Additive Manufacturing: Equipment, Instrumentation and Measurement: Session III
Program Organizers: Ulf Ackelid, Freemelt AB; Ola Harrysson, North Carolina State University

Tuesday 2:00 PM
November 3, 2020
Room: Virtual Meeting Room 5
Location: MS&T Virtual

Session Chair: Ola Harrysson, North Carolina State University


2:00 PM  Invited
Real Time Monitoring of Electron Emissions during Electron Beam Powder Bed Fusion and Process Control for Arbitrary Geometries and Toolpaths: Tim Horn1; Chris Rock1; 1North Carolina State University
    Real-time monitoring of electron emissions during electron beam powder bed fusion provides a wealth of in-process data across multiple length scales. We present a methodology for collecting both real time beam positional data and electron emissions as a function of time for arbitrary component geometries and complex tool-paths. We demonstrate visualization spatio-temporal process data and mathematical correlation to known defects observed in the electron signal. Ultimately, we eliminate the need for computationally expensive electron images in favor of structurally terse time-domain data leading to a plausible, practical and economically viable approach to real-time defect control in the AM of metal alloys. The value proposition of this approach hinges upon both the interpretation of the massive quantity of data generated per component, as well as the ability to correlate anomalous features smaller than the beam to incipient defect formation and preventative control actions in real-time.

2:40 PM  
A New Preheating Method for Electron Beam Powder Bed Fusion, Opening a Wider Range of Processable Feedstocks: Ulf Ackelid1; Martin Wildheim1; Philip Nilsson1; Ulric Ljungblad1; 1Freemelt AB
     The evolution of Electron Beam Powder Bed Fusion started in the 1990’s. It was discovered early that an e-beam directed towards a powder bed is prone to scatter powder particles into a powder cloud. This phenomenon is known as “smoke” and if it happens, it usually disrupts the build process. Preheating of each powder layer with a fast-scanning e-beam was later developed to prevent smoke. The preheating semi-sinters the powder and increases its electrical conductivity prior to melting. This laid the basis of the commercial E-PBF process successfully used for titanium alloys today. However, e-beam preheating is not a universal cure. Anyone who has experimented with new powders in E-PBF knows the effort of finding smoke-safe preheating parameters. This paper introduces a new preheating method using infrared radiation. The method gives 100% smoke suppression and opens a wider range of powder compositions and morphologies for E-PBF.

3:00 PM  
Analysis of In-Situ, 3D Surround Digital Image Correlation with Mapped Thermography in Directed Energy Deposition: James Haley1; Samuel Leach1; Brian Jordan1; Ryan Dehoff1; Vincent Paquit1; 1Oak Ridge National Laboratory
    In Directed Energy Deposition (DED) AM, inherent residual stress and distortion are introduced by a complex and time-variable thermal field, which poses a serious barrier to widespread adoption of the process. Using an array of low cost visible and infrared cameras, we show that these distortions and temperature variations can be measured in-situ with full surround 3D using Digital Image Correlation (DIC), for any printed geometry. Such measurements provide rapid feedback for process optimization, as it allows direct measurement and estimation of a number of different key process variables. Capabilities and limitations of the system are discussed, and compare results to simulation and ex-situ measurements for sample geometries.

3:20 PM  
Benefits of In-situ Monitoring in Metal Additive Manufacturing: Kevin Luo1; 1FormAlloy
    Metal Additive Manufacturing processes such as Directed Energy Deposition (DED) can produce complex geometries with incredible benefits for applications, but there are challenges between concept design and producing a part. In order to create quality, repeatable parts, in-process monitoring can be utilized to both collect data and control the build process. The data collected can help determine the point of failure initiation, and with implemented control in place, self-correction is possible during the build process. With Directed Energy Deposition, various monitoring and control modes are available to reduce parameter development times, improve build quality, and limit operator input during a build. Among these control modes are melt pool size and temperature, powder flow, laser power, and geometric monitoring and control. These control modes not only significantly reduce the process parameter development cycle, but also result in a higher quality build to include density and material properties.