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外筒工艺及磨床夹具设计【2张CAD图纸】【优秀】

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关键词：: 外筒工艺磨床夹具设计 cad图纸

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外筒工艺及磨床夹具设计

35页 11000字数+说明书+任务书+外文翻译+2张CAD图纸【详情如下】

任务书.doc

外文翻译--基本加工工序和切削技术.doc

外筒工艺及磨床夹具设计答辩稿.ppt

外筒工艺及磨床夹具设计论文.doc

外筒零件图.dwg

工艺卡.doc

工艺卡片.doc

磨床夹具装配图.dwg

摘要

本次设计内容涉及了机械制造工艺及机床夹具设计、公差配合与测量等多方面的知识。通过对知识的综合运用，设计了外筒零件的加工工艺规程及夹具的设计。外筒加工工艺规程及磨床的夹具设计包括零件加工的工艺设计、工序设计以及磨床夹具的设计三部分。在工艺设计中要首先对外筒零件进行分析，了解外筒零件的工艺再设计出毛坯的结构，并选择好外筒零件的加工基准，设计出外筒零件的工艺路线；接着对外筒零件各个工步的工序进行尺寸计算，关键是决定出各个工序的工艺装备及切削用量；然后重点进行磨床夹具的设计，磨床夹具设计的要点，选择设计出夹具的各个组成部件，如夹紧元件、引导元件、夹具体与机床的连接部件以及其它部件；计算出夹具定位时产生的定位误差，分析夹具结构的合理性与不足之处，并在以后设计中注意改进。设计磨床夹具是为了生产过程中能方便快捷的完成磨平面工序的加工，从而提高生产效率。通过夹具设计掌握所学的机械知识，使之相互联系，进一步使理论和实践相结合，并巩固了知识点。

关键词:外筒零件，工艺规程，磨床夹具

ABSTRACT

The design content of the mechanical manufacturing technology and machine tool fixture design, tolerance matching and measurement of aspects of knowledge. Through the integrated use of knowledge, design of the outer barrel parts machining process planning and fixture design. External processing technical process and grinding machine of fixture design including parts processing process design, process design and grinding machine fixture design three parts. Must first foreign tube parts in process design were analyzed, and the outer tube parts technology to design the structure of blank, and choose good outer barrel parts processing benchmark, sticking out of the barrel parts design process; Then foreign tube parts size of each work step of the process, the key is to determine the process equipment for each process and cutting parameter; Then the grinding machine fixture design, the main points of the grinding machine fixture design, select design out of the component parts of the fixture, such as clamping components and guide components, clip specific connection with machine parts and other parts; Calculated at the exit of fixture locating position error, analysis the rationality of the fixture structure and deficiency, and pay attention to the improvement in the later design. Grinding machine fixture is designed to process that can be convenient and quick plane grinding process to complete the processing, thus improve the production efficiency. Through the knowledge of the mechanical fixture design master what they have learned, to connect with each other, further to combine theory and practice, and consolidate the knowledge.

Key words：Outside the cylinder,Process planning,Grinding machine fixture

第一章绪论1

第二章工艺方案分析2

2.1 外筒的零件图的分析2

2.1.1 外筒零件结构特点3

2.1.2 外筒零件的作用3

2.1.3 外筒零件的工艺分析3

第三章外筒零件的工艺规程设计4

3.1 确定毛坯4

3.1.1 毛坯的选择4

3.1.2 绘制毛坯图5

3.2 拟定工艺路线5

3.2.1 各表面加工方法5

3.2.2 定位基准的选择16

3.2.3 加工阶段的划分17

3.2.4 工序的集中与分散17

3.2.5 热处理工序的安排18

3.2.6 辅助工序的安排19

3.2.7 重要工序的分析19

3.3 加工余量的确定21

3.4 尺寸链计算22

第四章外筒零件磨平面工序的磨床夹具设计24

4.1 定位装置的设计24

4.2 夹紧装置的设计24

4.3 绘制夹具总图25

4.4 夹具操作过程简述25

4.5 夹具精度校核25

第五章结论27

参考文献28

致谢29

毕业设计小结30

附录31

第一章绪论

机械制造业是制造具有一定形状位置和尺寸的零件和产品，并把它们装备成机械装备的行业。机械制造业的产品既可以直接供人们使用，也可以为其它行业的生产提供装备，社会上有着各种各样的机械或机械制造业的产品。我们的生活离不开制造业，因此制造业是国民经济发展的重要行业，是一个国家或地区发展的重要基础及有力支柱。从某中意义上讲，机械制造水平的高低是衡量一个国家国民经济综合实力和科学技术水平的重要指标。机械加工（简称“机加”）是制造技术中的重要组成部分。随着我国经济不断发展，产业结构的调整，企业改革不断深化。目前，我国制造技术水平与先进国家相比还有较大差距，为适应我国工业发展，在总结经验和加强基础研究上都加大投入，提高加工工艺水平，成为发展工业的重要环节之一。

随着近年来科学技术以及工业经济的飞速发展，合金结构钢的需求日益增多，使合金结构钢的加工性研究也随之深入。合金结构钢的广泛应用促进了合金结构钢加工技术的发展，同时加工技术的发展又拓展了合金结构钢的应用领域，因此合金结构钢的加工技术正成为研究的热点之一。而在对合金结构钢材料进行加工的过程中有许多内容值得我们进行探究，例如加工温度、切削表面、切削内应力等等。

本文的主要内容是外筒零件的加工工艺与磨床夹具设计。它的整个加工过程中涉及到毛坯的选择、加工余量的计算、工艺路线的确定、机床夹具定位装置的设计和辅助工序的选择等内容。叙述了外筒零件机械加工工艺过程，从以下几个方面展开研究：

