Feb 7 2012
Takt times and falling sales: How to Respond?
Question from Jean-Baptiste Bouthillon on The Lean Edge:
We have all learned that overproduction is muda, and that production must follow the takt of customer demand.
Is there a lean way of dealing with falling sales ? Should we just adjust production to customer takt time or stabilize sales by giving rebates ?
Is it important to level sales and give some stability to production or should we just adjust the production takt time ?
My response:
You question implies that takt time is only a function of customer demand. It is not. When you calculate it, you divide your production time by the demand, which means that it is as much a function of how long you decide to work as of how much you have to produce. Without any change in customer demand, you double the takt time by working two shifts instead of one.
The takt time of a production line is the time that elapses between two consecutive unit completions when the line runs. It is not the rate at which customer orders arrive.
So how do you respond to falling sales?
You have to distinguish between fluctuations in sales, for which you should not change the pace of production, and major changes, for which you should.
Once you have set up a large assembly line to work at a takt time of 57 seconds, changing it to 60 seconds is a major effort, involving the balancing of tasks among stations and adjustments in part supplies. In car assembly, unless you are hit by something like the Fukushima earthquake, you don’t do it more than once in four months, even if you are Toyota. During this period, you use heijunka to respond to fluctuations in mix, and adjust overtime for fluctuations in total volume.
If you have a major downturn, you have to reduce production, and the challenge then is to do it without going bankrupt while retaining the work force you spent so much time and effort developing.
It is in such times that having your money tied up in inventory can bankrupt you. When the recession hit in 2008, management in manufacturing companies suddenly took an interest in working capital, but it was too late. Downturns come brutally, and it is when they occur that you must be ready.
Keeping your work force intact and prepared for the next upturn is just as essential. So you stop using temps, cut all overtime, go on four-day weeks, or three-day weeks, and use the available time to solve nagging engineering problems, experiment with new technology, etc. I remember an auto parts plant in Japan, in which recession time had been used by a team to build in-house a pick-to-light system with their own AGV out of Creform. Even though they did not explain it, you could tell that they would know exactly what to require from vendors and how to deploy this technology when the upturn came.
Nov 2 2012
Takt time: where this strange expression comes from
In the TPS Only discussion group on LinkedIn, Casey Ng posted the following:
To which Bertrand Chauveau added:
And Frederick Stimson Harriman:
Following are the results of my own research into the matter:
Takt is indeeed a German word, designating a bar on sheet music, but also an engine stroke as in Viertaktmotor (four-stroke engine), and the interval between trains on a line where they run regularly (picture by David J. Anderson), as shown below:
Lean implementers in Germany today, however, are just as confused about it as Americans, and I have heard some refer to Takt as the process time.
But how exactly did “Takt” migrate from Germany to Japan? I think the key reason the Japanese consultants Frederick worked with didn’t dwell on it is that it happened during World War II, and that Japan’s war time alliance with Nazi Germany is not a source of pride.
Digging further on the input from Casey and Bertrand, I found in Americanization and Its Limits a chapter by Katsuo Wada and Takao Shiba reporting that the military aircraft arm of Mitsubishi learned about the German “Takt system” from Junkers engineers in 1942, and had implemented it in the Nagoya works in fuselage assembly by 1943, under the name of zenshinshiki (前進式?). From a contemporary observer’s description, it looks very much like the pulse line system currently used for military aircraft at Boeing, with fuselage sections assembled at fixed stations and moved at a fixed interval — the Takt — to the next station.
This is to be contrasted with the moving assembly line concept used for aircraft also in World War II by Ford in Willow Run, MI, for the B24, and currently by Boeing for commercial aircraft. And it is not the same concept as takt-driven production today. But there are also accounts in German Aircraft of the Second World War of the German aircraft industry using moving lines for subassemblies during the war.
The Nagoya location of this Mitsubishi plant may not be coincidental to the transfer of the term to Toyota, which is still headquartered in that area. It may have been carried in the heads of unemployed military aircraft engineers joining Toyota after the war.
For the German part of the story, in German Aircraft of the Second World War, J.R. Smith and A.L. Kay, in their discussion of the Ju-88, explain “In August 1938, Ernst Udet laid down the Takt system of construction for all large state-owned firms such as Junkers and Arado…”
A Ju-88 flying in 1936
I also found the following picture of a Ju-88 assembly line in 1941, which suggests that the fuselages move sideways between operations rather than nose-to-tail:
Ju-88 Assembly Line in 1941
This is where the trail ends for now. Udet committed suicide in 1941, and was therefore not involved in the transfer to Mitsubishi. I have yet to find a detailed description of the Junkers “Taktsystem.”
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By Michel Baudin • History • 7 • Tags: Takt, Takt time