Golf club heads with variable face thickness

1. A method of manufacturing a golf club head, the method comprising:

(a) forming a golf club head main body by either a forging process or an investment casting process, a golf club head main body including a heel, a toe opposite the heel, a sole, and a top portion opposite the sole;

(b) determining, with a computing device, a variable face thickness pattern of a striking face for the golf club head by:

(i) setting a target value for a first constraint;

(ii) on a computer-simulated striking face having a simulated face center, defining a plurality of parametrization zones including a central zone having the simulated face center;

(iii) for each parametrization zone, setting values for a first parameter and a second parameter;

(iv) simulating impacts for a plurality of impact locations about the simulated striking face;

(v) evaluating resultant first constraint values from the simulated impacts against the target first constraint value; and

(vi) changing the values for the first parameter and the second parameter by increasing or decreasing the values, such changes in values resulting in a simulated variable face thickness pattern;

(c) forming the striking face such that the striking face includes a variable face thickness pattern corresponding to the simulated variable face thickness pattern; and

(d) attaching the striking face to the golf club head main body,

wherein the golf club head has blade length less than 80 mm and a moment of inertia, Izz, and a golf club head mass, mh, that satisfies: Izz>mh*9.3 cm 2 .

2. The method of claim 1 , wherein step (c) further includes:

defining a central region, an intermediate region, and at least one of an upper region, a lower region, and a toe region;

recessing the central region to have a thickness less than a thickness of the intermediate region; and

recessing the at least one of the upper region, the lower region, and the toe region to have a thickness less than that of the central region thickness.

3. The method of claim 2 , wherein the central region, the intermediate region, the upper region, the lower region, and the toe region each correspond to one of the plurality of parametrization zones.

4. The method of claim 2 , wherein the golf club head has a weighted coefficient of restitution of no less than 0.79.

5. The method of claim 2 , wherein the intermediate region has a thickness of at least 2.5 mm and no more than 3.3 mm.

6. The method of claim 2 , wherein the recessing steps comprise removing material by machining.

7. The method of claim 1 , wherein the first parameter is a parametrization zone width and the second parameter is a parametrization zone thickness.

8. The method of claim 1 , wherein the first constraint is a mechanical stress limit of the striking face.

9. The method of claim 1 , wherein the golf club head is an iron-type cavity-back golf club head.

10. The method of claim 1 , wherein the golf club head has a topline thickness of no more than 6.5 mm.

11. A method of manufacturing a golf club head, the method comprising:

(a) forming a golf club head main body by either a forging process or an investment casting process, a golf club head main body including a heel, a toe opposite the heel, a sole, and a top portion opposite the sole;

(b) determining, with a computing device, a variable face thickness pattern of a striking face for the golf club head by:

(i) setting a target value for a first constraint;

(ii) on a computer-simulated striking face having a simulated face center, defining a plurality of parametrization zones including a central zone having the simulated face center;

(iii) for each parametrization zone, setting values for a first parameter and a second parameter;

(iv) simulating impacts for a plurality of impact locations about the simulated striking face;

(v) evaluating resultant first constraint values from the simulated impacts against the target first constraint value; and

(vi) changing the values for the first parameter and the second parameter by increasing or decreasing the values, such changes in values resulting in a simulated variable face thickness pattern;

(c) forming the striking face such that the striking face includes a variable face thickness pattern corresponding to the simulated variable face thickness pattern; and

(d) attaching the striking face to the golf club head main body,

wherein the golf club head has a blade length less than 80 mm, a maximum coefficient of restitution at a first location of the striking face, and a second coefficient of restitution that is no less than 98% of the maximum coefficient of restitution at a second location of the striking face that is at least 7.5 mm away from the first location.

12. The method of claim 11 , wherein the second coefficient of restitution is no less than 99% of the maximum coefficient of restitution.

13. The method of claim 11 , step (c) includes:

defining a central region, an intermediate region, and at least one of an upper region, a lower region, and a toe region;

recessing the central region to have a thickness less than a thickness of the intermediate region; and

recessing the at least one of the upper region, the lower region, and the toe region to have a thickness less than that of central region thickness.

14. The method of claim 13 , wherein the central region, the intermediate region, the upper region, the lower region, and the toe region each correspond to one of the plurality of parametrization zones.

15. The method of claim 13 , wherein the golf club head has a weighted coefficient of restitution of no less than 0.79.

16. The method of claim 13 , wherein the intermediate region has a thickness of at least 2.5 mm and no more than 3.3 mm.

17. The method of claim 13 , wherein the recessing steps comprise removing material by machining.

18. The method of claim 11 , wherein the first parameter is a parametrization zone width and the second parameter is a parametrization zone thickness.

19. The method of claim 11 , wherein the first constraint is a mechanical stress limit of the striking face.

20. The method of claim 11 , wherein the golf club head is an iron-type cavity-back golf club head.