Numerical Simulation And Application Of Secondary Injection Molding

With the rapid progress of the plastics industry,plastic products have developed toward to high-performance,multi-functional composite structures and green environmental protection.However,traditional injection molding technology is difficult to adapt to this new trend.Therefore,Secondary injection molding is a new plastic processing method,conforms to this trend and has been widely used in the automotive,electronics,furniture,packaging,chemical and medical devices industries.In this paper,with the help of commercial numerical simulation sofftware Moldflow and Taguchi DOE technology,the process parameters of the underfill and warp of overmolding mobile phone keys were optimized,and a new technical optimization scheme was proposed.By adopting the combination of experiment and numerical simulation methods,the shear force field and temperature field during the injection molding process of the sandwich core were analyzed.Based on the energy field,the formation of cylindrulite during the injection molding process of the sandwich core were quantified.The theoretical basis was provided for the molding process parameters and the crystal morphology and properties of the co-injection molded products.The main contents and conclusions of this paper are as follows:(1)By means of numerical simulation technology,the influence factors of process parameters on underfilling and warping of side keys of the mobile phone in secondary injection molding were studied.According to the influence of process parameters on product quality indexes,the molding process parameters were optimized to solve the problem of underfilling and warping of side keys in the molding process.(2)According to the large amount of cold material and long process for the side keys of overmolding mobile phone,a new technical optimization scheme was proposed.The hot runner system was adopted for optimization,and the advantages in product stress reduction,product deformation reduction and economic aspects brought by the optimization were analyzed with the help of numerical simulation technology.(3)Combined with numerical simulation and polarizing experiments,the data of shear force field,velocity field and temperature field in the forming process under different process parameters were studied,and the reasons for the difference in thickness direction were analyzed.The ratio of shear force work to energy change in the temperature field was used as the criterion for clindrulite formation.The criterion was to consider the influence of shear stress,velocity,temperature and time,and the clindrulite criterion was normalized according to Jcr unit.According to the treatment,the criterion of the formation condition of the clindrulite was established from the energy point of view.According to the range of the interval,a universal condition for the formation of the clindrulite was preliminarily established,that is,the Jcr value range of the clindrulite criterion wass[2.08,18.46].(4)With the help of numerical simulation technology,the influences of the traditional waterway of the electronic cigarette oil cup and the 3D metal printing conformal waterway on the surface temperature,molding cycle and warpage of the product were compared and analyzed.It was found that the temperature distribution of the 3D metal accompanying waterway compared with the traditional waterway product.More uniform,the molding cycle was shortened by 46.23%,and the warpage deformation was reduced by 29.98%.For the workpiece containing a large deep cavity mold,combined with 3D metal printing technology,the design of the cooling pipeline can be more scientific.