Brazing Study
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Problem:
With additive manufacturing, there are size limitations for parts made with the system since the system has a specific build box size. One concept that we wanted to look into was the possibility of combining multiple small parts into a larger part or repairing flawed parts using various post-processing techniques. One technique that we looked into was brazing which utilizes a flame torch and a filler material to connect components. We wanted to see if the presence of infill would affect brazing techniques in any way as the infill creates air pockets within the part which when heated would expand and could potentially pop out.
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Design of Experiment:
For the initial test of this project, samples of flawed parts were collected to test how brazing can repair the minor damages in parts. Certain flaws included cracked parts or delaminations.
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I conducted online research as well as discussions with an MIT professor who is well-versed in brazing to determine two filler materials that are known to work well with our part material which is 17-4Ph. The determined materials were Safety-Silv 45 and 56. Additionally, I decided to conduct the test both with the large tank system of a facility with brazing techniques in place as well as with a handheld butane torch for simulate a solution for customers without the full setup who are in need of a quicker fix.
While working as a co-op at Desktop Metal, I collaborated with colleagues at MIT to develop and conduct a study on brazing metal 3D printed parts. The printing process of Desktop Metal's Studio System which utilizes Bound Metal Deposition (BMD) requires infill to be used within the parts. Because of this, the parts are not fully solid and therefore it is important to test if the parts can have certain processes done on them in the same way that parts made from wrought steel can. For more information on the Desktop Metal systems I worked with, click here​.
Background:
While the additive industry is quickly evolving, it is still a relatively new field and the extension into using metal is even newer. Desktop Metal is expanding this industry to create a solution called the Studio System that is less industrial in that anyone can operate the system without the need for heavy personal protective equipment (PPE). The Studio System utilizes bound metal deposition to build up parts layer by layer. Due to the nature of this process, the parts are made with an infill in order to lightweight the part and allow for a critical debind step to ensure successful parts.
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View of Separation Surface
Part split in two pieces
Results:
It was determined that there was no significant difference between the two filler materials due to their similarity in composition. As for the torch difference, it was obvious that the large cylindrical tank systems gave cleaner brazed connections which was to be expected, but the handheld butane torch also repaired the cracks quite well.
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Since this was a feasibility study, the test I conducted was preliminary to determine that there were no obvious issues with the process and that the brazed joint was relatively durable which was tested by hitting the parts a few times with hammers. After I proved the feasibility of brazing on these parts, the project was handed to the materials team to do in depth testing of whether the brazed joint held up to our material standards.
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There was some noticeable oxidation on the part after brazing, so I was also able to test a few finishing techniques on the part post-brazing. Initially I used a media blaster with alumina oxide media which cleaned up the burned areas; however, it revealed the obvious color different between the printed 17-4Ph media and the Safety-Silv filler media. To reduce this contrast, one weld was cleaned up on a buffing wheel which polished both medias and blended the colors together quite well. Images of the part at all of these stages are provided.
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Part After Brazing
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Braze Welds Media Blasted with Alumina Oxide
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Top Braze Weld Buffed on Buffing Wheel
What I Learned:
Through this project, I learned a new skill: brazing. Since I handled the project entirely and worked, I was able to actually do the physical brazing. With the instruction of a contact at MIT who was well versed in welding and brazing, I was able to braze a variety of parts with different sized cracks and features. I learned a lot about the process and the importance of being thorough in the work. I also learned the correct settings to braze a part as well as the order of the braze. I was able to use gravity to my advantage by melting the filler material at the highest point of the feature and allowing the liquid filler to glide down through the rest of the crack.
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Some of the parts in the test had more unique geometries and required more creative ways to hold the pieces together. I learned the best way to grip the parts without interfering with the key features.
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Additionally, I learned that our materials did not have any significant issues in simple processes such as brazing. All the parts brazed quite well in the process with no issues.