Analysis And Simulation On Meshing Characteristics Of Globoidal Indexing Cam Mechanism

Globoidal indexing cam mechanism is one of indexing or stepping transmission mechanism which was used in two vertically staggered shafts. It is widely used in various automatic machines because of the characteristics such as high speed, high precision, heavy load, good reliability, long life, etc. Its indexing speed can reach 2000r/min and positioning accuracy can reach±5″～±15″. It has gradually replaced the geneva, ratcheting and intermittent gear, and become a development direction of intermittent indexing and stepping mechanism.This paper taking the point contact globoidal indexing cam mechanism as research object, aiming to the improvement of its precision and stability. There by means of some basic theory such as differential geometry, meshing theory, point contact, elasticity, etc., using computer software as programming,3D modeling, finite element analysis, etc., conducting research on basic theory, meshing characteristics, dynamics characteristics of point contact globoidal indexing cam mechanism.(1) Based on differential geometry theory and rotary transform tensor method, according to the conjugate principle of spatial envelope surface, the general mathematical model of spatial cam mechanism and globoidal indexing cam mechanism are obtained, and then the unified surface equation of various roller are derived; and the contour surface equation of globoidal indexing cam mechanism with conical roller is obtained.(2) Based on the general profile equation of globoidal indexing cam mechanism, the parametric dialog box of cam surface is designed and programmed by programming software VB, its spatial surface and solid model and 3D parametric model database of the sphere-conical roller are established through 3D modeling software Pro/E, then the assembly model and kinematics simulation are completed.(3) The cam pressure angle is analyzed and calculated through MATLAB, the variation curves are obtained, and its change laws and effects on meshing performance are discussed under the different roller structure parameters; the curvature analysis method of globoidal indexing cam mechanism with conical roller and sphere-conical roller are given. (4) The modal and harmonic response analysis of globoidal indexing cam and indexing rotary table are carried out by ANSYS,and first six nature frequencies and modes and harmonic analysis curves are given, which establish a good foundation for the direct analysis of dynamic characteristics and deformation conditions;(5) The elastic contact problems of point contact globoidal indexing cam mechanism are analyzed by Hertz elastic contiguity theory; based on finite element method, the point contact problem is modeled and analyzed by Pro/E and ANSYS. Through ANSYS contact analysis, which have many groups of contact finite element model of point contact globoidal indexing cam mechanism, their elastic point-meshing characteristics and influence laws with the change of roller radius, roller cone angle and meshing positions are discussed, including displacement, stress, strain, deformation area and contact press because of contact deformation, which provide theoretical basis for design and manufacture globoidal indexing cam mechanism with high reliability and precision.