机械设计制造及其自动化专业英语.doc

机械设计制造及其自动化专业英语

Chapter One Materials and Mechanical Elements Lesson 1Introduction for Materials Designers and engineers are usually more interested in the behavior of materials under load or when in amagnetic field in why they behave as they do.Yet the better one understands the nature of materials and the reasons for their physical and mechanical properties the more quickly and wisely will he/she be able to choose the proper material for agiven design.Generally,a material property is the measured magnitude of its response to astandard test performed according to astandard procedure in agiven environment.In engineering materials the loads are mechanical or physical in nature and the properties are recorded in handbooks or,for new materials,are made available by the supplier.Frequently such information is tabulated for room-temperature conditions only,so when the actual service conditions are at subfreezing or elevated temperatures,more information is needed.
第一章材料和机械零件
第一课材料介绍
设计者和工程师们通常都会对在加载状态下或处于磁场中的材料的性能更感兴趣，而不关心它们为什么具有这个性能。然而，一个人若能更好地理解这些材料的性质和它们的物理和机械的性能原因，了解得越清楚，他/她就能更快速和准确地选择合适的材料。通常，材料性能是在给定的环境条件下按照规定的方法进行的标准试验所获得的测定值。事实上，工程材料中的加载实质上是机械的或物理的加载，并且性能是记录在手册上的，或者，对于新材料来说，是应由供应商来提供性能手册的。一般来说类似的信息仅仅是在室温条件下被列表显示的，因此，当实际的操作条件是在冰点以下或在高温条件下，则会需要更多的信息。
Lesson 4Gears Helical gears have certain advantages；for example,when connecting parallel shafts they have ahigher loadcarrying capacity than spur gears with the same tooth numbers and cut with the same cutter.Because of the overlapping action of the teeth,they are smoother in action and can operate at higher pitch-line velocities than spur gears.The pitch-line velocity is the velocity of the pitch circle.Since the teeth are inclined to the axis of rotation,helical gears create an axial thrust.If used singly,this thrust must be absorbed in the shaft bearings.The thrust problem can be overcome by cutting two sets of opposed helical teeth on the same blank.Depending on the method of manufacture,the gear may be of the continuous-tooth herringbone variety or adouble-helical gear with aspace between the two halves to permit the cutting tool to run out.Double-helical gears are well suited for the efficient transmission of power at high speeds.
第四课齿轮
斜齿轮有某些优点；例如，在具有相同齿数且用同样的刀具来加工的情况下，连接平行轴的斜齿轮的承载能力要比直齿轮更高一些。由于轮齿的重叠作用，斜齿轮在运动中比直齿轮更平稳，并且能够以更高的节线速度来运行。节线速度就是节圆的线速度。由于轮齿向轴线的旋转方向倾斜，故斜齿轮产生了一个轴向推力。如果是单个的齿轮，这个推力必定会被轴向轴承吸收。通过在同一个坯件上切削两组相对的斜齿轮，能够克服推力的问题。根据不同的制造方法，齿轮可以是连续的人字形齿轮，或者是在两列斜齿之间留一间隙的双斜齿形齿轮，以便切削刀具通过。双斜齿形齿轮更适合以高速度进行高效地传送。
Lesson 6Dimensioning The design of amachine includes many factors other than those of determining the loads and stresses and selecting the proper materials.Before construction or manufacture can begin,it is necessary to have complete assembly and detail drawings to convey all necessary information to the shop men.The designer frequently is called upon to check the drawings before they are sent to the shop.Much experience and familiarity with manufacturing processes are needed before one can become conversant with all phases of production drawings.
Drawings should be carefully checked to see that the dimensioning is done in amanner that will be most convenient and understandable to the production departments.It is obvious that adrawing should be made in such away that it has one and only one interpretation.In particular,shop personnel should not be required to make trigonometric or other involved calculations before the production machines can be set up.
第六课标注
要设计一个机床除了要考虑那些已确定的负载和应力并且选择合适的材料以外，还包括很多其他的因素。在构造和加工开始以前，必须要把完整的装配图和详细的零件图的全部有用的信息传达给工人。设计者经常要在图纸未被送到车间以前检查核对图纸。每个人在熟悉生产图纸的各个阶段之前都必须具有丰富的经验并精通加工工艺。
应该仔细检查图纸，为生产部门作标注时须用一种最合适和最易理解的方式进行，很明显，一张图纸应该是有且只有一种解释的。尤其是不能要求车间工人先进行三角或其他复杂的计算后才能去调整机床。
Chapter Two Machine Tool,Cutting Tool,Jig and Fixture Lesson 1Engine Lathe(Center Lathe)
An engine lathe is shown diagrammatically in Fig.2.1a：it consists of ahorizontal bed supporting the headstock,the tailstock,and the carriage.All machine tools must have ameans of supporting or holding the workpiece.In Fig.2.1 the workpiece is gripped at one end by achuck mounted on the end of the main spindle of the machine and is supported at the other end by acenter mounted in the tailstock.The tailstock can be clamped at various positions along the bed to accommodate workpieces of various lengths.Short workpieces need only be gripped by the chuck.
