The use of a mathematical model of discrete motion of bulk material were justified for movement of polymer granules in the working channel of feeding zone of the screw extruder as a set of particles moving relative to each other based on the Discrete Element Method taking into account the influence of the shape and the size of polymer granules on their tribological properties on the example of the problem of forming the angle of repose. The study of the interaction among the granules of the following four polymers has been conducted: high-density polyethylene of brand Marlex HHM 5502BN (HDPE), copolymer of ethylene with vinyl acetate (sevilene) of brand 11104-030 (CEV), polystyrene of brand Denka Styrol MW-1-301 (PS), polyvinyl chloride of brand SorVyl G 2171/9005 11/01 (PVC), which are selected because they are widely used in industry and at the same time differ from each other in shape, size and physical and mechanical characteristics. The Hertz-Mindlin viscoelastic model was used to describe the interaction between granules, which assumes that the sphere-shaped particles do not deform upon contact and overlap each other by a predetermined amount, forming a contact patch. The study was carried out in the EDEM software package. The calculation results for the formation of an angle of repose of natural methods and numerical experiment were given with the two approaches to modeling the shape of pellets were analyzed: the consideration in the form of granules in the form of spheres and in the form of multisphere, when the calculated shape of the pellets as close to real. The results of the calculations on the formation of the angle of repose prove that the discrete motion model of bulk material based on the discrete element method when using the form of granules close to real better reproduces the behavior of bulk materials compared to spherical granules