K076-泵体零件机械加工工艺和专用夹具设计【2套】【铣底面+钻3-M12底孔】【含CAD图纸、工序卡、说明书】
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毕业设计报告(论文)报告(论文)题目:泵体(II)零件机械加工 工艺和专用夹具设计 作者所在系部: 机电工程学院 作者所在专业: 机械设计制造及其自动化 作者所在班级: B13113 作 者 姓 名 : 牛从从 作 者 学 号 : 20134011305 指导教师姓名: 丁红军 完 成 时 间 : 2017年6月 北华航天工业学院教务处制本科生毕业设计(论文)开题报告论文(设计)题目泵体零件机械加工工艺和专用夹具设计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其自动化作者所在班级B13113作 者 姓 名牛从从作 者 学 号20134011305指导教师姓名丁红军指导教师职称讲师完 成 时 间2017年3月北华航天工业学院教务处制说 明1根据学校毕业设计(论文)工作暂行规定,学生必须撰写毕业设计(论文)开题报告。开题报告作为毕业设计(论文)答辩委员会对学生答辩资格审查的依据材料之一。2开题报告应在指导教师指导下,由学生在毕业设计(论文)工作前期内完成,经指导教师签署意见及所在专业教研室论证审查后生效。开题报告不合格者需重做。3毕业设计开题报告各项内容要实事求是,逐条认真填写。其中的文字表达要明确、严谨,语言通顺,外来语要同时用原文和中文表达。第一次出现缩写词,须注出全称。4开题报告中除最后一页外均由学生填写,填写各栏目时可根据内容另加附页。5阅读的主要参考文献应在10篇以上(土建类专业文献篇数可酌减),其中外文资料应占一定比例。本学科的基础和专业课教材一般不应列为参考资料。6参考文献的书写应遵循毕业设计(论文)撰写规范要求。7开题报告应与文献综述、一篇外文译文和外文原文复印件同时提交,文献综述的撰写格式按毕业设计(论文)撰写规范的要求,字数在2000字左右。毕业设计(论文)开题报告学生姓名牛从从专 业机械设计制造及其自动化班 级B13113指导教师姓名丁红军职 称讲师工作单位北华航天工业学院课题来源教师自拟题目课题性质应用研究课题名称泵体零件机械加工工艺和专用夹具设计本设计的科学依据(科学意义和应用前景,国内外研究概况,目前技术现状、水平和发展趋势等)制造工艺是制造技术的灵魂、核心和关键,是生产中最活跃的因素。其过程是采用金属切削刀具或磨具及其他加工方法来加工工件,使工件达到所要求的形状、尺寸、表面粗糙度和力学物理性能,从而生产出合格零件。夹具的使用可以有效的保证加工质量,提高生产效率,降低生产成本,扩大机床的工艺范围,减轻工人劳动强度,保证安全生产等。考虑到机械加工工艺安排及夹具的使用在泵体的生产中直接影响到其加工质量和生产效率等,所以研究泵体的机械加工工艺及夹具设计的课题有着十分重要的意义。当代机械制造业主要采用单件生产、多品种/小批量和重复大批量生产等多种方式。多样化经营模式、工艺复杂,所需设备和工装繁多。目前采用CAPP编制工艺很普遍,成组工序允许采用同一设备和工艺装置,以及相同或相近的机床调整方式来加工工全组零件。成组技术亦可应用于零件加工的全工艺过程。采用先进的机床和刀具,工序集中,使加工高效、简洁、可靠,简化生产计划和生产组织工作。夹具最早出现在18世纪后期,随着科学技术的不断进步,夹具已从一种辅助工具发展为门类齐全的工艺装备。近年来,数控机床、加工中心、成组技术、柔性制造系统等新加工技术的应用,对机床夹具提出了很多新的要求。在现代制造业的发展中,机械加工过程越来越柔性化,现代机床夹具的发展方向:标准化、精密化、高效化、柔性化。随着现代科学的快速发展,加工控制和测量技术在不断进步,国外先进的制造工艺是将泵体和泵盖分别加工,然后组合到一起进行产品的总装,在保证精度的前提下,大大提高了加工效率,降低了成本。在大型泵体部件的加工工艺中,采用先进的设备、工装和检测手段确保产品质量,是泵行业不断追求工艺技术创新和突破的努力方向。设计内容和预期成果(具体设计内容和重点解决的技术问题、预期成果和提供的形式)先进行零件图的分析,主要内容包括:生产类型、零件的作用、结构特点、结构工艺性、关键表面的技术要求分析等。然后进行工艺设计,主要内容包括:确定毛坯类型;毛坯选择与说明;工艺路线的确定(粗、精基准的选择,各表面的加工方法的确定,工序集中与分散的考虑,工序顺序的安排的原则,加工设备与工装的选择,不同方案的分析比较等);加工余量、切削用量及基本时间、工序尺寸与公差的确定。最后进行专用夹具设计,主要内容包括:夹具设计思想与不同方案的对比;定位装置和对刀及导引装置的选择;夹紧机构设计与夹紧力的计算。重点解决的技术问题:粗、精基准的选择,工序顺序的安排,机床与工装的选择,加工余量、切削用量的计算,定位装置与对刀装置的选择,夹紧力的计算。预期成果及提供形式:工序卡片一套,对所设计的工序内容进行技术经济分析的分析报告一份,两套夹具装配图各一张,两套夹具零件图各一张,设计说明书一份,对所设计的专用夹具进行技术经济分析的分析报告一份。拟采取设计方法和技术支持(设计方案、技术要求、实验方法和步骤、可能遇到的问题和解决办法等)设计方案:首先对零件进行分析,然后对给定零件进行工艺过程设计,制订加工顺序并编制相应的工序卡片,最后进行专用夹具的设计。技术要点:分析零件、选择定位基准、制订加工顺序、划分加工阶段、计算工序尺寸、制订切削参数、制订工时定额等,并对制订的方案进行技术经济分析,提供分析报告。熟悉工序技术要求,熟悉并准备所有设计资料;制订合理的定位方案,并设计定位元件结构;制订合理的夹紧方案,并设计夹紧结构;制订导向方案,并选择导向元件;制订分度方案,并设计分度机构;制订夹具整体布局方案,设计夹具体;标注合理的技术要求,并分析精度是否满足要求;对夹具进行技术经济分析。可能遇到的问题及解决办法:1、定位基准的选择。参照选择原则选择合理的定位基准;2、工序顺序的安排。借鉴查到的资料上的工序顺序和向指导老师询问;3、工序尺寸、切削参数、工时定额的计算。按照指导书里的计算格式去查要用到的参考书并认真计算;4、制定专用夹具的定位与夹紧方案。借鉴查到的资料里的方案和向指导老师询问。5、制订夹具整体布局方案。参照参考书里的专用夹具布局、询问指导老师。实现本项目预期目标和已具备的条件(包括过去学习、研究工作基础,现有主要仪器设备、设计环境及协作条件等)在以前的学习中,学习了机械制造技术基础和工艺装备设计,基本上掌握了制定工艺的方法要点和夹具的设计要点,大四上学期的专业方向综合课程设计也是工艺和专用夹具设计,为这次的课题奠定了一定的基础,做课题时用到的参考书也了解了都有哪些,对泵体通过在网上、图书馆查阅资料也有了一定的认识,对国内外先进的加工方法和新的工艺也有了一些了解,这为以后的设计打下了基础,不会盲目的去做,在机床、夹具、刀具的选用上以传统工艺为主,主要的设计环境就是室内,并且无特殊的技术条件。各环节拟定阶段性工作进度(以周为单位)查阅资料,撰写文献综述; 1周根据撰写的文献综述填写开题报告,并查找与之相关的外文资料并翻译; 1周准备各种资料,熟悉零件图,并绘制零件图; 1周完成机械加工过程的设计; 1周对所设计的加工工艺进行技术经济分析; 1周完成工艺技术经济分析报告; 1周编写工序卡片; 1周根据工序内容编写一套夹具设计任务书; 1周设计一套专用夹具; 1周根据工序内容编写第二套夹具设计任务书; 1周设计第二套专用夹具; 1周拆一套零件图; 1周拆第二套零件图; 1周完成设计说明书一份; 1周对所设计的专用夹具进行技术经济分析,并完成分析报告; 1周其它时间:机动处理,比如整理打印图纸、打印装订分析报告,答辩准备等。 