Utilizing Sound for Detecting Defects in Metal 3D Printing


Scientists at the École Polytechnique Fédérale de Lausanne (EPFL) are presently studying defects noticed in metal 3D printing, especially during a laser process. The objective is to devise a method based on analyzing the sounds emitted by a 3D printer, in order to predict any possibilities of errors during printing, thereby improving the outcomes. The team has recorded and studied the sounds produced in both, a flawless printing process and a process containing faults. By collaborating with the Paul Scherrer Institute (PSI) and the Swiss Federal Laboratories for Materials Science and Technology (Empa), EPFL inserted a microphone in the printing chamber to perceive variations in the acoustic signal when the state of the metal powder changed.

Although the perception of printing mistakes is not newly recognized, many projects have recently been designed to assure reliable and repeatable results. These projects are habitually based on algorithms that can infer from known scenarios, but they are often flawed and require broad testing. EPFL scientists are planning towards overcoming this limitation by implementing a sound-based technique.

In the process of laser powder bed fusion, a slim layer of metal powder is heated to shape the desired object, one layer at a time. As the material goes through various stages – solid, liquid, and gaseous – forming a molten bath, the procedure may falter due to variables such as the angle of the laser or specific geometric attributes of the powder or the part. These situations, termed “inter-regime instabilities”, can sometimes initiate shifts between two different melting methods, known as “conduction” and “keyhole” regimes.

The teams use X-ray images to measure this melt pool (in width and depth) and have developed a method that enables them to see the changes in the metal when it is liquid. Thanks to a microphone installed in the printing chamber, they are then able to record the sounds produced during transitions between regimes and spot any shifts. If they exist, a defect has been detected. Lead researcher Milad Hamidi Nasab adds, “The synergy of synchrotron X-ray imaging with acoustic recording provides real-time insight into the LPBF process, facilitating the detection of defects that could jeopardize product integrity.”

The researchers are only at the beginning of their experiments, and are confident about the future of this solution. However, what is certain, is that it should make it possible to design parts with greater reliability and repeatability, a key point for many manufacturers today. You can find the official press release HERE.

Original source


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