Research On Evolution Discipline Of Bubble Morphology And Structure In The Process Of Microcellular Foaming And In-Mold Surface Decoration Combined Injection Molding

Microcellular foam injection molding is a sustainable process,and the poor surface quality of products restricts its application in appearance parts with high apparent quality requirements.In order to improve the surface quality of the parts,drawing on in-mold surface decoration,this paper proposes a process of microcellular foaming and in-mold surface decoration combined injection molding.It can not only use the advantages of microcellular foaming to produce products with light weight,high precision and excellent mechanical properties,but also can take advantage of in-mold surface decoration to overcome the lack of apparent quality of microcellular foaming products.It obtains excellent plastic products with smooth appearance and light weight at one time,which greatly promotes its engineering application in appearance products.Compared with the conventional microcellular foam injection molding,the bubble morphology structure's evolution and distribution have undergone a significant change due to the embedding of the decorative film.In order to study the evolution law of bubble morphology and structure in the microcellular foaming and in-mold surface decoration combined injection molding,this paper did the following work:The mathematical model of bubble growth is established.The boundary conditions of bubble growth are set by cell model and differential forming conditions;the filling control equations of bubble growth are derived by continuity equations,motion equations,and energy equations;the control equations of bubble growth are established by gas thermodynamics and dynamics theory Finally,the macro link of the microscopic bubble growth model is established.The dynamic process of bubble growth is studied According to the mathematical model of bubble growth,Moldflow simulation was carried out to study the forming process and the growth of bubbles at different stages,revealing the evolution law of bubble growth.The results show that: the evolution process of bubble growth is divided into three stages: asymmetric melt flow,filling growth and deformation,and cooling growth and shaping.in which the melt is in an unfoamed state during the asymmetric melt flow stage;the bubbles in the thickness direction of the spline have a large radius in the middle and small radii on both sides during the filling growth and deformation stages,in the cooling and shaping stage,the bubbles in the thickness direction of the spline have a large middle radius,small radius on both sides,and the bubble radius of the decorative film is larger than the non-decorative film.At the same time,some bubbles are deformed due to the fountain effect.The influence of process parameters on bubbles structure and mechanical properties was analyzed.According to the dynamic process of bubble growth,a single factor experiment method was used to analyze the influence of process parameters on bubbles structure and mechanical properties.The influence of injection rate,melt temperature,SCF ratio,mould temperature,and filling volume before V/P switch on bubbles structure and mechanical properties was obtained.Process parameters are optimized and cell structure is controlled.According to the influence of process parameters on bubbles structure and mechanical properties,the optimization of process parameters was analyzed using Taguchi design the optimal process combination was obtained: mould temperature 75 ?,melt temperature 180 ?,injection rate 60 cm3/s,filling volume before V/P switch 86%,SCF ratio 1.1%.Through multiple regression analysis,it was found that there is a linear correlation between the process parameters and the average bubble density,and the relationship model between the process parameters and the bubble density is established.