In the field of cleaning, when the surface of the workpiece is to be cleaned by steel shot blasting or spraying, pits are formed on the cleaned surface. Only when the pits overlap, the entire surface can be completely cleaned. If the particle size of the steel shot is too uniform, it will take longer for the pits to overlap. For steel shots with a certain particle size mixing ratio, the large steel shot will clean the large particles, and the small steel shot will clean the large particles. The steel shots form gaps, which greatly shortens the shot blasting time and improves the blasting surface quality and production efficiency. It is precisely because of the difference in roundness between steel shots that the best effect can be achieved when they are used together. Therefore, the more uniform the particle size of the steel shots, the better.