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

1. 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.

2. The method of claim 1 , further comprising cutting, buffing, or skiving at least a portion of the foamed preform part prior to inserting the foamed preform part into the press mold.

3. The method of claim 1 , wherein the polymeric material comprises thermoplastic polyurethane.

4. The method of claim 1 , wherein the press mold is heated to a temperature below the melt temperature of the foamed preform part.

5. The method of claim 4 , wherein the press mold is heated to a temperature of between about 155° C. to about 160° C.

6. The method of claim 1 , wherein press-forming the foamed preform part comprises a lateral displacement of the press mold wall portion with respect to the lower interior surface of the press mold cavity portion.

7. The method of claim 6 , wherein the lateral displacement comprises an asymmetric lateral displacement of the press mold wall portion with respect to the lower interior surface of the press mold cavity portion by rotation of the press mold wall portion with respect to the lower interior surface of the press mold cavity portion.

8. The method of claim 6 , wherein the lateral displacement is actuated through at least one of a mechanical, pneumatic, hydraulic, or electromagnetic actuation mechanism.

9. The method of claim 1 , wherein at least a portion of at least one of the press mold wall portion and the lower interior surface of the press mold cavity portion comprises at least one surface feature.

10. The method of claim 9 , wherein the at least one surface feature comprises at least one of a texture, a raised feature, and a recessed feature.

11. The method of claim 1 , wherein the expandable mold cavity is sized and shaped to form a foamed preform part that varies in thickness in at least one aspect.

12. The method of claim 1 , wherein at least a portion of at least one wall of the expandable mold cavity comprises at least one surface feature, wherein the surface feature is selected from the group consisting of a texture, a raised feature, and a recessed feature.

13. The method of claim 1 , further comprising:

inserting at least one second preform part into the press mold with the foamed preform part; and

press-forming the foamed preform part and second preform part within the press mold to form a multi-element unitary finished part.

14. The method of claim 13 , wherein the second preform part comprises at least one of a foamed element and an unfoamed element.

15. The method of claim 1 , wherein the unitary finished part comprises at least one of a midsole and an outsole for an article of footwear.

16. The method of claim 1 , wherein the unitary finished part comprises a sole element for incorporation into a midsole of an article of footwear.

17. The method of claim 1 , wherein the unitary finished part comprises a first region comprising a first density and a second region comprising a second density.

18. The method of claim 1 , wherein at least a portion of the at least one interior side wall surface of the press mold cavity portion further comprises a texture, and wherein press-forming the foamed preform part within the press mold produces at least one side wall of the unitary finished part comprising a texture conforming to the texture of the interior side wall surface of the press mold cavity portion.

19. 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 mixture of polymeric material and blowing agent from the polymer processing space and into the expandable mold cavity;

expanding the mold cavity to form a foamed preform part;

inserting the foamed preform part into a press mold cavity; and

press-forming the foamed preform part within the press mold cavity to form a unitary finished part, wherein press-forming the foamed preform part comprises a lateral displacement of a first wall portion of the press mold cavity with respect to a of the press mold cavity, and wherein the lateral displacement comprises an asymmetric lateral displacement of the first wall portion of the press mold cavity with respect to the second wall portion of the press mold cavity by rotation of the first wall portion with respect to the second wall portion.