A numerical model that incorporates temperature-dependent non-Newtonian viscosity was developed to simulate the extrusion process in extrusion-based additive manufacturing. Agreement with the experimental data was achieved by simulating a polylactic acid melt flow as a non-isothermal power law fluid using experimentally fitted parameters for polylactic acid. The model was used to investigate the temperature effect on the flow behavior, the cross-sectional area, and the uniformity of the extruded strand. OpenFOAM, an open source simulation tool based on the finite volume method, was used to perform the simulations. A computational module for solving the equations of non-isothermal multiphase flows was also developed to simulate the extrusion process under a small gap condition where the gap between the nozzle and the substrate surface is smaller than the nozzle diameter. Comparison of the strand shapes obtained from our model with isothermal Newtonian simulation, and experimental data confirms that our model improves the agreement with the experimental data. The result shows that the cross-sectional area of the extruded strand is sensitive to the temperature-dependent viscosity, especially in the small gap condition which has recently increased in popularity. Our numerical investigation was able to show nozzle temperature effects on the strand shape and surface topography which previously had been investigated and observed empirically only.

Purpose The purpose of this paper is to study the flexural behavior of additively manufacture Ultem 1010 parts. Fused deposition modeling (FDM) process has become one of most widely used additive manufacturing methods. The process provides the capability of fabricating complicated shapes through the extrusion of plastics onto a print surface in a layer-by-layer structure to build three-dimensional parts. The flexural behavior of FDM parts are critical for the evaluation and optimization of both material and process. Design/methodology/approach This study focuses on the performance of FDM solid and sparse-build Ultem 1010 specimens. Flexure tests (three-point bend) are performed on solid-build coupons with varying build orientation and raster angle. These parameters are investigated through a full-factorial design of experiments (DOE) to determine optimal build parameters. Air gap, raster width and contour width are held constant. A three-dimensional nonlinear finite element model is built to simulate the flexural behavior of the FDM parts. Findings Experimental results include flexure properties such as yield strength and modulus, as well as analysis of the effect of change in build parameters on material properties. The sparse-build FDM parts chosen from the experimental tests are simulated based on this developed model. Thermo-mechanical simulation results show that the finite element simulation and experimental tests are in good agreement. The simulation can be further extended to other complicated FDM parts. Originality/value From the DOE study, sparse-build coupons with specific build parameters are fabricated and tested for the validation of a finite element simulation.

Researchers looking to improve the surface roughness of acrylonitrile butadiene styrene (ABS) parts fabricated by fused deposition modeling (FDM) have determined that acetone smoothing not only achieves improved surface roughness but increases compressive strength as well. However, the sensitivity of ABS parts to acetone smoothing has not been explored. In this study we investigated FDM-fabricated ABS lattice structures of various cell sizes subjected to cold acetone vapor smoothing to determine the combined effect of cell size and acetone smoothing on the compressive properties of the lattice structures. The acetone-smoothed specimens performed better than the as-built specimens in both compression modulus and maximum load, and there was a decrease in those compressive properties with decreasing cell size. The difference between as-built and acetone-smoothed specimens was found to increase with decreasing cell size for the maximum load.

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