Some Specific Features of Bearing Unit Development Based on Sliding Friction Pairs for Precision Electro-Spindles

Abstract

Various types of bearing units are used for movable connections in mechanical engineering, and sliding pairs (sliding bearings, guides, bushings) are rather widely applied for this purpose. This allows increasing stiffness of units to reduce their dimensions, to improve heat dissipation and ensure reduction in noise and vibration. However in some cases while using a sliding friction pair higher friction losses occur in comparison with ball bearings and probability is increasing for situations when there is a jamming of friction surfaces. These problems have great significance for application of sliding bearings in precision equipment, which typically operates under stabilized temperature and humidity conditions. So an aim of the investigations is to develop methodological approaches for creation and rational design and manufacture of sliding friction pairs based on application of coatings formed of composite antifriction materials which are used in vertical precision program-controlled electro-spindles for high-speed machining. The paper considers issues pertaining to development and creation of friction units for precision electro-spindles of high rigidity with sliding friction pairs on the basis of composite materials. Diameters of sliding bearings can be rather large that makes it possible to obtain the required super-high accuracy in mechanical processing and nanometric roughness of the machined surface. A cutting speed (750 m/min or more) which is acceptable with regard to quality of machining by a diamond-like tool can be achieved by placing a cutting edge of the tool on diameter of 200 mm. Such approach permits to use lubricated sliding bearings in the spindle design. As a result, two tasks can be solved in an integrated manner. They include the required rigidity of an electrospindle for ultra-high accuracy of mechanical blade processing and high smoothness of the machined surface providing nanometric surface roughness with a decrease of macrodeviations up to 1 μm from a middle surface line. It is worth to note that this is extremely important for a number of special applications