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Title: Characterization of die-swell in thermoplastic material extrusion
Die-swell is a flow effect that occurs in polymer extrusion whereby the material experiences rapid stress and dimensional changes upon exiting the nozzle orifice. Material extrusion additive manufacturing is no exception, and this effect influences the final dimensions of the printed road and imparts residual stresses. Die-swell is measured via a custom test cell that uses optical and infrared cameras and an instrumented hot end with an infeed pressure load cell. The instrumented hot end is mounted onto a stationary extruder above a conveyor to simulate printhead translation at steady state conditions for a wide range of volumetric flow rates. Investigated factors for an acrylonitrile butadiene styrene (ABS) filament include volumetric flow rate (0.9 mm3/s to 10.0 mm3/s), hot end temperature setpoint (200–250 ◦C), and nozzle orifice diameter (0.25–0.60 mm). The die-swell increases as a function of the volumetric flow rate and shear stress but decreases as a function of the hot end temperature setpoint and nozzle orifice diameter. For modelling, an implementation of the Tanner model for die swell displays good agreement with experimental results. The model also demonstrates that the same proportionality constant, k_N1 , which relates first normal stress difference to shear stress, can be used for different nozzle orifice diameters with the same length to diameter ratios, and that kN1 increases as a function of hot end temperature setpoint as expected with the rheological concept of time temperature superposition.  more » « less
Award ID(s):
1914651
PAR ID:
10552490
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
NSF PAR
Date Published:
Journal Name:
Additive Manufacturing
Volume:
73
Issue:
C
ISSN:
2214-8604
Page Range / eLocation ID:
103700
Subject(s) / Keyword(s):
Material extrusion Die-swell Fused deposition modeling (FDM) Instrumentation Rheology
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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