“…Interestingly, Coogan and Kazmer reported decreasing bond strength with increasing layer thickness for micro tensile bars laser cut from single road width walls 32 . This trend is attributed to a combination of decreased bond widths and reduced contact pressure 33 , 35 for larger layer heights, neither of which this thermal model accounts for. Figure 3 Modeling of a single-road width wall printing at a range of layer thicknesses with T ext = 230 °C, v print = 30 mm/s.…”
Mechanical properties of additively manufactured structures fabricated using material extrusion additive manufacturing are predicted through combining thermal modeling with entanglement theory and molecular dynamics approaches. A one-dimensional model of heat transfer in a single road width wall is created and validated against both thermography and mechanical testing results. Various model modifications are investigated to determine which heat transfer considerations are important to predicting properties. This approach was able to predict tear energies on reasonable scales with minimal information about the polymer. Such an approach is likely to be applicable to a wide range of amorphous and low crystallinity thermoplastics.
“…Interestingly, Coogan and Kazmer reported decreasing bond strength with increasing layer thickness for micro tensile bars laser cut from single road width walls 32 . This trend is attributed to a combination of decreased bond widths and reduced contact pressure 33 , 35 for larger layer heights, neither of which this thermal model accounts for. Figure 3 Modeling of a single-road width wall printing at a range of layer thicknesses with T ext = 230 °C, v print = 30 mm/s.…”
Mechanical properties of additively manufactured structures fabricated using material extrusion additive manufacturing are predicted through combining thermal modeling with entanglement theory and molecular dynamics approaches. A one-dimensional model of heat transfer in a single road width wall is created and validated against both thermography and mechanical testing results. Various model modifications are investigated to determine which heat transfer considerations are important to predicting properties. This approach was able to predict tear energies on reasonable scales with minimal information about the polymer. Such an approach is likely to be applicable to a wide range of amorphous and low crystallinity thermoplastics.
“…The term double domain means modelling specific volume as a function of pressure and temperature separately in the state of solid and melt. The term ν o ( T ) is the reference specific volume given by the expression (2) for temperature below the transition range: compressibility B ( T ) is given by (3), where b 1 , b 2 , b 3 , b 4 are material coefficients (Table 2) given by the p-v-T diagram for the polystyrene [34] while b 5 is the transition temperature at zero pressure.…”
Electroless plating is used to enhance the strength of anodised aluminium oxide (AAO) which can be further utilised as a mould to fabricate the structures on large area of polymer for antireflection properties. Nanopillars of high aspect ratio are fabricated on polymer (polystyrene) sheet by hot embossing process which has ensured repeatability with precision and high throughput. The height of nanopillars matches the depth of the mould cavity. The enhanced light trapping performance is attributed to the high aspect ratio nanopillars with cup-shaped top surface.
“…That being said, the custom hot end design shows better performance than a typical hot end design (see supplementary materials Section S.11). Hot end performance is critical because it affects the systems energy efficiency (Kazmer et al , 2023) and the material properties (Kazmer et al , 2021; Kim et al , 2021), which affect the final part’s properties.…”
Purpose
A main cause of defects within material extrusion (MatEx) additive manufacturing is the nonisothermal condition in the hot end, which causes inconsistent extrusion and polymer welding. This paper aims to validate a custom hot end design intended to heat the thermoplastic to form a melt prior to the nozzle and to reduce variability in melt temperature. A full 3D temperature verification methodology for hot ends is also presented.
Design/methodology/approach
Infrared (IR) thermography of steady-state extrusion for varying volumetric flow rates, hot end temperature setpoints and nozzle orifice diameters provides data for model validation. A finite-element model is used to predict the temperature of the extrudate. Model tuning demonstrates the effects of different model assumptions on the simulated melt temperature.
Findings
The experimental results show that the measured temperature and variance are functions of volumetric flow rate, temperature setpoint and the nozzle orifice diameter. Convection to the surrounding air is a primary heat transfer mechanism. The custom hot end brings the melt to its setpoint temperature prior to entering the nozzle.
Originality/value
This work provides a full set of steady-state IR thermography data for various parameter settings. It also provides insight into the performance of a custom hot end designed to improve the robustness of melting in MatEx. Finally, it proposes a strategy for modeling such systems that incorporates the metal components and the air around the system.
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