The Design Of Subsection Double-lead Precision Indexing Worm Pair

With the development of mechanical equipment towards high precision,high efficiency and intelligence,higher requirements are put forward for mechanical transmission.As one of the most important transmission methods,worm drive is used in the precision indexing system of CNC machine tools.Among them,CNC indexable blade peripheral grinder is the most typical.According to the shape of the blade,the transmission system needs to repeat the forward and reverse rotation movement.In order to improve the machining efficiency and obtain high precision blades,it is necessary to eliminate the clearance between teeth in worm drive and improve the stability of movement.Firstly,the segmented double lead precision indexing worm gear pair is taken as the research object.According to the machining method and spatial meshing theory of worm gear,the spatial transmission coordinate system is established,and the tooth surface equation and contact line equation of worm gear pair are obtained.The structure characteristics of segmented double lead precision indexing worm gear pair are discussed,and the special structure parameter formula of the worm gear pair is designed.Secondly,the coincidence degree formula of worm gear pair is designed,and the influence of mechanism parameters of worm gear pair on it is studied.According to the structural characteristics and design requirements of worm gear pair,the optimization model is established,and the basic structural parameters of worm gear pair are obtained.The contact line model of worm gear pair is established.The contact line interference of worm gear pair under different pressure angle,different rotation angle and whether there is cross section is discussed.The value of worm tooth thickness reduction coefficient is 0.32.Then,according to the processing principle of worm gear and worm,the three-dimensional model of worm pair is established,the error visual positioning clamping device is designed,and the virtual assembly is carried out.Based on ADAMS software,the virtual prototype model is established to analyze the influence of the modification type of the incomplete tooth on the transmission stability of the worm pair,and the reasonable trimming angle of the incomplete tooth is obtained.The influence of different use error and structure error on the transmission stability of worm gear pair is analyzed.It is found that the use error of worm gear pair has greater influence on the transmission accuracy than the structure error.The wear of worm gear teeth in the use error has the greatest influence on the transmission accuracy,and the center distance error in the structure error has the greatest influence on the transmission accuracy.Finally,based on ANSYS The finite element model of worm gear pair is established by workbench software,the stress distribution of different worm gear teeth is analyzed,the stress distribution law is obtained,and the correctness of theoretical calculation is verified;the influence law of different structural errors on the stress of worm gear pair is analyzed as follows:the axial error has the most significant effect on the maximum stress peak of worm gear,followed by the radial error,and the minimum is the circumferential error.According to the stress distribution law of worm gear teeth and theoretical method,the fatigue life of worm gear pair is predicted to be 1.58E+06 times.