基于ProE的二级圆柱齿轮减速器实体设计
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信息时代的机械工程在80年代的初期,工程师们曾经认为要加快产品的研制开发,必须进行大量的研究工作。结果是实际上只进行了较少的研究工作,这是因为产品开发周期的缩短,促使工程师们尽可能地利用现有的技术。研制开发一种创新性的技术并将其应用在新产品上,是有风险的,并且易于招致失败。在产品开发工程中采用较少的步骤是一种安全的和易于成功的方法。对于资金和人力都处于全球性环境中的工程界而言,缩短产品研制开发周期也是有益的。能够设计和制造各种产品的人可以在世界各地找到。但是,具有创新思想的人则比较难找.对于你已经进行了6个月的研制开发工作,地理上的距离已经不再是其他人发现它的障碍。如果你的研制周期较短,只要你仍然保持领先,这种情况并不会造成严重后果。但是如果你正处于一个长达6年的研制开发过程的中期,一个竞争对手了解到你的研究工作的一些信息,这个项目将面临比较大的麻烦。工程师们在解决任何问题时都需要进行新的设计这种观念很快就过时了.在现代设计中的第一步是浏览因特网或则其他系统,看其他人是否已经设计了一种类似于你所需要的产品,诸如传动装置或者换热器等。通过这些信息系统,你可能发泄有些人已经有了制造图纸,数控纸带和制造你的产品所需要的其他所有东西。这样,工程师们就可以把他们的职业技能集中在尚未解决的问题上。在解决这类问题时,利用工作站和进入信息高速公路可以大大增强工程小组的能力和效率。这些信息时代的工具可以使工程小组利用大规模的数据库。数据库中有材料性能,标准,技术和成功的设计方案等信息。这些经过验证的设计可以通过下载直接应用,或者通过对其进行快速,简单的改进来满足特定的要求.将产品技术要求通过网络送出去的远程制造也是可行的。你可以建立一个没有任何加工设备的虚拟公司。你可以指示制造商,在产品加工完成后,将其直接送给你的客户。定期访问你的客户可以保证你设计的产品按照设计要求进行工作。尽管这些研制开发方式不可能对每个公司都完全适用,但是这种可能性是存在的。过去客户设计的产品通常是由小公司来制造。大公司不屑于制造这种产品,他们讨厌与特殊定向产品市场,或者是客户设计的小批量产品打交道。这就是我的产品”,一家大公司这样说:这是我们能够制造出来的最好产品,你应该喜欢它。如果你不喜欢,顺这条街走有一家小公司,它会按你的要求去做。”今天,因为客户们有较大的选择余地,几乎所有的市场都是特殊定向产品市场.如果你不能使你的产品满足某些特定客户的要求,你将失去你市场份额中的一大部分,或者失掉全部份额。由于这些定向产品市场是经常变化的,你的公司应该对时常的变化作出快速的反应。定向产品市场和根据客户要求进行设计这种现象的出现改变了工程师研究工作的方式。今天,研究工作通常是针对解决特定问题进行的。现在许多由政府资助或者由大公司出资开发的技术可以在非常低的成本下被自由使用,尽管这种情况可能是暂时的。在对这些技术进行适当改进后,它们通常能够被直接用于产品开发,这使得许多公司可以节省昂贵的研究经费。在主要的技术障碍被克服后研究工作应该主要致力于产品的商品化方面,而不是开发新的,有趣的,不确定的替换产品。采用上述观点看问题,工程研究应该致力于消除将已知技术快速商品化的障碍。工作的重点是产品的质量和可靠性,这些在当今的顾客的头脑中是最重要的。很明显,一个质量差的声誉是一个不好企业的同义词。企业应该尽最大的努力来保证顾客得到合格的产品,这个努力包括在生产线的终端对产品进行严格的检验和自动更换有缺陷的产品。研究工作应该着重考虑诸如可靠性等因素对成本带来的益处。当可靠性提高时,制造成本和系统的最终成本将会降低。如果在生产线的终端产生了30%的废品,这不仅会浪费金钱,也会给你的竞争对手创造一个利用你的想法制造产品,并将其销售给你的客户的良机。提高可靠性和降低成本这个过程的关键是深入,广泛地利用设计软件。设计软件可以使工程师们加快每一阶段的设计工作。然而,仅仅缩短每一阶段的设计时间,可能不会显著地缩短整个设计过程的时间。因而必须致力于采用并行工程软件,这样可以使所有设计组的成员都能使用共同的数据库。随着我们步入信息时代,要取得成功,工程师们在技术开发和技术管理方面都应该具有一些独特的知识和经验。成功的工程师们不但应该具有宽广的知识和技能,而且还应该是某些关键技术或学科的专家,他们还应该在社会因素和经济因素对市场影响方面有敏锐的洞察能力。将来,花在解决日常工程问题上的费用将会减少,工程师们将会在一些更富有挑战性,更亟待解决的问题上协同工作,大大缩短解决这些问题所需要的时间。我们已经开始了工程实践的新阶段。计算机和网络工程师们具有了越来越强的解决问题的能力,这也给他们的工作带来了很大的希望和喜悦。为了确保成功,我们所使用的工具的性能和对更好的产品与系统的不断追求应该与标志着在过程方面所有巨大努力的创新工作所带来的喜悦相适应。机械工程是一个伟大的行业,在我们尽可能多地利用了信息时代所提供的机遇后,它将变得更加伟大。许多工程师的职责是进行产品设计,而产品是通过对材料的加工制造而生产出来的。设计工程师在材料选择制造方法等方面起着关键的作用.一个设计工程师应该比其他的人更清楚地知道他的设计需要达到什么目的。他知道他对使用载荷和使用要求的假设,产品的使用环境,产品应该具有的外观形貌。为了满足这些要求,他必须选择和规定所使用的材料。通常,为了利用材料并使产品具有所期望的形状,设计工程师知道应该采用哪些制造方法。在许多情况下,选择了某种特定材料就可能意味着已经确定了某种必须采用的加工方法。同时,当决定采用某种加工方法后,很可能需要对设计进行修改,以使这种加工方法能够被有效而经济地应用。某些尺寸公差可以决定产品的加工方法。总之,在将设计转变为产品的过程中,必须有人做出这些决定.在大多数情况下,如果设计人员在材料和加工方法方面具有足够的知识,他会在设计阶段做出最为合理的决定。否则,做出的决定可能会降低产品的性能,或则使产品变得过于昂贵。显然,设计工程师是制造过程中的关键人物,如果他们能够进行面向生产(即可以进行高效率生产)的设计,就会给公司带来效益。制造工程师们选择和调整所采用的加工方法和设备,或者监督和管理这些加工方法和设备的使用。一些工程师进行专用工艺装备的设计,以使通用机床能够被用来生产特定的产品。这些工程师们在机床,工艺能力和材料方面必须具有广泛的知识,以使机器在没有过载和损坏,而且对被加工材料没有不良影响的情况下,更为有效地完成所需要的加工工序。这些制造工程师们在制造业中也起到重要作用。少数工程师们设计在制造业中使用的机床和设备。显然,他们是设计工程师。而且对于他们的产品而言,他们同样关心设计,材料和制造方法4之间的相互关系。