Study Of Ultrasonic-assisted Injection Molding Quality For Rectangular Micro Groove In Plastic Parts

With the rapid development of Micro-Electro-Mechanical System(MEMS)technology,micro injection molding parts have been widely used in biomedicine,environmental engineering,detection technology and other fields for its advantages of short production cycle,excellent performance and low cost.In micro-injection molding,the fluidity of the polymer melt in the microstructure of the cavity is poor,which leads to low duplication precision and large opening angle of the micro groove in the plastic parts,which affects the quality of the plastic parts.In this paper,microfluidic chips in micro-injection molding are selected as research objects,ultrasonic is introduced into micro injection molding and the effect of ultrasonic on micro injection molding is explored.Firstly,according to the structure of flat part,the ultrasonic assisted injection mold is made,which two sides of cavity are nickel plate microstructure and ultrasonic tool.According to the half wave resonance length of horn,verify the rationality of using single horn in this mold.Modal analysis is used to select the similar frequency of horn and tool as the working frequency of ultrasonic system.The amplitude of the piezoelectric ceramics and the magnification of the horn are obtained by the natural vibration analysis and harmonic response analysis respectively.Thus,the theoretical frequency and amplitude of the ultrasonic system are obtained.The stress analysis of the ultrasonic system is carried out.The numerical simulation of cavitation of polymethyl methacrylate(PMMA)melt is carried out by using the parameters of ultrasonic system in this paper.Secondly,5 factors(injection speed,injection pressure,melt temperature,ultrasonic power and ultrasonic time)and 3 horizontal injection molding orthogonal experiment is designed.The influence of injection molding parameters and ultrasonic parameters on the replication degree of micro groove in parts is analyzed,and the optimum molding parameters of microfluidic chip are obtained,according to it,single factor experiment is designed.The relationship between the ultrasonic power and the molding quality of micro groove of microfluidic chips in different directions and different positions is studied.Finally,the ultrasonic assisted injection mold is improved,and the visualization structure of the reflective observation is designed.The two sides of the mold cavity are the visualization structure and the ultrasonic tool with micro structure by electrical discharge machining(EDM).Force analysis of quartz glass in visualization structure is carried out.A visualization platform is built according to the operating space of the injection molding machine,and the long distance microscope and lens are selected.According to the visualization experiment,the filling process of the polymer melt with ultrasonic in two cavities with longitudinal and transverse microstructures is analyzed.The width of the incomplete filling area is proved to be the opening width of the micro groove in parts,and the changing curve of the opening width of the micro groove in the filling process is plotted,and the dynamic molding process of micro groove is analyzed.