Fused Deposition Modeling is one of the most commonly used additive technologies that is increasingly used to produce complex functional parts that can be used in realistic atmospheric and ambient conditions. Based on that and in accordance with the daily appearance of new materials, it is necessary to consider the conditions in which printed parts can exist without decreasing their mechanical properties, geometric and dimensional stability. The mechanical properties of printed parts are affected by many process parameters, so it is necessary to optimize them. In this paper, the influence of layer thickness, printing temperature and raster angle on the tensile strength of printed samples for two types of materials (PLA and carbon fibers reinforced polyamide) was analyzed. Mechanical testing of test samples was performed, which were previously exposed to simulated environmental conditions in which the given product will exist during its lifetime. Primarily, the influence of UV rays on the mechanical properties, geometric and dimensional stability of the printed parts was analyzed. Results shown that the tensile strength of the composite material decreases slightly after testing in the chamber in a time frame of 30 h that simulates 30 days of exposure in real atmospheric conditions, and that the PLA material in the same time frame significantly loses its dimensional and geometric stability, as well as decrease in tensile strength and ductility of the material.