BALANCING SPINDLES WITH TOOLS FOR FINISHING AND BORING MACHINES

Abstract

Finishing and boring machines are used in serial and mass production for processing parts of various shapes and deformation properties, namely liners, connecting rods, pistons, flanges, couplings, as well as body parts such as crankcases, blocks, cylinders, etc. Bridges are installed on the bed of horizontal boring machines, on which spindle units are fixed. The decisive influence on the accuracy of processing is exerted by the parameters of the spindle assembly with the tool and the fixture with the part. The use of modern tool materials makes it necessary to increase the speed of spindle units up to 8...10 thousand rpm when machining holes with a diameter of 16...40 mm. The paper investigates the anisotropy of the rigidity of the elastic system of the machine tool, which leads to deviations from the specified depth of cut under the action of forces rotating together with the cutter. In experiments, the influence of the anisotropy of radial compliance on the processing errors was studied. The dependence of the determination of additional centrifugal force, which provides a minimum of deviations from roundness, is obtained. To ensure a minimum deviation from roundness, the developed technique allows you to perform only three borings. Note that the fulfillment of the requirements for the shape of the cross section in the absence of imbalance is established after the first boring. According to the developed method, the values of centrifugal forces are assigned, given by the mass of the load fixed on the flange of the boring bar or on the pulley. The measured values of deviations from the roundness and roughness of the surfaces of the machined holes confirm the calculated estimates. It has been established that only for heads of the first size (universal diamond-boring UDB-1) the maximum unbalance is close in order of magnitude to the allowable one. Therefore, spindle balancing should be carried out for heads designed to operate at speeds close to the maximum.