銑削組合機床主軸箱設計

銑削組合機床主軸箱設計,銑削組合機床主軸箱設計,銑削,組合,機床,主軸,設計 英文原文 Basic Machining Operations Machining tools have evolved from the early foot –powered lathe Egyptians and John Wilkinson’s boring mill. They are designed to provide rigid support for both the workpiece and the cutting tool and cutting tool and can precisely control their relative positions and the velocity of the tool with respect to the workpiece. Basically, in metal cutting, a sharpened wedge-shaped tool removes a rather narrow strip of metal from the surface of a ductile workpiece in the from of a severely deformed chip. The chip is waste product that is workpiece in the from of a severely deformed chip is a waste product that is considerably shorter than the workpiece from which it came but with a corresponding increase in thickness of the uncut chip. The geometrical shape of the machine surface depends on the shape of the tool and its path during the machining opration. Most machine operations produce parts of differing geometry. If a rough cylindrical workpiece revolves about a central axis and tool penetrates beneath its surface and travels parallel to the center of rotation, a surface of revolution is produced, and the operation is called turning. If a hollow tube is on the machined on the inside in a similar manner, the operation is called boring. Producing an external conical surface of uniformly varying diameter is called taper turning. If the tool point travels in a path of varying radius, a contoured surface like that of bowling pin can be produced; or, if the piece is short enough and the support is sufficiently rigid, a contoured surface could be produced by feeding a shaped tool normal to the axis of rotation. Short tapered or cylindrical surfaces could also be contour formed. Flat or plane surface are frequently required. They can be generated by radial turning or facing, in which the tool point moves normal to the axis of rotation. In other cases, it is more convenient to hole the workpiece steady and reciprocate the tool across , it is series of straight-line cuts with a crosswise feed increment before each cutting stroke. This operation is called planning and is carried out on a shaper. For larger pieces it is easier to keep the tool stationary and draw the workpiece under it as in planning. The tool is fed at each reciprocation. Contoured surfaces can be produced by using shaped tools. Multiple-edged tools can also be used. Drilling uses a twin-edged fluted tool for holes with depths up to 5 to 10 times the drill diameter. Whether the drill turns or the workpiece rotates, relative motion between the cutting edge and the workpiece is the important factor. In milling operations a rotary cutter with a number of cutting edges engages the workpiece, which moves slowly with respect to the cutter. Plane or contoured surfaces may be produced, depending on the geometry of the cutter and the type of feed. Horizontal or vertical axes of rotation may be used, and the feed of the work piece may be in any of the three coordinate directions. Basic Machine Tools Machine tools are used to part of a specified geometetrical shape and precise size by removing metal from a ductile material in the form chips. The latter are a waste product and vary from long continuous ribbons of a disposal point of view, to easily handed well-broken chips resulting from cast iron. Machine tools perform five basic metal-remove processes: turning, planning, drilling, milling, and grinding. All other metal-removal processes are modifications of these five basic processes. For example, boring is internal turning; reaming, tapping, and counter boring mollify drilled holes and are related to drilling; hobbling and gear cutting are fundamentally milling operations; hack sawing and broaching are a from of planning and honing; lapping, super finishing, polishing, and buffing are variants of grinding or abrasive removal operations. Therefore, there are only four types of basic machine tools, which use cutting tools of specific