This was a very impressive exhibit, and I learned a lot about karakuri from the many different examples shown there by over one hundred exhibitors. Organized annually by the Japan Institute of Plant Maintenance, it is to my knowledge the biggest showcase of karakuri in the world. This was an exciting visit that I will process in a whole series of blog posts on karakuri Fundamentals and Examples Karakuri is the use of mechanic gadgetry rather than electric, pneumatic, or hydraulic devices. Definitely no computers!
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Here is my attempt of a structured overview, even though some of the points below may be overlapping. Improve Material Transport There are a number of different uses for karakuri. In the West, it is most commonly associated with material transport, especially returning empty boxes in a rolling lane supermarket.
There an AGV moved material around. The material was stored on rolling lanes on the AGV. Simply by driving slowly past the supermarket, different levers activated the material transport, and boxes with material moved from the AGV into the supermarket, while empty boxes moved back to the AGV.
A rough sketch of the process is shown below. The AGV then returned to the supply supermarket, slowly driving along. Again, levers returned empty boxes to the supply supermarket, and other levers restocked the AGV with full boxes from the supply supermarket to be brought to the consumption area. The video showed different examples, including engine blocks with kits. Well-thought-out kinematics made sure no boxes dropped on the ground or tried to move into an already occupied spot.
Since I wrote the post, Johannes Schuch showed me some good videos in his comment below. For example, on automotive assembly lines, operators often have a small cart with material and tools. These carts can be pushed along by hand, but it would be much easier if they move along the line by automatically.
While this idea is not new, Toyota Motor Canada presented such a cart in a karakuri version for the mounting of the engine in the car. While moving forward, a weight is lifted. After one car is done, the weight is released and moves the cart back along the line to the next vehicle. They also incorporated a protective mechanism that covers the fender of the car while working and presents a tray with parts over the fender of the car within easier reach of the worker. Altogether they were able to eliminate eight steps per work cycle.
Another example helped with installing exhaust systems underneath cars. The device presented a new exhaust to the worker within easy reach, reducing both walking and lifting effort. This reduced the cycle time of the worker by four seconds, or roughly 7 percent overall, as well as eased the burden of the worker. Thee plastic hoses were stuck in a connector. To remove them, the worker had to push a quick-release ring while pulling at the hose at the same time.
This happened in a cramped spot inside a larger machine, and the worker had to twist his fingers quite a bit to achieve that. Additionally, the small hose made it difficult to push the ring while pulling the hose.
After a few times, the fingers of the workers started to hurt believe me, I tried it. To resolve this problem, the company created a special pair of pliers that fit into the tight spot. Simply by closing the pliers, a mechanism pushed onto the release ring while at the same time pulled the hose out.
This special tool made it much easier and more comfortable to remove the hose, not to mention much faster. Another example by Toyota Boshoshoku was during visual inspection of car bumpers. These bumpers were originally on a rotating rack. Before, this meant that the worker had to walk back and forth to be close to the bumper for inspection. This is shown below in a top down view on the left side. The new karakuri device had a pin in a peanut shaped slot.
As a result, the worker was always close to the bumper without moving back and forth. Many more examples helped with lifting heavy loads or raising parts so that the operator can take them without bending over. Others helped to get parts into tight spots. Orientation of Materials Quite a few of the karakuri exhibits on display were used to arrange small parts for easier use by either machines or humans. The first example here is probably well known, being a popular example from Toyota.
During assembly, the worker needs to screw in two screws. Before, the worker had to pick them manually out of a box, which is cumbersome. Toyota attached two magnets to an movable arm.
Whenever the worker returned the power drill to the power drill holder, the weight of the power drill pushed down the arm briefly. The magnets dipped into the box of screws and picked up just the right number of screws in this example, two. This little unpowered mechanism saved the worker quite some time fumbling for the right number of screws. Another example is for feeding a machine with oriented parts.
The mechanism is so simple that you could argue that it is no mechanism at all, since it has no moving parts. The goal was to orient bolts where both ends were of a similar diameter, with one side only slightly larger than the other one. Instead of using a complicated bowl feeder, they simply used a half-funnel-shaped metal slide. Since the larger diameter side of the bolt rolled faster, this end always came out first at the end of the funnel.
There were many more examples of bringing material in a good orientation for further use. In fact, this seems to have been one of the major uses at the karakuri exhibit. Reduces Cost Another advantage of a karakuri mechanism is that it can reduce the overall cost. A conventional machine with computers, sensors, and actuators can be rather expensive. Depending on the situation, a karakuri machine can be much cheaper. Toyota Boshoku built a karakuri parts feeder that oriented the parts.
They used a pendulum that stored power and allowed the mechanism to operate for a few seconds without additional power. Improves Quality Denso showed an exhibit where they improved product quality. They transported a tray with around one hundred small and very delicate parts using an AGV.
This was enough to create an occasional issue for the parts, which got bumped too. As a result, even when the AGV ran over uneven surfaces, the parts did not shake.
Not only did the quality of the parts improve afterward, but the AGV was also able to drive faster, reducing one minute of the turnaround time for the transport. Another device by Toyota Motor Japan was a system that cleaned the rollers of a rolling lane automatically. This eliminated metal chips that sometimes scratched the parts. Another device by Daihatsu helped with inspection of valve seats, where an endoscope-style camera had to be inserted into around fifteen holes of a device.
The karakuri gadget made sure no valve seat was forgotten, and also eased the use of inspection. Improves Safety Not many but a few of the exhibits improved safety. Toyota Motor Japan displayed a device that was incorporated in a winch hoisting forty-kilo items.
They worried what would happen if the chain lifting the weight broke or otherwise failed. Hence they included a safety stop that actuates when the chain snaps. By itself nothing new similar devices are long since standard in elevators , but in this application it was for a much smaller device. Another example by Aisin Seiki provided pallet storage with a gate.
The weight of the pallet closes the gate when the forklift puts the pallet down. If the forklift lifts the pallet up again, the gate will swing open. Side note: Their video of the warehouse had only one such gated pallet storage, and upon my inquiry they commented that it may be a bit expensive. I guess this is not yet widely in use. Visual Management The fan is ON! Karakuri can also be used for visual management. Any type of gadget that visualizes the state of a device can help here. In its simplest case, this would be strips of plastic on a fan or air conditioner.
Other examples were a ball in a plastic tube to monitor flow, red and green coloring on dolly wheel locks, or a red sign that pops up when a valve is opened.
Wow, that blog post took me much longer to write than expected. In any case, I am confident that there was something in here that inspired you. But inspiration alone is not enough. Let the actions follow. Series Overview.
Introduction to Karakuri Kaizen
Karakuri Kaizen Examples