擋位的轉速。目前發(fā)展的趨勢是通過電氣的或機械的裝置進行無級變速。
由于車床的精度在很大程度上取決于主軸，因此主軸的結構尺寸較大，通常安裝在緊密配合的重型圓錐滾子軸承或球軸承中。主軸中有一個貫穿全長的通孔。主軸孔的大小是車床的一個重要尺寸，因為當工件通過主軸孔供料時，它確定了能夠加工棒料毛坯的最大外徑尺寸。
主軸的內端從主軸箱中凸出，其上可以安裝多種卡盤、花盤和擋塊。而小型的車床常帶有螺紋截面供安裝卡盤之用。很多大車床使用偏心夾或鍵動圓錐軸頭。這些附件組成了一個大直徑的圓錐體，以保證對卡盤進行精確地裝配，并且不用旋轉這些笨重的器件就可以鎖定或松開卡盤和花盤。
主軸由電動機經V帶或無聲鏈裝置提供動力。大多數現(xiàn)代車床都裝有5—15馬力的電動機，為硬質合金和金屬陶瓷合金刀具提供足夠的動力，進行高速切削。
尾座組件主要由三部分組成。底座與床身的內側導軌配合，并可以在導軌上做縱向移動，底座上有一個可以使整個尾座組件夾緊的裝置。尾座安裝在底座上，可以沿鍵槽在底座上橫向移動，使尾座與主軸箱中的主軸對正并為切削圓錐體提供方便。尾座組件的第三部分是尾座套筒，它是一個直徑通常在2～3英寸之間的鋼制空心圓柱軸。通過手輪和螺桿，尾座套筒可以在尾座體中縱向移入和移出幾英寸?；顒犹淄驳拈_口一端具有莫氏錐度，可以用于安裝頂尖或其他刀具。通常在活動套筒的外表面刻有幾英寸長的刻度，以控制尾座的前后移動。鎖定裝置可以使套筒在所需要的位置上夾緊。
拖板組件用于安裝和移動切削工具。拖板是一個相對平滑釣H形鑄件，安裝在床身外側導軌上，并可在上面移動。大拖板上有橫向導軌，使橫向拖板可以安裝在上面，并通過絲杠使其運動，絲杠由一個小手柄和刻度盤控制。橫拖板可以帶動刀具垂直于工件的旋轉軸線切削。
銑削加工
銑削是機械加工的一個基礎方法。在這一加工過程中，當工件沿垂直于旋轉刀具軸線方向進給時，在工件上去除切屑從而逐漸地銑出表面。有時候，工件是固定的，而刀具處于進給狀態(tài)。在大多數情況下，使用多齒刀具，金屬切削量大，只需一次銑削就可以獲得所期望的表面。在銑削加工中使用的刀具稱做銑刀。它通常是一個繞軸線旋轉并且周邊帶有同間距齒的圓柱體，銑刀齒間歇性接觸并切削工件。在某些情況下，銑刀上的刀齒會高出圓柱體的一端或兩端。
由于銑削切削金屬速度很快，并且能產生良好的表面光潔度，故特別適合大規(guī)模生產加工。為了實現(xiàn)這一目的，已經制造出了質量一流的銑床。并且在機修車間和工具模具加工中也已經廣泛地使用了非常精確的多功能通用的銑床。車間里擁有一臺銑床和一臺普通車床就能加工出具有適合尺寸的各種產品。
銑削操作類型：銑削操作可以分成兩大種類，每一類又有多種類型。
1．圓周銑削在圓周銑削中，使用的銑刀刀齒固定在刀體的圓周面上，工件銑削表面與旋轉刀具軸線平行，從而加工表面。使用這種方法可以加工出平面和成型表面，加工中表面橫截面與刀具的軸向外輪廓相一致。這種加工過程常被稱為平面銑削。
2．端面銑削銑削平面與刀具的軸線垂直，被加工平面是刀具位于周邊和端面的齒綜合作用形成的。刀具周邊齒完成銑削的主要任務，而端面齒用于精銑。
圓周銑削和端面銑削的基本概念，圓周銑削通常使用臥式銑床，而端銑削則既可在臥式銑床又可以在立式銑床上進行。
銑削面的形成：銑削時可以采用兩種完全不同的方法。應注意的是，在逆向銑削時，銑刀旋轉方向與工件進給方向相反，而在順銑時銑刀旋轉與工件進給方向相同。在逆銑過程中，當銑刀齒剛切人工件時，切屑是非常薄的，然后漸漸增厚，在刀齒離開工件的地方，切屑最厚。在兩種銑削方法中，切屑的形成是不同的，逆銑過程中，刀具有推動使工件從工作臺提升的趨勢，這種作用有助于消除銑床工作臺進給螺桿和螺母間的間隙，從而形成平穩(wěn)的切削。然而，這種作用也有造成工件與夾緊裝置之間的松動的趨勢，這時應施加更大的夾緊力。此外，銑削表面的平整度主要取決于切削刃的鋒利程度。
順銑時，最大切屑厚度產生于靠近刀具與工件接觸點處。由于相對運動把工件拉向銑刀，如果采用順銑法，要消除工作臺進給時螺桿可能產生的松動。因此，對于不能用于順銑的銑床，應不采用順銑方法。因為在銑刀結束切削時，處于切線方向的被切材料發(fā)生屈服，所以與逆銑相比，順銑的被加工表面沒有什么切痕。順銑的另一個優(yōu)勢是切削力趨于將工件壓緊在工作臺上，因此對工件的夾緊力可以小于逆銑。這一優(yōu)勢可以用于銑削較薄的工件或進行強力切削。順銑的弱點是銑刀齒剛一切削每片鐵屑時，刀齒會撞擊工件的表面。如果工件表面堅硬，像鑄件，就會使刀齒迅速地變鈍。
