| Grinding wheel dresser is the common tool which can be used to dress the shape and dimension of grinding wheel.Its property will be of great significance to grinding quality.The dressing speed have been increasing,as grinding speed increases.High speed dressing has put forward higher requirements on the dynamic characteristic of grinding wheel dresser.Grinding wheel dresser is consisted of a diamond pen,a bracket,a workbench,a line guideway,a base,the rolling feed system and servo motor.The dynamic characteristic parameters of rolling feed system and the line guideway will have great influence on the dynamic characteristic of grinding wheel dresser due to its point\line contact features.Therefore,it will be of great scientific significance and engineering value to establish and analyze the dynamic model of grinding wheel dresser considering the coupling stiffness of joint.Dynamic characteristics research of 3MK2125 grinding wheel dresser is conducted,the content is as follows:(1)Establish the 3-dimension digital model of grinding wheel dresser for railway bearing grinder with the aid of Solidworks;establish the finite element model of grinding wheel dresser considering the coupling stiffness of joint with the aid of ANSYS;conduct dynamic characteristic analysis of grinding wheel dresser for railway bearing grinder and six lowest order modal parameters have been obtained,systematically compare the modal analysis result with result which is obtained by simplifying the joint as rigid body or line stiffness.(2)The 5-DOF static stiffness model of linear ball guide is established based on Hertz contact theory.The result suggests that:The stiffness of linear ball guide is slightly decreased with the rising of the applied load within working load;the effect of the vary of contact angle can't be neglected.The model considering the vary of contact angle is increased when compared to the model which defines contact angle as a constant.(3)The 5-DOF static stiffness model of linear roller guide is established based on slicing method.The result suggests that:The stiffness of linear ball guide is slightly decreased with the rising of the applied load within working load;when linear roller guide is subjected to pressure load,the distribution of stress of roller is symmetry and the stress achieves its maximum on the edge of roller;when linear roller guide is subjected to rotational load,the distribution of stress of roller is asymmetry and the contact stress achieves its peak on one edge of the roller.(4)The dynamic model of machine tool feed system which is driven by ball screw is established based on Hertz contact theory.The dynamic characteristics of feed system are analyzed characteristics of feed system and when nut is closer to mid part,the axial feed system stiffness is l.The dynamic characteristics of feed system fixed on both ends are superior to the feed system fixed at one end in the term of axial stiffness.The results of study suggests that the contact stiffness of rolling joint can not be neglected when conducting the dynamic characteristic of grinding wheel dresser.The lowest 6 order natural frequency of grinding wheel dresser for 3MK2125 railway bearing grinder is obtained by applying the joint 6 DOF stiffness proposed by this thesis into dynamic characteristic analysis:132.03 Hz,184.52 Hz,192.83 Hz,312.44 Hz,425.5Hz,518.52Hz;if the joint is simplified as rigid body,the lowest 6 order natural frequency is 132.03 Hz,192.84 Hz,513.39 Hz,555.83 Hz,662.67 Hz,827.13 Hz,the relative error is 0%,4.3%,62.4%,43.78%,35.79%,37.3%;if the effect of angular stiffness is neglected and simplify the joint as line stiffness,the lowest 6 order natural frequency is 132.03 Hz,183.8Hz,192.83 Hz,301.09 Hz,418.81 Hz,508.79 Hz,the relative error is 0.1%,0.39%,0.1%,3.78%,1.60%,1.91%. |
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