然而,他们更多地关心他们所设计的机床将要加工的材料的性能和机床与材料之间的相互作用。还有另外一些工程师材料工程师,他们致力于研制新型和更好的材料,他们也应该关心这些材料的加工方法和加工对这些材料性能的影响。尽管工程师们所起的作用可能有很大的差别,但是,大部分工程师们都必须考虑材料与制造工艺之间的相互关系。低成本制造并不是自动产生的.在产品设计,材料选择,加工工艺装备选择和设计之间都有着非常密切的相互依赖关系。这些步骤中的每一个都必须在开始制造前仔细地加以考虑,规划和协调。这种从产品设计到实际生产的准备工作,特别是对于复杂产品,可能需要数月甚至数年的时间,并且可能花费很多钱。典型的例子有,对于一种全新的汽车,从设计到投产所需要的时间大约为2年,而一种现代化飞机则可能需要4年。随着计算机和由计算机产生的纸带与由计算机本身控制的机器的出现,我们进入了一个生产计划的新时代。采用计算机将产品的设计功能与制造功能集成,被称为CAD/CAM(计算机辅助设计/计算机辅助制造).这种设计被用来制定加工工艺规程和提供加工过程本身的编程信息。可以根据供设计由于制造用的中心数据库内的信息绘制零件图,需要时可以生成加工这些零件时所使用的程序。此外,对加工后的零件的计算机辅助试验与检测也得到了广泛的应用。随着计算机价格的降低和性能的提高,这种趋势将毫无疑问地得到不断加速的发展。车床主要是为了进行车外圆、车端面和镗孔等项工作而设计的机床。车削很少在其他种类的机床上进行,而且任何一种其他机床都不能像车床那样方便地进行车削加工。由于车床还可以用来钻孔和铰孔,车床的多功能性可以使工件在一次安装中完成几种加工。因此,在生产中使用的各种车床比任何其他种类的机床都多。车床的基本部件有:床身、主轴箱组件、尾座组件、溜板组件、丝杠和光杠。床身是车床的基础件。它能常是由经过充分正火或时效处理的灰铸铁或者球墨铁制成。它是一个坚固的刚性框架,所有其他基本部件都安装在床身上。通常在床身上有内外两组平行的导轨。有些制造厂对全部四条导轨都采用导轨尖朝上的三角形导轨(即山形导轨),而有的制造厂则在一组中或者两组中都采用一个三角形导轨和一个矩形导轨。导轨要经过精密加工以保证其直线度精度。为了抵抗磨损和擦伤,大多数现代机床的导轨是经过表面淬硬的,但是在操作时还应该小心,以避免损伤导轨。导轨上的任何误差,常常意味着整个机床的精度遭到破坏。主轴箱安装在内侧导轨的固定位置上,一般在床身的左端。它提供动力,并可使工件在各种速度下回转。它基本上由一个安装在精密轴承中的空心主轴和一系列变速齿轮(类似于卡车变速箱)所组成。通过变速齿轮,主轴可以在许多种转速下旋转。大多数车床有812种转速,一般按等比级数排列。而且在现代机床上只需扳动24个手柄,就能得到全部转速。一种正在不断增长的趋势是通过电气的或者机械的装置进行无级变速。由于机床的精度在很大程度上取决于主轴,因此,主轴的结构尺寸较大,通常安装在预紧后的重型圆锥滚子轴承或球轴承中。主轴中有一个贯穿全长的通孔,长棒料可以通过该孔送料。主轴孔的大小是车床的一个重要尺寸,因此当工件必须通过主轴孔供料时,它确定了能够加工的棒料毛坯的最大尺寸。尾座组件主要由三部分组成。底板与床身的内侧导轨配合,并可以在导轨上作纵向移动。底板上有一个可以使整个尾座组件夹紧在任意位置上的装置。尾座体安装在底板上,可以沿某种类型的键槽在底板上横向移动,使尾座能与主轴箱中的主轴对正。尾座的第三个组成部分是尾座套筒。它是一个直径通常大约在5176mm(23英寸)之间的钢制空心圆柱体。通过手轮和螺杆,尾座套筒可以在尾座体中纵向移入和移出几个英寸。车床的规格用两个尺寸表示。第一个称为车床的床面上最大加工直径。这是在车床上能够旋转的工件的最大直径。它大约是两顶尖连线与导轨上最近点之间距离的两倍。第二个规格尺寸是两顶尖之间的最大距离。车床床面上最大加工直径表示在车床上能够车削的最大工件直径,而两顶尖之间的最大距离则表示在两个顶尖之间能够安装的工件的最大长度。普通车床是生产中最经常使用的车床种类。它们是具有前面所叙的所有那些部件的重载机床,并且除了小刀架之外,全部刀具的运动都有机动进给。它们的规格通常是:车床床面上最大加工直径为305610mm(1224英寸);但是,床面上最大加工直径达到1270mm(50英寸)和两顶尖之间距离达到3658mm的车床也并不少见。这些车床大部分都有切屑盘和一个安装在内部的冷却液循环系统。小型的普通车床车床床面最大加工直径一般不超过330mm(13英寸)-被设计成台式车床,其床身安装在工作台或柜子上。虽然普通车床有很多用途,是很有用的机床,但是更换和调整刀具以及测量工件花费很多时间,所以它们不适合在大量生产中应用。通常,它们的实际加工时间少于其总加工时间的30%。此外,需要技术熟练的工人来操作普通车床,这种工人的工资高而且很难雇到。然而,操作工人的大部分时间却花费在简单的重复调整和观察切屑过程上。因此,为了减少或者完全不雇用这类熟练工人,六角车床、螺纹加工车床和其他类型的半自动和自动车床已经很好地研制出来,并已经在生产中得到广泛应用。先进制造技术中的一个基本的概念是数字控制(NC)。在数控技术出现之前,所有的机床都是由人工操纵和控制的。在与人工控制的机床有关的很多局限性中,操作者的技能大概是最突出的问题。采用人工控制是,产品的质量直接与操作者的技能有关。数字控制代表了从人工控制机床走出来的第一步。数字控制意味着采用预先录制的、存储的符号指令来控制机床和其他制造系统。一个数控技师的工作不是去操纵机床,而是编写能够发出机床操纵指令的程序。对于一台数控机床,其上必须安有一个被称为阅读机的界面装置,用来接受和解译出编程指令。发展数控技术是为了克服人类操作者的局限性,而且它确实完成了这项工作。数字控制的机器比人工操纵的机器精度更高、生产出零件的一致性更好、生产速度更快、而且长期的工艺装备成本更低。数控技术的发展导致了制造工艺中其他几项新发明的产生: 电火花加工技术、激光切割、电子束焊接 数字控制还使得机床比它们采用有人工操的前辈们的用途更为广泛。一台数控机床可以自动生产很多类的零件,每一个零件都可以有不同的和复杂的加工过程。数控可以使生产厂家承担那些对于采用人工控制的机床和工艺来说,在经济上是不划算的产品生产任务。同许多先进技术一样,数控诞生于麻省理工学院的实验室中。数控这个概念是50年代初在美国空军的资助下提出来的。在其最初的价段,数控机床可以经济和有效地进行直线切割。然而,曲线轨迹成为机床加工的一个问题,在编程时应该采用一系列的水平与竖直的台阶来生成曲线。构成台阶的每一个线段越短,曲线就越光滑。台阶中的每一个线段都必须经过计算。在这个问题促使下,于1959年诞生了自动编程工具(APT)语言。