This week we were molding and casting a 3D design. I was hoping to make something functional, but struggled at first to come up wiht an idea. When I got a feel for someone else’s final cast, I realized a hollow shape could make some sound when struck. I set out to make a “musical instrument”. Due to media lab sponsors week, I didn’t attend the lecture for this assignment, so…. Lots of mistakes.
The first thing I did was design the musical pipes in inkscape, then extrude them in blender. I implemented the diameters of the columns using 10 linear steps between 0.2 inches and 1.0 inches. I used the measurement from the lip of the cast-cup in the image above to determine a workable width for the circle edges of the columns. I thought everything was going to be easy-peasy when I went to mill, so I packed everything pretty tight.
When I went to generate a toolpath, I realized that the musical pipes were too narrowly packed for the ⅛” bit to mill-out. This led to artefacts such as the connections between the pipes and the outer edge, as you can see below. In order to fix this, I redid the design to separate the pipes further apart. At this point, I thought everything was done, but to my surprise, I recalculated the toolpath and found that it would take ~2 hours to cut out my design.
My design was heavy in the z direction (to give the pipes extra height). This is cool, but would require a long period of time to cut. In order to reduce this time, I removed the outer edges of the design. Tom also increased the feed-rate, and we agreed to skip the finishing pass. This resulted in a 30 minute milling time.
Removing the outer edges would come back to bite me later during the casting process.
¾ of the way through milling, the bit broke off inside of the design. This was the result of the bit being fastened too low inside of the desktop shop-bot. This caused strain and eccentricity in the bit, which eventually snapped. The reason for mounting the bit so low was to get as much cut in the z-direction as possible.
Despite the bit breaking, most of the design was finished, and was good enough to form a mold from.
The finished positive was filled with oomoo and a mold was formed. There were two issues with this mold-positive:
Not having outside edges really made pouring the final-cast material difficult. I tried the tape around the top trick, only to have the tape seap through the container and onto the foom hood area (which i wiped down). I couldn’t figure out another alternative to create a frame beyond hot gluing wood to the outside. That being said, I tried another solution, which was to use a box cutter to manually remove a certain part of the middle between the pipes in order to build a frame.