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3D-Printed Spinning Disk

The Magnetic Spinning Disk is the very first project that I received just when I started my freelance CAD modelling and 3-D printing service back in December 2020 after completing my Additive Manufacturing course. To this day, I still think of this project as the most interesting project as I learned a lot more about DFM in FDM 3D printing.

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First Design Iteration

The picture shown above is the very first sketch provided by the client. The idea of this project is that the client wants to create a disk with cylinder magnets inserted into the disk's side. The left picture shows the very first sketch with some general ideas.

After creating the CAD model and printing it out, I noticed that one side of the disk was not flat, which led me to believe that this would cause a lot of wobbling when the disk spins. This proved my suspicion that it would not be ideal to have too large surface area in contact with the print bed as the temperature change would cause the part to warp due to thermal contraction. As a consequence, as some areas of the disk experienced thermal contraction it affected the overall disk’s center of mass, which caused it to wobble as it spun.

 

The printed supports were also a problem of this design. As shown in the video, since the supports were too dense creating small gaps on the magnet hole, it was very difficult to take these supports out with a cutter. Additionally, since there were no holes on the top and bottom surfaces of the disk, there was essentially no other place to prob the supports out of the part. 

Second Design Iteration

After studying the problems from the first design, I addressed these issues to my client as I started creating the second design iteration of the disk. Instead of full circle on top and bottom surfaces of the disk, I created spokes (like the ones in car wheels), which tremendously reduced the amount of surface area in contact with the print bed, consequently reducing warpage.

After this design had been printed out, I enjoyed the aesthetic look of it, which was enhanced by the fillets I created on the spokes. Having the fillets are also important for FDM printing as it provides more time for the extruder to slow down and take corner before re-accelerating, as opposed to having sharp corners

Although this design helped reduce warpage, I was still having difficulty taking the supports out of the magnet hole. Again, this was the same problem as the first design.

Overall, this design slightly reduced warpage, but the part was still wobbly at this point. I was also still having difficulty taking the supports out of the magnet hole. In summary, the problems from the first design were mitigated but not completely resolved.

Third Design Iteration

At this stage, I exchanged with my client as an opportunity to collaborate and looking for some insights to address the support removal issue. The client suggested two through holes to be created on each spoke from the top to bottom surface with the idea that the magnet cylinder (of different sizes) could be inserted into these holes. To think about it, the 21mm-diameter hole would be advantageous for me as well as it provides an optimal location for me to insert my cutting tool and push the support out of the original magnet hole out of the disk.

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In addition, I also made the spokes smaller while keeping the all the holes in hope to further reduce more surface area that would be in contact with the print bed. The picture on the left shows my third and final design iteration of the disk. 

Results

After the third design had been printed out, the first thing I did was to test the surface flatness of the disk. Just like I did with the first design, I pushed the disk against a desk to see the whole surface touched the desk, and it did! After handing all of the printed parts to the client and completed the project, I received a video of his completed personal project. However, when I noticed, the disk was still wobbling. At that point, I learned that although this part still wobbled as it spun, it could have been worse if the first or second iteration was used.

 

This project was completed in the second week of January of 2021. At that time, I used Ultimaker Cura as the slicing software which allowed me to play around with the print setup including infill density, layer height, and print speed. I was completely new to the software at that time and was not aware the the support density could also be adjusted. If I had known this earlier, it would have helped me a lot with solving the support removal issue, as creating the magnet holes did not require dense supports. I began to discover this setup as I explored other slicing software such as Simplify3D

Since the Creality Ender 3 Printer was used, the print bed level had to be adjusted manually by rotating the knob on each corner. Because this process was done manually, the first print layer would not be equal as one side would be thicker than the other. As a consequence, the center of mass would not be located perfectly at the disk's axis of rotation, despite having eliminated most of the warping issues.

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Overall, I think this project is a huge success. The client was satisfied with the overall performance of the disk, which gave me satisfaction. This project also had been a great learning opportunity for me to gain more knowledge with DFM for Additive Manufacturing.

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