The Research Of Differential System And The Forming Process

Micro injection molding has great potential in the field of injection technology. Throughout the history of micro injection molding technology, it has been mainly applied in the micro-injection molding machine. Although the project has achieved some results, yet owing to the deficiency of structural complexity and the difficulty in production, plus being influenced by the strength of screw and plunger, miniaturization of micro injection molding machine has been greatly restricted.Based on the melt differential principle, the planetary melt pump was introduced into the field of micro injection, completes the design of system-critical mechanical structure and the forming process, and succeeds in developing a differential injection molding machine. Experimental analysis of technologic performance and molding properties of the differential injection molding machine has been carried out. With the use of Moldflow simulation software, evaluations have been made on the melt state and the molding properties of the differential system. In the molding experiment of representative micro products, a micro gear of only 0.0115g with sharpness edge and great surface quality has been successfully produced. Through studying the filling rate of the micro gear and factors that influence the micro structure replication fidelity, grasped the basic law of differential injection molding technology and accumulated valuable experience for the parameters setting of molding micro products. Based on the above-mentioned work, the paper has made the following findings:(1) In order to improve the pressure response properties of the differential system, innovatively proposed a technical solution of constant pressure cut-off at the nozzle end to achieve effective control of the melt state. On the basis of it, the paper proposes the injection technique of system secondary pressurized injection and the cooling technique of intermittent supplying cooling water, which have achieved continuous automatic production of differential injection molding and greatly improved the molding precision and the product quality stability of differential injection molding;(2) By conducting a systematic research on the pressure response properties and the temperature distribution law of the differential injection system, results show that the system has a stable and accurate pressurization effect. Under the condition of low-pressure, the relationship between the injection pressure and the injection volume of the flow channel is presented excellent linearity. The orthogonal experiment shows that major parameters that influence the system to build pressure are melt pump inlet pressure, nozzle temperature and melt pump speed. The study on temperature characteristics of the system shows that Lower melt pump temperature can improve Supercharging performance, high control precision and has a great heating rate during the Forming process;(3) With the use of Moldflow evaluations are made on the system molding performance and molding simulation of micro gear is conducted. It shows that the temperature and the pressure characteristics of the differential system meet the requirements of molding micro gear; under rated melt pump inlet pressure, melt pump speed can be properly raised to increase the injection rate without affecting the measurement accuracy; higher molding temperature can help improve the filling rate of molded products and keep buckling deformation within the allowable range;(4) The automatic molding of micro gear has been taken, after mastered the forming regularity and process characteristics, and successfully got the micro gear with sharpness edge and great surface quality. At the same time, set the filling rates and micro structure replication fidelity as the evaluation index, and select the optimized parameters of differential injection molding. Experiment shows that:The major parameters that influence the filling rate are nozzle temperature, pressure maintaining time, melt pump rotation speed and the molding pressure; The major parameters that influence micro structure replication fidelity are nozzle temperature, mold temperature, melt pump rotation speed and the pressure maintaining time.