2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Process Development: Powder Bed Fusion III
Program Organizers: Joseph Beaman, University of Texas at Austin
Tuesday 1:30 PM
August 13, 2024
Room: 415 AB
Location: Hilton Austin
Session Chair: Joy Gockel, Colorado School of Mines
1:30 PM
Non-Invasive Measurement of SS304L Powder Bed Density via Flash Thermography: Shu Wang1; Nathan Crane1; 1Brigham Young University
In binder jetting (BJ) and powder bed fusion (PBF) processes, precise control and monitoring of powder bed density are critical for ensuring the quality and mechanical properties of the final printed parts. Traditional methods for measuring powder bed density typically require large samples and disrupt the powder layer, disrupting the building process. Flash Thermography (FT) offers significant advantages in the real-time monitoring of powder bed density without disturbing the bed. We developed and refined methodologies that enable accurate calculation of the relative density of SS304L powder resting on a metal substrate. This provides sufficient property contrast to extract powder bed density with one to two flashes. The powder bed density measurements have errors of about 5% and a coefficient of variation around 6%. This study highlights the potential of FT as a transformative tool for in-situ monitoring in PBF, paving the way for more consistent and reliable fabrication outcomes.
1:50 PM
Exploring Effects of Part Geometry for PBF-LB Bismuth Telluride Parts with In-situ Process Monitoring: Clayton Perbix1; Saniya LeBlanc2; Joe Walker3; Joy Gockel1; 1Colorado School Of Mines; 2George Washington University; 3Open Additive
Bismuth Telluride (Bi2Te3) is an important material used in thermoelectric applications. However, the effect on microstructure and ultimately thermoelectric performance when it is additively manufactured using laser powder bed fusion (PBF-LB) is not fully understood. This study investigates the effect of various processing parameters and part geometries on the quality and microstructure of PBF-LB Bi2Te3. In-situ process monitoring was performed using thermal tomography to provide per-layer information about sample thermal behavior. Results showed that increasing part size led to undesirable printing defects, and individual parts also exhibited a large range of microstructural features. Thermal tomography data showed that larger layer cross-sections retained more heat during processing, a result contradictory to what has been shown in structural metals processing. Understanding the effects of part geometry on thermoelectric materials such as Bi2Te3 will provide the ability to create more complex geometries and enable higher performance thermoelectric devices.
2:10 PM
Design of a Heated Build Plate for Printing Refractory Alloys Using Powder Bed Fusion: Jacques Wang1; Carolyn Seepersad1; 1Georgia Institute of Technology
The powder bed fusion process enables the development of complex shapes, such as lattice structures, that can provide desirable mechanical properties at a fraction of the weight when compared to bulk material. Ongoing work focuses on applying this manufacturing process to refractory metals, such as molybdenum alloys, because of their suitability for extreme environmental conditions including high temperature and radioactivity. An ongoing concern when printing these metals is that their high processing temperature results in warping and cracking when fabricated with standard, low temperature build plates and powder beds, and an actively heated build plate can alleviate these challenges. The objective of this work is to develop a safe and reliable design for a heated build plate and develop sample parts to explore proper process parameters for printing these materials.
2:30 PM
Laser Induced Breakdown Spectroscopy for Chemistry and Composition Monitoring of Laser Powder Bed Fusion Processing: Edward Kinzel1; Justin Krantz1; Gonzalo Reyes-Donoso1; Robert Landers1; Ben Brown2; Cody Lough2; 1University of Notre Dame; 2Kansas City National Security Campus
A major challenge in Laser Powder Bed Fusion (LPBF) process development is the ability to perform analysis in-process. In-situ monitoring provides the opportunity to identify flaws and address them during the build process. One process of particular interest is Laser Induced Breakdown Spectroscopy (LIBS). This process can provide the potential to collect data about material composition with the potential to react to this information. A femtosecond laser is coaligned with a CW process laser for simultaneous use during the LPBF process. The ultrafast laser is used to probe the melt pool of in-process LPBF builds, creating plasma from which signals are collected with minimal impact on the melt pool. This process allows for superior emission collection capabilities compared to techniques such as optical emission spectroscopy. The Department of Energy’s Kansas City National Security Campus (operated and managed by Honeywell Federal Manufacturing Technologies, LLC under contract number DE-NA0002839) funded this work.
2:50 PM
Detecting Residual Powder in Additively Manufactured Parts via Impedance Measurements: Nathan Raeker-Jordan1; Sourabh Sangle2; Pablo Tarazga2; Mohammad Albakri2; Christopher Williams1; 1Virginia Tech; 2Texas A&M
Powder bed fusion (PBF) additive manufacturing (AM) processes allow for the creation of complex, end-use parts from high-performance polymers and metals. However, complex geometries can have internal features that are challenging to depowder, resulting in residual powder trapped within the completed part. While there are various methods of powder removal or depowdering (e.g., mechanical manipulation, vibration/ultrasonic excitation, or washing), there are no formal processes for verifying depowdering completeness in the literature. In this work, a novel means of detecting the presence of residual powder in metal and polymer PBF AM parts is presented. This method leverages electromechanical impedance (EMI) -based measurement techniques, whereby loose powder within or on the surface or a part changes its resonant behavior and the resulting characteristic EMI response. The precision of this method is evaluated on geometries fabricated by both polymer and metal PBF, allowing for detection of as little as 0.8% powder by mass.
3:10 PM
Laser Beam Sources and their Influence on Tailored Microstructure, Mechanical Properties, and Increased Productivity in Laser Powder Bed Fusion Additive Manufacturing: Cesar Terrazas1; 1AconityUS, Inc.
Recent advances in laser powder bed fusion (L-PBF) additive manufacturing of metals involve the use of lasers with tuneable intensity profiles enabling the control of the energy distribution and hence of the thermal gradients and the solidification pathway during the material deposition process. In this work, we present current developments involving the use of various laser sources applied in a L-PBF platform from Aconity3D GmbH. Several case studies will be presented to showcase tailoring microstructural features and mechanical performances of components built using both traditional laser sources with a Gaussian intensity distribution and those in which the emission profile is controlled (i.e. ring beam or top hat) at discretion while shifting the productivity to the next level. Results are presented for several materials of interest in the fields of aerospace, automotive and medical, and to the larger additive manufacturing community.