93 FIBRES & TEXTILES in Eastern Europe July / September 2007, Vol. 15, No. 3 (62) n Introduction Due to higher standards of living and rapidly changing fashion trends, cloth- ing manufacturers have encountered unexpected demands and diversity. In order to respond as fast as possible to model and quantity changes and to pro- duce high-quality, low-cost products, the manufacturers are favouring new pro- duction systems which are based on JIT. Because of its lexibility and simplicity, modular manufacturing has begun to be implemented in some organisations. The American Apparel Manufacturing Association has deined modular manu- facturing as “a contained manageable work unit of 5 to 17 people performing a measurable task. The operators are inter- changeable among tasks within the group to the extent practical and incentive com- pensation is based on the team’s output of irst quality output” [1]. In a modular sys- tem, processes are grouped into a module instead of being divided into their small- est components. As a rule, fewer num- bers of multi-functional operators work on the machines which are arranged in a U-line. All the operators in the group are responsible for the quality of each item that are produced in the line. The system works when a problem of qual- ity is reached; the operators in the group have to coordinate their quality work, which leads to an increase in quality. The modular system works on the principle of pull-type production systems, in which the job order comes from the last step to previous steps. Because of this, the amount of work in process is low, even working when no inventory is possible. n Review of the literature The modular system was irst implement- ed at Toyota in 1978 as part of JIT, and was known in the 1980s in the West as the Toyota Sewing System. Monden gave this system a U-turn layout and claimed that the main advantage of that system was that the amount produced can eas- ily be arranged by changing the number of operators working in the system [2]. Gilbert showed that the main advantage of the system was the low amount of the work in process [3]. In 1990, Kuler & Dewitt reached encouraging results, and claimed that it was possible to produce quality products at much lower costs. They also determined that the throughput time of the products in the system was much shorter than in conventional sys- tems. Furthermore, the system was quite resistant to worker turnover [4]. When the working principles of the systems in literature are analysed, it is seen that various researchers worked on different systems with different motion principles. The common point of the different studies is that the researchers have preferred to analyse the system by using simulation. In 1991, Wang & Ziemke simulated a system which was working on the motion principles based on the Toyota Sewing System. In this system, the following principle is stated: the items always move forward in the system, while the operators move forward with the item and then move backward for additional work. In the Toyota system, the operator moving backward for inding a work piece can interrupt the operator if he cannot ind any work piece waiting to be sewn. Wang & Ziemke found that the system showed high performance, even though the operation times of each station varied considerably among each other. They also determined that after some time the operators formed their own work patterns [1]. Schroer et al. constructed a simula- tion package which is suitable for use in clothing manufacturing companies. This package can simulate the system accord- ing to three principles of motion, which are the rabbit chase, the Toyota sewing system and the mixed manufacturing module. In the rabbit chase, the opera- tor works on all machines sequentially. For the mixed manufacturing module, the researchers described the bundle and time limits which are the basis for the de- cision taken by the operator [5]. In 1993, Schroer & Black dealt with the modular system as manned cells and offered to use decouplers which separate and link the cell, and function as a balancing ele- ment for different operation times [6]. Black & Chen constructed linked cells in the system according to the number of workers in the system, and added decou- plers through that system. They studied the effects of changing the capacity of decouplers on the system [4]. n Experimental Model description The modular system can readily be app- lied in irms that mainly produce stand- ard products. In this study, the system is designed for an apparel company pro- ducing men’s, women’s, and children’s casual and sports wear. The sweatshirt was chosen as the base product due to the high and constant demand for this prod- uct. After establishing the base product, the operational low for that product was determined. The operations which are conducted on the same type of machine are combined together. The standard times for each operation are determined, and the combined operations times are added to all of them. Standard deviations for each operation were taken as 10% of the operation time. The Promodel Simulation Package was used in the modelling, which was con- ducted in 3 steps; deine, detail and dis- play. In the program, information about the performance parameters was collected as statistics. Three different motion principles were designed for the modular manufacturing model. The change in system perform- ance was analysed by changing the number of operators and the allowed stock on hand. Moreover, the bottleneck Analysis of Modular Manufacturing System in Clothing Industry by Using Simulation Fatma Kalaoğlu Canan Saricam Istanbul Technical University Faculty of Textile Technologies and Design, Instanbul, Turkiye E-mail: saricamc@itu.edu.tr Abstract In this study, an application of the modular system in the clothing industry by using the ProModel Simulation package is presented. The modular system was designed for a base product working on three different motion principles which differ in some way from the ones presented in literature. The performance of the system was determined in terms of productivity, operators and machine eficiency, throughput time and work in process. Key words: modular manufacturing, simulation, pro-model, clothing.