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Chris Fox's Engineering Section

Optimised Production Technology

Optimised Production Technology (OPT) is concerned with overcoming problems set by having machines with different production rates.

An operation at which the rate of production is comparatively low is termed a bottleneck. Because bottlenecks restrict the flow of materials, they should be utilised as fully as possible in order to maximise output.

At operations following a bottleneck, the maximum rate of production is that of the bottleneck: extra work cannot be created part of the way along the line. Upstream, operations can work faster than the bottleneck, but in so doing they produce inventory. One solution is to stagger workers' breaks in order to ensure there is always someone operating the bottleneck. Also, as non-bottlenecks are idle for part of the time, their operators could be given other work to do during that time.

Another OPT principle breaks the idea that the transfer batch - the lot size from the parts point of view - necessarily equals the process batch - the lot size from the resource point of view. The recommendation is that part of a process batch be transferred before the rest. Furthermore, OPT states that the process batch should vary according to machine capacity, with large batches at bottlenecks to maximise throughput, and small batches elsewhere to minimise lead times and inventory.

OPT believes that 100% utilisation of all machines is not necessarily the best option. Instead, it states, the factory should decide what needs to be produced, then balance the flow of products through the factory. Related to this is the view that optimising each resource will not optimise the factory.

Finally, OPT states that there is an important interaction between capacity and priority. The two should therefore be considered simultaneously, not alternately.

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