这是一个专门适用于数控的编程语言,使用类似于英语的语句来定义零件的几何形状,描述切削刀具的形状和规定必要的运动。APT语言的研究和发展是在数控技术进一步发展过程中的一大进步。最初的数控系统下今天应用的数控系统是有很大差别的。在那时的机床中,只有硬线逻辑电路。指令程序写在穿孔纸带上(它后来被塑料带所取代),采用带阅读机将写在纸带或磁带上的指令给机器翻译出来。所有这些共同构成了机床数字控制方面的巨大进步。然而,在数控发展的这个阶段中还存在着许多问题。一个主要问题是穿孔纸带的易损坏性。在机械加工过程中,载有编程指令信息的纸带断裂和被撕坏是常见的事情。在机床上每加工一个零件,都需要将载有编程指令的纸带放入阅读机中重新运行一次。因此,这个问题变得很严重。如果需要制造100个某种零件,则应该将纸带分别通过阅读机100次。易损坏的纸带显然不能承受严配的车间环境和这种重复使用。这就导致了一种专门的塑料磁带的研制。在纸带上通过采用一系列的小孔来载有编程指令,而在塑料带上通过采用一系列的磁点眯载有编程指令。塑料带的强度比纸带的强度要高很多,这就可以解决常见的撕坏和断裂问题。然而,它仍然存在着两个问题。其中最重要的一个问题是,对输入到带中指令进行修改是非常困难的,或者是根本不可能的。即使对指令程序进行最微小的调整,也必须中断加工,制作一条新带。而且带通过阅读机的次数还必须与需要加工的零件的个数相同。幸运的是,计算机技术的实际应用很快解决了数控技术中与穿孔纸带和塑料带有关的问题。在形成了直接数字控制(DNC)这个概念之后,可以不再采用纸带或塑料带作为编程指令的载体,这样就解决了与之有关的问题。在直接数字控制中,几台机床通过数据传输线路联接到一台主计算机上。操纵这些机床所需要的程序都存储在这台主计算机中。当需要时,通过数据传输线路提供给每台机床。直接数字控制是在穿孔纸带和塑料带基础上的一大进步。然而,它敢有着同其他信赖于主计算机技术一样的局限性。当主计算机出现故障时,由其控制的所有机床都将停止工作。这个问题促使了计算机数字控制技术的产生。微处理器的发展为可编程逻辑控制器和微型计算机的发展做好了准备。这两种技术为计算机数控(CNC)的发打下了基础。采用CNC技术后,每台机床上都有一个可编程逻辑控制器或者微机对其进行数字控制。这可以使得程序被输入和存储在每台机床内部。它还可以在机床以外编制程序,并将其下载到每台机床中。计算机数控解决了主计算机发生故障所带来的问题,但是它产生了另一个被称为数据管理的问题。同一个程序可能要分别装入十个相互之间没有通讯联系的微机中。这个问题目前正在解决之中,它是通过采用局部区域网络将各个微机联接起来,以得于更好地进行数据管理。普通车床作为最早的金属切削机床的一种,目前仍然有许多有用的和为人要的特性和为人们所需的特性。现在,这些机床主要用在规模较小的工厂中,进行小批量的生产,而不是进行大批量的和产。在现代的生产车间中,普通车床已经被种类繁多的自动车床所取代,诸如自动仿形车床,六角车床和自动螺丝车床。现在,设计人员已经熟知先利用单刃刀具去除大量的金属余量,然后利用成型刀具获得表面光洁度和精度这种加工方法的优点。这种加工方法的生产速度与现在工厂中使用的最快的加工设备的速度相等。普通车床的加偏差主要信赖于操作者的技术熟练程度。设计工程师应该认真地确定由熟练工人在普通车床上加工的试验件的公差。在把试验伯重新设计为生产零件时,应该选用经济的公差。六角车床 对生产加工设备来说,目前比过去更注重评价其是否具有精确的和快速的重复加工能力。应用这个标准来评价具体的加工方法,六角车床可以获得较高的质量评定。在为小批量的零件(100200件)设计加工方法时,采用六角车床是最经济的。为了在六角车床上获得尽可能小的公差值,设计人员应该尽量将加工工序的数目减至最少。自动螺丝车床 自动螺丝车床通被分为以下几种类型:单轴自动、多轴自动和自动夹紧车床。自动螺丝车床最初是被用来对螺钉和类似的带有螺纹的零件进行自动化和快速加工的。但是,这种车床的用途早就超过了这个狭窄的范围。现在,它在许多种类的精密零件的大批量生产中起着重要的作用。工件的数量对采用自动螺丝车床所加工的零件的经济性有较大的影响。如果工件的数量少于1000件,在六角车床上进行加工比在自动螺丝车床上加工要经济得多。如果计算出最小经济批量,并且针对工件批量正确地选择机床,就会降低零件的加工成本。自动仿形车床 因为零件的表面粗糙度在很大程度上取决于工件材料、刀具、进给量和切削速度,采用自动仿形车床加工所得到的最小公差一定是最经济的公差。在某些情况下,在连续生产过程中,只进行一次切削加工时的公差可以达到0.05mm。对于某些零件,槽宽的公差可以达到0.125mm。镗孔和休用单刃刀具进行精加工时,公差可达到0.0125mm。在希望获得最大主量的大批量生产中,进行直径和长度的车削时的最小公差值为0.125mm是经济的。19Mechanical Engineering in the Information Age In the early 1980s, engineers thought that massive research would be needed to speed up product development. As it turns out, less research is actually needed because shortened product development cycles encourage engineers to use available technology for use in a new product is risky and prone to failure. Taking short steps is a safer and usually more successfully approach to product development.Shorter product development cycles are also beneficial in an engineering world in which both capital and labor are global. People who can design and manufacture various products can be found anywhere in the world, but containing a new idea is hard. Geographic distance is no longer a barrier to others finding out about your development six months into the process. If