Bottleneck calculator

Work out how many units each step can make per hour and find the lowest: that step limits the whole line. On the floor it usually shows as a pile of work in front of one step while the steps after it wait. The calculation confirms what you see and tells you by how much the step falls short.

Capacity per hour = machines × 3,600 ÷ cycle time in seconds × uptime. A step with one machine, a 50 second cycle and 90% uptime makes 3,600 ÷ 50 × 0.9 = 64.8 units an hour. Multiply by the hours run per day for daily capacity.

No. A step with two machines in parallel can have the longest cycle time and still make more per hour than a single machine with a shorter one, and a step that is often down for breakdowns or changeovers loses capacity it would have on paper. That is why the calculator counts machines and uptime, not cycle time alone.

In the theory of constraints, a constraint is anything that limits how much the whole system can produce: a machine, a skill, a supplier, a policy or customer demand itself. A bottleneck is a constraint that is a resource on the floor, a step whose capacity is below what is asked of it. If every step can make more than customers order, the limit is demand, not a bottleneck.

Make sure it never waits: keep a small buffer of work in front of it, run it through breaks and changeovers where you can, and check quality before it so it never works on parts that will be scrapped. Pace the other steps to it rather than to their own speed. Only then add capacity, and recalculate, because the bottleneck moves once you fix it.