Study On Mechanism And Application In Precision Injection Molding Of Microstructures Assisted By Ultrasonic Vibration

Micro injection molding finds more and more attention and applications in the biomedical, micro-optics and micro-sensors. The requirements of complex degree, precision and efficiency in micro injection parts are also increased gradually. In actual processing, being short of theory guidance, it has become a difficulty in producing complex or high aspect ratio features in injection molding. Based on present injection molding technology, we introduced ultrasonic vibration into injection molding. Using numerical simulations and molding process experiments, the flow properties of polymer with ultrasonic vibration and the molding quality were studied, all of which are momentously theoretical and practical significance on the micro injection molding and on improving the quality of micro plastic parts.According to the fundamental theories of viscous fluid dynamics, heat transfer theory and polymer rheology, the basic equations for flow of polymer melt with ultrasonic vibration were constructed with the reference of the research methods of conventional flow. The flow properties of polymer with ultrasonic vibration were studied with experimental test and numerical analysis. In addition, it was carried out that the research of micro injection molding theory and injection molding processing.An ultrasonic-assisted polymer extrusion measurement system was developed and used to ultrasonic-assisted extrusion experiments. By experimental comparison between this method and the traditional models, it is found that after the introduction of ultrasonic vibration, micro-channel inlet pressure drop decreased obviously; Polymer viscosity under the action of the ultrasonic is smaller than the traditional steady-state viscosity. The efficiency of ultrasound decreased with the rising of length of micro channel.The microstructure of micro-needle array for molding process experiments was designed and fabricated. The results show that micro injection molding with ultrasound can improve the quality of the micro-needle array injection parts. Then with orthogonal experiment design method the molding experiments for micro-needle array were performed. The influence sequence and optimal level combination of process parameters were obtained by the analysis of means and the analysis of variance, and using the different structures of micro-needle array it was analyzed that the influencing rules of ultrasonic, mold temperature, injection speed and holding pressure were gained under the condition of considering the forming quality of micro-needle array injection parts, thus provides the theoretical basis for actual injection molding of the micro-needle array.