A bit of history

The neck of a bottle

However much water is in a bottle, it cannot pour out faster than the neck lets it. Make the bottle twice as wide — it will not flow faster. Widen the neck — it will.

A factory is the same. A shop of ten sections makes exactly as much as its slowest section lets through. It sounds obvious, but for almost the whole 20th century factories were run as if it were not true.

The «utilization» trap, 20th century

Since Taylor's time managers measured utilization: what percentage of the time each machine and each worker is busy. An idle machine was considered a loss, and they tried to load it with anything — even with parts nobody needed yet. The reports looked wonderful: all machines busy 90 percent of the time. But the stocks between sections swelled, orders were late, and money lay on the shelves as half-finished parts.

Goldratt called this the main mistake of factories: loading a machine that is not the bottleneck adds nothing to the output. An hour lost at the bottleneck is lost for the whole plant. An hour saved anywhere else is a mirage.

Andon: the lamp that stops the line

As early as 1924 Sakichi Toyoda — the father of Toyota's founder — built a loom that stopped by itself when a thread broke: there is no point in weaving defects. At Toyota's plants this idea became the andon (Japanese for «lantern»). Above the line hangs a board with lamps — one per section. If something goes wrong for a worker, they pull a cord, their lamp lights up, and the supervisor sees at once where the line has stumbled.

Andon is electronics that measures the factory and shows its state. The lamps above our machines and the idle meter are its direct descendants: they too answer the question «where is the factory standing right now».

12345the andon board above the linestation 1station 2station 3station 4station 5cordthe worker at station 3 pulled the cord — lamp 3 lights: the foreman sees at once where the line stumbled
Andon at a Toyota plant: one lamp per station. Electronics that shows the state of the shop — the ancestor of our lamps and idle meter.

Goldratt's five steps

Later, in the books after «The Goal», Goldratt summed everything up in five steps that repeat in a circle:

  1. Identify the constraint — the section that sets the output of the whole factory.
  2. Exploit it fully — so that it never stands idle for a minute.
  3. Subordinate everything else to it — work at its rhythm, not your own.
  4. Elevate the constraint — speed it up, add capacity to it.
  5. Repeat — the constraint has moved elsewhere; find it again.
1. identifyidle meter2. exploitHerbie never waits3. subordinateHerbie’s rhythm4. elevatespeed Herbie up5. repeata new placeround and round: the constraint has moved — find it again
Goldratt’s five focusing steps. Highlighted — the steps for which this kit builds electronics.

The lessons of this kit follow these steps. The idle meter identifies Herbie. The rhythm selector subordinates the release to him. The speed-up experiment shows that only he should be elevated — and that after that the constraint moves.