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1、 本科生毕业设计(论文)外 文 翻 译 原 文 标 题 An intelligent fixture design method based on smart modular fixture unit 译 文 标 题 基本的加工工序切削，镗削和铣削 作者所在系别 机电工程学院 作者所在专业 机械设计制造及自动化 作者所在班级 作 者 姓 名 作 者 学 号 指导教师姓名 指导教师职称 完 成 时 间 -1-译文标题 基本的加工工序切削，镗削和铣削 原文标题 Basic Machining OperationsTurning,Boring and Milling 作 者 B.W.Nile 译 名
2、 本.沃.聂迩 国 籍 加拿大 原文出处 Modern Manufacturing Process Engineering 译文：基本的加工工序 机床是从早期的埃及人的脚踏动力车床和约翰.威尔金森的镗床发展而来的。它们用于为工件和刀具两者提供刚性支撑并且可以精确控制它们的相对位置和相对速度。一般来说，在金属切削中用一个磨尖的楔形工具以紧凑螺纹形的切屑形式从有韧性工件表面上去除一条很窄的金属。切屑是废弃的产品，与其工件相比，它相当短但是比未切削的部分厚度有相对的增加。机器表面的几何形状取决于刀具的形状以及加工过程中刀具的路径。不同的加工工序生产出不同几何形状的部件。如果一个粗糙的柱形工件绕中心轴
3、旋转而且刀具穿透工件表面并沿与旋转中心平行的方向前进，就会产生一个旋转面，这道工序叫车削。如果以类似的方式加工一根空心管的内部，则这道工序就叫镗削。制造一个直径均匀变化的锥形外表面叫做锥体车削。如果刀具尖端以一条半径可变的路径前进，就可以制造出象保龄球杆那种仿形表面；如果工件足够短而且支撑具有足够的刚性，仿形表面可以通过用一个垂直于旋转轴的仿形刀具来制造。短的锥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。它们可以通过径向车削或端面车削来完成，其中刀具尖端沿垂直于旋转轴的方向运动。在其他情况下，更方便的是固定工件不动，以一系列直线方式往复运动刀具横过工件，在每次切削行程前具有一定横向进
4、给量。这种龙门刨削和牛头刨削是在刨床上进行的。大一些的工件很容易保持刀具固定不动，而像龙门刨削那样在其下面拉动工件，再每次往复进给刀具。仿形面可以通过使用仿形刀具来制造。也可以使用多刃刀具。钻削使用两刃刀具，深度可达钻头直径的 5-10 倍。不管是钻头转动还是工件转动，切削刃与工件之间的相对运动都是一个重要因素。在铣削作业中，有许多切削刃的旋转铣刀与工件相接合，这种工件相对铣刀运动缓慢。根据铣刀的几何形状和进给的方式，可以加工出平面和仿形面。可以使用水平或垂直旋转轴，工件可以沿三个坐标方向中的任意一个进给。基本的机床 机床用于以切屑的形式从韧性材料上去除金属来加工特殊几何形状和精密尺寸的部件。
5、切屑是废品，其变化形状从像钢这样的韧性材料的长的连续带状屑到-2-铸铁形成的易于处理、彻底断掉的切屑，从处理的观点来讲，不想要长的连续带状屑。机床完成 5 种基本的金属切削工艺：车削、刨削、钻削、铣削和磨削。其他所有金属切削工艺都是这5 种基本工艺的变形。例如：镗削是内部车削；铰削、锥体车削和平底锪孔则修改钻孔，与钻削有关；滚齿与切齿是基本铣削作业；弓锯削和拉削是铣削和磨削的一种形式；而研磨、超精加工、抛光和磨光是磨削和研磨切削作业的各种变化形式。因此，仅有 4 种使用专用可控几何形状的刀具基本机床：1、车床，2、刨床，3、钻床，4、铣床。磨削工艺形成碎屑，但是磨粒的几何形状不可控制。不同加工
6、工艺切削的材料的数量和速度却不相同。可能极大，如大型车削作业；或者极小，如磨削和超精加工作业，只有表面高出的点被去除。机床完成 3 种主要功能：1、刚性支撑工件或工件夹具以及切削刀具；2、提供工件与切削刀具之间的相对运动；3、提供了一定范围的速度进给，通常每种有4-32 种选择。切削速度和进给 切削速度、进给量和切削深度是切削加工的 3 个主要变量，其他变量还有工件和工具材料、冷却剂以及切削刀具的几何形状。金属切削的速率和加工所需的功率就决定于这些变量。切削深度、进给量和切削速度是任何金属切削作业中必须都建立的变量。它们都影响切削力、功率和对金属切削的速率。可以通过把它们与留声机的唱针和唱片相
7、比较给出定义。切削速度（V）由任意时刻唱片表面相对于拾音器支臂内部的唱针的速度来表示；进给量由唱针每圈径向向内的前进量或者由两个相邻槽的位置差来表示。切削深度是唱针进入的量或者是槽的深度。切削 那些在外表面上用单刃刀具完成的工序叫车削。除钻削、铰削和锥体车削外，在内表面的作业也由单刃刀具完成。包括车削和镗削在内的所有加工工序都可以分为粗加工、精加工和半精加工。粗加工工序的目的是尽可能迅速且高效地去除大量的材料，在工件上只留下少量的材料给精加工工序。精加工工序用以获得工件最终的大小、形状和表面粗糙度。有时，在精加工工序前进行半精加工作业以便在工件上留下少的、预定的和均匀量的原材料供精加工去除。通
8、常，较长的工件是在一个或两个车床顶尖的支撑下进行的。用于安装车床顶尖的锥形孔叫做顶尖孔，它是在工件的端部钻出的通常沿着柱形部件的轴心。与尾架邻近的工件端部总是由尾架顶尖支撑，而挨着主轴箱的一端则由主轴箱顶尖支撑或装在卡盘内。工件的主轴箱一端可以装在一个四爪卡盘或套爪卡盘-3-内。这种方法牢固地夹持工件并且把功率平稳地传送到工件上；由卡盘提供的额外支撑减少了车削作业时发生震动的倾向。如果仔细地将工件精确的固定在卡盘上，用这种方法将获得精密的结果。通过将工件支撑在两个顶尖之间可以获得非常精确的结果。一个车床夹头夹在工件上；然后由安装在主轴前端的拨盘一起带动。先加工工件的一端，然后可以在车床上将工件
