The cleaning machines with different principles focus on the impurities or functions removed during seed processing. There are more principles and types of cleaning machines, so you should be careful when purchasing. The general principles are as follows.

　　(1) If it is obviously lighter than good seeds in weight, and the size is obviously different from that of good seeds, we should first choose a wind screen type cleaning machine. This machine is widely used at present.

　　(2) When there are obvious differences in the length and size of the cleaning, and there are still long impurities or short impurities that cannot be completely cleaned after the air screening processing, the socket type cleaner should be selected for trial.