1、 1 Flexible Manufacturing As an introduction to the subsequent discussions of production systems and advanced manufacturing technologies it is useful to present a definition of the term manufacturing system. A manufacturing system can be defined as a series of value-adding manufacturing processes co
2、nverting the raw materials into more useful forms and eventually finished products. In the modern manufacturing setting, flexibility is an important characteristic. It means that a manufacturing system is versatile and adaptable, while also capable of handling relatively high production runs. A flex
3、ible manufacturing system is versatile in that it can produce a variety of parts. It is adaptable because it can be quickly modified to produce a completely different line of parts. A flexible manufacturing system is an individual machine or group of machines served by an automated materials handlin
4、g system that is computer controlled and has a tool handling capability. Because of its tool handling capability and computer control, such a system can be continually reconfigured to manufacture a wide variety of parts. This is why it is called a flexible manufacturing system. A FMS typically encom
5、passes: * Process equipment e.g. , machine tools, assembly stations, and robots * Material handling equipment e.g. , robots, conveyors, and AGVs (automated guided vehicles) * A communication system * A computer control system Flexible manufacturing represents a major step toward the goal of fully in
6、tegrated manufacturing. It involves integration of automated production processes. In flexible manufacturin , the automated manufacturing machine and the automated materials handling system share instantaneous communication via a computer network. This is integration on a small scale. Flexible manuf
7、acturing takes a major step toward the goal of fully integrated manufacturing by integrating several automated manufacturing concepts: * Computer numerical control (CNC) of individual machine tools * Distributed numerical control (DNC) of manufacturing systems * Automated materials handling systems
8、* Group technology (families of parts) When these automated processes, machines, and concepts are brought together in one 2 integrated system, an FMS is the result. Humans and computers play major roles in an FMS. The amount of human labor is much less than with a manually operated manufacturing sys
9、tem, of course. However, humans still play a vital role in the operation of an FMS. Human tasks include the following: * Equipment troubleshooting, maintenance, and repair * Tool changing and setup * Loading and unloading the system * Data input * Changing of parts programs * Development of programs
10、 Flexible manufacturing system equipment, like all manufacturing equipment, must be monitored for bugs, malfunctions, and breakdowns. When a problem is discovered, a human troubleshooter must identify its source and prescribe corrective measures. Humans also undertake the prescribed measures to repa
11、ir the malfunctioning equipment. Even when all systems are properly functioning, periodic maintenance is necessary. Human operators also set up machines, change tools, and reconfigure systems as necessary. The tool handling capability of an FMS decreases, but does not eliminate involvement in tool c
12、hanging and setup. The same is true of loading and unloading the FMS. Once raw material has been loaded onto the automated materials handling system, it is moved through the system in the prescribed manner. However, the original loading onto the materials handling system is still usually done by hum
13、an operators, as is the unloading of finished products. Humans are also needed for interaction with the computer. Humans develop part programs that control the FMS via computers. They also change the programs as necessary when reconfiguring the FMS to produce another type of part or parts. Humans pl
14、ay less labor-intensive roles in an FMS, but the roles are still critical. Control at all levels in an FMS is provided by computers. Individual machine tools within an FMS are controlled by CNC. The overall system is controlled by DNC. The automated materials handling system is computer controlled,
15、as are other functions including data collection, system monitoring, tool control, and traffic control. Human/computer interaction is the key to the flexibility of an FMS. 1 Historical Development of Flexible Manufacturing Flexible manufacturing was born in the mid-1960s when the British firm Molins
16、, Ltd. Developed its System24. System 24 was a real FMS. However, it was doomed from the outset because automation, integration, and computer control technology had not yet been 3 developed to the point where they could properly support the system. The first FMS was a development that was ahead of i
17、ts time. As such, it was eventually discarded as unworkable. Flexible manufacturing remained an academic concept through the remainder of the 1960s and 1970s. However, with the emergence of sophisticated computer control technology in the late 1970s and early 1980s, flexible manufacturing became a v
18、iable concept. The first major users of flexible manufacturing in the United States were manufacturers of automobiles, trucks, and tractors. 2 Rationale for Flexible Manufacturing In manufacturing there have always been tradeoffs between production rates and flexibility. At one end of the spectrum a
19、re transfer lines capable of high production rates, but low flexibility. At the other end of the spectrum are independent CNC machines that offer maximum flexibility, but are capable only of low production rates. Flexible manufacturing falls in the middle of continuum. There has always been a need i
20、n manufacturing for a system that could produce higher volume and production runs than could independent machines, while still maintaining flexibility. Transfer lines are capable of producing large volumes of parts at high production rates. The line takes a great deal of setup, but can turn out iden
21、tical in a part can cause the entire line to be shut down and reconfigured. This is a critical weakness because it means that transfer lines cannot produce different parts, even parts from within the same family, without costly and time-consuming shutdown and reconfiguration. Traditionally, CNC mach
22、ines have been used to produce small volumes of parts that differ slightly in design. Such machines are ideal for this purpose because they can be quickly reprogrammed to accommodate minor or even major design changes. However, as independent machines they cannot produce parts in large volumes or at
23、 high production rates. An FMS can handle higher volumes and production rates than independent CNC machines. They cannot quite match such machines for flexibility, but they come close. What is particularly significant about the middle ground capabilities of flexible manufacturing is that most manufa
24、cturing situations require medium production rates to produce medium volumes with enough flexibility to quickly reconfigure to produce another part or product. Flexible manufacturing fills this long-standing void in manufacturing. Flexible manufacturing, with its ground capabilities, offers a number of advantages for manufacturers:
