The most publicized type of modern manufacturing systems is known as the flexible manufacturing system. The development of FMSs began in the United States in the 1960s. The idea was to combine the high reliability and productivity of the transfer line with the programmable flexibility of the NC machine in order to be able to produce a variety of parts. In the late 1960s, such a system was installed for machining aircraft speed drive housings that is still in use today. However, very few of these systems were sold until the late 1970s and early 1980s, when a worldwide FMS movement began.

The FMS is fundamentally an automated, conveyorized, computerized job shop. The system is complex to schedule. Because the machining time for different parts varies greatly, the FMS is difficult to link to an integrated system and often remains an island of expensive automation.

Some common features of FMSs are pallet changers, underfloor conveyor systems for the collection of chips, and a conveyor system that delivers parts to the machine.

An FMS system can usually monitor piece part counts, tool changes, and machine utilization, with the computer providing supervisory control of the production. The workpieces are launched randomly into the system, which identifies each part in the family and routes it to the proper machines. The systems generally display reduced manufacturing lead time, low in-process inventory, and high machine tool utilization, with reduced indirect and direct labor. The materials-handling system must be able to route any part to any machine in any order and provide each machine with a small queue of “banked parts” waiting to be processed so as to maximize machine utilization. Convenient access for loading and unloading parts, compatibility with the control system, and accessibility to the machine tools are other necessary design features for the materials-handling system. The computer control for an FMS system has three levels. The master control monitors the entire system for tool failures or machine breakdowns, schedules the work, and routes the parts to the appropriate machine.

An FMS generally needs about three or four workers per shift to load and unload parts, change tools, and perform general maintenance. The workers in the FMS are usually highly skilled and trained in NC and CNC.