1.外筒零件的结构特点和工艺分析；

2.零件的工艺规程设计；

3.加工中刀具的选择及应用；

4.夹具的设计及注意事项。2.1.1外筒零件结构特点

该零件是薄壁零件，原材料为无发纹钢，左右对称，中间钻有中心孔，表面粗糙度要求为Ra3.2，表面的位置精度：心轴的跳动量不大于0.05mm，外圆的椭圆度和锥度不大于0.03mm，端面K对内孔A的跳动量不大于0.01mm的外筒装置用做承受巨大冲击力。

2.1.2 外筒零件的作用

本零件为某助力器的外筒。它里面装的是活塞与活塞一起组成执行机构。外筒的两轴劲与飞机的方向舵操纵系统相连接，帮助驾驶员用较小的力量去操纵笨重的操纵面。

2.1.3外筒零件的工艺分析

设计零件的机械加工工艺过程，是生产技术准备工作的一个重要组成部分。外筒零件可以采用不同的工艺过程制造出来，但是正确合理的工艺过程，应满足下列基本要求：

（1）保证产品的质量符合设计图和技术条件所规定的要求；

（2）保证劳动高的生产率；

（3）保证经济的合理性；

　　　从零件的结构和基本功能来看，为保证内外圆的同轴度和两端面平行度要求，外筒零件的加工应采取互为基准和反复加工的原则。其基本工艺过程是粗车外圆及端面→调头粗车另一端面及外圆→钻孔、扩孔→热处理→精车→磨平面→磨内孔。

第二章外筒零件的工艺规程设计

3.1 确定毛坯

3.1.1毛坯的选择

毛坯的种类和制造方法对零件的加工质量、生产率、材料消耗及加工成本都有影响。选择合适毛坯，可减少机械加工的劳动量，提高材料利用率，降低机械加工成本，但毛坯制造成本增加，两者是相互矛盾的。

选择毛坯时，应考虑现有生产条件，如现有毛坯的制造水平和设备情况，外协的可能性等。随着毛坯制造专业化生产的发展，目前毛坯制造方面的新工艺、新技术和新材料的应用越来越多，如精铸、精锻、冷轧、冷挤压、粉末冶金和工程塑料的应用日益广泛，这些方法可大大减少机械加工量，节约材料，有十分显著的经济效益，我们在选择毛坯时，应充分考虑，在可能的条件下，尽量采用零件上的尺寸公差、形位公差和表面粗糙度的标注，应根据零件的功能和经济合理地决定。过高的要求会增加加工难度，过低的要求会影响工作性能，两者都是不允许的。

目前，材料的选择既要满足产品的使用要求，又要考虑产品成本，尽可能采用常用材料，机械加工零件的毛坯种类通常有以下几种：铸件、锻件、型材、焊接件、其它毛坯，其中：

铸件：适合做形状复杂零件的毛坯；

锻件：适合做受力复杂的重要零件的毛坯；

型材：适合做精度要求较高的中小型零件的毛坯；

焊接件：适合做单件小批生产和大型零件及样机试制的毛坯。

根据外筒的作用以及其尺寸较小、形状简单，大批量生产的要求，所以最好选模锻件，根据设计图要求，表面硬度35-45HB，选Ф89.5×371.2的30CrMnSiA毛坯。　　　选用井式炉，表面P和Q发蓝，其他Ra0.8

　　　工序140-最终检验。

按零件图的尺寸及要求检验。

3.2.2 定位基准的选择

在设计工艺路线时，最重要的问题之一要考虑位置精度保证问题。为保证位置精度一般常采用以下四种方法：

a、一次安装

在一次安装的条件下，可以保证有较高的位置精度因为一次安装时所加工的各表面的位置精度主要取决于设备的精度。而与定位误差定位基准误差无关。

b、互为基准

有位置精度要求的两个表面，在加工时，用其中任何一个表面作为定位基准来加工另一个表面.用这种方法来保证位置精度，称为互为基准。

c、同一基准

有位置精度要求的两个表面，在加工时，都采用另一个表面作为定位基准。用这两种方法保证这两个表面间的位置精度，称为同一基准法。

d、不同基准

有位置精度要求的两个表面，在加工时。采用两个不同的表面，作为各自的定位基准。这种方法，称为不同基准法。

　　根据以上原则，粗基准：以外圆柱面为粗基准；

精基准：以外圆、内孔和端面为精基准。

所以外筒零件选择端面销钉定位和侧平面定位。

3.2.3 加工阶段的划分

1．基面先行原则

用作精基准的表面，应优先加工。因为定位基准的表面越精确，装夹误差就越小，所以任何零件的加工过程，总是先对定位基准面进行粗加工和半精加工，必要时还要进行精加工。

2．先粗后精原则

各个表面的加工顺序一般是按照粗加工——半精加工——精加工——光整加工的顺序进行，这样才能逐步提高加工表面的精度和减少表面粗糙度。

3．先主后次原则

零件上的工作面及装配精度要求较高的表面，属于主要表面，应先加工。自由表面、键槽、紧固用的螺孔和光孔等表面，精度要求较低，属于次要表面，可穿插进行，一般安排在主要表面达到一定精度后，最终精加工之前加工。

4．先面后孔原则

　　　对于箱体类、支架类、机体类的零件，一般先加工平面，后加工孔。这样安排加工顺序，一方面是用加工过的平面定位，稳定可靠；另一方面是在加工过的平面上加工孔，比较容易，并能提高孔的加工精度。

