外文原文：Group TechnologyGroup technology (GT) is a very important methodology in todays manufacturing significant. The reason for this is that group technology, when utilized to its fullest extent, can affect most areas of manufacturing, including design, process planning, scheduling, routing, factory layout, procurement, quality assurance, machine tool utilization, tool design, producibility engineering, and assembly.1 IntroductionGroup technology is a simple concept that is used widely in various forms. For a variety of reasons, it is logical to collect and associate things based on features that they have in common. This approach is familiar to everyone for plants, animals, and chemicals. Such organizational structures have also been used for hardware and other obviously similar products within the manufacturing world. Group technology represents structured categorization of particular value to the manufacturing community. It is already widely used; perhaps 50% of manufacturing companies use some form of GT.Bath or lot production suffers from many inefficiencies due to part variety and the general-purpose nature (flexibility requirements) of machine tools in use on the shop floor. In fact, a Cincinnati Milacron study showed that 95% of the time a part spends on the shop floor is idle time, the other 5% is divided between setup and teardown of the machine tool. The future breakdown of the 5% of on-machine time was developed by Dunlap. Based on this estimate, only 24% of the 5% is time which actually involves cutting; i.e., parts are being machined during only 1.2% of the total time spent in manufacturing. Group technology makes possible the application of several methods of analysis which assist in making batch production more efficient by reducing part variety via part families and improving throughout and work-in-process inventory. It is for this reason that group technology is becoming a key concept in manufacturing.2 DefinitionManufacturing philosophy to some, fundamental building block for more efficient production to most, group technology is a simple concept which utilizes/exploits similarities for more efficient production in bath manufacturing. Group technology usually classifies parts in the form of a code which is assigned to each part based on its shape or production processing characteristics. In use, coding parts assists in the control of planning and processing. This added control, which exploits similarities, leads to economies in the overall manufacturing process. The actual operator on the shop floor may never know this code, but designers, engineers, and planners find it an invaluable tool, allowing them to do more productive and useful analysis.3 General BenefitsIn practice, group technology is really nothing more than an information/indexing system. However, because of its focus on part design and processing similarities, analysis is possible which creates manufacturing economies of scale, encourages standardization, and eliminates duplication in design and process planning.Mass production enjoys the benefits of what are called economies of scale. Economies of scale achieved by processing a large number of parts over the same workstations or equipment. This result in less labor per part, more efficient machine utilization, and a faster turnover of inventory. Batch production in the past has not enjoyed economies of scale because of the need to remain flexible for changing part types and products. However, by grouping parts into families based on their similarities, much of the manufacturing processing of these parts can be done on entire families. This increases the number of parts processed with the same equipment conditions, thereby permitting some of the economies of scale of mass production.Standardization is achieved in both design and part process planning. Essentially, group technology creates an efficient design retrieval system since parts have been code based on shape. Similar design are located quickly and aspects such as part tolerances and producibility can be better understood, more easily applied, and kept more consistent from design to design. When standardized process planes are developed and include in the group technology code, new parts and repeat orders can follow similar processing routes through the shop floor, simplifying scheduling and flow through the shop.Group technology eliminates duplication. In both design and process planning, there is much les “reinventing of the wheel” since there is sufficient retrieval of standard designs and process plans.4 Application of GT in Process PlanningAlthough many areas of business operation can benefit from GT, manufacturing, the original application area, continues to be the place where GT is most widely practiced. Two important tasks in manufacturing planning and manufacturing engineering are scheduling and process planning. Job scheduling sets the order in which parts should be processed and