Method and apparatus for applying an active joining force during laser welding of overlapping workpieces

A method, comprising:

• arranging a first workpiece in an at least partially overlapping relationship with a second workpiece to form a workpiece assembly to be joined together;
• applying a joining force at a welding location using a pressing device of a laser welding apparatus, the pressing device including an arm member having a pressing pad with an opening defined therethrough, the arm member being shaped such that the opening in the pressing pad is arranged at a known fixed distance from a laser optic unit of the laser welding apparatus to provide an optical path between the laser optic unit and the workpiece assembly, the pressing pad being fabricated from a wear-resistant material and having a pressing surface on a workpiece-facing side thereof for applying the joining force to the workpiece assembly at the welding location during the laser welding, at least a portion of the pressing surface being defined by a polished workpiece-facing surface of the wear-resistant material, and the pressing surface being contained in a single plane and extending around the opening with at least one discontinuity in said pressing surface;
• during application of the joining force, irradiating the welding location by directing a beam of laser light from the laser optic unit toward the welding location via the opening in the pressing pad;
• and
• moving the pressing pad relative to the workpiece assembly along a welding direction, with a sliding-contact movement between the pressing surface and a contact surface of the workpiece assembly, while simultaneously applying the joining force and irradiating, so as to form a connection between the first workpiece and the second workpiece along the welding direction,
• further comprising controlling the relative movement between the pressing pad and the workpiece assembly such that the at least one discontinuity is arranged along a trailing edge of the pressing pad relative to the welding direction such that the at least one discontinuity provides clearance for a weld bead that is created on the workpiece assembly during the laser welding.

A pressing device for a laser welding apparatus, comprising:

• an arm member having a mounting end and an opposite pressing end, the pressing end defining a pressing pad having an opening extending therethrough for allowing a beam of laser light to impinge upon a workpiece assembly that is being pressed by the pressing device, the mounting end having a mounting structure for detachably securing the pressing device to the laser welding apparatus, the arm member being shaped to position the opening in the pressing pad at a known fixed distance from a laser optic unit of the laser welding apparatus, and the pressing pad having a pressing surface on a workpiece-facing side thereof for applying a joining force to the workpiece assembly at a welding location during the laser welding;
• wherein at least one of a size, a shape and a smoothness of the pressing surface is configured to support a sliding-contact movement of the pressing surface along a surface of the workpiece assembly during application of the pressing force,
• wherein the arm member is fabricated from a wear-resistant material, and wherein at least a portion of the pressing surface is defined by a polished workpiece-facing surface of the wear-resistant material of the arm member, and
• wherein the pressing surface is contained in a single plane and extends around the opening with at least one discontinuity in said pressing surface, the at least one discontinuity, during laser welding, being arranged along a trailing edge of the pressing pad relative to a welding direction.