Research On Equivalent Stiffness And Redundant Structure Of Elastic Cylindrical Indexing Cam Mechanism

Indexing mechanism is one of the core components of light industrial machinery such as printing and packaging machines.The indexing cam mechanism has gradually replaced other intermittent transmission mechanisms such as grooved wheel mechanism because of its good motion characteristics among many indexing transmission mechanisms.So,this indexing cam mechanism possessed huge market demand.In indexing cam mechanism,the cylindrical indexing cam mechanism was once widely used due to its numerous advantages,such as simple structure and lower manufacturing cost.With the increasingly demanding of motion accuracy and production efficiency on automatic machinery,the precision,speed and motion stability of the indexing cam mechanism must be enhanced.In this case,the cylindrical indexing cam mechanism could not to meet these requirements,and was gradually replaced by globoidal indexing cam mechanism.Although the globoidal indexing cam mechanism shows better motion characteristics at high speeds,its maching and assembly was difficult lead to high cost.Especially,the globoidal indexing cam mechanism could not transmit with large indexing numbers.The elastic cylindrical indexing cam mechanism was studied by systematically analyzing the contact deformation of roller and bending deformation of pins.The purpose of this research was to improve the transmission accuracy and stability of cylindrical indexing cam mechanism and solve its problems of low precision and poor motion stability.At the same time,combined with the structural parameters of the roller follower,the selection of equivalent components of system stiffness and the calculation of equivalent stiffness were completed in this dissertation.Based on the analysis above,two kinds of redundant structures which can eliminate the transverse impact of cylindrical indexing cam mechanism were proposed,and their theoretical analysis and experimental verification were carried out.The main research work of this dissertation is described as follows:(1)Analysis of load and deformation of the cylindrical indexing cam mechanism followerBased on the analysis of the load of cylindrical indexing can mechanism,its maximum allowable load was calculated according to the theory of contact fatigue strength and bending fatigue strength.Combined with the structure size of the roller follower,the bending deformation of the pin and the contact deformation of the roller were calculated,which provides a basis for the subsequent analysis and research.(2)Research on the system equivalent stiffness of elastic cylindrical indexing cam mechanismBased on the analysis of the selecting principle of the system stiffness equivalent component,the pin was considered as the equivalent component of the stiffness of the cylindrical indexing cam mechanism,by calculating the elastic deformation of the main components.According to the structural parameters relationship of roller follower,the deformation and simplification of the calculation formula of contact deformation were carried out by using minimum error analysis method,and the calculation formula of elastic approach produced by the contact between roller and cam was transformed into a linear relationship between load and deformation.With the relevant results,it turns out that the contact deformation of roller and the bending deformation of pin were all equivalent to the elastic deformation of pin,therefore,the equivalent stiffness coefficient of the system was derived.The maximum relative error between the total elastic deformation calculated by equivalent stiffness and the theoretical value is only 1.3251%.The selection of equivalent component and the calculation of equivalent stiffness provide a theoretical basis for the study and analysis of elastic cylindrical indexing cam mechanism.(3)Proposal of two redundant cylindrical indexing cam mechanismsBased on the analysis of the causes and hazards of transverse impact,in order to avoid transverse impact.Two innovative mechanisms were proposed,namely large and small roller cylindrical indexing cam mechanism and double roller cylindrical indexing cam mechanism.By analyzing two redundant structures,it was proved theoretically that the two redundant structures can eliminate the transverse impact of the cylindrical indexing cam mechanism and improve the motion stability.(4)Design of the main structural parameters of two redundant cylindrical indexing cam mechanismsThe load analysis of two kinds of redundant cam mechanisms was conducted to avoid transverse impact and jump phenomenon.According to the strength condition,the design theory and method on the main structural parameters of two kinds of redundant indexing cam mechanism were established.Based on the conclusion of equivalent stiffness of the system,the elastic deformation requirements of the two redundant structures were analyzed,and the deformation compatibility conditions were verified.These conclusions provide theoretical basis for the parameter design and machining tolerance requirements of two kinds of redundant cam mechanisms.(5)Building of test platform for motion characteristics of cylindrical indexing cam mechanismIn order to verify the rationality of the design of two redundant cylindrical indexing cam mechanisms,a test platform was designed.According to the test purpose,two kinds of redundant cam mechanisms were designed and manufactured.The speed regulating motor and frequency converter,the acceleration sensor and the encoder and so on were selected.Finally,a motion characteristics test platform of cylindrical indexing cam mechanism was built.This work provided software and hardware basis for the comparison and verification of two redundant cylindrical indexing cam mechanisms.(6)Verification of the motion characteristics of the two redundant cylindrical indexing cam mechanismsThe performance comparison test of cylindrical indexing cam mechanisms with different structures were carried out on the test platform.The acceleration data collected at different positions of the shell of the test device.The maximum acceleration value of the shell was reduced more than 48%by two cylindrical indexing mechanisms with redundant structure.It was verified that these two redundant mechanisms can depress the vibration and noise.Though the comparison of the angular accelerations of the driven disk of cylindrical indexing cam mechanisms with different structures,the maximum accelerations of large and small rollers and double rollers cylindrical indexing cam mechanisms were only 10.49%and 10.76%respectively account of the common cylindrical indexing cam mechanism.It was verified that these two redundant indexing cam mechanisms could eliminate the transverse impact and improve the motion stability of the driven disk at high speeds.With the research aiming at cylindrical cam,by utilizing the elastic theory,this dissertation conducted the selection of equivalent components of system stiffness and the calculation of equivalent stiffness,which enriched the research theory of elastic cylindrical indexing cam mechanism.The proposed two kinds of redundant cylindrical indexing cam mechanisms,in order to eliminate the transverse impact,meanwhile,design analysis and test verification were carried out.The results show that these two redundant cam mechanisms break the limitation that cylindrical indexing cam mechanisms could only work at low and medium speed.The research results provide a reference for the development and application of elastic cylindrical indexing cam mechanism.Moreover,and the improvement of the stability of indexing motion as well as the production efficiency of automatic machinery.