Toyota established its casting plant amid the farmland of Miyoshi City, Aichi, in 1973. This was the era of Japan’s rapid motorization, even as pollution became a pressing social issue.

At Toyota Motor, the production of cast parts began with the Honsha Plant, which opened its doors in 1938. However, as demand for automobiles soared in the second half of the 1960s, securing a stable supply of such parts presented a major challenge for management. At the same time, the Honsha Plant’s foundry facilities were increasingly showing their age.

Casting involves pouring molten metal into molds made of sand, which are then broken apart to remove the finished product once it solidifies. Breaking molds and cleaning residue from parts tends to stir up fine sand and dust, and dealing with these particles is an inescapable task for foundries.

By 1970, industrial pollution had become a major issue in Japanese society, prompting sweeping changes to environmental regulations. As Toyota prepared to build a new casting plant, addressing pollution was a central priority.

In March 1971, Toyota acquired land from Aichi Prefecture in the town of Miyoshi; developed for industrial use, it would serve as the site for the company’s new casting facility. That May, a committee was established to steer the construction of the Myochi Plant. The following month, Toyota signed a pollution prevention agreement with the town, and broke ground with the aim of building a “pollution-free” factory. From the outset, Toyota’s seventh plant was built on a promise to the local community: a factory that would generate neither dust nor noise.

With the power supply system completed in February 1973, followed by the No. 1 casting plant in June, the Myochi Plant began operations. The plant’s design was centered around three principles: a good working environment, thorough pollution controls, and high productivity. Toyota’s mission for Myochi was to create an entirely new kind of casting plant, a trailblazing facility that anticipated the future to come. 

At the time, foundries typically featured sawtooth roofs with upper windows. Myochi broke with this convention, becoming Toyota’s first flat-roofed, windowless plant, designed to prevent dust from escaping into the surrounding environment.

Hisashi Hata, who joined the company in 1982, worked on maintaining and improving environmental equipment in the plant’s foundry and administration divisions, and later contributed to obtaining ISO certification as part of what is now the Plant & Environmental Engineering Division. He explains the Myochi Plant’s innovative approach.

Following the start of operations in 1973, Myochi expanded rapidly. The No. 2 casting plant was completed in 1977, adding capacity for cylinder blocks and smaller cast iron components. This expansion allowed the Honsha Plant's foundry to close in February of that year. In July 1981, the No. 3 casting plant began operations, boosting production capacity for aluminum cylinder heads.

In 1989, the groundbreaking ceremony was held for a new machining plant. Its first lines started up the following year, and the entire facility was completed by 1992. With machining and assembly lines for components including Celsior steering columns and axles for the Crown Majesta and Mark II, Myochi began to cement its place among Toyota’s leading unit plants.

Shigeru Murai joined Toyota in 1977 and later went on to head the plant’s Foundry Division. He recalls the Myochi Plant in its heyday.

One of the biggest turning points in Myochi’s history came in 1998, when the plant launched a three-year initiative to tackle dust at its source and create a “maskless” working environment.

The cylinder block manufacturing process includes a step known as “shot blasting,” in which small steel pellets are fired at freshly cast parts in order to remove any sand residue left by the mold. To keep the steel shot and sand from spreading, the equipment was enclosed in a sealed structure. As Murai and Koyanagi recall, however, this arrangement ironically created new problems.

“Enclosing the space meant that you couldn’t see inside. People worked surrounded by piles of sand, the equipment wore out, and we had frequent problems. It was very hard on the genba personnel.” (Murai)

“Inside, the enclosed space was really dirty. Piles of sand, spilled shot pellets scattered around. There was a pit that went about 6 meters into the ground, and even that was a mound of sand and shot pellets. It was like a desert.” (Koyanagi)

This space became a “back alley,” hidden from view and proper safety oversight, where managers would not even notice if guardrails had been removed.

After witnessing this situation for himself, Murai made the call: “Let’s get rid of the enclosure.” With that, the plant embarked on a new initiative based on the efforts of a genba-led quality control (QC) circle, seeking to go “maskless” by creating a work environment where even dust masks were no longer necessary.

The initiative was pursued as a three-year project, with the first year devoted to thorough cleaning by hand. Every member of the Foundry Division pitched in, getting covered in sand and sweat as they scrubbed even the normally no-go areas behind each piece of equipment. In the second year, they turned to tackling the actual sources of dust. Unable to secure an adequate budget for the project, frontline personnel came up with clever solutions.