How do you use mathematical equations to figure out how large the sieve is and what size it is to sieve out?
Your raw material (coarse aggregate) is too thin, most of which is lower than 20mm, so in the mixture you find more than 20mm of the material is very small. Raw material is not qualified.
Check that the overflow bin is overflowing, and if so, prove that your raw material (coarse aggregate) is non-circular in shape and block the screen, so you need to clean the screen.
This is related to the sieve margin, larger than 21# discharge, less than equal to the product, through the screen, that is, the screen under the screen, the margin is based on the amount of feed and sieve on the percentage of the material to be calculated, the method is not.