根据外筒零件加工工序的过程，确定在工序5-10为粗加工阶段，工序25-30为半精加工阶段，工序50为精加工阶段。

3.2.4 工序的集中与分散

在设计工艺路线时，当选定了各表面的加工方法和确定了阶段划分以后，就可将同一阶段中的个加工表面组合成若干工序，组合时可采用集中或分散的原则。

1、工序集中的特点：

（1）采用高效专用设备及工艺装备，生产率高；

（2）工件装夹次数减少，易于保证表面间位置精度，还能减少工序间运输量，缩短生产周期；

（3）工序数目少，可减少机床数量、操作工人和生产面积，还可简化生产计划和组织工作。

2、工序分散的特点：

（1）设备及工艺装备比较简单，调整和维修方便，工人容易掌握，生产准备工作量少，又易于平衡工序时间，易适应产品更换；

（2）可采用最适合的切削用量，减少基本时间；

（3）设备数量多，操作工人多，占用生产面积大。

工序集中与工序分散各有利弊，应根据生产类型，现有生产条件，工件结构特点和技术要求等，进行综合分析后选用，因此，对于产量较小时，为简化计划、调度等工作，选取工序集中原则，较便于组织生产。对于钢性较差且精度要求高的精密工件，则工序应适当分散，对尺寸和重量大的工件，由于安装和运输困难，一般宜采用工序集中原则组织生产。

因此外筒零件的加工批量大，结构和各个加工面的加工，需要不同的加工方法和不同的夹具，不能将多个加工面放在同一道工序中进行加工，所以选用工序分散原则。

3.2.5热处理工序的安排

为了提高材料的力学性能，改善材料的切削加工性和消除工件内应力，在工艺过程中要适当安排一些热处理工序。

⑴改善工件材料切削加工性能的热处理（如退火、正火、调质等），一般安排在切削加工之前。

⑵为了消除内应力而进行的热处理（如人工时效、退火、正火等），最好安排在粗加工之后。有时为减少运输工作量，对精度要求不太高的零件，把去除内应力的人工时效或退火安排在切削加工之前（即在毛坯车间）进行。

⑶为了改善材料的力学物理性能，半精加工之后，精加工之前常安排淬火、渗碳淬火等热处理工序。对于整体淬火的零件，淬火前应将所有切削加工的表面

进行完。对于那些变形较小的热处理（如高频感应加热淬火、渗氮），有时允许安排在精加工之后。

⑷对于高精度精密零件（如铰刀、精密丝杠、精密齿轮等），在淬火后安排冷处理（使零件在低温介质中继续冷却到零下80℃）以稳定零件的尺寸。

所以在外筒加工工序过程中，热处理安排在工序45，采用井式炉，淬火并回火，确保表面硬度HRC=35~45。

3.2.6 辅助工序的安排

外筒零件工序40和工序140检验工序是主要的辅助工序，它是保证产品质量的主要措施。除了在每道工序的进行中，操作者都必须自行检验外，还应在下列情况下安排单独的检验工序：

⑴粗加工阶段结束之后；

⑵重要工序之后；

⑶零件从一个车间转到另一个车间时；

⑷特种性能（磁力探伤、密封性等）检验之前；

⑸零件全部加工结束之后。

除检验工序外，还要在相应的工序后面考虑安排去毛刺、倒棱边、去磁、清洗、涂防锈油等辅助工序。应该认识到辅助工序仍是必要的工序，缺少了辅助工序或是对辅助工序要求不严，将会给装配工作带来困难，甚至使零件不能使用。例如，液压助力器外筒未去净毛刺和锐边，将使外筒不能装配在液压助力器上，且将危及工人的安全。

3.2.7 重要工序的分析

1、工序的分类

在产品质量的形成过程中包括多个工序过程，其定义分为三类：

（1）一般工序：对产品形成质量起一般作用的工序；

（2）关键工序：对产品形成质量，特别是关键性能质量起至关重要作用的工序；

（3）特殊工序：其结果不能通过后面的检验和试验，而只能通过使用后才能完全验证的工序。

工序质量控制是过程质量控制的基本点，是现场质量控制的重要内容。工序质量控制，是在加强一般工序质量控制的同时，采取有效的控制方法，对关键工　　　本次设计是对外筒零件的加工工艺规程及一些专用夹具(磨床)设计，要求绘制零件图、毛坯图、工艺图、夹具装配图、夹具部分零件图。它的制造及相关夹具设计涉及到机械制造专业多方面的内容包括从毛坯的选择、选择生产类型、零件的结构工艺性分析、零件的加工工艺路线、零件的加工方法的确定、加工阶段的划分、加工顺序的安排、设备及工艺装备的选择、加工余量的确定、工序尺寸公差的确定等等方面考虑，同时还要考虑机械加工生产率和技术经济性分析。该文从零件分析，工艺规程的设计，机械加工余量、工序尺寸及毛坯尺寸的确定，专用夹具设计四个方面对工艺路线及平面磨床夹具的设计做了详细的阐述。

本设计论文虽然基本满足生产要求，但自动化程度、生产效率低，耗时耗力由于所学知识和时间有限，加上缺乏实践经验，在设计写作过程中难免出现错误，不足之处敬请老师批评指正。

参考文献

[1] 闫光明，侯忠滨，张云鹏。现代制造工艺基础[M]西安：西北工业大学出版社，2007.

[2] 狄瑞坤，潘晓弘，樊晓燕。机械制造工程[M]杭州：浙江大学出版社。2001.

[3] 薛源顺，机床夹具设计[M]北京：机械工业出版社，2000

[4] 许建新，孔宪光，张振明，CAPP技术综述[J]CAD/CAM与制造业信息化。2002.

[5] 蔡瑾，段国林，李翠玉，李德红，夹具设计技术发展综诉[J]河北工业大学报，2002.

[6] 魏米，吴大春，机械加工工艺路线的拟定[J]，民营科技，2008.

