Compression Vs Injection molded EVA Midsoles
Compression and injection molding happen to be just two of the many ways to produce midsoles. Although, as far as running shoes are concerned, these two methods (or a combination of) will account for over 95% of the models produced.
There are some models made from a poured Polyurethane method or 3D printing, but those are exceptions. We’ll briefly describe those processes too.
Compression molding, as the name suggests, is the process of compressing a block of EVA (Ethylene Vinyl Acetate) foam inside a metal mold. Much like a cupcake mold, the sides of these molds have a design etched into them.
When heat and pressure are applied to the mold, the material expands and fills the inside of the mold. Under pressure, the EVA foam takes on the shape of the mold cavity, including the design etched on its sides.
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