Additive Manufacturing: Beyond the Beam II: Binder Jetting
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Powder Materials Committee, TMS: Additive Manufacturing Committee
Program Organizers: Paul Prichard, Kennametal Inc.; James Paramore, Texas A&M University; Peeyush Nandwana, Oak Ridge National Laboratory; Nihan Tuncer, Desktop Metal
Wednesday 8:30 AM
March 17, 2021
Room: RM 4
Location: TMS2021 Virtual
Session Chair: Paul Prichard, Kennametal
8:30 AM
Introductory Comments: Additive Manufacturing: Beyond the Beam II: Paul Prichard1; 1Kennametal Inc.
Introductory Comments
8:35 AM
A Look into Solid-state Metal AM Techniques from Metallurgical Bonding Perspective: Nihan Tuncer1; Animesh Bose1; 1Desktop Metal
Although significant commercial and academic resources have been invested in beam-based metal AM, challenges associated with repeated local melting and processing complexity along with high cost equipment and operation are making solid-state AM methods an attractive alternative. In this talk, we discuss the capabilities and challenges of major solid-state AM techniques in two broad categories, deformation-based and sinter-based, based on the metallurgical bonding mechanisms. Limited data available in literature shows that while deformation-based techniques are primarily limited to relatively ductile alloys, a larger variety of materials are suitable for manufacturing through sinter-based AM. Deformation-based methods generally refine the microstructure by recrystallization, while in most cases sinter-based AM methods lead to grain growth due to high temperature processing and a more isotropic microstructure. Among the solid-state AM methods summarized here, binder jetting and additive friction stir AM methods stand out with isotropic microstructures and mechanical properties close to the wrought properties.
8:55 AM
Development, Characterization, and Modeling of a 3D Binder-jet Printed N95 Metal Filter for COVID-19: Aaron Acierno1; Katerina Kimes1; Erica Stevens1; Pierangeli Rodriguez1; Steve Pilz2; Kyle Myers3; Patrick Dougherty3; Kurt Svihla2; Thomas Spirka4; Markus Chmielus1; 1University of Pittsburgh; 2ANSYS; 3ExOne; 4Synopsys
In response to the ongoing COVID-19 crisis, the development of a reusable and self-sterilizing 3D-printed N95 respirator filter is crucial in limiting the spread of the virus while masks are in short supply. Currently, 3D binder-jet printed metal filters are considered as an alternative to surgical masks due to antimicrobial properties present in some metals and intentional porosity introduced during the printing process can be fine-tuned through printing and sintering parameters. Micro computed X-ray tomography (microCT) was used to characterize porosity, tortuosity, and density of 3D binder-jet printed metal filters to compare sintering temperature, time, and material at the microstructural level. 3D modelling was also performed using meshes created from microCT scans to assess pressure drop and flow characteristics of 3D-printed filters. Our work shows that microCT is a powerful tool in non-destructive characterization and simulation of 3D-printed filters and that measurements can be performed quickly and accurately.
9:15 AM
Effect of Processing Defects on Properties of Binderjet WC-Co: Paul Prichard1; Hadi Miyanaji1; Zhuqing Wang1; 1Kennametal Inc.
The binderjet process has been used to process a variety of metal, ceramics and polymers. Each material system and powder have unique challenges in the various processes necessary to produce high density components including: printing, curing, debinding, sintering and surface finishing. These processes may introduce defects, which influence the product performance. The WC-Co system has a specific set of microstructural requirements, which indicate associated mechanical properties. This paper will discuss the influence of inclusions, porosity, large grains, co-pools on the transverse rupture strength to inform the quality assessment from microstructure instead of performing extensive property testing.
9:35 AM
Droplet Powder Interactions in Binder Jet Additive Manufacturing: Trenton Colton1; Nathan Crane1; 1Brigham Young University
Binder Jet (BJ) additive Manufacturing creates geometry by printing droplets of liquid binder into thin layers of dry powder. The interaction of the droplets with the powder is critical to forming dense, defect-free parts. However, this core, highly dynamic, process of BJ is poorly understood. Traditional printing parameters use single global printing parameters. However, this work shows how the printing outcomes are depending on droplet size, droplet velocity, printing pattern, and part geometry. To better understand this process, an extensive experimental study of printing has been undertaken that looks at the impact of these key process variables on the formation of lines, layers, and multilayered parts. These results provide insight into the selection of print saturation and methods to avoid printing defects such as balling during printing.
9:55 AM
Fluid and Particle Dynamics Simulation in Binder Jetting Process: Fangzhou Li1; Wenda Tan1; 1University of Utah
In a binder jetting process, binder droplets are deposited on the powder bed to binder particles together for the printing purpose. The droplets can have rather high impacting speed, which can significantly disturb the powder bed and cause pores in the 3D printed parts. In this work, we will establish a 3D numerical model to capture this complex process. Specifically, a computational fluid dynamic (CFD) module will be developed to simulate the binder flow and droplet deformation, and a discrete element module (DEM) will be developed to simulate the droplet-particle and particle-particle collision. The two modules will be fully coupled to predict the binder droplet impact on the powder bed and the resultant powder re-arrangement. Model-based parametric studies will be performed to investigate the droplet and jetting parameters on the powder bed.
10:15 AM
Gravity Influence on Sintering of Binder Jetted Components: Elisa Torresani1; Eugene Olevsky1; Randall German1; 1San Diego State University
Powder components subjected to sintering should ideally homogeneously shrink and retain their original shapes. However, the real-world materials processing is influenced by many factors (e.g. temperature non-uniformity, external friction forces, and gravity) which during sintering cause inhomogeneous densification and shape distortions in final products. These issues also affect powder components obtained using additive manufacturing technologies, such as binder jetting and ceramic stereolithography, followed by sintering. Therefore, the fundamental understanding of the sintering process and the different sintering-influencing factors is of great importance for the development of modeling tools able to predict the resulting shapes and properties of the final sintered 3D-printed components. In the present work, a finite element model is developed in order to predict the sintering behavior of 3D-printed specimens under the influence of gravitational forces. Subsequently, the model results are validated through the comparison with the experimental test outcomes.
10:35 AM
Distortion Modeling of Sintering Process in Binder Jet Printed Parts: Basil Paudel1; Dave Conover2; Albert To1; 1University of Pittsburgh; 2ANSYS Inc.
During sintering of binder jet printed parts, distortion, often anisotropic, is seen with shrinkage values in the range of ~5-20%. The geometry and complexity of the part combined with the sintering stress and high temperature creep makes prediction of the final part geometry more difficult, thus hindering its wide adoption in the industry. In the present study, a viscoelasticity based constitutive model is adopted to predict the distortion during sintering of the stainless steel 316L BJP parts. The effects of friction and gravity are considered. The model is coded as a usermat subroutine and applied in ANSYS Mechanical APDL to simulate distortion in a part. An evolutionary algorithm (EA) is utilized to identify material specific constitutive parameters. The shrinkage results from the numerical analysis using identified parameters were validated against the experiment. It is shown that the proposed model agrees reasonably with the distortion data obtained during the sintering process.