Figure 1: Shown above are isometric (a), front (b), and side (c) views of our "Yo!" yo-yo design. The main feature of the yo-yo is the still "Yo!" design which is decoupled from the spinning body via a ball bearing. Upon throwing the yo-yo, the "Yo!" design is expected to stay not rotate with respect to the eye of the viewer.
Figure 2
Figure 2: From left to right: an assembled mirror-image half of the yo-yo with the axle still screwed in it (yellow, red, gray), the body of the yo-yo (red), the bearing (green) which is press-fit in the body, the "Yo!" design (teal) which is press-fit into the bearing, the transparent cover (magenta) which will provide a window to the "Yo!" design, and the overlaying ring (yellow) that snaps onto the body and holds the cover in place.
Figure 3
The assembly of the yo-yo is described in the following steps:
- Screw the axle into the body
- Press bearing into the body
- Press stem of design into the bearing; embedded nut will prevent deeper pressing of bearing
- Lay cover over the body so that flange covers the rim of the body
- Press ring over cover/body interaction and snap onto body
- Repeat to the other side
The manufacturing process influenced our designs considerably. Thermoforming can't keep tight tolerances like injection molding can, so early in the design process, we realized that we couldn't rely on having the cover snap into the body. Thus we took an action to add an outer ring that would snap over and onto the body and hold the cover from moving through pressure and friction of the small flange on the cover. Additionally, sharp corners have to be removed from the parts to optimize the forming and cooling of thermoformed and injection molded parts. Lastly, thought was put into the removal from molds and thus draft angles were added to parts in appropriate locations.
