If you're 3D-printing metal parts for use in aircraft or other critical systems, then those parts had better not be defective. A new system allows such items to be checked for structural flaws, quicker and cheaper than ever before.
Typically, 3D-printed metal alloy objects are made up of a lattice of microscopic crystals – it's similar to the woodgrain of wooden items.
In order to assess the strength and toughness of such printed alloys, scientists use scanning electron microscopes to ascertain the size, shape and alignment of the crystals. Not only does doing so take a long time, but the microscopes themselves can cost anywhere from US$50,000 to over a million dollars.
Led by Asst. Prof. Matteo Seita, researchers at Singapore's Nanyang Technological University set out to develop a less expensive, less labor-intensive alternative. The system they created incorporates an optical camera, a flashlight-like light source, and a notebook computer running machine-learning-based software – the setup's total cost is about US$18,400.
Users start by chemically etching the surface of the printed item, in order to reveal the alloy's microstructure. This means that one item out of a larger production run would have to be sacrificed for inspection. Next, the camera is used to take multiple photos of the object, while the light is moved to illuminate it from different directions.
The software subsequently determines the shape, size and orientation of the micro-crystals, by analyzing the manner in which they scatter the reflected light in the different photographs. That information can in turn be utilized to determine the object's strength and toughness. From start to finish, the inspection process takes only about 15 minutes.
"Using our inexpensive and fast-imaging method, we can easily tell good 3D-printed metal parts from the faulty ones," said Seita.
A paper on the research was recently published in the journal npj Computational Materials.
Source: Nanyang Technological University
