The process for manufacturing a tennis ball has not changed in over 100 years, but the tennis ball inspection process continues to advance with modern technology. Tennis balls were historically manufactured in Europe and USA until recently when the need to have lower labor costs, and cheaper raw materials shifted manufacturing to the Far East.
Key points for QC inspection of tennis balls:
Removing "Set"
Tennis balls are pre-compressed before any testing to remove any “set” in the tennis ball. Set is a property that occurs in materials when they are not subjected to force. This may occur to tennis balls between the time they have been packaged and the time they are opened for testing. The pre-compression machine compresses tennis balls 2.54 cm three repetitions from three different directions using a pneumatic actuators.
Acclimatization and Decompression
Before testing, the balls are acclimatised for 24 hours in a climate controlled laboratory. The lab operates at an average temperature of 20 degrees Celsius and the humidity set at 60%. Studies have proven that temperature and humidity affect tennis ball properties. High humidity can decrease tennis ball bound height and high temperatures can increase tennis ball bound height.
Deformation Testing
One of the tests performed is the deformation test. To perform this test, you will need to use a mechanical device which applies force to a tennis ball placed between two pieces of steel. The technician compresses the tennis ball by turning a handle on the mechanical device. The amount of deformation under a force is then measured by a scale.
Rebound Testing
A rebound test is also performed in the inspection process which did involve dropping a tennis ball vertically from the height of 100'' and then measuring the rebound. The rebound range should be between 53 - 58in. Equipment used in laboratories consist of a vacuum pipe that holds the tennis ball at the specified height. then it is released onto a smooth, granite block. The tennis ball bounces and a camera records the height of the bounce. This video will then be analyzed to view the bounce in real time and then an accurate calculation of the height will be provided.
Color Observation
In the rules of tennis it specifies that a tennis ball has to be the color white or yellow, so quality control specialists in the Far East access the color of tennis ball's using a tool called the spectrophotometer. The spectrophotometer records the color of each ball on the scale called L.A.B. This scale specifies color on a 3D level. The letter L represent lightness, the letter A represents
redness-greenness and the letter B represents yellowness-blueness.
If importing tennis balls from China then performing testing and inspection prior to shipment is critical. Let InTouch Quality's experienced staff create a tennis ball inspection procedure for you.
