Some insights into proportional lot sizing and scheduling

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 a hard task.