Injection molding systems and methods for forming materials used in footwear and materials manufactured by said systems and methods

A method of forming a foamed part, the method comprising:

• providing a polymer processing system comprising a polymer processing space;
• mixing polymeric material and a blowing agent within the polymer processing space to produce an unfoamed mixture;
• providing a mold having at least one expandable mold cavity in fluid communication with the polymer processing space;
• injecting a volume of the unfoamed mixture of polymeric material and blowing agent from the polymer processing space and into the expandable mold cavity;
• expanding the expandable mold cavity to form a foamed preform part;
• inserting the foamed preform part into a press mold comprising a press mold cavity portion and a press mold wall portion, wherein the press mold cavity portion comprises a lower interior surface and at least one interior side wall surface, and wherein the at least one interior side wall surface comprises at least one recess;
• and
• press-forming the foamed preform part within the press mold to form a unitary finished part, wherein the unitary finished part comprises at least one side wall comprising at least one extension conforming in shape to the at least one recess of the interior side wall surface of the press mold cavity portion.