Abstract
Fused Deposition Modeling (FDM) is often used for prototyping, and Injection Molding (IM)is used for mass producing parts. This study investigates the tensile loading of FDM parts in both the X and Z orientations while using specific process parameters such as 100% infill density, 0.2mm layer height, and a rectilinear filament deposition pattern on the Bambu Lab P1S, when compared to IM parts and see if they can accurately represent each other. Numerical analysis on an FEA software is done to predict the stresses that can be distributed within the cross-section of the specimen for both FDM and IM parts. The materials used in these experiments are Acrylonitrile Butadiene Styrene (ABS), Polylactic Acid (PLA), and Polyethylene Terephthalate Glycol (PETG). ASTM D638 standard was followed with all specimens fabricated to be the dimensions for dog bone type 1. The SATEC Universal Testing Machine (UTM) was used to conduct the testing of the polymers, and for Injection molding, experimental data was grabbed from literature and manufacturer data sheets. Since FDM 3D printed parts are anisotropic, it was found that the X build for PLA, ABS, and PETG was stronger than the Z build by 24.63%, 42%, and 127.9%, respectively. This was due to the X build having stronger interlayer adhesion when the load is parallel to the deposited filament layers. Injection molded counterparts for PLA, ABS, and PETG were stronger by 58.7%, 42.6%, and 12.3%. PETG had the closest performance when compared against injection molded PETG pellets. The FEA analysis for PLA, ABS, and PETG had a % error of less than 5% for both injection molded and FDM parts. FEA analysis did have a fillet stress concentration bias due to the fillet localizing a higher stress concentration in the shoulder gauge region of the specimens. In reality the specimens are created to break in the thinnest cross-sectional region of the specimen, which is the midpoint. ABS ,PLA, and PETG showed the most ductility in the X build direction while these polymers had a brittle fracture mode in the Z direction due to poor interlayer bonding shown during the microscopic analysis. The experimental results show that FDM modeling whether in the X or Z build cannot be an accurate representation of injection molded parts when it comes to tensile strength and FEA simulations are dependable. Tensile strength is also the greatest when the loading is parallel to the filament layers. And weakest when the loading is perpendicular to the filament layers.