Joining a workpiece in a concealed joining seam

A method for joining concealed workpiece parts by an energy beam, comprising:

• a) positioning at least one lower workpiece part and at least one upper workpiece part relative to each other;
• b) when the at least one lower workpiece and the at least on upper workpiece are positioned, the at least one upper workpiece part contacts the at least one lower workpiece part along a joining contour of the at least one lower workpiece part and conceals the joining contour, the target profile of which is known to a controller in relation to a co-ordinate system;
• c) directing the energy beam onto an upper side of the at least one upper workpiece part, which faces away from the at least one lower workpiece part, and is moved along the joining contour by the controller;
• d) producing an exploratory seam using the energy beam on the upper side of the at least one upper work piece part, for detecting the joining contour;
• e) detecting a boundary by a detector at which a surface area of the at least one upper work piece part, which does not have any contact with the at least one lower work piece part, borders a surface area of the at least one upper work piece part which does have contact with the joining contour;
• f) registering a position of the boundary by the controller and comparing it with a target position of the boundary which is stored in the controller;
• g) correcting a movement of the energy beam along the joining contour if the position of the boundary deviates;
• and
• h) joining the at least one upper workpiece part to the at least one lower workpiece part along the joining contour or along the corrected joining contour with the energy beam by adhesive bond after detection thereof.