Engineering Design Process
Learning Objectives
Students will be able to:
- Identify and describe the stages of the engineering design process
- Define criteria and constraints for their CR box design
- Apply the engineering design process to plan their air purifier
- Explain why engineering design is iterative (not linear)
Scientist vs. Engineer
What's the difference?
Scientist
"How does nature work?"
Discovers knowledge
Engineer
"How can we solve this problem?"
Creates solutions
Both use evidence and reasoning, but they have different goals. In this unit, you become engineers.
The Engineering Design Process
Unlike a linear process, engineering design is iterative—you cycle through steps multiple times to improve your solution.
What need are we addressing?
What solutions exist?
What are the requirements?
Generate multiple ideas
Choose best approach
Create working model
Collect data
Improve based on results
Share the solution
Criteria vs. Constraints
| Criteria (Goals) | Constraints (Limitations) |
|---|---|
| What the solution MUST DO | What LIMITS the solution |
| Performance requirements | Resource limitations |
| Example: "Remove 80% of PM2.5" | Example: "Budget under $100" |
Our Design Criteria & Constraints
Criteria (Must Achieve)
- CADR of at least 400 CFM
- Uses MERV-13 (or higher) filters
- Safe to operate
- Stable and won't tip
- Measurable performance
Constraints (Limitations)
- Budget: $100 or less
- Materials must be available
- Build time: 2 class periods
- Must fit in classroom
- Standard filter sizes only
Case Study: The Invention of the CR Box
In 2020, during the COVID-19 pandemic, people needed affordable ways to clean indoor air. Commercial HEPA purifiers cost $300-800 and were hard to find.
Dr. Richard Corsi, an air quality expert, and Jim Rosenthal, a filter manufacturer, asked: "Can we build something effective using common materials?"
They experimented with box fans and furnace filters. A single filter restricted airflow too much. But arranging filters in a cube? That worked!
They shared their design freely. People around the world built thousands of CR boxes. Scientists tested them and found they performed as well as commercial units costing 5-10x more.
Key Vocabulary
| Term | Definition |
|---|---|
| Engineering design process | A systematic approach to solving problems through iteration |
| Criteria | Requirements a solution must meet; goals to achieve |
| Constraints | Limitations on what's possible; boundaries to work within |
| Iterative | Repeating steps to improve; trying, testing, and improving again |
| Prototype | A working model to test a design |
| Trade-off | Giving up one thing to gain another |