Reactive scheduling in a make-to-order flexible job shop with re-entrant proces...

• Author(s): Gomes, Marta C. ; Barbosa-Póvoa, Ana Paula ; Novais, Augusto Q.
• Date: 2013
• Persistent ID: http://hdl.handle.net/10400.9/2323
• Origin: Repositório do LNEG
• Subject(s): Reactive scheduling; Flexible job shop; Re-entrant process; Assembly; Mixed-integer linear program
• Document Type: Article
• Language: English

Description

A mixed-integer linear programming model is presented for the scheduling of flexible job shops, a production mode characteristic of make-to-order industries. Re-entrant process (multiple visits to the same machine group) and a final assembly stage are simultaneously considered in the model. The formulation uses a continuous time representation and optimises an objective function that is a weighted sum of order earliness, order tardiness and in-process inventory. An algorithm for predictive-reactive scheduling is derived from the proposed model to deal with the arrival of new orders. This is illustrated with a realistic example based on data from the mould making industry. Different reactive scheduling scenarios, ranging from unchanged schedule to full re-scheduling, are optimally generated for order insertion in a predictive schedule. Since choosing the most suitable scenario requires balancing criteria of scheduling efficiency and stability, measures of schedule changes were computed for each re-scheduling solution. The short computational times obtained are promising regarding future application of this approach in the manufacturing environment studied.