[7] 曾爱新，浅谈机械加工工艺的发展趋势[J]，职培园地，2002。

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内容简介：: 设计论文毕业任务书一、题目外筒工艺及磨床夹具设计二、指导思想和目的要求机械加工工艺与夹具设计是全面地综合运用有关专业课程的理论和实践知识进行加工工艺及夹具结构设计的一次重要实践。毕业设计（论文）是培养自学能力、综合应用能力、独立工作能力的重要教学实践环节。在毕业设计中，独立承担一部分比较完整的工程技术设计任务。发挥主观能动性，积极性和创造性，在毕业设计中着重培养独立工作能力和分析解决问题的能力，严谨踏实的工作作风，理论联系实际，以严谨认真的科学态度，进行有创造性的工作，认真、按时完成任务。三、主要技术指标 1. 机械中英文材料 2. 外筒的CAD制图 3. 外筒加工工艺过程综合卡 4. 磨床夹具设计图 5. 设计论文四、进度和要求第一阶段：第八学期第1，2周，完成零件CAD制图，撰写开题报告第二阶段：第八学期第3，4周，修改并完成文献综诉与译文，；第三阶段：第八学期第5，6周，外筒工艺设计的初步思想；第四阶段：第八学期第7，8周，研读工艺规程设计资料，制定零件加工工艺规程；第五阶段：第八学期第9，10周，磨床夹具设计与计算，绘制制定零件图；第六阶段：第八学期第11，12周，完善磨床夹具设计，画出夹具装配图。第七阶段：第八学期第13，14周，拟定毕业设计论文框架，整理和撰写设计论文，形成终稿，送审，修改，并装订。五、主要参考书及参考资料1 闫光明,侯忠滨,张云鹏.现代制造工艺基础M西安:西北工业大学出版社,2007.2 狄瑞坤,潘晓弘,樊晓燕.机械制造工程M杭州：浙江大学出版社.2001.3 薛源顺,机床夹具设计M北京：机械工业出版社.20004 许建新,孔宪光,张振明,CAPP技术综述JCAD/CAM与制造业信息化.2002.5 蔡瑾,段国林,李翠玉,李德红,夹具设计技术发展综诉J河北工业大学报，2002.6 魏米,吴大春,机械加工工艺路线的拟定J,民营科技,2008.7 曾爱新,浅谈机械加工工艺的发展趋势J,职培园地,2002.西北工业大学明德学院本科毕业设计论文原文：Basic Machining Operations and Cutting TechnologyBasic Machining Operations Machine tools have evolved from the early foot-powered lathes of the Egyptians and John Wilkinsons boring mill. They are designed to provide rigid support for both the workpiece and the 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 form of a severely deformed chip. The 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 workpiece depends on the shape of the tool and its path during the machining operation. Most machining operations produce parts of differing geometry. If a rough cylindrical workpiece revolves about a central axis and the 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 machined on the inside in a similar manner, the operation is called boring. Producing an external conical surface uniformly varying diameter is called taper turning, if the tool point travels in a path of varying radius, a contoured surface like that of a 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 surfaces 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 hold the workpiece steady and reciprocate the tool across it in a 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 workpiece may be in any of the three coordinate directions. Basic Machine Tools Machine tools are used to produce a part of a specified geometrical shape and precise I size by removing metal from a ductile material in the form of chips. The latter are a waste product and vary from long continuous ribbons of a ductile material such as steel, which are undesirable from a disposal point of view, to easily handled well-broken chips resulting from cast iron. Machine tools perform five basic metal-removal processes: I 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 modify drilled holes and are related to drilling; bobbing and gear cutting are fundamentally milling operations; hack sawing and broaching are a form 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: 1. lathes, 2. planers, 3. drilling machines, and 4. milling machines. 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 I large, as in heavy turning operations, or extremely small, as in lapping or super finishing operations where only the high spots of a surface are removed. A machine tool performs three major functions: 1. it rigidly supports the workpiece or its holder and the cutting tool; 2. it provides relative motion between the workpiece and the cutting tool; 3. it provides a range of feeds and speeds usually ranging from 4 to 32 choices in each case. Speed and Feeds in Machining Speeds, feeds, and depth of 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 depth of cut, feed, and cutting speed are machine settings 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 performed on an engine lathe are illustrated. Those operations performed on external surfaces with a single point cutting tool are called turning. Except for drilling, reaming, and lapping, the operations on internal surfaces are also performed by a single point cutting tool. All machining operations, 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 ends 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 the 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 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 results 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 a driver plate mounted on the spindle nose. One end of the Workpiece is mecained;then the workpiece can be turned around in the lathe to machine the 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 removed 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 chucks. While very large diameter workpieces 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. Introduction of Machining Machining as a shape-producing method is the most universally used and the most important of all manufacturing processes. Machining is a shape-producing process in which a power-driven device causes material to be removed in chip form. Most machining is done with equipment that supports both the work piece and cutting tool although in some cases portable equipment is used with unsupported workpiece. Low setup cost for small Quantities. Machining has two applications in manufacturing. For casting, forging, and press working, each specific shape to be produced, even one part, nearly always has a high tooling cost. The shapes that may he produced by welding depend to a large degree on the shapes of raw material that are available. By making use of generally high cost equipment but without special tooling, it is possible, by machining; to start with nearly any form of raw material, so tong as the exterior dimensions are great enough, and produce any desired shape from any material. Therefore .machining is usually the preferred method for producing one or a few parts, even when the design of the part would logically lead to