GOALI: Adaptive Fused Filament Fabrication (AFFF)

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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.