This study deals with optimal layout design by line balancing using simulation modeling. Modeling and simulation are potential tools for analysis of the assembly lines like apparel of a garment manufacturing. The experiment controls the resources of the assembly line process without affecting the real production system. In this study the Arena software, AutoCAD and POM software are employed to model and measure the performance of the existing sewing line of the Ronny t-shirt model. The t-shirt has 12 major parts to be assembled. For each activity, the researcher has taken 15 sampling observations using stopwatch. All the collected data are statistically analyzed using arena input analyzer for statistically significance and determination of expressions to be used to the simulation modeling. Standard simulation model was developed and run for 160 replications. The result shows the line is operating with a line balance efficiency of 72.56%. In the course of action using Opt Quest different types of scenarios had been developed and line balance efficiency increase to 75.3% and the company saves 518,400 birr per year that spent for salary. This arena simulation model has considered the production resources, processing time of each activity and testing different scenarios.

Keywords: - Layout, Line Balance, Opt Quest, Optimization, simulation modeling