Production planning and scheduling for injection moulding of pipe fittings A case study

The present study considers the development of a production planning and scheduling model for injection moulding of PVC pipe fittings in a local factory. The objective is to minimize the total costs of production, inventory, and shortages. A three-stage sequential procedure is used to solve the problem. The total problem domain is divided into three subproblems by mould-machine grouping. Each subproblem is then solved as a single-machine, multi-product, capacity lot-sizing problem, with a three-month planning horizon. A linear, zero-one goal programming approach is used to generate the solution. Finally, the production plan of the first month is decomposed and scheduling for each individual machine is carried out by a heuristic procedure. Comparison of the results show that the new procedure can substantially reduce both shortage and inventory costs.