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Nomenclature
3D = Three-dimensional;
AM = Additive manufacturing;
ABS = Acrylonitrile butadiene styrene;
ASTM = American Society for Testing and Materials;
CAD = Computer-aided design;
CI = Confidence interval;
COV = Coefficient of variation;
DIC = Digital image correlation;
FDM = Fused deposition modeling;
PC = Polycarbonate;
RP = Rapid prototyping;
SMP = Shape memory polymer; and
STL = Stereo lithography.
1.Introduction
Fused deposition modeling (FDM) is an additive manufacturing (AM) technique which works by a heated nozzle laying down molten material in layers to produce the desired part. FDM is one of the most common techniques used for three-dimensional (3D) printers and has become one of the most popular rapid prototyping (RP) techniques in the past decade. FDM works by taking a part designed by a computer-aided design (CAD) model exported as a stereolithography (STL) file and uploaded into a slicer program. The slicer program cross-sections the model into individual layers of a specified height and converts the desired height and other settings into G-Code to be read by the printer. The printer reads the G-Code, heats up a liquefier to the desired temperature to melt the polymer filament of choice and begins extruding the material. The printing filaments used for this study were acrylonitrile butadiene styrene (ABS) and polycarbonate (PC). These filaments are fed through the heated liquefier by two drive wheels, where the filaments are then melted and extruded through a nozzle onto the build platform. The heating and extrusion of the filaments to the specified diameter are all contained within the extrusion head which moves in the X-Y plane, depositing material on the build platform. A single line of material is called a road, and the deposition of multiple roads side-by-side produces a single layer of a 3D-printed part. After each layer is finished, the build platform moves down a specified Z or layer height, and the process repeats for the next cross-sectioned layer until the part is completed. Figure 1 illustrates this process and highlights some of the key parts within the extrusion head as well as the deposition of the extruded filament. The X- and Y-axes are on the horizontal plane, and the build platform moves vertically along the Z-axis.
3D-printing has increasingly progressed from a strictly prototyping...