JE25-110開式雙點(diǎn)壓力機(jī)傳動(dòng)系統(tǒng)的設(shè)計(jì)（含CAD圖紙和說明書）

JE25-110開式雙點(diǎn)壓力機(jī)傳動(dòng)系統(tǒng)的設(shè)計(jì)（含CAD圖紙和說明書）,JE25,110,開式雙點(diǎn),壓力機(jī),傳動(dòng)系統(tǒng),設(shè)計(jì),CAD,圖紙,說明書 附錄2 英語(yǔ)原文 The Computer and Manufacturing Computer Aided Design The computer is bringing manufacturing into the Information Age. This new tool, a long familiar one in business and management operations, is moving into the factory, and its advent is changing manufacturing as certainly as the steam engine changed it 100 years ago. The basic metal working processes are not likely to change fundamentally, but their organization and control definitely will. IN one respect, manufacturing could be said to be coming full circle. The first manufacturing could was a cottage industry: the designer was also the manufacturer, conceiving and fabricating products one at a time. Eventually, the concept of the interchangeability of parts was developed, production was separated into specialized functions, and identical parts were produced thousands at a time. Today, although the designer and manufacturer may not become one again, the functions are being drawn close in the movement toward an integrated manufacturing system, It is perhaps ironic that, at a time when the market demand a high degreed of product diversification, the necessity for increasing productivity and reducing costs is driving manufacturing toward integration into a coherent system, a continuous process in which parts do not spend as much as 95% of production time being moved around or waiting to be worked on. The computer is the key to each of these twin requirements. It is the only tool that can provide the quick reflexes, the flexibility and speed, to meet a diversified market. And it is the only tool that enables the detailed analysis and the accessibility of accurate data necessary for the integration of the manufacturing system. It may well be that, in the future, the computer may be essential to a company’s survival. Many of today’s businesses will fade away to be replaced by more-productive combinations. Such more-productive combinations are super-quality, super-productivity plants. The goal is to design and operate a plant that would produce 100% satisfactory parts with good productivity. A sophisticated, competitive world is requiring that manufacturing begin to settle for more, to become itself sophisticated, To meet competition, for example, a company will have to meet the somewhat conflicting demands for greater product diversification, higher quality, improved productivity, and low prices. The company that seeks to meet these demands will need a sophisticated tool, one that will allow it to respond quickly to customer needs while getting the most out of its manufacturing resources. The computer is that tool. Becoming a “super-quality, super-productivity” plant requires the integration of an extremely complex system. This can be accomplished only when all elements of manufacturing—design, fabrication and assembly, quality assurance, management, materials handling—are computer integrated. In product design, for example, interactive computer-aided-design (CAD) systems allow the drawing and analysis tasks to be performed in a fraction of the time previously required and with greater accuracy. And programs for prototype testing and evaluation further speed the design process. In manufacturing planning, computer-aided process planning permits the selection, from thousands of possible sequences schedules, of the optimum process. On the shop floor, distributed intelligence in the form of microprocessors controls machines, runs automated loading and unloading equipment, and collects data on current shop conditions. But such isolated revolutions are not enough. What is needed is a totally automated system, linked by common software from front door to back. The benefits range throughout the system. Essentially, computer integration provides widely and instantaneously available, accurate information, improving communication between departments, permitting tighter control, and generally enhancing the overall quality and efficiency of the entire system. Improved communication can mean, for example, designs that are more producible. The NC programmer and the tool designer have a chance to influence the product designer, and vice versa. Engineering changes, thus, can be reduced, and those that are required can be handled more efficiently. Not only does the computer permit them to be specified more quickly, but it also alerts subsequent users of the data to the fact that a change has been made. The instantaneous updating of production-control data permits better planning and more0effective scheduling. Expensive equipment, therefore, is used more productively, and parts move more efficiently through production, reducing work-in-process costs. Product quality, too, can be improved. Not only are more-accurate designs produced, for example, but the use of design data by the quality-assurance department helps eliminate errors due to misunderstandings. People are enabled to do their jobs better. By eliminating tedious calculations and paperwork—not to mention time wasted searching for information—the computer not only allows workers to be more productive but also frees them to do what only human beings can do: think creatively. Computer integration may also lure new people? into manufacturing. People are attracted because they want to work in a modern, technologically sophisticated environment. In manufacturing engineering, CAD/CAM decreases tool-design. NC-programming, and planning times while speeding the response rate, which will eventually permit in-house staff to perform work that is currently being contracted out. According to the Tool & Manufacturing Engineers Handbook, process planning is the systematic determination of the methods by which a product is to be manufactured economically and competitively. It essentially involves selection, calculation, and documentation. Processes, machines, tools, and sequences must be selected. Such factors as feeds, speeds, tolerances, dimensions, and costs must be calculated. Finally, documents in the form of setup instructions, work instructions, illustrated process sheets, and routings must be prepared. Process planning is an intermediate stage between designing and