Definition
Processes with the least productive capacity in value streams that limit the capacity of the system as a whole, and subject to fluctuations in mobility and quality, any process could become a current bottleneck.
In detail
Bottleneck is the process in a value stream with the smallest capacity that limits the capacity of the entire system. Affected by fluctuations in availability and quality, any process can become the current bottleneck. In production management, it addresses the problem that "system output is limited by the weakest link," improving overall efficiency by identifying and optimizing the bottleneck. It is similar to the constraint in the Theory of Constraints but emphasizes dynamism—the bottleneck may shift with changing conditions. Typical outputs include bottleneck identification results (e.g., markings on a process capability table), bottleneck improvement plans, and measures to balance the production line.
Example in practice
A production line has four processes with cycle times of 100, 110, 150, and 90 seconds, and a takt time of 120 seconds. Clearly, the third process is the bottleneck, causing upstream waiting and downstream shortages. After confirming the bottleneck through time observation and a process capability table, the team improved the third process: optimizing internal operations and adding auxiliary staff, reducing its cycle time to 115 seconds. They also rebalanced the operations across processes, increasing overall output and eliminating waiting and shortages.