WO2001056765A1

WO2001056765A1 - A golf ball casting mold assembly

Info

Publication number: WO2001056765A1
Application number: PCT/US2001/003256
Authority: WO
Inventors: Gary G. Marshall
Original assignee: Callaway Golf Company
Priority date: 2000-02-01
Filing date: 2001-01-31
Publication date: 2001-08-09
Also published as: US6439873B1; AU2001234715A1; JP2001252934A

Abstract

A mold assembly (20) designed for casting a layer for a golf ball is disclosed herein. The mold assembly (20) has two halves (22a) (22b) that each hold a plurality of mold inserts (30). Each mold half (22a) (22b) is composed of a carrier base (24), a carrier plate (26), a retainer plate (28) and a plurality of mold inserts (30). The multiple component aspect of each mold half (22a) (22b) allows for a more efficient transfer of heat during a casting process. Preferably, the mold assembly (20) is utilized to mold a polyurethane cover on a golf ball precursor product (25).

Description

Title

A GOLF BALL CASTING MOLD ASSEMBLY

Technical Field

The present invention relates to a mold for forming a golf ball cover layer. More

specifically, the present invention relates to a mold for forming a thermoset polyurethane

cover on a golf ball core.

Background Art

Golf balls may comprise one-piece constructions or they may include several

layers including a core, one or more intermediate layers and an outer cover that surrounds

any intermediate layer and the core. In multi-component golf balls, there exists an inner

core. Often, this core is made by winding a band of elastomeric material about a

spherical elastomeric or liquid-filled center. Alternatively, the core may be a unitary

spherical core made of a suitable solid elastomeric material. One such material that is

conventionally used for the core of golf balls is a base rubber, such as polybutadiene,

which is cross-linked with a metal acrylate, such as zinc diacrylate.

In the construction of some multi-component golf balls, an intermediate boundary

layer is provided outside and surrounding the core. This intermediate boundary layer is

thus disposed between the core and the outer cover of the golf ball.

Located outwardly of the core and any intermediate boundary layer is a cover.

The cover is typically made from any number of thermoplastic or thermo setting materials, including thermoplastic resins such as ionomeric, polyester, polyetherester or

polyetheramide resins; thermoplastic or thermoset polyurethanes; natural or synthetic

rubbers such as balata (natural or synthetic) or polybutadiene; or some combination of the

above.

Golf balls are typically manufactured by various molding processes, whether one-

component or multicomponent balls. Generally, the core of the golf ball is formed by

casting, compression molding, injection molding or the like. If an intermediate boundary

layer is desired, one or more intermediate boundary layers are added over the core by any

number of molding operations, including casting, compression molding, and/or injection

molding. The cover is then formed over the core and intermediate boundary layers, if

present, through casting, compression molding, and/or injection molding.

One of the earliest disclosures of manufacturing a golf ball with dimples is set

forth in U.S. Patent Number 721,462 to Richards, which was filed on May 26, 1902.

Richards discloses covering a core that is centered with pins within a spherical cavity of a

mold, with a fluent gutta percha material. The gutta percha material is subjected to high

pressure and then cooled within the mold to form a cover on the core.

Bowerman et al., U.S. Patent Number 2,940,128, which was filed on May 14,

1958, discloses a method of manufacturing a rubber covered golf ball. Bowerman

discloses separately forming rubber hemispherical covers on the core. One of the earliest methods of manufacturing a polyurethane cover is disclosed in

Gallagher, U.S. Patent Number 3,034,791, which was filed on April 26, 1960. Gallagher

discloses forming polyurethane disks that are then molded over cores to create a

polyurethane cover.

Another early method of manufacturing a polyurethane cover is disclosed in

Ward, U.S. Patent 3,147,324, which was filed on October 20, 1960. Ward discloses

using a liquid polyurethane prepolymer, either polyether-type or polyester-type, that is

cured with a diamine. The liquid polyurethane is poured into a hemispherical mold

cavity of a mold half, and a wound golf ball core is centered therein. Subsequently, a

corresponding hemispherical mold cavity of a second mold half is filled with the liquid

polyurethane. The first mold half with the wound core is then mated with the second

mold half and allowed to cure for a set period of time.

A second Ward patent directed toward forming a polyurethane cover is U.S.

