Introduction

In the kit «The Bottleneck» we found Herbie with an instrument and subordinated the release to him: the SLOW switch releases a part every 2 seconds, exactly at his rhythm. But for that you have to know in advance how long Herbie works. And a real bottleneck works unevenly: now faster, now slower, and after an improvement — at a different rhythm altogether. A timetable set in advance cannot keep up with it.

Goldratt proposed another way — «drum — buffer — rope». The bottleneck beats the rhythm like a drum. A small stock of work is kept in front of it — the buffer. And the rope ties the buffer to the start of the line: release a new part only when the stock before the bottleneck is running low.

In this kit you build that rope out of chips:

  • lesson 1 — the buffer counter: an IR pair after Herbie, two CD4029 counting down and two CD4008 adders. A display shows how many parts are waiting for Herbie;
  • lesson 2 — the rope: four goal switches, two CD4585 comparators and three free gates of FL-01 and FL-02;
  • lesson 3 — Herbie with a die: how much stock a bottleneck that works unevenly needs;
  • lesson 4 — the experiment «push or pull»: release every second, a timetable and the rope — and what happens when Herbie is sped up.

The electronics is the main thing here: a counter, an adder and a comparator turn the factory into a system with feedback — it fits itself to its bottleneck. Goldratt explains why that is needed.

What you need

The built kits FL-01 «The Dice Game» and FL-02 «The Bottleneck» — this kit is built on top of them: the same factory, the same panel, Herbie, the idle meter and the SLOW switch. If you don't have them yet, build them from the FL-01 and FL-02 books.

Chips — the kit file drum-chips.json, imported into the library with one button. It holds everything from FL-02 plus two more real Texas Instruments chips of the CMOS 4000 series: the CD4008 (4-bit adder) and the CD4585 (comparing two numbers).

How long

Four lessons. Lessons 1 and 2 are one Cmd+I insert each, lessons 3 and 4 are experiments of three or four shifts.