| Precision injection molding is an advanced molding method for producing high-precision,high-surface-quality plastic products.The key technical problem is to keep the plastic melt in the mold cavity at a stable temperature and good fluidity.Preparing a layer of low thermal conductivity coating on the inner surface of the mold cavity is a relatively novel technological means,which can keep the temperature of the melt in the mold cavity stable and improve the apparent quality and mechanical properties of the plastic part.This topic combines the preparation of thermal barrier coatings with precision injection molding methods.First,a universal porous composite thermal barrier coating preparation and performance control method is proposed,and then the melt in the mold cavity and the The heat transfer mechanism between the molds has been studied in depth,and the influence of the heat transfer process on the apparent quality of the plastic part is analyzed in multiple dimensions.Finally,the effect of the proposed thermal barrier coating of the porous composite material is carried out in the injection molding production.了Verification.The research ideas and main contents of this topic are as follows:(1)The porous 7YSZ(zirconium oxide stabilized with 7%yttria)coating is prepared by atmospheric plasma spraying,and a certain amount of PA 11(polyamide-11)is added to the 7YSZ powder to adjust the performance of the coating.The obtained 7YSZ coating has a mixed structure of tetragonal and cubic phases.By changing the content of PA11 added to the 7YSZ powder,various properties of the coating can be controlled.When the PA11 content is 10%and the coating thickness is about 230 μm,its overall performance is the best.The bonding strength of the coating can reach 31.7 Mpa,the hardness of the coating can reach 940 HV,and the thermal conductivity of the coating continues to decrease with the increase of PA 11 content.Heat treatment is beneficial to further decompose the residual PA 11 in the coating,increase the porosity of the coating and promote a more uniform pore distribution.(2)Modeling is performed by Solidworks,heat transfer analysis is performed by Ansys Workbench,and melt filling simulation is performed by Moldex 3D.The results show that by directly reducing the thermal conductivity of the mold or indirectly reducing the thermal conductivity of the mold by using a thermal barrier coating,the temperature distribution in the mold cavity can be made more uniform,and the formation time of the solidified layer on the melt surface is gradually delayed,thereby increasing The fluidity of the melt in the mold cavity enables the melt to fill the cavity more fully.Higher melt temperature can reduce the filling pressure and injection pressure of the melt,and is beneficial to shorten the length of the weld mark and reduce the weld mark phenomenon of the product;in addition,the thickness ratio of the melt solidification layer also increases with the temperature Higher and lower,smaller thickness of the solidified layer indicates that the fluidity of the melt in the cavity is improved,which is beneficial to the improvement of the surface quality of the plastic part and the improvement of the mechanical properties.(3)Using the mold coating platform independently built by the laboratory team,based on the study of the coating performance control methods in this subject,appropriate coating preparation process parameters were selected,and 7YSZ with different thermal conductivity was prepared on the surface of the mold cavity Coating,and explored its influence on the surface quality and mechanical properties of injection molded products.By preparing a suitable coating in the mold cavity,the weld line of the injection molded product can be significantly eliminated and the mechanical properties of the product can be improved. |
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