JOHNSON’S ALGORITHM AND SHORTHEST PROCESSING TIME IMPLEMENTATION TO MINIMIZE MAKESPAN IN FLOW SHOP SCHEDULING FOR HEAD PART PRODUCTION PROCESS IN PT. X INDONESIA

Abstract

PT. X is one of huge companies that focus on kid’s toy manufacturing. PT. X Indonesia is one of subsidiaries of PT. X. There are two plants of PT. X Indonesia in Indonesia which are North Plant and South Plant. Each of plant produce different products. North Plant produce die cast products and South Plant produce fashion doll products. In South Plant there are a lot of varieties of products. Each of product has different specification and difficulties. In making a fashion doll, PT. X Indonesia has separated the fashion doll into 3 main part which are head part, torso part and accessory part. Each of head part has their own specifications and difficulties. The specifications and difficulties make the head part has a different processing time. In managing the manufacturing process especially in head part production process, PT. X Indonesia has to face the scheduling problem. Currently, PT. X Indonesia use Earlier Due Date (EDD) method. In peak season of PT. X Indonesia, EDD method is not suitable enough to cover the tardiness and high amount of penalty costs which are reach IDR 769,500,000.00. Moreover, the makespan of the head part process also reach 49 days. Changing the method that can result an optimal solution to scheduling problem is needed in head part production process. Short Processing Time (SPT) method and Johnson’s algorithm will be implemented to find the most optimal solution for solving the scheduling problem in head part production process. Penalty costs, average tardiness and makespan will be used as the comparison between methods. Method that can give the optimal solution will be proposed to the head part production process. Johnson’s algorithm will be used to the head part production process because by using this method, it can decrease the makespan until 6 days which is 43 days and decrease the costs until IDR 582,280,000.00 which is decreasing the costs 24.3% of the penalty costs by using EDD method.