The planning and scheduling requirements manufacturing companies in the process sector are very different from discrete. Process is a ‘one-to-many’ relationship where a batched intermediate is used to make several end items, whereas discrete is generally a ‘many-to-one’ process in which several components are used to make an end item.
An example of process manufacturing with complex timing is a brewery:
The wort is made and is stored in storage tanks ready to be filtered and settled in bright beer tanks before being used in filling lines. An essential feature is a scheduling system in this scenario is to accurately model the capacity, inflow and outflow of the tanks. Ignoring any of the three characteristics of tanking means that the availability of the tank is at best approximated, and compromises the ability of the scheduling system to make most efficient use of the tanks and subsequent resources.
There is often a preferred sequence of processing the beer through the filters to minimize the filter cleans (Clean in Place) and another for the packing lines to minimize changeover times. In addition there will be requirements for cleaning for the tanks typically when they are emptied or if they remain empty for a defined maximum period.
In the video, you will see a multi-pass rule that:
1) Optimizes the packing based on dues date and packaging size.
2) Schedules of Clean-In-Place of the filter.
3) Schedules CIP in the bright beer tanks.
4) Final sequencing of all actions to create a complete schedule from tanks to packaging, including all maintenance activity required.
The output from the schedule will be the sequence of packing on each line, the filling and emptying events at each bright beer tank and the materials usage in terms of fermented beer.