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密 级分类号编 号成 绩本科生毕业设计 (论文)外 文 翻 译原 文 标 题Precision Machining Technology 译 文 标 题精密机械加工工艺作者所在系别机电工程学院作者所在专业车辆工程作者所在班级作 者 姓 名作 者 学 号指导教师姓名指导教师职称副教授完 成 时 间2017年2月北华航天工业学院教务处制译文标题精密机械加工工艺原文标题Precision Machining Technology作 者Peter J. Hoffman译 名彼得J霍夫 曼国 籍美国原文出处Cengage Learning译文：精密机械加工工艺在机械加工过程中，工件受到切削力、离心力、惯性力等作用，为了保证在这些外力作用下，工件仍能在夹具中保持已由定位元件确定的加工位置，而不致发生振动或位移、夹具结构中应设置夹紧装置将工件可靠夹牢。 一、夹紧装置的组成 夹紧装置的种类很多，但其结构均由两部分组成。1 动力装置 夹紧力的来源，一是人力；二是某种装置所产生的力。能产生力的装置称为夹具的动力装置。常用的动力装置有：气动装置、液压装置、电动装置、电磁装置、气液联动装置和真空装置等。由于手动夹具的夹紧力来自人力，所以它没有动力装置。2 夹紧部分 接受和传递原始作用力使之变为夹紧力并执行夹紧任务的部分，一般由下列机构组成：1）接受原始作用力的机构。如手柄、螺母及用来连接气缸活塞杆的机构等。2）中间递力机构。如铰链、杠杆等。3）夹紧元件。如各种螺钉压板等。其中中间递力机构在传递原始作用力至夹紧元件的过程中可以起到诸如改变作用力的方向、改变作用力的大小以及自锁等作用。二、夹紧装置的基本要求 在不破坏工件定位精度，并保证加工质量的前提下，应尽量使夹紧装置做到：1. 夹紧力的大小适当。既要保证工件在整个加工过程中其位置稳定不变、振动小，又要使工件不产生过大的夹紧变形。2. 工艺性好。夹紧装置的复杂程度应与生产纲领相适应，在保证生产效率的前提下，其结构应力求简单，便于制造和维修。3. 使用性好。夹紧装置的操作应当方便、安全、省力。三、基本夹紧机构原始作用力转化为夹紧力是通过夹紧机构来实现的。在众多的夹紧机构中以斜楔、螺旋、偏心以及由它们组合而成的夹紧机构应用最为普遍。1. 斜楔夹紧机构采用斜楔作为传力元件或夹紧元件的夹紧机构称为斜楔夹紧机构。 直接采用斜楔夹紧时，斜楔的自锁条件是：斜楔的升角小于斜楔与工件、斜 楔与夹具体之间的摩擦角之和.即： 1+2为保证自锁可靠，手动夹紧机构一般取=68。用气压或液压装置驱动的斜楔不需要自锁，可取a =15 35 。斜楔夹紧具有结构简单，增力比大，自锁性能好等特点，因此获得广泛应用。（二）螺旋夹紧机构采用螺杆作中间传力元件的夹紧机构统称为螺旋夹紧机构。由于它结构简单、夹紧可靠、通用性好，而且由于螺旋升角小，螺旋夹紧机构的自锁性能好，夹紧力和夹紧行程都较大，是手动夹具上用得最多的一种夹紧机构。1. 简单螺旋夹紧机构 最简单的螺旋夹紧机构由于直接用螺钉头部压紧工件，易使工件受压表面损伤，或带动工件旋转。因此常在头部装有摆动的压块。由于压块与工件间的摩擦力矩大于压块与螺钉间的摩擦力矩，压块不会随螺钉一起转动。夹紧动作慢、工件装卸费时是单个螺旋夹紧机构的另一个缺点。为克服这一缺点，可采用快速夹紧机构。2. 螺旋压板夹紧机构在夹紧机构中，螺旋压板的使用非常普遍，常见的螺旋压板典型结构其结构尺寸均已标准化，设计者可参考有关国家标准和夹具设计手册进行设计。2. 偏心夹紧机构用偏心件直接或间接夹紧工件的机构，称为偏心夹紧机构。偏心件有两种形式，即圆偏心和曲线偏心，其中，圆偏心机构因结构简单、制造容易而得到广泛应用。偏心夹紧加工操作方便、夹紧迅速，缺点是夹紧力和夹紧行程都小。一般用于切削力不大、振动小、没有离心力影响的加工中。 1圆偏心轮的工作原理 2圆偏心轮的夹紧行程及工作段3.偏心轮的自锁条件max1+2 推导得： f1 2eD 当 f= 0.1 时，eD 20 当 f= 0.15 时，eD 14 四、定心夹紧机构 当工件被加工面以中心要素（轴线、中心平面等）为工序基准时，为使基准重合以减少定位误差，需采用定心夹紧机构。定心夹紧机构具有定心和夹紧两种功能，如卧式车床的三爪自定心卡盘即为最常用的典型实例。定心夹紧机构按其定心作用原理有两种类型，一种是依靠传动机构使定心夹紧元件等速移动，从而实现定心夹紧，如螺旋式、杠杆式、楔式机构等；另一种是利用薄壁弹性元件受力后产生均匀的弹性变形（收缩或扩张） ，来实现定心夹紧，如弹簧筒夹、膜片卡盘、波纹套、液性塑料等。1. 螺旋式定心夹紧机构螺杆两端的螺纹旋向相反，螺距相同。当其旋转时，使两个 V 形钳口作对向等速移动，从而实现对工件的定心夹紧或松开。V 形钳口可按工件不同形状进行更换。 这种定心夹紧机构的特点是：结构简单、工作行程大、通用性好，但定心精度不高，主要适用于粗加工或半精加工中需要行程大而定心精度要求不高的场合。2. 杠杆式定心夹紧机构 杠杆式三爪自定心卡盘中，滑套作轴向移动时，圆周均布的三个钩形杠杆便绕轴转动， 拨动三个滑块沿径向移动，从而带动其上卡爪将工件定心并夹紧或松开。这种定心夹紧机构具有刚性大、动作快、增力倍数大、工作行程也比较大等特点，但其定心精度较低。一般为 0.1mm 左右，它主要用于工件的粗加工。由于杠杆机构不能自锁，所以这种机构自锁要靠气压或其它机构。3. 楔式定心夹紧机构 机动的楔式夹爪自动定心机构中，当工件以内孔及左端面在夹具上定位后，汽缸通过拉杆使六个夹爪左移， 由于本体上斜面的作用，夹爪左移的同时向外胀开，将工件定心夹紧；反之，夹爪右移时，在弹簧卡圈的作用下使夹爪收拢，将工件松开。这种定心夹紧机构的结构紧凑，定心精度一般可达 0.02mm0.07mm，比较适用于工件内孔作定位基面的半精加工工序。 4. 弹簧筒夹式定心夹紧机构这种定心夹紧机构常用于安装轴套类工件。弹性定心夹紧机构的结构简单、体积小、操作方便迅速，因而应用十分广泛。其定心精度可稳定在 0.04mm0.010mm 之间。除上述介绍的定心夹紧机构外，常用的还有膜片卡盘机构、波纹套定心夹紧机构以及液性塑料夹紧机构等。夹具是机械加工中不可缺少的部件，在机床技术向高速、高效、精密、复合、智能、环保方向发展的带动下，夹具技术正朝着高精、高效、模块、组合、通用、经济方向发展。一、 高精随着机床加工精度的提高，为了降低定位误差，提高加工精度对夹具的制造精度要求更高高精度夹具的定位孔距精度高达0.5mm，夹具支撑面的垂直度达0.01mm/300mm，平行度高达 0.01mm/500mm。瑞士EROWA柔性夹具的重复定位精度高达25微米。机床夹具的精度已提高到微米级，世界知名的夹具制造公司都是精密机械制造企业。为了适应不同行业的需求和经济性，夹具有不同的型号以及不同档次的精度标准供选择。二、 高效 为了提高机床的生产效率，双面、四面和多件装夹的夹具产品越来越多。为了减少工件的安装时间，各种自动定心夹紧、精密平口钳、杠杆夹紧、凸轮夹紧、气动和液压夹紧等，快速夹紧功能部件不断的推陈出新。新型的电控永磁夹具，夹紧和松开工件只用1、2秒，夹具结构简化，为机床进行多工位、多面和多件加工创造了条件。采用美国杰金斯公司的球锁装夹系统，1分钟内就能将夹具定位和锁紧在机床工作台上，球锁装夹系统用于柔性生产线上更换夹具，起到缩短停机时间，提高生产效率的作用。