Bottleneck Capacity Analyzer

How this works

A production line's real capacity is set by its slowest step, not its average or its fastest step. Each step's cycle time (minutes to make one unit) and the time available per day convert to a capacity for that step; the line as a whole can never run faster than the smallest of those numbers. This engine computes each step's capacity, picks the minimum, and compares it to demand so the gap is explicit.

Improving a step that isn't the constraint doesn't change the line's output at all, since the slowest step still caps it. This is why identifying the actual constraint matters more than optimizing steps at random.

Key terms

• Cycle time: minutes it takes one unit to pass through a single step.
• Available time: total minutes per day the line is running (shift length minus planned downtime, breaks, etc.).
• Capacity: units per day a step can produce, equal to available time divided by cycle time.
• Constraint (bottleneck): the step with the lowest capacity, the one that sets the line's real output.
• Capacity gap: demand minus the line's real (bottleneck) capacity, positive means demand exceeds what the line can produce.

Assumptions

• Cycle times are steady-state averages, not distributions
• No changeover or setup time between steps is modeled
• Two or three named steps in series, all on the same available-time schedule

Limitations

• Not a full routing network, only a simple in-series line
• Does not model buffer or work-in-process dynamics between steps
• Does not account for step-to-step variability or downtime differences

Sources

Cycle-time-to-capacity conversion and the min-of-steps bottleneck rule follow Goldratt and Cox, The Goal, the same Theory of Constraints source already used in Warehouse Throughput Bottleneck and Contribution Margin per Constraint Hour.

Worked example

A two-step line has a 2-minute cycle time at Step A and a 3-minute cycle time at Step B, with 480 minutes available per day. Step A can make 240 units/day; Step B can only make 160. The line's real capacity is 160 units/day, set by Step B, regardless of how fast Step A runs. Against 150 units/day of demand, that's 10 units/day of spare capacity. Push demand to 200 units/day and the same line is now 40 units/day short, and speeding up Step A alone would do nothing to close that gap: only improving Step B would.

Common use cases

• Identifying which process step to invest in improving first
• Checking whether a line can support a demand increase before committing to it
• Explaining to a team why speeding up a non-constraint step didn't raise output
• Feeding a capacity figure into Order Feasibility Planner for a specific order