Patent Number 3,112,521, which was filed on March 8, 1961. The '521 Ward patent

discloses a method and apparatus for sensing the center of a wound core prior to

placement in a mold filled with liquid polyurethane which is part of a complete casting

machine. As with the '324 Ward patent, liquid polyurethane is poured into a

hemispherical mold cavity of a mold half. However, in the '521 Ward patent, the wound

core is more precisely centered prior to insertion into the polyurethane filled cavity. The

entire process of the '521 Ward patent is performed on a rotatable annular platform. Another example of a method for making a polyurethane cover is disclosed in

Watson et al., U.S. Patent Number 3,130,102, filed originally in Great Britain on May 19,

1960. Watson discloses a process for partially forming polyurethane half-shells for a

golf ball, cooling them, then fusing them together on a core while imparting a dimple

pattern thereon. Watson also demonstrates better cutting resistance for its polyurethane

covered golf ball. An alternative of the Watson process for making a polyurethane cover

on a golf ball is disclosed in a related patent to Ford et al., U.S. Patent Number

3,177,280, filed originally in Great Britain on May 23, 1960. Ford discloses coating a

core until the required thickness is applied, however, it still requires interrupting the

curing, to place the coated core into a mold to impart a dimple pattern thereon.

Building upon Ford and Watson, U.S. Patent Number 3,989,568 to Isaac discloses

a process for using curing agents that have different reaction rates to partially cure a

polyurethane half shell that is later placed on a core for further processing. Isaac

discloses that a cover may be as thin as 0.025 inches using this process which involves

two different diisocyanates and different amine curing agents. Dusbiber, U.S. Patent

Number 3,979,126, originally filed in February of 1965, discloses another method of

making polyurethane half shells for a golf ball cover.

Brown et al, U.S. Patent Number 5,006,297, filed on February 22, 1989,

discloses openly curing both halves of polyurethane cover in an initial mold, then

compression molding the smooth covered golf ball to form a dimple pattern thereon. The initial molding step may use retractable or non-retractable pins to center the wound core

while polyurethane flows about it.

Wu, U.S. Patent Number 5,334,673 discloses the multiple step process of Ford

and Watson using a slow-reacting polyamine curing agent. Wu et al., U. S. Patent

Number 5,692, 974 discloses the difficulty in manufacturing a commercially viable

polyurethane covered golf ball due to the centering of the core within a partially cured

mixture of polyurethane. The '974 Wu patent states that the 1993 Titleist®

PROFESSIONAL was the first successful polyurethane covered golf ball.

Calabria et al., U.S. Patent Numbers 5,733,428; 5,888,437; 5,897,884; and

5,947,843 all originate from an application filed on January 21, 1994 which was a

continuation-in-part application of an abandoned application filed on July 6, 1992. The

Calabria family of patents disclose a method and apparatus for forming a wound core golf

ball with a polyurethane cover. The apparatus of Calabria, similar to that of the '521

Ward patent, inserts a wound core into a half mold cavity of partially cured polyurethane.

Calabria discloses using a single insertion device for each individual mold. Calabria

introduces the polyurethane mixture into a top mold half and after 50 to 80 seconds later a

core is lowered at a controlled rate to prevent air bubbles, and a stop limits the downward

movement of the core into the mold cavity. At a later time the bottom mold halves are

filled with the polyurethane mixture. After another 50 to 80 seconds, the vacuum holding

the core is released and mold halves are removed from the centering fixture. The top mold halves are then mated with the bottom mold halves and excess material resides in

sprue channels. The mold halves are heated and pressurized for a predetermined period

of time, and then demolded.

Herbert et ah, U.S. Patent Number 5,885,172, which was filed on May 27, 1997,

discloses using the process of Calabria to form a polyurethane cover over a core with an

inner layer thereon. Wu, U.S. Patent Number 5,908,358, which was originally filed on

June 7, 1995, discloses using a four mold unit to manufacture golf balls with

polyurethane covers.

Dewanjee, et ah, PCT International Publication Number WO 99/43394, claiming

priority from U.S. Patent Application Number 09/030,332, filed on February 25, 1998

discloses a method for forming a polyurethane cover on a golf ball. Dewanjee discloses

using a X-Y table to position mold halves under a mix head that dispenses the

polyurethane mixture. The mold halves are then placed on a conveyor for transport to a

core insertion station. The cores are then centered over each cavity through use of a pin

on the mold half that engages with an aperture on the core holding unit. A second mold

half is mated with the first mold half, and the mold is heated under pressure to form a

polyurethane cover over the core. De-molding is accomplished through insertion of mold

releasing pins into apertures of the mold halves. Consequently, there remains a need for methods of manufacturing golf balls that

do not suffer from the above disadvantages. Moreover, the methods would preferably

decrease the production time to manufacture golf balls.