Primary motion,the rotation of the workpiece(motion C'),is provided by the movement of aseries of gears driving the main spindle,the gears being driven by an electric motor mounted at the rear of the machine.The main spindle and the gears are all mounted in the headstock.Levers on the front of the headstock allow various rotational speeds to be sele cted.
第二章机床，切削刀具，钻模和夹具
第一课车床(普通车床)
一个普通车床的结构如图2.1a所示：它由支撑着主轴箱的卧式床身、尾座以及拖板三部分组成。所有的机床必须都要有一种支撑或夹紧工件的方式。在图2.1中，工件通过安装在机床主轴末端的卡盘在一端被夹紧，并且由装配在尾架上的顶尖在另一端被支撑。根据被加工工件长度的不同，尾架沿着床身被装夹在不同的位置。短的工件仅需要由卡盘夹紧。
主运动，即工件的旋转运动(也就是C'点的运动)，是由轮系驱动主轴实现工件旋转的，齿轮通过装夹在车床尾部的电机来带动它旋转。主轴和齿轮都装夹在主轴箱中。主轴箱前部的手柄能够根据实际需要选择不同的旋转速度。
Lesson 2Horizontal Milling Machine(Horizontal Miller)
There are two main types of milling machines：horizontal and vertical.These words again refer to the orientation of the main spindle.In the horizontal-milling machine shown in Fig.2.5 the milling cutter is mounted on ahorizontal arbor driven by the main spindle.The tools are therefore rotated(motion C)and the work fed continuously(motions X'or Y').
The simplest operation,slab milling,is used to generate ahorizontal surface on the workpiece,as shown in Fig.2.5.The figure shows the conventional slab-milling operation；if the workpiece had been fed in the opposite direction,it would tend to climb onto the work surface,and this type of slab milling is called"climb"milling.Some evidence suggests that the forces and power consumption are less in climb milling than in conventional milling.However,high rigidity of the machine tool and work and tool-holding devices is required for this operation.
第二课卧式铣床
铣床有两种主要类型：卧式和立式。这两种铣床再一次提到了主轴的方向。如图2.5所示的卧式铣床，铣刀被装在水平方向的刀杆上，这个刀杆由主轴来驱动。刀具因此是旋转的(C运动)，并且工件是连续地进给(X'、Y'方向的运动)。
平面铣的加工方式最简单，用来加工工件的水平表面，如图2.5所示。该图给出了平面逆铣加工；如果工件以相反的方向进给，刀具就像在工件表面上爬行一样，这种类型的平面铣也叫"顺"铣。一些证据表明，顺铣中的力和功率的消耗比逆铣中的少。然而，这就要求机床、工件和夹具要具有更高的硬度。
Lesson 3Shaping Machine(shaper)
The shaper is asmall machine on which the primary motion is linear(Fig.2.17).The single-point tool is gripped in atoolhead mounted on the end of aram.The ram is made to move backward and forward(X motion)either by amechanical drive system or ahydraulic piston and cylinder.The cutting stroke is the forward stroke,and with either mechanical or hydraulic shapers the forward ram speed is slower than the speed on the return stroke,causing the production time to be reduced as much as possible.A quick-return mechanism often used in mechanical shapers is shown in Fig.2.18.In all shapers the length of the stroke can be adjusted to suit the particular workpiece being machined.The feed is applied to the workpiece in increments at the end of the return stroke of the ram by arachet-and-pawl mechanism driving the lead screw in the crossrail.
Shapers are most commonly used to machine flat surfaces on small components and are only suitable for low-baton quantities.For the machining of ahorizontal surface(Fig.2.17),the workpiece is fed horizontally(Y'motion)；for vertical surfaces,the workpiece is fed vertically(Z'motion).
