1.1 Research Background
A manufacturing system can be in different configurations, such as serial, parallel, hybrid (a combination of serial and parallel). A serial configuration is widely used for mass production, such as vehicle assembly manufacturing. In a series manufacturing line, a line is often designed with an intermediate buffer between two workstations to transfer WIPs. In a manufacturing system, two serial lines are connected with a conveyor. The inter-line conveyor transfers WIPs from the upstream to the downstream line. In addition, the conveyor system plays an important buffering role in helping the continuous operation during the downtime of a workstation in a line and improves the productivity of a manufacturing system.
Cycle time and reliability of the workstations, are crucial factors that affect the productivity of a manufacturing line. Moreover, unpredictable events in production, such as small and catastrophic breakdowns, can affect the throughput of a line. Some significant studies have been done over the past for the throughput performance of a system using the two-machine-single-buffer model. However, the real-world manufacturing system is more complex, consisting of a different numbers of production lines and stations. Thus, it is important to understand a complex manufacturing system performance throughput under different conditions. This study provides a substantial understanding for the selection of an inter-line conveyor capacity by introducing a random breakdown at a station and studying the WIPs on an inter-line conveyor for different capacities and effect of the same on the throughput performance.
A manufacturing system is comprised of multiple serial lines connected by an inter-line conveyor between any two lines. In principle, when a failure occurs in the downstream line, an inter-line conveyor can reduce the blocking of an upstream line, until the WIP occupies the full capacity of the inter-line conveyor. Similarly, when a failure occurs in the upstream line, an inter-line conveyor can reduce the starving of the downstream line until all the WIPs are used. Several factors are to be considered while designing such a large production line, where the capacity of an inter-line conveyor directly affects the inventory cost of production as well as throughput (Conway et al., 1988). However, such impacts on blocking and starving have not fully quantitatively studied.