三、 模块 组合夹具元件模块化是实现组合化的基础。利用模块化设计的系列化、标准化夹具元件，快速组装成各种夹具，已成为夹具技术开发的基点。省工、省时、节材、节能，体现在各种先进夹具系统的创新之中。模块化设计为夹具的计算机辅助设计与组装打下了基础。应用CAD技术，可建立元件库、典型夹具库、标准和用户使用档案库，进行夹具优化设计，为用户三维实体组装夹具。模拟仿真刀具的切削过程，既能为用户提供正确、合理的夹具与元件配套方案，又能积累使用经验，了解市场需求，不断的改进和完善夹具系统。 四、 通用 经济夹具的通用性直接影响其经济性。采用模块、组合式的夹具系统，一次性投资比较大，只有夹具系统的可重组性、可重构性及可扩展性功能强，应用范围广，通用性好，夹具利用率高，收回投资快，才能体现出经济性好。附录：Cengage Learning In the machining process the work piece by the cutting force, centrifugal force, inertia force, such as the role of, in order to ensure that these external force, the workpiece can remain in the fixture by the positioning of the processing to determine the location of components, and should be no vibration or displacement, fixture structure should be set up reliable work piece clamping device folder will be in prison. First, the composition of clamping devices. Many different types of clamping devices, but their structures are composed of two parts. 1. Power plant The source of clamping force, one human; second is generated by a power device.The device can generate power as the power unit fixture. Commonly used in power plant are: pneumatic devices hydraulic devices electrical devices electromagnetic devices gas - liquid interaction devices and vacuum devices. Fixture as a result of manual clamping force from the human so it does not power plants. 2. Clamping part Receive and impart into the original clamping force to clamp the task force and part of the implementation of the general composition of the following agencies: 1) to accept the original force of bodies. Such as handles nuts and used to connect the institutions such as cylinder piston rod. 2) Force the middle of delivery. Such as hinges levers and so on. 3) Clamping components. Such as plate such as screws. Force delivery of them in the middle of the original transmission of force to the process of clamping devices can play such as changes in the direction of force to change the size of forces as well as the role of self-locking and so on. Second the basic requirements for clamping device Without damaging the work piece positioning accuracy and quality assurance process under the premise of clamping devices should be enabled to: 1. The size of the appropriate clamping force. It is necessary to ensure that the work piece in the whole process of its stable position vibration small but also so that the work piece does not produce excessive clamping deformation. 2. Technology is good. The complexity of the clamping device should be suited to the production of the Program to ensure production efficiency its structure should be kept simple easy to manufacture and maintenance. 3. Good use. The operation of clamping device should be convenient safe and labor-saving. Third the basic Clamp iginal force into a clamping force through the clamping body to achieve.Among the many institutions in the clamping wedge oblique spiral and by their eccentric combination of the most common application of clamping.