Due to limited production numbers, using additive manufacturing for the production of railway components, is proving more economical. Furthermore, strict requirements regarding flammability properties, standardised in EN 45545-2, are applied on trains. This work focuses on the production of transparent components made of Polycarbonate via 3D-printing. The polymer was modified using different flame retardant agents and the influence of the printing parameters, especially the print density, was determined. Polylactic Acid was examined for comparison reasons only. The printed and modified polymers were tested exposing the samples to heat radiation, according to ISO 5660-1 using a Cone Calorimeter, and to a direct flame, according to UL 94. Processing and printing of the polymer causes thermal stress to the molecules. This may lead to a worsening of the flammability causing a decline of the properties compared to the native Polycarbonate. This was confirmed through both testing methods. Moreover, the additive and the print density both influence the flammability properties depending on the polymer type. In summary print parameters and additivation have to be carefully considered when it comes to the flammability properties of polymers.