Additive manufacturing is gaining momentum into industrial applications where thermal management is one of the new areas to explore. There are commercial filaments that have added particulate that enhances thermal conduction, and this works evaluates their properties. A short experiment was conducted to better assess the thermal properties of infused filament fabricated disks to provide better computer simulations. Five filaments, PLA, copper-infused PLA, high carbon iron PLA, aluminum PLA, and Ice9 Flex TPU, were used to print two discs for each filament, aligned at 0° and 90° to the print bed. The materials were developed by The Virtual Foundry, Inc. and TCPoly, Inc. The thermal conductivity of the disks were obtained using a modified Lee’s Disk Method setup. The test sample disks are placed between two 0.50” brass pucks. The bottom metal disk is attached to a 125W resistive electrical 3.00” pad heater which is connected to a power supply for ease of use, and the top metal disk is passively cooled by the ambient air. Two FluxTeq PHFS-01 flux sensors are placed in the setup to be in contact with the bottom and the top of the test sample. Thermal paste is used to secure the sensors in place and promotes heat transfer. The placement of the sensors aimed to obtain the heat flux and temperature of the boundaries before the sample and after the sample. The calibration of these differential-temperature thermopile sensors was performed by FluxTeq at a heat flux range of 2200-2400 W/m². The disks are manufactured to be 3.00” in diameter, 0.25” in thickness, 100% rectilinear infill, two shells, and default Cura slicing settings. Sample disks were manufactured parallel (XY-orientation or flat) to the build plate and perpendicular (Z-orientation or vertical) to the build surface to explore the difference in orientation and material deposition. The setup was brought to steady-state, defined as a change of no greater than 0.5°C in 10 minutes, and the heat flux through the sensors as well as the temperatures at the boundaries was measured. The thermal conductivities of the disks are obtained using the heat flow rate equation.The thermal conductivity of the additively manufactured parts depends on the print orientation from the manufacturing process. The measured values of the thermal conductivities obtained in this experiment are consistent with previous work. The change in print orientation from Z-orient to XY-orient accounted for a 23.1 to 47.7% difference in thermal conductivity in all the test samples. No data was previously available in the literature for Ice9 Flex TPU, although it is advertised as having 8 W/m·K in the print direction and 2.5 W/m·K along the through-plane direction. Remarkably, this material provided better results than the filaments with metal particles. The obtained thermal conductivities are as follows, with Z-orientation sample results preceding XY-orientation sample results: 0.124 W/m·K (vertical) and 0.174 W/m·K for PLA (flat); 0.342 W/m·K (vertical) and 0.656 W/m·K for Cu PLA (flat); 0.242 W/m·K (vertical) and 0.293 W/m·K (flat) for Fe PLA; 0.334 W/m·K (vertical) and 0.435 W/m·K (flat) for Al PLA; and 1.494 W/m·K (vertical) and &nbsp;0.811 W/m·K (flat) for Ice9 TPU. There is variation between the two orientations due to the layer deposition since the slicing software is optimized for structural strength and not for thermal conduction. There is a large difference between the results for Ice9 Flex TPU along the through-plane when compared against the experimental results using the default slicing settings. This indicates a need to tailor the deposition orientation for enhanced thermal conductivity. This work presents the first report showcasing thermally conductive filaments and their thermal conductivities values.

Thermal Conductivity Measurement of Infused Filaments for Additive Manufacturing

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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