Study On Flow Imbalance Of Injection Molding Filling For Products With Microstructure

With the rapid development of micro/nano technology,micro-injection molding technology has become one of the research hotspots.Due to the small size and high precision of micro-injection molding products,the flow characteristics of melt in the process of molding are different from those of macro-injection molding,which make the traditional injection molding process not completely applicable to micro-injection molding.At present,the theory of micro-injection molding is inadequate enough,and the rheological properties of melt in the process of micro-injection molding need to be further studied.In the actual production,in order to improve production efficiency and reduce costs,a multi cavity balanced runner system is usually adopted in injection molding,but the phenomenon of filling imbalance usually occurs,which is difficult to ensure the quality consistency of plastic parts.In this paper,polypropylene(PP)was used as raw material.Considering the forming characteristics,structure and size of micro-structure injection products,an injection mold with micro-structure characteristics was designed.The effects of mold temperature,injection rate and injection pressure on filling rate of microstructural injection molding products and the imbalance of melt flow in the forming process were analyzed.Combining with the numerical simulation software,the essential reason of flow imbalance was revealed,and the flow passage system was improved.The main works of this paper are as follows:1.The injection mold with microstructural characteristics was designed.Micro-circular holes were machined on the cavity by micro-EDM technology,and insert structure was adopted to make the die easy to be replaced.2.Based on the method of single factor test,the effects of mold temperature,injection rate and injection pressure on filling rate of micro-structure with different sizes were studied.The filling rate of micro-feature products can be increased by increasing the temperature,injection rate and injection pressure of the mold.3.The influence of die temperature,injection rate and injection pressure on flow imbalance in the forming process of micro-structure with different sizes was studied.4.Optimizing the runner system,the replaceable square groove and spherical groove inserts were designed at the diversion point.The influence of two runner systems on the imbalance was studied.5.The numerical simulation of injection molding product was carried out.The filling process was simulated by using finite element analysis software,which further revealed the reason for the imbalance of melt filling.