Laser metal deposition (LMD) is a blown powder process used for the additive manufacturing of large as well as complex parts. The laser spot size is determined by the fiber optic cable and by the imaging ratio of the process optics. Spot sizes typically used for LMD can range between 200 µm up to several millimeters. Zoom optics are able to change the laser spot focus within seconds during the process. However industrial powder nozzles are still static in their powder spot size. Changing the powder spot size accordingly to the laser spot size could lead to a desirable union of time savings when printing large volumes while also generating fine near-net-shape features.
To overcome the current limitations in the LMD process, this work examines an adaptive powder nozzle system. In this discrete coaxial layout of three single powder nozzles the individual powder nozzles can be adjusted closer and further from the process to dilate or shrink the powder focus. Different diameters of powder channels are examined. The resulting powder propagation behavior is characterized for different settings of the single powder nozzles. Single tracks are welded with different nozzle settings for a fine and coarse powder spot, while accordingly changing the laser spot size with a zoom optic. The laser power is closed-loop controlled by a 2-color pyrometer to achieve comparative process temperatures. The single tracks are evaluated with regard to their geometry. High-Speed imaging gives supplementary information on the welt track generation.