自动化生产线--外文翻译电子教案.doc

English Translation Material1. Transfer Machine The highest degree of automation with special-purpose, multifunction machines is achieved by using transfer machines. Transfer machine are essentially a combination of individual workstations arranged in the required sequence, connected by work transfer devices, and integrated with interlocked controls. Workplaces are automatically transferred between the stations, which are equipped with horizontal, vertical, or angular units to perform machining , gaging ,workplace repositioning, assembling, washing, or other operation. The two major classes of transfer machines are rotary and in-line types. An important advantage of transfer machines is that they permit the maximum number of operations to be performed simultaneously. There is relatively no limitation on the number of workplace surface or planes that can be machined, since devices can be interposed in transfer machines at practically any point for inverting, rotating, or orienting the workplace, so as to complete the machining operations. Work repositioning also minimizes the need for angular machining heads and allows operations to be performed in optimum time. Complete processing from rough casting or forging to finished parts is often possible. One or more finished parts are produced on a transfer machine with each index of the transfer system that moves the parts from stations to stations. Production efficiencies of such machines generally range from 50% for a machine variety of different parts to 85% for a machine producing one part, in high production, depending upon the workplace and how the machine is operated(material handling method, maintenance procedures, etc. ) All types of machining operations, such as drilling, tapping, reaming, boring, and milling, are economically combined on transfer machines. Lathe-type operations such as turning and facing are also being performed on in-line transfer machine, with the workplace being rotated in selected machining stations. Turning operations are performed in lathe-type segments in which toolholders are fed on slides mounted on tunnel-type bridge units. Workplace are located on centers and rotated by chucks at each turning station. Turning stations with CNC are available for use on in-line transfer machine. The CNC units allow the machine cycles to be easily altered to accommodate changes in workplace design and can also be used for automatic tool adjustments. Maximum production economy on transfer lines is often achieved by assembling parts to the workplaces during their movement through the machine. such items as bushings, seals, welch plugs, and heat tubes can be assembled and then machine or tested during the transfer machining sequence. Automatic nut torquing following the application of part subassemblies can also be carried out. Gundrilling or reaming on transfer machines is an ideal application provided that proper machining units are employed and good bushing practices are followed. Contour boring and turning of spherical seats and other surface can be done with tracer-controlled single-point inserts, thus eliminating the need for costly special form tools. In-process gaging of reamed or bored holes and automatic tool setting are done on transfer machines to maintain close tolerances. Less conventional operations sometimes performed on transfer machines include grinding, induction heating of ring gears for shrink-fit pressing on flywheels, induction hardening of valve seats, deep rolling to apply compressive preloads, and burnishing. Transfer