controllable geometry. The grinding process forms chips, but the geometry of the abrasive grain is uncontrollable. The amount and rate of material removed by the various machining processes may be large, as in heavy turning operations, or extremely small, as in lapping or superfinishing operations where only the high spots of a surface are removed. A machining tool performs three major functions: 1. it rigidly supports the workpice or its holder and the cutting tool; 2. it provides relative motion between the workpice and the cutting tool; 3. it provides a range of feeds and speeds usually ranging from 4 to32 choices in each case. Speed and Feeds in Machining Speeds, feeds, and depth pf cut are the three major variables for economical machining. Other variables are the work and tool materials, coolant and geometry of the cutting tool. The rate of metal removal and power required for machining depend upon these variables. The depths of cut, feed, and cutting speed are machine setting that must be established in any metal-cutting operation. They all affect the forces, the power, and the rate of metal removal. They can be defined by comparing them to the needle and record of a phonograph. The cutting speed (V) is represented by the velocity of the record surface relative to the needle in the tone arm at any instant. Feed is represented by the advance of the needle radially inward per revolution, or is the difference in position between two adjacent grooves. The depth of cut is the penetration of the needle into the record or the depth of the grooves. Turning on lathe centers The basic operations operations performed on an engine lathe are illustrated in fig. 11-3. those operations performed on external surfaces with a single point cutting tool are called turning. Except for drilling, reaming, and tapping, the operations on internal surfaces are also performed by a single point cutting tool. All machining operate, including turning and boring, can be classified as roughing, finishing, or semi-finishing. The objective of a roughing operation is to remove the bulk of the material as rapidly and as efficiently as possible, while leaving a small amount of material on the work-piece for the finishing operation. Finishing operations are performed to obtain the final size, shape, and surface finish on the workpiece. Sometimes a semi-finishing operation will precede the finishing operation to leave a small predetermined and uniform amount of stock on the work-piece to be removed by the finishing operation. Generally, longer workpieces are turned while supported on one or two lathe centers. Cone shaped holes, called center holes, which fit the lathe centers are drilled in the end of the workpiece-usually along the axis of the cylindrical part. The end of the workpiece adjacent to the tailstock is always supported by a tailstock center, while end near the headstock may be supported by a headstock center or held in a chuck. The headstock end of the workpiece may be held in a four-jaw chuck, or in a collet type chuck. This method holds the workpiece firmly and transfers the power to the workpiece smoothly; the additional support to the workpiece provided by the chuck lessens the tendency for chatter to occur when cutting. Precise result can be obtained with this method if care is taken to hold the workpiece accurately in the chuck. Very precise results can be obtained by supporting the workpiece between two centers. A lathe dog is clamped to the workpiece; together they are driven by the driver plate mounted on the spindle nose. One end of the workpiece is machined; then the workpiece can be turned around in the lathe to machine to other end. The center holes in the workpiece serve as precise locating surfaces as well as bearing surfaces to carry the weight of the workpiece and to resist the cutting forces. After the workpiece has been remove from the lathe for any reason, the center holes will accurately align the workpiece back in the lathe or in another lathe, or