Production scheduling and routing problem in the textile industry

In this paper we propose a two-phase solution approach to solve a combined routing and scheduling problem occurring in the textile industry where all fabrics are dyed by dye-jets and transported by forklifts. The objective is to minimize the cost of unproductive activities consisting of setup time due to dye-jets cleaning and forklifts waiting time. The first phase solves an integer linear program to assign jobs (fabrics) to dye-jets while minimizing the setup cost. We compare in this phase an arc formulation and a path-based formulation. In the second phase we use a mixed-integer linear program to deal with dye-jets scheduling and both routing and scheduling of forklifts. Experiments are performed on real data provided by a major multinational company and have been conducted using Cplex 12.4.0 and a column generation solver. Optimal solution is obtained in reasonable time.