Method for scanning the surface of metal workpieces and method for carrying out a welding process

Method for scanning the surface (O) of metallic workpieces (W), wherein, during a scanning process before a welding process is carried out, a welding torch (1) with a meltable welding wire (2) is moved over the surface (O) of the workpieces (W), and at predefined times (ti) the welding wire (2) is moved towards the surface (O) of the workpieces (W) until a contact of the welding wire (2) with one of the workpieces (W) is detected, and the position (Pi) of the surface (O) of the workpieces (W) at each time (ti) is determined and stored in the welding power source (4), wherein an edge (K) is determined if the current position (Pi) of the surface (O) of the workpieces (W) exceeds at least one of the stored previous positions (Pi-n) of the surface (O) of the workpieces (W) by a predefined threshold value (S). To reduce the computing effort and to increase processing speed, the end of the edge (K) is determined if the current position (Pi) of the surface (O) of the workpieces (W) remains the same with respect to at least one of the stored previous positions (Pi-n), and if an edge (K) is determined, an edge detection parameter (KP) is set and output together with the current position value (Pi) and transferred to the manipulator (3).