Research On Eliminating Adhesion Between Micro Plastic Parts Of Same Polymer Molded By In-mold Assembly Injection

In-mold assembly injection molding of micro plastic parts can not only reduce secondary operation of assembling various micro plastic parts after demolding and improve efficiency as well as quality of micro assembly, but also innovate structure of the plastic parts and simplify composition of the plastic mechanism. As a result, the operation reliability of the micro plastic mechanism can be promoted. On the other hand, if the micro plastic parts molded by in-mold assembly injection are made of same polymer, requirements for complexity and cost of the injection-molding machine can be reduced, which plays strong realistic role in practice.How to eliminate adhesion between the micro plastic parts molded by in-mold assembling is crucial to quality of in-mold assembly injection molding. In this thesis, the way to avoid adhesion phenomena at the solid-melt interface of same polymer was analyzed, and experiments of measuring adhesion strength between the parts injection-molded by same polymer were carried out. Then the ice-cold system for micro core of the mold was optimized. And the temperature field of the improved refrigeration module was simulated to shorten time needed for eliminating adhesion between the micro plastic hole and the micro plastic pin which composed the micro plastic hinge and at the time ensure good quality of the micro plastic rotating mechanism. The thesis includes the following specific contents.Firstly, in order to find out temperature condition of avoiding inter-surface adhesion between parts of micro plastic binge molded by same polymer with the single-cylinder micro injection molding machine, experiments of the solid-melt interface adhesion between parts injection-molded by same polymer were carried out. And impact of temperature at the curing solid surface on adhesion phenomenon of same polymer was analyzed to provide reference data for specific application of the ice cold trick.Secondly, based on results of adhesion experiments, structure of the ice cold system which uses semiconductor refrigeration chips as core components and uses heat pipes and cold water as heat transfer approaches was optimized. And the goal of regulating temperature of the micro core to a reasonable low temperature was achieved, which makes it possible to extremely cool the polymer melt surface that contacts with the micro core during in-mold assembly injection molding, and then the ice cold trick can be actualized.At last, the optimized ice cold system was integrated with the micro injection mold, and temperature of the micro core which was placed in practical injection molding environment was measured. By taking temperature of the micro core as boundary condition of the plastic micro hole, the instantaneous temperature field of the micro-hole plastic part was simulated by using ANSYS software. As a result, variation process of the solidifying surface temperature was predicted for the plastic micro hole that contacted the micro core under refrigeration condition. And this analysis provided valuable judgment for determining reasonable cycle time of in-mold assembly micro injection molding using same polymer.