Karakuri is written in Japanese most commonly as からくり. It basically means gimmick, mechanism, machinery, trick, contrivance or device. The key point here is some mechanical trickery.
It originated with mechanical dolls in Japan, called Karakuri Ningyo (からくり人形). These dolls are first mentioned around 1500 years ago, but were most popular around 200 years ago. These dolls can be seen as the precursor to robots. One of the most well-known examples is the tea-carrying doll displayed at the top of the article. The weight of a bowl of tea put on the tray made the doll move forward a set distance while moving its feet (powered by a wound-up spring). After you remove the bowl and drink the tea, the empty bowl is placed on the tray again. This weight then made the doll turn around and move back to its original position.
Karakuri in industry
Toyota introduced the karakuri philosphy as part of the Toyota Production System (TPS). Carts, racks, roller conveyors, etc. with which material is handled on the basis of gravity, levers, cams and inertia. This to move boxes and parts between machines or deliver a controlled number of small parts to the hands of an operator. Karakuri allows Toyota and in the meanwhile several other companies to involve the operators even more in the kaizen activities and to let them implement cheap automation projects.
Why use Karakuri instead of computers?
Industry 4.0 is currently all the rage. Yet, karakuri kaizen with its focus on mechanical solutions is pretty much the opposite! These solutions are not connected wirelessly, and not online as part of the internet of things They don’t even have a microchip! So why use them? After all, any of these actions can also be done using sensors , actuators, and processors. Yet, karakuri is often better with following advantages:
In a purely mechanical system you do not need the wiring and programming. It gives Karakuri the potential to be cheaper than a computerized system.
Easier to Maintain
Often, maintenance of karakuri is also easier. If a computer system bugs out, it is really hard to figure out what went wrong. You need a mechanic, an electrician, and possibly also a programmer. With a mechanical device, it is usually quite easy to see (even for the untrained eye) where the problem is. Hence, finding and fixing the problem is potentially much easier and may even be done by shop-floor personnel. However, no worker on the shop floor will touch a computer system to fix it, because it is so much harder to fix.
Easier to Improve
Karakuri is most often called karakuri kaizen. And kaizen is continuous improvement. Such improvement often requires trial and error, and usually requires the input from the workers. Similar to the easier maintenance above, shop-floor workers can create and improve karakuri devices by themselves, whereas they will not install or change anything that includes computers and sensors. Hence, karakuri devices allow for a bottom-up continuous improvement in lots of little steps. Computer systems are big steps, usually initiated by management when they notice the problem (often too late, and only the biggest ones), and implemented by engineers and programmers when they have the time (rarely). In sum: Kaizen is so much easier with karakuri!
Some of our realizations can be found here.