Question 6 of 6: Flexible Manufacturing Systems and Local Area Networks

Question 6: Flexible Manufacturing Systems and Local Area Networks (20 marks)

Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.

(a) Principle of Flexible Manufacturing Systems and Their Capital Cost

A flexible manufacturing system (FMS) integrates a group of CNC machine tools (and, often, robots for loading/unloading) with an automated material-handling and storage system — conveyors, automated guided vehicles, or a robot transfer arrangement — all coordinated by a central (typically hierarchical) computer control system. That control system schedules which part goes to which machine and in what order, downloads the correct NC program and tooling instructions to each station, and tracks part status through the system, allowing a scheduled mix of different part types to be processed largely without manual intervention, including in random or arbitrary order rather than one batch at a time.

An FMS requires major capital investment because it is engineered and commissioned as one integrated system rather than purchased as separate, off-the-shelf machines: it needs multiple CNC machining centres, a sophisticated automated material-handling and storage subsystem, automatic tool-changing and tool-management capability across all stations, the central scheduling/control computer and its software, and the systems-integration and commissioning effort to make all of these work together reliably — plus staff training on a system considerably more complex than a set of stand-alone NC machines. This up-front cost is only justified when the resulting flexibility and reduced labour/lead-time genuinely offset it over the system's production life.

(b) Why an FMS Produces a Wide Range of Lot Sizes Economically

Because an FMS's routing and processing are governed entirely by downloaded computer programs and by automatically exchanged tooling/fixtures rather than by manual machine setup, changing from one part type to another (or interleaving several part types) requires essentially no manual changeover time — the controller simply calls a different part program and directs the part along a different route through the same physical machines. This lets the system economically process anything from a single part (true one-off, mass-customized production) up through moderate batch sizes, in contrast to a dedicated hard-automation transfer line, which is economical only at very high volume of one part type because its physical tooling changeover is slow and costly. The FMS's flexibility is therefore not merely qualitative variety but genuine economic viability across a wide span of lot sizes, because the cost that would normally scale with the number of setups (manual changeover) has been engineered out of the system.

(c) Function of a Local Area Network in an FMS/CIM Context

The local area network (LAN) is the communication backbone that links the FMS's central (host) computer, the individual CNC machine controllers, robot controllers, and material-handling/storage controllers, allowing them to exchange part programs, scheduling and dispatch commands, and real-time machine/part status data. This real-time exchange is what lets the central controller coordinate the whole system as one integrated unit rather than a set of independent machines, and it is also the mechanism by which the FMS is connected upward into the broader CIM hierarchy — to the CAD/CAPP systems that originate part programs and process plans, and to higher-level production-management or ERP systems that need current shop-floor status — keeping data consistent and current across every level of the enterprise rather than isolated at the individual machine.