Nov 7 2012
See on Scoop.it – lean manufacturing
But problem solving is a problem at companies accustomed to hiding problems, according to Shook.Cambridge, MA (PRWEB) November 05, 2012 A company’s “attitude towards problems” determines if it succeeds or fails at a lean management transformation,…
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Nov 6 2012
In the TPS Only discussion group on LinkedIn, Joachim Knuf provided the following information, to which I have added a few illustrations:
“Junkers was building an aircraft for infantry support in 1917/18, the J4. After building airplanes in a handcraft mode for some years, this was the first attempt to meet larger demands. Junkers was known for not simply designing a product but the production process along with it. Clearly very lean and practiced by Toyota.”
The founder of the company was Hugo Junkers (pronounced ‘yoonkerz). He died in 1935 and was in no way affiliated with the Nazis, who took away his company and later besmirched his name by claiming association with it. Because the company still bore his name, it is linked in the minds of World War II forced laborers with their experience.
“The J4 was build in modules, incorporating components delivered from outside vendors, incorporating fixtures, templates and gauges for economic benefit. Subsequently, the F13, build in 1919/20 as the world’s first civilian passenger plane, was designed from the start with modular manufacturing in mind. This plane was built for customers around the world, with production numbers as high as 60/month.”
The only surviving J4, at the Canada Aviation and Space Museum.
Junkers F13 in 1925.
“Production was organized to an overall completion schedule. As a result, completion of modules had to be structured and synchronized. Final assembly was organized into six phases, performed at specific fixtures. Highly specialized work teams had a set amount of time to complete their fixture-based task, then moved on to the next fixture to repeat the job, followed by another specialized team (what we think of as a caravan system these days). The increment was the ‘progression interval’ (Fortschrittszeit). Airplanes/modules stayed in place. The result was a finished plane every 9 hours. This approach was shared with Junkers facilities working in other industries.
By 1926 this system was developed to the point that subassemblies could be produced off the main assembly and connected to it with moving lines that moved at set intervals. These intervals were then referred to as ‘Takte’ (plural, ‘takt intervals’). With the new W33/34 (first East-West Atlantic crossing in 1928), there was interest in the US to produce the plane in license, in preparation of which Junkers developed a complete production plan to allow large-scale production, identifying the most economical methods. At that point Junkers had 40% of the international market share. Some years later, Lufthansa orders for the new model Ju 52/3m required the further refinement of the ‘takt method’ (Taktverfahren), incorporating new technology and equipment.”
Junkers W34 at the Canada Aviation and Space Museum.
“After 1933 (and the nationalization of Junkers by the Nazis) this allowed the mass production of airplanes in serial assembly. To produce the required numbers of planes, eventually also using forced labor, Junkers began constructing large subassemblies in decentral locations within 20 miles of the main assembly facility, delivered just in time. Major subassemblies then moved down a ‘takt avenue’ (Taktstrasse) from station to station, remaining a uniform, prescribed ‘takt duration’ (Taktdauer) in each, creating the Junkers ‘Airplane High Volume Series Production to the Minute’ (Flugzeug-Grossreihenfertigung auf die Minute). Changes in takt were used to adjust production volume to demand. Continuous improvement was an integral aspect of this system (which also certified workers on their self-inspection skills).”
A 2010 video entitled Fischertechnik Taktstrasse mit Sortierung depicts a “Taktstrasse” as a transfer line.
Nov 2 2012
In the TPS Only discussion group on LinkedIn, Casey Ng posted the following:
“It is quite clear that Takt is a foreign word (外来語) to both English and Japanese.
Its origin could come from German : Taktzeit.
Refer to “Walking Through Lean History” by Jim Womack ( President and founder of Lean Enterprise Institute:‘By the late 1930s, the German aircraft industry had pioneered takt time as a way to synchronize aircraft final assembly in which airplane fuselages were moved ahead in unison throughout final assembly at a precise measure (takt) of time.’
Therefore, Toyota could have adopted the term and application from Mitsubishi who had technical link with the German in aircraft manufacturing.
But Toyota did breathe new life to the concept of takt by integrating it to the flow principle and inventory reduction of JIT. Therefore, any attempt to implement JIT without proper understanding of takt with Taiichi Ohno’s precise definition of takt time could fail.”
To which Bertrand Chauveau added:
“Takt is a German word
Casey, you are right. It is a German word used in music to describe the rhythm. Mitsubishi brought it back to Japan. Association of Japanese manufacturers deployed it throughout the industry. Thus Toyota adopted and adapted the concept to their production.”
And Frederick Stimson Harriman:
“Regarding the German origins of “takt,” I have never heard any of the Japanese consultants I worked with say where they thought the origin was, but a consultant from JIPM did say to me once that Shingo used the term, and so Bertrand’s explanation makes sense.”
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.”
Oct 31 2012
This is the question Casey Ng asked in the TPS Only discussion group on LinkedIn. He elaborated as follow:
What are the essential conditions to implement takt time successfully? What are the cases when it fails and if you refer to the fundamental principle of takt and yet couldn’t find the solution? Then what are the exception areas and what alternate solution can be used?
To date, it has generated 43 comments, many with the high level of depth and the implementation examples that are characteristic to this group. It is a new LinkedIn group, with only 118 members — compared with 151,503 for Lean Six Sigma — but passionate and providing meaty technical content. I recommend it in general, and this discussion in particular. Here, I will be including only my own contributions on takt time, and its relevance to the following:
With monuments — the very large machines used for heat treatment, electroplating, painting, cutting of sheet metal, etc. — you usually have to load multiple parts simultaneously in order to meet demand, but these parts often do not have to be identical. I don’t recall anyone mentioning this in the earlier comments, but the parts that you load together can be a matching set rather than a batch. If your takt times are long enough, as, for example, in aircraft production, you can actually process one plane-set at a time, to takt time.
