Study On Stability And Optimization Of Wide Extrusion Flow Field

Under the continuous development and reform of building materials industry,polymer waterproofing membrane has been further developed.With the continuous development of social economy,polymer waterproofing membrane is widely used.Polymer waterproofing membrane is not only used in apartments,shopping malls,parking lots and other living areas,but also used in tunnels,subways and other transportation facilities,water conservancy projects such as hydropower stations and agricultural fields.These fields all put forward higher quality requirements for polymer waterproofing membrane.Extrusion has become the main molding method of polymer waterproofing membrane because of its good compactness.However,due to the rheological properties of polymer materials and the structural characteristics of the extruder head,the flow velocity and temperature rise in the center of the flow field are different from those on the upper and lower walls.This brings about the problems of poor extrusion uniformity,excessive temperature difference,and inconsistent flow rate.All of these will lead to the change of the stability of the rubber extrusion flow field,and eventually lead to the warpage deformation of the waterproof membrane and the decline of the waterproof performance.Therefore,it is very necessary to study the forming process and flow characteristics of rubber in wide extruder head.The flow process of three-dimensional non isothermal flow field in wide range extruder head is studied by finite element analysis and response surface optimization method,considering the influence of temperature field.The rheological behavior is clarified and the cooling scheme is optimized.A theoretical model is established between the target parameters and the important parameters that determine the product quality uniformity and productivity.The quantitative relationship is established to provide theoretical basis for the extrusion production of wide film.The extruder head with high efficiency and high quality was optimized.The optimal way of process parameters,structure parameters and material parameters is established.It has practical engineering significance for enterprises to improve efficiency and productivity,accurately control the size of products and reduce costs.The main tasks are as follows.(1)A three-dimensional non isothermal mathematical model of polymer melt in the die flow field is established,and the heat transfer analysis of the melt flow process in a large range extruder head is carried out.The three-dimensional non isothermal flow can more truly and effectively reflect the flow state of the fluid in the wide range extruder head.(2)FLUENT is used to simulate the flow of rubber in the channel of wide die.StarCCM+ is used to capture the geometry of extruded wide sheet after elastic deformation was restored,and the Extrusion Swell Behavior of sheet after exit is predicted.(3)The temperature control system of wide extruder head is studied.The influence of different temperature control systems on extrusion is analyzed.Considering energy consumption and extrusion uniformity,the temperature control system of wide extruder head is optimized.The purpose of choosing parallel cooling mode instead of series cooling mode is to improve the heat dissipation power of compound and extrusion output of sheet,and reduce the temperature difference in the thickness direction of exit sheet.(4)Single factor analysis method is used to study the influence of structure,process and physical parameters on the flow stability of polymer melt.The influencing factors and rules of extrusion speed and uniformity of wide extruder head are determined,which provided guidance for industrial production parameters.(5)The mathematical relationship between the influencing factors and extrusion efficiency and quality was determined by the combination of finite element analysis and response surface method.The quantitative mathematical model is established and verified.It is found that the errors of predicted value and actual value of extrusion speed mean value and extrusion speed standard deviation are ±4% and ±5%.The multiobjective optimization method is adopted to improve extrusion efficiency as far as possible on the basis of ensuring the uniformity of extrusion.The structure,process and physical parameters of the extruded die are obtained and verified.The error between the mean value of extrusion speed and standard deviation of the optimized extruder head and the predicted value of theoretical model is 1.19% and 2.9%,respectively.The theoretical model and optimized parameters have engineering significance for practical guidance.