Annular laser beam head for 3D printing of metal materials

The opto-mechanical head producing an annular laser beam enables an axial supply of a metal substance in the form of powder and wire and variation of the intensity distribution of the laser beam on the surface of the workpiece.

Authors: Edvard Govekar, Alexander Kuznetsov, Andrej Jeromen, Matjaž Kotar

In addition to selective laser melting, laser direct deposition (LDD) of metallic materials is one of the more promising processes for 3D printing of metal materials. Within the research of the group of the Laboratory of Synergetic at the Faculty of Mechanical Engineering of the University of Ljubljana (Edvard Govekar, Alexander Kuznetsov, Andrej Jeromen, Matjaž Kotar), an optomechanical head was developed for the application of a metallic substance, which by forming an annular laser beam, enables an axial supply of a metallic material in the form of powder or wire (Fig. 1a) and variation of the laser beam intensity distribution on the surface of the workpiece (Fig. 1c). The developed system achieves symmetry of the LDD process, which in addition to insensitivity to the direction of material deposition also ensures a higher stability of the process. This was confirmed in the framework of research into the process of laser generation and deposition of metal drops, which is an inherently unstable process [1, 2].

This achievement was the basis for further years of research and development of the system and process for LDD of metallic powder and wire by means of an annular laser beam in cooperation with the Japanese company DMG MORI. On the basis of research results, two patents were submitted and a prototype head for LDD (Fig. 1b) was developed, which with minimal adjustments allows LDD of powder or wire. In the case of metal wire LDD, the head enables precise adjustment of the proportion of energy input into the wire and into the base material, thereby additional controlling of the process stability [3, 4]. In the case of LDD of powder, a very high powder catchment efficiency (>80%) is achieved, and in addition to the standard process parameters the process stability and the properties of the deposited layer can be influenced by the distribution of the laser beam intensity (Fig. 1c).

References: Govekar E., Jeromen A., Kuznetsov A., Levy G. N., Fujishima M. Study of an annular laser beam based axially-fed powder cladding process, CIRP Annals, 1 (2018), 241-244.

Govekar E., Jeromen A., Kuznetsov A., Kotar, M., Kondo M. Annular laser beam based direct metal deposition. Procedia CIRP, 74 (2018), 222-227. 

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a) Annular laser beam with an axially delivered substance, b) Prototype system, c) Examples of generated intensity distributions (PI) and cross sections of deposits 

Image source: LASIN, Faculty of Mechanical Engineering, University of Ljubljana