第三课牛头刨床(成型机)
牛头刨床是一个小型机床，它的主运动是直线运动(图2.17)。它的单刃刨刀被夹紧在刀架上，装卡在滑枕的末端。机械的驱动或者液压的活塞缸使得滑枕在X轴方向上进行前后移动。它向前供进的行程即为切削行程，并伴随着机械或者液压的成型机，滑枕向前的速度要比它回程的速度慢得多，这就会使加工时间尽可能的快，以提高工作效率。通常，用在机械牛头刨床的快回机械如图2.18所示。在所有的牛头刨床中，回程的长度均可根据需要做出相应的调整以适应不同的待加工工件。在滑枕返程的末端，进给被应用于工件的增量上，通过横导轨内的丝杆来驱动棘轮棘爪机构。
牛头刨床大多用于加工普通的小零件的平面表面，并且仅适合小批量加工生产。对于一个机件的水平表面的加工(图2.17)，工件沿水平方向进行进给(沿Y'轴方向运动)；对于垂直表面的加工，工件以垂直的方向进给(Z'轴方向)。
Lesson 4Automatic Machines Afinal class of automatic lathe is the multispindle automatic.These lathes are basically flexible,rotary-transfer machines where each spindle holding acollet or chuck is indexed around the various tooling positions so that during each indexing cycle acompleted component is produced.Drum cams instead of disk cams are used in these machines.
Another class of machine tool that can be mechanized is the internal or external cylindrical grinder.When fitted with mechanisms for loading workpieces automatically and with automatic wheel-dressing devices,these machines can continually produce finished components.The workpieces are often stacked in amagazine,and the operator simply ensures that the magazine is replenished with workpieces at suitable intervals.Because the components are small and the machining forces light,magnetic chucks are often employed to facilitate automatic work holding.
第四课自动机床
最后一组的自动车床是多主轴自动机床。这类机床基本上是灵活的旋转自动机，它的每一根轴上都有一个夹头或卡盘，可以绕不同位置的刀具转位，因此，每转位一次就加工出一个零件。在这类机床中，凸轮轴取代了盘形凸轮被使用。
另一类可以实现机械化的机床是内部的或外部的外圆磨床。当装上带有自动砂轮修整装置的自动装载工件的机械时，这些机床能够不断地生产成品组件。工件堆放在自动储存送料装置上，而操作者只需在适当的时间内将工件补放到送料装置上。因为这些组件很小，并且加工力道很轻，磁性夹头通常采用自动方式，以方便运行。
Lesson 5Jigs and Fixtures When several identical workpieces are to be produced the need to mark out each part is eliminated by the use of jigs and fixtures,but if acasting or forging is involved,a trial workpiece is marked out,to ensure that the workpiece can be produced from it,and to ensure that ribs,cores,etc.have not become misplaced.
Jigs and fixtures are alike in that they both incorporate devices to ensure that the workpiece is correctly located and clamped,but they differ in that jigs incorporate means of tool guiding during the actual cutting operation,and fixtures do not.In practice,the only cutting tools that can be guided while actually cutting are drills,reamers,and similar cutters；and so jigs are associated with drilling operations,and fixtures with all other operations.Fixtures may incorporate means of setting the cutting tools relative to the location system.
第五课钻模和夹具
当若干相同的工件需要加工时，通过使用钻模和夹具可不必对每个工件都进行划线。但如果加工的是铸件或锻件，则仍需对试件进行划线，以确保加工出合格的样件，而不致造成加强筋、内孔等位置偏移。
钻模和夹具类似，都是确保工件正确定位和夹紧的装置，但也有不同之处，钻模具有在实际加工过程中仍能导引刀具的元件，而夹具则没有。实际上，在切削过程中只有对钻头、铰刀以及类似的刀具才能进行导引，所以钻模通常与钻削加工相关联，而夹具是与其他所有加工方法相关联的。夹具可纳入设置相对定位系统的调刀手段。
Chapter Three Conventional and Nonconventional Machining Lesson 1Term and Definitions All metal-cutting operations can be likened to the process shown in Fig.3.1,where the tool is wedge-shaped,has astraight cutting edge,and is constrained to move relative to the workpiece in such away that alayer of metal is removed in the form of achip.Fig.3.1b depicts the general case of cutting known as oblique cutting.A special case of cutting,where the cutting edge of the tool is arranged to be perpendicular to the direction of relative work-tool motion(Fig.3.1a),is known as orthogonal cutting.Since orthogonal cutting represents atwo-dimensional rather than athree-dimensional problem,it lends itself to research investigations where it is desirable to eliminate as many of the independent variables as possible.The relatively simple arrangement of orthogonal cutting is therefore widely used in theoretical and experimental work.
The tool flank plays no part in the process of chip removal；however,the angle between the flank and the new workpiece surface can significantly affect the rate at which the cutting tool wears and is defined as the clearance angle or,more precisely,the working normal clearance.
Thus from Fig.3.2 the sum of the rake,clearance,and wedge angles is equal to 90 deg,where the wedge angle is the included angle between the face and the flank.