in a cylindrical grinding machine. The workpiece must never be held at the headstock end by both a chuck and a lathe center. While at first thought this seems like a quick method of aligning the workpiece in the chuck, this must not be done because it is not possible to press evenly with the jaws against the workpiece while it is also supported by the center. The alignment provided by the center will not be maintained and the pressure of the jaws may damage the center hole, the lathe center, and perhaps even the lathe spindle. Compensating or floating jaw chucks used almost exclusively on high production work provide an exception to the statements made above. These chucks are really work drivers and cannot be used for the same purpose as ordinary three or four-jaw chicks. While very large diameter workpiece are sometimes mounted on two centers, they are preferably held at the headstock end by faceplate jaws to obtain the smooth power transmission; moreover, large lathe dogs that are adequate to transmit the power not generally available, although they can be made as a special. Faceplate jaws are like chuck jaws except that they are mounted on a faceplate, which has less overhang from the spindle bearings than a large chuck would have. Boring The objective of boring a hole in a lathe is: 1、To enlarge the hole 2、To machine the hole to the desired diameter 3、To accurately locate the position of the hole 4、To obtain a smooth surface finish in the hole The motion of the boring tool is parallel to the axis of the lathe when the carriage is moved in the longitudinal direction and the work piece revolves about the axis of the lathe. When these two motions are combined to bore a hole, it will be concentric with the axis of rotation of the lathe. The position of the hole can be accurately located by holding the work piece in the lathe so that the axis about which the hole is to be machined coincides with the axis of rotation of the lathe. When the boring operation is done in the same setup of the work that is used to turn and face it, practically perfect concentricity and perpendicularity can be achieved. The boring tool is held in a boring bar which is fed through the hole by carriage. Variations of this design are used, depending on the job to be done. The lead angle used, if any, should always be small. Also, the nose radius of the boring tool must not be too large. The cutting speed used for boring can be equal to the speed for turning. However, when the spindle speed of the lathe is calculated, the finished, or largest, bore diameter should be used. The feed rate for boring is usually somewhat less than for turning to compensate for the rigidity of the boring bar. The boring operation is generally performed in two steps; namely, rough boring and finish boring. The objective of the rough-boring operation is to remove the excess metal rapidly and efficiently, and the objective of the finish-boring operation is to obtain the desired size, surface finish, and location of the hole. The size of the hole is obtained by using the trial-cut procedure. The diameter of the hole can be measured with inside calipers and outside micrometer calipers. Basic Measuring Instrument, or inside micrometer calipers can be used to measure the diameter directly. Cored holes and drilled holes are sometimes eccentric with respect to the rotation of the lathe. When the boring tool enters the work, the boring bar will take a deeper cut on one side of the hole than on the other, and will deflect more when taking this deeper cut, with the result that the bored hole will not be concentric with the rotation of the work.. This effect is corrected by taking several cuts through the hole using a shallow depth of cut. Each succeeding shallow cut causes the resulting hole to be more concentric than it was with the previous cut. Before the finale, finish cut is taken, the hole should be concentric with the rotation of the work in order to make certain that the finished hole will be accurately