Column WIP limits…
… are a waste of effort and resources. Because only one column can be the constraint, it follows that the majority of interventions (on the other columns!) are actually wasted.
“Fixing” a non-constraint is waste. Fixing the constraint (Herbie!) is the real gain.
This is completely unnecessary, considering that those bottlenecks were created artificially.
(Note well, there is a distinction to be made between a bottleneck and a constraint!).
Quoted from: Tame the Flow.