1周- 4 -开 题 报 告 审 定 纪 要时 间地点主持人参会教师姓 名职 务(职 称)姓 名职 务(职 称)论证情况摘要 记录人:指导教师意见指导教师签名: 年 月 日教研室意见教研室主任签名: 年 月 日北华航天工业学院毕业论文摘 要 本文是对泵体零件加工应用及加工的工艺性分析,此外还对钻削泵体上3-M6-7H的螺纹孔以及铣削泵体底面的两道工序的加工设计了专用钻床夹具及专用铣床夹具。在机床上加工工件时,为了保证加工精度,必须正确安装工件,使其相对机床切削成形运动和刀具占有正确的位置,这一过程称为“定位”。为了不因受切削力、惯性力、重力等外力作用而破坏工件已定的正确位置,还必须对其施加一定的夹紧力,这一过程称为“夹紧”。定位和夹紧的全过程称为“安装”。在机床上用来完成工件安装任务的重要工艺装备,就是各类夹具中应用最为广泛的“机床夹具”。机床夹具的种类很多,但广泛用于批量生产,专为某工件加工工序服务的专用夹具,需要各制造厂根据工件加工工艺自行设计制造。因此,专用夹具的设计是一项重要生产准备工作,每一个从事加工工艺的工装设计人员,都应该掌握有关夹具设计的基础知识。关键词 泵体 加工工艺 专用夹具 钻床夹具 铣床夹具AbstractThis paper is on the bracket parts processing application and processing technology and analysis, In addition to the stuffing box cover part two process designing special fixture.Processes the work piece when the engine bed, to guarantee the working accuracy, must install the work piece correctly, causes its relative engine bed cutting builder motion and the cutting tool holds the correct position, this process is called “the localization”. For because of exogenic processes and so on cutting force, force of inertia, gravity is not destroyed the work piece already the correct position which decides, but must exert certain clamping force to it, this process is called “the clamp”. The localization and the clamp entire process is called “the installment”. Uses for on the engine bed to complete the work piece to install the duty the important craft equipment, is in each kind of jig widely applies “the engine bed jig”.The engine bed jigs type are many, the use scope broadest universal jig, the specification size many have standardized, and has the specialty factory to carry on the production. But widely uses in the volume production, specially unit clamp which serves for some work piece working process, then needs various factories independently to design the manufacture according to the work piece processing craft. Therefore, unit clamps design is an important production preparatory work, each is engaged in the processing craft the work clothes designers, should grasp the related jig design the elementary knowledge.Key words Pump body Processing technology Special jig Drilling jig Milling jig II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B13113作 者 姓 名牛从从作 者 学 号20134011305指导教师姓名丁红军指导教师职称讲师完 成 时 间2017年3月北华航天工业学院教务处制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。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,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。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。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。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。原文:Basic Machining OperationsMachining tools have evolved from the early foot powered lathe Egyptians and John Wilkinsons boring mill. They are 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 metal 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 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 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 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 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 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 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 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 work piece may be in any of the three coordinate directions.Basic Machine ToolsMachine 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 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 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, 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. 