Reliable shop floor bottleneck detection for flow lines through process and inventory observations: the bottleneck walk

Abstract

Bottleneck detection in manufacturing is the key to improving production efficiency and stability in order to improve capacity. Yet, common bottleneck detection methods in industry and academia lack either accuracy or practicability, or both, for dynamic systems. The new methodology is conducted by the observation of processes and inventories. Blocked processes and full inventories indicate a downstream bottleneck. Starved processes and empty inventories indicate an upstream bottleneck. Through subsequent observations of multiple process states and inventory levels within a system, it is possible to determine the direction of the bottleneck at the given time and hence to find the momentary bottleneck in the system. The shifting of bottlenecks can be observed directly. Work sampling techniques can be used to obtain a long-term picture of the dynamically shifting bottleneck. The new methodology does not require any calculations, statistics, or time measurements. Hence, the method is suited for practical use by shop floor supervisors and clerks. The direct observation of the bottleneck also gives additional information about the underlying causes of the bottlenecks, simplifying the improvement of the system capacity. Extensive field testing of the method received positive feedback not only from management but also from shop floor operators. The method is already in use at the Robert Bosch GmbH, where it is known as the bottleneck walk.

TOC implementation in a medium-scale manufacturing system with diverse product rooting

“…The study confirms what has been observed by some researchers (Roser et al, 2015) that inventories are a good marker of bottlenecks in a system. However, one should address inventories using a deep understanding of the production flow.…”

“…TOC, which is also known as Goldratt's theory, is plainly elaborated and justified by its author with respect to the central idea (Goldratt, 1997;Goldratt & Cox, 1992;Goldratt, Schragenheim, & Ptak, 2000). There are also application proposals, such as managerial methodologies (Chowdhary, 2009;Cox & Schleier, 2010;Dettmer, 1998;Roser, Lorentzen, & Deuse, 2015;Scheinkopf, 1999). As Mabin and Balderstone (2003, p. 570) state, Goldratt theory's distinctive feature is the recognition that there are always limitations to system performance, and despite the complex set of factors influencing it, there are a very small number of elements in the system, usually only one that Goldratt terms the 'constraint', which directly restricts performance.…”

“…A high stock level is a sign that in front of this stock is a bottleneck that significantly affects the waiting inventory. Some authors suggest detecting production bottlenecks by observing inventories during a bottleneck assessment (Roser et al, 2015). Figure 2 presents the inventory wait for each process in the studied manufacturing system.…”

Bottleneck Prediction Using the Active Period Method in Combination with Buffer Inventories

“…Bottlenecks are processes that influence the throughput of the entire system. The larger the influence, the more significant the bottleneck [1] [2] [3] [4].…”

“…The bottleneck walk looks at both processes and inventories to determine the direction in which the bottleneck is likely to be found [1] [21]. This approach is very well suited for practical use in flow lines, although it has difficulties with job shop-type production systems.…”