1、- 1 - 中文 3035 字 English Translation Material 1. 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, connecte
2、d 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
3、 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, sinc
4、e 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. Com
5、plete 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% f
6、or 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, an
7、d 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 toolhold
8、ers 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 i
9、n 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
10、 machine or - 2 - 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 prac
11、tices 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
12、 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
13、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 eli
14、minate 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,
15、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 productio
16、n 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 stat
17、ions 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 soli
18、d-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 t
19、he 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, l
20、ights, and so on. Other output device include analog devices, digital BCD displays, ASCII compatible - 3 - devices, servo variable-speed drives, and even computers. Programmable controllers were developed (circa in 1968) when General Motors Corps, and other automobile manufacturers were experimentin
21、g 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 ap
22、proached 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 pro
23、cessor 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 volta
24、ge 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 outpu
25、t 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 start
26、er, 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 allow
27、s 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 ) Thi
28、s 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, whic
29、h 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
