Design and Manufacturing II

Yo-Yo Project

Introduction

The yo-yo project has small teams of students experience designing and manufacturing a simple product at scale. Throughout the project experience, students will have a chance to create a new yo-yo design, develop a computer-aided design (CAD) model, computer numerically controlled (CNC) machine tooling for injection molding using computer-aided machining (CAM), create thermoform tooling using additive manufacturing, and operate industrial injection molding and thermoforming machines themselves. This is an iterative process that allows the students to see the implications of their design details all the way through to final production!

Requirements and Geometric Considerations
Minimum Number of Parts	2 separate injection molded parts, including assembly using a press fit (note: no adhesives allowed) at least 1 thermoformed part
Recommended String Gap	0.075" +/- 0.010"
IM Part Guidelines	all molds must be machined from the standard aluminum blanks: 4" x 4" x 1.5" no undercuts that will interfere with releasing from the mold no side-pull mechanisms maximum volume: 2.70 in3 recommended part thickness: 0.080" +/- 0.010" keep part thickness as constant as possible to avoid shrinkage, warping, dishing weight recommendation: 60g–70g all parts are made with polypropylene (PP) ejector pin holes must be 1/8" in diameter
Thermoforming Part Guidelines	thermoformed sheets come in a stock size of 5" x 5" with a thickness of 0.030" all parts are made out of either clear polyethylene terephthalate glycol (PETG) or white high-impact polystyrene (HIPS) thermoform molds should be made by SLA 3D printing with FormLabs High Temp Resin vacuum hole size guideline: 0.026" (if vacuum holes do not properly print, they can be drilled) no undercuts that might prevent the part from releasing from the mold molds can be shelled to reduce print time, but must survive vacuum application dies for cutting thermoformed pieces have a max diameter of 2.5"
Project Details	teams must produce 50 identical yo-yos team budget: $250 per team drop test: height of 4 feet

Manufacturing Review Rubric

Presentation Structure

• Be ready to present CAD and manufacturing results (quality of your manufactured parts) for all parts of the yo-yo:
  • Bring example parts and molds.
  • Be ready to discuss the biggest challenges and roadblocks your team has overcome.
  • Have a clear outline and description of any remaining issues, including plans for addressing those concerns.
• Have measurement data (bluetooth caliper measurements) ready for 100 of your body and ring parts (as final as possible).
• Students will be graded based on the following criteria:
  • completeness of the required elements
  • clarity of presentation

Press Fit Engineering Analysis

• Present the analysis documented in the manufacturing spreadsheet, preparing slides that highlight each key decision-making step.
  • Instructors and LAs will have the spreadsheet open for reference.
• Explain the full thread of the press-fit features of your yo-yo, connecting the decisions made during the design phase to the results of the manufacturing phase:
  • How well did you deliver on your own specifications?
  • How do your body and ring distributions characterize the success of your manufacture processes?
    • Using engineering reasoning, why are there differences between your specifications and measured parts?
  • What did you learn along the way?
• Students will be graded based on the following criteria:
  • completeness of the spreadsheet parameters up to this point
  • soundness of the engineering reasoning used to make key decisions about press fit parameters
  • consistency between the manufacturing spreadsheet, CAD, and the message conveyed in the presentation

Design for Manufacturing

• How did you work towards delivering high quality components/assemblies?
• Which features ended up being the hardest to manufacture?
  • How does this experience match up to what you thought was going to be hardest?
• Students will be graded based on the following criterion:
  • effectiveness and appropriateness of manufacturing results

Organization and Planning

• Did your team utilize your backup plan protocol? 
  • What was your thinking for managing risk and scaling back your designs?
  • How did your team manage yourselves in terms of getting all the requirements completed?
    • Were there any interesting strategic decisions that had to be made to meet the deliverables?
• What is left to do to meet the final 50 yo-yo’s lab deliverable?
• Students will be graded based on the following criteria:
  • demonstration of engineering reasoning applied to strategic decision making throughout the manufacturing portion of the yo-yo project
  • overall clear messaging, effective presentation, and coherent reasoning presented throughout the manufacturing reviews