Research And Development Of Plastic Additive Manufacturing System Based On Droplet Jetting Technology

The additive manufacturing technology based on discrete-integral ideal has been showing a strong vitality and receiving extensive attention in various fields, because of its characteristics such as strong adaptability and short manufacturing cycle time. However, it not yet really gets a wide range of application in industrial applications, largely due to the types of useable material and the strength of molded parts is insufficient to satisfy the daily use. The additive manufacturing based on liquid droplet jetting technology is not limited by the type of raw material, also has the advantages of low cost and high performance of molded parts. But the droplet jetting forming of high viscosity materials is quite difficult, especially the additive manufacturing technology using general industrial plastic droplet still needs further research and development.Therefore, the study of plastic droplet jetting is of great significance to additive manufacturing technology.1. Because of the plastic melt has the characteristics of high temperature and high viscosity, a kind of mechanical jetting technology was applied. In this paper, the process of droplet jetting and melt breakup into droplet was analyzed in detail, and got a conclusion that the melt jetting velocity should be greater than the critical velocity.2. The dynamic characteristics of striker in the process of lifting and dropping were mainly analyzed, based on the mechanical jetting technology. The each parts of droplet jetting forming system were designed. To fulfill the function of forming system, built up the melt feeding unit, the high pressure oil unit, motion platform and temperature control unit. Finally, the completion of the forming system provides a hardware platform for the study of the formation mechanism and process research.3. To study the melt flow inside the nozzle and melt jetting process, the application of meshless numerical simulation software was used to simulate the internal cavity of the nozzle melt under the action of the striker lifting and dropping movement of the jetting by micropores and the whole process of breakup. The results can be found through the simulation, that the striker in the melt jetting process, not only acts as a switch valve, but also improve the instantaneous velocity in the time of melt breakup. The gap, the striker sear angle, pore diameter and the melt pressure have great impact on the maximum velocity and droplet volume. But the uses of high melt pressure helps reduce the impact of the striker movement and melt chamber dimensions.The pore diameter and length were selected as a structural design factors, melt pressure and pulse width were selected as the operating process factors, obtained by orthogonal experimental analysis of the pore diameter and the melt pressure is the most important influencing parameters.4. Droplet jetting molding experiment was conducted to study the impact of melt pressure, pulse width and pulse frequency on the average apparent diameter and mass of droplet. The results showed that the average apparent diameter is less affected by melt pressure, and the pulse width is proportional to the height of the droplet and curing angle increased; pulse frequency had a good linear inverse relationship with the average apparent diameter; the relationship between mass of droplet and melt feeding pressure and pulse width was proportional, while inversely proportional with the pulse frequency. At last, a three-dimensional part manufacturing was finished.