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，这些结构要么无法通过其他方式实现，要么只能使用传统的减法制造工艺以大量浪费的方式实现。增材制造在汽车、航空航天、医疗产品和国防等行业有着广泛的应用和影响。增材制造的一种常见形式是熔融长丝制造（FFF），其中熔融材料被挤压并逐层成形以形成零件。这个学术联络与工业（GOALI）项目的资助机会研究了新的FFF工艺，使用传感器和建模来观察、表征和控制正在处理的熔融材料。这将与行业合作伙伴Stratasys合作完成，Stratasys是增材制造技术的全球领导者，协助进行机械和材料研究。这项研究将广泛影响美国的竞争力和环境保护，使产品的生产比目前的增材制造或替代制造工艺更快、更一致。该项目的成功实施将支持美国的创新和独创性，使新材料的3D打印成为可能，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。本研究将通过测试两个假设来研究聚合物流变学与FFF中产生的零件性能之间的基本联系：1)熔体粘度可以根据上游电机扭矩和速度精确确定；2)通过熔体粘度可以预测聚合物在长丝焊缝上的扩散程度。要验证这些假设，就必须了解聚合物在FFF过程的非等温、非稳态条件下的流变行为，以及流变行为如何影响打印结构的物理和机械性能。本项目主要有三个主要的研究任务：1。用FFF作为毛细管流变仪对聚合物粘度进行在线建模2. FFF建模（包括零件性能预测）和自适应，基于模型的控制长丝挤压，焊接和凝固；3. 使用先进的实验平台进行验证，该实验平台包括闭环步进电机和仪表喷嘴。这项工作的基本影响在于利用先进的过程仪器提供的实时反馈对过程-结构-属性关系进行建模。因此，该研究有望为基于其固有的非等温剪切变薄行为的更广泛聚合物的加工提供指导。此外，通过考虑黏度与底层分子形态之间的关系，本研究也将为如何开发FFF新材料提供指导。通过GOALI合作伙伴Stratasys及其员工的参与，将项目结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SHAP3D，确保了这一重要领域更有能力和知情的劳动力。该奖项反映了美国国家科学基金会的法定使命，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.