2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Process Modeling
Program Organizers: Joseph Beaman, University of Texas at Austin
Tuesday 1:40 PM
August 15, 2023
Room: 615 AB
Location: Hilton Austin
Session Chair: Conor Porter, Northwestern University
1:40 PM Cancelled
A General Model of Hot Isostatic Pressing for Additively Manufactured Metal Component Performance Improvement: Lei Yan1; Wei Gao1; Nagaraja Iyyer2; Yuyi Mao3; 1Nanjing University of Aeronautics and Astronautics; 2Technical Data Analysis, Inc.; 3Wuxi Institution of Inspection, Testing and Certification
Hot isostatic pressing (HIP) has become an essential post-heat treatment to eliminate internal porosities and tailor microstructure for additively manufactured metal component performance improvement. In the present work, a finite element model based on creep and plasticity that is capable of pore closure evaluation was developed for the HIP cycle process window development. HIP soak temperature, soak pressure and initial pore size effects on pore evolution were investigated on Ti-6Al-4V additively manufactured components for model validation. The proposed model is effective in predicting pore evolution during the HIP process and provides a promising tool for additively manufactured components post-heat treatment process optimization.
2:00 PM
Laser beam shape optimization: Exploring alternative profiles to Gaussian-shaped laser beams in powder bed fusion of metals: Vijaya Holla1; Philipp Kopp1; Jonas Grünewald1; Patrick M. Praegla1; Christoph Meier1; Katrin Wudy1; Stefan Kollmannsberger1; 1Technical University Munich
Laser-based powder bed fusion of metals (PBF-LB/M) commonly utilizes Gaussian-shaped laser beams characterized by a high intensity at the center. However, this type of profile leads to localized high temperatures and temperature gradients. When the laser power is increased beyond a certain threshold, the temperature inside the melt pool can reach the boiling point, causing excessive metal evaporation, hydrodynamic instabilities, and undesired effects such as keyholing. On the other hand, ring-shaped laser beams generate a more uniform temperature distribution but tend to produce shallower, wider, and shorter melt pools with reduced resolution compared to the Gaussian profiles. The deep, narrow, and elongated melt pools generated by the Gaussian shapes still have advantages for increased precision in the PBF-LB/M processes. This contribution uses numerical optimization to generate a new laser beam shape that also leads to a deep, narrow, and elongated melt pool, similar to a Gaussian-shaped beam, while maintaining a lower and more uniform temperature distribution inside the melt pool. The resulting optimized laser profile lowers the maximum laser intensity by 40% without decreasing the total laser power compared to the Gaussian profile. The more uniform distribution of temperature with a peak value of just above 3 000 ◦C indicates a conduction dominated process with less hydrodynamic and minimal evaporative effects.This is expected to reduce the associated defects and improve the process stability.
2:20 PM
An Evaluation of a Programmatic Method for the Generation of Finite Element Event Series for Additive Manufacturing Against Machine Print Paths: Chuyen Nguyen1; David Failla1; Matthew Register1; Matthew Priddy1; 1Mississippi State University
A major challenge of using additive manufacturing (AM) processes is determining optimal process parameters for a specific geometry. Finite element (FE) modeling can reduce lead times and costs associated with process parameter calibration by predicting part deformation and residual stresses through the examination of different process parameters. For an accurate process-property relationship, there is a vital need for the simulated print path to resemble the real machine print path as closely as possible when using a moving heat source. This effort evaluated the difference between a new print path event series generator, AMTech, and print paths generated for usage by laser-powder bed fusion (L-PBF) AM systems for part fabrication. AMTech is a pre-processing tool that takes g-code generated with open-source software along with AM process parameters to generate print paths for use with FE simulations. Demonstrating the efficacy of AMTech will enable researchers to streamline their AM process parameter determination.
2:40 PM Cancelled
Characterization of Simulated Coaxial Melt Pool Monitoring Signal Variations Due to Melt Pool Morphology: Conor Porter1; Arash Samaei1; Dominik Kozjek1; Jon-Erik Mogonye2; Gregory Wagner1; Jian Cao1; 1Northwestern University; 2Army Research Laboratory
One barrier to wider adoption of laser powder bed fusion in industry is the ability to qualify and ensure the consistency of parts produced by this process. Coaxial photodiode monitoring sensors can provide a digital signature of a part at the melt pool scale, which can expedite qualification. However, this signature currently includes considerable noise and variation in sensor signals, masking important signatures. While the sensing method and systems contribute to the noise, fluctuations in the melt pool also contribute to variations in sensor signals, which have not been well studied. This work analyzes simulated coaxial photodiode measurements of an L-PBF simulation. These simulated sensor signals are compared to fluctuations in the simulated melt pool including variations in width and area. This work provides a preliminary basis for determining how much of the apparent noise in coaxial melt pool monitoring signals may be due to fluctuations in the melt pool.
3:00 PM
Energy Flow (Bond Graph) Dynamic Modelling of Cartesian-frame FFF 3-D Printer Gantry: Maharshi Arindom Sharma1; Albert Patterson1; 1Texas A&M University, College Station
Energy flow (bond graph) modelling gives important information about the flow of energy to each component of a dynamic system and is especially useful for complex non-linear mechanical systems. This work presents a systematic development of a bond graph model of fused filament fabrication (FFF) 3D printer gantry. The model incorporates structural and belt stiffness, damping and input torque. The model was checked for correctness and causality using the 20-Sim software. The model was further validated using Matlab Simulink using parameters obtained for an example printer characterized in a lab environment. The bond graph model gives a unique view into modelling of the extruder carriage dynamics in FFF and can be applied to specific problems. It will also give interesting information on the controllability and system integration of the printer hardware.