youve got a short development cycle, the situation is not catastrophic as long as you maintain you lead. But if youre in the midst of a six year development process and a competitor gets wind of your worker, the project could be in more serious trouble.The idea that engineers need to creat a new design to solve every problem is quickly becoming obsolete. The first step in the modern design process is to browse the Internet or other information systems to see if someone else has already a new transmission, or a heat exchanger that is close to what you need. Through these information system, you may discover that someone already has manufacturing drawings, numerical control tapes ,and everything else required to manufature your product. Engineers can then focus their professional competence on unsolved problems.In talckling such problems, the availability of wokstations and access to the information hignway dramatically enhance the capability of the engineering team and its productivity. These information age tools can give the team access to massive databases of material properties, standards, technologies, and successful designs. Such protested designs can be downloaded for direct use or quickly modified to meet specific needs. Remote manufacturing, in which productions are sent out over a network, is also possible. You could end up with a virtual company where you dont have to see any hardware. When the product is completed you can direct the manufaturer to drop-ship it to your customer. Periodic visits to the customer can be made to ensure that the product you designed working according to the specification. Although all of the developments wont apply equally to every company, the potential is there.Custom design used to be left to small company. Big companies sneered at itthey hated the idea of dealing with niche markets small-valum custom solutions. “Here is my product,” one of the big companies would say:“This is the best we can make it you ought like it. If you dont, theres smaller company down the street that will work on your problem.”Today, nearly every market is a niche market, because customers are selective. If you ignore the potential for tailoring your product to specific customers needs, you will lose the major part of your market share. Since these niche markets are transient, your company needs to be in a positiong to respond to them quickly.The emgergence of niche markets and design on demand has altered the way engineers conduct research. Today, research is commonly directed toward sovling particular problems. Although this situstion is probably temporary, much uncommitted technology, developed at government expense or written off by major corporationgs, is available today at very low cost. Following modest modificationgs, such technology can ofen be used directly in product