Influence of elastic deformations of a non-rigid box blanks, limited by the fixture design, on the accuracy of machined surfaces

Abstract

An analysis is given of the forced alignment of inaccurate base surfaces of the workpiece with the exact base surfaces of the fixture by applying a distributed load to it with the help of rigid fixture elements that have the correct geometric shape. As a rigid element, a prismatic insert with cutouts on the upper and lower surfaces is used, which is installed inside the box-shaped housing made of sheet 1.5 GOST 19904-90 made of 30XGSA steel. It is shown that this eliminates the uncertainty of basing, which creates the prerequisites for increasing the accuracy of machining and increases the rigidity of the fixed workpiece, which helps to reduce vibrations and improve the quality of the machined surface. It has been established that there is an optimal width of the insert cutout on the base-clamping surface, at which the elastic deformations of the base surface of the workpiece are within acceptable limits. The rational value of the liner cutout width should be either less than 55 mm or more than 70 mm. Such fastening causes additional errors in the position of the side surfaces of the housing, which are the measuring bases for milled surfaces and drilled holes. In the work, their numerical evaluation was carried out, which showed that the elastic displacements of the surfaces, which are the measuring bases, are within acceptable limits. It has been established that if the workpiece was sent to a fixed mounting base using an adjustable bracket and fixed without applying clamping forces, then in this case a more uniform and smaller (about 0.01-0.08 mm) elastic deformation of the side walls of the workpiece occurs, than when fixing with a force (about 0.02-0.20 mm.).