HOMENunobiki Manufacturing’s RootsDeveloping Pyro Screens for Environmentally Friendly Machines

Developing Pyro Screens for Environmentally Friendly Machines

Pyro screen

Time moved on. In the mid-1970s when Japan’s rapid economic growth had begun to settle, various regions suffered from over-pollution, which became a social problem. As a result, factories needed to install air-purifying equipment to their stacks. Filters at the time were made from kraft paper or resin. But these materials had low durability and would burn when overheated. The president of Motozu Enterprises, which is still a customer, asked if we could make the filters out of stainless steel or aluminum, and we collaborated on developing a suitable product. The standard size of filters at the time was 500mm x 500mm, so it was imperative to comply with this standard. It was not just a matter of punching holes in a sheet between 0.15 and 0.2mm thick. High-temperature, dust-collecting filter pyro screens were developed using Nunobiki Manufacturing’s expanded metal technology to make diamond-shaped or tortoise-shaped mesh by cutting notches in a sheet and expanding them in opposite directions.

Despite having installed specialized machines to manufacture these revolutionary pyro screens, Nunobiki Manufacturing did not receive the anticipated number of orders.

A pyro screen’s inner filter

It was precisely around this time that the sales staff met a professor from the Himeji Institute of Technology at an exhibition at which Nunobiki Manufacturing had a display. Showing much interest in the pyro screens, he made it his project to research and analyze the screens’ wind direction and dust-collecting capabilities. Pyro screens at the time were pressed using the same machines that pressed diamond screens, so they were made between diamond screen orders. But thanks to the research results, Nunobiki Manufacturing had hard data that proved the capabilities of their pyro screens, and sales grew.


Nunobiki Manufacturing’s pyro screens were patented in Germany in 1985 and in Japan in June 1991.

In 1977, Nunobiki Manufacturing received an order from a pelagic fishery for perforated screens to fit machines that make minced fish from a fresh catch on a fishing trawler. Since the boats fish in the open ocean, the staff—together with other manufacturers that adjusted the machinery—needed to be waiting at the ports in Tobata, Kyushu, and Harumi, Tokyo, when the trawlers docked to measure, replace, and repair the screens. The new screens had to be delivered before the trawlers sailed, and Nunobiki Manufacturing is flexible enough to accept such short turnaround orders.

Since the products were delivered to a trawler, the smell of fresh fish was so overpowering the staff could still smell it two or three days later. They still remember that odor to this day.