5. 3D Scanning and printing¶
This week’s assignment was to design and 3D print an object that could not be made subtractively and to 3D scan an object. Our group assignment is to test the design rules for our 3D printers.
3D Printing¶
I started this week by designing my 3D print. I decided to make a case for the programmer board that I made last week. I first imported my .brd file into EAGLE and then exported it as a DXF file that I could import to fusion 360. I used calipers to measure the length of my board and compared it with the length of the side of the DXF file. Since they were the same, I continued modeling, confident that the reference file was to scale.
I started by designing a part that would house my case. I created a simple box around the case, I designed a slot that would allow the board to slide into it, and I created a high roof on the case to avoid the vertical pin headers. I then created a back piece that would slot into the main part. I did this by projecting the edges of the inside of the case and used the offset feature to allow the pieces to slide together better. Finally, I made holes for the pin headers to fit through and I created a small cut in the bottom of one end to allow the FTDI board to fit.
I then printed my case with my Ender 3 that I built in week 2. I saved the file as an STL and opened it in the slicer Ultimaker Cura. I set the print settings to 65mm/s and a layer height of .2mm. I then sliced the file to turn it into gcode. I added this gcode into an SD card, inserted this into my Ender 3 printer, and printed it from my SD card.
Post Processing¶
I used PLA as my material, so the post-processing process was fairly simple. I used a brim for build plate adhesion, so I started by pulling away any excess PLA that was stuck to my parts. I then slotted the two parts of the case together, and they inserted pretty cleanly. I then tried with my programmer board, but I found that it was not able to slide in. I realized that I had two problems that were causing this. The first was because even though the length of the .dxf file I imported as a reference was correct, the width was a few mm too wide. The second problem was that to avoid having to use support, I decided to print my case vertically. This is a problem because the printer was not very accurate while printing this way, and the bottom of the case was not flat.
I decided to redesign my case to be able to print horizontally. I did this by adding a few chamfers to the inside of the case. I set the angle to 45 degrees because I was fairly confident that the printer could handle that angle. I then redesigned my slot piece by projecting the edges of the updated case and using an offset. I then realized that due to the angle, my vertical pin headers would actually run into the case. To prevent this from happening, I offset the parts of the case that the headers would intersect by a few mm and cut out a portion of the case. I then went through the printing process again.
This time, the case came out well. Both pieces slot together nicely, and I was able to fit the board down through the slot. However, I noticed that the end of the case was not sliding in well. I noticed it was bumping up against the crystal. To solve this issue, I used a pair of wire cutters to cut away a small piece to make room for the crystal. The case was then able to assemble well.
3D Scanning¶
For the 3D scanning part of the assignment, I decided to experiment with photogrammetry. Photogrammetry is the process of converting photos, videos, and other forms of media into a 3D object or mesh. I decided to use the software Metashape since its interface looked fairly user-friendly.
To start, I selected the object I would render: a home-run baseball from a Charlotte Knights game.
I took about 130 photos of the baseball, and imported them into Metashape. I then used the “Allign Photos” function to place the photos in the position they were taken at. This function would also build a point cloud from the images. This part of the process took about 2 hours to calculate, and once finished gave me this result:
I then ran the “Build Mesh” function to create a 3D object from the point cloud. This process took about 6 hours to process. once the process finished, I saved the project as a .obj and brought it into Fusion 360. I have never used the mesh features before in Fusion, but its tools were fairly similar to the solid tools. The mesh had a lot of points from around the ball, so I started by trimming away everything but the ball. I then used the “Make Closed Mesh” to make the mesh watertight. Finally, I moved the mesh to near the origin and rotated it so that it was vertical.
I then brought it into Cura. I used the scale feature to bring the baseball to a 1:5 scale with the real-life object. I then uploaded the file to an SD card and printed it.
The 3D scanning process went pretty well. There were some regions where I must not have taken enough pictures since the surface was not entirely smooth, but it came out pretty well overall.
More 3D Printing¶
After finishing my render and programmer case, I decided to make something that 100% could not be made subtractively. I made a small fidget toy for this assignment that would have a ball inside a path. I created a quick sketch with a few rectangles with room for a sphere between them, extruded them, and mirrored them to have a top. I then created small joints between the inner and outer rectangles to hold them together and between the top and bottom, and added a sphere on the inside. I then went through the slicing process again, and 3D printed my design.
The 3D print turned out okay. The print was designed for the ball to be able to roll along all four sides of the rectangle, but the sphere did not print well. This caused the sphere to be elongated on one side, and it was not able to roll between corners. If I were to restructure this idea, I would add spheres in the corner and have a ball on each leg instead of one that goes between all four.
Group Assignment¶
Our group assignment this week was to test the design rules for our 3D printers. Our documentation for this week can be found on our group site.
To do this assignment, we 3D printed four files to test for properties such as infill, overhang, and bridge lengths. My role was to print a benchmark test for our ender 3 printers that included features such as overhang, bridging, and others.
From this week, I learned a lot about the 3D printing process. I learned to think about the 3D printing process while designing an object to make it simpler to 3D print will less room for error. I also learned a lot about the capabilities of the ender 3 printers, and I was very surprised by the high overhang and bridging values possible through the printer.
This week’s files can all be found in this zip file.