Simulation and Optimization Model of the Performance of Processes at Signoff Units (A Case Study in Automotive Industry: Saipa Corporation

The present research aims to investigate the feasibility of improving the number and quality of final products at workstations using a simulation-based method. a major challenge faced by senior managers is how to identify bottlenecks of the operating processes. in this article, the signoff process was selected because this procedure was the bottleneck in the factory. the signoff process was modeled to identify the parameters affecting this process that include the number of workstations, manpower, defect per unit, and logistic structure (transferring cars at the signoff unit and supply of spare parts). in this structure, the car sequencing was determined based on the customer demand information during a one-year period (since 1397), as per the data extracted from the saipa corporation sales system, and mapped as a disc distribution function (indicating that 1 and 3 out of every 4 cars sold by the saipa corporation were x100 and x200, respectively). it was further assumed that one product unit entered the signoff unit every 2 minutes. the model was implemented and run by arena software (version 14). the fact that the software returned no error verified the model. in this paper, there are four scenarios: ordering product by customers which is the input of the process of signoff, equipment failure, unavailability of the spare parts, and allocated indirect cost and allocated joint cost. finally, equipment failure is the optimal scenario in this process. the results indicated that about 80% of the existing problems could be addressed by appropriately planning for human resources and optimizing the workstations that contributed the most to the working queues based on their pareto graphs. by applying the mentioned solutions, improvements were also observed in the qualitative indices. for instance, the direct pass rate in busy areas increased from 60% to 90% while the defect per unit (dpu) decreased from 2 to 1.4% at both the wheel alignment and electrical defect identification units. in terms of quantity, the number of output cars increased by 10%