Gigantic products, like oil tankers, with takt times of six months or more, are built out of vertical hull slices made at much shorter takt times in a shop, and then welded together in the dry dock. Pioneered in the US with Liberty Ships during World War II, this is now standard shipyard practice, and enhances of the repetitiveness of the process, applying the concepts of takt time and one-piece flow.
I am puzzled by Todd McCann‘s use of the takt time concept in the context of nuclear plant refueling outages, a problem I had the opportunity to work on 20 years ago in France, not in the US. I don’t know who the top performers are in this area today. At the time, it was a tie between the French and the Japanese, at about three weeks from shutdown to restart for one reactor, which is substantially longer than the 193 hours you were quoting for 2006, assuming that the work continues 24 hours/day, 7 days/week.
The French performance was accomplished by standardization. They had 55 reactors with only two designs, producing respectively 900MW and 1300MW, run by a single company. The procedures were the same everywhere, with any improvement quickly shared. The Japanese performance was based on using techniques from TPM. They had nine different reactor designs, run by different utility companies.
Even though they had the best performance in the world, I saw many opportunities for improvement, based on borrowing techniques from SMED, improved planning and scheduling for materials, tooling, and the 1000+ contractors involved, and operational details. Such a detail, for example, was security. Their procedures were effective at controlling access, but inefficient, with utility employees at all levels spending too much time getting contractors into and out of the facility.
The concept of takt, on the other hand, did not strike me as particularly relevant, given that a refueling outage is a yearly burst of intense activity for any given reactor, as opposed to a repetitive process.
More generally about takt time, most businesses have both what my colleague Crispin Vincenti-Brown called Rate Work and Response Work. In manufacturing, if you do a Runner-Repeater-Stranger analysis of your products, Your Runners and Repeaters are rate work; your Strangers, response work.
Runners are products with enough volume to warrant a dedicated line. Repeaters are products that you group into families that, in aggregate, have enough volume for a line. Strangers are all the other products, including R&D prototypes, sample quantities of new products, spare parts for obsolete products, and any other special request. Even in aggregate, they account neither for a high volume nor for high revenue, but you still must produce them promptly. They require a small job-shop set up with your most flexible equipment, staffed with your most versatile operators, and its own operating policies.
While takt time is fundamental to line design for Runners and Repeaters, it isn’t much use for Strangers.
I have a hard time seeing the relevance of takt time in the absence of repetitiveness. In an assembly process, the takt time gives you an upper bound for the process time at each operation. As you broaden the mix of products you assemble on the same line, it becomes more difficult to balance the work among stations. Past a certain point, you are better off using approaches like bucket brigades, a.k.a. bump-back system, or even a yatai, which are not based on takt time.
Outside of mathematics, concepts are not reducible to formulas. Time/Demand is the way you calculate takt time, but it tells you neither the rules by which you are supposed to use that number nor how it maps to shop floor activity.
In mass production plants, managers use the inverse of this ratio: Demand/Time, which gives you the same information. Mathematically, working at a takt time of 1 minute and making 60 units/hour (uph) is equivalent. Yet, you and I know that, depending on whether the manager thinks the plant is producing at a takt time of 1 minute or making 60 uph, the shop floor will be radically different.
If you think in terms of uph, it doesn’t matter if nothing comes out for the first 59 minutes of each hour as long as all 60 come out in the end. If you think in terms of takt, 1 unit will come out like clockwork every minute.
What this says is that there is more to takt time than the formula. This is discussed extensively in Lean Assembly, with the following definition of takt time:
“Assuming we complete the product one unit at a time at a constant rate during the net available work time, the takt time is the amount of time that must elapse between two consecutive unit completions in order to meet the demand.”
As I recall, this is,more formally, the way Ohno described the concept in Toyota Production System.
The takt time allows you to define an ideal state, that John Shook and Pascal Dennis call True North, but that I prefer to call takt-driven production. In this state, you perform all operations one-piece at a time with process times that exactly match the takt time, and with instant transfer to the next operation at every beat. Of course, it is never perfectly realized, even on an assembly line. Real lines can only be approximations of it. The point is that it gives us a direction.
All deviations from takt-driven production translate to Ohno’s waste categories, overproduction, waiting, excess inventory, etc. Since any local project that move production in this direction eliminates waste, it can be undertaken with the confidence that it contributes to global improvement and is not sub-optimization.
Joachim Knuf : “… The ancient Greeks differentiated between two types of time: chronos (chronological, sequence of intervals, typically of equal extension) and kairos, best thought of as ‘the opportune moment.’ In this case, intervals begin and end under sets of conditions. This concept applies, for example, to healthcare, when next process steps are initiated by a preset configuration of values (patient’s blood pressure, glycemic index, bowel movement), not by elapsed time…”
I had never heard of Kairos, but, if the ancient Greeks made the distinction between Kronos and Kairos, why shouldn’t we? There is a rich toolbox associated with the pursuit of takt-driven production. Where the concept of takt does not apply, we can’t use these tools. As you said, extending usage of the word to Kairos-driven activities just adds confusion. These activities need different tools, and Casey pointed out some of them in his comments on Strangers. Let us keep different words to hang them on.
Nov 8 2012
Superheros of Manufacturing | Karen Wilhelm
See on Scoop.it – lean manufacturing
See on www.manufacturingpulse.com
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By Michel Baudin • Blog clippings • 0 • Tags: Lean manufacturing, Maintenance, TPM