A two stage approach for hybrid-assembly line design

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Industrial Engineering, Turkey

Approval Date: 2014


Supervisor: ÖMER KIRCA


The aim of the study is to propose an approach for hybrid assembly line design in the make-to-order and mixed-model environment. In this context, the main goal is to reduce lead-time, which is one of the key concepts of competitive markets. A systematic approach was employed for designing of hybrid assembly line in order to achieve the goal. The line is divided into two parts in a hybrid system: while the first part of the line works as a closed-loop system for instant replenishment of Constant Work in Progress (CONWIP) supermarket, the second part of the line works for order fulfillment that starts the fulfillment by pulling semi-finished products from the CONWIP supermarket. At the first phase, a mathematical model was developed to identify the right station to install the CONWIP supermarket, which has an objective function forcing maximization of horizontal balancing of the line. The output of the model was the input for the second phase. Here, the CONWIP levels were identified for each product type using a simulation-embedded optimization tool, which retrieves the inputs from simulation runs in the simulation model of the proposed system. At the second phase, current serial assembly line and the proposed hybrid assembly line were compared considering optimized CONWIP levels, which were previously collected. The performance measures were set as lead-time, WIP level and throughput level. Comparison of the results revealed that hybrid system provides an opportunity for lead-time reduction at a reasonable WIP level.