Casting and Molding
This week, we learned about the casting and molding process. This process involves many steps, and there were a few bottlenecks this week, so I haven't yet completed the assignment. Once i finish this week I will document the remainder of my progresss. The first step is to mill or 3d print what you would like to make, using either the roland modela and millable wax, or a 3d printer. I decided I wanted to make a mount for my cycilng computer, and the only way to make this was with the 3d printer. I designed the mount in tinkercad, and then printed it at the labs. It actually does a good job holding the computer when printed in 3d, but if i were to want to make a bunch of these, molding and casting it would be a quicker, cheaper way of producing more than one. 
The next step is to make the mold using OOMOO, which is a two part mold making mix. You mix the parts together in equal quantities, stir for a few minutes, and then pout the mixture over your design, and let it set. My design was pretty complicated, so I had to figure out a way to do it so that all of the overhangs of the model would come out. I decided to suspend the part in OOMOO, in a pepsi bottle, let it cure, and then I cut it out with a razor blade in two parts. This gave me a suprisingly good mold.
After the mold was created, I used a 2 part plastic mixture to cast it. I mixed the two parts together, and then poured the mixture into my mold. I let it sit for an hour to make sure it had hardened. The reaction betwene the two resins was excothermic, and let off a lot of heat, which was pretty cool. I carefully sperated the halves of the mold, and puled out my part. It looked surprisingly good! It even held my bike computer securely!
I let it cure for 24 hours more, and then did a little stress testing. I put some force on the piece, and it snapped much more easily than the original 3d printed peices had when i tested them. I was dissapointed in this, because I was hoping it would be strong enough to actually use when riding. While this type of plastic isn't, I am sure there is another material that I could make with my mold that would be strong enough. One possibility would be to put a peice of metal or carbon fiber inside the main shaft while casting, as a sort of spine. Stay tuned for composites!
