Before 1965 tennis rackets were constructed strictly from wood materials. In 1968, the Spalding company was the first company to market aluminum tennis rackets. The change in design allowed for a broader head. In 1981, The International Tennis Federation adopted rules defining acceptable tennis rackets for the use in the sport tennis. Tennis rackets sold in the United States are mass produced at one of several large factories in Japan or elsewhere in Asia.
Since then the manufacturing of tennis rackets have exploded worldwide, and are being mass produced in Japan or elsewhere in Asia. Raw material costs are cheaper which in return has allowed for manufacturers to produce tennis rackets that are poorer quality and that don't meet International Standards. Tennis rackets are made up of different types of alloys. A very popular alloy used in China contains 2% silicon, magnesium,chromium, and copper. Other materials found in tennis rackets are nylon for the strings on the top of the tennis racket, and leather or another type of synthetic material which is used for the handle.
QC of tennis rackets includes inspection at several different times during the manufacturing process. A visual tennis racket inspection is performed when the tennis racket frames are being removed from the molds. Tennis rackets that pass inspection are then graded for quality. Passing rackets will be graded for quality. Aluminum tennis rackets are then tested with a stress test to determine the strength of the tennis racket frame and ensure it meets international standards.
A very important step in the tennis racket inspection and quality control process is for QC auditors to check the balance and the weight of the tennis racket. Inspectors will weigh the tennis racket before and after the racket has been set up with the nylon strings. The tennis racket cannot be heavy at the head or in the handle. Then the racket is weighed after it has been set up with strings. This step is crucial to test how well the tennis racket will play. The grommet holes are then inspected along with a final visual inspection for defects or rough edges. New tennis racket designs will usually be play-tested as well to ensure the design is efficient and meets International Standards.