Experiment Researeh On The Process Of Polymer Micro-machine In-mold Assembly Molding

In-mold assembly molding of polymer micromachines is a new technology in which technological bottlenecks of micromachines micro-assembly manufacturing process can be effectively solved, however, the thermal-fluid-solid coupling effect between polymer high temperature viscoelastic melt flow and preformed micro solid part can be caused which induces preformed micro solid part producing frequently the thermal-fluid-solid coupling deformation and necking fusing fracture phenomenon, how accurate control and predict thermal-fluid-solid coupling deformation and necking fusing fracture phenomenon is key scientific issues of in mold micro assembly molding technology industrialized application. Therefore, based on the developed variable combination mold and Auto model FB-110 C polymer co-injection molding machine, the polymer micromachines In-mold assembly molding experimental research platform was established, by which the influencing rule and influencing mechanism of process parameters and properties of polymeric materials on preformed micro shaft thermal-fluid-solid coupling deformation and necking fusing fracture phenomenon were systematically studied, key regulatory parameters of thermal-fluid-solid coupling deformation and necking fusing fracture phenomenon in in-mold micro assembly molding process was clarified; the scientific foundation of the research and development of thermal-fluid-solid coupling deformation precision-shaped control technology and the prevention technology of necking fusing fracture phenomenon was laid. The main innovations and achievements as follows.The variable combination mold of typical micro mobile motion pair in-mold micro assembly molding was developed, and Based on the developed variable combination mold and Auto model FB-110 C polymer co-injection molding machine, the polymer micromachines In-mold assembly molding experimental research platform was established.The influencing rule and influencing mechanism of secondary molding melt injection temperature, secondary molding melt injection pressure and screw stroke on necking fusing fracture phenomenon of preformed micro shaft, the research results show key regulatory parameter of preformed micro shaft necking fusing fracture phenomenon is secondary molding melt injection volume, when the secondary molding melt injection volume exceeds its critical melt injection volume, the critical melt injection volume of induced preformed micro shaft necking fusing fracture phenomenon depends on secondary molding melt injection temperature, which is positively proportional to secondary molding melt injection temperature. Improving of secondary molding melt injection temperature will help improve the critical melt injection volume of induced preformed micro shaft necking fusing fracture phenomenon, which increase the secondary molded part density and strength in In-mold assembly molding process, at the same time, but also to avoid preformed micro shaft necking fusing fracture phenomenon.Experimental research results show that the micro shaft unidirectional necking fusing fracture phenomenon possible ways have two main factors, firstly, the axial tensile force is too large; secondly, the preformed micro shaft near-surface temperature in a secondary molding process is too large, which led to partial melting and a sharp decline of elastic modulus. The heat transforms time contact between secondary molding high temperature and preformed micro shaft will prolong with increasing of secondary molding melt injection volume, which make the preformed micro shaft near-surface temperature improve with increasing of screw stroke. When the preform micro shaft near-surface temperature exceeds the glass transition temperature, local micro assembly interface of preformed micro shaft will experience continuous phase transition evolution from elastoplastic solid state to viscoelastic plasticity glassy state,final to viscoelastic high-elastic state, which led to a sharp decline of elastic modulus and make polymer material in local phase transition evolution region lost the ability to resist deformation, preformed micro shaft in local phase transition evolution region of micro assembly interface must produce necking phenomenon under tensile force effect. When the tension force reaches a certain level, preformed micro shaft will produce the necking fusing fracture phenomenon. In order to preform micro shaft near-surface temperature does not exceed the glass transition temperature, which requires its secondary molding melt injection volume does not exceed the critical injection volume. Based on above necking fusing fracture mechanism, the preparatory proposed necking fusing fracture mechanism theory and prevention technical method of preformed micro shaft necking fusing fracture provide technical support for the industrialized application of In-mold micro assembly molding technologyExperimental research results show that the preformed micro shaft thermal-fluid-solid coupling deformation depends on secondary molding melt injection temperature, secondary molding melt injection pressure, secondary molding melt injection volume and preformed micro shaft material properties,and the process parameters affect its thermal-fluid-solid coupling deformation by adjusting pre-formed micro shaft micro assembly interface to withstand the impact of the thermal-fluid-solid coupling pressure, viscoelastic supporting normal stress, viscous friction drag shear stress and micro shaft stiffness against deformation,the preformed micro shaft thermal-fluid-solid coupling deformation increase with increasing of secondary molding melt injection temperature,secondary molding melt injection pressure, secondary molding melt injection volume, and based on key regulatory parameters of viscoelastic supporting normal stress, viscous friction drag shear stress and micro shaft stiffness against deformation, the formation mechanism of preformed micro shaft thermal-fluid-solid coupling deformation was revealed.