casting, forging or press working if a high quantity were to be produced. Close accuracies, good finishes. The second application for machining is based on the high accuracies and surface finishes possible. Many of the parts machined in low quantities would be produced with lower but acceptable tolerances if produced in high quantities by some other process. On the other hand, many parts are given their general shapes by some high quantity deformation process and machined only on selected surfaces where high accuracies are needed. Internal threads, for example, are seldom produced by any means other than machining and small holes in press worked parts may be machined following the press working operations.Primary Cutting ParametersThe basic tool-work relationship in cutting is adequately described by means of four factors: tool geometry, cutting speed, feed, and depth of cut. The cutting tool must be made of an appropriate material; it must be strong, tough, hard, and wear resistant. The tool s geometry characterized by planes and angles, must be correct for each cutting operation. Cutting speed is the rate at which the work surface passes by the cutting edge. It may be expressed in feet per minute. For efficient machining the cutting speed must be of a magnitude appropriate to the particular work-tool combination. In general, the harder the work material, the slower the speed. Feed is the rate at which the cutting tool advances into the workpiece. Where the workpiece or the tool rotates, feed is measured in inches per revolution. When the tool or the work reciprocates, feed is measured in inches per stroke, Generally, feed varies inversely with cutting speed for otherwise similar conditions. The depth of cut, measured inches is the distance the tool is set into the work. It is the width of the chip in turning or the thickness of the chip in a rectilinear cut. In roughing operations, the depth of cut can be larger than for finishing operations. The Effect of Changes in Cutting Parameters on Cutting Temperatures In metal cutting operations heat is generated in the primary and secondary deformation zones and these results in a complex temperature distribution throughout the tool, workpiece and chip. A typical set of isotherms is shown in figure where it can be seen that, as could be expected, there is a very large temperature gradient throughout the width of the chip as the workpiece material is sheared in primary deformation and there is a further large temperature in the chip adjacent to the face as the chip is sheared in secondary deformation. This leads to a maximum cutting temperature a short distance up the face from the cutting edge and a small distance into the chip. Since virtually all the work done in metal cutting is converted into heat, it could be expected that factors which increase the power consumed per unit volume of metal removed will increase the cutting temperature. Thus an increase in the rake angle, all other parameters remaining constant, will reduce the power per unit volume of metal removed and the cutting temperatures will reduce. When considering increase in unreformed chip thickness and cutting speed the situation is more complex. An increase in undeformed chip thickness tends to be a scale effect where the amounts of heat which pass to the workpiece, the tool and chip remain in fixed proportions and the changes in cutting temperature tend to be small. Increase in cutting speed; however, reduce the amount of heat which passes into the workpiece and this increase the temperature rise of the chip m primary deformation. Further, the secondary deformation zone tends to be smaller and this has the effect of increasing the temperatures in this zone. Other changes in cutting parameters have virtually no effect on the power consumed per unit volume of metal removed and consequently have virtually no effect on the cutting temperatures. Since it has been shown that even small changes in cutting temperature have a significant effect on tool wear rate it is appropriate to indicate how cutting temperatures can be assessed from cutting data. The most direct and accurate method for measuring temperatures in high -speed-steel cutting tools is that of Wright &. Trent which also yields detailed information on temperature distributions in high-speed-steel cutting tools. The technique is based on the metallographic examination of sectioned high-speed-steel tools which relates microstructure changes to thermal history. Trent has described measurements of cutting temperatures and temperature distributions for high-speed-steel tools when machining a wide range of workpiece materials. This technique has been further developed by using scanning electron microscopy to study fine-scale microstructure changes arising from over tempering of the tempered martens tic matrix of various high-speed-steels. This technique has also been used to study temperature distributions in both high-speed -steel single point turning tools and twist drills. Wears of Cutting Tool Discounting brittle fracture and edge chipping, which have already been dealt with, tool wear is basically of three types. Flank wear, crater wear, and notch wear. Flank wear occurs on both the major and the minor cutting edges. On the major cutting edge, which is responsible for bulk metal removal, these results in increased cutting forces and higher temperatures which if left unchecked can lead to vibration of the tool and workpiece and a condition where efficient cutting can no longer take place. On the minor cutting edge, which determines workpiece size and surface finish, flank wear can result in an oversized product which has poor surface finish. Under most practical cutting conditions, the tool will fail due to major flank wear before the minor flank wear