this week, i was inspired by metal casting (not at all expecting how brittle the bismuth-tin alloy actually would turn out to be) and wanted to make some jewelry. i came up with this "möbius" (not with these four "turns") bracelet in rhino with some rectangles placed around a ring and twisted gradually:

i used the little shopbot in the science center basement to make a positive in the machinable wax, which came out with remarkable resolution! i introduced hemispheres in the corners to fit four metal balls that would align the two "halves" of the mold as well as four ducts for the molten material to flow in and out of the mold. i also had to be careful to match the ducts between the two dissimilar mold parts.

i had trouble with bubbles in the oomoo. i tried using the vacuum but it make the mixture bubble so much that i wasn't sure if i was even using it correctly. i ended up trying to tediously break all the visible bubbles by hand.

(ew, oomoo in vacuum)
in the end, the molds turned out fine. probably because the bracelets have so little surface area anyway and the bubbles in the wax just rise to the top when i smash it against the table, far away from bracelet.

one problem with my mold was not having ducts large enough in which the alloy can easily flow. i tried to fix it with an X-ACTO knife:

okay, not terrific but gets the job done.

my major problem this week was actually that the metal didn't flow all the way through, leaving me with stuff like this:

you can see that the failure on the right is also a result of not having had the two pieces of the mold held together firmly enough. i made sure the alloy was hot enough using the wire temperature sensor and quickly poured it into the mold, make sure it was also exiting on the other side and not cooling before even reaching the bottom.

this got the entire circle!

unfortunately it was my sawing skills that broke it in the end. here's a terrible soldering job i attempted:

one final try:

almost. it turned out kiiiinda pretty though (and totally unsuitable for wear)...