Method for forming a footwear midsole

A system for forming a shoe comprising:

• a perforated last;
• a mold with a cavity shaped to receive a bottom region of the perforated last;
• and
• an injection machine configured to couple to an inlet port in the mold and to inject a polymeric material configured to foam and form a sole;
• wherein:
• the perforated last comprises:
• perforations arranged in clusters positioned in regions of the perforated last associated with regions of the sole which are thicker than other regions of the sole, the thicker regions comprising at least one of a heel region, an arch region, a ball region, and a toe region;
• and
• an inner conduit fluidly connected to the perforations and including an opening at a top of the perforated last;
• and
• the mold comprises:
• the inlet port through which the polymeric material can be injected into the cavity;
• continuous, gas-impermeable surfaces that do not include openings in addition to the inlet port;
• and
• a bottom piston that can be raised while gas is vented through the perforations in the perforated last wherein the continuous, gas-impermeable surfaces of the mold are configured to enclose the polymeric material between the bottom piston and the perforated last during the forming of the sole.