3D printing is the process of making a product, layer by layer. It encompasses various technologies. In the final thesis, we focused on the fused deposition modelling. We were interested in how the degree of internal filling affects the mechanical properties of a PLA material. According to the standards for polymeric materials, we printed out the test pieces and then tested them on the devices for bending and impact testing. Impact toughness was calculated from the ratio of the impact part and the cross-sectional area of the specimen at the fracture site. In the bending test the force was measured and the bending tension was calculated. The findings were that PLA material is fragile. The mechanical properties increase as the occupancy rate increases. For less congested parts, therefore, minimum fill rates would be used, while for more congested areas the highest fill rate would be used.