Session: 02-02-02: Session #2: Measurement Science, Sensors, Non-destructive Evaluation (NDE) and Process Control for Advanced Manufacturing

Paper Number: 96980

96980 - Build Chamber and Start Plate Variability During Electron Beam Melting Machine Setup 

Electron beam melting (EBM) is an additive manufacturing process that utilizes a metallic powder as the feedstock material. This material is commonly fetched from powder hoppers and deposited over the build plate using a rake. During the setup of an Arcam A2X machine, the operator is first required to load the feedstock into the hoppers and set the “zero” position of the build or “start” plate. This is accomplished after the powder basin is filled with powder and the start plate is positioned on the powder bed. The height of the plate is then continuously adjusted until the rake “barely cleans” the entire start plate. As necessary, the operator is advised to knock on the plate corners to achieve a level position. This process establishes the build surface orientation (i.e., parallelism) relative to the sweep direction and angle of the rake. Positioning of the build plate relative to the rake is a manual process which relies on operator-experience and is hypothesized to have a detrimental impact on process repeatability by locally modifying the expected powder layer thickness. Furthermore, the potential effects on the as-built quality and performance of EBM manufactured components due to these relatively uncontrolled aspects of the process are unknown.

Therefore, this study presents a device used to measure the variability that exists within an Arcam A2X build basin and the start plate “zero” position. The device indexes with the profile surfaces of the rake using a simple, “123” indexing configuration. The device is equipped with a linear actuator and contact probe which senses contact using an Arduino microcontroller and the A2X thermocouple grounding wire. Location of the build basin and start plate are provided relative to a limit switch. The steps of the linear actuator are converted to a distance measurement which were checked by probing the bottom of a M3-0.5 socket head cap screw (SHCS) over the course of several turns. The results of a pilot study considering a single Arcam A2X and ten build plate setups are provided. Assuming a mean Ti-6Al-4V particle diameter of 50 μm and commensurate layer thickness, the data indicate that local thickness deviations greater than ten layers are achievable using the prescribed zeroing routine. These process details have important implications on beam penetration, the development of overall manufacturing process melt strategies, and final product quality. While not directly considered in this study, a discussion regarding powder pile size during fetching operations and how this may affect bed coverage will also be provided.

Presenting Author: Garrett Kelley University of Washington

Presenting Author Biography: Garrett Kelley is a PhD student at the University of Washington where his focus is in experimental and computational characterization of the electron beam melting process for Ti-6Al-4V. He has 11 years experience in the aerospace tooling industry, as a project manager, designer, and stress analyst. He is also a registered professional engineer in the state of Washington.

Authors:

Garrett Kelley University of Washington
Ramulu Mamidala University of Washington