The invention relates to a method for manufacturing a sandwich panel as a semi-finished product where at least one layer of a non-metallic material is positioned between at least two metallic layers. At least one of the metal layers is shaped into a three dimensional layer, and the metal layers are in direct mechanical contact to enable resistance weldability of the semi-finished product in order to connect the semi-finished product to a desired combination of solutions in a subsequent manufacturing process.

The seam welding apparatus includes a pair of rotating electrodes, an electrode supporting frame, a distance measuring means, and a controller. The electrode supporting frame supports the pair of rotating electrodes. The distance measuring means is provided on the electrode supporting frame and measures a distance to an edge of the steel plate. The controller controls the robot to adjust a running direction of the rotating electrodes so that a deviation comes into zero when a distance actually measured by the distance measuring means deviates from a predetermined distance. Thereby, it is accomplished that the seam welding apparatus is downsized as well as uninfluenced by the surface state and/or shape of workpiece (steel plate).

The invention relates to a method for manufacturing a sandwich panel as a semi-finished product where at least one layer of a non-metallic material is positioned between at least two metallic layers. At least one of the metal layers is shaped into a three dimensional layer, and the metal layers are in direct mechanical contact to enable resistance weldability of the semi-finished product in order to connect the semi-finished product to a desired combination of solutions in a subsequent manufacturing process.