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IN CLASSIC JAPAN, automata known as karakuri delivered tea to guests. The mechanized doll would approach the guest, then, with head bowed, offer the cup of tea. When the tea was consumed and cup replaced, the karakuri would raise her head, turn around, and return to her starting point.
In the 17th to 19th century, this was quite an impressive trick. Indeed, karakuri, からくり, is the Japanese word for “tricky mechanism.”
Karakuri Today. The word karakuri has entered Japanese, and American, manufacturing jargon describing engineering solutions of notable elegance. As described by Hans Greimel in Automotive News, December 31, 2018, its precepts are straightforward: 1. A karakuri concept uses gravity and simple mechanisms such as springs, cams, or gears. 2. Its materials are low-cost and consume little or no power. 3. Karakuri relieves overwork, waste, or uneven workflow. 4. It improves safety, quality, productivity, maintenance, or logistics.
Easy-Access Trays. On the Mazda Hiroshima trim line, workers within the cars are delivered trays containing the tools and parts needed for their tasks. These trays moving in and out of the cars are articulated by levers and cogs, the power coming from gravity: Plastic bottles, originally containing soft drinks, are weighted appropriately with old nuts and bolts, just enough to balance the movement. Once the trim work is completed, the worker resets an arm, the tray moves out of the interior through its weighted-bottle power.
Mazda says this karakuri saves $6400 per year. Its cost is $424 in materials, plus 40 hours of labor.
A Spring-Powered Cart. In his Automotive News report, Hans Greimel writes about Toyota’s Tundra assembly in San Antonio: “Every time a Tundra came through their station, it would pull a cart of parts and tools with it. The problem was, after the vehicle moved to the next process, workers had to wrestle the 72-lb. cart back to the starting point 25 ft. up the line. And they had to do that no fewer than 1040 times a day.”
The karakuri fix was simple and ingenious: a spring-loaded line attached to the cart. Greimel writes, “It spools out as the cart and vehicle move down the line together. When the cart gets to the end of the process, it trips a switch, and the coil reels the cart back like a retractable keychain.”
“The extra cost,” Greimel says, “was peanuts, but the savings in time and wear and tear were substantial.”
Mixed Nuts, Please. On Mazda’s Hiroshima trim line, workers had to count out the correct number of fasteners, and possibly drop several, for whatever task was being performed. Now, a karakuri dispenser is adjusted to deliver just the right number of fasteners into the worker’s open palm. The system resets after each handful.
Another karakuri device separates links of CVT drive belts during their drying in a cleaning process. This saves 40 minutes per engine, with concomitant savings in electricity, thereby reducing power expenses and 0.28 tons per year of carbon emissions.
As another example, Toyota emission analyses in prototype development were streamlined by a simple fixture that reduced a task taking as much as four hours into one of 10 seconds.
A Tea Break Too? Its developer invented 20 karakuri concepts during five years at Toyota, the best of them getting him an $800 bonus. And, I’d like to imagine, he got a nice cup of tea, delivered by a traditional karakuri doll. ds
© Dennis Simanaitis, SimanaitisSays.com, 2019