Scheduling issues for environmentally responsible manufacturing: The case of hoist scheduling in an electroplating line

This article explores the possibility of taking into account environmental constraints in scheduling solutions for a “cleaner” treatment surface. In such an industry, the key point to control is related to the handling of products from one bath to another (or tank) by hoists. Mathematical models (known as hoist scheduling problems) involved in the hoist scheduling maximize the shop throughput (maximum productivity) assuming implicitly that the environmental cost and impact of each treatment are constant as long as each soaking duration (processing time) stays in a time window [min value; max value]. When taking into account all cost parameters, a nonlinear global cost function can be created. Then, the schedule can be improved from the environmental point of view by using a nonlinear optimization. Finally, the well-known triangle quality–cost–delay is improved considering a new dimension and becomes a tetrahedron quality–cost–delay–environment.