Crystallisation Dynamics in Large-Scale Extrusion Additive Manufacturing: An Analysis with and without Temperature...

Area of Science:

• Manufacturing Engineering
• Materials Science
• Polymer Processing

Background:

• Large-Scale Material Extrusion (LS-MEX) offers novel manufacturing capabilities but faces challenges with heat retention.
• Excessive heat can lead to insufficient strand strength, causing 'slumping', and affects microstructural changes like crystallization kinetics.
• These thermal effects impact the final product's macroscopic properties, including strength and stiffness.

Purpose of the Study:

• To investigate the influence of thermal energy on structural processes in Large-Scale Material Extrusion.
• To explore methods for controlling thermal profiles and microstructural changes in extruded materials.
• To correlate controlled thermal dynamics with targeted modifications of macroscopic material properties.

Main Methods:

• Numerical simulations of the Large-Scale Material Extrusion process for polyamide 6 with 40% carbon fibres (PA6 wt.%40 CF).
• Application of semi-empirical methods, specifically the Nakamura model, for analyzing crystallization kinetics.
• Integration of thermal simulations with crystallization analysis to predict material behavior.

Main Results:

• Adjusting process parameters and utilizing modification units allows for accurate control of the material's thermal profile.
• Precise control over microstructural processes, particularly crystallization kinetics, was achieved.
• The study determined the absolute degree of crystallization, showing an increase from the strand's outer interface towards the print bed.

Conclusions:

• Controlling thermal energy is crucial for mitigating slumping and enhancing component quality in LS-MEX.
• Combining thermal simulations with semi-empirical models provides a reliable method for predicting crystallization kinetics.
• The findings enable targeted modification of macroscopic material properties by managing thermal dynamics during LS-MEX.