Disclosure of the Invention

The mold assembly of the present invention is able to provide a solution to the

problems of the prior art. The present invention is able to accomplish this by providing a

novel mold assembly design that allows for a greater number of golf ball precursor

products to be processed simultaneously, and allows for a more efficient transfer of heat

during the casting process.

One aspect of the present invention is a mold assembly for forming a layer on a

golf ball precursor product. The mold assembly includes a first mold half and a second

mold half. The first mold half includes a first central hub mechanism having a first

plurality of hemispherical cavities disposed circularly equidistant about the first central

hub mechanism, and a second central hub mechanism having a second plurality of

hemispherical cavities disposed circularly equidistant about the second central hub

mechanism. The second mold half includes a third central hub mechanism having a third

plurality of hemispherical cavities disposed circularly equidistant about the third central

hub mechanism, and a fourth central hub mechanism having a fourth plurality of hemispherical cavities disposed circularly equidistant about the fourth central hub

mechanism. The first and second central hub mechanisms engage with the third and

fourth central hub mechanisms during mating of the first mold half with the second mold

half.

Another aspect of the present invention is mold assembly that includes multiple-

component first and second mold halves. The first and second mold halves each include

a carrier base, a carrier plate, a plurality of mold inserts and a retainer plate. Each carrier

base has a plurality of studs extending from an interior surface. Each carrier plate has a

plurality of insert apertures with each having a first diameter and a plurality of hub

apertures therein. Each carrier plate is mounted on the plurality of studs of the carrier

base. Each of the plurality of mold inserts is disposed within a corresponding insert

aperture of the plurality of insert apertures. Each retainer plate has a plurality of insert

apertures with each having a second diameter. Each retainer plate is mounted on the

carrier plate, and each of the plurality of insert apertures is positioned above a

corresponding mold insert of the plurality of mold inserts.

Brief Description of the Drawings

FIG. 1 is a side view of a mold assembly of the present invention.

FIG. 1A is a cross-sectional view of a golf ball. FIG. 2 is a top plan view of a first mold half of the mold assembly of FIG. 1.

FIG. 3 is a cross-sectional views of the first mold half of FIG. 2.

FIG. 4 is a top plan view of a second mold half of the mold assembly of FIG. 1.

FIG. 5 is a cross-sectional views of the second mold half of FIG. 4.

FIG. 6 is a schematic top plan view of a mold half of the prior art.

FIG. 6 A is a schematic top plan view of another mold half of the prior art.

FIG. 7 is a schematic side view of the mold half of FIG. 6.

FIG. 8 is a top plan view of a carrier base of a mold half of a mold assembly of

the present invention.

FIG. 9 is a bottom plan view of a carrier plate of a mold half of a mold assembly

of the present invention.

FIG. 10 is a top plan view of a carrier plate of a mold half of a mold assembly of

the present invention.

FIG. 1 1 is a top plan view of a retainer plate of a mold half of a mold assembly of

the present invention.

FIG. 12 is a side view of a mold insert of the mold assembly of the present

invention.

FIG. 13 is a top plan view of the mold insert of FIG. 12 illustrating the inverse

dimple pattern of the cavity of the mold insert. FIG. 14 is a side view of a mold insert of FIG. 12 with a golf ball precursor

product therein.

FIG. 15 is an enlarged top view of the retainer plate with an insert radial locating

plate. FIG. 16 is an enlarged view of a hub mechanism and mold inserts of a mold half

of the mold assembly of the present invention.

Best Mode(s) for Carrying Out the Invention

As shown in FIGS. 1-5, a mold assembly for casting a layer of a thermoset

material on a golf ball precursor product is generally designated 20, and is composed of a

first mold half 22a and a second mold half 22b. In a preferred embodiment, the first mold

half 22a is the top mold half and the second mold half 22b is the bottom mold half. The

mold halves 22a-b are mated together during a casting process as set forth in co-pending

U.S. Patent Application Number 09/496,126 filed on an even date herewith, entitled

System And Method For Forming A Thermoset Golf Ball Cover, which is hereby

incorporated in its entirety by reference.

