Design Evolution

Chapter 2: From Napkin Sketch to CAD Model

Initial Concepts

Every design starts somewhere. For the JMC cap, it began with a simple question: “What if the AeroPress filter cap had adjustable flow?”

The Napkin Stage

The first sketches explored several concepts:

Multi-hole patterns - Various arrangements of small perforations
Spiral channels - Creating turbulence for better extraction
Variable aperture - Adjustable flow like a camera iris
Modular inserts - Swappable flow plates

Design Constraints

Before moving to CAD, we established key constraints:

Physical Requirements

Must fit AeroPress XL dimensions precisely
Maintain seal integrity during brewing
Support standard paper filters
Withstand brewing temperatures (80-100°C)

Manufacturing Constraints

Printable on consumer FDM printers
No support material in critical areas
Reasonable print times (<2 hours)
Post-processing minimal

User Experience

Easy to clean
Intuitive to use
Durable for daily use
Safe for food contact

CAD Development

Version 1: Basic Proof of Concept

- Simple cylinder with holes
- Fixed gasket groove
- 0.8mm hole diameter
- Result: Leaked badly, poor flow

Version 2: Improved Sealing

- Deeper gasket channel
- Tapered edges
- Multiple hole sizes tested
- Result: Better seal, uneven extraction

Version 3: Flow Optimization

- Hexagonal hole pattern
- Gradual thickness transitions
- Integrated drip fins
- Result: Good flow, difficult to clean

Version 4: Current Design (NoDrip XL)

- Flow-restriction outlet design
- Standard paper-filter cradle
- Locking tab overhang
- TPE disc gasket compatibility
- Result: Prismo-style pressure without metal screen

The NoDrip XL prototype showing the snowflake-pattern flow restrictor

Design Tools and Workflow

Software Stack

CAD: Fusion 360 / OpenSCAD
Slicing: PrusaSlicer
Analysis: Flow simulation basics

Parametric Design

Key parameters made adjustable: - Hole diameter and count - Wall thickness - Gasket groove dimensions - Overall height

Lessons Learned

Iterate quickly - First prints revealed issues immediately
Test with water first - Save coffee for proven designs
Document everything - Failed designs teach valuable lessons
Community feedback - Other users spot issues you miss

Design Files

All CAD files are available in the repository: - OpenSCAD source for customization - STL files for direct printing - Technical drawings with dimensions

Next: Material Selection

With the design refined, the next chapter explores choosing the right plastics for safe, effective brewing.

--- title: "Design Evolution" --- # Chapter 2: From Napkin Sketch to CAD Model ## Initial Concepts Every design starts somewhere. For the JMC cap, it began with a simple question: "What if the AeroPress filter cap had adjustable flow?" ### The Napkin Stage The first sketches explored several concepts: 1. **Multi-hole patterns** - Various arrangements of small perforations 2. **Spiral channels** - Creating turbulence for better extraction 3. **Variable aperture** - Adjustable flow like a camera iris 4. **Modular inserts** - Swappable flow plates ## Design Constraints Before moving to CAD, we established key constraints: ### Physical Requirements - Must fit AeroPress XL dimensions precisely - Maintain seal integrity during brewing - Support standard paper filters - Withstand brewing temperatures (80-100°C) ### Manufacturing Constraints - Printable on consumer FDM printers - No support material in critical areas - Reasonable print times (<2 hours) - Post-processing minimal ### User Experience - Easy to clean - Intuitive to use - Durable for daily use - Safe for food contact ## CAD Development ### Version 1: Basic Proof of Concept ``` - Simple cylinder with holes - Fixed gasket groove - 0.8mm hole diameter - Result: Leaked badly, poor flow ``` ### Version 2: Improved Sealing ``` - Deeper gasket channel - Tapered edges - Multiple hole sizes tested - Result: Better seal, uneven extraction ``` ### Version 3: Flow Optimization ``` - Hexagonal hole pattern - Gradual thickness transitions - Integrated drip fins - Result: Good flow, difficult to clean ``` ### Version 4: Current Design (NoDrip XL) ``` - Flow-restriction outlet design - Standard paper-filter cradle - Locking tab overhang - TPE disc gasket compatibility - Result: Prismo-style pressure without metal screen ``` ![The NoDrip XL prototype showing the snowflake-pattern flow restrictor](images/DA0CD7AB-DA38-4A42-95C6-E8DEFD296CD8_4_5005_c.jpeg) ## Design Tools and Workflow ### Software Stack - **CAD**: Fusion 360 / OpenSCAD - **Slicing**: PrusaSlicer - **Analysis**: Flow simulation basics ### Parametric Design Key parameters made adjustable: - Hole diameter and count - Wall thickness - Gasket groove dimensions - Overall height ## Lessons Learned 1. **Iterate quickly** - First prints revealed issues immediately 2. **Test with water first** - Save coffee for proven designs 3. **Document everything** - Failed designs teach valuable lessons 4. **Community feedback** - Other users spot issues you miss ## Design Files All CAD files are available in the repository: - OpenSCAD source for customization - STL files for direct printing - Technical drawings with dimensions ## Next: Material Selection With the design refined, the next chapter explores choosing the right plastics for safe, effective brewing.