Numerical modeling of the strand deposition flow in extrusion-based additive manufacturing

Comminal, Raphaël; Serdeczny, Marcin P.; Pedersen, David Bue; Spangenberg, Jon

doi:10.1016/j.addma.2017.12.013

Cited by 136 publications

(159 citation statements)

References 37 publications

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“…These preliminary computations are in line with the previous results obtained by Comminal et al [11] showing that the thickness of the deposited layer is less than the gap e. The computational fluid dynamics (CFD) is a powerful tool in which multiphysics can be taken into account, for example a non-uniform temperature field at nozzle exit and a shear thinning behavior for the molten polymer. However, and even if the computing power is still increasing, the screening of design and working conditions stay a hard task in CFD.…”

Section: Model Descriptionsupporting

confidence: 90%

“…The polymer spreads laterally over a smaller distance than before as shown in Figure 7 and Figure 8. The minimum thickness of the deposited layer is equivalent to the previous case in agreement with the results of Comminal et al [11] but its shape is less regular and its width is reduced by more than a factor 2.…”

Section: Model Descriptionsupporting

confidence: 90%

“…The pressure will obviously greatly influence the filling of porosities and the welding with the previously deposited polymer. Recently, Du et al [10] and Comminal et al [11] have calculated the shape of the deposited layer and the pressure distribution between the moving printing head and the substrate using finite volume methods. Du et al [10] accounted for a Non-Newtonian temperature dependent behavior of the polymer, but the widening of the deposit during spreading remained limited.…”

Section: Introductionmentioning

confidence: 99%

“…Du et al [10] accounted for a Non-Newtonian temperature dependent behavior of the polymer, but the widening of the deposit during spreading remained limited. Comminal et al [11] used a Newtonian isotherm hypothesis and provided pressure distributions and deposit dimensions for different gaps between the head and the substrate and different fluid and printing head velocities. Xia et al [12] computed the deposit of successive layers.…”

Section: Introductionmentioning

confidence: 99%

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Flow analysis of the polymer spreading during extrusion additive manufacturing

Agassant

Pigeonneau

Sardo

et al. 2019

Additive Manufacturing

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The spreading of molten polymer between the moving printing head and the substrate in extrusion additive manufacturing is studied. Finite element computation and an analytical model have been used. The hypotheses of the analytical model are qualitatively justified by the results of the numerical computation. The analytical calculation is a powerful tool to rapidly evaluate the relationships between processing parameters (extrusion rate, printing head velocity, gap between the printing head and the substrate) and some characteristics of the deposition (dimensions of the deposited filament, pressure at the printing head nozzle, separating force between substrate and printing head). An isothermal hypothesis is discussed. The viscous non-Newtonian behavior is accounted for through an approximate shear thinning power law model. A printing processing window is defined following several requirements: a continuous deposit, without spreading in front of the printing head, maximum and minimum spreading pressures, an upper-limit for the separating force between head and substrate.

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Section: Model Descriptionsupporting

confidence: 90%

Section: Model Descriptionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Flow analysis of the polymer spreading during extrusion additive manufacturing

Agassant

Pigeonneau

Sardo

et al. 2019

Additive Manufacturing

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“…In fact, when small modifications on the scaffold geometry must be achieved, acting on process parameters of the traditional FDM technique can be a valid option instead of looking for expensive, more accurate technologies. A recent study proposed a numerical model to simulate the extrusion of a strand of semi-molten material to investigate how the strand cross-section changes for variable process parameters [25]. The porosity and the micro-architecture of parts built with the FDM technique appear very suited to stimulate the colonization and subsequent differentiation of mesenchymal stem cells [26].…”

