Grand slams such as the ATP World Tour Finals get through up to 70,000 tennis balls per tournament, so demand for new stock is always high. Wilson’s 11,000-square-metre factory, just outside Bangkok, makes 100 million of the green furry things every year, using a process that involves 24 intricate steps.
“The tennis ball is the most complex ball we make,” says Jason Collins, global product director at Wilson. “Because of the tightness of the specification – weight, size, hardness, rebound – the materials have to be super consistent.”
The factory uses a design that hasn’t changed much over the years due to strict specification from the International Tennis Federation. The main challenge it faces is producing a tennis ball with the perfect bounce.
If a ball becomes depressurised, or moisture in a clay court disrupts its felt, a player’s game could be thrown off – a potentially big problem if the player in question happens to be seeded.
1. Crushing
This rubber-based core compound made of materials including clay (which deadens rebound), is repeatedly crushed in an open mill for five minutes.
2. Compressing
Slugs are cut from the rubber-based core compound, which is then compression moulded for 90 seconds into a thin shell.
3. Sheeting
Once the slugs are compressed, a sheet is made. This is removed with an air gun, rolled up, left to cool and cut into semi-circular shells.
4. Buffing
The shell halves are combined to make ball cores and are buffed – placed in a sandpaper-lined cylinder to create grooves which aid adhesion.
5. Felting
An automatic cutting machine removes panels, or “dog bones”, out of a sheet of felt. They are then mechanically stuck to the core.
