The body of the new N BOX mini-vehicle, which Honda launched on the market in December 2011, incorporates a reinforcement component (an ultra high-rigid stiffener) produced using the hot stamping process. In the past, this production process made adoption in mini-vehicles difficult due to cost and other problems. Honda Engineering Co., Ltd. which serves as Honda’s manufacturing technology division, successfully reduced hot stamping costs using technologies developed in-house. A decision was made to adopt these technologies in the N Box.
What sort of technology is the hot stamping process?For an explanation, we approached Staff Engineer Kazuya Saito, the project leader for the new process development project.
“Hot stamping refers to the process of press-moding steel sheets heated to be malleable at 840 ℃ or more, and the subsequent cooling. It makes the steel five times stronger than normal. This process resolves competing challenges: strong materials are difficult to mold, but easily-molded materials lack strength.”
Yet hot stamping also has demerits. Vast amounts of energy are needed to heat the steel sheets, and unnecessary portions must be trimmed off using lasers after molding.
So hot stamping requires a lot of time and effort, and has high costs. The Honda Engineering project team developed the world’s first internal die trimming manufacturing method, which trims the unnecessary portions without using lasers, which were a major cause of the high costs,and even drills holes.
Two young engineers, Toshifumi Matsuda and Kohei Tejima,played central roles in the development of this internal die trimming method.
Matsuda says “I was conducting research on technologies to make aluminum lighter six years ago, but at that time the company’s policy was shifting to an emphasis on making steel lighter.”
In this context, Matsuda decided to focus on the stamping process.
“I suggested that if we were going to use steel, we should investigate hot stamping. I knew that the many processes, long cooling time and laser processing resulted in high costs, and realized that if we could resolve those issues it could become a low-cost and wide spread technology.”
The company’s reply to Matsuda was that he should go ahead and pursue this. At that time he had only been at Honda Engineering Co. for five years and had no subordinates. He decided to involve Tejima, who had just entered the company.
“Mr. Matsuda asked me to join his team, but at first we knew nothing about dies. While addressing all kinds of concerns we advanced our research a bit at a time”, Tejima says.
A key point of the internal die trimming process that trims and drills holes inside the die is the use of a high speed hydraulic system for the dies to work. Several hydraulic equipment manufacturers refused to participate, insisting that such a use would create a very great load and be too dangerous. Tejima tried persistently to find a manufacturer that would cooperate, leading to the development of the present hydraulic system.
“I think many people viewed this as very risky, but Honda continued to be supportive, and did not tell us to stop.”
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