development, which allows many organizations to avoid the expense of an extensive research effort. Once the technology is free of major obstacles, the research effort can focus on overcoming the barriers to commercializationg rather than on pursuing new and interesting, but undefined, alternatives.When view in this prospective, engineering research must focus primarily on removing the barriers to rapid commercilizationg of known technologies. Much of this effort must address quality and reliability concerns, which are foremost in the minds of todays consumers. Clearly, a reputationg for poor quality is synonymous with bad business. Everything possibleincluding thorough inspection at the end of the manufacturing line and automatic replacement of defective productsmust be dong to assure that the customer receives a properly functionging product.Research has to focus on the cost benefit of fators such as reliability. As reliability increases, manufanturing costs and the final costs of the system will decrease. Having 30%junk at the end of a production line not only costs a forturn but also creats an opportunity for a competitor to take your idea and sell it to your customers.Central to the process of improving reliability and lowing costs is the intensive and widespread use of design software, which allows engineers to speed up every stage of the design process. Shortening each stage, however ,may not sufficiently reduce the time required for the entire process. Therefore, attention must also be devoted to concurrent engineering software with shared databases can be accessed by all members of the design team.As we move more fully into the Information Age, success will require that the engineer possess some unique knowledge of and experience in both the development and the management of technology. Success will require broad knowledge and skills as well as expertise in some key technologies and disciplines; it also require a keen awareness of the social and economic factors at work in the marketplace. Increasingly, in the future, routin problems will not justify heavry engineering expenditures, and engineers will be expected to work cooperatively in solving more challenging , more demanding problems in substantially less time. We have begun a new phase in the practice of engineering. It offers great promise and excitement as more and more problem-solving capability is placed in the hands of the computerized and wired engineer. To assure success, the capability of our tools and the unquenched thirst for better products and systems must be matched by the joy of creation that marks all great engineering endeavors. mechanical engineering is a great profession, and it will become even greater as we make the most of the opportunities offered by the Information Age.Many engineers have as their function the