One of the first operations in the technology of post-harvest processing of a combine heap is preliminary cleaning, which makes it possible to increase the flowability of the material and reduce the cost of drying. In the farms of the North-Western region of the Russian Federation, the grain heap coming from the fields to the processing lines of grain-cleaning and drying complexes is characterized by increased grain mass contamination (15 ... 20%) and a multicomponent composition of trash, which, along with an increase in the moisture content of the grain heap, has a negative effect on the efficiency of the pre-cleaning machines. At grain cleaning and drying points, machines of various designs are used for preliminary grain cleaning. In most cases, they are not intended for separating small weed fractions and separating feed grain, when cleaning a heap with a moisture content of 26 ... 30% or more, their productivity decreases 1.5 ... 2 times. As a result, the wellness of the grain mass is sharply reduced, which in turn reduces the efficiency of storage bins, dryers, as well as machines for primary and secondary grain cleaning. Fundamentally new approaches to the development of designs for grain pre-cleaning machines are required. They must have a high productivity for the coordinated and efficient operation of the entire technological line, as well as carry out preliminary cleaning of grain with its simultaneous separation into feed and seed fractions. Heap cleaners are needed that are capable of separating clean forage from the grain heap already at the first operation, so that it does not need to be additionally cleaned of large weeds and sand, but only needs to be dried on a separate technological line. The pre-cleaner must have a developed air-sieve system and have perfect under-sowing sieves to separate small weed seeds