As shown in FIG. 1, a set of golf ball precursor products 25 are placed within the

first mold half 22a which is inverted for mating with the second mold half 22b. The golf

ball precursor products 25 may be a core (solid, liquid or hollow) that is wound or non- wound. Each golf ball precursor product 25 may also have one or more intermediate or

boundary layers over the core portion. The thermoset material layer that is casted in the

mold assembly 20 is preferably the cover layer 27c of the golf ball 27, however, it may

also be the boundary layer 27b. A preferred thermoset material is polyurethane such as

described in co-pending U.S. Patent Application Number 09/295,635, entitled

Polyurethane Cover For A Golf Ball, which pertinent parts are hereby incorporated by

reference. However, those skilled in the relevant art will recognize that other thermoset

materials may be used with the mold assembly 20 without departing from the scope and

spirit of the present invention.

Referring again to FIGS. 1-5, each mold half 22a-b is generally composed of a

carrier base 24, a carrier plate 26 and a retainer plate 28. Each mold half 22a-b also has a

plurality of mold inserts 30 positioned within mold insert apertures 31 of the retainer

plate 28 and mold insert apertures 33 of the carrier plate 26.

The carrier plate 26 is sandwiched between the carrier base 24 and the retainer

plate 28. The carrier plate 26 carries the mold inserts 30 during the casting process. The

retainer plate 28 is designed to lock each of the mold inserts 30 in the carrier plate 26.

The carrier base 24 is the mold assembly's 20 contact surface during conveyance through

a casting system.

Compared to the solid one-piece body mold halves 1 OOa-b of the prior art

illustrated in FIGS. 6, 6A and 7, each mold half 22a-b of the present invention is composed of multiple stacked components that minimize the mass of the mold assembly

20 while providing sufficient structural support to withstand the high pressure forces

during the casting process. The multiple component structure of each mold half 22a-b

allows for a more efficient transfer of heat to the mold halves 22a-b than the prior art

since there is less metal per mold cavity. Further, the mold halves lOOa-b of the prior art

had the cavities 102a-b as part of the body of the mold half lOOa-b. The mold halves 22a-

b are heated to prevent problems with the dispersion of the exothermic thermoset material

into each mold cavity. Further, the mold assembly 20 is capable of casting a layer on a

greater number of golf ball precursor products 25 than the prior art mold assemblies.

As shown in FIG. 8, the carrier base 24 has a substantially flat body 60 and is

preferably composed of a rolled steel material. The thickness of the carrier base 24 is

between 0.2 and 1.0 inches. The body 60 has two cut-outs 62a-b located in the center for

stopping on a casting apparatus. The body 60 also has two hub apertures 64a-b for

assembling of the mold half 22. The body 60 also has stud spacers 66a-d that elevate the

carrier plate 26 approximately 1.0 inch.

As shown in FIGS. 9 and 10, the carrier plate 26 is mounted on top of the carrier

base 24. The carrier plate 26 has a body 70 has a thickness that is preferably between 0.3

and 1.0 inches. The body 70 is preferably composed of a mild steel material. The body

70 has two equal sets of insert apertures 33 for housing each of the mold inserts 30. Each

set of insert apertures 33 is positioned about a hub aperture 72a-b. The insert apertures 33 are equidistant from their respective hub aperture 72, and equidistant from each other

within the set. Preferably, the insert apertures each have a diameter that ranges from

2.00 to 3.00 inches, and each diameter is larger than the diameter of the mold insert 30.

The body 70 also has locating apertures 74a-d at each corner for mounting locating pins

92a-b and locating bushings 94a-b.

The locating pins 92a-b and bushings 94a-b properly align the mold halves 22a-b

during mating thereof to form the mold assembly 20. In a preferred embodiment, the

locating pins 92a-b are diagonally opposed to each other on the second mold half 22b.

The locating bushings 94a-b are disposed on the first mold half 22a. Each locating pin

92a-b may be extended or retracted for molding and de-molding purposes. The top of

each locating pins 92a-b is tapered or indented for assistance during the de-molding

separation of the first and second mold halves 22a-b. Alternatively, the locating pins 92a-

b may be fixed with a double tapered top.

The hub mechanisms 40 are placed through the afore-mentioned hub apertures

72a-b on each of the mold halves 22a-b. Each hub mechanism 40a-b for the first mold

half 22a has a stud adapter 80, a spring 82, a backing plate 84 and a bolt 86. Each hub

mechanism 40c-d for the second mold half 22b has a stud adapter 80, a spring 82, a

backing plate 84 and a nut 88. When the first mold half 22a is mated with the second

mold half 22b, each bolt 86 is connected with a corresponding nut 88. Preferably, the

bolts 86 are threadingly connected to the nuts 88, and each bolt 86 has a spring 90 attached thereto to keep the bolt 86 extended through the carrier plate 26. Those skilled

in the art will recognize that the bolts 86 may be used on the second or bottom mold half

22b and the nuts 88 on the top or first mold half 22a. Further, those skilled in the art will

recognize that each mold half 22a-b may have one nut 88 and one bolt 86.

