Hitachi Tool dropped Lean and let one bottleneck set the clock

Lean, built for Toyota's high-volume, low-variety world, did not fit Hitachi Tool Engineering's job-shop environment. The company tried it repeatedly and each time performance worsened, forcing a retreat to earlier methods.

The Theory of Constraints offered a different lens: identify the single constrained step, then run everything at its pace. The plant used Drum-Buffer-Rope and buffer management to synchronise work around its bottleneck.

It is described as the classic case of a methodology (Lean) that did not apply being solved by theory of constraints, and it shows that the flow principles behind both Toyota and Ford are real but must be adapted to the environment.

Find the constraint, not the waste

Time spent on a non-bottleneck is inventory, not throughput.

A buffer in front of the constraint keeps it starve-free.

The rope limits early release, so work does not pile up.

A workflow is bounded by its slowest constraint, so improving that constraint lifts the whole flow, while improving everything else just builds unneeded inventory.

The implementation improved production performance in a plant where Lean had failed, and became a documented example of matching the method to the production environment. The same research group later noted the limits of Drum-Buffer-Rope, making it an honest case rather than a universal cure.