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 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 or 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 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 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 centersThe basic operations operations performed on an engine lathe 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 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 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 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 collet 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 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 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 to 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 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 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 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.BoringThe objective of boring a hole in a lathe is:1To enlarge the hole 2To machine the hole to the desired diameter3To accurately locate the position of the hole 4To obtain a smooth surface finish in the holeThe motion of the boring tool is parallel to the axis of the lathe when the carriage is moved in the longitudinal direction 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 hole 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 the hole by carriage. Variations of this design are used, depending on the job to be done. The lead angle used, if any, should always be small. Also, the nose radius of the boring tool must not be too large. The cutting speed used for boring can be equal to the speed for turning. However, when the spindle speed of the lathe is calculated, the finished, or largest, bore diameter should be used. The feed rate for boring is usually somewhat less than for turning to compensate for the rigidity of the boring bar.The boring operation is generally performed in two steps; namely, rough boring and finish boring. The objective of the rough-boring operation is to remove the excess metal rapidly and efficiently, and the objective of the finish-boring operation is to obtain the desired size, surface finish, and location of the hole. The size of the hole is obtained by using the trial-cut procedure. The diameter of the hole can be measured with inside calipers and outside micrometer calipers. Basic Measuring Instrument, or inside micrometer calipers can be used to measure the diameter directly.Cored holes and drilled holes are sometimes eccentric with respect to the rotation of the lathe. When the boring tool enters the work, the boring bar will take a deeper cut on one side of the hole than on the other, and will deflect more when taking this deeper cut, with the result that the bored hole will not be concentric