Induction heating of golf ball mold for consistent durability and increased knit strength

1 . A method of forming a golf ball layer in an injection mold comprising an induction coil and a mold cavity defining a cavity surface, comprising:

positioning a golf ball subassembly in the mold cavity;

supplying an injection material to an injection port of a runner system disposed in the injection mold, wherein the injection material is at an injection temperature at the injection port;

activating the induction coil to heat the cavity surface to a target temperature which is less than the injection temperature;

forcing the injection material through the runner system to thereby begin to fill the mold cavity with the injection material from the runner system;

deactivating the induction coil while the mold cavity is filling with the injection material; and

allowing the injection material to harden.

2 . The method of claim 1 , wherein the target temperature is approximately the melting temperature of the injection material or approximately the glass transition temperature of the injection material.

3 . The method of claim 1 , wherein the injection temperature is between approximately 400° F. and 475° F.

4 . The method of claim 1 , wherein the target temperature is between approximately 100-175° F. less than the injection temperature.

5 . The method of claim 4 , wherein the target temperature is between approximately 120-140° F. less than the injection temperature.

6 . The method of claim 1 , wherein the induction coil is deactivated when the mold cavity is more than 50% filled.

7 . The method of claim 6 , wherein the induction coil is deactivated when the mold cavity is 55-75% filled.

8 . The method of claim 6 , wherein the induction coil is deactivated when the mold cavity is 75-95% filled.

9 . The method of claim 1 , further comprising extending a plurality of retractable pins into the mold cavity to securely position the golf ball subassembly.

10 . The method of claim 9 , wherein the retractable pins are hydraulically, pneumatically, or electrically actuated.

11 . The method of claim 9 , wherein filling the mold cavity comprises injecting the injection material into the mold cavity through an injection gate extending around a circumference of the mold cavity until the mold cavity is completely filled.

12 . The method of claim 11 , wherein the gate is a ring gate or an edge gate.

13 . The method of claim 11 , wherein the injection material comprises at least one of a polyurethane or ionomer material.

14 . The method of claim 1 , wherein the injection mold further comprises a cooling system comprising a cooling channel configured to receive a cooling liquid.

15 . The method of claim 14 , wherein the induction coil is configured to heat the cavity surface against a cooling effect of the cooling system while the cooling liquid is in the cooling channel.

16 . The method of claim 15 , wherein the cooling liquid cools the cavity surface to a demolding temperature after the induction coil is deactivated.

17 . The method of claim 16 , further comprising removing molded parts after the cavity surface reaches the demolding temperature.

18 . The method of claim 17 , wherein the demolding temperature is between approximately 50-100° F. less than the target temperature.

19 . The method of claim 17 , further comprising reactivating the induction coil after the molded parts are removed.