The Suzuka Factory was Honda’s third domestic plant, established in 1960. It is now one of Honda’s most important production bases, used to manufacture the CR-Z, Insight, Fit, N BOX and other top Honda models. A new technology was born last year at the Suzuka Factory’s Engine Plant No. 2 Casting Module.
The development was led by Staff Engineer NagafumiMuta and two other staff members. Muta says “On a day-today basis our section is responsible for the production of cylinder heads, which are the part on the very top of the engine. We make the cylinder heads using the Low Pressure Die Cast (LPDC¹) method that heats aluminum to about 700 ℃, has the molten metal flow into a die and finally cools it to solidify.”
The LPDC manufacturing method pours molten aluminum into a die, and if the die is cold the flowing aluminum may cool and harden, preventing the formation of the correct shape. So the dies must be heated sufficiently beforehand. “Because of this characteristic of the LPCD method, one process was required during the factory lunch break. While we turned off the manufacturing equipment during lunch, allowing the dies to cool would hinder the afternoon works. So all through lunch we had to heat the dies with gas burners to maintain their temperature.”
Continuously heating the dies with gas burners even while production is stopped might be accepted as inevitable, but in another sense this is a waste of energy. Yet, as illustrated by Staff Engineer Kenichi Maeyama’s explanation: “As far as I know, Honda has used this method at all its factories for the past 40 years,” heating dies with gas burners during lunch breaks was the conventional approach for the use of the LPDC method.
※ Low Pressure Die Casting (LPDC)Metal casting methods include gravity die casting (GDC), low pressure die casting (LPDC) and high pressure die casting (HPDC), with different methods used for different purposes and applications. Among these, with low pressure die casting (LPDC), the molten metal is injected at a slow speed, so the casting quality is greatly influenced by the die temperature. For that reason, the die must be maintained at an appropriate temperature, as noted in the text.
Nevertheless, workers at the No. 2 Casting Module began to question this long-standing method, and came up with an idea to change it. This was sparked by the spread of efforts to change the way work is done throughout the Suzuka Factory to advance energy savings and CO₂ emissions reductions.
When the works at the No. 2 Casting Module were reviewed as part of this initiative, Staff Engineer Jyunji Sugimoto noticed something.
“When I carefully examined the gas burner preheating during lunch breaks, several problems become clear. The temperature rise was uneven, with higher temperatures on the surface, and there was a great deal of heat dissipation, with poor efficiency. In short, in terms of the ideal energy efficiency, the gas burner method was far from perfect. I wondered if there wasn’t some way to efficiently heat only the necessary areas, only as much as needed. Then I came on the idea of using electric heaters, instead of gas burners, to heat the dies.”
Because electric heaters do not use flames, when electricity is used the dies can be sealed with insulation. Also internal heating coils can be inserted, greatly improving efficiency. According to Muta, the electric heaters have other merits as well.
“When gas burners are lit while associates leave for lunch, the burners have to be monitored by safety supervisors due to the fire danger. With electric heaters, the danger is very small so the dies do not have to be monitored. In other words, the electric heaters have great merits in terms of safety and personnel costs as well.”
The interesting thing is that engineers Muta, Maeyama and Sugimoto came up with this idea while chatting in the associate lounge.
“Even when we wrack our brains trying to come up with ideas in a formal setting as part of our work, they do not emerge that easily. But there we were joking during lunch break and this idea popped out, just like that.”, said Maeyama.
“Yes, ideas are more often created in a relaxed setting,” said Sugimoto.
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