(A) Wedge Clampused as components or transmission of the clamping device clamping body known as the Wedge Clamp.Wedge clamping directly the oblique wedge of the self-locking conditions are:Wedge angle smaller than the work piece Wedge Wedge and folders between the concrete and the friction angle. Namely: 1+2In order to ensure a reliable self-locking manual clamping generally take a =6 8 . Using pneumatic or hydraulic device drivers do not need the self-locking oblique wedge it is desirable to a =15 35 . Wedge clamp is simple in structure than by large self-locking features such as performance it is widely available.(B) Helical Clamp Used as intermediate screw transmission components are collectively referred to as the clamping screw clamping body organs. Because of its simple structure reliable clamping common good and as a result of the small helix angle spiral of self-locking clamping body good clamping force and the clamping itinerary are larger fixture on manual with the most a clamping body.1. Simple screw clamp bodyThe simplest spiral as a result of the direct use of clamping bodies pressed workpiece screw head so easy to damage the surface of the work piece under pressure or driven rotating work piece. So often in the head with swinging Press. Press with the work piece as a result of friction between the Press and the torque is greater than the friction between the screw torque screw together with the Press will not rotate. Clamping action slow time-consuming loading and unloading the work piece is a single spiral Another drawback of the Clamp. To overcome this shortcoming the rapid clamping bodies can be.2. Clamp screw plateInstitutions in the clamping the use of spiral plate is very common common structure of the spiral structure of a typical plate size has been standardized the designer can refer to the relevant national standards and fixture design manual design. (C) Eccentric Clamp With eccentric pieces, directly or indirectly, the work piece clamping body, known as the eccentric clamping body. There are two types of eccentric pieces, that is, and the curveof eccentricity eccentric circle, which, due to a round eccentric structure is simple and easy to manufacture and is widely used. Eccentric clamping processing is easy to operate, rapid clamp, the disadvantage of clamping force and clamping trip are small. Not generally used in cutting force, vibration small there is no centrifugal force of the impact of the processing. 1. Round the working principle of eccentric 2. Eccentric clamping round trip and paragraph 3. Eccentric self-locking condition of max1+2 Was derived: f1 2e / D When f =0.1 hours, e / D 20, when f =0.15 pm, e / D 14 Fourth institutions centering clampingWhen the work piece is processed by the central element of surface (axis, the center plane, etc.) for the base process in order to enable the base to reduce the positioning error of coincidence to be used centering clamping body. Centering centering clamping body and clamping the two functions such as horizontal self-centering three-jaw lathe chuck is a classic example of the most commonly used. Centering centering clamping the role of institutions according to their principle, there are two types, one is relying on the transmission mechanism so that mobile speed