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2~5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5
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。
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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 7
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 Clamp used 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: α≤Φ1+Φ2 In 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 8
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