Steady Melting in Material Extrusion Additive Manufacturing

Published

July 5, 2023

Author(s)

Austin Colon, David Kazmer, Amy Peterson, Jonathan Seppala

Abstract

Purpose One of the main causes of defects within material extrusion additive manufacturing is the non-isothermal condition in the hot end, which leads to inconsistent extrusion and weld healing. This work validates a custom hot end design intended to melt the thermoplastic prior to the nozzle, to reduce variability in melt temperature, and presents a full 3D temperature verification methodology for hot ends. Design/methodology/approach Infrared 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. Simulation model tuning to estimate the effects of different model assumptions on the simulated melt temperature. Findings The experimental results show that the measured temperature and variance is as a function of volumetric flow rate, temperature setpoint and the nozzle orifice diameter. Convective heat transfer to the surrounding air has a significant effect. The dimensionless temperature shows 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 infrared thermography data for various nozzle orifice diameters, hot end temperature setpoints, and volumetric flow rates. It also provides insight into the performance of a custom hot end designed to improve the robustness of melting in material extrusion and proposes a strategy for modeling such systems.

Citation

Rapid Prototyping Journal

Pub Type

Journals

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Keywords

Purpose One of the main causes of defects within material extrusion additive manufacturing is the non-isothermal condition in the hot end, which leads to inconsistent extrusion and weld healing. This work validates a custom hot end design intended to melt the thermoplastic prior to the nozzle, to reduce variability in melt temperature, and presents a full 3D temperature verification methodology for hot ends. Design/methodology/approach Infrared 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. Simulation model tuning to estimate the effects of different model assumptions on the simulated melt temperature. Findings The experimental results show that the measured temperature and variance is as a function of volumetric flow rate, temperature setpoint and the nozzle orifice diameter. Convective heat transfer to the surrounding air has a significant effect. The dimensionless temperature shows 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 infrared thermography data for various nozzle orifice diameters, hot end temperature setpoints, and volumetric flow rates. It also provides insight into the performance of a custom hot end designed to improve the robustness of melting in material extrusion and proposes a strategy for modeling such systems.

Citation

Colon, A. , Kazmer, D. , Peterson, A. and Seppala, J. (2023), Steady Melting in Material Extrusion Additive Manufacturing, Rapid Prototyping Journal, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936451 (Accessed March 21, 2025)