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机械毕业设计英文翻译
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英文翻译外文文献翻译454自动装配技术,机械毕业设计英文翻译
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附录 A 自动装配技术 过去，对大批量的成品数量的需求逐渐增加 , 以至工程师们去寻找并且发展制造的新方法。 在各种制造业技术的不同部门，许多个别企业已经取得发展并且允许以较低的费用增加以完善成品的产量。当两个或多个部份同时出现用以生产成品时，便需要进行此过程。 组装过程的早期发展史与大批量生产方法的发展史的关系是十分密切的。 因此，大批量生产的先锋也是现代组装生产的先锋。 现代的新理念给大批量的组装方法带来重要的进步 . 尽管制造业工程学的某些部门 , 像是金属的切断和金属的热处理 ,最近非常快速地已经发展，但是基本的组装技术的发展速度仍然没有改变 . 尽管人们所取得的成功是很有限的并且许多的装配工人依然象产业革命时期的工人那样用一些基本的工具。在过去的几年中，人们已经努力通过自动化的应用和现代工艺来减少生产成本，例如，超声波焊接和压模法。 组装系统的发展过程 在早期产品制造过程中，一个技术工人不仅仅要负责产品生产的单个环节，同时也要掌 控整个生产过程。因此，对于一个技术工人来说应该全面掌握生产要领是很重要的，同时培养一个全面的技术工人也是一项费时费钱的工作。由于工人能力有限导致生产规模十分有限，不能满足实际需求。 1798 年，美国政府需要一大批枪械，但是联邦调查局不能满足他们的需要。因为当时与法国的战争迫在眉睫，所以去欧洲寻求支援是不太可能的事。然而， Eli惠特尼作为当时大批量生产的先锋，承诺在 28 个月内提供美国所需 10000 支枪械。虽然完成契约需要花费大量时间和金钱，但惠特尼的在大批量生产的新提法上已经被成功的证实了。在肯乃迪克州的建立 了新的工厂来专门大批量的生产枪械。这些机器为技术工人减少了必需掌握的技术，同时也增加了劳动生产率。在1801 年，惠特尼让高贵的来宾从一大批货品中随意抽选来观看时，大家震惊了。惠特尼工作的结果是为工业制造领域带来了三个重大的贡献。首先，通过机器制造的产品比手工制造的质量高。这些产品可以互换，并且是集合工作变得简单化。其次，最终产品的准确性能被保持在一个比较高的标准，第三，最重要的产品生nts产率被提高。 Oliver Eban s 材料传输不需要人工最终促进了自动化的发展。在 1793年，他在一个自动化面粉压榨集中运用 了三种运送装置，只需要两个操作者。第一个操作员把面粉倒入漏斗，第二个操作员用麻布袋包装用压榨机生产的面粉。所有操作的中间环节都是由自动传送带由一个操作者传给另一个重要的贡献由Elihu Root 设计了集装化方法。在 1894 年，他加入了生产“六发式左轮手枪”的公司。即使那时集合成分的各种不同的操作相当的简单，他把这些操作分成能够被快速无误完成的基本单元。操作区分概念是“工作分工，提高产量”。用这种方法，即和工作被转为非常基本的操作操作员经过短暂的培训，就能获得较高的效率。腓特烈文斯洛泰勒或许是第一个将技术时间 和运动引进到制造业技术中的。这项技术是为完成需要的工作节省操作者的时间和体力来确保工作和与之有关的工作放在合时的位置。泰勒也发现了任何的工人都有工作最适宜的速度，如果超过，会造成全部表现的减少。 毫无疑问地，生产的发展的主要贡献者和几何方法是亨利福特。他在下面描绘了集会的原则： 首先，放置工具，然后由人工操作，并且确保在产品完成的过程中流动的距离最短。 其次，使用滑动的工具或其他形式的运送工具，使工作人员完成他们的操作后，把东西放在他们手边同一个并且是最方便的位置，如果可能的话，让他以地心引力传给下一个工作 人员。 第三，用滑动装配线将集合的零件以适当的间隔传送，是隔开处理他们是比较容易的。 这些方法逐渐被应用在生产福特汽车 T 模板中 现代的装配线技术首先在调速轮磁发电机的集会中被使用。在最初的方法中，一个操作员在 20 分钟之内装配了一个磁发电机。我们发现这个过程被分成29 个独立的的操作，每个操作员沿着装配线在装配区间执行各自的操作，整个装配时间被缩短到 13 分钟 10 秒。当装配线的高度在 8 分钟被提升时，先在被缩短到 7 分钟。在进一步的实验后我们找到了合适的装配线传输速度，传送时间被降到 5 分钟，他所用的时间是原有装配程序的四分之一。这个结果促使亨利福特nts在为汽车产生副装配工厂的其他部门使用它的装配系统。后来，这给从事主要汽车装配的操作人员，在工作的 副装配流程中带来了连续不断的快速增加。后来发现操作人员无法应付增加的流程，而且不久之后很清楚的看到，主要的装配不得不在同一个装配线上来完成。起初，主要的装配运动是由一根粗绳由一个地方拉到另一个地方来完成的。然而，随着生产技术的发展，令人吃惊的是整个装配时间由 12 小时 28 分降到 5 小时 50 分。最后，一个永无止境的力量驱动器被安装。这有流溢的地板和广阔的地方容纳地盘。当他们进行他们的操作是为他们提供坐或站的空间，运送装置以 6 小时 45 分钟的速度运送到每个工作站。更进一步的进步导致了整体装配时间的缩短，最后，生产一辆 汽车所用的时间只有 10 秒钟。 以上这种类型的装配操作通常是由一个装配操作者来完成的，而且他是最普遍运用的大规模产品的生产方法。然而，在特定的情况下，更加精炼的装配方法已经出现。 作为基本装配生产线原则的逻辑延伸部分，机械装配方式取代了操作人员的操作方法已经被设计。在这里，用自动化设备取代人工操作的方法很普通，操作起来也很简单。相对机械生产而然，用人工生产是不经济的。对于大多数的产品而言，这种装配方法被迅速的传播。 然而，完全自动化的产品装配是不存在的。 装配方法的选择 当考虑到产品的装配时，一个制造业者不得不考虑影响装配系统选择的许多因素。对于一个新产品，接下来考虑的通常是重要的： 装配成本 必要的产品生产率 劳动效率 产品的市场生命周期 如果有一种尝试能够证明现有操作装配线的自动化是合理的，那么必须要考虑变成多余的那些操作人员有所调动。如果劳动力过剩，自动化程度取决于由引进自动化装配线所导致的装配成本的降低和产品生产率的增加。然而，必须既得的是，大体上，自动化机器的资本投入必须在产品的市场生命周期之上被分期偿还。清楚的是如果不是这种情形，产品的市场生命是很短的，自动化通 常是不可证明的。 nts自动装配的优势 下面是自动化的一些优势： 降低装配成本； 提高了产品的生产率； 产品标准化； 减低了操作员的危险操作。 除了上面列出的特殊情况，降低成本是主要考虑的因素，如果他不能按预期的降低成本，那么自动化就不可能被使用。在一个先进的工业社会，生产力是对操作效率的重要衡量。增加的生产力对制造业不会产生直接的利益，除非生产力是十分稀缺的资源，但对扩张经济是必要的，因为它为其他的工作提供了人员保障。很清楚，一旦装配的自动化生产线产生效力时，所需操作人员的数量会逐渐的减少，生产力增强。 一个操 作人员能很容易操作的一些装配工作，把它复制在大部分较复杂的自动化工作中是极其困难的。有时一个精密的检验系统被需要用来探测零件的明显错误。如果尝试装配零件被接受，但事实上有缺陷，一个操作者，在没有成功的尝试完成装配，能够非常迅速的拒绝零件，如果在产品上没有重要的漏洞。在自动化装配，然而，除非这个零件被安装系统拒绝，一个自动化的系统将会在某一时刻停止，会被浪费并且减少错误。如果零件只有一个小错误，一个操作者也许能够完成安装，但是所生产的产品不能完全满意。他时常会被认为自动化装配其中的一个优势是它能长久的确保产品 的高质量，因为如果零件不能满足特定的需求，机器就会出错。 在一些情形中，由于高温、有毒物质和其他的材料会对操作人员装配产生危险。在这些环境下，机械装配会有明显的优势。 程序设计被定义为“将设计数据转换成操作指导，并对其负责的次要系统。课程设计更具体的定义是“生产设备在建立过程中的作用，以及程序被应用（正如那些机器有能力操作这些程序）目的是为了将原始形式按照事先设计好的工程图的细节转换成最终形式（设计图通常是由工程师设计的）。”把原始资料输入程序中会出现不同的形式。（在机器生产过程中，这些材料通常起因于 一个形成金属的程序，最普通的就是块状存货，铸件，锻链，或者也许是一块厚金属板，nts其他的程序已经被输入资料。）