To push performance, golf clubs are taking advantage of space-age materials and methods. Although steel still plays a key role in building clubs, titanium has come on strong as a contender for making long-distance drivers. And in the wings, wait other new-age materials to improve club performance.

By Gil Bassak, Technical Editor

The trend to have aerospace technology, materials in particular, adopted by sporting goods manufacturers is alive and well and improving the performance of golfing equipment – specifically, golf clubs. Witness, for instance, the growing use of – and demand for high-strength steel alloy and lightweight titanium club heads and the emergence of graphite-composite shafts.

Inserts from Carpenter Technology Corp. include the company's popular Custom 455 and Custom 456 stainless steel alloys, which are found mostly in fairway woods, irons, and wedges.

Case in point: The AerMet alloy family of high strength-to-weight metals from Carpenter Technology Corp., first used in the landing gear of the F-18 fighter jet, is now a popular material for making golf club inserts, or club faces. "The idea is to take advantage of certain materials to optimize what the golfer needs," says James Scutti, a professional engineer and technical director at Massachusetts Materials Research Inc., a company that Scutti says helps people solve problems with materials.

In the future, he adds, look for golf club makers to turn to metal-matrix composites, in which metals are infused with bits of ceramic, and polymer-matrix composites, which mix in, for instance, Kevlar and graphite – all to tailor the material's performance while keeping it light. Particular promise is seen in titanium-silicon carbide, which mixes titanium with silicon carbide particles, "basically the grit in sandpaper," says Scutti. There are even hints of bringing the science of nanotechnology to golf equipment manufacture to increase the swing speed and volume while cutting club surface thickness and mechanical tolerances.

For the original design manufacturers (ODM), many of which are in Taiwan, where the clubs are actually designed and made, these advances demand manufacturing agility, including customization capabilities and quick turnaround, to meet market demands.

What Golfers Need

What golfers need, says Scutti, is a good transfer between their swing and the golf ball. For fairway woods, irons, and wedges, this frequently means the use of a forged steel insert at the club face. The insert is needed because the club body itself is cast, a technique whose porosity and large-grain structure degrade performance. (See adjacent box "Casting Club Heads.") In contrast, the forged insert, with its non-porous, fine-grain structure, transfers energy efficiently to the ball.

Inserts from Carpenter, for example, include the company's popular AerMet 100 steel alloys as well as its Custom 455 and Custom 456 stainless steel alloys – part of the firm's TourAlloy family – which are found mostly in such distance clubs as fairway woods, irons, and wedges. (See adjacent box "Stealing Steel.") In all, the company offers more than a dozen different alloys of various hardnesses and strengths for the golf industry.

Solution-treated and aged, the alloys in this group blend such elements as carbon, chromium, cobalt, molybdenum, and nickel, and – for Custom 455 and Custom 456 – are precipitation hardened. In precipitation hardening, which yields high strength and hardness, the alloy is heated until it becomes "compositionally homogenous," explains James M. Dahl, a product application specialist for Carpenter Technology Corp. Then it is cooled to room temperature and reheated to an intermediate temperature, around 900°F, a process that forms little particles – precipitates – within the steel to enhance its strength.

The call for such high-performance steel alloys should grow with a move by the United States Golf Association (USGA) to limit both a club's head size (to 385 cubic centimeters) and the speed with which a ball can leave the club head (called the coefficient of restitution). Specifically, these constraints will likely force club designers to find new ways to deliver longer distances and a larger sweet spot.

To meet demands for customized designs, high accuracy and quality, and fast time to market, O-TA Precision Industry Co., Ltd. develops 90 percent of its products using Pro/Engineer five-axis milling CAD software.

For the club heads of drivers, the trend continues to be toward titanium, whose light weight – titanium has the strength of steel at half the weight – makes it best suited for these large "Cadillacs" of clubs, as Dahl calls them. Because joining forged steel to a titanium casting is not practical, these clubs typically use inserts of forged titanium. To add to the appeal of titanium drivers, says Dahl, "their price has come down so much that they are pushing steel out of the market for drivers."

As for golf club shafts, there is a definite trend toward carbon graphite. "One way to get a good energy transfer between the swing and the ball is to have a good whip in the shaft," says Dahl. For this, he says, carbon graphite works very well. "It's a very, very stiff material, and it can be tailored very simply to give 'whipishness' or stiffness."

Agile Manufacturing

These technical changes in golf club design are keeping design and manufacturing houses on their toes. "In the fast changing golf industry, product development is critical," notes Bill Lin, general manager for O-TA Precision Industry Co., Ltd., a golf club ODM. "Each vendor has its own demands for price, shape, material, weight, hardness, stability, center of gravity, and other specifications for their club heads."

A short product life cycle is another hurdle facing ODMs. "We must always speed our time to market in order to help our customers and ourselves stay ahead of our competitors," says Lin. To meet these demands, while increasing accuracy and quality, O-TA develops 90 percent of its products using Pro/Engineer five-axis milling CAD software.

Also important, says Lin, is to have a "seamless and real-time information infrastructure." To that end, the company has initiated a plan that will allow all its employees and suppliers in Taiwan and mainland China to respond efficiently to design changes or customer demands. Moreover, for collaborative product development, the company has networked a large share of its businesses over the Internet, a move that Lin says has lowered costs, improved quality, and shortened development time.

Sidebar

Casting Club Heads

Investment casting, a centuries-old technique, is still used today in manufacturing in both the aerospace and golf club industries. Also called the lost-wax method, it produces a casting that needs little grinding or other machining.

The process starts with a piece of wax in the shape of, say, a golf-club head. The wax is then dipped in a slurry of ceramic particles – what James Scutti, technical director at Massachusetts Materials Research Inc., calls a "milkshake." "You dip it and let it dry, and then dip it again and let it dry again," he says, "just like when you were a kid and made candles by dipping a string in wax."

The resulting ceramic shell goes into a furnace that burns off the wax, leaving behind a ceramic mold that is exactly the shape that you want for the metal. Next, molten metal is poured into the mold and allowed to cool. The ceramic mold is then cracked away, leaving only the casting. Although the molds are clearly not reusable, says Scutti, manufacturers have automated the process using robotics. As a result, "the advantages outweigh the cost in terms of not having to buff or straighten anything."

Sidebar

Stealing Steel

The appeal of certain steel alloys has attracted the attention of some unsavory hawkers of "counterfeit alloys," says James M. Dahl, a product application specialist for Carpenter Technology Corp. His company makes proprietary alloys of precipitation-hardened stainless steel called Custom 455 and Custom 456, which are used for inserts in clubs from TaylorMade, Nike, and other major vendors. Dahl says several OEMs have reported that some foundries making club heads have been approached with offers of "455" and "465" alloys for half what Carpenter charges.

"We cannot trademark just three digits," says Dahl. "What they are playing on is the number. They are not saying 'Custom 455' or 'Custom 456.' They are using the vernacular." Composition-wise, he adds, the counterfeit alloys are "not even close to our alloys, yet they are being palmed off as the real thing."

More information on the design technologies featured in this article is available by contacting the companies directly, writing in the corresponding numbers on our reader service card, or replying online at www.pddnet.com.

Carpenter Technology Corp.Box 14662Reading, PA 19612(610) 208-2235www.cartech.comMassachusetts Materials Research Inc.Box 8101500 Century Dr.West Boylston, MA 01583(508) 835-6262www.mass-mat.comO-TA Precision Industry Co., Ltd.No. 8 Chien-Fu Rd.Nei-Tung HsienTaiwan, R.O.C.886-8-7783855www.o-ta.com.tw

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