Design Review
The Fro-Yo!
We each brainstormed ideas of how to make a Fro-Yo, and we met together to create one cohesive design, which is shown in the picture below.
Our initial drawing of our Fro-Yo idea. We wanted to thermoform the froyo piece and injection mold the cup, snap ring, m&m's, and cherry.
We originally wanted to do a waffle cone cup design inspired by this picture. However, we decided to go with a plain cup instead to prevent undercuts in the injection molding process. Our initial design in Fusion is shown to the right
The fro-yo piece will be thermoformed with depressions in it, in which we will glue our M&M pieces. We chose to thermoform the froyo piece instead of injection molding it, because it will be less heavy, and it gives us the opportunity to print a texture on the thermoforming plastic stock. In addition, thermoforming it will allows us to easily use the snap ring to attach it the cup. However, the froyo helical pattern will have undercuts, so we changed the design.
New froyo piece to prevent undercuts. No depressions are shown, because we decided to eliminate the m&m's due to high manufacturing time as well as difficulties in injection molding several different colors.
We plan to use Wikki Stix for the cherry stem, because it's stiffer than plain string but not sharp. Essentially, they are just string covered in wax.
Assembled Fro-Yo!
We also plan to use bearings in our yo-yo, and modify the standard internal design (shown above) slightly to accommodate this. The bearings we found that we thought would be best for this design were quoted at $3.80 (ABEC Class 3) from Action Bearing and have an inner diameter of .25", which means they could slide onto the default axle spacer. They also have an outer diameter of .375" and a width of .125". This presents an interesting challenge, since .125" is larger than the gap width of .075" necessary for the string to properly catch the side of the yo-yo and return. We could add .025" clearings on both sides of the yo-yo that the bearing could fit inside, allowing us to keep our gap width low while still using the thick bearing. We could also use the .125" gap and utilize something called a starburst response.
The starburst response is essentially raised protrusions in a star shape on both sides of the yo-yo. This will allow us to keep the larger gap width while still giving the string something to catch on to in order for it to wind back up properly.