is sufficiently large to result in the manufacture of an unacceptable component. Because of the stress distribution on the tool face, the frictional stress in the region of sliding contact between the chip and the face is at a maximum at the start of the sliding contact region and is zero at the end. Thus abrasive wear takes place in this region with more wear taking place adjacent to the seizure region than adjacent to the point at which the chip loses contact with the face. This result in localized pitting of the tool face some distance up the face which is usually referred to as catering and which normally has a section in the form of a circular arc. In many respects and for practical cutting conditions, crater wear is a less severe form of wear than flank wear and consequently flank wear is a more common tool failure criterion. However, since various authors have shown that the temperature on the face increases more rapidly with increasing cutting speed than the temperature on the flank, and since the rate of wear of any type is significantly affected by changes in temperature, crater wear usually occurs at high cutting speeds. At the end of the major flank wear land where the tool is in contact with the uncut workpiece surface it is common for the flank wear to be more pronounced than along the rest of the wear land. This is because of localised effects such as a hardened layer on the uncut surface caused by work hardening introduced by a previous cut, an oxide scale, and localised high temperatures resulting from the edge effect. This localised wear is usually referred to as notch wear and occasionally is very severe. Although the presence of the notch will not significantly affect the cutting properties of the tool, the notch is often relatively deep and if cutting were to continue there would be a good chance that the tool would fracture. If any form of progressive wear allowed to continue, dramatically and the tool would fail catastrophically, i. e. the tool would be no longer capable of cutting and, at best, the workpiece would be scrapped whilst, at worst, damage could be caused to the machine tool. For carbide cutting tools and for all types of wear, the tool is said to have reached the end of its useful life long before the onset of catastrophic failure. For high-speed-steel cutting tools, however, where the wear tends to be non-uniform it has been found that the most meaningful and reproducible results can be obtained when the wear is allowed to continue to the onset of catastrophic failure even though, of course, in practice a cutting time far less than that to failure would be used. The onset of catastrophic failure is characterized by one of several phenomena, the most common being a sudden increase in cutting force, the presence of burnished rings on the workpiece, and a significant increase in the noise level. Mechanism of Surface Finish Production There are basically five mechanisms which contribute to the production of a surface which have been machined. These are:(l) The basic geometry of the cutting process. In, for example, single point turning the tool will advance a constant distance axially per revolution of the workpiecc and the resultant surface will have on it, when viewed perpendicularly to the direction of tool feed motion, a series of cusps which will have a basic form which replicates the shape of the tool in cut. (2) The efficiency of the cutting operation. It has already been mentioned that cutting with unstable built-up-edges will produce a surface which contains hard built-up-edge fragments which will result in a degradation of the surface finish. It can also be demonstrated that cutting under adverse conditions such as apply when using large feeds small rake angles and low cutting speeds, besides producing conditions which lead to unstable built-up-edge production, the cutting process itself can become unstable and instead of continuous shear occurring in the shear zone, tearing takes place, discontinuous chips of uneven thickness are produced, and the resultant surface is poor. This situation is particularly noticeable when machining very ductile materials such as copper and aluminum. (3) The stability of the machine tool. Under some combinations of cutting conditions; workpiece size, method of clamping ,and cutting tool rigidity relative to the machine tool structure, instability can be set up in the tool which causes it to vibrate. Under some conditions this vibration will reach and maintain steady amplitude whilst under other conditions the vibration will built up and unless cutting is stopped considerable damage to both the cutting tool and workpiece may occur. This phenomenon is known as chatter and in axial turning is characterized by long pitch helical bands on the workpiece surface and short pitch undulations on the transient machined surface. (4)The effectiveness of removing swarf. In discontinuous chip production machining, such as milling or turning of brittle materials, it is expected that the chip (swarf) will leave the cutting zone either under gravity or with the assistance of a jet of cutting fluid and that they will not influence the cut surface in any way. However, when continuous chip production is evident, unless steps are taken to control the swarf it is likely that it will impinge on the cut surface and mark it. Inevitably, this marking besides looking. (5)The effective clearance angle on the cutting tool. For certain geometries of minor cutting edge relief and clearance angles it is possible to cut on the major cutting edge and burnish on the minor cutting edge. This can produce a good surface finish but, of course, it is strictly a combination of metal cutting and metal forming and is not to be recommended as a practical cutting method. However, due