Fabrication and assembly operations, Part V: Production order sequencing

Between conventional techniques of scheduling and the actual production order sequencing lies a gap which should be bridged to provide a logical system connection between the planning process and the implementation of the shop loading function. Project network techniques, including PERT, generally do not consider the constraints on resources.
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It is true that resource utilization can be extracted from a PERT-type schedule. However, there is no guarantee that the amount of resources required for any scheduled interval of time will not exceed the plant capacity, thereby making the schedule invalid. Also, if the demand for resources associated with the PERT schedule fluctuates severely, the resulting schedule may be expensive. These considerations are especially acute when several project networks compete for limited resources. On the other hand, by definition, sequencing techniques provide a feasible loading of the shop.
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However, this loading is usually accomplished at the hazard of ignoring project goals in favor of local (short-term) increases in facility utilization. An exception is discussed in a report by B. Banerjee,
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which is a treatment of a set of project-oriented heuristics for shop sequencing.