Optimization And Application Of Injection Molding Technology For Glass Fiber Reinforced PBT

PBT(butylene terephthalate)has high heat resistance,toughness and fatigue resistance,and has been widely used in automobile,mechanical equipment,precision instrument parts,electronic and electrical appliances.However,the molecule contains ester bonds,which will decompose under the action of strong acid,strong alkali and water vapor.The material is sensitive to notch and brittle,so glass fiber reinforced modification is commonly used.At present,injection molding of the mould has become an important means to improve the production scale and efficiency of glass fiber reinforced PBT materials.Then,due to the different content of glass fiber,it may lead to great changes in injection molding process and molding law.How to control the process parameters to obtain high-quality parts is an urgent problem to be solved.This paper first analyzes the characteristics,uses and modification methods of PBT.According to the characteristics of glass fiber reinforced PBT,it is judged that it is non-Newtonian fluid to study the injection process and analyze the viscosity model.Then,the quality problems of the materials are studied,and the mechanism and influencing factors are analyzed.The first mock exam is based on material characteristics.A thin-walled workpiece is selected.The filling system and cooling system are determined by using the molding software Moldflow.The gating system and cooling system are determined.According to the two cavity needs of a mold,side gate and two cooling water channel are selected.In order to obtain the better combination of process parameters,orthogonal test method was used to study the forming process.Three kinds of PBT materials with different glass fiber content were studied by orthogonal experiment.The primary and secondary effects of four process parameters on warpage,volume shrinkage and shrinkage mark were obtained.According to the analysis of variance,the influence degree of four process parameters on them under different glass fiber was obtained.Then the glass fiber content and the three quality indexes were studied.It was found that with the increase of glass fiber content from 10% to 15% and then to 30%,the three indexes decreased as a whole.Therefore,30% glass fiber reinforced PBT material is suitable for production.The single factor simulation study was carried out to study the influence of the most influential factors on the three factors,and the optimal combination of parameters was obtained,that is,injection temperature 230 ℃,mold temperature 85℃,holding time 10 s,and injection time 0.2S.The rules are applied to the actual production of the factory,and the products meet the size standard for subsequent assembly and put into the market.