Development And Precision Control Method Of Mechanical Spindle Unit Of BT50 Machining Center

Machining center spindle unit is the main component of NC machine tool,and its accuracy directly affects the accuracy of the whole machine tool.Only by improving the accuracy of the spindle unit of the machining center can the accuracy of the whole machine tool be improved.Firstly,the research status of spindle unit is analyzed.According to the actual needs of actual manufacturers,the design subject of high-speed,high-precision,high-torque mechanical spindle unit is put forward.The research contents are as follows:(1)Determine the overall structure scheme of the mechanical spindle unit of BT50 machining center.Through demonstration and comparison,it is proposed that BT50 should be designed as the mechanical spindle unit of the machining center;through demonstration,the transmission mode of the spindle unit of the machining center is the structure of synchronous belt pulley and motor connection;the bearing configuration and support mode of the spindle unit should be selected according to the high rigidity requirement of the spindle;the taper shank and tool tension mechanism of the spindle are given;and the sealing and lubricating mode are also given,so as to be sure.The overall structure scheme of the mechanical spindle unit of BT50 machining center is determined.(2)Finite element analysis and manufacturing process analysis are carried out for the structure of the spindle unit.The diameter of the spindle unit of BT50 machining center is designed and calculated.The three-bearing structure of the spindle unit is reasonably analyzed by using finite element analysis software.The corresponding deformation of the front end of the spindle is obtained by analyzing different bearing spans,and then the structural dimensions suitable for the high steel of the spindle unit are determined.At the same time,the finite element method is used to analyze the structure of the spindleelement and the stress of the three-support spindle.The processing technology of main parts of BT50 mechanical spindle unit is analyzed.The processing difficulties of key parts such as spindle and sleeve are analyzed.The corresponding solving measures are put forward according to the processing difficulties.In the process of spindle processing,the method of benchmark interchange is adopted to eliminate the errors in processing.At the same time,in the process of spindle processing,the traditional tail cone hole positioning is changed to the 60 degree positioning of the hole orifice,which improves the processing accuracy and saves the cost.In hole processing,CNC drilling machine is used to process the through hole of spindle unit,and the deviation between the hole and the outer circle is eliminated by 60 degree top hole opening.The inner hole of the spindle is refined by using the outer circle of the finish turning as the reference,and the deviation of the center between the outer circle and the inner hole of the spindle is eliminated by the conversion of the reference.The assembly process of the spindle unit is analyzed in detail,and the existing problems in the assembly process are analyzed.Different experiments are used to verify that the spindle unit is qualified.Running-in experiments are carried out after the assembly of the spindle unit is completed,and the related comprehensive performance tests of the spindle can be carried out only after the test is qualified.The factors affecting the accuracy and the deterioration of the spindle unit are analyzed to prepare for the test.(3)The spindle element is tested and studied by experiments on its rotational accuracy and stiffness.The testing principle and testing method of the spindle rotation accuracy test-bed are analyzed,and the mechanical spindle unit is tested.Standard sphere detection method is used to test the rotation accuracy of spindle unit.In the process of testing,single-point measurement and two-point vertical measurement are used.The rotation accuracy of the spindle unit is tested,and the spindle values at various speeds are recorded to verify the spindle unit’s rotation accuracy is qualified.Radial stiffness and axial stiffness of the spindle element were tested on a stiffiness test rig.The stiffness of the spindle element is verified by loading experiments on groups of spindle elements and recording the axial and radial movement of the spindle element under different loading forces.According to the loading requirements of the axial force and the radial force,four different forces are applied to each group of loading forces from low to high,and the deformation of the spindle unit is recorded separately.To verify whether the axial and radial stiffness of the spindle meets the design requirements.Experiments show that the performance of the spindle unit fully meets the requirements of design and use.