machines have long been used in the automotive industry for production rates with a minimum of manual part handling. In addition to decreasing labor requirements, such machines ensure consistently uniform, high-quality parts at lower cost. They are no longer confined just to rough machining and now often eliminate the need for subsequent operations such as grinding and honing. More recently, there has been an increasing demand for transfer machines to handle lower volumes of similar or even different parts in smaller sizes, with means for quick changeover between production runs. Built-in flexibility, the ability to rearrange and interchange machine units, and the provision of idle stations increases the cost of any transfer machine, but such feature are economically feasible when product redesigns are common. Many such machines are now being used in nonautomotive applications for lower production requirements. Special feature now available to reduce the time required for part changeover include standardized dimensions, modular construction, interchangeable fixtures mounted on master pallets that remain on the machine, interchangeable fixture components, the ability to lock out certain stations for different parts by means of selector switches, and programmable controllers. Product design is also important, and common transfer and clamping surfaces should be provided on different parts whenever possible.2. Programmable Logic Controllers A programmable logic controller (PLC) is a solid-state device used to control machine motion or process operation by means of a stored program. The PLC sends output control signals output and receive input signals through input/output (I/O) devices. A PLC controls output in response to stimuli at the inputs according to the logic prescribed by the stored program. The inputs are made up of limit switches, pushbuttons, thumbwheels, switches, pulses, analog signal, ASCII serial data, and binary or BCD data from absolute position encoders. The output are voltage or current level to drive end devices such as solenoids, motor starters, relays, lights, and so on. Other output device include analog devices, digital BCD displays, ASCII compatible devices, servo variable-speed drives, and even computers. Programmable controllers were developed (circa in 1968) when General Motors Corps, and other automobile manufacturers were experimenting to see if there might be an alternative to scrapping all their hardwired control panel of machine tools and other production equipment during a model changeover. This annual tradition was necessary because rewriting of the panels was more expensive than buying new ones. The automotive companies approached a number of control equipment manufacturers and asked them to develop a control system that would have a longer productive life without major rewriting, but would still be understandable to and repairable by the plant personnel. The new product was named a “programmable controller”. The processor part of the PLC contains a central processing unit and memory. The central processing unit (CPU) is the “traffic direction” of the processor, the memory stores information. Coming into the processor are the electrical signals from the input devices, as conditioned by the input module to voltage levels acceptable to processor logic. The processor scans the state of I/O and updates outputs stored in the memory of the PLC. For example, the processor may be programmed so that if an input connected to a limit switch is true (limit switch closed), then a corresponding output