This week I decided to make a bowl.
I designed the bowl in FreeCAD. I opted to add a set of contours to the bowl using the "Loft" function in FreeCAD. This function can take several two dimensional shapes along the Z-axis and connect them into one smooth shape. To make the bowl I made 7 concentric circles of various diameters and then moved them along the z-axis. I then used the Loft function to connect them.
I made the mold using the Shopbot CNC mill in the Harvard Science Center. I used a square piece of styrofoam, which I attached with tape.
The first cut was a rough cut and the second time around was a finer final cut. Although the bowl wasn't perfectly smooth, it came out well.
I cut away the borders and was then ready to make my bowl.
I cut out three layers of burlap of apporoximately the right size to cover my mold. I then mixed the Epoxy resin with the hardener in a 2:1 ratio. I spread the resin homogeneously over each piece of burlap. I then started assembling my composite sandwich. In order, from the bottom up: mold wrapped in plastic wrap and sprayed with release spray, three pieces of burlap, another piece of burlap and breather layer wrapped in plastic wrap and sprayed with release spray (and punctured with small holes). I then put all of this in a vacuum bag which I sealed.
I connected the vacuum and let it run, but Rob later informed me that my vacuum bag was leaking so he took it out and put a large bag of water on it.
I left it overnight and retrieved my masterpiece the next day.
After rounding out the edges with large scissors, my bowl was ready for action. One could imagine, for example, that my bowl would function magnificently in holding 3-5 medium sized pieces of fruit.
Regular readers of my webpage may recall that I like my creations to have multiple functions, such as both holding things and acting as hats (example from week 2)
I am pleased to report my bowl fared well in its alternative usage.
