聚合物熔体微滴堆叠自由成形机理及调控机制

3D additive Manufacturing is an important research area of advanced manufacturing technology. From the prospect of the maximum output polymer products in the 3D printing field, the products are mainly processed by the Fused Deposition Modeling which has many shortages such as obvious stripes on the surface, low strength in the vertical direction, and difficulty in multi-material and multi-color mixed printing. However, Polymer melt micro-droplet stack has advantages in fabricating products with small size and high precision, and with multi-material and multi-color gradient. Therefore, it is necessary to study the freeform fabrication mechanism and regulation mechanism of Polymer melt micro-droplet stack. Based on the micro-droplet forming and stacking experimental system controlled by the high frequency needle valve in the hot runner, the inherent relationship between scale of melt micro-droplet and polymer characteristics will be studied; and micro-droplets-scale regulation mechanism of various polymer materials will also be established. What’s more, the morphological evolution and heat transfer of the melt micro-droplet will be studied during the micro-droplet forming and stacking process, with the dynamic evolution discipline of it in free forming state, including flowing, bonding and contraction revealed, and the precise regulatory mechanism of polymer melt micro-droplet stacking freeform fabrication illuminated; meanwhile, the online control method of polymer melt micro-droplet stacking freeform fabrication will be proposed. The research results will lay the scientific theory foundation for independent research and development of new 3D additive manufacturing equipment and forming control method.

3D增材制造是先进制造技术中的重要研究领域。从产量最大的高分子制品角度来看，制品主要采用熔丝沉积成形的方法加工，存在制品表面有明显条纹，垂直方向强度较弱，难以多材多色混合打印等不足。而采用熔体微滴堆叠自由成形的方式，具有制备小尺寸高精度制品及多材多色梯度制品的优势。因此，引出了聚合物熔体微滴堆叠自由成形机理及在线调控的问题。申请人通过热流道高频针阀微滴成滴及堆叠成形实验平台，研究熔体微滴成滴尺度与聚合物特性的内在联系，建立多种聚合物材料的微滴尺度调控机制；研究微滴成滴及堆叠过程中熔体微滴形态演变和热交换，揭示熔体微滴在自由堆积状态下的流动、粘结、收缩的动态演化规律，阐明聚合物熔体微滴堆叠自由成形的精密控制机理，提出聚合物熔体微滴堆叠自由成形的在线控制方法。该课题研究成果将为自主研发新型3D增材制造装备及其成形控制方法奠定科学理论基础。

针对熔融沉积3D打印技术精度低、打印耗材种类少等缺点，采用聚合物熔体微积分思想，成功研制了熔体微滴堆叠自由成形实验平台。.该平台创新采用精密螺杆式的物料塑化与供料原理、快速响应的开关阀式料流控制方式以及熔体压力闭环自平衡等关键技术，可实现各种材料的粒状形态直接打印成型，解决了现有熔融沉积3D打印对耗材种类和耗材形态存在限制的技术难题，耗材种类广、成本低。.以此为研究平台，主要研究内容和结论如下：1）研究了聚合物熔体微滴成滴与微滴尺度调控机理，发现聚合物熔体由于粘度大难以自由滴落，需通过被动微滴成形的方式进行微滴成滴，研究得到了聚合物微滴堆叠；.2）对聚合物熔体微滴成滴和堆叠过程的温度场进行了模拟分析研究，获知长方体薄板模型微滴堆叠成形温度场随微滴堆叠位置的移动而呈现动态变化，为微滴堆叠实验研究和工艺优化提供了理论基础；.3）对聚合物熔体微滴堆叠自由成形方法进行研究，研究发现熔体微滴堆叠可以降低打印制品的收缩率，影响聚合物熔体微滴堆叠成形精度的主要因素是液滴间距和成形路径；.4）研发成功成功工业级大型熔体微分3D打印设备，制备了一种适配熔体微滴堆叠自由成形实验平台具有高强度、可导电性能的MWCNTs/PLA复合材料，并在金属铸造领域替代木模方面进行了应用研究。.本项目发表学术论文23篇，其中SCI收录3篇；申请国家发明专利10项，授权5项。培养博士研究生1名，硕士研究生7名。研发成功的实验设备多次应邀参加了于中国橡塑展和上海TCT展览会，获得了国内外客商的广泛关注。