assignment: design and 3D print an object that could not be made subtractively
what I made: small 3D printed milk bottle
assignment: 3D scan an object (and optionally print it)
what I made: a scan of my own upper body, for printing a bust
This week's project was very straightforward - design and print something on the 3D printer. Coming into this class, I was not particularly experienced in CAD modeling and the few projects that I had done were built up using laser cut pieces. I wanted to create something that (1) had geometry that wasn't too complex and (2) might be actually useful in my everyday life.
I started off with wanting to make a Klein bottle (topographical shape) but had a lot of difficulty building the model in Autodesk Inventor. Hollowing out the shape when it had intersecting geometry turned out to be a problem for Autodesk Inventor. I wrestled with Autodesk forum posts for a couple hours struggling to get the geometries designed in the right order. It turns out that successful Klein bottle designs rely on equation based surfaces whose implementation in Autodesk Inventor is outside my skill level (at least for implementation within a week's time). So instead of a Klein bottle, I went with the almost equally aesthetically pleasing milk bottle.
The design of the milk bottle began with constructing a radial profile as a sketch that I could then revolve to get the 3D shape. Both the bottom of the bottle and the top part are rounded - the bottom part with the arc of a circle, the top part by a custom spline. The neck of the bottle is straight lines coming off of the spline region. The sketch profile was revolved to create the initial solid geometry for the bottle
The next step was to hollow out the bottle so that it could actually store things. This is the step that truly makes this project something you could not make purely subtractively - a lathe would have a difficult to impossible time hollowing out the inside of a bottle with curvature like this whereas a pottery wheel would be ineffective at a scale as small as this. I used the "shell" feature on Autodesk Inventor to hollow out the middle of the bottle shape.
At this point, the bottle was hollow inside but did not yet have an opening at the top. This was fixed by adding a "hole" feature to the top of the bottle. Centering the hole was surprisingly difficult as the "hole" feature in Inventor requires some sort of reference geometry. I ended up sharing the sketch used to revolve the bottle to the higher level plane allowing me to use the center line of the bottle to allign the hole.
I printed the bottle using the 3DWOX Sindoh 3D Printer. It was incredibly easy to load the file in for printing and there was minimal setup because the printer already had a white cartridge installed. The total print time for the job was 1 hour and 11 minutes (for an object 2cm*2cm*4cm large).
The second part of the assignment was to 3D scan an object. In this case, the object of consideration was my upper body. The 3D scanner was a Malyan 3D scanner and it looked a little bit like a staple gun. The scanner was set up with its own software on a Macbook and I simply had to sit and spin slowly while the scanner scanned my upper body. I initially tried having someone walk around me with the scanner, but it turns out that that method doesn't work at all. The proper way to 3D scan is to keep the scanner stationary and move the object that is being scanned. After four unsuccessful attempts, the fifth attempt yielded this:
Not the most flattering image (especially around my nose where I appear to have gotten in an accident of some sort) but that is certainly recognizable. The file type outputted by the scanner was a .ply file and to prepare the file for 3D printing, I had to change the file type extension to .stl. The result was this beautiful bust, viewable in FreeCAD.
Why, he doth bestride the earth like a Colossus. Not bad.