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Real-Time Acoustic Emission Monitoring of Powder Mass Flow Rate for Direct Energy Deposition



Justin G. Whiting, Adam Springer, Federico Sciammarella


The material delivery rate in the direct energy deposition (DED) process must be monitored and controlled to ensure a reliable and repeatable additive manufacturing process. In the DED process, metal powder is delivered through a nozzle into a molten pool that rapidly solidifies, creating a solid part. The mass flow rate of these metallic particulates is critical to the consistency of single-track geometry and, in turn, the final part quality. The two-phase flow created by the metal particulates and the inert gas stream that conveys them through the nozzle for delivery into the molten pool, creates a situation in which conventional mass flow sensors cannot be used. To date there has been limited research conducted on monitoring the powder delivery system in the DED process, and the narrow breadth of work published has focused on the use of optical based photodiodes that must have a line of sight to the flow. Furthermore, these systems can be expensive and often require the flow path to be altered to provide appropriate viewing. In this paper the use of acoustic emission (AE) sensing as an alternate method of monitoring the flow in the DED process is proposed. Acoustic pressure waves are produced when the particulates strike either one another or the internal walls of the delivery lines. This pressure is transduced by a piezo-electric element into electro-motive force. With minimal calibration, this signal has been found to closely correlate to the actual mass flow rate. This article describes the fabricated mass flow monitoring system, documents various conditions in which the actual flow rate deviates from its set value, and details situations that showcase the system's utility. While AE mass flow monitoring is not free of concerns, its features make it an attractive measurement technique in the DED process.
Additive Manufacturing


Acoustic Emission, Direct Energy Deposition, Powder Flow Rate, Quantitative Nondestructive Evaluation


Whiting, J. , Springer, A. and Sciammarella, F. (2018), Real-Time Acoustic Emission Monitoring of Powder Mass Flow Rate for Direct Energy Deposition, Additive Manufacturing, [online], (Accessed April 24, 2024)
Created August 18, 2018, Updated November 10, 2018