Tide pod yo-yo's were the result of a term project for the Design and Manufacturing II (2.008) course at MIT. The goal of the project was to design a yo-yo with at least three injection molded parts and one thermoformed part, design molds for both injection molding and thermoforming, and mass-produce enough parts to create 50 functional yo-yo's.
Our team of five people designed a yo-yo with two main features. One (mostly aesthetic) feature were the colored pods used to convey the tide pod theme of the yo-yo. The pods were made from a clear thermoplastic material and was formed with a thermoforming process. The protruding cavities were then filled with clay during final assembly both to provide color and add weight to the yo-yo for better functionality. The second feature was the inclusion of small tabs along the outside of the yo-yo to create a twist fit between some of the injection molded parts. These tabs served to provide extra mechanical strength to resist fracture during a drop test (one of design requirements).
The project was mainly an exercise in design for manufacturing. My primary responsibilities on the project were to:
Complete the CAD design of the yo-yo
Create CAM programs for the molds of the injection molded parts
Assist with injection molding process optimization and production runs
When designing each part of the yo-yo, there were a few important design considerations both to provide mechanical strength in the final product, to ensure that molds could be machined for each part, and to prevent defects in the produced parts. First, the injection molded parts needed to designed to have a small, uniform thickness to ensure short cooling time and to prevent warping. Second, because the design has undercuts due to the the twist fit feature, we needed to guarantee that a parting line existed on all parts that would be accepted by the mold design tool in Solidworks. Finally, although we wanted the tabs to be as small as possible to avoid interfering with functionality, we were ultimately limited by the dimensions of the smallest mill tools available and the required strength. The tabs were designed to have a large height and a relatively small length in order to resist bending stresses that may cause the parts to fracture.
In testing, the yo-yo's proved to be extremely robust to dropping. They could be repeatedly dropped from a height of approximately five feet with no noticeable damage. Additionally, they were dropped from a height of approximately 20 feet with only minor damage that would not have impacted the functionality of the yo-yo!