When clothing is washed or worn, it constantly rubs against the outside or itself, so that the fiber ends on the surface of the fabric yarn are taken away from the bondage of the yarn by the friction force, and the yarn is untwisted and exposed on the surface of the fabric, forming a surface on the surface of the fabric. This process is called "fluffing". If these piles cannot fall off the fabric in time, they will be entangled with each other and kneaded into spherical particles. This process is called "pilling".
Judging from the quotation of the standard, the domestic woven garment industry basically uses the circular trajectory method such as GB/T4802.1, the American customers basically use the Martindale method such as ASTM D4970, and the Japanese customers mostly use the pilling box method such as JIS L 1076A method.