A rheology roadmap for evaluating the printability of material extrusion inks

Rau, Daniel A.; Bortner, Michael J.; Williams, Christopher B.

doi:10.1016/j.addma.2023.103745

Cited by 7 publications

(4 citation statements)

References 38 publications

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“…The power-law model, which is based on the power-law scaling of the viscosity near the gel point, ,,,− ,− predicts the gel conversion and the scaling behavior of the material. The extent of reaction at the gel point, α gel , is of particular interest for material extrusion additive manufacturing of thermoset composites ,− and filament winding , because it indicates the transition to a viscoelastic solid state where the material becomes exponentially more resistant to structural collapse. Well-established methods exist to determine the α gel of thermosets, but these methods are difficult to apply to composite resins that exhibit yield stress.…”

Section: Introductionmentioning

confidence: 99%

Evaluating Models That Predict Epoxy Conversion Using Rheological Properties

Romberg,

Roberts,

Snyder

et al. 2024

ACS Appl. Polym. Mater.

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Simultaneous rheology and conversion measurements of neat and composite epoxy resins reveal that conventional models neither accurately nor fully describe the relationship between rheology and conversion. We find that models predicting thermoset conversion based on mixing rules of rheological properties are quantitatively inaccurate and do not account for chemical gelation. Models based on percolation theory and the divergence of the viscosity at the gel point are more accurate but valid only before the gel point. Here, we propose the use of the generalized effective medium (GEM) model, which incorporates the divergence of the rheological properties on both sides of the critical gel point. We show that the GEM model works well for both neat resins and filled systems, and the resulting parameters estimate the gel point and scaling behavior on either side of the sol−gel transition.

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Section: Introductionmentioning

confidence: 99%

Evaluating Models That Predict Epoxy Conversion Using Rheological Properties

Romberg,

Roberts,

Snyder

et al. 2024

ACS Appl. Polym. Mater.

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“…Studies on the evaluation process for the potential new printing materials have been also carried out [13,14]. A notable example is the printing of biomaterials [15].…”

Section: Introductionmentioning

confidence: 99%

Flexible actuation with intrinsic sensing for ram extrusion 3D printing

Suthithanakom,

Sithiwichankit,

Chaiprabha

et al. 2024

Int J Adv Manuf Technol

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Conventional actuation mechanisms used in liquid deposition modeling (LDM) technology limit the flow handling capability and the visibility of the printing materials’ properties. This work presents a flexible actuation system with intrinsic sensing for a ram extrusion printhead used in LDM technology. A mathematical model is used to design and simulate the printhead. The experimental results demonstrate the system’s ability to control the extrusion flow in two modes. The pressure control mode is favorable for the flow in a transient state such as flushing. The volumetric control mode provides a constant printed line width with less than 0.1-mm deviation between each tested material (biogel, chocolate fudge, and silicone sealant). A lower standard deviation for printed lines in the volumetric control mode indicates more precise line printing. The system also incorporates real-time monitoring of extrusion pressure and flow rate. The intrinsic capability to detect printing material properties is validated in both simulation and experiment. It provides valuable insights for further optimization of the printing process. The proposed system offers the advantage of improved pressure and flow control as well as the ability to monitor and respond to the properties of printing material.

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“…Direct ink writing (DIW) is a widely utilized method of 3D printing based on the room temperature extrusion of an 'ink'. 15,16 The requirements for a suitable ink include thixotropic behavior, and the ability to be cured after printing. DIW does not necessitate added heat, extending its suitability to temperature-sensitive materials, [17][18][19] including some that can provide desirable rheological modification 20,21 as well as induced porosity.…”

Section: Introductionmentioning

confidence: 99%