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.