Int. J. Computational Science and Engineering, Vol. X, No. Y, 200X 1 Copyright © 200X Inderscience Enterprises Ltd. Input-output control order release mechanism in a job-shop: how workload control improves manufacturing operations Maria do Rosário Alves Moreira* and Rui Alberto F.S. Alves Faculty of Economics, Universidade do Porto, R. Dr. Roberto Frias, 4200-464 Porto, Portugal E-mail: mrosario@fep.up.pt E-mail: ralves@fep.up.pt *Corresponding author Abstract: This paper presents and evaluates an order release decision rule in a job-shop, based on the input-output control concept. The order release mechanism is part of a global decision-making scheme that includes four main decisions: accept/reject orders, define the order’s due date, release the accepted jobs and dispatch it on the shop floor. This paper also presents an evaluation of two acceptance rules, four release mechanisms, and two dispatching rules, using four levels of due date tightness. Extensive simulation experiments were performed to compare the different decision rules, using several criteria: mean tardiness, percent tardy, mean absolute deviation, mean queue time in the shop floor and in the system, and machine usage. We conclude that considering the four decisions simultaneously improve the job-shop performance, and planning both the input and the output when deciding to release a job, leads to an improvement of the operational performance measures. Keywords: job-shop; input-output control; order release; simulation. Reference to this paper should be made as follows: Moreira, M.d.R.A. and Alves, R.A.F.S. (xxxx) ‘Input-output control order release mechanism in a job-shop: how workload control improves manufacturing operations’, Int. J. Computational Science and Engineering, Vol. X, No. Y, pp.000–000. Biographical notes: Maria do Rosário Alves Moreira graduated in Management at the Faculty of Economics, University of Porto in 1994. In 1997, she obtained her Masters degree in Economics at the University of Porto. After doing the scholar programme of management quantitative methods master course, she started her PhD research in the field of workload and input-output control, obtaining her PhD in 2005. She has been teaching Operations Research and Operations Management at Faculty of Economics since 1996. Rui Alberto F.S. Alves graduated in Economics at the University of Porto in 1974. After a few years of work experience, he moved to Rochester, USA, where he received his MS in Operations Research in 1986 and PhD in Business Administration in 1988 from the William E. Simon Graduate School of Business Administration. He is presently a Full Professor in the Management Department of the Faculty of Economics, University of Porto. 1 Introduction In make-to-order production environments the concept of workload and input-output control is of crucial importance to improve manufacturing operations. Despite a clear early concern about workload control (Wight, 1970), input-output control with the four decisions taken into consideration simultaneously is quite recent (Riezebos et al., 2003; Henrich et al., 2004; Stevenson, 2006; Stevenson and Hendry, 2007; Stevenson and Silva, 2008; Weng et al., 2008; Hendry et al., 2008; Moreira and Alves, 2009; Fredendall et al., 2010; Thurer et al., 2011). The first basic research model considers a job as a series of operations to be processed with a limited number of machines that comprise the shop. As the job proceeds along the shop floor, it encounters other jobs competing for the same resources and queues develop at each machine. Most of the research has concentrated on developing mechanisms to prioritise these jobs in order to optimise some shop performance parameter (Yang and Sum, 1994; Holthaus and Ziegler, 1997; Jayamohan and Rajendran, 2000; Reeja and Rajendran, 2000a, 2000b). This control decision is often referred to as ‘dispatching’. The due-date assignment decision is another important decision (Vig and Dooley, 1991; Raghu and Rajendran, 1995; Gordon et al., 2002; Hsu