This thesis investigated how different infill patterns and densities affect the compressive behavior of 3D printed Thermoplastic Polyurethane (TPU) structures. The study started with a literature review, followed by detailed chapters covering failure types, sample preparation, compression testing, and result analysis. Common failure modes in 3D printed structures are categorized into mechanical, structural, print quality, and material-specific issues, primarily caused by improper parameters or incompatible designs. These insights guided the accurate preparation of samples in the next phase. Cylindrical specimens were designed according to ASTM D575-91 using SolidWorks and printed using an FDM printer with six different infill patterns and two density levels. In total, 36 samples were tested under compression of 2 mm and 10 mm using the INSTRON 68TM-10 machine. Data such as maximum force, displacement, and dimensional changes were recorded. Stress-strain curves were generated to show how different infill settings impacted compressive strength. Error functions confirmed the consistency of results, supporting repeatability. The study concluded that higher infill densities generally led to greater resistance to deformation, and infill type had a significant effect on mechanical behavior.