Real-time acoustic emission monitoring of powder mass flow rate for directed energy deposition

Abstract

In order to ensure a reliable and repeatable additive manufacturing process, the material delivery rate in the directed energy deposition (DED) process requires in situ monitoring and control. This paper demonstrates acoustic emission (AE) sensing as a method of monitoring the flow of powder feedstock in a powder fed DED process. With minimal calibration, this signal closely correlates 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 highlight the system’s utility. While AE mass flow monitoring is not free of concerns, its features make it an attractive measurement technique in the powder-fed DED process. The work presented here highlights the results obtained and illustrates that accurate monitoring of powder flow in real-time regardless of environmental conditions within the build chamber is possible.

Processing Parameter DOE for 316L Using Directed Energy Deposition

“…These devices were part of a larger study taking place at NIU's Advanced Research of Materials and Manufacturing (ARMM) Lab on process monitoring and property control for MAM [19], which was sponsored by NIST MSAM. An in-situ acoustic emission sensor in the LENS monitored the powder flow as a function of time (Figure 2), and in this way, the mass flow rate could be independently tracked during the build [17]. The presence of the sensor is critical to determining the appropriate powder flow since the powder flow has a strong influence on the balance of the available energy.…”

“…An in-situ acoustic emission sensor in the LENS monitored the powder flow as a All the builds were performed on a LENS 850 M system in which the deposition head moves in x and y directions and the build plate moves in the z direction (see Figure 2). Two custom built, in-situ process monitoring devices were utilized for this work: one has the capability to measure powder flow in real time [17], and the other can monitor the energy density during builds [18]. These devices were part of a larger study taking place at NIU's Advanced Research of Materials and Manufacturing (ARMM) Lab on process monitoring and property control for MAM [19], which was sponsored by NIST MSAM.…”

Predicting the Strength of EBAM 3D Printed Ti-6Al-4V from Processing Conditions

“…Similarly, by working to incorporate other in situ process monitors, such as novel acoustic sensing, it is anticipated that this model could be significantly improved. The acoustic signatures during print may hold the key to identifying potential material failure points within prints in real-time [32][33][34][35]. The linear regression model will also be applied to smaller-scale geometries and single wall prints in a different material than the Ti-6Al-4V discussed.…”

A monitoring framework based on exergetic analysis for sustainability assessment of direct laser metal deposition process

“…This parameter is fundamental for the quality and the sustainability assessment of the laser deposition process because it strongly impacts on the deposited track. In the literature, the real-time measurement of this parameter remains an open challenge [66] also because there are few commercial devices capable of measuring it. As no suitable sensor was available, the powder flow assessment was carried out by means of a preliminary series of flow tests.…”