Method for scanning the surface of metal workpieces

A method for scanning a surface of a metallic workpiece, the method comprising the steps of:

• during a scanning process, moving a welding torch with a consumable welding wire over the surface of the metallic workpiece, and moving the consumable welding wire towards the surface of the metallic workpiece at specified points in time at a forward speed, until a contact of the consumable welding wire with the metallic workpiece is detected by a welding current source, and subsequently moving the consumable welding wire away from the metallic workpiece again at a backward speed,
• carrying out a slag-removal process to remove slag at an end of the consumable welding wire before the scanning process,
• at a start of the slag-removal process, lowering a welding current to a minimum, and cyclically moving the consumable welding wire with a rapid recurrent forward/backward movement over a specified path length in direction of the metallic workpiece, and by a smaller distance away from the metallic workpiece again, so that a conveyance of the consumable welding wire to the metallic workpiece prevails, and upon a detection of no short circuit between the consumable welding wire and the metallic workpiece, repeating the slag-removal process, and upon a detection of several short circuits between the consumable welding wire and the metallic workpiece one after another, ending the slag-removal process, and
• starting the slag-removal process when a wire feed speed sinks below a specified threshold value when moving the consumable welding wire at a specified wire feed speed in the direction of the metallic workpiece before the scanning process.