This week we had to tackle molding and casting, which was a new technique for me that I have never used before. I found that I liked it quite a bit, and the ease of use to mass produce a part from a single mold was pretty impressive. Like other techniques, I had some problems with it, but nothing too crazy this week, so I will now go into the process I followed to cast molds of my fingers.

Creating a Mold 

The first thing I did was create the alginate mixture by using a ratio of alginate to water of 1:4, which proved to be a pretty good mixture. The only problem I ran into this early in the project was that there was not a lot of alginate left by the time I was trying to create my mold, and so there was a low volume alginate in my cup for my mold. This caused some problems because my fingers are kind of big, so I had to put them in at a weird angle to completely submerge my finger. Because of this, the entry point of the negative was not completely flat to the mold, but was at a strange angle that will become more evident when the first finger I make is shown.

Casting My Fingers

Next up I prepared my plaster, which I started with a 2:1 ratio of water to plaster by volume, but I felt that the mixture was a little too thin, so I decided to add more plaster to the mix until I got a thicker consistency similar to a milkshake consistency. From there I went ahead and poured it into my mold, and had a bit of the plaster spill out of the mold due to the uneven way I put my finger in to cast the mold. Because the volume was pretty low, I also had to hold the screw in the best I could for 10 minutes, and then afterwards it had set enough so that I could take my hands off it and it stood in there on its own. After about 30 minutes I took the cast out and as you can see below there were some problems with it, such as the access amount of plaster at the base of the finger, and the finger nails getting messed up during the cast. Because the entry hole was at an odd angle as well, you can slightly see the screw poking out.

Post Processing

To post process my fingers, I went ahead and shaved off all the excess plaster at the bottom of the finger to actually return the cast to an actual finger like shape for the hook. After removing excess plaster, I also went ahead and sanded a few features on the finger, such as fixing the nail to have the correct shape, and not have the broken nail look that it had when I first pulled it out of the mold. After polishing it with 120 grit sandpaper, I went ahead and gave it a clear coat because I found the cast was a little powdery, and my hope is that the clear coat will keep all the plaster stuck together for a cohesive and finalized piece.

Cost Analysis:

Labor: $15/hr x 2hr = $30

Alginate: About $2

Plaster: About $1

Screws: $0.20

Clear Coat: $0.10

Total: $33.30