The study was carried out in order to substantiate the development of a combination of sieves for the combine harvester cleaning system. Methodically, the research is based on the general logical method and mathematical analysis. In the course of the study, formation of the separation process of the grain heap in the cleaning system of the combine was shown. At the same time, the relationship between regularities characterizing changes in the technical and operational parameters of the combine and technological properties of grain crops is considered. The relationship between the supply of the grain heap to the cleaning system of the harvester and technological parameters of the grain heap and technical and operational parameters of the machine is revealed. A graphical interpretation of the obtained regularities characterizing changes in the height of the grain heap layer on the sieve for cleaning the combine from the technological properties of grain crops and other parameters of the combine harvester is presented. © 2022 American Institute of Physics Inc.. All rights reserved.