Cookie Monster Yo-Yo:
An Exercise on Mass Manufacturing Processes & Techniques
Yo-Yo Design
Overview of Design
Press Fit and Thickness
Mold Designs
Face
Top Ring
Body
Cookies
Milling and Injection Molding Difficulties
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Press Fit dimensions require long machining time
Need to optimize machining operations
Utilize different tool sizes to minimize tooling time
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Determine errors that are causing molds to be defective
Manage quality control
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Ejection Issues in IM process due to multiple factors
Too small of draft angle, no ejector pins, lack of mold release, incorrect IM settings, etc.
Fine-tune IM parameters to eliminate flash, short shot, and other issues
Data Collection
At the end of the project, we collected the 50 yo-yos we made and checked them against our original design.
During the term, we changed our press fit spec from 0.010” to 0.0145” because we didn't allow for enough shrinkage in our first calculation. We found that the "Ring Inner Diameter" and the "Body Outer Diameter" were both larger than our specifications, but the distribution was good.
The interference fit was smaller than expected, but all yo-yos had some interference fit, which was a positive outcome. In the future, we will likely adjust the cooling time, packing temperature, and packing pressure to improve the interference fit.