designing of products that are to be brought into reality through the processing or fabrication of materials. In this capacity they are a key fator in the material selection-manufaturing procedure. A design engineer, better than any other person, should know what he or she wants a design to accomplish. He knows what assumptions he has made about service loads and requirements, what service environment the product must withstand, and what appearance he wants the final product to have. In order to meet these requirements he must select and specify the material(s)to be used. In most cases, in order to utilize the material and to enable the product to have the desired form, he knows that certain manufacturing processes will have to be employed. In many instances, the selection of a specific material may dictate what processing must be used. At the same time, when certain processes are to be used, the design may have to be modified in order for the process to be utilized effectively and economically. Certainly dimensional tolerances can dictate the processing. In any case, in the sequence of converting the design into reality, such decisions must be made by someone. In most distances they can be made most effectively at the design stage, by the designer if he has a reasonably adequate knowledge concerning materials and manufacturing processes. Otherwise, decisions may be made that will detragt from the effetiveness of the product, or the product may be needlessly costly. It is thus apparent that design engineers are a vital fator in the manufacturing process, and it is indeed the company if they design for producibilitythat is, for effient production.Manufacturing engineers select and coordinate specific processes and equipment to be used, or supervise and manage their use. Some design special tooling that is used so that standard machines can be utilized in producing special products. These engineers must have a broad knowledge of machine and process capabilities and of materials, so that desired operations can be done effectively and efficiently without overloading or damaging machines and without adversely affecting the materials being processed. These manufacturing engineers also play an important role in manufacturing.A relatively small group of engineers design the machines and equipment used in manufacturing. They obviously are design engineers and, relative to their products, they have the same concerns of the interrelationship of design, materials, and manufacturing processes. However, they have an even greater concern regarding the properties of the materials that their machines are going to process and the interreaction of the materials and the machines.Still another group of engineersthe materials engineersdevote their major efforts toward developing new and better materials. They, too, must