Bottleneck

Bottlenecks reveal themselves through several observable symptoms on the factory floor. The most obvious indicator is WIP accumulation: inventory piles up in front of the bottleneck workstation because upstream processes produce faster than the bottleneck can consume. Another sign is high utilization: the bottleneck machine or operator is always busy, with no idle time between jobs. Downstream starvation occurs when workstations after the bottleneck frequently wait for work because the bottleneck cannot feed them fast enough. Delivery delays often trace back to bottleneck overloads. To confirm which step is the bottleneck, compare the cycle time or throughput rate of each workstation — the one with the longest cycle time (lowest throughput rate) is the constraint. Note that bottlenecks can shift: a machine that is the bottleneck for Product A may not be the bottleneck for Product B. In mixed-model production, analyze the bottleneck by product mix, not just individual product. LinePlanner's visual scheduling makes bottlenecks apparent when certain production lines consistently show over-capacity loading.

Goldratt's Theory of Constraints provides a five-step process for managing bottlenecks. Step 1: Identify the constraint — determine which resource limits system throughput. Step 2: Exploit the constraint — ensure the bottleneck is always running productive work with zero wasted time (no unnecessary changeovers, no idle time during breaks, no quality rework). Step 3: Subordinate everything else to the constraint — schedule non-bottleneck operations to serve the bottleneck's needs rather than optimizing local efficiencies. Step 4: Elevate the constraint — if exploitation and subordination are not enough, invest to increase the bottleneck's capacity (add a machine, add a shift, outsource bottleneck work). Step 5: Repeat — once the current bottleneck is resolved, identify the new constraint and begin again. Most manufacturers find that Step 2 (exploitation) alone yields significant improvement, because bottleneck utilization is typically only 60–70% of theoretical capacity due to changeovers, waiting, breakdowns, and producing defects.

Production scheduling strategy should revolve around the bottleneck. The key principle is Drum-Buffer-Rope (DBR) scheduling from TOC: the bottleneck sets the production pace (drum), a time buffer protects the bottleneck from upstream delays, and a rope mechanism controls material release to prevent WIP buildup. In practice, this means scheduling the bottleneck first — ensuring it has a full, optimized sequence with minimized changeovers — and then scheduling all other operations to support the bottleneck's sequence. Non-bottleneck operations intentionally have excess capacity and should not be scheduled to 100% utilization, because they need slack to recover from variability without delaying work to the bottleneck. LinePlanner enables bottleneck-focused scheduling by allowing planners to identify critical production lines and prioritize their scheduling, then fitting supporting operations around the bottleneck sequence.