Abstract
A method for image analysis was implemented to determine the edge pixels of two biopolymer-based thermoplastic filaments during their hot melt isothermal sintering at 120 °C. Successive inverted ellipses are adjusted to the contour of the sintered filaments and lead to the identification of the parameters of the corresponding lemniscates of Booth. The different steps of the morphological image analysis are detailed, from 8-bit coded acquired images (1 frame/s), to the final fitting of the optimized mathematical functions describing the evolution of the filaments envelope. The complete sequence is composed of an initial pure viscous sintering step during the first minute, followed by viscoelastic swelling combined with melt spreading for a longer time, and then the stabilization of the sintered filaments shape for over 2 min at high temperatures. Using a master curve obtained from Hopper’s abacus, the characteristic viscous sintering time is assessed at tvs = 78 s, confirming the one previously found based on the measurement of the bonding neck length alone. Then, the full description of the evolution of the thermoplastic filaments envelope is assessable by image analysis during sintering trials as a result of its digital modeling as successive lemniscates of Booth, reflecting geometry changes in the molten state.
Highlights
This study deals with the modeling of the viscous sintering of thermoplastic filaments based on a 3D printable biopolymer processed in the molten state
The author gave an exact analytic solution of the plane-flow case where capillarity drives the evolution of the shape of the two cylinders’ profile as a function of the sintering time. Starting from this assumption, we propose using the viscous sintering of thermoplastic filaments as a model case to demonstrate the ability of the lemniscates of Booth to fit the contour of the local cross-section and to drastically enhance previous approaches only based on bonding neck length
The ability of lemniscates of Booth to describe the contour of the crosssection of a pair of thermoplastic 3D printing filaments has been demonstrated in the model case of viscous sintering
Summary
This study deals with the modeling of the viscous sintering of thermoplastic filaments based on a 3D printable biopolymer processed in the molten state. The author gave an exact analytic solution of the plane-flow case where capillarity drives the evolution of the shape of the two cylinders’ profile as a function of the sintering time. Starting from this assumption, we propose using the viscous sintering of thermoplastic filaments as a model case to demonstrate the ability of the lemniscates of Booth to fit the contour of the local cross-section and to drastically enhance previous approaches only based on bonding neck length
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