2024 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2024): Process Development: Powder Bed Fusion I
Program Organizers: Joseph Beaman, University of Texas at Austin
Monday 1:30 PM
August 12, 2024
Room: 415 AB
Location: Hilton Austin
Session Chair: Ben Fotovvati, Seurat Technologies
1:30 PM
On the Effectiveness of PBF-LB Particle Dampers with Thin and Flat Cavities Considering Industrial Process Variances: Julius Westbeld1; 1University of the Bundeswehr Munich
Powder Bed Fusion (PBF) enables the production of integrally-designed, stiff and lightweight structures, which are prone to vibration due to their low structural damping capabilities. Several studies have demonstrated the effectiveness of particle damping in such components or specific specimens to counteract this disadvantage by leaving unfused powder inside of the components during manufacturing. However, there is a lack of large-scale studies evaluating the reproducibility of these particle dampers, particularly in relation to expectable variances in industrial additive manufacturing (AM) processes. This presentation demonstrates how the damping of specimens with thin and flat cavities varies depending on adjustable parameters in the design and build job preparation, as well as the expected scatter of the damping properties independent of these parameters. In particular, different states of powder sintering in the cavities depending on the machine-powder combination exemplifies the sensitivity of the damping effectiveness of these additively manufactured particle dampers.
1:50 PM
High-Speed Imaging Investigation and Process Mapping of the Plume Behavior in Laser Powder Bed Fusion: Alexander Myers1; Christian Gobert1; Jack Beuth1; Jonathan Malen1; 1Carnegie Mellon University
The laser's small spot size and high power in laser powder bed fusion (LPBF) lead to peak melt pool temperatures above the boiling point of common alloys, resulting in the formation of a metal vapor plume. In this work, overhead high-speed imaging experiments were conducted with varying processing conditions and materials to understand the effect of each on the plume's size and trajectory. A U-Net convolutional neural network (CNN) was trained to segment the plume from experimental images. The overhead images were then used to process map the plume across process parameters such as scanning velocity, power, and shielding gas flow. This experimental study increases our understanding of the plume's behavior at the melt-pool scale in LPBF and can be used to inform parameter selection for minimal laser-plume interaction, validate multi-physics models of the plume, and provide optimum parameters for avoiding plume interference in melt-pool imaging.
2:10 PM
Model-Based Production Operational Control for Metal Additive Manufacturing: Duncan Gibbons1; Paul Witherell1; 1NIST
Metal additive manufacturing processes are influenced by many variables that affect the produced material to varying degrees. This wide range of variables and the complex fusion mechanisms inherent to these processes often result in a manufacturing process with poor repeatability and reproducibility. This is a qualification and certification concern for critical industries. This research aims to investigate the application of manufacturing reference architectures and models for metal additive manufacturing production definition and control. Such models aid qualification activities by defining critical to quality information and controlling production operations. A systems engineering methodology is utilized to design and develop a reference model for metal additive manufacturing operations. A case study is performed to demonstrate how the developed reference model can be leveraged to define requirements, define operations per STEP-NC, and generate machine-readable process control files. This demonstration illustrates how critical to quality data is captured and managed within the system model for compliance purposes. The proposed reference model provides an architecture for developing and implementing operational digital twins.
2:30 PM
Process Optimization of Diode Point Melting Using Ti6Al4V in Laser Powder Bed Fusion: Alkim Aydin1; Erhan Cetin1; S. Can Erman1; Kamran Mumtaz1; 1University of Sheffield
Diode Point Melting (DPM) is a novel additive manufacturing approach that can produce by focusing multiple diode laser sources into a single beam spot, offers an alternative approach to traditional laser powder bed fusion techniques. With this motivation, this work aims to determine optimum process parameters of DPM using 450 nm low wavelength multiple diode sources. In this study, Ti6Al4V powder used as a production material with different laser powers (19W and 38W), different hatch distance (50, 75, 100 and 125 μm) and different layer thickness (30, 60, 90 and 120 μm) and different speed (800, 1200, 1600 and 2000 mm/min) were considered as process parameters. The results showed that samples with density up-to 99.4% can be produced by using the optimum process parameters obtained. The results also revealed that DPM approach reveals the potential of a promising production method according to traditional additive manufacturing techniques.
2:50 PM
Controlling AM Microstructures through In-situ Laser Annealing and Rapid Post-processing Optimization: Kaila Bertsch1; Connor Rietema1; Jennifer Glerum1; John Roehling1; William Smith1; 1Lawrence Livermore National Laboratory
Current methods for controlling metal AM microstructures (and therefore properties) can be limited, e.g. by native process parameters, or prohibitively slow, e.g. empirical determination of post-processing. To reduce these constraints, a framework for controlling microstructures was developed using in-situ annealing and rapid post-mortem heat treatment screening. To control phases and microstructure layer-by-layer during printing, we developed a secondary diode laser annealing system for powder-bed fusion. Ti-6Al-4V microstructures were controlled as a function of depth by pulsing the diode laser at different frequencies. For alloys that cannot be annealed in-situ, a Gleeble thermomechanical simulator was used to rapidly screen post-process heat treatments. Resistive heating was used to apply a temperature gradient to AM components to evaluate microstructural evolution and phase transformations across a range of annealing temperatures in a single sample, eliminating a critical bottleneck. Together, these developments create a framework for printing novel alloys in an agile, efficient way.
