Since May, Wilson has been hard at work creating 98,000 balls for this year's US Open in their factories near Bangkok. Each ball goes through 24 production steps from start to finish before being sent out to the tournament in New York. Here's how it's done.
The half shells are pressurized to 18 psi, then the press is brought together until the halves are a quarter-inch apart and the half shells are bonded to make the core of the ball. This process cures 144 balls at a time and takes about 10 minutes: a five-minute heat cycle followed by three minutes of cooling, with a couple of minutes for loading and unloading.
The newly bonded shells (called "cores" by Wilson at this point) are placed in a cylindrical buffing machine, a sandpaper-lined tube where the outside of the core is roughed up in preparation for adhesive application. These are the abraded cores that have come out of the buffing machine after spending six to seven minutes in it.
This machine holds 225 cores, and the coating process takes about five minutes. The pictured cores are shiny because the adhesive is still wet. The coated cores are dumped out of the tumbling machine, and a worker, pictured, evenly distributes the coated cores. He puts one core through every hole in the screen, directing them into alignment with the tray below.
This is the automatic cutting machine, which cuts the felt into panels that Wilson employees call "dog bones" because of their shape. The machine makes 25 dog bones a minute, and they are piled 70 strips high. Yellow, white and orange are the only colors approved for tennis balls.
Tennis ball orientation
Here, the worker is orienting the balls inside of the third cure press, which hold 121 balls at once. The cycle is similar to the second cure: a five-minute heat cycle followed by three to four minutes of cooling. After this curing, the felt on the ball is fluffed (not pictured). During fluffing, the felt is brought back to its original thickness by putting several thousand balls at a time into a giant industrial laundry machine, in which the balls are tumbled around with steam and agitated.
The machine is flipping the can 180 degrees. The cans come up in the correct orientation but are then flipped upside-down for label application. Once the label is applied to the can, the can is spun around and goes through a heat tunnel, which shrinks the label onto the can.