Method for producing welded helical-seam tubes having optimized tube geometry

The invention relates to a method for producing welded helical-seam tubes (10) having optimized tube geometry. A metal strip (1) is helically shaped into an open seam tube by means of a forming unit (11) and the converging strip edges are welded together, wherein an actual diameter determined on the welded tube is compared with a specified target diameter and any deviation lying outside a tolerance threshold is used to correct the actual tube diameter, wherein the strip edges are completely welded in a two-stage step, comprising tack welding as a first step immediately after the shaping to form an open seam tube and thereafter final welding as a second step. According to the invention, the tube diameter is measured after the complete shaping to form an open seam tube and before the final welding. For this purpose, the diameter measuring device (8) is arranged in such a way that either the completely shaped open seam tube or the only tack-welded tube is measured.