An assembly line is a production arrangement of workers and equipment in which the product that is being assembled passes consecutively from operation to operation, with each station adding to the work of previous stations, until the product is completed. Assembly line methods were originally introduced to increase factory productivity and efficiency by reducing the cost and manufacturing time required to produce a finished product. Current advances in assembly line methods have been introduced with the same basic objectives: to increase throughput (the number of products produced in a given period of time), and to save money. While assembly line methods apply primarily to manufacturing processes, business experts have also been known to apply these principles to other areas of business, from product development to management.
The introduction of the assembly line to American manufacturing floors in the early part of the twentieth century revolutionized myriad industries and fundamentally transformed the character of business throughout the nation. Thanks to the assembly line, production periods shortened, equipment costs accelerated, and labor and management alike endeavored to keep up with the changes. Today, using modern assembly line methods, manufacturing has become a highly refined process in which value is added to parts along the line. Increasingly, assembly line manufacturing is characterized by "concurrent processes"—multiple parallel activities that feed into a final assembly stage. These processes require a well planned flow of materials and the development of an advanced materials and supply infrastructure.
Just-in-time (JIT) manufacturing methods have been developed to reduce the cost of carrying parts and supplies as inventory. Under a JIT system, manufacturing plants carry only one or a few days' worth of inventory in the plant, relying on suppliers to provide parts and materials on an "as needed" basis. Future developments in this area may include suppliers establishing operations within the manufacturing facility itself or increased electronic links between manufacturers and suppliers to provide for a more efficient supply of materials and parts.
VARIATIONS IN ASSEMBLY LINE METHODOLOGIES
The passage of years have brought numerous variations in assembly line methodologies. These new wrinkles can be traced back not only to general improvements in technology and planning, but to factors that are unique to each company or industry. Capital limitations, for example, can have a big impact on a small business's blueprint for introducing or improving assembly line production methods, while changes in international competition, operating regulations, and availability of materials can all influence the assembly line picture of entire industries. Following are brief descriptions of assembly line methods that are currently enjoying some degree of popularity in the manufacturing world.
* Modular Assembly—This is an advanced assembly line method that is designed to improve throughput by increasing the efficiency of parallel subassembly lines feeding into the final assembly line. As applied to automobile manufacturing, modular assembly would involve assembling separate modules—chassis, interior, body—on their own assembly lines, then joining them together on a final assembly line.
* Cell Manufacturing—This production methodology has evolved out of increased ability of machines to perform multiple tasks. Cell operators can handle three or four tasks, and robots are used for such operations as materials handling and welding. Cells of machines can be run by one operator or a multi-person work cell. In these machine cells it is possible to link older machines with newer ones, thus reducing the amount of investment required for new machinery.
* Team Production—Team-oriented production is another development in assembly line methods. Where workers used to work at one-or two-person work stations and perform repetitive tasks, now teams of workers can follow a job down the assembly line through its final quality checks. The team production approach has been hailed by supporters as one that creates greater worker involvement in and knowledge of the entire manufacturing process.
As new assembly line methods are introduced into manufacturing processes, business managers look at the techniques for possible application to other areas of business. New methods all share the common goal of improving throughput by reducing the amount of time individual workers and their machines spend on specific tasks. By reducing the amount of time required to produce an item, assembly line methods have made it possible to produce more with less.