A bottleneck is the resource or operation whose available capacity limits the throughput of a defined process, such as the fitting station in a bag-production line.
Capacity analysis identifies the bottleneck by comparing operations on a common basis, usually completed units per hour or day. Consider a line with 420 available minutes per day and three sequential operations taking 4, 7 and 10 minutes per unit. With one dedicated resource at each operation, their capacities are 105, 60 and 42 units per day. The 10-minute operation sets the planning ceiling at 42 units per day, assuming sufficient demand and material supply.
Adding a second independent resource at that operation raises its capacity to 84 units per day. The 7-minute operation then becomes the bottleneck, limiting the line to 60 units per day. Investment appraisal should therefore use the increase in whole-process capacity, from 42 to 60, when estimating potential additional output. Shared operators and rework can change these calculations.
Au sein du DMAIC, bottleneck analysis supports Measure and Analyze by directing attention to the resource constraining flow. Value Stream Mapping shows its position in the process. A Gemba Walk helps validate the calculation against operating conditions, including queues and downstream starvation. A queue alone does not establish a bottleneck: work may accumulate because material needed for the next task is missing. After an improvement, the Plan de surveillance should track completed good units and specify when changes in staffing or product mix trigger another capacity comparison.