wired to an output module is to be energized. This processor remembers this command through its memory and compares on each scan to see if that limit switch is, in fact, closed. If it is closed ,the processor energizes the solenoid by turning on the output module. The output device, such as a solenoid or motor starter, is wired to an output modules terminal, and it receives its shift signal from the processor, in effect, the processor is performing a long and complicated series of logic decisions. The PLC performs such decisions sequentially and in according with the stored program. Similarly, analog I/O allows the processor to make decisions based on the magnitude of a signal, rather than just if it is on or off. For example, the processor may be programmed to increase or decrease the steam flow to a boiler (analog output) based on a comparison of the actual temperature in the boiler (analog input ) This is often performed by utilizing the built-in PID (proportional, integral, derivative) capabilities of the processor. Because a PLC is “software based”, its control logic functions can be changed by reprogramming its memory. Keyboard programming devices facilitate entry of the revised program, which can be design to cause an existing machine or process to operate in a different sequence or to different level of, or combinations of stimuli. Hardware modifications are needed only if additional, changed, or relocated input/output device are involved. 3. Automated Assembly Assembly in the manifacturing process consists of putting together all the component parts and sub-assemblies of a given product, fastening, performing inspections and function tests, labeling, separating good assembly from bad, and packaging and or preparing them for final use. Assembly is unique compared to the methods of manufacturing such as machining, grinding, and welding in that most of these processes invovle only a few disciplines and possibly only one. Most of these nonassembly operations cannot be performed weithout the aid of equipment; thus the development of automatic methods has been necessary rather than optional. Assembly, on the other hand, may involve in one machine many of the fastening methods,such as riveting, welding, screwdriving,and adhesive application,as well as automatic parts seletion, proding, gaging, functional testing, labeling,and packaging. The state of the art in assembly operations has not reached the level of standardization; much manual work is stillbeing performed in this area. Assembly has traditionally been one of the highest areas of direct labor costs. In some cases, assembly accounts for 50% or more of manufacturing csosts and typically 20% 50%. However, closer cooperation between design and manufacturing engineers has resulted in reducing and in a few cases eliminating altogether the need for assembly. When asssembly is required, improved design or products has simplified automated (semiautomatic or automatic) assembly.Considerations for Automated AssemblyBefore automated assembly is adopted, several factors should be considerd. These include practicality of the process for automation, simulation for economic considerations and justification, management involvement, and labor relations. Determining the practicality of automated assembly required careful evaluation of the following: a)The number of parts in assembly. b)Design of the parts with respect to producibility, assembility, automatic handling, and testability (materials, forms, dimensional tolerances, and weights). c)Quality of parts to be assembled. Out-of-tolerance or defective parts can cause production losses and increase costs because of stoppages. d)Availablity of qualiyied, technically competent personal to be responsible for equipment operation.e) Total production and production-rate requipments. Product variations and frequency of design changes. f)Joining methods required. g)Assembly times and costs. h)Assembly lines or system configuration, using simulation, including material handling.