3:10 PM Break
3:40 PM
Local Porosity Detection in LPBF Manufactured Aluminum Parts by In-Situ Multi-Sensor Monitoring: Berkay Bostan1; Shawn Hinnebusch1; Alexander Groeger2; Austin Tiley3; Dimitri Papazoglou3; John Middendorf3; Christopher Barrett2; Albert To1; 1University of Pittsburgh; 2Laser Fusion Solutions; 3Ohio State University
Laser Powder Bed Fusion (LPBF) is renowned for its precision in fabricating intricate components. However, addressing porosity in LPBF-produced parts is a significant challenge, especially in high-precision applications. This research introduces a specific porosity detection framework for aluminum parts. It utilizes a variety of sensors, including long-wavelength infrared camera, recoat camera, and thermal tomography. This approach yields over 90% accuracy in detecting pores smaller than three times the sensor resolution while keeping the false positive ratio below 2%. Furthermore, the method consistently achieves 99% accuracy in identifying pores larger than 400 microns. The study also outlines each sensor's distinct role in detecting different porosity sizes, underscoring the importance of sensor selection for precise detection. Ultimately, this research significantly enhances porosity prediction in LPBF-manufactured aluminum parts and emphasizes the critical role of sensor choice across different porosity ranges.
4:00 PM
An In-situ Eddy Current Diagnostic for Monitoring Sub-surface Temperature During Metal Additive Manufacturing: Saptarshi Mukherjee1; Ethan Rosenberg1; Edward Benavidez1; Peng Lei2; Yiming Deng2; Joseph Tringe1; David Stobbe1; 1Lawrence Livermore National Laboratory; 2Michigan State University
With the increase in laser powder bed fusion (LPBF) additive manufacturing applications, an in-situ sub-surface temperature monitoring diagnostic is critical to determine the thermal stress distribution of a metal AM component. Current temperature monitoring diagnostics provides limited information on sub-surface melt pool temperatures. Here we develop an eddy current (EC) diagnostic that can monitor sub-surface temperature distribution during a thermal heating process, by detection of sub-surface induced eddy currents that are perturbed due to the material’s electrical conductivity variation from temperature fluctuations. A commercial EC system is integrated in a laser-based system and detects temperature changes from laser heating initially followed by late time cooling. These experiments also help benchmark EC signals to temperature, as we transition the EC experimental system to an in-situ sub-surface temperature monitoring diagnostic for LPBF.
4:20 PM
An Acoustic-based Witness Coupon Methodology: Conor Porter1; Jian Cao1; 1Northwestern University
Post-build validation of part quality is a key step for the certification of parts produced by additive manufacturing. Current validation methods, such as X-ray CT scanning and destructive witness coupon testing, can provide high-resolution and detailed data, but are expensive and time consuming to implement. This work presents a novel acoustics-based witness coupon methodology for time- and cost-effective validation of Laser Powder Bed Fusion (LPBF) part quality. This methodology centers on thin witness coupons built in parallel to the target parts. These witness coupons can be ‘plucked’ and the resulting resonant frequency measured and correlated with the geometric accuracy and overall density of the target part. This work presents an initial design and characterization of these acoustic-based witness coupons using both experimental results and simulations. Results indicate that the correlations to target part density and geometric accuracy can be used to verify target part quality based on acoustic-based witness coupons.
4:40 PM
Evaluation of the Effects of Machining Methods on Fatigue Life and Surface Quality of L-PBF Ti-6Al-4V Parts: Cristian Banuelos1; Shadman Nabil1; Diego Ariza1; Edel Arrieta1; Ryan Wicker1; Francisco Medina1; 1W.M. Keck Center for 3D Innovation
This paper explores the impact of various surface finishing techniques on the flexural fatigue life of L-PBF Ti-6Al-4V components. It analyzes four standard machining methods to evaluate their effects on surface roughness, measured using contact and non-contact techniques. A modified 4-point bending fatigue test was conducted on the specimens at four maximum stress levels. Detailed fractography was employed to investigate the fracture surfaces and identify the failure mechanisms. Microhardness tests on the specimen surfaces were also performed, with results compared against fatigue performance. The findings indicate that while machining improves the fatigue endurance of L-PBF Ti-6Al-4V parts compared to as-built ones, improved surface quality in machined parts does not necessarily correlate with better fatigue performance. The opposite was observed, potentially due to work hardening that affects the mechanical properties of the specimens.
5:00 PM
Re-Imagining Additive Manufacturing through Multi-Material Laser Powder Bed Fusion: Jacklyn Griffis1; Kazi Shahed1; Kenneth Meinert2; Buket Yilmaz1; Matthew Lear2; Guha Manogharan1; 1Pennsylvania State University; 2Applied Research Laboratory at Pennsylvania State University
Multi-Material Laser Powder Bed Fusion (MM-LPBF) offers a novel approach for fabricating high-resolution components with both spatially tailored material properties and design by capitalizing on selective powder deposition (SPD) in conventional LPBF processing. Advancements in multi-material additive manufacturing (AM), specifically MM-LPBF is now presenting a unique opportunity to re-imagine additive manufacturing design complexity to achieve spatial functional design requirements. In this study, the fracture mechanics of complex multi-material structures is investigated through multi-scale domains, including mechanical testing (with digital image correlation), finite element analysis, and intermittent micro-CT), microstructural and morphological characterization of the bimaterial interface. This study analyzes the contribution of factors such as thermomechanical material compatibility, process induced interfacial defects and microstructure to determine the ultimate origin of failure. Interface formation mechanisms are explored to elucidate process-structure-property framework for MM-LPBF. Findings study demonstrate both the opportunity of MM-LPBF and current technological challenges to advance the adoption of MM-LPBF.