Phase3D is excited to share the highlights from a recent scientific study by our collaborators at the Illinois Institute of Technology (IIT), titled “Does Selective Shell Printing Advance Binder Jetting Additive Manufacturing?” The study, published in Powder Technology, is available here.
Dr. Amir Mostafaei and his research team explore the intricate dynamics of binder deposition methods, sintering atmospheres, and their effects on the microstructure and mechanical properties of binder-jetted 316L stainless steel components. Our cutting-edge Fringe Research technology plays a pivotal role in capturing heightmaps during the binder jetting process, providing valuable insights into the powder deposition and subsequent binding stages. (See Figure2)
Key Findings of the Study
The study focuses on comparing bulk and selective printing methods in binder jetting, alongside the effects of different sintering atmospheres — vacuum versus hydrogen (H2). Here are some of the critical findings:
- Density and Grain Size Analysis: H2-sintered specimens exhibited up to 5% lower density compared to vacuum-sintered parts, with a final density of 99.7%. The grain size in H2-sintered parts was smaller (∼26 μm) compared to vacuum-sintered parts (∼33 μm) due to residual pores impeding grain growth.
- Mechanical Properties: H2-sintered specimens showed an elongation of 25% and an ultimate tensile strength (UTS) of 460 MPa, whereas vacuum-sintered parts demonstrated significantly higher elongation (70%) and UTS (550 MPa).
- Fractography Analysis: Vacuum-sintered samples revealed ductile fractures, while H2-sintered parts exhibited a combination of brittle and ductile fractures due to remnant pores in the microstructure.
The Role of Fringe Research
Fringe Research was used to capture real-time heightmaps of the binder jetting process. By meticulously measuring the height during powder deposition and post-binding, the researchers were able to identify process anomalies that may lead to defects in the final product. This real-time monitoring allows researchers to ensure the consistency and quality of the binder jetting process. Ultimately, this enhances the reliability of manufactured parts and empowers users to improve the process.
To quantify powder bed uniformity and identify in-process defects, Phase3D’s in-situ inspection system provides objective, unit-based data from every layer of the powder bed. Unlike camera-only systems or diode-based monitoring, Fringe Research uses a patented structured light system which is retrofit onto the AM system without interfering with the printing process. Fringe Research measures the height of exposed surfaces of powder-based AM process before and after binder deposition for every layer. These heightmaps are sensitive to primary in-process part failure mechanisms, such as inadequate powder coating and out-of-plane part deformation. Fringe Monitoring Software v1.1+ was used to detect powder layer defects, generating 3D heightmaps sensitive to striations, depressions, and clumping. The data gathered after binder spraying allowed for comparing heightmap measurements to visualize in-process defects during binder-powder interactions with a 10 µm resolution. (See Figure 2 Below)
Impact on Binder Jetting Additive Manufacturing
The insights gathered from this study underscore the transformative potential of selective shell printing in binder jetting AM. By minimizing binder usage and expediting de-binding, shell printing not only enhances the efficiency of the process but also ensures compatibility with binder-sensitive materials. The research revealed that vacuum sintering, coupled with selective shell printing, offers superior densification, reduced porosity, and enhances mechanical properties compared to traditional bulk printing and H2 sintering methods.
Future Perspectives
The integration of Fringe Research technology into the binder jetting process marks a significant advancement in the field of additive manufacturing. By enabling precise detection of height anomalies, Phase3D’s technology paves the way for more accurate and defect-free production of complex parts. Moving forward, Phase3D aims to further refine Fringe Research capabilities and explore new applications across other additive manufacturing processes.
Conclusion
At Phase3D, we are committed to pushing the boundaries of additive manufacturing through innovation and research. The findings from this recent study highlight the critical role of selective shell printing and vacuum sintering in enhancing the quality and performance of binder-jetted components. With Fringe Research, Phase3D is poised to lead the way in delivering cutting-edge solutions for the additive manufacturing industry.
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