Study On Numerical Simulation And Cylindritic Structures Of Co-injection Molded Polypropylene Parts

With the rapid development of plastic industry, co-injection molding as a new type of plastic processing method, widely used for cars, electron, furniture, packaging, chemical, medical equipment and other industries. This article primarily aims at co-injection molding, depends on the compare of experimental results and simulation results to illustrate the reliability and accuracy of the simulation software-Moldflow by researching the effect of process parameters on the core material penetration behavior. This article also studies the micromorphology on the dead line and core melt front of the co-injection molded products. Meanwhile, base on the temperature field analysis, attempts to quantify the forming conditions of cylindritic structures.The main content of this article:(1) The co-injection molding of exising experiment was simulated using the Co-injection module of Moldflow simulation software, the effect of processing parameters on the core material penetration behavior was investigated. The reliability and predictive accuracy of the simulation software-Moldflow for core material penetration behavior was verified by comparing the experimental results and simulated results, but the simulation software can’t simulate the deflecting of the core material.(2) Microscopic crystal morphology along the direction of thickness at different location of the co-injection molded parts prepared by different process parameters was researched by PLM. There is no special crystal form near the gate. The appearance of cylindritic structures at the delayed line mainly relates to the injection rate of core layer. The emergence and the quantity of the cylindritic structures are not increased with the injection rate. When the rate is larger enough, the quantity of cylindritic structures is less, and even does not appear.20mm/s is the best rate when cylindritic structures appear in this experiment.(3) Microscopic crystal morphology at the melt flow front in core layer of the co-injection molded parts relates to the delay time、injection rate of core layer. When the delay time is1s, there is no cylindritic structure. When the delay time is5s, cylindritic structures grow along the outline of the core layer melt front. And it is located near the interface of skin material and core material. The core material melt temperature is constant, and when the core material injection rate is10mm/s, the quantity of cylindritic structures is largest.(4) Through the statistics and analysis of skin layer thickness and cylindritic structures position, in combination with the results of numerical simulation, with the help of Matlab software, complet a given process parameters under the condition of one dimensional unsteady heat transfer with heat source analysis and obtain the thickness of the products specified location of temperature and heat energy. From the angle of energy, in this experiment, in the scope of [39.30,108.27] J/m3, cylindritic structures maybe exist.