另外，机器材料也可能被烧成一些粗糙的形状，（火焰切割是操作生产的一个部分）或只是矩形范围的材料。投入的材料可能有各式的形状和物力性质。一些程序可能改变零件的大小或表面质地。其他的程序，像热处理，只能改变材料的物理性质。更确切的说，韧化会减少物质的韧性，降低细工品伸缩力。用这些生材料作为基础，程序的设计者必须准备将那些所需要的程序由通常预定材料转化成最终的、具体的几何形状。一个程序设计者处理的最普通的金属 转化程序就是转，车断面，磨，钻孔，穿孔，螺旋转，成型，纹孔，平刨，锯，环锯，抛光，冲压，磨削。一些制造业的人可能把一些操作视为主要种类的子集。纹孔时常被视为一个演练的子集。其他可能定义为更主要的种类。一些不熟知的程序，例如：电的解除装置，电气化学的机制和被用于物质移动的激光机制。所有的应用程序也适用于产品，应当被程序设计者考虑。 程序设计的要素 道尔将程序运行活动通常分成类。 解释设计说明书的要求。 在机器上放置部分。 在处理的每个阶段决定中间产品的需求。 选择主要的设备操纵这个过程。 在每次操作中，选择工具和处理过程的顺序。 计算运行程序所用的时间。 程序设计公文。 一些这样的活动能被分成叫小的单位；这项活动详述提供了一个方便的编目方法为了分析。 手动程序设计 一个程序设计者通常在下列的限制之下操作 他为给定的一组机器做设计。 机器有能力限制制造业操作的数量。 机器有特定的负担和工作量。 如果给这些机器加以限制，每组工作图包含特定的 partgeometry 需求，程序设计者依靠他们的经验也能设计生产产品的程序。程序的选择不是完全随机的nts也不是完全不可预测的。通常生产一个具体的表面化的产品不 只一个程序：程序设计者必须选择一个他认为最好的程序。通常会取消相似的部分，或者至少是相似的表面，这种方法被用在部分制造业中。以这种方式，设计者通过曾经用过的具体程序和获得的最终的设计书明书比较，选择他认为最好的来替代。这种类型的设计被认为是最适用的设计程序，同时它也是今天最普通的产品设计类型。设计生产零件的操作程序需要两组可变的知识：部分需求（一种工程图所指出）；可得的机器和程序，每个程序的运行能力。假使这些是可变的，设计者会选择生产一个最终产品所需的组合程序。在选择程序组合时，需要一些标准。产品的成本和所 花费的时间通常是决定程序选择的标准。然而，机器的利用和工作路线排定经常会影响计划的选择。大体上来说，程序设计者会选择最好的程序和机器来生产成套产品而不是单独的一小部分。正如所想，大部分的程序设计目前还存在，是一种艺术并非一个科学。程序数据时常被记录在一个黑名单中。这个信息可能是可靠的也可能不是。同样的，设计者也一定选择操作数据。（例如机器的速度，饲养和深度）。在一次，一个黑名单被雇用选择这些操作特性 这次黑名单在某种程度上更复杂（一本机制数据手册）；然而，他不保证操作效率，只有可行性。 自动的程序设计 一个有效率的程序设计系统对于每项活动都有好的决策规则，这样很少能做出差劲的计划。能设计一个如此有效的系统是通过减少对一系列机械步骤的决策来完成的。然而，即使使用一个好的决策规则，由于人的交流存在差异性，程序设计仍然会出现问题。程序设计师一线无聊并乏味的工作。因此，人类个性化的设计时常产生错误的程序设计。由于个性化的设计使劳动力增加了一倍，所以导致许多工厂将投资转向自动化程序设计。无论设计系统是自动的还是人工的，道尔所定义的个一般需求都要在程序设计中有所体现。在接下来的部分，自动化的程序设计构架将会被描述。 Spur 和 Optiz 中有人第一次写了关于制造业系统自动化以及程序设设机在这些系统中所扮演的角色 . 马刺也许是第一个将差异性和生产力定义到程序设计方法，机械化，设计系统的实施。不同的程序设计方法以团队的技术为基础，同时还要具备必要的两个步骤。 nts 建立一个程序计划目录（通常也叫做“菜单”）用所给的机器工具生产整个产品。 设计必要的软件来检验所设计的产品，在目录中找到最靠近的传真机，然后取回联合的程序计划。 程序设计的生产方法有四个必要的步骤组成。 详细的描述 描述可得生产部分程序的目录。 描述操作过程中的机械工具。 建立软件来检查零件，程序和机器的可得性，并且考察三者是否能相容。 大体上，计划使用生产力政策需要详细的描述，对制造业程序详细的理解和他们的准确性。以不同政策为基础的制造业决定采取几个标准来解决个人的操作问题，并且适应或调整他们所需要的地方 附录 B Automatic Assembly The modern assembly line technique was first employed in the assembly of a flywheel mangneto. In the original method, one operator assembled a magneto in 20 min. It was found that when the process was divided into 29 indibidual operations, carried out by separate operators working at assembly stations spaced along an assembly line, the total assembly time was reduced to 13 min 10s. When the height of the assembly line was raised by 8 in, the time was reduced to 7 min .After further experiments were carried out to find the optimum speed of the assembly line conveyor,the time was reduced to 5 min, which was only one-fourth of the time taken by the original process of assembly. This result encouraged Henry Ford to ntsutilize his system of assembly in other department of the factory,which were producing subassemblies for the car. Subsequently, this brought a continous and rapidly increasing flow of subassemblies to the operators working on the main car assembly. It was found that the operators could not cope with increased flow, and it soon became clear that the main assembly would also have to be carried out on an assembly line. At first, the movement of the main assemblies was achieved simply by pulling them by a rope from station to station. Howere, even this development produced the amazing result of a reduction in the total time of assemble from 12h 28 min to 5 h 50 min. Eventually a power-driven endless conveyer was installed. It was fulsh with the floor and wide enough to accommodate a chassis. Space was provided for workers to either sit or stand while they carried out their operations and the conveyrs moved at a speed of 6 ft/min past 45 separate workstations. With the introduction of this conveyor, the total