Development On Dynamic And Static-Pressure Spindle Units Of DJYM70 Multi-wire Screw Tap Grinding Machine Tool

For the multi-thread tap grinder therein,the form grinding wheel with multiple grinding line is adopted.With the grinding speed of 80m/s,the grinder realizes the efficient and precise grinding process of screw tap.Both the processing accuracy and productivity of the screw tap is at a high level.Spindle unit,as the key functional component of multi-thread tap grinder,can throw a direct influence on overall performance of the grinder;and the dynamic&static-pressure spindle unit is characterized by the high-level precision,profound stiffness,strong hold facility,etc.,thus can properly ensure the compliance of multi-thread tap grinder to the performance and precision requirements.Currently,80%of multi-thread tap grinder depends on the import.Consequently,the research and production of the dynamic&static-pressure spindle unit adopted for the multi-thread tap grinder can not only satisfy the rapidly increasing demand on multi-thread tap grinders in screw tap market,but also improve the overall technical level of those functional components on domestic dynamic&static-pressure spindle unit,forming an importance significance on promoting the international competitiveness of domestic high-end equipment manufacturing industry.This Paper analyzes the current situations of tap grinder and spindle unit,proposes the technical requirements on DJYM70 precision multi-thread tap grinder,demonstrates and confirms the overall schemes of dynamic&static-pressure spindle unit on the multi-thread tap grinder and the design schemes of dynamic&static-pressure sliding bearing.The telescoping structure is employed whole dynamic&static-pressure spindle unit with dual supports and thrust bearing combination at one end;further,the thrust end shall be arranged in front of the spindle unit.Based on the characteristics of dynamic&static-pressure sliding bearing,no unloading gear is installed on the spindle unit to reduce the transmission links and increase the transmission efficiency.The radial sliding bearing is structured into the even and opposed oil chamber with an equivalent area;thrust bearing is equipped with fan-shaped multi-oil chambers structure with constant pressure feed way and orifice type restriction.For sealing device,the method of gap non-contact seal is applied;and the dynamic&static-pressure spindle unit is treated with design calculations.The 38CrMoAl is employed as the spindle material,with carbonitriding technology and 0.4-0.5mm of thickness of nitride layer;and the tin bronze ZQSn-6-6-3 with higher wearing coefficient is adopted to the bearing bushes of front and back bearing.In the design,the main journal and optimal supporting span has been calculated,as well as the orifice diameter of orifice type restriction,fuel supply pressure and minimal radial clearance of the sliding bearing.Additionally,the Paper has also checked the stiffness of grinding wheel on the spindle unit,as well as the radial and axial stiffness of the bearing.With the application of#2 spindle oil,it has been calculated that temperature rise of the spindle unit under the rotating speed is 17.3 ?,thus meeting the temperature rise requirements.It has analyzed the processing technology of those major parts on DJYM70 dynamic&static-pressure spindle unit,described safeguard measures of processing quality in bearing inner hole and inner chamber,chamber bearing hole,spindle,match grinding of sleeve excircle.Besides,the Paper has researched the assembly technology of spindle unit,proposed the specific solutions to mounting difficulty,incurred in the assembly of spindle unit,instable axial dimension of adjustable pad,inflexible spindle rotation after assembly completion and other problems,and debugged the operation of assembled dynamic&static-pressure spindle unit.Further,it has conducted the bench test to the dynamic&static-pressure spindle unit on DJYM70 precision multi-thread tap grinder,and actually measured the rotation precision of spindle unit,axial movement,axial stiffness,radial stiffness,spindle vibration,bearing temperature rise and other main performance indexes.According to the test result,the dynamic&static-pressure spindle unit meet the design requirements.