Description:
This paper deals with proportional lot sizing and scheduling (PLSP) and gives some insights into the properties of this problem. Such insights may be useful for developing heuristic and/or exact solution procedures. The emphasis of this paper is on the multi-level, multi-machine case. We provide a mixed-integer programming model, relate it to other models that can be found in the literature, and discuss characteristics which make solving instances of the PLSP-model become a hard task.