Production and shipment planning for Project Based Enterprises: Exploiting learning-forgetting phenomena for sustainable assembly of Curtain Walls

The production and shipment planning for Project Based Enterprises in the Curtain Walls industry is investigated in order to manage the typical trade-off between the assembly plant and the installation site requirements. Given the limited and intermittent nature of the production in large construction projects, empirical evidence is firstly provided about the impact of learning-forgetting phenomena on the assembly pace and the opportunity to include them into the planning process to generate more feasible plans and not to expose workers to excessive stress. A methodology is developed in order to assign proper values of learning-forgetting parameters to panels on the basis of features that, despite of the engineer-to-order nature of products, can survive in different projects. An optimisation model for mid-term production and shipment planning is then proposed, including learning-forgetting in cycle times, installation sequence-based restrictions, and container saturation. Costs due to idle time on the assembly line, setup, overtime, less than full load transports, and capital ones are then minimized by exploiting Constraint Programming and Large Neighborhood Search. The application of the model to an actual project has outlined its capability to support a company on both project decision-making and operational levels.