Fatigue Characteristics Of An Insert Part In Injection Mold Under Thermal-mechanical Load

With the rapid development of machinery and electronics industry,plastic products are being used widely,the demand is becoming greatly,species are also more diversified,the structure is trending to be complicated,and thus the function of mold for plastic products should be better to fit the request.Now the mainstream mode of production of plastic parts is injection molding process where mold endures not only enormous injection pressure but thermal shock caused by high temperature melt.The injection process is cyclic and may last for hundreds of thousands of times.During the process,mold has to withstand stress with periodic changes,the combined action of thermal stress and mechanical stress may lead to fatigue,which may cause the defections in parts,scrap of mold and even casualties that can also cause huge economic losses to the enterprise.If the fatigue property of mold can be predicted in the design stage,the occurrence of such problems can be prevented effectively.So,the study on mold fatigue is of great significance to the reduction of loss and cost.This thesis takes an mold of OA classifications as research object.After getting the melt temperature and pressure in the insert location through Moldflow software,then the results are used for transient thermal stress analysis and static structure analysis respectively.Finally,the fatigue property of the insert is analyzed based on thermal stress and mechanical stress,using nCode software.The main work in this paper is as follows:(1)After establishing printer drawer product,hot runner system and cooling system,the numerical analysis of injection molding is carried out,thus the melt temperature and pressure change at insert location are obtained.(2)Use melt temperature result as load to start transient thermal analysis for insert and assembly,get steady state temperature field of insert.Set mold temperature as the initial temperature and transient thermal analysis is done to obtain the stress distribution of insert.(3)Considering that the injection pressure is not a fixed value,the holding pressure is chosen as a load,thus the mechanical stress distribution is obtained.(4)The mechanical stress temperature and transient thermal are mingled to analyze the fatigue life of the insert part with mean stress correction theory through nCode software,the life distribution is finally obtained and in accordance with the actual failure,the method to improve life is also given and verified.