Characterization of die-swell in thermoplastic material extrusion

Colon, Austin R.; Kazmer, David O.; Peterson, Amy M.; Seppala, Jonathan E.

doi:10.1016/j.addma.2023.103700

Cited by 4 publications

(4 citation statements)

References 62 publications

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“…The actual porosities of all scaffolds are slightly lower than the designed theoretical porosity (~50%), as shown in Table S2 . The reason is due to the expansion swelling effect, which is a common phenomenon in the melt extrusion of polymer materials [ 38 ]. In the FDM printing process, when the polymer material is extruded from the hot nozzle, the melt exhibits an expanded state, leading to an increase in the size of the extruded filament.…”

Section: Resultsmentioning

confidence: 99%

Magnesium Hydroxide as a Versatile Nanofiller for 3D-Printed PLA Bone Scaffolds

Guo,

Bu,

Mao

et al. 2024

Polymers

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Polylactic acid (PLA) has attracted much attention in bone tissue engineering due to its good biocompatibility and processability, but it still faces problems such as a slow degradation rate, acidic degradation product, weak biomineralization ability, and poor cell response, which limits its wider application in developing bone scaffolds. In this study, Mg(OH)2 nanoparticles were employed as a versatile nanofiller for developing PLA/Mg(OH)2 composite bone scaffolds using fused deposition modeling (FDM) 3D printing technology, and its mechanical, degradation, and biological properties were evaluated. The mechanical tests revealed that a 5 wt% addition of Mg(OH)2 improved the tensile and compressive strengths of the PLA scaffold by 20.50% and 63.97%, respectively. The soaking experiment in phosphate buffered solution (PBS) revealed that the alkaline degradation products of Mg(OH)2 neutralized the acidic degradation products of PLA, thus accelerating the degradation of PLA. The weight loss rate of the PLA/20Mg(OH)2 scaffold (15.40%) was significantly higher than that of PLA (0.15%) on day 28. Meanwhile, the composite scaffolds showed long-term Mg2+ release for more than 28 days. The simulated body fluid (SBF) immersion experiment indicated that Mg(OH)2 promoted the deposition of apatite and improved the biomineralization of PLA scaffolds. The cell culture of bone marrow mesenchymal stem cells (BMSCs) indicated that adding 5 wt% Mg(OH)2 effectively improved cell responses, including adhesion, proliferation, and osteogenic differentiation, due to the release of Mg2+. This study suggests that Mg(OH)2 can simultaneously address various issues related to polymer scaffolds, including degradation, mechanical properties, and cell interaction, having promising applications in tissue engineering.

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Section: Resultsmentioning

confidence: 99%

Magnesium Hydroxide as a Versatile Nanofiller for 3D-Printed PLA Bone Scaffolds

Guo,

Bu,

Mao

et al. 2024

Polymers

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“…System identi cation has been performed on roads deposited by material extrusion for control purposes, but not on signals collected during processing [40]. Transient behaviors have implications on the methods used to characterize materials and could affect the measurement of contact pressures [3,41], die-swell [42,43] and compressibility [2], which in uence the welding between the layers of deposited material [22] and their geometry. Understanding the transient behaviors present during extrusion will also provide support to efforts for sustainability [15,44], since designers can use these techniques to evaluate their systems relative to others, and to advanced processes that leverage standard material extrusion systems [45].…”

Section: Introductionmentioning

confidence: 99%

Transient modeling of material extrusion by system identification

Colon,

Kazmer,

Peterson

2023

Preprint

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Material extrusion is popular for its low barriers to entry and the flexibility it gives designers relative to traditional manufacturing techniques. Material extrusion is a transient process with a high frequency of starts, stops, and accelerations. This work presents transient data collected by an instrumented printhead and models the data by way of system identification. First-order and second-order control system models are proposed. The work also includes principal component analysis to determine which model coefficients correlate with the main effect, models the first-order model coefficients as a function of the experimental factors by regression, and predicts the apparent viscosity using a fitted static gain and known parameters. Flow rate, hot end temperature, nozzle diameter, and acceleration are the factors selected for the experiment. Each of these factors influences the steady state pressure, except for acceleration. The system identification models predict the melt pressure’s transient behavior well, with standard errors less than 4% of the mean melt pressure. Statistical analysis of the first-order model coefficients verifies that the static gain and time constant are statistically significant responses of the factors. The modeled apparent viscosity follows rheological expectations, showing the trends typically seen for viscosity as a function of shear rate.

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“…Die swell can be evaluated by swell ratio. The die swell ratio (DSR) is de ned as the radio between the extrudate diameter and the die diameter in most simple cases of capillary geometries [21,22].…”

mentioning

confidence: 99%

“…The authors also studied the in uence of the printing speed on the microstructure and surface quality of the PEEK parts. Colon et al (2023) [22] characterized the die swell effects in a MEX-AM based on solid lament mechanism of acrylonitrile butadiene styrene (ABS) polymer. They used a in-line instrumentation of optical and infrared cameras to estimate the swell ratio.…”

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confidence: 99%

Effects of extrusion parameters in the printing stability: evaluation in an innovative 3D printer containing a vertical co-rotating twin screw extrusion unit

Silva,

Barbosa,

Chinelatto

et al. 2024

Preprint

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The study of die swell phenomenon in Material Extrusion Additive Manufacturing (MEX-AM) technologies holds great importance in order to maintain the control over the extruded beads diameter to ensure surface quality, dimensional precision, adhesion between adjacent beads (intra and inter), as well mechanical properties on manufactured parts. This paper addresses an experimental procedure to analyze the influence of extrusion parameters on the die swell phenomenon on extruded beads printed from a 3D customized equipment containing a customized co-rotating vertical twin-screw extrusion unit (Co-TSE AM). In this context, an analytical estimation of shear rate in the screws and die was performed; a design of experiments (DOE) was conducted to evaluate the influence of factors as of screw rotational speed (40 rpm and 80 rpm), output rate (20 g/h and 40 g/h), and nozzle diameter (0.4 mm and 0.6 mm) on the die swell ratio (DSR); and scanning electron microscopy (SEM) was employed to assess the morphology in the cross-sectional area of the beads, as well as qualitative aspects of surface texture. Additionally, print line experiments were conducted to examine the influence of platform speed and standoff distance on bead width and bead height. It was observed that the DSR average varied between 1.28 and 1.67. Output rate and nozzle diameter are the parameters that most strongly influence DSR. Screw rotational speed has not significant influence on the thermomechanical environment that influences material swelling. The bead width and bead height are differently influenced by the standoff distance and print platform speed.

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Characterization of die-swell in thermoplastic material extrusion

Cited by 4 publications

References 62 publications

Magnesium Hydroxide as a Versatile Nanofiller for 3D-Printed PLA Bone Scaffolds

Magnesium Hydroxide as a Versatile Nanofiller for 3D-Printed PLA Bone Scaffolds

Transient modeling of material extrusion by system identification

Effects of extrusion parameters in the printing stability: evaluation in an innovative 3D printer containing a vertical co-rotating twin screw extrusion unit

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