to cutting tool wear, these conditions occasionally arise and lead to a marked change in the surface characteristics. Limits and Tolerances Machine parts are manufactured so they are interchangeable. In other words, each part of a machine or mechanism is made to a certain size and shape so will fit into any other machine or mechanism of the same type. To make the part interchangeable, each individual part must be made to a size that will fit the mating part in the correct way. It is not only impossible, but also impractical to make many parts to an exact size. This is because machines are not perfect, and the tools become worn. A slight variation from the exact size is always allowed. The amount of this variation depends on the kind of part being manufactured. For examples part might be made 6 in. long with a variation allowed of 0.003 (three-thousandths) in. above and below this size. Therefore, the part could be 5.997 to 6.003 in. and still be the correct size. These are known as the limits. The difference between upper and lower limits is called the tolerance. A tolerance is the total permissible variation in the size of a part. The basic size is that size from which limits of size arc derived by the application of allowances and tolerances. Sometimes the limit is allowed in only one direction. This is known as unilateral tolerance.Unilateral tolerancing is a system of dimensioning where the tolerance (that is variation) is shown in only one direction from the nominal size. Unilateral tolerancing allow the changing of tolerance on a hole or shaft without seriously affecting the fit.When the tolerance is in both directions from the basic size it is known as a bilateral tolerance (plus and minus). Bilateral tolerancing is a system of dimensioning where the tolerance (that is variation) is split and is shown on either side of the nominal size. Limit dimensioning is a system of dimensioning where only the maximum and minimum dimensions arc shown. Thus, the tolerance is the difference between these two dimensions. Surface Finishing and Dimensional Control Products that have been completed to their proper shape and size frequently require some type of surface finishing to enable them to satisfactorily fulfill their function. In some cases, it is necessary to improve the physical properties of the surface material for resistance to penetration or abrasion. In many manufacturing processes, the product surface is left with dirt .chips, grease, or other harmful material upon it. Assemblies that are made of different materials, or from the same materials processed in different manners, may require some special surface treatment to provide uniformity of appearance. Surface finishing may sometimes become an intermediate step processing. For instance, cleaning and polishing are usually essential before any kind of plating process. Some of the cleaning procedures are also used for improving surface smoothness on mating parts and for removing burrs and sharp corners, which might be harmful in later use. Another important need for surface finishing is for corrosion protection in a variety of: environments. The type of protection procedure will depend largely upon the anticipated exposure, with due consideration to the material being protected and the economic factors involved. Satisfying the above objectives necessitates the use of main surface-finishing methods that involve chemical change of the surface mechanical work affecting surface properties, cleaning by a variety of methods, and the application of protective coatings, organic and metallic. In the early days of engineering, the mating of parts was achieved by machining one part as nearly as possible to the required size, machining the mating part nearly to size, and then completing its machining, continually offering the other part to it, until the desired relationship was obtained. If it was inconvenient to offer one part to the other part during machining, the final work was done at the bench by a fitter, who scraped the mating parts until the desired fit was obtained, the fitter therefore being a fitter in the literal sense. J It is obvious that the two parts would have to remain together, and m the event of one having to be replaced, the fitting would have to be done all over again. In these days, we expect to be able to purchase a replacement for a broken part, and for it to function correctly without the need for scraping and other fitting operations.When one part can be used off the shelf to replace another of the same dimension and material specification, the parts are said to be interchangeable. A system of interchangeability usually lowers the production costs as there is no need for an expensive, fiddling operation, and it benefits the customer in the event of the need to replace worn parts. Automatic Fixture Design Traditional synchronous grippers for assembly equipment move parts to the gripper centre-line, assuring that the parts will be in a known position after they arc picked from a conveyor or nest. However, in some applications, forcing the part to the centre-line may damage cither the part or equipment. When the part is delicate and a small collision can result in scrap, when its location is fixed by a machine spindle or mould, or when tolerances are tight, it is preferable to make a gripper comply with the position of the part, rather than the other way around. For these tasks, Zaytran Inc. Of Elyria, Ohio, has created the GPN series of non- synchronous, compliant grippers. Because the force and synchronizations systems of the grippers are independent, the synchronization system can be replaced by a precision slide system without affecting gripper force. Gripper sizes range from 51b gripping force and 0.2 in. stroke to 40Glb gripping force and 