HYDROSTATIC SPINDLE FOR ULTRA-PRECISION TWO-SIDED MACHINING
Authors: Fedorynenko Dmytro , Sapon Serhii 
Published: August 2019

Urgency of the research. Modern development of mechanical engineering creates constantly increasing demands concerning maintenance of quality indicators of detail processing. So, indicator of roughness, admissions of linear sizes and angular are decreased constantly. Application of precision machine tools is an effective way of decision of the tasks in view.
Target setting. Today ultra-precision processing of materials is widely used for manufacture of electronic components of techniques, telecommunication, medical, automobile, optical equipment. Therefore, the designing of ultra-precision machine tools is an urgent task for ensuring the high efficiency of the processes of machining.
Actual scientific researches and issues analysis. Basic component of precision machine tool which defines quality of machining is a spindle. Quality indicators of a spindle are mostly provided with a correct choice of type and design of its bearings. It is showed that hydrostatic bearings together with increase of machining reliability and productivity allow providing of exclusively high indicators of detail machining quality compared with other types of spindle bearings. Besides, they are the most perspective type of spindle bearings for realization of high-speed machining and ultra-precision machining.
However hydrostatic bearings are characterized by relatively big power losses on friction and, as a consequence, vigorous heating at increased rotational frequencies. Therefore lubrication of hydrostatic bearings with low viscous liquids, in particular water, presents separate interest.
Uninvestigated parts of general matters defining are designing of new design of a spindle with combined hydrostatic bearing based on special water lubrication for increased precision and efficiency of two-sided ultra-precision machining.
The research objective of this article is designing of new design of a spindle unit with direct drive, clamping fixture and combined hydrostatic bearing, which based on special water lubrication, for increased precision and efficiency of two-sided ultra-precision machining.
The statement of basic materials. New design of a spindle with combined hydrostatic bearing based on special water lubrication and clamping fixture is proposed for increased precision and efficiency of two-sided ultra-precision machining. The design of this precision spindle with direct drive by hollow-shaft torque motor provides two-sided machining of disk-shaped workpieces. The regularities of the formation of stiffness, flow rate and power losses in the combined spindle bearing, depending on viscosity of the working fluid, clearances in the journal and thrust bearings, pump pressure, and size of the bearing lands are defined. As a result of mathematical and CFD modeling rational parameters of combined spindle bearing were identified that provide minimum power losses at operation at simultaneous insuring of the high accuracy of a spindle. For increase of accuracy of clamping advanced design of the clamping fixture with a screw clamping of workpieces on the basis of use of PVC paste as pressure-transmitting environment is offered. The article introduce the use of water lubrication as an effective way of solving issues of increase concerning spindle unit efficiency, the reduction of operating costs due to simultaneous cooling of bearings and spindle drive, and also the increase of environmental friendliness of the design as a whole.
Conclusions. The new design of a spindle unit for two-sided ultra-precision machining with direct drive and clamping device was presented in this article. The main advantage of this solution is the compact structure of the spindle. The direct drive of the spindle with hollow-shaft torque motor can effectively be used for two-sided ultra-precision end turning of the workpieces.
The regularities of the flatness deviation formation of the end surface of the workpiece during clamping are established. It is shown that clamping forces acting on the workpiece do not have a significant impact on accuracy of the surfaces machined. The
rational geometrical and operational parameters of the clamping for maintenance of high operational reliability are received.