be concerned with how these materials can be processed and with the effects the processing will have on the properties of the materials.Although their roles may be quite different, it is apparent that a large proportion of engineers must concern themselves with the interrelationship between materials and manufacturing processes.Low-cost manufature does not just happen. There is a close and interdependent relationship between the design of a product, selection of materials, selection of processes and equipment, and tooling selection and design. Each of these steps must be carefully considered, planned, and coordinated before manufacturing starts. This lead time, particularly for complicated products, may take months, even years, and the expenditure of large amount of money may be involved. Typically, the lead time for a completely new model of an automobile is about 2 years, for a modern aircraft it may be 4 years.With the advent of computers and machines that can be controlled by either tapes made by computers or by the computers themselves, we are entering a new era of production planning. The integration of the design function and the manufacturing function through the computer is called CAD/CAM(computer aided design/computer aided manufacturing). The design is used to determine the manufacturing process planning and the programming information for the manufacturing processes themselves. Detailed drawing can also be made from the central data base used for the design and manufature, and programs can be generated to make the parts as needed. In addition, extensive computer aidedtesting and inspection(CATI)of the manufactured parts is taking place. There is no doubt that this trend will continue at ever-accelerating rates as computers become chesper and smarter. Lathes are machine tools designed primarily to do turning, facing and boring, Very little turning is done on other types of machine tools, and none can do it with equal facility. Because lathes also can do drilling and reaming, their versatility permits several operations to be done with a single setup of the work piece. Consequently, more lathes of various types are used in manufacturing than any other machine tool.The essential components of a lathe are the bed, headstock assembly, tailstock assembly, and the leads crew and feed rod.The bed is the backbone of a lathe. It usually is made of well normalized or aged gray or nodular cast iron and provides s heavy, rigid frame on which all the other basic components are mounted. Two sets of parallel, longitudinal ways, inner and outer, are contained on the bed, usually on the upper side. Some makers use an inverted V-shape for all four ways, whereas others utilize one inverted V and one flat way in one or both sets, They are precisi
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