Sheet Metal and Socialites: Episode 04 « Nipponscape – One hundred views of making and doing in Japan

Sheet Metal and Socialites: Episode 04

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What is Precision-crafted Sheet Metal?

Currently, at the start of the 21st century, the society we live in is virtually flooded with metal products. Additionally, these metal products require an extremely high level of precision. This is where precision-crafted sheet metal comes in. Picture the machines we use every day: bank ATMs, automated train station gates, vending machines. Those machines all fall into the world of “precision” machines. It doesn’t take an engineer to realize that. Precision-crafted sheet metal has no strict definition. It’s simply sheet metal that has been processed in an extremely precise way.

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Sheet Metal Processing

Sheet metal processing is a relatively well-known trade. The most common application of this is in the automobile industry. These workshops are everywhere, so most people have probably seen one before. Cars that have been dented up from collisions and other accidents are repaired at these sheet metal workshops. The work of a sheet metal worker is to cut and bend, weld and perforate sheets of metal to create the shape necessary for the job at hand.

In recent years, the skills of the sheet metal worker have been in the news because of their role in building the nose of the shinkansen bullet trains. There are only two noses per train, so the production volume is tiny. Additionally, the shinkansen models are upgraded frequently. As a result, it’s simply not practical to make a mass-production stamp press for the part. This is where the experienced hand of the sheet metal worker comes in. An aluminum sheet is formed into a beautiful curved shape through the repeated blows from a hammer. That kind of work is where sheet metal processing techniques really shine.

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Structural Components for High-speed Vehicles

Mr. Sugano operates on the same technical basis as sheet metal processing. The difference is the level of precision: his is one that won’t forgive a margin of even 0.1mm. The majority of the products that Mr. Sugano’s company Keiswi makes are components for shinkansen trains and airplanes. However, they’re not the vehicle housing, but rather the internal structural components. For example, parts with names like “center console, ” “center arm,” and “side arm.”

Both shinkansen trains and airplanes are high-speed vehicles. Naturally the parts that compose such a fast moving machine need to be precisely formed and assembled. In other words, a high degree of precision is required. Whether the space the machine moves through is on land or in the air, a vehicle moving at such a high speed is subjected to strong vibrations. If a high degree of accuracy and strength are not in place, even in something like the structural components of a seat which has no direct relationship to the chassis, the whole thing could easily collapse. This is why a high degree of skill is required to make these sheet metal components. It’s something that’s difficult to convey to people outside the industry. In order to better imagine what is involved, let’s take a look at the process broken down into steps.

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The Precision Sheet Metal Process

First, the most important thing of all is to take the three-dimensional image and break it into flat parts in a blueprint. The most difficult part is devising a plan while considering the order in which to construct the piece. If this isn’t done properly, the whole plan falls apart. The final assembled piece won’t be precise at all: it’ll be a mismatched defect. That’s why the skilled craftsman has to plan everything down to the tiniest detail in his head and record it all in the blueprint.

Once the plans have been drawn up, the next step is to program a machine called a numerical controlled machine tool, which automatically cuts out and makes holes in the pieces in accordance with the programming. Here, the metal plate has holes punched out of it, and the unwanted burrs that are generated on the cut surface are removed. Not only do these burrs impede the precision of the work, but if they are not completely eliminated, the rough surface can act like a blade, cutting up anything it touches.

Once the metal parts are prepared, the next process is to bend the pieces. There is a special machine called a bending machine that is used for this step. The precise shape required must be decided in advance if it’s going to be done well, so this all must be planned out ahead of time in detail. If the metal sheets are not bent to the precise angle required, the entire project will amount to nothing.

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　Next is the welding process. Welding is the act of attaching two pieces of metal together through heating and melting the metal at the connection point. I’m sure many people are familiar with the scene of a neighborhood workman donning a welding mask, working hard amongst flying dust, sparks, and smoke. From an outsider’s point of view, the sight of a man generating flying sparks in the dim light of a workshop is an exciting, even beautiful, sight. However, the job is actually an extremely dangerous one, which requires a very high level of skill to execute properly. After the various metal parts have been welded together, the final step is finishing, where the lumps and scratches created during the previous steps are smoothed to a beautiful flat surface, and the product is completed.

Put into words, the manufacturing procedures involved may sound simple, but it goes without saying that they are in fact terribly difficult. There’s absolutely no room for cutting corners. The material itself is subjected to heat and pressure during the manufacturing process. Due to this, the metal undergoes slight expansion and contraction. A seasoned craftsman has to be able to identify the nature of his materials by sight and adjust the pressure and heat while he works. Precision sheet metal processing requires thorough planning based on accumulated experiences, and the skilled hand of a seasoned craftsman.

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Perhaps Mr. Sugano’s workshop Keiswi has this level of skill because it has been a sheet metal shop for three generations. If the many techniques cultivated by his grandfather had not been passed down, there might not have been such a highly-valued sheet metal shop left in the 21st century today.

Nippon Scape

Sheet Metal and Socialites: Episode 04

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