THE EFFECTS OF BUFFER PATTERNS ON THROUGHPUT IN CONWIP FLOW LINES: A SIMULATION STUDY
Keywords:
Release mechanism, CONWIP, buffers, protective capacity, bottleneckAbstract
This research was a simulation experiment which aimed to investigate the effects of buffer patternson the throughput of lines controlled by a CONWIP release mechanism. The hypothetical linessimulated were stochastic 11-station flow lines with the middle station as the bottleneck. ANOVAtests were used for the analysis of the simulation output, followed by Duncan’s Multiple Rangetests. There were 6 buffer patterns which were distinguished by the amount of total buffer capacityand the buffer allocation approaches. The experiment was done at three levels of protective capacity(PC); 0%, 20%, and 40%, and two levels of coefficient of variation (CV) of processing times; 0.05 and0.50. When CV = 0.05, ANOVA tests revealed a significant difference (p < 0.01) among buffer patternsonly for the lines with PC of 0%, whereas when PC = 20% and 40%, there were insignificantdifferences among buffer patterns. When CV = 0.50, ANOVA tests indicated significant differences(p < 0.01) among buffer patterns at all PC levels. The important suggestion is that appropriateallocation of limited buffer capacity, an addition of protective capacity, and a reduction of systemvariation could increase the throughput rates to the desired level.
References
Atwater, J.B. and Chakravorty, S.S. (1994). Doesprotective capacity assist managers incompeting along time-based dimensions?.Prod. Inventory Manag. J., 35(3):53-59.
Bank, J., Carson, J.S., Nelson, B.L., and Nicol,D.M. (2001). Discrete-event System Simulation.3rd ed. Prentice Hall, EnglewoodCliffs, NJ. 594p.
Conway, R., Maxwell, W., McClain, J.O., andThomas, L.J. (1988). The role of work-inprocess inventory in serial productionlines. Oper. Res., 36(2):229-241.
Cox, J.F., Blackstone, J.H., and Spencer, M.S.(eds.) (1995). APICS Dictionary. AmericanProduction and Inventory ControlSociety, Inc., Falls Church, VA, 102p.
Duenyas, I. and Keblis, M.F. (1995). Releasepolicies for assembly system. IIE Trans.,27(4):507-518.
El-Rayah, T.E. (1979). The effect of inequality ofinterstage buffer capacities and operationstime variability on the efficiency ofproduction line systems. Int. J. Prod. Res.,17:77-89.
Goldratt, E.M. and Cox, J. (1986). The Goal: aProcess of Ongoing Improvement. NorthRiver Press, Croton-on-Hudson, NY, 273p.
Hopp, W.J. and Spearman, M.L. (1996). FactoryPhysics. Irwin, Chicago, IL, 668p.
Kadipasaoglu, S.N., Xiang, W., Hurley, S.F.,and Khumawala, B.M. (2000). A studyon the effect of the extent and locationof protective capacity in flow systems.Int. J. Prod. Econ., 63:217-228.
Krajewski, L.J., King, B.E., Ritzman, L.P., andWong, D.S. (1987). Kanban, MRP, andshaping the manufacturing environment.Manag. Sci., 33(1):39-57.
Muralidhar, K., Swenseth, S.R., and Wilson, R.L.(1995). Describing processing time whensimulating JIT environment. Int. J. Prod.Res., 27(4):507-518.
Pritsker, A.A.B., O’Reilly, J.J., and LaVal, D.K.(1997). Simulation with Visual SLAM andAWESIM. 2nd ed. John Wiley & Sons, Inc.,NY, 828p.
Smith, L.D. and Brumbaugh, P. (1977). Allocatinginter-station inventory capacity inunpaced production lines withheteroscedastic processing time. Int. J.Prod. Res., 15(2):163-172.
Spearman, M.L., Hopp, W.J., and Woodruff, D.L.(1989). A hierarchical control architecturefor constant work-in-process (CONWIP)production systems. J. Mfg. Oper. Mgt.,2(3):147-171.
Spearman, M.L., Woodruff, D.L., and Hopp, W.J.(1990). CONWIP: a pull alternative toKanban. Int. J. Prod. Res., 28(5):879-894.
Spearman, M.L. and Zazanis, M.A. (1992). Pushand pull production systems: issues andcomparisons. Oper. Res., 40(3):521-532.
Welch, P.D. (1983). The Statistical Analysis ofSimulation Results. In: Computer PerformanceModeling Handbook. Lavenberg,S.S. (ed). Academic Press, Inc., NY., 399p.
