Section 5. Wartime Research and Production
Item 4. Research on Forge Processing Technology
Kiichiro Toyoda anticipated that as advances were made in casting technology, cast components would replace forged components. Therefore, when the Koromo Plant was constructed, investment in forging facilities was limited. Kiichiro explained his reasoning as follows:
I am ashamed to say that we are still using a primitive method. The workers are quite used to the processes, so even if the methods are primitive, the products themselves are fairly accurate... I had research conducted on forging machines and one-heat process forging in preparation for mass production, but the workers were rather unenthusiastic, and as a result the design of the Koromo Plant used the old style.1
The "primitive method" that Kiichiro refers to was hammer forging, which indicates production methods such as those using free hammer and stamping hammer with a forging die. The forging machinery installed at the Koromo Plant included not only hammer forging equipment, but also forging machines that perform die forging. The latter is a type of horizontal press known as an upsetter and is used to machine the ends of long materials to form rear axles and other components.
However, the workers were not accustomed to the upset forging machinery manufactured by Eumuco in Germany, and initially it was not used. Later, when it was learned that the dies for three processes could be arranged and three-step formation performed with a single heating, the workers recognized the efficiency of one heat forging and started using the upset forging equipment in 1940.2