Improving the existing designs of screw conveyors can significantly increase productivity and expand the functionality of transport mechanisms, which leads to further development of production. One of the reserves to increase the functionality of screw transport mechanisms is to improve the transportation process by developing combined screw working bodies that will ensure the simultaneous movement and grinding of materials. The objestive of the work is to refine the mathematical model of productivity of the improved screw conveyor basing on coordination of supply of root crops from the loading channel to the auger and complex geometrical factor of filling the working space of a trench. The developed refined mathematical model allows to determine at the highest level the real productivity of simultaneous transportation and grinding of root crops on a separate technological unit, which is installed, for example, in the line of preparation and processing of root crops for biofuels. This allows to optimize the parameters and modes of operation of the entire processing complex at a practical level and ensure its estimated productivity of the manufacturing process.