centering clamping device in order to achieve centering clamping, such as spiral leveraged institutions such as wedge; the other is the use of thin-walled elastic element force even after the elastic deformation (contraction or expansion), to achieve centering clamping, such as a spring clip drum, diaphragm chuck, bellows units, such as liquid plastic.1. Centering clamping body spiralRotary screw thread at both ends to the contrary, the same pitch. When it spins, the two V-shaped gag against the constant movement in order to achieve the centering of the work piece clamping or release. V-shaped work pieces of different shapes can shut up the replacement. Centering clamping bodies such features are: simple structure the work trip and general good but the centering accuracy is not high mainly suitable for rough or semi-finished tour of the needs of large and less demanding precision centering occasions. 2. Leveraged institutions centering clamping Three-jaw self-centering leveraged trading cards, sleeve for axial movement the circle are three fabric hook lever will rotate around the axis, the three struck the slider along the radial movement of the cards in order to promote its claws the work piece centering and clamping or release. This centering clamping rigid body, and move fast, by force multiplier, and the worktrip is also characterized by relatively large, but its relatively low precision centering. Generally about 0.1mm it is mainly used for rough work. Since the body can not self-locking lever, so that organizations rely on self-locking air pressure or other agencies. 3. Centering clamping wedge bodies Wedge mobile folder automatically centering body claw when the work piece surface within the hole and left the position in the fixture after the six-cylinder through the rod so that the left claw clip due to the role of ontology on the slope while the left claw folder to the opened outside the bulge will be centering the workpiece clamping the other hand claw shifted to right folder in the role of spring circle card folder under claw to release the work piece. Centering clamping bodies such compact structure usually ranging from precision centering 0.02mm 0.07mm compared with the hole for the workpiece surface for positioning the base of the semi-finishing processes.4. Clip-on spring-centering clamping cylinder body This centering clamping sleeve body type commonly used in the installation of the work piece. Elastic centering clamping simple structure, small size, easy to operate quickly, so a wide range of applications. Centering accuracy of its stability in between0.04mm 0.010mm. In addition to the above described centering clamping bodies, are commonly used diaphragm chuck body, corrugated centering clamping sets of institutions, as well as fluid bodies such as plastic clamping. Machining fixture is an indispensable component in the machine tool technology to high-speed, high efficiency, precision, complex, intelligent, environmentally-friendly direction, driven by technology is moving fixture high-precision, high-performance, modular, mix, general economic direction. First, high-precision