Additive manufacturing, or 3D printing, is revolutionizing manufacturing processes. But to develop viable products for particular applications, researchers must find and eliminate flaws. A technique being refined at ORNL uses various imaging techniques to cost-effectively evaluate the quality of components in situ, or as they are being printed.
“Traditionally when you print an object, you create the specs, give them to the printer, and you get the product back,” said Vincent Paquit, a researcher in the Imaging, Signals, and Machine Learning Group of the Electrical and Electronics Systems Research Division. “You don’t know if this product is good or not for its final use.”
If the object is being used in a simple application, minor flaws may not matter. But what if the object is intended for use in a car, where the engine gets quite hot? A weak area might not be able to hold up to high heat, and the part might then fail. That’s why it is important to certify the results of the 3D printing process.
Using Images and Sensors
One effective approach is to x-ray the object after it is printed. X-ray imaging provides clear results but is prohibitively expensive and, as a result, limits the commercial implementation of additive manufacturing to unique applications.
Paquit and his colleagues are instead using various forms of imaging and sensors to look at every single layer during the printing process. The resulting data pinpoint problems or weaknesses.
“We can monitor on the fly what’s going on in the object as we’re printing,” he said. “You know every single time what the process parameters are in the printer when you are printing one dot in space, so if you can extract information on the fly and correlate it to the data collected from sensors, you can find the link between the two data sets.”
Paquit and his group are using a variety of 3D printers. Most of the work has been focused on Arcam, a company with strong collaborative ties to the lab under a Cooperative Research and Development Agreement; DOE’s Manufacturing Demonstration Facility at ORNL currently has three Arcam printers and will add another soon. However, these techniques can be applied to nearly any 3D printing process.
The Arcam printers each include a near-infrared and/or thermal camera at the top of the chamber directed downward through a window to capture images of the power bed layer being printed. Although this imaging approach is less accurate, with lower-resolution images, the results are collected in real time and are close enough to x-ray studies to be extremely valuable.
Key Advantages
The key advantage of in situ imaging that makes it more cost effective is that it can eliminate waste associated with the x-ray process. Each layer of printing is scanned, so flaws are found early. If scanning reveals that an object is not going to work for its planned application, the researcher just stops printing it, with no additional waste of the printing medium. The researcher can make adjustments to fix the issue and then start printing again.
