COAXwire: Processing optic for laser wire cladding

Laser wire cladding is a well-proven technology which came up with the first powerful laser sources already in 1974 in the United States [1]. The single-step metal deposition principle is commonly based on a lateral supply of the wire feedstock material. Important advantages are the complete material utilization, the clean and stable process, and the increased productivity in case of hot wire cladding. While the traditional technology is based on a single laser beam with the lateral and, thus, direction-dependent wire supply, special two-beam optics with centric wire supply have been developed. These optics enable an advantageous omni-directional welding operation in all technical welding positions [2]. Further developments at Fraunhofer IWS concern several designs of multi beam optics with centric wire supply to increase direction-independence and process stability [3]. The latest result with respect to industrial performance is a completely new generation of a beam splitting optic called IWS COAXwire. Special features of that new head are the low weight, compact design, easy handling as well as flexible interfaces to the operating system, laser source and wire feeder drive. For long-time stability, a cooling circuit for the optic elements and the wire supply, cross jets for deflection of splatters and down jets for dust protection have been integrated. Based on the reflective beam splitting concept, COAXwire aligns three single beams at 120 degrees to one and another around the optic's center axis to a combined triple focus. With a fixed working distance, the focus diameter can be set by the choice of the fiber diameter and the collimation type. All common laser sources could be coupled via LLK-D, LLK-B or QBH connectors. As a very special feature, an integrated emergency-stop module protects the optic in the case of collision or process irregularities. COAXwire enables to use nearly all commercially available solid as well as cored wires, in fine or standard dimensions as filler material. Potential and current applications are wear protection of parts like hydraulic cylinders or forming dies with Fe-, Co- or Ni- base alloys, rapid design changes using similar materials as well as repair or generation of 3D-parts with Ti- and Ni- aerospace alloys. The deposition rates at 4 kW laser power lie in the range of 100 to 250 cm³/h, depending on the material and the part's geometry. Current developments aim at further improvement of the operating properties and conditions like process monitoring, closed shielding gas chamber to process oxygen affine materials, and also feeding drives for very fine wire diameters. Finally, the realization of advanced omni-directional cladding and buildup strategies on robot machines lies in the focus of process development.