Stress Analysis And Fatigue Fracture Research Of Injection Molding Machine

The injection molding machine is the core equipment of rubber injection molding which withstands the alternating mold load when in service.Engineering practices show that the main failure mode of the injection molding machine is the fatigue fracture at the thread connection between the column and the nut.This kind of damage is closely related to the magnitude and distribution of the stress generated by the axial force at the thread,and thus,related to the size and structure of the column thread.In this thesis,stress analysis and fatigue fracture tests were conducted on a 3000KN four column injection molding machine.The main contents are as follows.(1)Finite element analysis of the structure of the injection molding has been conducted with the ANSYS software.Mises equivalent stress and maximum principal stress distribution at each parts of the machine were extracted.Strength assessment was carried out based on maximum Mises equivalent stress.At the same time,deformations at each part of the machine were examined especially the maximum deformation on the columns.(2)Stress measurements were performed on the injection molding machine when the mold-close force was applied and the stress values on columns were obtained.The results of the axial stress measurement at the columns are compared with those obtained from the numerical simulation to verify the accuracy of the ANSYS simulation results.(3)Finite element analysis was carried out on a single threaded column based on the results obtained from the whole machine.The stress distribution at the thread was specially concerned.Axial,hoop,and radial stresses at the thread of the column were extract and the maximum principal stress were calculated which is taken as the strength parameter to determine the possibility of the fatigue fracture of the column.(4)To study the problem of fatigue fracture of columns,threaded specimens were manufactured from the same material as the column(42CrMo)and fatigue tests were conducted.The loads for the tests were determined referring to the numerical calculations.The number of cycles before fracture for each specimen was recorded which will provide reference data for future column and whole machine structural design.