Copyright © 2018 Authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. International Journal of Engineering & Technology, 7 (1.1) (2018) 177-183 International Journal of Engineering & Technology Website: www.sciencepubco.com/index.php/IJET Research paper Simulation modeling and analysis of job release policies in scheduling an agile job shop with process sequence dependent setting time K.T. Vinod 1* , S. Prabagaran 2 , O.A. Joseph 3 1 Research Scholar, Department of Mechanical Engineering, Karpagam Academy of Higher Education, Coimbatore, India 2 Professor, Department of Mechanical Engineering, Karpagam Academy of Higher Education, Coimbatore, India 3 Principal, College of Engineering, Vatakara, India Abstract This paper analyses the effects of job release policies, priority scheduling rules and setup times on the performance of a dynamic job shop in a sequence dependent setup time environment. Two job release policies namely, immediate job release and job release based on a specified work-in-process are investigated. A simulation model of a realistic manufacturing system is developed for detailed analysis. The dynamic total work content method is adopted to assign the due dates of jobs. Six priority rules are applied for prioritizing jobs for processing on machines. Several performance criteria are considered for analyzing the system performance. The simulation results are used to conduct statistical tests. Analytical models have been formulated to represent the simulation model for post-simulation studies. These models are found to yield a satisfactory estimation of the system outputs. Keywords: Dynamic job shop, sequence dependent setup, job release, simulation, regression models. 1. Introduction Scheduling involves projecting the manufacturing-related activities of a production system on a time scale. A job shop production system specializes in low-to medium-volume production. Machine tools are selected in a Job shop essentially would be of Multipurpose functioning so as to cater the machining of varieties of jobs without compromising the quality requirement. The job scheduling problem involves finding the sequence of processing the jobs on machines to achieve a specified criterion. Setup time denotes the time that elapses in changing from one product type to another on a machine (Xu et al. 2015). Setup activity is a non-value added activity. In production systems, activities such as obtaining tools, setting the machines, fixing and removing jobs, returning tools, cleaning the machines, inspecting materials, etc. constitute setup time. The setup time can be classified as sequence independent or sequence dependent. In the case of process sequence independent setting time situations, any job setting time is not dependent on previous job. There are some situations in which it may not be realistic to assume that the time required to setup a machine for the next operation is independent of the immediate preceding operation. This can be better explained with the example of paint manufacturing where the same machinery has to be cleaned and used for manufacturing different colours. Such a shop floor is an example of a system operating under Sequence Dependent Setup Time (SDST) environment. SDST environment is characterised by the dependence of the setup time on the current job and also on the previous job that has been processed on that machine. Recent research on scheduling incorporates explicitly setup time in addition to processing time (Allahverdi and Soroush [1], Allahverdi [2]). This results in realistic schedules that lead to better performance of the system. The present research takes into account SDSTs in scheduling jobs on machines. In a manufacturing system with dynamic arrival of orders, jobs arrive at the shop for processing at random points in time. Saad et al. [24] state that there are three stages in production control: (1) order entry, (2) order release and (3) job scheduling. Upon arrival of a job, a due time of completion is assigned. Total work content method is the commonly used procedure for determining the due time of jobs. This method ignores the information on the status of the shop. Due date determination methods that consider the condition of the system in terms of existing work load at the time of arrival of a job are known as dynamic due date methods. In simulation studies it is generally assumed that arriving jobs are immediately released to the shop floor for processing. However, in practice, the arriving jobs are initially collected in a pool and then released for processing according to some criterion. After the job release decision is made, the jobs are dispatched to machines for processing using scheduling or dispatching rules. This paper focuses on the analysis of the effects of job release policies, priority scheduling rules and setup times in a job shop system operating in an SDST environment with the dynamic arrival of jobs. In the present research, due dates of jobs are set dynamically using the dynamic total work content method. Two job release policies are investigated: (1) Immediate job release (2) Job release based on a specified work-in-process (number of jobs undergoing processing in the system). Six priority rules are