銑刀
銑刀分類有多種方法，一種方法是根據刀具后角將銑刀分為兩大類：
1．仿形銑刀每個刀齒在切削刃的背面磨了一個很小的棱面形成后角，切削刃可以是直線或曲線的。
2．凸輪形后角銑刀每個齒的橫截面在切削刃的背面呈偏心曲線狀，以產生后角。偏心后角的各面與切削刃平行，具有切削刃的相同形狀。這種類型的銑刀僅需磨削齒的前刀面就可以變得鋒利，只要切削刃的外形保持不變，銑刀的另一種分類方法是根據銑刀安裝的方法進行分類。心軸銑刀帶有一個中心孔以使銑刀安裝在心軸上。帶柄銑刀有一錐柄或直柄軸，含錐形軸柄的銑刀可以直接安裝在銑床的主軸上，而直柄軸的銑刀則是夾持在卡盤里。平面銑刀通常用螺栓固定在刀軸的末端上。
根據這種分類方法，通用型的銑刀可分類如下：
心軸銑刀：圓柱形銑刀，角度銑刀，側刃銑刀，嵌齒銑刀，錯齒銑刀，凸輪形后角銑刀，開槽銑刀，高速切削刀。
帶柄銑刀：端面銑刀，T形槽銑刀，整體式銑刀，半圓鍵座銑刀，套式銑刀，高速切削刀，空心銑刀。
銑刀的類型圓柱形銑刀是在圓周上有直的或螺旋形的齒的圓柱形或盤形銑刀。它們可以用來銑削平面，這種銑削稱做平面銑削。螺旋形的銑刀上的每個齒是逐漸地接觸工件，在給定的時間內，一般有多齒進行銑削，這樣可以減少震動，獲得一個較平滑的表面。因此，與直齒銑刀相比，這種類型的銑刀，通常使用得更多。
側刃銑刀的齒除了在圓柱刀體的一端或兩端向徑向延伸之外，與圓柱形銑刀是相似的。側刃銑刀的刀齒既可以是直線的，也可以是螺旋形的，這種銑刀一般較窄小，具有盤形的形狀。在跨式銑削加工中，常常將兩個或更多的側刃銑刀同時相間地安裝在一個刀桿上同步并行切削。
雙聯(lián)槽銑刀是由兩個側刃銑刀組成，但是在銑槽時，作為一組銑刀進行操作。在兩個銑刀之間添加一些薄墊片，以調整之間的間距。
錯齒銑刀是較薄的圓柱形銑刀，刀上有相互交錯的刀齒，相鄰刀齒具有相反的螺旋角。這種銑刀經研磨后僅用于周銑，在每個齒突出的一邊，留有供切屑排出的縫隙。這種類型的銑刀可用于高速切削，在銑削深槽時可以發(fā)揮獨特的作用。
開槽銑刀是一種薄型的圓柱形銑刀，厚度一般為1／32—3／16英寸。這種銑刀的側面呈盤狀，有間隙，可以防止粘連。與圓柱形銑刀相比，這種類型的銑刀每英寸直徑上的齒數更多，通常用于銑削較深的、狹窄的槽，并可用于切割加工。
附件2：外文原文（復印件）
LATHE AND MILLING
The basic machines that are designed primarily to do turning, facing and boring are called lathes. Very little turning is done on other types of machine tools, 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 workpiece. These 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 long long age. Modem lathes date from about 1797, when Henry Maudsley developed one with a lea&crew. It provided controlled, mechanical feed of the tool. This ingenious Englishman also developed a changegear system that could connect the motions of the spindle and lea&crew and thus enable threads to be cut.Lathe Construction. The essential components of a lathe are depicted in the block diagram.
