Integrated planning and scheduling with due dates in corrugated board boxes industry

Abstract

An integrated approach that solves the cutting stock problem and scheduling is considered in this article. The main challenging characteristics of this problem are given by its combinatorial nature, as well as the nonconvexities appearing in the formulation. Scheduling decisions are directly affected by cutting patterns and present changeover times that are sequence-dependent. Given the problem complexity, in general, cutting stock optimization has been considered independently from the scheduling problem. However, a cutting plan that defines the sequence in which patterns are processed is essential in order to obtain a solution in the context of corrugated board boxes industry. In order to obtain a global solution, the approach that has been developed uses a disjunctive technique to transform the original nonconvex formulation into a mixed-integer linear programming (MILP) model; whereas a continuous time representation is assumed to model sequencing decisions by applying general and immediate precedence constraints. Both scheduling models are presented and compared in three examples, showing efficient solutions for the integrated problem.