A series of alternative materials are tested as the basis for use in 3D printing applications. Especially when the Fused Filament Fabrication (FFF) technology is selected, either for prototyping or manufacturing purposes, there is a need to combine low cost with increased mechanical properties. The present paper studies the tensile strength of a filament that integrates PLA and Cu-powder (65%). Three fabrication parameters were used (temperature, flow rate, layer height) with three levels each and a verified prediction model was developed. The high validity of the proposed model was proved by the analysis of variance and the analysis of the residuals.