9、掉头加工另一端。工件上的顶尖孔是用作精确定位面以及承受工件重量和抵抗车削力的支撑面。在工件被拆下后，顶尖孔可以精确地将其装回机床。工件千万不要同时通过卡盘和顶尖安装在主轴箱一端。虽然这样似乎是一种快捷方法，但是这样做使得工件受力不均匀，顶尖的对正作用不能维持，而且爪的压力可能损坏顶尖孔、车床顶尖甚至车床主轴。几乎被独自用在大量生产工件上的补偿或浮动爪式卡盘是上述的一个例外。这些卡盘是自动偏心夹紧卡盘不能起到普通三爪或四爪卡盘同样的作用。直径非常大的工件虽然有时安装在两个顶尖上，但是最好用花盘把它们固定在主轴箱端以获得流畅的动力传输；此外，可以把它们制造成专用部件，但是一般不能提供足够大的车床夹
10、头来传输动力。除非是安装在花盘上，其主轴轴承上的外伸要比大卡盘上的少一些。镗削 在车床上镗孔的目的是：1、扩孔；2、把孔加工到所需直径；3、精确的为孔定位；4、在孔内获得好的表面粗糙度。当刀具径向溜板纵向移动而工件绕车床的轴线旋转时，镗刀的运动平行于车床上的轴线。当两种运动结合起来镗孔时，就会与车床的旋转轴同心。通过把工件固定在车床上可以精确定位孔的位置以使待加工孔所环绕的轴与车床的旋转轴一致。当镗削工序与用于车削和刮削工序的设置相同时，实际上可以达到理想的同心与垂直。镗刀固定在一根通过刀具径向溜板进给的镗杆上。根据待做的工作来使用这一设计的变化形式。如果有的话，所用的倒角总是应该小些。而且，
11、镗刀前端的半径一定不能太大。用于镗孔的切削速度可以等于车削速度。但是，在计算车床主轴速度时，应当使用完成后的或最大的孔径。镗削的进刀速度通常比车削的小一点以补偿镗杆刚性的不足。镗削工序一般分两步完成，即粗镗和精镗。粗镗工序的目的是快速、高效地去除多余的金属；而精镗工序的目的是获得所需的尺寸、表面粗糙度和孔的位置。-4-孔的尺寸通过试切来获得。孔的直径可以用内卡尺和千分尺测量。测量仪表或内千分卡尺直接测量直径。型心孔和要钻的孔有时相对于车床的旋转是偏心的。当镗刀进入工件时，镗杆在孔的一边切口比另一边深，当采用这深切口时就会更偏斜，结果镗的孔与工件旋转不同心。这一影响通过利用浅切口在整个孔加工中进
12、行几次加工来纠正。因为每个浅切口形成的孔比使用深切口形成的孔更加同心。在完工前，进行精加工，孔应该与工件的旋转同心以确保完工时孔能精确定位。肩、沟槽、轮廓、锥度和螺纹也应该在孔内镗出。内槽是用与外部开槽工具相似的工具切削。镗削内槽的步骤非常类似于车削肩部的步骤。大的肩部使用前导装置定位的镗刀进行刮削，使用横向滑板进给工具。内部轮廓使用车床上的描摹附件加工。仿行板附件安装在横向滑板上，靠模指跟随标准剖面板的轮廓线运动。这使刀具对应于标准剖面样板的轮廓线的路径进行移动。这样标准剖面样板的轮廓就在孔内得到复制。标准剖面样板精确安装在一个专用的滑板上，滑板可以在两个方向上进行精确调整以使刀具与工件以正
13、确的关系对正。这台车床有一个偏心夹型的主轴前端，允许在任意一方向旋转时进行切削。正常的车削是在主轴逆时针转动时进行的；镗削切削是在主轴顺时针方向或“向后”转动时进行的。这允许在孔的“后侧”进行镗削切削，在车床前面，从操作者的位置易于看到后孔。在具有螺纹主轴前端的车床上不应这么做，因为切削力的作用会旋松卡盘。铣削 铣削是一种通过工件与多刃旋转铣刀间的相对运动去除材料的加工工艺。在一些应用中，工件固定而旋转的铣刀以一定进给速度移过工件（横向进给）；在其他应用中，工件与铣刀既彼此相对运动，又相对铣床运动。但是，更常见的是工件以一个相对较低的运动速度或进给速度朝正在高速旋转的铣刀前进，而铣刀轴保持在一
14、个固定位置。铣削工艺特有的性能是每个铣刀齿都以小的单个切屑的形式切去一部分原料。可以在许多不同的机器上进行铣削作业。由于工件和铣刀都可以彼此相对运动，铣削可以独立的或以组合方式完成各式各样的作业。各种应用包括平面或仿行面、窄槽、槽、退刀槽、螺纹和其他外形的加工。铣削是一种最为通用而又复杂的加工方法。该工艺比任何其他基本加工方法在所用机器的种类、工件运动以及加工工具种类方面都具有更多的变化。利用铣削去除材料的重要优点包括原料切削速度高，能形成相对光滑的表面粗糙度以及可应用的刀具更为多样。刀具的切削刀刃可以仿行以形成任何复杂的表面。主要的铣削方法有周铣和端铣，此外，还有许多相关方法，他们属于这2
15、种方法的变化形式，这些变化形式取决于工件或刀具的类型。-5-周铣 在周铣（有时也叫平面铣削）中，由位于铣刀主体外周上的尺或刀片铣削的面一般在一个与铣刀轴平行的平面上。使用铲齿铣刀和成形铣刀完成的铣削工序包括在这一类。铣削面的界面与所使用的铣刀或刀具组合的轮廓线或轮廓相符。周铣作业通常在带有水平定位主轴的铣床上进行。但也可以在带有端面铣刀的主轴铣床上进行。铣刀安装在心轴上，尤其是由于设置的条件，铣刀或者若干铣刀位于距主轴前端一定距离处时，心轴一般在外端得到支撑来提高刚性。如果部件可以端铣，一般不应进行周铣。端铣 端铣在卧式铣床和立式铣床上进行。由位于铣刀外周和端面的切削刃联合铣削所形成的铣削面一
16、般与铣刀轴成直角。除了在肩部铣削时外，铣削面是平的，与齿的轮廓形状无关。一般来讲，无论何时何地，只要可能就应使用端铣。传统（上）端铣中切屑厚度是变化的，在铣刀齿进入和退出处最薄，而在沿水平直径处最大。铣削面由齿和专属转速痕迹表现其特征，这与周铣铣刀情况相同。这些痕迹的起伏度由齿的端面切削刃的磨削精度或由刀体/刀片在可以指标化的刀具内组合精度以及刀具安装精度来控制，以使刀具在主轴上精确运动。起伏度还由机器及工件本身的刚性来控制。当端面切削刃的长度短于每转的进给量（或铣刀每转一圈工件的移动量）时，在铣面上就会形成一系列的环形凹槽或环纹。当后齿在工件的铣面上拖动时，也会产生类似的标记，这叫齿根拖动。
17、在端铣中，如果想获得最佳结果，重要的是选择铣刀具有适于所建议的切削宽度的直径。如果可能，应避免切削宽度等与铣刀外径相同，因为在齿的入口处，薄的铣屑界面会由于研磨加上铣屑有焊或粘到齿或刀片上并被带来带去或再次切削的趋向而导致齿的加速磨损。这对表面粗糙度是有害的。好的铣刀直径与工件或提议的切削路线宽度之比是5：3。-6-原文：Basic Machining Operations Machining tools have evolved from the early foot powered lathe Egyptians and John Wilkinsons boring mill.They a
18、re 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 me
19、tal 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
20、 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 surfa
21、ce 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
22、 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
23、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
24、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
25、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 e
26、dge and the workpiece is the important factor.In milling operations a rotary cutter with a number of cutting edges -7-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.Horizonta
27、l 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
28、 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
29、 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,p
30、olishing,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 r
31、ate 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 o
32、r 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
33、 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 operat
34、ion.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 -8-surface relative to the needle in the tone arm at any instant.Feed is represented
35、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 lath
36、e 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
37、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 perfo
38、rmed 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 turn
39、ed 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 e
40、nd 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 workpiec
41、e 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
42、 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 t
43、o 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 -9-workpiece back in the lathe or in another lathe,or in a cylindrical grinding machine.The workpiece must never be held a
44、t 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 alignm
45、ent 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 ch
46、ucks 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 la
47、the 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 borin
48、g a hole in a lathe is:1To enlarge the hole 2To machine the hole to the desired diameter 3To accurately locate the position of the hole 4To 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 dir
49、ection 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 ho
50、le 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 t