Inside Mazda

The Deep World of Metal Forging: Using a rare method to craft engine parts

We took a tour of the forging factory of Mazda’s Hiroshima plant with Hisashi Watanabe, a.k.a. “Mr. Forging.” Watanabe has spent 35 years working in the forging plant and was ready to show us the deep world of forging.

Making Iron Move

To see what metal forging looks like, check out this video from Mazda Japan’s blog:

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“I’ve worked in the forging factory for 35 years, but I am still fascinated and get glued to the sight,” says Watanabe.

Many parts for a vehicle’s engine and transmission are forged, as they need the strength only the forging process can give them. Mazda uses three types of forging for different parts: Electric Upsetter, Press Forging and Cross-Roll Forging.

The Rare Art of Cross-Roll Forging

Cross-roll forging is the rarest and most complicated type of forging, even in Japan.  Mazda uses cross-roll machines to forge countershafts, a transmission part. See it in action here:

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Using the cross-roll forging technique, an iron bar, heated to about 2,300 degrees Fahrenheit, is sandwiched by dies, each of which travels up and down separately, rotating the iron bar to mold its shape.

Cross-roll forging equipment has many advantages, including its high productivity and material yield, relatively quiet noise production and its compact size. But are only a few units of cross-roll forging equipment exist in Japan because adjusting the dies used are very  difficult.

What makes cross-roll forging so complex is that you don’t have any idea what final shape the dies will churn out, even if you watch them closely. However, Watanabe is an exception. He is capable of predicting and picturing the product’s shape in his head just by looking at the dies.

“When a defective product is found, you can instantly identify which die is the root cause if you can picture the image of the product shape based on the shape of dies,” Watanabe says. “Of course, you have to remember the roles of all 400 small pieces of die by heart, as well as understand how those pieces are related to each other. I used to spend many hours trying to figure out what piece was responsible for a problem using measurement tools and jigs. There were times when I could not get a clue even after working for several days.”

Watanabe was able to perfect his skills by spending years studying the characteristic features of cross-roll forging and from coaching by senior colleagues on how to repair dies. Watanabe continues, “Spending years with cross-roll forging, I can now draw a mental image in my head as to which piece of die has a problem, just by touching the die. It took me 20 years to get this skill.”

Passing Skills to the Next Generation

Watanabe has had  a lot of repeated trials and errors in learning cross-forging, and he feels it is his turn to pass down to younger generations the skills and techniques obtained by training himself over 20 years. “My job is to pave the way so the next generation can master my techniques in 10 years and the next next ones in three years, although it took 20 years for me to master them,” Watanabe says.

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