Numerical Simulation And Process Optimization For Injection/compression Molding For Plastic Transparent Products

Transparent polymer materials are widely used in optical,electronic,aerospace and other fields due to their excellent properties.The transparent plastic products produced by conventional injection molding have large residual stress,deformation and less light transmittance,which seriously influence the performance.The additional compression process in injection compression molding effectively reduces the residual stress of the product and improves the product quality due to the polymer molecule's re-orientation caused by the uniform pressure in this stage.However,the injection-compression conversion time,compression time,compression distance and other process parameters interact with each other.The mechanism of action is very complicated.It is necessary to reveal their internal relations through theoretical analysis and experimental verification,and find control methods to provide theoretical support and technical guidance for actual injection compression molding production.This paper established a theoretical model of PS and PC melt fluid based on three-dimensional viscoelastic flow theory.An iterative algorithm for numerical solution was proposed based on the nonlinear characteristics of the governing equation and the constitutive model.The experimental mold was designed,and the multi-process PS and PC injection compression molding experiments were carried out,and the birefringence of the molded product was measured.Based on theoretical analysis and forming experiments,the orthogonal injection test method was used to optimize the injection compression molding process conditions,and the experimental verification was carried out.The main results of this paper are as follows:1.The 3D flow model based on viscolastic and ALE principle was founded,optimization of governing equations and constitutive equations by introducing material derivatives,the Galerkin method was used to establish the variation equations of the energy equation,the momentum equation and the continuous equation,the two-fold iterative decoupling algorithm was used to solve the equations.To ensure the mesh quality,the convection term?35?t w^n?10?1 was added based on the Lagrangian method,a simulation program was developed to better predict the injection molding process.2.A flat test mold was designed and fabricated,and a pressure sensor and a temperature sensor were mounted on the surface of the cavity,an injection compression molding experiment was carried out,and the simulated intracavity pressure and the measured melt pressure were compared,the birefringence image and the simulated birefringence image of the injection compression molded product measured by photoelastic experiment were analyzed,the simulation results were consistent with the experimental results,and the rationality of the theoretical model and numerical algorithm established in this paper was verified.3.The injection compression molding simulation was carried out in combination with the orthogonal test method.The influence of the process parameters on the injection compression molding products was analyzed.The process parameters with significant influence were selected and the process parameter combination in the compression stage was optimized.The injection compression molding experiment and simulation were carried out with the combination of optimal and common process parameters.The experimental results were basically consistent with the simulation results.It was proved that it is feasible to optimize the injection compression molding parameters based on the orthogonal test method.4.In this paper,it was found that the compression distance and compression time have a significant effect on plastic injection compression molding,and the degree of influence varies with materials.For the PS material compression stage,the optimal process parameters are:compression distance 0.5 mm,compression time 5 s,compression force 20 t,compression speed 6 mm/s.For the PC material compression stage,the optimal process parameter combination are:compression distance 0.5 mm,compression time 2 s,compression force 20 t and compression speed 6 mm/s.