located. Shoulders, grooves, contours, tapers, and threads are also bored inside of holes. Internal grooves are cut using a tool that is similar to external grooving tool. The procedure for boring internal shoulder is very similar to the procedure for turning shoulders. Larger shoulders are faced with the boring tool positioned with the nose leading, and using the cross slide to feed the tool. Internal contours can be machined using a tracing attachment on a lathe. The tracing attachment is mounted on the cross slide and the stylus follows the outline of the master profile plate. This causes the cutting tool to move in a path corresponding to the profile of the profile plate. Thus, the profile on the master profile plate is reproduced inside the bore. The master profile plate is accurately mounted on a special slide which can be precisely in two directions, in order to align the cutting tool in the correct relationship to the work. This lathe has cam-lock type of spindle nose which permits it to take a cut when rotating in either direction. Normal turning cuts are taken with the spindle rotating counterclockwise. The boring cut is taken with the spindle revolving in a clockwise direction, or “backwards”. This permit the boring cut to be taken on the “back side” of the bore which is easier to see from the operator’s position front of the lathe. This should not be done on lathes having a threaded spindle nose because the cutting force will tend to unscrew the chuck. Milling Milling is a machining process for removing material by relative motion between a workpiece and a rotating cutter having multiple cutting edges. In some applications, the workpiece is held stationary while the rotating cutter is moved past it and a given feed rate (traversed). In other applications, both the workpiece and cutter are moved in relation to each other and in relation to the milling machine. More frequently, however, the workpiece is advanced at a relatively low rate of movement or feed to a milling cutter rotating at a comparatively high speed, with the cuter axis remaining in a fixed position, a characteristic feature of the milling process is that each milling cutter tooth takes its share of the stock in the form of small individual chips. Milling operations are performed on many different machines. Since both the workpiece and cutter can be moved relative to one another, independently or in combination, a wide variety of operations can be performed by milling. Applications include the production of flat or contoured surfaces, slots, grooves, recesses, threads, and other configurations. Milling is one of the most universal, yet complicated machining methods. The process has more variations in the kinds of machines used, workpiece movements, and types of tooling than any other basic machining method. Important advantages of removing material by means of milling include high stock removal rates, the capability of producing relatively smooth surface finishes, and the wide variety if cutting tools that are available. Cutting edges of the tools can be shaped to form any complex surface. The major milling methods are peripheral and face milling; in addition, a number of related methods exist that are variations of these two methods, depending upon the type of workpiece or cutter. Peripheral Milling On peripheral milling, sometimes called slab milling, the milled surface generated by teeth or inserts located in the periphery of the cutter body is generally in a plane parallel to the cutter axis. Milling operations with form-relieved and formed profile cutters are included in this class. The cross section of the milled surface corresponds to the outline or contour of the milling cutter or combination of cutters used. Peripheral milling operations are usually performed on milling machines with the spindle positioned horizontally, however, they can also be performed with end mills on vertiasl-spindle machines. The milling cutters are mounted on an arbor which is generally supported at