As shown in FIG. 11 , the retainer plate 28 has a body 110 with a curved perimeter

to reduce mass. The body is preferably composed of cold-rolled steel, and preferably has

a thickness between 0.1 and 0.2 inches. The retainer plate 28 is designed to secure the

mold inserts 30 within the carrier plate 26 with the minimum amount of mass. The

retainer plate 28 has an equal number of insert apertures 31 as the insert apertures 33 of

the carrier plate 26. Further, the insert apertures 31 are smaller in diameter than the insert

apertures 33 of the carrier plate 26. The retainer plate 28 also has two hub apertures

112a-b, which allow for engagement of the bolt 86 with the nuts 88. Each set of insert

apertures 31 is positioned about a hub aperture 112a-b. The insert apertures 31 are

equidistant from their respective hub aperture 112, and equidistant from each other within

the set. Preferably, each of the insert apertures 31 has a diameter that ranges from 2.00

to 3.00 inches. The retainer plate 28 is secured to the carrier plate 26 using conventional

methods.

FIGS. 12-14 illustrate the mold inserts 30 used with the mold assembly 20 of the

present invention. Each mold insert 30 has a hemispherical cavity 32 within a body 34.

Around a center height of the body 34 is an annular flange 36 that has an alignment flat 38 along a portion thereof. The flange 36 is used for mounting each mold insert 30 on

the carrier plate 26.

The hemispherical cavity 32 preferably has an inverse dimple pattern thereon if a

cover 27c is formed in the mold insert 30. However, the hemispherical cavity 32 will

have a smooth surface if a boundary layer 27b is formed in the mold insert 30. The

number of mold inserts 30 used for each mold half 22a-b may preferably range from eight

to twelve, and is most preferably ten. In the preferred embodiment, as shown in FIGS. 2

and 4, five mold inserts 30a-e are positioned about hub mechanism 40a, five mold inserts

30f-j are positioned about hub mechanism 40b, five mold inserts 30k-o are positioned

about hub mechanism 40c, and five mold inserts 30p-t are positioned about hub

mechanism 40d. Those skilled in the art will recognize that more or less than five inserts

may be positioned about each hub mechanism 40a-d without departing from the scope

and spirit of the present invention.

As shown in FIGS. 15-16, each mold insert 30 of a set of mold inserts 30 is

properly oriented using a insert radial locator plate 44 that is placed about the hub

mechanism 40. Each insert radial locator plate 44a-d has straight edges to oppose the

alignment flat 38 of each of the mold inserts 30. Once the locator plate 44 and the

respective mold inserts 30 are aligned, the mold inserts 30 and the locator plate 44 are

locked together to prevent rotation thereby ensuring that the top and bottom mold inserts

30 are oriented properly when mated, to produce the correct dimple pattern on the golf ball. Further, each mold insert may be a replaceable mold insert as set forth in co-

pending U.S. Patent Application 09/310,785, entitled Replaceable Mold Inserts For Golf

Balls, which pertinent parts are hereby incorporated by reference.

In a preferred casting process, each cavity 32 of each mold insert 30a-j is filled

with a flowable polyurethane mixture. The mixture is allowed to gel, or partially cure,

then a golf ball precursor product 25 is inserted in each of the mold inserts 30a-j of the

first mold half 22a. During this time, the cavity 32 of the mold inserts 30k-t of the

second mold half 22b, have received a predetermined quantity of the flowable

polyurethane mixture. The first mold half 22a is then inverted and mated with the second

mold half 22b to form the mold assembly 20 with each mold insert 30a-j of the first mold

half 22a aligning with a corresponding mold insert 30k-t of the second mold half 22b.

The bolts 86 are then preferably threadingly engaged with the nuts 88.

Claims

1. A mold assembly for forming a layer on a golf ball precursor product, the mold

assembly comprising:

a first mold half comprising a first central hub mechanism having a first

hub mechanism, and a second central hub mechanism having a second plurality of

mechanism; and

a second mold half comprising a third central hub mechanism having a

third plurality of hemispherical cavities disposed circularly equidistant about the third

central hub mechanism, and a fourth central hub mechanism having a fourth plurality of

hemispherical cavities disposed circularly equidistant about the fourth central hub

mechanism; wherein the first and second central hub mechanisms engage with the third

and fourth central hub mechanisms during mating of the first mold half with the second

mold half.

