Research On Cam Mechanism Characteristics Of Gear Rack Type Planetary Indexing

As a common intermittent motion mechanism, the indexing cam mechanism hasbeen widely used in the automatic machinery of machine, electronics and printingindustry, etc. However, a flaw that the input shaft can realize only one dividingmovement by rotating once exists in the traditional indexing cam mechanism. Withcoaxial layout and compact structure, one-dwell coaxial planetary indexing cammechanism combines the advantages of one-dwell coaxial indexing cam mechanismand planetary indexing cam mechanism, which overcomes the limitation of traditionalindexing cam mechanism that can only output in a way of whole circle, to realize thetransmission of large indexing number.This paper studies one of the structures of one-dwell coaxial planetary indexingcam mechanism-planetary indexing cam to intensively investigate its form,transmission principle, profile equation, modal analysis and mechanism dynamicsinvolving clearance. The following were completed during the study:This paper researches the structure and transmission principle of planetaryindexing cam of pinion and rack, describes its profile equation and establishes thetheoretical and practical profile equation. The profile equation was generated byMatlab Programming and was verified through motion simulation to complete the3Dmodeling in Solidworks.Two basic elements-pressure angle and radius of curvature affecting thegeometrical feature of cam were analyzed based on the parameters of planetaryindexing cam of pinion and rack. The law of how the basic parameters impact thepressure angle and radius of curvature was also studied.Focusing on the feature that modal analysis of cam mechanism assembly isnonlinear, a measure to calculate the modal range under critical state was put forwardand the natural frequency and vibration model were obtained to provide basis forreducing vibration and optimizing the design of mechanism.The clearance was described in a way of vector calculus based on two-statediscontinuous contact model for analyzing mechanism clearance. The clearance,contacts and collision described in nonlinear spring-damper model and modifiedCoulomb model were integrated into the ideal model to set up the multi-bodydynamics model involving clearance. In view of the planetary indexing cam of pinion and rack, the dynamics model ofpinion-and-rack planetary indexing cam was established by ideal setup of contactparameters in Adams. This paper also researched the dynamics performance of cammechanism with different clearance and analyzed the effect of clearance on theperformance of cam mechanism.