6in stroke. Grippers Production is characterized by batch-size becoming smaller and smaller and greater variety of products. Assembly, being the last production step, is particularly vulnerable to changes in schedules, batch-sizes, and product design. This situation is forcing many companies to put more effort into extensive rationalization and automation of assembly that was previouslyextensive rationalization and automation of assembly that was previously the case. Although the development of flexible fixtures fell quickly behind the development of flexible handling systems such as industrial robots, there are, nonetheless promising attempts to increase the flexibility of fixtures. The fact that fixtures are the essential product - specific investment of a production system intensifies the economic necessity to make the fixture system more flexible. Fixtures can be divided according to their flexibility into special fixtures, group fixtures, modular fixtures and highly flexible fixtures. Flexible fixtures are characterized by their high adaptability to different workpieces, and by low change-over time and expenditure. There are several steps required to generate a fixture, in which a workpiece is fixed for a production task. The first step is to define the necessary position of the workpiece in the fixture, based on the unmachined or base pan, and the working features. Following this, a combination of stability planes must be selected. These stability planes constitute the fixture configuration in which the workpiece is fixed in the defined position, all the forces or torques are compensated, and the necessary access to the working features is ensured. Finally, the necessary positions of moveable or modular fixture elements must be calculated- adjusted, or assembled, so that the workpiece is firmly fixed in the fixture. Through such a procedure the planning and documentation of the configuration and assembly of fixture can be automated.The configuration task is to generate a combination of stability planes, such that fixture forces in these planes will result in workpiece and fixture stability. This task can be accomplished conventionally, interactively or in a nearly fully automated manner. The advantages of an interactive or automated configuration determination are a systematic fixture design process, a reduction of necessary designers, a shortening of lead time and better match to the working conditions. In short, a significant enhancement of fixture productivity and economy can be achieved.中文翻译译文：基本加工工序和切削技术基本加工工序机床是从早期的埃及人的脚踏动力车和约翰威尔金森的镗床发展而来的。它们为工件和刀具提供刚性支撑并可以精确控制它们的相对位置和相对速度。基本上讲，金属切削是指一个磨尖的锲形工具从有韧性的工件表面上去除一条很窄的金属。切屑是被废弃的产品，与其它工件相比切屑较短，但对于未切削部分的厚度有一定的增加。工件表面的几何形状取决于刀具的形状以及加工操作过程中刀具的路径。大多数加工工序产生不同几何形状的零件。如果一个粗糙的工件在中心轴上转动并且刀具平行于旋转中心切入工件表面，一个旋转表面就产生了，这种操作称为车削。如果一个空心的管子以同样的方式在内表面加工，这种操作称为镗孔。当均匀地改变直径时便产生了一个圆锥形的外表面，这称为锥度车削。如果刀具接触点以改变半径的方式运动，那么一个外轮廓像球的工件便产生了；或者如果工件足够的短并且支撑是十分刚硬的，那么成型刀具相对于旋转轴正常进给的一个外表面便可产生，短锥形或圆柱形的表面也可形成。平坦的表面是经常需要的，它们可以由刀具接触点相对于旋转轴的径向车削产生。在刨削时对于较大的工件更容易将刀具固定并将工件置于刀具下面。刀具可以往复地进给。成形面可以通过成型刀具加工产生。多刃刀具也能使用。使用双刃槽钻钻深度是钻孔直径5-10倍的孔。不管是钻头旋转还是工件旋转，切削刃与工件之间的相对运动是一个重要因数。在铣削时一个带有许多切削刃的旋转刀具与工件接触，工件相对刀具慢慢运动。平的或成形面根据刀具的几何形状和进给方式可能产生。可以产生横向或纵向轴旋转并且可以在任何三个坐标方向上进给。基本机床机床通过从塑性材料上去除屑片来产生出具有特别几何形状和精确尺寸的零件。后者是废弃物，是由塑性材料如钢的长而不断的带状物变化而来，从处理的角度来看，那是没有用处的。很容易处理不好由铸铁产生的破裂的屑片。机床执行五种基本的去除金属的过程：车削，刨削，钻孔，铣削。所有其他的去除金属的过程都是由这五个基本程序修改而来的，举例来说，镗孔是内部车削；铰孔，攻丝和扩孔是进一步加工钻过的孔；齿轮加工是基于铣削操作的。抛光和打磨是磨削和去除磨料工序的变形。因此，只有四种基本类型的机床，使用特别可控制几何形状的切削工具1.车床，2.钻床，3.铣床，4.磨床。磨削过程形成了屑片，但磨粒的几何形状是不可控制的。通过各种加工工序去除材料的数量和速度是巨大的，正如在大型车削加工，或者是极小的如研磨和超精密加工中只有面的高点被除掉。一台机床履行三大职能：1.它支撑工件或夹具和刀具2.它为工件和刀具提供相对运动3.在每一种情况下提供一系列的进给量和一般可达4-32种的速度选择。加工速度和进给速度，进给量和切削深度是经济加工的三大变量。其他的量数是攻丝和刀具材料，冷却剂和刀具的几何形状，去除金属的速度和所需要的功率依赖于这些变量。切削深度，进给量和切削速度是任何一个金属加工工序中必须建立的机械参量。它们都影响去除金属的力，功率和速度。切削速度可以定义为在旋转一周时速度记录面相对任何瞬间呈辐射状扩散的针，或是两个相邻沟槽的距离。切削深度是进入的深度和沟槽的深度。在车床中心的车削在机动车床上完成的基本操作已被介绍了。那些用单点刀具在外表面的操作称为车削。除了钻孔，铰孔，研磨内部表面的操作也是由单点刀具完成的。所有的加工工序包括车削，镗孔可以被归类为粗加工，精加工或半精加工。精加工是尽可能快而有效的去除大量材料，而工件上留下的一小部分材料用于精加工。精加工为工件获得最后尺寸，形状和表面精度。有时，半精加工为精加工留下预定的一定量的材料，它是先于精加工的。一般来说，较长的工件同时被一个或两个车床中心支撑。锥形孔，所谓的中心孔，两端被钻的工件适于车床中心-通常沿着圆柱形工件的轴线。工件接近为架的那端通常由尾架中心支撑，在靠近主轴承的那端由主轴承中心支撑或由爪盘夹紧。这种方法可以牢固的加紧工件并且能顺利地将力传给工件；由卡盘对工件提供的辅助支撑减少切削时发生的颤振趋势，如果能小心准确地采用卡盘支撑工件的方法，则可以得到精确的结果。在两个中心之间支撑工件可以得到非常精确的结果。工件的一端已被加工，那么工件便可车削了。在车床上加工另一端，中心孔充当精确定位面和承载工件重量和抵制切削力的支撑面。当工件由于任何一原因从车床上移除后，中心孔将准确地使工件回到这个车床上或另一个车床上或一个圆柱磨床上。工件不允许被卡盘和车床中心夹在主轴承上。然而首先想到的是一个快速调整卡盘上工件的方法，但这是不允许的因为在由卡盘夹持的同时也由车床中心支撑是不可能的。由车床中心提供的调整将不能持续并且爪盘的压力会损坏中心孔和车床中心，甚至是车床主轴。浮动的爪盘为上述陈述提供了一个例外，它几乎完全使用在高生产工作上，这些卡盘是真正的工作驱动者并且不为同样的目的如普通的三爪，四爪卡盘使用。而大直径的工件有时装在两个中心，它们最好有由面板夹持在主轴承尾部来顺利得到能量转换；许多车床夹头并不能足量的转换能量，虽然可以作为特殊的能量转换。机械加工介绍作为产生形状的一种方法，机械加工是所有制造过程中最普遍使用的而且是最重要的方法。机械加工过程是一个产生形状的过程，在这过程中，驱动装置使工件上的一些材料以切屑的形式被去除。尽管在某些场合，工件无支承情况下，使用移动式装备来实现加工，但大多数的机械加工是通过既支承工件又支承刀具的装备来完成。小批量，低成本。机械加工在制造业上有两个应用。是铸造，锻造和压力工作，产生每一个特殊形状，甚至一个零件，几乎总有较高的模具成本。焊接的形状很大程度上取决于原材料。通过利用总成本高但没有特殊模具的设备，加工是有可能的；从几乎任何形式的原材料开始，只要外部尺寸足够大，由任意材料设计形状。因此加工是首选的方法，当生产一个或几个零件甚至在大批量生产时，零件的设计在逻辑上导致铸造，锻造或冲压制品。高精度，表面精度。机械加工的第二个应用是基于可能的高精度和表面精度的。如果在其他工序中大批量生产，很多低量零件会产生出低的但可接受的公差。另一方面，许多零件由一些大变形过程产生一般的形状，并且只在具有很高精度的选定面加工。举例来说，内线流程是很少产生任何方式以外的其他机械加工并且紧接着压力操作后零件上的小洞可能被加工。主要的切削参数在切削时基本工具工作的关系充分描述的方法有4个因素：刀具几何形状，切削速度和切削深度。刀具必须由适当的材料做成；它必须有一定的强度，粗糙度，硬度和抗疲劳度。刀具几何形状由面和角度描述，对每一种切削操作都是正确的。切削速度是指切削刃通过工作面的速度，它已每分钟通过的英尺数表示。对于加工效率，切削速度相对于特殊工作组合必须具有适当规模。一般来讲，工件越硬，速度越小。进给是刀具进入工件的速率。当工件或刀具旋转时，进给量的单位是英寸每转。当刀具或工件往复移动时，进给量的单位是英寸没次，总的来说，在其他相似情况下进给量与切削速度成反比。切削速度用英寸表示，是刀具进入工件的距离表示的，它是指车削时屑片的宽度或是直线切削时屑片的厚度。粗加工时切削深度比精加工的切削深度大。切削参数的改变对切削温度的影响在金属切削作业中热量产生于主要和第二变形区而这些结果导致了复杂温度遍布于刀具，工件和屑片。一个典型的等温先如图所示，它可以看出正如预测的，当工件材料经历主要变形，被减切时，有一个非常大温度梯度遍布于屑片的整个宽度。当第二变形区的屑片还有一小段距离就达到了最大温度。因为几乎所有的工作都以金属切削转化为热量而完成，可以预测去除每一单位体积的金属所增加的能量消耗将会提高切削温度。因此在所有其他参数不变，前角变大时，将减少去除每单位体积金属的能量和切削温度。当考虑到增加未形成屑片的厚度和速度，情况就更复杂了。增加切削厚度往往会大大影响热量传给工件，刀

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