Also called constraint, theory of constraints
What is a bottleneck?
The one step whose pace sets the pace of everything else.
What else it is called
- Other names
- constraint, theory of constraints
- In French
- goulot d’étranglement
Related entries
Understanding bottleneck
In any sequence of operations one step has less capacity than the rest, and the output of the whole line is the output of that step. This is the central idea of the theory of constraints, and two consequences follow that both feel wrong.
The first is that improvement away from the constraint is worthless in throughput terms. A faster saw ahead of a slow paint booth produces more work in process and the same shipments. The second is that the constraint should never be starved or stopped - it is the only place where an hour lost is an hour lost by the whole plant, which is why it is the one machine that gets its changeovers staged, its maintenance scheduled around production, and its operator covered through lunch.
Bottlenecks also move. A mix shift towards a product that spends longer in one operation relocates the constraint, which is why a plant that solved this three years ago often has an out-of-date answer posted on the wall.
In practice
Buying a faster saw when the paint booth is the constraint produces more work in process and the same shipments. The question is always which step the queue forms in front of.
Frequently asked
How do I find the bottleneck in my plant?
Walk the floor and look for where material waits. The constraint has a queue in front of it and a starved operation behind it. If the piles are ambiguous, compare each station’s cycle time against takt time for your current mix; the station furthest above the line is the constraint.
Should I always eliminate the bottleneck?
You cannot eliminate it, only move it. Every process has a slowest step, and relieving one promotes another. The useful goal is to put the constraint where you want it - on your most expensive asset, where it is easiest to schedule around - rather than to chase it.