assemble time was reduced to 93 min. Further improvements led to an even shorter overall assembly time and eventually, a production rate of one car every 10 s of the working day was achieved. The type of assembly operation dealt with above is usually referred to as operator assembly, and it is still the most widespread method of assembling mass-or large-batch-produced products.However, in certain cases, more refined methods of assembly have now emerged. As a logical extension of the basic assembly line principle, methods of replacing operators by mechanical means of assembly have been debised. Here, it is usual to attempt to replace operators with automatic workheads where the tasks being performed were very simple and to retain the operators for tasks that would be uneconomical to mechanize. This method of assembly has rapid gained popularity for mass production and is usually referred to as automatic assembly. However, complete automation where the product is assembled completely by machine is essentialy nonexistent. Choice of Assembly method When considering the assembly of a product, a manufacturer has to take into account the many factors that affect the choice of assembly system. For a new ntsproduct, the following considerations are generally important: Cost of assembly; Production rat required; Availability of labor; Market life of the product. If an attempt is to be made3 to justify the automation of an existing operator assembly line, consideration has to be given to the redeployment of those operators who would become redundant. If labor is plentiful, the degree of automation depends on the reduction in cost of assembly and the increase in production rate brought about by the automation of the assembly line. However, it must be remembered that, in general , the capital investment in automatic machinery has to be amortized over the market life of the product unless the machinery may be adapted to assemble a new product. It is clear that if this is not the case and the market life of the product is short, automation is generallly not justifiable. Advantages of Automatic Assembly Following are some of the advantages of automation: Reduction in the cost of assembly; Increased productivity; A more consistent prodect; Removal of operators from hazardous operations. A reduction in costs is often the main consideration and, except for the special circumstances listed above, it could be expected that automation would not be carried out if it was not expected to produce a reduction in cost. Productivity in an advanced industrial society is an important measure of operating efficiency. Increased productivity, although not directly beneficial to manufacturer unless labor is scarce, is necessary to an expanding economy because it releases personnel for other tasks. It is clear that when put into effect, automation of assembly lines generally reduces the number of operators required and hence increases productivity. Some of the assembly tasks that an operator can perform easily are extremely ntsdifficult to duplicate on even the most sophisticated automatic workhead. An operator can often carry out a visual inspection of the part to be assembled, and parts that are obviously defective can be discarded. Sometimes a bery elaborate inspection system is required to detect even the most obviously defective part. If an attempt is made to assemble a part that appears to be acceptable but is in fact defective, an operator, after unsuccessfully trying to complete the assembly, can reject the part very quickly without a significant loss in production. In automatic