(777b) Modeling Flow Phenomena in Fused Filament Fabrication Geometry

Authors: 
Gilmer, E. L., Virginia Polytechnic Institute and State University
Miller, D., Virginia Polytechnic Institute and State University
Fallon, J., Virginia Polytechnic Institute and State University
Zawaski, C., Virginia Polytechnic Institute and State University
Pekkanen, A. M., Virginia Polytechnic Institute and State University
Long, T. E., Virginia Tech
Williams, C. B., Virginia Polytechnic Institute and State University
Bortner, M. J., Virginia Polytechnic Institute and State University
The additive manufacturing (AM) field has recently been growing at an exponential rate and is currently transitioning from prototype visualization to functional prototypes and end product development. One of the greatest hurdles to advancing AM is the lack of available materials that can be printed into usable components. Extrusion based additive manufacturing, also known as fused filament fabrication (FFF) and the trademarked name fused deposition modeling (FDM), is the most common method of AM and has the largest catalog of useable materials. However, far fewer options are available when compared to traditional manufacturing methods, which limits the mechanical and chemical properties of parts created by this process. We propose a screening process to efficiently expand the catalog of available materials and reduce the need for extended and expensive testing. The screening process considers the most common failure modes for material extrusion: filament buckling and annular backflow, and integrates a continuum based transport approach to describe the physics of material extrusion through common FFF geometries. Our approach successfully describes the backflow phenomenon, which has not been previously investigated or reported but has been observed as we are developing new materials for the FFF process, including ionomers. We demonstrate the sensitivity of backflow to a material’s viscosity, the feed rate, and system geometry. Using this approach, we are able to rapidly predict the ability of a polymer to successfully print in an FFF system based on a single experimental measurement and the system geometry. We present the sensitivity of process conditions to the potential for failure to guide process condition selection, including temperature and feed rate.