RESEARCH AND DEVELOP A METHOD AND AN EQUIPMENT SYSTEM TO EVALUATE THE SPINDLE UNIT STIFFNESS OF AN EXTERNAL CIRCULAR GRINDING MACHINE BASING ON REPLACING HYDRODYNAMIC LUBRICATION WITH HYDROSTATIC LUBRICATION

Abstract

The spindle unit of machine tools in general and external circular grinding machines in particular is a very
important part, it determines the cutting productivity as well as the surface quality of the workpiece.
Hydrodynamic lubrication is used for the spindle unit of circular grinding machines including the 3K12 grinding
machine. However, due to the characteristics of hydrodynamic lubrication, the spindle center trajectory changes
depending on the speed and the applied load, which affects the stabilization of the spindle center and
enhancement of the machining accuracy of the workpiece. Currently, hydrostatic lubrication can be considered as
a solution to improve the working quality of the spindle unit of the external grinding machine instead of using a
hydrodynamic lubrication. One of the criteria to evaluate the quality of the external circular grinding machine
spindle using hydrostatic lubrication is the stiffness. This paper presents the research results and development of
a method and an equipment system for measuring the spindle unit stiffness of the medium-sized grinding
machine basing on replacing hydrodynamic lubrication with hydrostatic lubrication.