These are the bed, headstock assembly, tailstock assembly, carriage assembly, quick-change gear box, and the lea&crew and feed rod.The bed is the backbone of a lathe. It usually is made of well-normalized or aged gray or nodular cast iron and provides a heavy, rigid frame on which all the other basic components are mounted. Two sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side. Some makers 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 components are mounted and/or move on the ways they must be made with precision to assure 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 modem 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 the 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 provide from eight to eighteen speeds, usually in a geometric ratio, and on modem lathes all the speeds can be obtained merely by moving from two to four levers.
An increasing trend is to provide 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 extends through the spindle so that long bar stock can be fed through it. The size of this 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 spinale.
The inner end of the spindle protrudes from the gear box and contains a means for mounting various types of chucks, face plates, and dog plates 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 modem lathes have motors of from 5 to15 horsepower to provide adequate power for carbide 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 fits on the lower one and can be moved transversely upon it on some type of keyed ways. This transverse motion pemfits aligning the tailstock and headstock spindles and provides a method of tuming tapers. The third major component of the assembly is the tailstock quill. This is a hollow steel cylinder, usually about 2 to sinches in diameter, that can be moved several 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 on 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 in any desired position.
The carriage assembly provides the means for mounting and moving cutting tools. The carriage is a reianvely fiat H-shaped casting that rests 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 handwheel 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 short lead screw operated by a handwheel 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 handwheel 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.
MILLING
Milling is a basic machining process in which the surface is generated by the progressive formation and removal of chips of material from the workpiece as it is fed to a rotating cutter in a direction perpendicular to the axis of the cutter. In some cases the workpiece is stationary and the cutter is fed to the work. In most instances a multiple-tooth cutter is used so that the metal removal rate is high, and frequently the desired surface is obtained in a single pass of the work.
The tool used in milling is known as a milling cutter. It usually consists of a cylindrical body which rotates on its axis and contains equally spaced peripheral teeth that intermittently engage and cut the workpiece. 1 In some cases the teeth extend part way across one or both Ends of the cylinder.
Because the milling principle provides rapid metal removal and can produce good surface finish, it is particularly well-suited for mass-production work, and excellent milling machines have been developed for this purpose. However, very accurate and versatile milling Machines of a general-purpose nature also have been developed that are widely used in jobshop and tool and die work. A shop that is equipped with a milling machine and an engine lathe can machine almost any type of product of suitable size.
Types of Milling Operations. Milling operations can be classified into two broad categories, each of which has several variations:
1. In peripheral milling a surface is generated by teeth located in the periphery of the cutter body; the surface is parallel with the axis of rotation of the cutter. Both flat and formed surfaces can be produced by this method. The cross section of the resulting surface corresponds to the axial contour of the cutter. This procedure often is called slab milling.
2. In face milling the generated flat surface is at right angles to the cutter axis and is the combined result of the actions of the portions of the teeth located on both the periphery and the face of the cutter. 2 The major portion of the cutting is done by the peripheral portions of the teeth with the face portions providing a finishing action.
