Lemniscates fitting to the contour of thermoplastic filaments pairs during viscous sintering
Characterization of the viscous sintering of extruded filaments pairs (zein plasticized by 20w%glycerol used as model-biopolymer for Additive Manufacturing by Melt Extrusion ; T=120°C ; Extruded_Filament_Diameter≈2mm) : Successive lemniscates fitting to their evolving contour. - Sintering time [s] (Column#1); - Average values of the shape parameter B [-] and their associated standard deviations [-] (Columns#2 and #3, respectively), computed from lemniscate fitting in a polar coordinate system (Sowinski and Jasion, 2019); - Average values of parameter a [pixel] and their associated standard deviations [pixel] (Columns#4 and #5, respectively), issued from image analysis. With a=Lmax/2, Lmax being the maximal horizontal lenght of the white object (i.e., filaments pairs) on the segmented image (i.e., binary). Parameter a is used as the size coefficient for lemniscate fitting in a polar coordinate system (Sowinski and Jasion, 2019); - Average values of Lmax normalized as the sintering filaments size factor : Lmax/Lmax_initial [-] and their associated standard deviations [-] (Columns#6 and #7, respectively); - Average values of m^2 [-], derived from the parameter m of lemniscate used to fit particles viscous sintering in a Cartesian coordinate system (Hopper, 1984) and their associated standard deviations [-] (Columns#8 and #9, respectively).
Steps to reproduce
Zein powder with 20 w% glycerol added as plasticizer was extruded with a twin-screw microcompounder at 130°C (Chaunier et al., 2019). The extruded filaments were cut as cylinders with a constant length (Lenght_filament=5mm ; Diameter_filament≈2mm). An instrumented oven was designed for the sintering of two horizontally adjacent extruded filaments. The front is a transparent glass plate, while the back is equipped with three LEDs for the backlighting the thermoplastic filaments pair. A CMOS camera allows the acquisition of contrasted images (256 gray levels) of the cylinder’s cross-section (1 frame.s^-1) with an average resolution of about 200pixel.mm^-1. Cropping, segmentation and morphological image analysis are successively carried out on the raw acquired images to determine each point of the contour in (x, y) coordinates and to fit the adjusted lemniscates. Lemniscates are planar curves determined by parameters B and a in a polar coordinate system (Sowinski and Jasion, 2019), or by parameter m in a cartesian coordinate system (Hopper, 1984), allowing the determination of viscous sintering properties of the considered material.