In-process monitoring of the melt-pool motion during continuous-wave laser metal deposition

Abstract

Abstract In the field of additive manufacturing (AM), the implementation of real-time monitoring systems is essential to guarantee the quality and repeatability of the manufactured parts. Particularly in the laser metal deposition technique, the dynamics and stability of the molten pool, both geometrically and thermally, have an impact on the microstructural properties and the formation of defects. This article presents a novel technique to track the molten pool in real-time. A middle wavelength infrared (MWIR) camera is used, with a spectral range between 3 and 5 μm. The acquired frames are processed to reduce their dimension using a new strategy based on Superpixels. Traditional pixels are grouped into block-structures that are similar in temperature, optical flow, and spatial position. This guarantees a better adherence to the edges improving the segmentation task. Then, the optical flow of the molten pool is calculated. Throughout this tracking, geometric and thermal features are extracted. The proposed method was evaluated using qualitative and quantitative criteria. The performance of the proposal is compared against benchmark algorithms using standard metrics such as Sub-segmentation Error, Compactness, and Achievable Segmentation Accuracy obtaining better results. The proposal presented is robust to the number of superpixels generated as well as the size of the images. Which provides better performance for in situ monitoring tasks. Our proposal has significant industrial potential for monitoring additive manufacturing processes, as it requires minimal modifications to commercially available industrial machines.