Browsing by Subject "2023 Solid Freeform Fabrication Symposium"

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2023 International Solid Freeform Fabrication Symposium Preface and Organizing Committee
(University of Texas at Austin, 2023) University of Texas at Austin
A comparison of mechanical properties from natural and process-induced interfaces in filament extrusion AM of polymer blends
(University of Texas at Austin, 2023) Chatham, Camden A.; Benza, Donald W.
Polymer blends are commonly tuned for specific applications to achieve desired properties otherwise inaccessible or prohibitively expensive to obtain via homopolymers. The interfacial characteristics of the polymer A-polymer B interface and resultant domain sizes govern key performance properties. Micro- and meso-scale morphology forms through the interplay of surface forces between the polymers and between each polymer and the surrounding atmosphere. Analogously, the layer-layer and road-road interfaces of material extrusion (MEX) additive manufacturing (AM) govern key performance properties of printed parts. This work explores the effect of layer height on the thermomechanical performance of polystyrene (PS)-polycarbonate (PC) blends. Filament is prepared from a 50/50 weight ratio of the two polymers and compared against dual-nozzle printing where every layer alternates between PS or PC homopolymer forming a part with an overall 50/50 polymer ratio. Typical indicators of polymer blend compatibility are also studied.
Analysis of Flow Additives in Laser-Based Powder Bed Fusion of Polymers: Implications for Flow Behavior, Processing, Temperature Profile, and Part Characteristics
(University of Texas at Austin, 2023) Cholewa, S.; Jacksch, A.; Drummer, D.
Powder bed fusion of polymers requires the use of flow additives to ensure adequate flowability of the feedstock material. However, information regarding flow additives and their load is limited, as is an understanding of their impact on processing conditions. This study investigates the flow behavior using static and dynamic measurements under process conditions, focusing on the influence of flow additives. Subsequently, processing studies are conducted using thermography to analyze the laser-material interaction. The characteristics of parts produced from Polypropylene and Polyamide 12 systems are also examined. The findings of this research enhance the understanding of the impact of flow additives on the processing conditions of laser-based powder bed fusion of polymers, potentially leading to optimized process parameters and improved part quality and mechanical properties.
Benchmarking the Tensile Properties of Polylactic Acid (PLA) Recycled Through Fused Granule Fabrication Additive Manufacturing
(University of Texas at Austin, 2023) Al Nabhani, Dawood; Kassab, Ali; Habbal, Osama; Mohanty, Pravansu; Ayoub, Georges; Pannier, Christopher
To progress toward a circular economy of thermoplastic polymers, the adoption of 3D printers to make functional articles can facilitate distributed recycling. To this end, the mechanical degradation of polymers through multiple recycling cycles must be quantified. This work presents a procedure and benchmark dataset of tensile property degradation for polylactic acid (PLA) feedstock in multiple recycling passes with a fused granule fabrication process. To establish recycling with minimal processing (shredding and sieving), modifications were required to the granule feeding hopper of the 3D printer. Two distinct orientations were chosen to obtain tensile test coupons. These coupons were die-cut from machined 3D printed rectangular cross-section tubes, with one orientation along the bead (0°) and the other perpendicular to it (90°). Tensile properties are presented for 3D printed virgin material and one, two, three, and four passes of recycling. In terms of print orientation, the results indicate that samples pulled at 0° and 90° exhibited similar mechanical properties. However, there was an average decrease of 3.1% in ultimate tensile strength and a 1.7% decrease in elastic modulus for the samples along 90° orientation for all recycling passes. The samples along 0° demonstrated a 13.7% higher strain at fracture compared to those along 90°. Regarding the number of recycling passes, the findings suggest that the mechanical characteristics of PLA remain largely unaffected even after undergoing four recycling cycles. However, when the material is pulled in the direction of the bead, a 3.09% decrease in ultimate tensile strength is observed in the fourth recycling pass. The elastic modulus and strain at fracture did not exhibit a clear trend. It is important to note that the testing results display some variability, which can be attributed to a combination of stochasticity in the printing process and the preparation procedure employed.
DETERMINATION AND COMPENSATION OF THE SHRINKAGE BEHAVIOR OF CYLINDRICAL ELEMENTS IN THE FDM PROCESS
(University of Texas at Austin, 2023) Koers, T.; Magyar, B.
Fused Deposition Modeling (FDM) is an additive manufacturing process to produce complex thermoplastic geometries layer by layer. The filament is melted in a nozzle, iteratively deposited, and then cools down. Due to the solidification process, the deposited filament strands deviate from their intended position due to shrinkage, resulting in significant geometric deviations in the final part. In terms of dimensional accuracy, there is a need for optimization, especially for local curved geometries in relation to the global part with higher nominal dimensions. The aim of this study is to investigate the size and shape deviations for cylindrical FDM elements and to compensate the expected deformations by using an in-house software with adaptive scaling factors in the x-y plane. Previous studies mainly focus on simple, non-curved objects, this study also considers the influence of curvature and global as well as local deviations on the final part.