The basic concepts of peripheral and face milling are illustrated in Fig. 16-1. Peripheral milling operations usually are performed on machines having horizontal spindles, whereas face milling is done on both horizontal- and vertical-spindle machines.
Surface Generation in Mimng. Surfaces can be generated in milling by two distinctly different methods depicted in Fig. 16-2. Note that in up milling the cutter rotates againsi the direction of feed the workpiece, whereas in down milling the rotation is in the same direction as the feed. As shown in Fig. 16-2, the method of chip formation is quite different in the two cases. In up milling the c hip is very thin at the beginning, where the tooth first contacts the work, and increases in thickness, becoming a maximum where the tooth leaves the work. The cutter tends to push the work along and lift it upward from Tool-work relationshios in peripheral and face milling the table. This action tends to eliminate any effect of looseness in the feed screw and nut of the milling machine table and results in a smooth cut. However, the action also tends to loosen the work from the clamping device so that greater clamping forcers must be employed. In addition, the smoothness of the generated surface depends greatly on the sharpness of the cutting edges.
In down milling, maximum chip thickness cecum close to the point at which the tooth contacts the work. Because the relative motion tends to pull the workpiece into the cutter, all possibility of looseness in the table feed screw must be eliminated if down milling is to be used. It should never be attempted on machines that are not designed for this type of milling. Inasmush as the material yields in approximately a tangential direction at the end of the tooth engagement, there is much less tendency for the machined surface to show tooth marks than when up milling is used. Another considerable advantage of down milling is that the cutting force tends to hold the work against the machine table, permitting lower clamping force to be employed. 3 This is particularly advantageous when milling thin workpiece or when taking heavy cuts.
Sometimes a disadvantage of down milling is that the cutter teeth strike against the surface of the work at the beginning of each chip. When the workpiece has a hard surface, such as castings do, this may cause the teeth to dull rapidly.
Milling Cutters. Milling cutters can be classified several ways. One method is to group them into two broad classes, based on tooth relief, as follows:
1. Profile-cutters have relief provided on each tooth by grinding a small land back of the cutting edge. The cutting edge may be straight or curved.
2. In form or cam-reheved cutters the cross section of each tooth is an eccentric curve behind the cutting edge, thus providing relief. All sections of the eccentric relief, parallel with the cutting edge, must have the same contour as the cutting edge. Cutters of this type are sharpened by grinding only the face of the teeth, with the contour of the cutting edge thus remaining unchanged.
Another useful method of classification is according to the method of mounting the cutter. Arbor cutters are those that have a center hole so they can be mounted on an arbor. Shank cutters have either tapered or straight integral shank. Those with tapered shanks can be mounted directly in the milling machine spindle, whereas straight-shank cutters are held in a chuck. Facing cutters usually are bolted to the end of a stub arbor.
The common types of milling cutters, classified by this system are as follows:
Types of Milling Cutters. Hain milling cutters are cylindrical or disk-shaped, having straight or helical teeth on the periphery. They are used for milling flat surfaces. This type of operation is called plai n or slab milling. Each tooth in a helical cutter engages the work gradually, and usually more than one tooth cuts at a given time. This reduces shock and chattering tendencies and promotes a smoother surface. Consequently, this type of cutter usually is preferred over one with straight teeth.
Side milling cutters are similar to plain milling cutters except that the teeth extend radially part way across one or both ends of the cylinder toward the :center. The teeth may be either straight or helical. Frequently these cutters are relatively narrow, being disklike in shape. Two or more side milling cutters often are spaced on an arbor to make simultaneous, parallel cuts, in an operation called straddle milling.
Interlocking slotting cutters consist of two cutters similar to side mills, but made to operate as a unit for milling slots. The two cutters are adjusted to the desired width by inserting shims between them.
Staggered-tooth milling cutters are narrow cylindrical cutters having staggered teeth, and with alternate teeth having opposite helix angles. They are ground to cut only on the periphery, but each tooth also has chip clearance ground on the protruding side. These cutters have a free cutting action that makes them particnlarly effective in milling deep slots.