I worked with a team to design and manufacture a production run of celestial-themed yo-yos. The yo-yo was made from a set of five unique snap-fit injection molded and thermoformed plastic parts. A team member and I designed a base and snap-fit ring which would form the body of the yo-yo.
After doing the initial toy design in SolidWorks, the 3D models were converted into 2D drawings. Using Mastercam, toolpaths were run on the parts to output code for CNC machining. The core and cavity molds were then machined from aluminum blocks. Once the molds were finished, test parts were produced for process optimization. We then manufactured 100 parts which were used to assemble 50 finished yo-yos.
INJECTION MOLDING
Injection molding provided some great teaching moments:
Shrinkage - the initial mold design attempted to account for plastic shrinkage, but the snap-fit ring shrank more than expected and the mold had to be modified.
Burning - when burning was observed in the channels and base parts, vents were added to the mold to allow trapped gases to escape.
PROCESS CONTROL
Controlled changes were introduced in the injection-molding and thermoforming processes to observe the effects on finished parts. Measurements of critical dimensions were used to plot Shewart charts in order to determine whether the manufacturing process was in control.