Section: Introductionmentioning

confidence: 99%

Mechanobiological Approach to Design and Optimize Bone Tissue Scaffolds 3D Printed with Fused Deposition Modeling: A Feasibility Study

et al. 2020

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In spite of the rather large use of the fused deposition modeling (FDM) technique for the fabrication of scaffolds, no studies are reported in the literature that optimize the geometry of such scaffold types based on mechanobiological criteria. We implemented a mechanobiology-based optimization algorithm to determine the optimal distance between the strands in cylindrical scaffolds subjected to compression. The optimized scaffolds were then 3D printed with the FDM technique and successively measured. We found that the difference between the optimized distances and the average measured ones never exceeded 8.27% of the optimized distance. However, we found that large fabrication errors are made on the filament diameter when the filament diameter to be realized differs significantly with respect to the diameter of the nozzle utilized for the extrusion. This feasibility study demonstrated that the FDM technique is suitable to build accurate scaffold samples only in the cases where the strand diameter is close to the nozzle diameter. Conversely, when a large difference exists, large fabrication errors can be committed on the diameter of the filaments. In general, the scaffolds realized with the FDM technique were predicted to stimulate the formation of amounts of bone smaller than those that can be obtained with other regular beam-based scaffolds.

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Embedded 3D Printing of Thermally‐Cured Thermoset Elastomers and the Interdependence of Rheology and Machine Pathing

Stang

Tashman

Shiwarski

et al. 2022

Adv Materials Technologies

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polyether ether ketone (PEEK) can be directly printed into high-performance parts. [1][2][3][4][5] However, there are still large classes of materials that have been difficult to adapt to 3D printing. For example, thermally-cured thermosets such as epoxies and silicones are widely used in many applications for their combination of mechanical properties, chemical resistance, and thermal stability. [6] However, these polymers are often two-part systems that must be mixed and then take minutes to hours to crosslink and fully cure. These thermosets remain in a liquid state for a prolonged period and are thus challenging to 3D print with high fidelity because they flow and do not retain their intended geometry.Extrusion-based direct ink writing (DIW) has had success printing thermosets such as epoxies and silicones but typically requires modification of ink composition and rheological properties to make them thixotropic, or that are already thixotropic, to permit printing in air. [7,8] Additionally, DIW faces the same geometrical constraints that limit related fused deposition modeling (FDM) type approaches, such as overhangs and free-standing structures that are difficult to print without the use of support material. These constraints on the materials and geometries that can be 3D printed severely limit the complexity of parts that can be fabricated using slow-to-cure liquid prepolymers and soft materials.Freeform reversible embedding (FRE) 3D printing is a technique that was recently developed to print soft and liquid materials and overcome these challenges. [9] First described in separate papers by the Feinberg and Angelini groups in 2015, FRE and related embedded 3D printing techniques involve extruding prepolymers into a microgel-based support bath that possesses a yield stress. [10,11] Unlike typical FDM approaches in which the filament is extruded onto a platform, in FRE the material of choice (often referred to as the ink) is extruded directly into the support bath and held in place until it is cured. The support bath also greatly diminishes the effects of gravity and generally eliminates the need for any additional printed support structures. Despite these advantages, there are still challenges that are unique to the FRE process Thermoset elastomers are widely used high-performance materials due to their thermal stability, chemical resistance, and mechanical properties. However, established casting and molding techniques limit the overall 3D complexity of parts that can be fabricated. Advanced manufacturing methods such as 3D printing have improved design flexibility and reduced development time but have proved challenging using thermally-cured thermosets due to their viscosity, slow gelation kinetics, and high surface tension. To address this, freeform reversible embedding (FRE) 3D printing extrudes thermosets such as polydimethylsiloxane (PDMS) elastomer within a carbomer support bath, but due to the liquid-like state of the prepolymer during extrusion has been limited to hollow structures. Here, FRE printi...

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Numerical modeling of the strand deposition flow in extrusion-based additive manufacturing

Cited by 136 publications

References 37 publications

Flow analysis of the polymer spreading during extrusion additive manufacturing

Flow analysis of the polymer spreading during extrusion additive manufacturing

Mechanobiological Approach to Design and Optimize Bone Tissue Scaffolds 3D Printed with Fused Deposition Modeling: A Feasibility Study

Embedded 3D Printing of Thermally‐Cured Thermoset Elastomers and the Interdependence of Rheology and Machine Pathing

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