Classification of flexible manufacturing systems

There has been some uncertainty concerning the conditions under which a manufacturing system may be termed 'flexible'. To clarify this confusion eight types of flexibilities are defined and described. A FLEXIBLE Manufacturing System (FMS) is an integrated, computer-controlled complex of automated material handling devices and numerically controlled (NC) machine tools that can simultaneously process medium-sized volumes of a variety of part types. tsl This new production technology has been designed to attain the efficiency of well-balanced, machine-paced transfer lines, while utilizing the flexibility that job shops have to simultaneously machine multiple part types. Recently, many new manufacturing facilities have been labelled FMS. This has caused some confusion about what constitutes an FMS. Flexibility and automation are the key conceptual requirements. However, it is the extent of automation and the diversity of the parts that are important; some systems are termed FMS just because they contain automated material handling. For example, dedicated, fixed, transfer lines or systems containing only automated storage and retrieval are not FMSs. Other systems only contain several (unintegrated) NC or CNC machines. Still other systems use a computer to control the machines, but often require long setups or have no automated parts transfer. Some systems are called flexible because they produce a variety of parts (of very similar type, using fixed automation). In most of these examples, the operating mode is either transfer line-like or based on producing batches of si mi lar part types. To help clarify the situation, eight types of flexibilities will be defined and described. Examples or explanations are provided when needed to illustrate a particular flexibility type. Measurement and attainability of each are also discussed. q Machine Flexibility: the ease of making the changes required to produce a given set of part types. Measurement of these changes include, for example, the time to replace worn-out or broken cutting tools, the time to change tools in a tool magazine to produce a different subset of the given part types, and the time to assemble or mount the new fixtures required. The setup time required for a machine tool to switch from one part type to another includes: cutting tool preparation time; part positioning and releasing time; and NC program changeover time. This flexibility can be attained by: (a) technological progress, such as sophisticated tool-loading and part-loading devices; (b) Proper operation assignment, so that there is no need to change the cutting tools that …