assembly, however, unless the part has been rejected by the feeding device, an automatic workhead will probably stop an time will then be wasted locating and eliminating the fault. If a part has only a minor defect, an operator may be able to complete the assembly, but the resulting prodect may not be completely satisfactory. It is often suggested that one of the advantages of automatic assembly is that it ensures a product of consistently high quality because the machine faults if the parts do not conform to the required specifications. In some situations, assembly by operators would be hazardous due to high temperatures and the presence of toxic substances and other materials. Under these circumstances,assembly by mechanical means is obviously advantageous. The increasing need for finished goods in large quantities has, in the past, led engineers to search for and to develop new methods of production. Many indibidual developments in the various branches of manufacturing technology have been made and have allowed the increased production of improved finished goods at lower cost. One of the most important manufacturing processes is the assembly process. This process is required when two or more component parts are to be brought together to produce the finished product. The early history of assembly process development is closely related to the history of the development of mass-production methods. Thus, the pioneers of mass production are also the pioneers of the moderassembly process. Their new ideas and concepts have brought significant improvements in the assembly methods employed in large-volume production. However, although som branches of manufacturing engineering, such as metal ntscutting and metal forming processes, have recently been developing very rapidly, the technology of the basic assembly process has failed to keep pace. Table 28.1 shows that in the United States the percentage of the total labor force inbolved in the assembly process baries from about 20% for the manufacture of farm machinery to almost 60% for the manufacture of telephone and telegraph equipment. Because of this, assembly costs often account for more than 50% of the total manufacturing costs. Statistical surveys show that these figures are increasing every year. In the past few years, certain efforts have been made to reduce assembly costs by the application of automation and modern techniques, such as ultrasonic welding and die-casting. Howerer, success has been very limited and many assembly operators are still using the same basic tools as those employed at the time of the Industrial Revolution. In the early days of manufacturing technology, the complete assembly of a product was carried out by a single operator and usually, this operator also manufacutred the individual component part of the assembly. Consequently, it was necessary for the operator to be an exper in all the barious aspects of the work, and training a new operator was a long and expensive task. The scale of production was often limited by the availability of trained operators rather than by the demand for the product. In 1798, the United States needed a large supply of muskets and federal arsenals could not meet the demand. Because war with the French was imminent, it was also not possible to obtain additional supplies from Europe. However, Eli whitney, now recognized as one of the pioneers of mass production, offered to contract to make 10000 muskets in 28 menths. Although it took 10.5 yuars to complete the contract, Whitneys novel ideas on mass production had been successfully proved. The factory at New Haven, Connecticut, built specially for the manufacture of the muskets, contained machines for producing interchangeable parts. These machines reduced the skills required by the bariou operators and allowed significant increases in the rate of production. In an historic demonstration in 1801, Whitney surprised his distinguished visitors when he assembled musket ntslocks after randomly selected parts from a heap. The results of Eli Whitneys work brought about threee primary developments in manufacturing methods. First, parts were manufactured on machines, resulting in a consistently higher quality than that of hand-made parts. These parts were now interchangeable and as a consequence assembly work was simplified. Second, the accuracy of the final product could be maintained at a higher standard, and third, production rates could be significantly increased. Oliver Ebanss conception of conveying materials from one place to another without manual effort led eventually to further developments in automation for assembly. In 1793, he used three types of conveyors in an automatic flour mill, which required only two operators. The first operator poured rain into a hopper and the second filled sacks with flour procduced by the mill. All the intermediat operations were carried out automatically with conveyors carrying the material from operation to operation. The next significant contribution to the development of assembly methods was made by Elihu Root. In 1849, Elihu Root joined the company that was producing Colt “six shooters”.Even though at that time the various operation of assembling the component parts were quite simple, he divided these operations into basic units that could be completed more quickly and with less chance of error. Toots division of operations gave rise to the concept “divide the work and multiply the output”. Using this principle, assembly work was reduced to very basic operations and with only short periods of operator training, high efficiencies could be obtained. Frederick Winslow Taylor was probably the first person to introduce the methods of time and motion study to manufacturing technology. The objective was to save the operators time and energy by making sure that the work and all things associated to the work were placed in he best positions for carrying out the required tasks. Taylor also discovered that any worker has an optimum speed of working which, if exceeded,results in a reduction in overall performance. Undoubtedly, the principal contributor to the development of production and assembly methods was Henry Ford. He described his principles of assembly in the ntsfollowing words: “First, place the tools and then men in the sequence of the operations so that each part shall travel the least distance whilst in the process of finishing”. “Second, use work slides or some other form of carrier so that when a workman complete his operation he drops the part always in the same place which must always be the most convenient place to his hand and if possible have gravity carry the part to the next wokman. “Third, use sliding assembly lines by which parts to be assembled are delivered at convenient intervals, spaced to make it easier to work on them”. These principles were gradually applied in the production of the Model T Ford automobile. The increasing need for finished goods in large quantities has, in the past, led engineers to search for and to develop new methods of production. Many indibidual developments in the various branches of manufacturing technology have
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