Making Manhole Covers

 Preparing Sand Molds

An aluminum template of a manhole cover featuring Yokohama’s famed Bay Bridge.

The plant has more than 4,000 manhole cover templates.

A sand mold for casting is created by pressing the aluminum template into a special sticky sand.

Preparing Materials

Around 70% of the material for cover is recycled scrap metal, often collected from local factories.

High-quality scrap metal is melted in an electric furnace.

Magnesium, sulfur, and other materials are added to create sturdy, durable ductile iron.

A worker removes impurities from the molten metal.

Adding Materials to the Molds

Specially ordered goods and large manhole covers are cast by hand. Here workers pour molten material into molds using manually operated machinery.

The speed and volume of material added to the mold affect the quality of the finished manhole cover.