The two leading golf ball producers also differ about the best method of forming the cover and dimples on a two-piece ball. Spalding employs conventional injection molding while Titleist uses compression molding. In the former, the core is centered within a mold cavity by pins and molten thermoplastic is injected into the dimpled cavity surrounding the core. As the plastic cools and hardens, the pins are retracted.
With compression molding, the cover is the first injection molded into two hollow hemispheres. These are positioned around the core, heated and then pressed together, using a mold which fuses the cover to the core and also forms the dimples.
Spalding claims that injection molding provides greater uniformity and accuracy because two halves don’t need to fit perfectly together. The injection process also offers the potential for greater distance because of the high stress involved, Spalding says. Titleist believes that compression molding offers greater consistency because the core cannot shift off-center as it says can happen following removal of the pins in the injection process.
Three-piece balls are all compression molded. “No one to my knowledge has been able to injection mold the cover over a wound ball. The hot plastic flowing through would distort and probably cause breaks in the rubber threads,” says Walter Reid, director of engineering at Titleist.
Two basic types of cover materials are used on golf balls — balata or an ionomer, such as Surlyn. Balata, once natural rubber but now a synthetic offering the same characteristics, compresses at impact, imparting great backspin on the ball. Spin rate is determined by the hardness of the cover relative to the core. Spin rates range from 2,000 (driver hitting hardcover) to over 10,000 rpm (nine-iron, softcover).
With a high spin rate, a ball tends to fly higher (longer carry) and land softer with more bite (less roll). It also will react more to sidespin. This is good for the expert intentionally drawing or fading the ball but can be a disaster for the duffer fighting a hook or slice. Thus, a ball with a relatively high spin rate is preferred by the better player, who generally emphasizes control over raw distance.
A durable ionomer, the most widely used type of cover material, resists cuts and abrasions better than balata. Its hardcover results in lower spin rates and permits increased compression (hardness) of a golf ball. The average golfer may prefer it to minimize a slice or to maximize roll distance.
X-rays and wind tunnels
Titleist’s wound or three-piece golf balls go through more than 80 different manufacturing steps and 32 inspections (including X-rays to make sure the centers are perfectly round) during its 30 days in production. Its two-piece balls require about half of these steps and can be produced in three to four days. Spalding lists 16 steps in manufacturing and can produce a ball in one day. This reduction in expense and time is another reason for the two-piece trend.
Titleist also tests balls in its own custom-designed, computerized wind tunnel to measure lift, drag, and ball movement under various wind conditions. This 6-ft-sq wind tunnel is similar to those used in aerospace but testing golf balls presented an additional problem, says Aoyoma, previously an aerospace engineer. “In aerospace, we would take a scale model of a plane and support it on some mechanism. The air would blow past it, and scales would measure the wind resistance. You can’t do that with a golf ball because it must be spinning in flight. In order to spin it, you have to put it on some kind of spindle, but the wind going around that spindle affects the air flow and you get a result that’s not realistic. The problem was: how do you spin the golf ball without supporting it?”
The solution was to position the golf ball between two cups, which get it spinning. The cups are then pulled apart and the ball drops through a hole into the wind tunnel. The ball spins about half a second, but that’s sufficient. A video camera records the ball path and with the help of a special computer program, researchers can figure the wind resistance and lift action.
Titleist also boasts an elaborate outdoor test range — a six-acre layout with three lush green, close-clipped fairways and a putting green. There, its “Iron Byron” is set up to hit with various clubs, at different speeds and striking angles. The shots are videotaped, and the distances and trajectories are plotted on a computer, with wind conditions figuring in the calculations.
Advice and astonishment
At the manufacturers’ test ranges, touring pros and other top golfers also hit balls and give their reactions and advice. “There are subjective things — such as how the ball feels when hit, and how they like the trajectory — that machines can’t tell us,” Aoyama explains.
The pros astonish the ball producers. “To me, it’s impossible that some golfers can do what they do,” Reid marvels. “We have had pro golfers here who are so good that you put a bushel basket out there at 260 yds, and they put half the shots in the basket on the fly. But what really disgusts me is the test where you measure where they hit on the clubface. A good pro can repeat the impact location to one-tenth of an inch or better, with a 43-in. shaft. I take a hammer with a 12-in. shaft and hit my thumb. The tells me that I am not going to be a golf pro.”
Reid is in charge of Titleist’s production engineering, which involves developing and building its ball-making machinery. Nearly all of this machinery, most of which is run by programmable controllers, had to be custom designed and built. However, Titleist (and Spalding) got at least one idea from the poultry industry — an egg-washing machine, which they converted to removing grit from golf balls after a pressure lasting.
What’s ahead for the golf ball industry? Customization. Golfers will be offered a greater choice of golf balls geared to their individual swing characteristics and club specifications — for example, four or five different types of trajectories might be available.
Meanwhile, producers continue to employ more and more space-age devices and materials to develop golf balls with even greater consistency and durability. Unfortunately, however, many of these high-tech wonders will be doomed to an extremely short life. One swing, one slice, into a lake or woods. Bye-bye.