Evaluation of quality parameters of the torque transmission connections of the multi-purpose machine spindle joints

Abstract

The article presents the results of theoretical studies of a multi-purpose machine when assembling an HSK spindle-mandrel connection for accuracy, contact stiffness and strength. Studies were based on the developed original mathematical program complex for assessing the quality parameters of machine connections. They have been carried out with respect to HSK spindle-mandrel connections under conditions of multiple tool changes. Simulation of the coupling of connection parts for different values of the fastening (assembly) forces showed that HSK-type connections have a static uncertainty of basing under external loading conditions. Analysis of the stress-strain state of the connection joints was based on the finite element method when using software in the FEMAP 11.1 with NX NASTRAN. It showed that an unorganized change of bases occurs under the influence of external conditional load. It has been established that for tool mandrels of the HSK-63 type with a fixing force of 900 to 23000 N, the elastic displacements at the end of the mandrel vary from 1.5 to 0.6 μm under the condition of an external conditional load of 1732 N and, accordingly, from 8.0 to 2.5 μm with an external load of 6070 N. It was established that with a limiting value of the mandrel clamping force equal to 23000 N under conditions of external loading an unorganized change of bases occurs, namely: the end faces of the contact of the tool mandrel and the spindle are pressed, which reduces the geometric accuracy of a multi-purpose machine with a CNC.