Analysis Of Thermal Characteristics For CNC Machining Center Spindles

Thermal error is the main factor that affects the machining accuracy of CNC Machining Center, CNC Machining Center spindle is one of the biggest sources of heat, the size of the thermal error will directly affect the machining accuracy of CNC Machining Center. Therefore, analysis of thermodynamic characteristics for the spindle impact on machining error. It’s of great significance to improve the machining accuracy of CNC machining center.By means of ANSYS Workbench platform and using the finite element method study on CNC Machining Center of machine spindle and high speed motorized spindle. Spindle temperature field distribution and thermal deformation are analyzed changing with the processing parameters, the following research achievements.(1) Analyzing the characteristics of CNC machining center of motorized spindle and mechanical spindle of spindle structure, using ANSYS Workbench platform, establish three-dimensional geometric model of the spindle. On the basis of two kinds of main shaft driving part structure function, determines the heat source when the main shaft is working, and gives the relationship of local heat flow and main working parameters. According to the main shaft design structure, cooling mode and the work environment, determines the heat transfer coefficient and heat transfer boundary conditions of the main shaft components.(2) On the working process of the two types of spindle steady state thermal analysis and transient thermal analysis, it is concluded that the temperature field distribution characteristics of spindle assembly and changing with the time. Based on the relationship of spindle speed,bearing equivalent load and heat generating heat flux density, analyzed that the spindle rotational speed of spindle assembly affect the temperature field distribution, the results indicate:For machine spindle, the highest temperature appears that the rolling bearing is in front of the main shaft, the after rolling bearing temperature is much lower than the temperature of the before rolling bearing, but the case external surface’s temperature is uniform. Spindle each steady temperature were increased with the increase of rotational speed when the speed is not more than 5000 r/min, the rise of temperature of the bearing can’t more than 20℃, But with the increasing of spindle speed, the time of spindle assembly temperature distribution to stabilize is shorter. For motorized spindle, the highest temperature appears about built-in motor spindle rotor, before rolling bearing temperature slightly lower than the temperature of the motor rotor, and the difference case external surface’s temperature is smaller. The temperature of motorized spindle assembly increases with the increase of rotational speed, when the speed up to 15000 r/min, temperature rise of the highest temperature point temperature rise of up to 50℃, before rolling bearing of maximum temperature rise up to 40℃.(3) Through steady state and transient thermal analysis for two kinds of main shaft, thermal alteration characteristics of spindle assembly was studied. For machine spindle, axial and radial thermal deformation thermal deformation of the front shaft sleeve and the junction of box is larger. But the axial thermal deformation of the junction of box is the largest. The radial thermal deformation of the front shaft sleeve is the largest. The thermal deformation of axis is small. For motorized spindle, the axial and radial thermal deformation of the foe overhang spindle end, before rolling bearing and the junction of box is larger. But the axial thermal deformation of the foe overhang spindle end is the largest, The radial thermal deformation of the junction of box is the largest, the axial and radial thermal deformation of before rolling bearing is slightly smaller(4) Studied the influence law of the bearing pre-tightening force, back cutting depth, feed the influence law of temperature distribution and heat cutting on the spindle, the results indicate:Bearing pre-tightening force is an important factor that affects the spindle temperature rise, rolling bearing temperature rise along with the increment of pre-tightening force, especially the pre-tightening force up to a certain value, rolling bearing temperature rise will be raised; But back cutting depth, feed and cutting hot little impact on the temperature rise of the spindle component, can be ignored.