I am curious about how metal molds for injection molding are made. Especially before CNC technology became common. And I mean the kind of molds we like - lots of detail with parts that have to fit together. Anyone know?
Most molds are made out of aluminum and are either casted or machined. For high volume injection molding, most are casted then machined. A representation of the part to be molded called a pattern is made from either wood, clay, or sand, and is put into a casting box and molten aluminum is poured into the box, and cooled, it is taken out, split, cleaned up, and all the fine details are machined into the mold.
Today, with the advent of 3D scanners, a multi-axis CNC mill can really make a good, crisp mold for plastic model injection molding. However, I think the majority of the molds are still made by hand by skilled pattern makers.
Scott