I am a member of a group called Team Hack-a-Day. Team Hack-a-Day is the unofficial Folding@Home team for Hack-a-Day. (note: as used on these sites "hack", "hacker", and "hacking" refer to legal activities and people, they have nothing to do with illegal hack/hacking/hacker as reported by the media.) Anyway, at some point, on the Team Hack-a-Day (THaD) forums, those of us with CNC milling machines (or access to CNC machines) decided that it would be cool to make some keychains with the THaD "skull-and-cross-hacks" logo on them.

      Since my machine is not quite strong enough to mill aluminum directly, I decided to mill foam patterns and cast them instead.

      Right now, the only cutting bits I have for the CNC machine are 1/8" diameter. Unfortunately, a cutter with that big of diameter cannot cut the logo small enough to fit on a reasonably sized keychain. Therefore, I decided to scale the prototype up about 2-3 times it's final size until I could get a smaller cutting bit. Anyway, all the pictures on this page are of the prototypes that are about 1/2" thick and 4" in diameter.

First two foam patterns:


Sprues attached:


Patterns being coated in drywall compound:


Drywall compound drying:


Crucible loaded and foundry lit:


Skimming the slag off the molten aluminum just prior to pour:


Castings cooled and sprues and drywall compound removed (note the rounded/unfilled tips of the wrenches):


Parts after being painted black then sanded (to remove the paint from the raised sections):


      The reason that the tips of the wrenches and other edges are rounded instead of sharp is because I did not let the aluminum get hot enough befour the pour. Since the Aluminum was too cold it did not have time to fill the mold completely before freezing.

      Since those two didn't come out as well as I'd hoped, I decided to try again. So I loaded some more foam into the CNC machine and cut out another pattern. I slightly modified the toolpath to make the machining a little faster and more efficient. Anyway, this time i let the aluminum get hot enough to propperly fill the mold and the casting came out almost perfectly. Pics below.

Machine milling a new pattern:


Part successfully cast, painted, and sanded:


      At this point I am ready to try to make a smaller version except that I need a smaller cutting bit for the milling machine (preferably 1/8" or smaller) and some thinner foam (preferably 1/4" thick).