Stereo camera based in-situ monitoring of L-PBF process stability by spatter detection

The stability and reproducibility of the melting process is a decisive factor for the quality of the printing process and the final part. Stereo-vision in-situ monitoring based on two high-speed cameras in combination with fringe projection is used to investigate the three-dimensional layer topography, process spatter and residue of the melting process of laser powder bed fusion (L-PBF) process. The stereo camera system provides intensity data and a depth map of the working plane. The depth map has a lateral resolution of 40 µm and a depth variance 𝜎² of 3.76 µm. The stability of the printing process can be estimated by monitoring the development of spatter and residue. Both are undesired by-products of the L-PBF process, which can indicate the present melting conditions. By optimizing the process conditions and reducing the scrap rate of printed parts, manufacturing costs can be reduced. This paper proposes a method to localize and quantify spatter emitted during the melting process, by combining the obtained depth data and the raw intensity data. The proposed method is evaluated in the course of an empirical investigation, which consists of three experiments. Within the experiments, unsuitable process conditions are caused intentionally by process parameter variation. In a real-life situation, these impairing process parameters could have been caused by defective machine components or miscalibration, and would possibly remain undetected without the technical ability to reliably monitor process stability. By measuring concentration, size and shape of the emitted spatter, the change in process parameters could be quantified and detected successfully by the proposed method. Especially overheating of material due to high local energy input and the dependency on the size of exposed area could have been identified reliably.

DDC Class

600: Technik

620: Ingenieurwissenschaften

Options

Stereo camera based in-situ monitoring of L-PBF process stability by spatter detection