Formation of geometrical characteristics of short holes in the longitudinal section during honing

The use of honing when finishing holes for cylinder-piston systems makes it possible to ensure high geometric accuracy of the treated surfaces and to form a microrelief in the form of transverse scratches, ensuring retention and circulation of oil during operation. The main output parameters of the honing process, characterized by the accuracy of the geometric shape and the roughness of the machined surface, as well as the processing productivity and durability of the bars, depend on a combination of technological, kinematic, power and scale-geometric factors. As an analysis of published research results has shown, the choice of honing process parameters to ensure the accuracy of the geometric shape of the hole in the longitudinal section is based on empirical methods obtained for specific honing conditions and cannot be used in other conditions without the necessary theoretical justification. In this regard, a model was developed for the formation of errors in the geometric shape of short holes in the longitudinal section during honing according to a processing scheme with overlapping processing zones along the length of the hole, built on the basis of scale-geometric factors, including the ratio of the dimensions of the honing stone, the length of the hole, the stroke of the honing head, as well as the ratio of the speeds of translational and rotational movements and force influence in the processing zone. To obtain analytical dependencies that evaluate deviations of the geometric shape, the conditions for metal removal were considered, the value of which was taken to be proportional to the movement of individual points of the bar relative to the selected point of the treated surface and the pressure value. For this purpose, graphs of the distribution functions of displacements and pressure changes were constructed depending on the coordinate of the location of the point on the generatrix of the hole being machined. The obtained analytical dependencies confirmed the potential appearance of a shape error in the form of barrel-shape, and made it possible to evaluate the influence of the length of the honing stones, the amount of overtravel and the ratio of translational and rotational speeds on their value.