Determination of Constraint Buffer Size for Drum-buffer-rope Considering System’s Fluctuation Factor

 Buffer size for drum-buffer-rope (DBR) affects lead time of the production and throughput, and it has an influence on product competitiveness. Aiming at the problem that static buffer size cannot be adjusted according to fluctuations in the production system, an approach is proposed to estimate buffer size dynamically. The three factors which have an impact on constraint buffer size are analyzed and the buffer size to offset fluctuation caused by fluctuation of process before the constraint, number of process before the constraint and fluctuation of the constraint via G/G/1 model estimated. Also estimated is the minimum buffer size to avoid bottleneck starvation caused by machine failure and machine maintenance. On this basis, a method which can adjust buffer size dynamically based on simulation is proposed. A production example is given, which proves the validity and usability of the proposed method.