the outer end for increased rigidity, particularly when, because of the conditions of the setup, the cutter or cutters are located at some distance from the nose of the spindle. Peripheral milling should generally not be done if the peripheral milling should generally not be done if the part can be face milled. Face Milling Face milling is done on both horizontal and vertical milling machines. The milled surface resulting from the combined action of cutting edges located on the periphery and face of the cutter is generally at right angles to the cutter axis. The milled surface is flat, with no relation to the contour of the teeth, except when milling is done to a shoulder. Generally, face milling should be applied wherever and whenever possible. Chip thickness in conventional (up) face milling varies from a minimum at the entrance and exit of the cutter tooth to a maximum along the horizontal diameter. The milled surface is characterized by tooth and revolution marks, as in the case of peripheral milling cutters. The prominence of these marks is controlled by the accuracy of grinding the face cutting edge of the teeth, or by the accuracy of the body/insert combination in indexable cutters and of mounting the cutter so that it runs true on the machine spindle. It is also controlled by the rigidity of the machine and workpiece itself. When the length of the face cutting edge is less than the feed per revolution (or the amount the work has moved in one revolution of the cutter), a series of roughly circular grooves or ridges results on the milled surface. Similar marking is produced by the trailing teeth drag on the milled surface of the work. This is known as heel drag. In face milling, it is important to select a cutter with a diameter suited to the proposed width of cut if best results are to be obtained. Cuts equal in width to the full cutter diameter should be avoided, if possible, since the thin chip section at entry of the teeth results in accelerated tooth wear abrasion plus a tendency for the chip to weld or stick to the tooth or insert and be carried around and recut. This is detrimental to surface finish. A good ratio of cutter diameter to the width of the workpiece or proposed path of cut is 5:3. 中文譯文 基本的加工工序—切削，鏜削和銑削 機床是從早期的埃及人的腳踏動力車床和約翰.威爾金森的鏜床發(fā)展而來的。它們用于為工件和刀具兩者提供剛性支撐并且可以精確控制它們的相對位置和相對速度。一般來說，在金屬切削中用一個磨尖的楔形工具以緊湊螺紋形的切屑形式從有韌性工件表面上去除一條很窄的金屬。切屑是廢棄的產(chǎn)品，與其工件相比，它相當短但是比未切削的部分厚度有相對的增加。機器表面的幾何形狀取決于刀具的形狀以及加工過程中刀具的路徑。 不同的加工工序生產(chǎn)出不同幾何形狀的部件。如果一個粗糙的柱形工件繞中心軸旋轉(zhuǎn)而且刀具穿透工件表面并沿與旋轉(zhuǎn)中心平行的方向前進，就會產(chǎn)生一個旋轉(zhuǎn)面，這道工序叫車削。如果以類似的方式加工一根空心管的內(nèi)部，則這道工序就叫鏜削。制造一個直徑均勻變化的錐形外表面叫做錐體車削。如果刀具尖端以一條半徑可變的路徑前進，就可以制造出象保齡球桿那種仿形表面；如果工件足夠短而且支撐具有足夠的剛性，仿形表面可以通過用一個垂直于旋轉(zhuǎn)軸的仿形刀具來制造。短的錐面或柱面也可以仿形切削。 常常需要的是平坦的或平的表面。它們可以通過徑向車削或端面車削來完成，其中刀具尖端沿垂直于旋轉(zhuǎn)軸的方向運動。在其他情況下，更方便的是固定工件不動，以一系列直線方式往復運動刀具橫過工件，在每次切削行程前具有一定橫向進給量。這種龍門刨削和牛頭刨削是在刨床上進行的。大一些的工件很容易保持刀具固定不動，而像龍門刨削那樣在其下面拉動工件，再每次往復進給刀具。仿形面可以通過使用仿形刀具來制造。 也可以使用多刃刀具。鉆削使用兩刃刀具，深度可達鉆頭直徑的5-10倍。不管是鉆頭轉(zhuǎn)動還是工件轉(zhuǎn)動，切削刃與工件之間的相對運動都是一個重要因素。在銑削作業(yè)中，有許多切削刃的旋轉(zhuǎn)銑刀與工件相接合，這種工件相對銑刀運動緩慢。根據(jù)銑刀的幾何形狀和進給的方式，可以加工出平面和仿形面?？梢允褂盟交虼怪毙D(zhuǎn)軸，工件可以沿三個坐標方向中的任意一個進給。 基本的機床 機床用于以切屑的形式從韌性材料上去除金屬來加工特殊幾何形狀和精密尺寸的部件。切屑是廢品，其變化形狀從像鋼這樣的韌性材料的長的連續(xù)帶狀屑到鑄鐵形成的易于處理、徹底斷掉的切屑，從處理的觀點來講，不想要長的連續(xù)帶狀屑。機床完成5種基本的金屬切削工藝：車削、刨削、鉆削、銑削和磨削。其他所有金屬切削工藝都是這5種基本工藝的變形。例如：鏜削是內(nèi)部車削；鉸削、錐體車削和平底锪孔則修改鉆孔，與鉆削有關；滾齒與切齒是基本銑削作業(yè)；弓鋸削和拉削是銑削和磨削的一種形式；而研磨、超精加工、拋光和磨光是磨削和研磨切削作業(yè)的各種變化形式。因此，僅有4種使用專用可控幾何形狀的刀具基本機床：1、車床，2、刨床，3、鉆床，4、銑床。磨削工藝形成碎屑，但是磨粒的幾何形狀不可控制。 不同加工工藝切削的材料的數(shù)量和速度卻不相同?？赡軜O大，如大型車削作業(yè)；或者極小，如磨削和超精加工作業(yè)，只有表面高出的點被去除。 機床完成3種主要功能：1、剛性支撐工件或工件夾具以及切削刀具；2、提供工件與切削刀具之間的相對運動；3、提供了一定范圍的速度進給，通常每種有4-32種選擇。 切削速度和進給 切削速度、進給量和切削深度是切削加工的3個主要變量，其他變量還有工件和工具材料、冷卻劑以及切削刀具的幾何形狀。金屬切削的速率和加工所需的功率就決定于這些變量。 切削深度、進給量和切削速度是任何金屬切削作業(yè)中必須都建立的變量。它們都影響切削力、功率和對金屬切削的速率?？梢酝ㄟ^把它們與留聲機的唱針和唱片相比較給出定義。切削速度（V）由任意時刻唱片表面相對于拾音器支臂內(nèi)部的唱針的速度來表示；進給量由唱針每圈徑向向內(nèi)的前進量或者由兩個相鄰槽的位置差來表示。切削深度是唱針進入的量或者是槽的深度。 切削 那些在外表面上用單刃刀具完成的工序叫車削。除鉆削、鉸削和錐體車削外，在內(nèi)表面的作業(yè)也由單刃刀具完成。 包括車削和鏜削在內(nèi)的所有加工工序都可以分為粗加工、精加工和半