manufacturing the product. But how well does it bridge design and manufacturing? Most manufacturing engineers would agree that, if ten different planners were asked to develop a process plan for the same part, they would probably come up with ten different plans. Obviously, all these plans cannot reflect the most efficient manufacturing methods, and, in fact, there is no guarantee that any one of them will constitute the optimum methods for manufacturing the part. What may be even more disturbing is that a process plan developed for a part during a current manufacturing program may be quite different manufacturing program and it may never be used again for the same or similar part during a previous similar part. That represents a lot of wasted effort and produces a great many inconsistencies in routing, tooling, labor requirements, costing, and possibly even purchase requirements. Of course, process plans should not necessarily remain static. As lot sizes change and new technology, equipment, and processes become available, the most effective way to manufacture a particular part also changes, and those changes should be reflected in current process plans released to the shop. A planner must manage and retrieve a great deal of data and many documents, including established standards, machine ability data, machine specifications, tooling inventories, stock availability, and existing process plans. This is primarily an information-handling job, and the computer is an ideal companion. There is another advantage to using computers to help with process planning. Because the task involves many interrelated activities, determining the optimum plan requires many iterations. Since computers can readily perform vast numbers of comparisons, many more alternative plans can be explored than would be possible manually. A third advantage in the use of computer-aided process planning is uniformity. Several specific benefits can be expected from the adoption of computer-aided process-planning techniques: ●?Reduced clerical effort in preparation of instructions. ● Fewer calculation errors due to human error. ●?Fewer oversights in logic or instructions because of the prompting capability available with interactive computer programs. ●?Immediate access to up-to-date information from a central database. ●?Consistent information, because every planner accesses the same database. ●?Faster response to changes requested by engineering of other operating departments. ●?Automatic use of the latest revision of a part drawing. ●?More-detailed, more-uniform process-plan statements produced by word processing techniques. ●?More-effective use of inventories of tools, gages, and fixtures and a concomitant reduction in the variety of those items. ●?Better communication with shop personnel because plans can be more specifically tailored to a particular task and presented in unambiguous, proven language. ●?Better information for production planning, including cutter-life, forecasting, materials-requirements planning, scheduling, and inventory control. Most important for CIM, computer-aided process planning produces machine-readable data instead of hand written plans. Such data can readily be transferred to other systems within the CIM hierarchy for use in planning. There are basically two approaches to computer-aided process planning: variant and generative. In the variant approach, a set of standard process plans is established for all the parts families that have been identified through group technology. The standard plans are stored in computer memory and retrieved for new parts according to their family identification. Again, GT helps to place the new part in an appropriate family. The standard plan is then edited to suit the specific requirements of a particular job. In the generative approach, an attempt is made to synthesize each individual plan using appropriate algorithms that define the various technological decisions that must be made in the course of manufacturing. In a truly generative process-planning system, the sequence of operations, as well as all the manufacturing-process parameters, would be automatically established without reference to prior plans. In its ultimate realization, such an approach would be universally applicable: present any plan to the system, and the computer produces the optimum process plan. No such system exists, however. So called generative process-planning system—and probably for the foreseeable future—are still specialized systems developed for a specific operation or a particular type of manufacturing process. The logic is based on a combination of past practice and basic technology. Computer Aided Manufacturing Numerical Control Numerical control can be defined as a form of programmable automation in which the process is controlled by numbers,letters,and symbols.In NC, thenumbers form a program of instructions designed for a particular workpart or job. When the job changes, the program of instructions is changed .This capability to change the program for each new job is what gives NC its flexibility, It is much easier to write new programs than to make major change in the production equipment. NC equipment is used in all areas of metal parts fabrication and comprises roughly 15% of the modern machine tools in industry today. Since numerically controlled machines are considerably more expensive than their conventional counterparts, the asset value of industrial NC machine tools is proportionally much larger than their numbers. Equipment utilizing numerical control has been designed to perform such diverse operations as drilling, milllng~; ~r~j, gtindlng, :sheetmetal pres~orkingi spot welding, arc welding, riveting, assembly, drafting, inspection, and parts handling. And this is by no means a complete list. Numerical control should be considered as a possible mode of controlling the operation for any production situation possessing the following characteristics: I, .Similar workparts in terms of raw material(e. g., metal stock for machining) 2. The workparts are produced in various sizes and geometries. 3. The workparts are produced in batches of small to medium-sized quantities. 