Abstract. An air screen cleaning machine has been developed for the fractional technology of forage grain flattening with a new implementation of the elements of the screen part and a pneumatic system, allowing efficient separation of the grain material coming from the field after threshing by combine harvesters into fractions of the seed and the forage grain, and their qualitative cleaning from admixtures. There is presented a design and technological scheme of this machine, as well as its pneumatic system in the form of a pneumatic circuit. Research of the pneumatic system has been carried out by mathematical simulation, which makes it possible to theoretically test its operability and conduct analysis of the dynamic processes that occur in separate elements. By using the results of these studies, a possibility appears to design and then to make a test sample of the machine with the parameters of the working tools (the pneumatic system), which ensures a qualitative cleaning process from the admixtures of the grain fractions.Keywords: technology, fractionation, grain flattening, admixtures. IntroductionForage grain is valuable concentrated feed for animals, a source of carbohydrates, protein and other useful nutrients, and it is widely used in animal husbandry. To improve digestibility of its components, forage grain is subject to special processing, or grinding. One of the most economical ways of grain processing is flattening [1], which has a number of advantages in comparison with crushing [2-4], since it ensures the production of fodder best corresponding to the biochemical processes that occur in the stomach of the ruminant animal [5]. Despite the fact that grain flattening has been used for more than a hundred years, the machines for this process are constantly being improved in terms of the quality of the process performed, minimisation of the energy costs, etc.Analysis of the scientific, technical and patent literature on the existing technologies and technical means of the post-harvest handling and processing of grain forage [6][7][8] shows that one of the most promising and economically profitable technologies is the fractional technology of forage grain flattening. In order to isolate the forage grain fraction (which is then subject to flattening) from the grain that is arriving after threshing by the combine harvesters on the field into the post-harvest processing centres, an air screen cleaning machine in a new design of the elements of the screen part and the pneumatic system has been developed allowing not only efficient fractionation of the not yet treated grain into the seed grain and forage, but also qualitative separation of these fractions from admixtures.For this purpose the most perfect is the air-screen grain cleaning machine, intended for processing the grain material both in the usual mode (separation of grain from small, big and light admixtures), and in the fractionation mode (separation of the grain material into fractions with simultaneous cleaning of the grain fractions from admixt...