The paper-forming sieve is the most important part of the paper production machine. Reliability of the machine as a whole depends on the sieve's quality. An analysis of the two constructions of the paper forming sieves, which were obtained by the plasma welding of the sieve's wires, is presented in this paper. The mechanical characteristics of the two sieves, made of wires of diameters 0.15 mm and 0.20 mm, were tested, namely the tensile strength and elongation. The tests have shown that the sieve made of the wire of the smaller diameter has the better mechanical properties. This sieve is also better from the aspect of the water removal in the press section of the paper machine.