In this study, it is aimed to design a printer which has fused deposition technology and determine experimentally the effect of infill percentage on the mechanical properties with samples produced on the printer. A Cartesian type and open source three dimensional printer was modelled. Mechanical test samples were printed at 10, 20, 30, 40 and 50% infill percentage of PET and PLA materials using a three-dimensional printer manufactured as a prototype. Using the obtained samples, uniaxial tensile tests, hardness and surface roughness values were measured. As a result of the measurements, the hardness values of PET and PLA materials were directly related to the infill percentage of the material, and the hardness of the materials increased as the filling percentage increased. It was observed that roughness and tensile values of PLA and PET materials were inversely related to each other and roughness and tensile strength values were observed in the opposite direction from 30% infill percentage to 10% and 20% infill percentage.