GOALI: Adaptive Fused Filament Fabrication (AFFF)

增材制造（AM），通常被称为3D打印，是一种用于生产复杂结构的制造工艺，这些结构要么无法以其他方式实现，要么只能使用传统的减材制造工艺以大量浪费来实现。增材制造在其应用中非常广泛，并影响着汽车、航空航天、医疗产品和国防等行业。AM的一种常见形式是熔丝制造（FFF），其中熔融材料被挤出并逐层图案化以形成部件。这个赠款机会学术联络与工业（GOALI）项目研究新的FFF过程中使用传感器和建模来观察，表征和控制熔融材料，因为他们正在处理。这项工作将与增材制造技术的世界领导者Stratasys合作，以协助机械和材料研究。 该研究将广泛影响美国的竞争力和环境保护，使产品能够比目前的AM或替代制造工艺更快，更一致地生产。该项目的成功实施将通过实现新材料的3D打印，提高3D打印产品的制造吞吐量和质量，并为制造产品提供持续的质量保证，支持美国的创新和独创性。本研究将通过测试两个假设来研究FFF中聚合物流变学和所得部件特性之间的基本联系：1）熔体粘度可以基于上游电机扭矩和速度准确地确定，以及; 2）在知道熔体粘度的情况下，可以预测聚合物在长丝焊缝上的扩散程度。测试这些假设需要了解在FFF工艺的非等温、非稳态条件下聚合物的流变行为，以及流变行为如何影响打印结构的物理和机械性能。本课题的主要研究任务有三个：1.使用FFF作为毛细管流变仪在线建模聚合物粘度; 2. FFF建模（包括零件属性预测）和自适应的基于模型的细丝挤出、焊接和固化控制; 3.使用先进的实验平台进行验证，该平台包括闭环步进电机以及仪表喷嘴。这项工作的根本影响在于使用先进的过程仪表提供的实时反馈的过程-结构-性能关系的建模。因此，该研究有望为基于其固有的非等温剪切稀化行为加工更广泛的聚合物提供指导。此外，通过考虑粘度与潜在分子形态之间的关系，本研究也将为如何开发用于FFF的新材料提供指导。通过GOALI合作伙伴Stratasys及其员工的参与，项目成果转化为商业相关产品/系统的工作大大增加。通过研究生和本科生参与研究以及NSF资助的增材制造中心SHAP 3D，确保在这一重要领域拥有更有能力和更知情的劳动力。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Additive manufacturing (AM), often referred to as 3D printing, is a manufacturing process for producing complex structures that either could not be otherwise achieved or which could only be achieved with significant waste using traditional subtractive manufacturing processes. Additive manufacturing is widespread in its applications and impacts industries such as automotive, aerospace, medical products, and defense. One common form of AM is fused filament fabrication (FFF) in which molten material is extruded and patterned layer-by-layer to form a part. This Grant Opportunities for Academic Liaison with Industry (GOALI) project investigates new FFF processes using sensors and modeling to observe, characterize, and control the molten materials as they are being processed. This will be done in collaboration with industry partner Stratasys, a world leader in AM technologies, to assist in the machinery and materials research. The research will broadly impact US competitiveness and environmental conservation by enabling products to be more rapidly and consistently produced than is possible today with current AM or alternative manufacturing processes. The successful implementation of this project will support American innovation and ingenuity by enabling the 3D printing of new materials, increasing the manufacturing throughput and quality of 3D printed products, and providing continuous quality assurance for manufactured products. This research will investigate the fundamental linkages between polymer rheology and resulting part properties in FFF by testing two hypotheses: 1) Melt viscosity can be accurately determined based on the upstream motor torque and speed, and; 2) The extent of polymer diffusion across the filament's weld can be predicted knowing the melt viscosity. Testing these hypotheses necessitates an understanding of polymer rheological behavior under the non-isothermal, non-steady state conditions of the FFF process, as well as how the rheological behavior affects physical and mechanical properties of a printed structure. There are three major research tasks in this project: 1. On-line modeling of the polymer viscosity using the FFF as a capillary rheometer; 2. FFF modeling (including part property predictions) and adaptive, model-based control of the filament extrusion, welding, and solidification; 3. Validation using an advanced experimental platform that includes a closed loop stepper motor as well as an instrumented nozzle. The fundamental impact of this work lies in the modeling of processing-structure-property relationships using real-time feedback provided by advanced process instrumentation. The research is thus expected to provide guidance for processing a wider range of polymers based on their inherent non-isothermal, shear thinning behavior. Moreover, by considering the relationship between the viscosity and underlying molecular morphology, this research will also provide guidance in how to develop new materials for FFF. The translation of project results to commercially relevant products/systems is greatly increased through the participation of the GOALI partner Stratasys and its employees. A more capable and informed workforce in this important area is ensured through the participation of graduate and undergraduate students in the research as well as the NSF-funded center for additive manufacturing, SHAP3D.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.