Research On Key Technologies Of In-mold Lamination Process

As the development of automobile industry,in order to enhance and/or change the appearance of automotive interiors,it is necessary to improve the soft touch and texture,and usually add the outer cover on the surface of the plastic product,such as artificial leather(PVC leather),fabric,PU leather,genuine leather and so on.In the traditional process,first got the plastic substrate through injection molding and then bonded the outer cover on its surface.There are some issues such as many processes,high production cost and environmental pollution in the process.However,in in-mold lamination process,first put the laminated material(outer cover)in the mold cavity,then the plastic melt flowed on the inner surface of the laminated material after the mold was closed,and at last the laminated material was firmly attached to the outer surface of the molded plastic part after cooling.There are many advantages in this process,such as low cost,environmental protection and etc.However,in-mold laminating process is very different from the traditional process and very difficult to achieve.There are also many problems in the process,such as the laminated material is very easy to crack and wrinkle,the laminated material is easily peeled from the plastic substrate,and the injection molding equipment is special and expensive.Aiming at the above problems,this paper has carried out the following research work.The mechanism and main influencing factors of defect formation were researched,through theoretical analysis,experimental research and numerical simulation.The mechanical properties of PVC artificial leather was tested and analyzed,and the characteristics of strong strain rate sensitivity was found in the material.The nonlinear elastic constitutive model was established,and the effect of forming speed on the forming performance was researched by ABAQUS/Explicit finite element numerical simulation.The result provided the guidance for predicting defects and optimizing the process and mold structure.The formation mechanism of interlayer interface between in-mold lamination product was proved,and the main factors influencing of the interlayer bonding strength was researched,through the interface interlocking theory and diffusion theory.The influence of plastic substrate and injection parameters on the interlayer bonding strength was also researched by experiment.The result provided the scientific rule and optimization method for obtaining the best interlayer bonding strength of the product.The characteristics of in-mold laminating process was researched.Considered the actual situation of the abroad in-mold lamination injection machine was too expensive,a new scheme of developing an external control system on the universal injection machine was proposed.The embedded control system for in-mold laminating injection was researched and developed,and also the hot runner system temperature control and neutron motion control algorithm was built up.Through the test and application,the control system could meet the requirements of in-mold lamination process,and reduced the cost of the injection molding equipment.Take the in-mold lamination product of the frame inside the car interior door as an example,the product of the formability analysis was carried out.Analysis and optimization for the laminating process and the injection process were also researched thourgh numerical simulation.The special structure mould was designed and developed.The practical application and verification of the in-mold process were realized,and the process was popularized and applied in the automotive industry.Therefore,the key technologies of in-mold lamination process were researched systematically,such as formability of the laminated material,interlayer bonding strength,in-mold lamination control system and mold structure design.The technical bottleneck was broken and the engineering application of the process were achieved,which provided theoretical guidance and technical support for the further popularization and application for in-mold lamination process.