Laser powder bed fusion (LPBF) has the ability to produce three-dimensional lightweight metal parts with complex shapes. Extensive investigations have been conducted to tackle build accuracy problems caused by shape complexity. For metal parts with stringent requirements, surface roughness, laser beam positioning error, and part location effects can all affect the shape accuracy of LPBF built products. This study develops a data-driven predictive approach as a promising solution for geometric accuracy improvement in LPBF processes. To address the shape complexity issue, a prescriptive modeling approach is adopted to minimize geometrical deviations of built products through compensating computer aided design models, as opposed to changing process parameters. It allows us to predict and control a wide range of shapes starting from a limited set of measurements on basic benchmark geometries. An error decomposition and compensation scheme is developed to decouple the influence from different error components and to reduce the shape deviations caused by part geometrical deviation, laser beam positioning error, and other location effects simultaneously via an integrated modeling and compensation framework. Experimentation and data collection are conducted to investigate error sources and to validate the developed modeling and accuracy control methods.
The demand of measuring the internal topography of holes with submillimeter diameter and high aspect ratio is increasing. However, moving a coordinate measuring machine (CMM) probe tip into a submillimeter hole manually is extremely difficult because the diameters of the probe tip and the hole are extremely small to be seen clearly with human eyes. An automatic measuring method and system is presented in this study to simplify the operation and improve the measuring efficiency. A micro CMM system was built. Two cameras were used to image the probe tip and the holes to be measured. The obtained images were magnified, and the edges of the probe tip and the holes were extracted. The image coordinates of the center points of the probe tip and the hole were obtained. The center coordinate values of the probe tip and the hole in the world coordinate system were achieved using the principle of binocular stereo vision. The probe tip was moved into the holes by the differences in the obtained coordinate values. Experiments were conducted. The effectiveness of the proposed method and system was verified by moving the probe tip into a hole with 1 mm diameter. This method can be used to assist in the measurement of deep submillimeter holes, especially in nonbatch measurement situations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.