Adaptive powder nozzle for additive manufacturing processes

• Applicants: Professor Dr.-Ing. Rodion Groll; Dr.-Ing. Thomas Seefeld, since 10/2021
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 424886092

An essential scope in the cost savings of additive manufacturing processes lies in the efficient and economical use of additive materials. Using the example of laser powder build-up welding, this corresponds to the precisely metered use of the powder to be used. In the framework of the project presented here, various concepts are investigated both experimentally and numerically in order to avoid uncontrolled diffusion of the introduced powder and to ensure effective use of this additive material. With the aim of predicting the underlying material efficiency and the quality of the weld, the welding process in different nozzle configurations including the thermal input of the laser beam is investigated both experimentally and numerically.For a higher powder efficiency an adaptive powder nozzle will be designed. This contributes a defined adaption of the powder-spot diameter to the diameter of the laser-spot. The adaptive powder nozzle consists of three single nozzles which are arranged coaxially to the laser beam. Their distance to the substrate surface and their working angle could adjusted variably. Besides the influence of the powder nozzle position on the size of the powder-spot diameter the position has also amongst others an impact on interaction period between the particles out of the powder stream and the laser beam. Both a very long and a very short interaction period can have a negative impact on process efficiency or welding bead quality. Aim of this project is to identify the relevant process parameters for the size of the powder-spot diameter as well as the interaction period to manufacture small or large single tracks. The gained process knowledge will be transferred for producing large multi-track structures with a high precision.Accompanying the experimental investigation, based on an Euler / Lagrange description, the motion of the powder particles as well as that of the surrounding air as a carrier phase are numerically modeled. The particle / wall interaction within the nozzle and large-scale turbulent structures in the wake of the nozzle exit have a significant influence on the powder diffusion and accordingly the material efficiency of the process to be described. The dynamics of the particle phase are correspondingly mapped by a particle-in-cell (PIC) method, which takes into account both the interaction with the carrier phase and the interaction of the polydispersed particle phase with respect to mutual particle collisions.With this improved concept, in combination with new simulation approaches to describe the phase transition of solid particles, diffusion processes in turbulent and polydisperse multiphase flows are to be predicted in order to enable a better focusing of the powder flow of build-up welding processes.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Frank Vollertsen, until 9/2021