with the rotation of the work. This effect is corrected by taking several cuts through the hole using a shallow depth of cut. Each succeeding shallow cut causes the resulting hole to be more concentric than it was with the previous cut. Before the finale, finish cut is taken, the hole should be concentric with the rotation of the work in order to make certain that the finished hole will be accurately located.Shoulders, grooves, contours, tapers, and threads are also bored inside of holes. Internal grooves are cut using a tool that is similar to external grooving tool. The procedure for boring internal shoulder is very similar to the procedure for turning shoulders. Larger shoulders are faced with the boring tool positioned with the nose leading, and using the cross slide to feed the tool. Internal contours can be machined using a tracing attachment on a lathe. The tracing attachment is mounted on the cross slide and the stylus follows the outline of the master profile plate. This causes the cutting tool to move in a path corresponding to the profile of the profile plate. Thus, the profile on the master profile plate is reproduced inside the bore. The master profile plate is accurately mounted on a special slide which can be precisely in two directions, in order to align the cutting tool in the correct relationship to the work. This lathe has cam-lock type of spindle nose which permits it to take a cut when rotating in either direction. Normal turning cuts are taken with the spindle rotating counterclockwise. The boring cut is taken with the spindle revolving in a clockwise direction, or “backwards”. This permit the boring cut to be taken on the “back side” of the bore which is easier to see from the operators position front of the lathe. This should not be done on lathes having a threaded spindle nose because the cutting force will tend to unscrew the chuck.MillingMilling is a machining process for removing material by relative motion between a workpiece and a rotating cutter having multiple cutting edges. In some applications, the workpiece is held stationary while the rotating cutter is moved past it and a given feed rate (traversed). In other applications, both the workpiece and cutter are moved in relation to each other and in relation to the milling machine. More frequently, however, the workpiece is advanced at a relatively low rate of movement or feed to a milling cutter rotating at a comparatively high speed, with the cuter axis remaining in a fixed position, a characteristic feature of the milling process is that each milling cutter tooth takes its share of the stock in the form of small individual chips. Milling operations are performed on many different machines.Since both the workpiece and cutter can be moved relative to one another, independently or in combination, a wide variety of operations can be performed by milling. Applications include the production of flat or contoured surfaces, slots, grooves, recesses, threads, and other configurations. Milling is one of the most universal, yet complicated machining methods. The process has more variations in the kinds of machines used, workpie
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