2. The mold assembly according to claim 1 wherein each of the first mold half and

the second mold half further comprises: a carrier base having a plurality of studs extending from an interior

surface;

a carrier plate having a plurality of insert apertures with each having a first

diameter and a plurality of hub apertures therein, the carrier plate disposed on the

plurality of studs of the carrier base; and

a retainer plate having a plurality of insert apertures with each having a

second diameter, the retainer plate disposed on the carrier plate and each of the plurality

of insert apertures positioned above a corresponding mold insert of the plurality of mold

inserts and wherein the first diameter is greater than the second diameter.

3. The mold assembly according to claim 1 further comprising at least one locator

pin, the at least one locator pin adjusting from a molding position to a de-molding

position for separation of the first mold half from the second mold half.

4. The mold assembly according to claim 2 wherein the first mold half further

comprises at least one spring backing plate mechanism disposed between the first carrier

base and the first carrier plate, and the second mold half further comprises at least one

spring backing plate mechanism disposed between the second carrier base and the second

carrier plate.

5. The mold assembly according to claim 2 further comprising a plurality of insert

radial locating plates wherein each group of five or more of the plurality of mold inserts

is restrained by an insert radial locating plate.

6. A mold assembly for forming a layer on a golf ball precursor product, the mold

assembly comprising:

a first mold half comprising

a first carrier base having a plurality of studs extending from an

interior surface,

a first carrier plate having a plurality of insert apertures with each

having a first diameter and a plurality of hub apertures therein, the first carrier plate

disposed on the plurality of studs of the first carrier base,

a plurality of mold inserts, each plurality of mold inserts disposed

within a corresponding insert aperture of the plurality of insert apertures, and

a first retainer plate having a plurality of insert apertures with each

having a second diameter, the retainer plate disposed on the first carrier plate and each of

the plurality of insert apertures positioned above a corresponding mold insert of the

plurality of mold inserts and wherein the first diameter is greater than the second

diameter; and

a second mold half comprising a second carrier base having a plurality of studs extending from an

interior surface,

a second carrier plate having a plurality of insert apertures with

each having a first diameter and a plurality of hub apertures therein, the second carrier

plate disposed on the plurality of studs of the second carrier base,

a second plurality of mold inserts, each plurality of mold inserts

disposed within a corresponding insert aperture of the plurality of insert apertures, and

a second retainer plate having a plurality of insert apertures with

each having a second diameter, the retainer plate disposed on the second carrier plate and

each of the plurality of insert apertures positioned above a corresponding mold insert of

the plurality of mold inserts and wherein the first diameter is greater than the second

diameter.

7. A mold assembly for forming a layer on a golf ball precursor product, the mold

assembly comprising:

a first mold half comprising

a first carrier plate having a first hub aperture with a first plurality

of insert apertures disposed circularly equidistant about the first hub aperture, and a

second hub aperture with a second plurality of insert apertures disposed circularly

equidistant about the second hub aperture, each of the first and second pluralities of insert apertures having a first diameter,

a first plurality of mold inserts, each plurality of mold inserts

disposed within a corresponding insert aperture of the first and second pluralities of insert

apertures, and each of the first plurality of mold inserts having a cavity with an inverse

dimple pattern,

first and second hub bolts extending through first and second hub

apertures; and

a first retainer plate having a plurality of insert apertures with each

plurality of mold inserts, wherein the first diameter is greater than the second diameter,

and the first retainer plate having a first and second hub aperture for the first and second

hub bolts to extend through; and

a second mold half comprising

a second carrier plate having a third hub aperture with a third

plurality of insert apertures disposed circularly equidistant about the third hub aperture,

and a fourth hub aperture with a fourth plurality of insert apertures disposed circularly

equidistant about the fourth hub aperture,

a second plurality of mold inserts, each of the second plurality of

mold inserts disposed within a corresponding insert aperture of the third and fourth pluralities of insert apertures, and each of the second plurality of mold inserts having a

cavity with an inverse dimple pattern,

first and second hub receptors disposed within the third and fourth

hub apertures for receiving the first and second hub bolts respectively; and

a second retainer plate having a plurality of insert apertures with

each having a second diameter, the second retainer plate disposed on the second carrier

plate and each of the plurality of insert apertures positioned above a corresponding mold

insert of the plurality of mold inserts, wherein the first diameter is greater than the second

diameter, and the second retainer plate having a third and fourth hub apertures for the first

and second hub bolts to extend through to engage the first and second hub receptors.