Enhanced Dimensional Accuracy of Material Extrusion 3D-Printed Plastics through Filament Architecture

Abstract

Optimization of three-dimensional (3D) print conditions for material extrusion of plastics by fused filament fabrication typically involves trade-offs between mechanical properties and dimensional accuracy due to their orthogonal requirements. Increased polymer mobility improves the mechanical properties by chain diffusion to strengthen the interfaces between printed roads, but flow associated with the high polymer mobility leads to inaccuracies. Here, we describe the application of a model core–shell geometry in filaments to address these trade-offs and understand the material requirements to achieve improved dimensional accuracy. Systematic variation of the core with commercial polycarbonate-based plastics and a common high-density polyethylene (HDPE) shell illustrates that tensile properties obtained with these filaments are relatively insensitive to printing conditions and selection of the core polymer, but the dimensional accuracy of the printed part improves markedly as the glass transition temperature of the core polymer increases. The impact resistance of the core–shell-based parts is dependent on the selection of the core polymer with a significant decrease in impact resistance for the lowest modulus core examined. Although warping can be mostly mitigated with the core–shell filaments, the printed object is generally smaller than the digital source due to large volume change associated with HDPE crystallization. The dimensional accuracy is dependent on the solidification temperature and mechanical properties of the polymers comprising the filament, print conditions, and the local geometry of the object as quantified by layer-by-layer analysis of 3D scanned images of the printed objects. Both processing changes and some structures in the digital object that can degrade the dimensional accuracy are identified through this analysis. The core–shell filament structure represents a model geometry to understand the potential for the printing of polymer blends where separation of solidification temperatures in cocontinuous blends could provide a route to improve performance.

Effect of the nanoparticles on the morphology and mechanical performance of thermally blown 3D printed HIPS foams

“…The differences between the designed and actual dimensions were 0.2% (0.01 mm) in the x–y‐direction (diameter) and 5.5% (0.33 mm) in the z‐direction (height). Such inaccuracy is in line with other reports on FDM 3D printing 32 . The bubble formation occurred during 3D printing of nanocomposites even below the standard decomposition temperature of azodicarbonamide due to lowering the surface energy around the blowing agent grains when the NPs were added.…”

“…Such inaccuracy is in line with other reports on FDM 3D printing. 32 The bubble formation occurred during 3D printing of nanocomposites even below the standard decomposition temperature of azodicarbonamide due to lowering the surface energy around the blowing agent grains when the NPs were added. Thus, it was possible to achieve a porous structure even when 3D printing occurred at low-temperature conditions.…”

Dual Material Fused Filament Fabrication via Core–Shell Die Design

“…The use of amorphous PETG thermoplastic in the core helps to maintain the shape of the printed part and mitigates the stresses induced by the volume contraction as the HDPE shell crystallizes when the layers cool below its crystallization temperature of 118 °C (see Figure S4). , In addition, the crystallinity of HDPE is reduced to 63% when printed in a core–shell configuration with PETG in the core (see Figure S5). On top of the rheological advantages of using HDPE as a shell polymer, the layer height was set to be 33% smaller than the extrusion width to ensure proper contact between printed tracks and overcome surface tension.…”

Feasibility of Producing Core-Shell Filaments through Fused Filament Fabrication

“…ABS and PC polymers were considered for printing the filament due to their good compatibility and available PC–ABS blend filament on the market as a point of comparison. Since PC material is tougher than ABS, using it as a core can behave similarly to continuous fibres to reinforce the ABS shell [ 16 ]. The resulting filaments were printed as samples with flat orientation and evaluated for the tensile test.…”

“…Ai et al (2021) extended the work from [ 15 ] by studying the dimensional accuracy of core-shell filaments of bisphenol-A PC, copolymer PC (cPC), or PC-ABS core and HDPE shell produced in the same way. Through a higher solidification point, the core acts as a reinforcement, and the shell, due to the lower solidification temperature, offers increased mobility between printed cores, improving the mechanical properties [ 16 ].…”