译文 1. 自动生产线 使用自动生产线可以利用专用、多功能机床来实现最大程度的自动化。自动生产线实质是那些由工件传送装置连接起来的按所需顺序布置的单个工位的组合，并且通过连锁控制集成为一体。工件在工位间被自动传送，每个工位都装配有用于加工、测量、工件再定位、组装、清洗或其他操作的卧式、立式及倾斜式设备。自动生产线的两大主要类别上旋转式和直列式。 自动生产线的一个显著优点是它们允许同时完成大量的操作。相对来说，对机加工工件表面或平面的数量没有限制，因为装置可介入自动生产线，实际上在任意位置能使工件翻转、旋转或定向以便完成加工操作。工件重定位也使倾斜主轴箱的数目减至最小，使操作在最佳时间完成。经常可进行从原始铸件或锻件到成品件的完整加工。 一个或多个成品件在一条带有每个传输系统标志的自动生产线上生产，传输系统使部件从一个工位运动到另一个工位。这类生产线的生产效率通常为50%85%，由一条生产线生产各式各样部件时为50%，由一条生产线大批量生产一个部件时达85%，这取决于工件和如何操作自动生产线（材料处理方法、维护程序等。 所有类型的机加工操作，如钻削、攻丝、铰削、镗削和铣削，在自动生产线上被经济地组合在一起。诸如车削和表面加工的车床式操作也在直列式自动生产线上完成，工件在选择的机加工工位上旋转。车削操作在机床部件完成，多刀架通过安装在隧道式桥形装置上的滑轨进给。工件定位在中心位置，由在每个车削工位上的卡盘带动旋转。直列式自动生产线上CNC的车削工位可供使用。CNC装置允许我们很容易地改变机器工作周期以适应工件设计的改变而且用于调整自动刀具。 当工件在传送机上移动时通过将零件组装到工件上，经常可以获得连续生产线上最大的生产经济效益。在传送加工过程中，能够对诸如轴衬、密封垫、威尔士衬套和保温管等零件进行组装、机加工或测试。完成部件局部装配后也可进行 自动螺帽扭转。 如果能使用合适的机加工装置并随后进行良好的操作，在自动生产线上进行深钻孔或铰削是一项理想的应用。球面座和其它表面的仿形镗削和车削可用仿形控制单点进入工件完成，因此取消了昂贵的专用成形刀具。对铰孔或镗孔的测量以及自动刀具的调整是在自动生产线上进行的，以保持精确的公差。 有时在自动生产线上进行的非常规加工包括磨削、环形齿轮的感应加热冷缩配合压在飞轮上、阀座的感应淬火、深度辊压以施加预压载荷和抛光。自动生产线很早就用于汽车工业高效率得生产相同部件，手工零件加工量极少。除了减少劳动力需求外，这种生产线能保证低成本生产标准始终如一的、高质量零件。它们不再局限于粗加工，现在已经常取消了诸如抛光和搪磨这样的后来工序。目前，对自动生产线的需求越来越多，用来处理少量的小尺寸的相似的或甚至不同的零件，用于生产经营的快速转换。内置柔性，即重新布置和互换机加工设备的能力，以及提供空转工位增加了每个自动生产线的成本，但是在经常重新设计产品的情况下这些特性是经济可行的。现在许多这样的生产线已用在非汽车领域里来满足少量的生产要求。现在用于减少零件更换时间的特殊性能包括标准尺寸、模块结构、安装在自动生产线主托架上的互换性夹具、可互换性的夹具零件、借助选择开关将不同的部件锁定在具体工位上的能力和可编程控制器。产品设计也很重要，如可能在不同的零件上应提供常见的移动和夹紧用的表面。2. 可编程序逻辑控制器可编程逻辑控制器（PLC）是一种固态电子装置，它利用已存入的程序来控制机器的运动或工艺的工序。PLC通过输入/输出（I/O）装置信号发出控制信号和接受输入信号。PLC依据以存入程序所规定的逻辑控制输出装置响应的激励。输入装置由限位开关、按钮、手轮、开关、脉冲、模拟信号、ASCII系列数据和来自于绝对位置解码的二进制或BCD数据组成。输出的是驱动电磁线圈、电动起动机、继电器、指示灯等设备的电压或电流电平。其他输出装置包括模拟装置、数字BCD显示、ASCII兼容装置、伺服变速驱动器、甚至计算机。 当通用汽车公司和其他制造商们正在试验看能否有另一种方法来销毁型号转变过程中机床的所有布线控制面板和其他生产设备时，PLC被研制成了（大约在1968年）。这种年度厉行工作是必要的，因为控制面板的重新布线比购买新的控制面板要贵得多。 汽车公司与许多控制设备制造商打交道，请他们开发一个控制系统，这个系统要有较长的生产寿命而无须主要线路重新布线，并且能被工厂人员所理解和维护。这个新系统被称作“可编程控制器”。PLC的处理器部分由中央处理器和存储器组成。中央处理器(CPU)是处理器的“交通控制器”，存储器储存信息。从输入装置来的信号进入处理器后，经输入模块整理成处理器逻辑单元可接受的电压电平。处理器监测I/O的状态，然后依据储存在PLC存储器中指令更新输出。例如，处理器可被编程以便当连接限位开关的输入位真时（限位开关闭合），连在输出上的输出装置被连通，例如，这个输出装置可以是电磁线圈。处理器通过存储器记录下这个指令并与每次检测相比较以确定限位开关是否真正闭合。如果闭合，处理器通过接通输出模块接通电磁线圈。诸如电磁线圈或电动机之类的输出装置被连接到输出模块的接线柱上，并从处理器接受它的位移信号。实际上，处理器在完成一系列长而复杂的逻辑判断。PLC按顺序并根据存储的程序来执行这样的判断。同样地，模拟 I/O装置允许处理器依据信号的大小而不是其接通或关闭来做判断。例如，处理器可被编程为根据锅炉实际温度（模拟输入）与所需温度的比较来增加或减少流向锅炉的蒸汽（模拟输出）。这通常是用处理器的内置PID（比例，积分，微分）能力来实现的。因为PLC是“基于软件的”，其控制逻辑功能可通过对存储器再编程而改变。键盘编程装置使修改的程序的输入更方便，该程序可以被设计成使现有机器或工序以不同顺序运行，或响应不同水平的激励或激励组合。只有当涉及到附加的更改的或重新定位的输入/输出装置时，才需要修改硬件。 3. 自动化组装 生产过程中的组装包括把特定产品的所有元件和组件安装到一起、对产品进行固定、进行性能检测和功能测试、贴标签、区分良次性、包装并为最后的使用作好准备。与切削、磨削、焊接这样的加工方法相比组装的独特之处在于，这些工序大部分只包括几个甚至可能只有一个规则。大多数这样的非组装操作离开设备就无法进行。因此，自动化组装方法的开发就成为必然，而非可有可无。另一方面，在一台机器上可能要采用多种固定方法进行组装，诸如铆，焊、上螺钉和使用粘合剂，以及自动选件、探测、测量、功能测试，粘标签和包装。组装操作工艺的状况仍未达到标准水平，在该领域仍在使用大量的人工操作。组装在传统上已经成为直接劳动力成本最高的领域之一。有时，组装费用占生产成本的50%或更多，通常是20%50%。然而，设计师与生产技师之间紧密的合作会最终减少甚至在一些情况下排除对组装的需要。一旦需要组装的时候，改善产品的设计或重新设计能够简化自动化（包括全自动和半自动）组装程序。自动化组装的考虑 在采用自动化组装之前，需要考虑几个因素。其中包括该工序自动化的实用性、经济因素与合理性模拟、管理和劳动关系。决定自动化组装的实用性时需要仔细考虑以下因素：a)组装中的零件数量。B)与生产率、组装能力、自动处理能力和检测能力相关的零件设计（材料、外形、规格、体积公差和重量）。C)组装件的质量。超出公差或有缺陷的零件会由于故障造成生产损失和增加成本。D)需要合格的技术过硬的工作人员负责设备操作。e)生产总量和生产率要求。f)产品种类和设计要求。g)所需的联合方法。h)组装次数和成本。i)包括材料处理在内的组装线或系统布局，用模拟的方法。