第三章常规和非常规加工
第一课术语和定义
所有的金属切削加工过程都可以用图3.1所示的过程来表示，即刀具是楔形的且具有直线切削刃，并且刀具相对于工件运动，每运动一次便会切下一层切屑。图3.1b描述了斜刃切削作为切削刀具的一般情况。切削中有一个特例，即刀具的切削刃相对于刀具的运动方向是垂直的(图3.1a)，这也叫直角切削。由于直角切削反映的是二维而不是三维的结构问题，这样相对简单的直角切削也因此被广泛地用于理论和实验的工作中。
刀具后刀面在切屑被去除的过程中不起作用；然而，后刀面与新加工工件表面所夹的夹角严重地增加了刀具的磨损率，这个角被定义为后角，或者，更确切地说，称为工作法向后角。
然而从图3.2可以看出，前角，后角和楔形角三者的和正好等于90°，这个楔形角包含了前刀面和后刀面所夹的夹角。
Lesson 2Production Turning Operations The era of modern machine tools is relatively recent,dating back to the Industrial Revolution in England.The first screw-cutting lathe was invented by Maudsley in 1798.The modern engine lathe takes its name from its gear-driven headstock that typically provides 16 spindle speeds.Although an engine lathe can bring one to four tools mounted in its one toolpost to bear on aworkpiece,it can provide only asingle feed motion at one time.A typical turned part frequently requires several operations,each of which needs adifferent tool and feed motion.The replacement and resetting of the tooling and handling of the work in and out of the machine adds asignificant cost to the finished part.Moreover,the cost per piece may be three to six times the cost of using amore specialized machine tool.When anumber of identical parts are needed,positioning of the tools for each operation not only involves time but may also result in workpieces that will not pass inspection.Thus,an engine lathe is suitable for low production only.
第二课车削加工
现代车床的年代并不遥远，可追溯到英国工业革命时期。世界上第一台螺纹切削车床是由莫兹利于1798年发明的。现代主轴车床得名于它的齿轮驱动主轴箱运动且具有典型的16种主轴速度。虽然一个车床的一个刀架在加工一个工件时可携带一至四把刀具，但在一段时间内它只能实现一次进给运动。一个典型的车削零件需反复加工多次才能完成，每一次加工都需要一把不同的刀具和进给运动。换刀和重新调刀以及工件的装卸都给工件增加了巨大的成本。此外，每一步所花费的成本可能会是使用一个更加专业化机床成本的三至六倍。当需要加工一定数目的相同零件时，对每一次加工的对刀和调刀来说不仅仅浪费时间而且还会导致很多工件不合格。因此，车床只适合于小批量生产。
Lesson 4Electrical-Discharge Machining Electrical-discharge machining(EDM),or spark machining,as it is also called,removes material with repetitive spark discharges from apulsating DC power supply,with adielectric flowing between the workpiece and the tool.
The principle of the EDM process is illustrated by the simplified diagram in Fig.3.17.The tool is mounted on the chuck attached to the machine spindle whose motion is controlled by aservo-controlled feed drive.The workpiece is placed in atank filled with adielectric fluid；a depth of at least 50mm over the work surface is maintained to eliminate the risk of fire.The tool and workpiece are connected to apulsating DC power supply.Dielectric fluid is circulated under pressure by apump,usually through ahole(or holes)in the tool electrode.A spark gap of about 0.025 to 0.05 mm is maintained by the servomotor.
第四课放电加工
放电加工(EDM)也叫电火花加工，顾名思义，它是通过从脉冲直流电源中反复的电火花释放来去除工件的材料的，且在工件与刀具之间有绝缘液体介质的存在。
放电加工过程的原理如图3.17所示的简图。装配在卡盘上的刀具，连接到机床主轴上，且机床主轴的运动是由伺服控制进给驱动的。工件被放置在一个充满了绝缘介质的槽箱中；要确保绝缘介质没过工件表面至少50毫米，以消除火灾隐患。将刀具和工件连接到脉冲直流电源的两端。绝缘介质是在一个泵的压力下开始循环的，通常经由刀具电极中的一个孔(或几个孔)中开始。火花的间隙大约是0.025至0.05毫米，是在伺服电机工作的状态下保证的。
Chapter Four Manufacturing Lesson 4Assembly After individual parts have been manufactured,they are assembled into aproduct.Assembly is an important phase of the overall manufacturing operation and requires consideration of the ease,speed,and cost of putting parts together.Many products are also designed so that they can be taken apart for maintenance and servicing.
There are several methods of assembly,each with its own characteristics and requiring different operations.The use of abolt and nut,for example,requires preparation of holes that must match in location and size.Hole generation requires operations such as dr