4. A sequence of similar processing steps is required to complete the operation on each workpiece. Many machining jobs meet these conditions. The machined workparts are metal,they are specified in many differentsizes and shapes, and most machined parts produced in industry today are made in small to medium-size lot sizes.To produce each part,a sequence of drilling operations may be required, or a series of turning or milling operations. The suitability of NC for these kinds of jobs is the reason for the tremendous growth of numerical control in the metalworking industry over the last 25 years. Basic Components of an NC system An operational numerical control system consists of the following three basic components: 1.Program of instructions. 2.Controller unit, also called machine control unit (MCU) 3.Machine tool or other controlled process The program of instructions serves as the input to the controller unit , which in turn commands the machine tool or other process to be controlled. Program of instructions The program of instructions is the detailed step-by-step set of directions which tell the machine tool what to do. It is coded in numerical or symbolic form on some type of input medium that can be interpreted by the controller unit. The most common input medium is 1-inch-wide punched cards, magnetic tape,and even 35-mm motion picture film. There are two other methods of input to the NC system which should be mentioned. The first is by manual entry of instructional data to the controller unit .This is time-consuming and is rarely used except as an auxiliary means of control or when only one or a very limited number of parts are to be made. The second method of input is by means of a direct link with a computer .This is called direct numerical control, or DNC. The program of instructions is prepared by someone called a part programmer. Theprogrammer’s job is to provide a set of detailed instructions by which the sequence of processing steps is to be performed. For a machining operation, the processing steps involve the relative movement of the machine tool table and the cutting tool. Controller unit The second basic component of the NC system is the controller unit . This consists of the electronics and hardware that read and interpret the program of instructions and convert it into mechanical actions of the machine tool . The typical elements of the controller unit include the tape reader , a data buffer, signal output channels to the machine tool, feedback channels from the machine tool, and the sequence controls to coordinate the overall operation of the foregoing elements. The type reader is an electrical-mechanical device for winding and reading the punched tape containing the program of instructions . The data contained on the tape are read into the data buffer , The purpose of this device is to store the input instructions in logical blocks of information. A block of information usually represents one complete step in the sequence of processing elements. For example, one block may be the data required to move the machine table to a certain position and drill a hole at that location . The signal output channels are connected to the servomotors and other controls in the machine tool. Through these channels, the instructions are sent to the machine tool from the controller unit. To make certain that the instruction have been properly executed by the machine, feedback data are sent back to the controller via the feedback channels. The most important function of this return loop is to assure that table and workpart have been properly located with respect to the tool. Most NC machine tools in use today are provided with position feedback controls for this purpose and are referred to ae closed-loop systems. However, in recent years there has been a growth in the use of open-loop systems, which do not make use of feedback signals to the controller unit. The advocates of the open-loop concept claim that the reliability of the system is great enough that feedback controls are not needed and are an unnecessary extra cost. Sequence controls coordinate the activities of the other elements of the controller unit. The tape reader is actuated to read data into the buffer from the tape, signals are sent to，and so on. These types of operations must be synchronized and this is the function of the sequence controls. Another element of the NC system, which may be physically part of the controller unit or part of the machine tool, is the control panel. The control panel or control console contains the dials and switches by which the machine operator runs the NC system. It may also contain data displays to provide information to the operator. Although the NC system is an automatic system, the human operator is still needed to turn the machine on and off, to change tools (some NC systems have automatic tool changers), to load and unload the machine, and to perform various other duties. To be able to discharge these duties, the operator must be able to control the system, and this is done through the control panel. The third basic component of an NC system is the machine tool or other controlled process. It is the part of the NC system which performs useful work. In the most common example of an NC system, one designed to perform machining operations, the machine tool consists of the worktable and spindle as well as the motors and controls necessary to drive them. It also includes the cutting tools, work fixtures, and other auxiliary equipment needed in the machining operation. 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 and receives input signals through input/output (I/O) devices. A PLC controls outputs 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 signals, ASCII serial data, and binary or BCD data from absolute position encoders. The outputs are voltage or current levels to drive end devices such as solenoids, motor starters, relays, lights, and so on. Other output devices 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 Corp, and other automobile manufacturers were experimenting to see if there might be an alternative to scrapping all their hardwired control panels of machine tools and other production equipment during a model changeover. This annual tradition was necessary because rewiring 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 rewiring, but would still be understandable to and repairable by 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 director" 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 ou