Researchers at NASA’s Marshall Space Flight Centre, Huntsville, Alabama, USA, have developed what is claimed to be a novel method for interim, in-situ dimensional inspection of additively manufactured parts. The space agency’s new technology uses infrared (IR) and visual cameras to allow users to monitor the build in real-time and correct the process as needed, reducing the time and material wasted in parts that will not meet quality specifications.
NASA believes the technology has the potential to enable the implementation of a closed-loop feedback system, allowing systems for automatic real-time corrections. Different types of cameras are strategically placed around the part to monitor its properties during construction: the IR cameras collect accurate temperature data to validate thermal math models, while the visual cameras obtain highly detailed data at the exact location of the laser to build accurate, as-built geometric models.
The technology also uses a range of adopted techniques (e.g. single to grouped pixels comparison to avoid bad/biased pixels) to reduce false positive readings. This is said to be especially useful for the in-process inspection of a part’s internal features (e.g. fluid channels and passages), which cannot be easily inspected once the print is complete.
NASA has developed and tested prototypes in both laser-sintered plastic and metal processes. The technology detected errors due to stray powder sparking and material layer lifts, and demonstrated the potential to detect anomalies in the property profile caused by errors due to stress, power density issues, incomplete melting, voids, incomplete fill and layer lift-up.
Three-dimensional models of the printed parts were reconstructed using only the collected data, demonstrating the success and potential of the technology to provide a deeper understanding of laser-metal interactions. By monitoring the print, layer by layer, in real-time, users were able to pause the process and make corrections to the build as needed – reducing material, energy, and time wasted in nonconforming parts.
According to NASA, the new system offers the following benefits:
- Robustness – leveraging processing techniques to reduce false positive readings
- Flexibility – enabling it to be implemented in existing systems
- Economy – reducing the time, energy, and material wasted in nonconforming parts
- Accuracy – using both IR and visual cameras for thermal and spatial accuracy
NASA’s researchers expect the new technology, which is available on license, to be especially useful in Additive Manufacturing for the aerospace, automotive and medical industries.
Potential users can apply to license the technology via NASA’s Technology Transfer Program website.