Machining with improved accuracy, in order to reduce the positioning error and improve machining accuracy of the fixture manufacturing precision demanding high-precision positioning jig Distance accuracy up to 5m the bearing surface of the vertical fixture achieve 0.01mm / 300mm up to parallelism0.01mm/500mm. Switzerland duplication EROWA Flexible fixture positioning accuracy of up to 2 5m. Precision machine tool fixture to the micron level has been raised the worlds leading manufacturer of fixture is precision machinery manufacturing enterprises. It is true that, in order to meet the needs of different industries and economy, folders with different models, as well as the different grades for the accuracy of the standard options. Second, efficient tool To improve production efficiency, double-sided, four and more than clamping fixture of more and more products. Work piece in order to reduce the installation time, all kinds of auto-centering clamping, precision flat clamp, clamping levers, cam clamp, such as pneumatic and hydraulic clamping, rapid clamping new features constantly. New type of electronically controlled permanent magnet fixture, step up and release the work piece only 12 seconds, simplifying the fixture structure for the machine to carry out stage, faceted and processing to create the condition. American JERGENS the companys ball lock clamping system,1 minutes, will be able to locate and lock fixture in the machine tool table, the ball lock clamping system of flexible production line for the replacement of fixtures, played reduce downtime and increase the role of productivity. Third, modules Modular components of modular fixture is the basis of the realization of portfolio. Take advantage of the modular design of serialization, standardization fixture elements, quickly assembled into a variety of fixtures, has become a fixture technology development basis points.Save labor, time, materials, energy-saving, being reflected in a variety of advanced fixture system innovation. The modular design laid the foundation for the the fixture computer-aided design and assembly. Application of CAD technology to create a component library the typical fixture library, standard and user archive fixture optimization design, assembly fixtures for users dimensional solid. Cutting process simulation tool, both to provide users with the correct fixtures and components supporting the program, but also the accumulation of experience, understand the market demand, and continue to improve and perfect the fixture system. Fourth, GM Economic fixture versatility direct impact on the economy. Modules, modular fixture system, a one-time investment is relatively large, the only fixture system reconfigurable and scalability features a wide range of applications, common good, fixture utilization, faster recovery of investment to reflect the economic good. 13指 导 教 师 评 语 外文翻译成绩：指导教师签字： 年 月 日注：1. 指导教师对译文进行评阅时应注意以下几个方面：翻译的外文文献与毕业设计（论文）的主题是否高度相关，并作为外文参考文献列入毕业设计（论文）的参考文献；翻译的外文文献字数是否达到规定数量（3 000字以上）；译文语言是否准确、通顺、具有参考价值。2. 外文原文应以附件的方式置于译文之后。
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