Principles &
Practices
Introduction to computer-aided design (CAD) and computer-aided manufacturing (CAM) principles, covering 2D and 3D design fundamentals, digital fabrication workflows, and the tools and techniques that form the foundation of modern making.
I had not yet joined the the class for this week's assignment, so this page focuses on general learnings and principles from computer-aided design from the course website, rather than specific assignment deliverables. The content is based on foundational CAD/CAM concepts and design principles that inform the rest of the course.
01 · Computer-Aided Design Overview
Computer-Aided Design (CAD) and Computer-Aided Manufacturing (CAM) form the foundation of modern digital fabrication. CAD involves creating digital models of physical objects, while CAM translates those models into machine instructions for fabrication.
Design to Fabrication Workflow
The complete workflow from design to finished part involves several stages:
- Design: Create digital model using CAD software
- CAM: Generate toolpaths and machine instructions
- Fabrication: Execute manufacturing process (cutting, milling, 3D printing)
- Testing: Verify fit, function, and quality
- Iteration: Refine design based on results
02 · 2D Design Fundamentals
Raster vs Vector Graphics
Understanding the difference between raster and vector graphics is fundamental to 2D design:
| Type | Definition | Characteristics | Common Tools |
|---|---|---|---|
| Raster | Pixel-based images | Fixed resolution, file size depends on dimensions, loses quality when scaled | GIMP, Photoshop, Krita, ImageMagick |
| Vector | Mathematical paths and shapes | Infinite scalability, smaller file sizes, resolution-independent | Inkscape, Illustrator, CorelDRAW, QCAD |
Raster Graphics
Raster images are composed of a grid of pixels, each with a specific color value. They are ideal for photographs and complex images with gradients, but have limitations for fabrication:
- Resolution-dependent: Quality is determined by pixel density (DPI/PPI)
- Scaling issues: Enlarging causes pixelation and quality loss
- File size: Larger dimensions mean larger file sizes
- Applications: Photo editing, texture mapping, image processing
Vector Graphics
Vector graphics use mathematical descriptions of shapes (paths, curves, polygons) rather than pixels. They are essential for digital fabrication:
- Scalable: Can be resized infinitely without quality loss
- Precise: Exact coordinates and dimensions for fabrication
- Efficient: Small file sizes for simple geometric shapes
- Machine-readable: Direct conversion to cutting paths (SVG, DXF)
- SVG (Scalable Vector Graphics): Web-standard format, excellent for laser cutting and vinyl cutting
- DXF (Drawing Exchange Format): Industry standard for CAD/CAM, widely supported by fabrication machines
- Precision: Vector paths define exact cut lines with mathematical precision
- Parametric: Can be programmatically generated and modified
03 · 3D Design Fundamentals
3D Design Representations
Three-dimensional models can be represented in different ways, each with advantages for specific applications:
| Representation Type | Description | Use Cases |
|---|---|---|
| Boundary Representation (BRep) | Defines surfaces and boundaries of solid objects | CAD modeling, precise engineering parts, assemblies |
| Function Representation (FRep) | Mathematical functions define object geometry | Complex organic shapes, procedural generation |
| Volume Representation (VRep) | Voxel-based or mesh-based volume models | 3D printing, medical imaging, game engines |
Parametric Design
Parametric design uses variables and constraints to create models that can be easily modified. This approach is fundamental to modern CAD:
- Variables: Dimensions, angles, and properties defined as parameters
- Constraints: Relationships between features (parallel, perpendicular, tangent)
- Design history: Feature-based modeling with editability
- Iteration: Easy modification by changing parameter values
3D Design Approaches
Different 3D design approaches suit different needs and workflows:
Sketching & Modeling
- Sketch-based: Start with 2D sketches, extrude/revolve into 3D (Fusion 360, SolidWorks, Onshape)
- Direct modeling: Push/pull geometry directly (SketchUp, Tinkercad)
- Constraint-based: Define relationships between features (FreeCAD, Solvespace)
Sculpting & Organic Modeling
- Digital sculpting: Clay-like manipulation of surfaces (ZBrush, SculptGL)
- Node-based: Procedural geometry generation (Blender Geometry Nodes, Grasshopper)
- Text-to-3D: AI-generated models from text descriptions
Programmatic Design
- Code-based: Generate geometry through programming (OpenSCAD, CadQuery)
- Algorithmic: Rule-based and generative design
- Optimization: AI-driven design optimization and Multidisciplinary Design Optimization (MDO)
04 · CAD Software Categories
Professional CAD Tools
Industry-standard CAD software provides comprehensive modeling, simulation, and CAM capabilities:
| Software | Type | Key Features |
|---|---|---|
| Fusion 360 | Cloud-based CAD/CAM | Parametric modeling, CAM toolpaths, simulation, collaboration |
| SolidWorks | Professional CAD | Assembly modeling, FEA simulation, sheet metal, surfacing |
| Onshape | Cloud-based CAD | Browser-based, real-time collaboration, version control |
| FreeCAD | Open-source CAD | Parametric modeling, workbenches, Python scripting |
| Rhino + Grasshopper | NURBS modeling + visual programming | Complex surfaces, algorithmic design, parametric workflows |
Open-Source Alternatives
Open-source CAD tools provide accessible alternatives for learning and development:
- FreeCAD: Full-featured parametric CAD with workbenches for different tasks
- OpenSCAD: Programmatic CAD using code-based modeling
- Blender: 3D modeling, animation, and rendering with CAD Sketcher addon
- Solvespace: Constraint-based parametric CAD
05 · File Formats & Interchange
Common 3D File Formats
Different file formats serve different purposes in the design-to-fabrication pipeline:
| Format | Type | Use Cases |
|---|---|---|
| STL | Mesh (triangles) | 3D printing, rapid prototyping |
| STEP | BRep (boundary representation) | CAD interchange, precise geometry, assemblies |
| OBJ | Mesh with materials | 3D graphics, rendering, game engines |
| SVG | 2D vector | Laser cutting, vinyl cutting, web graphics |
| DXF | 2D/3D CAD | Laser cutting, CNC routing, CAD interchange |
| glTF | 3D scene | Web 3D, AR/VR, real-time rendering |
- For 3D printing: STL (mesh) or 3MF (with supports)
- For CNC machining: STEP (precise geometry) or STL (mesh approximation)
- For laser cutting: SVG or DXF (vector paths)
- For CAD interchange: STEP (preserves features) or IGES (legacy)
- For web/AR: glTF (efficient, feature-rich)
06 · Design Principles
Parametric Modeling Best Practices
Effective parametric design requires thoughtful organization and constraint management:
- Name parameters clearly: Use descriptive names (e.g., "box_width" not "w1")
- Define relationships: Use constraints to maintain design intent
- Organize features: Group related operations logically
- Document design intent: Add comments explaining design decisions
- Test parameter ranges: Ensure design works across expected variations
Design for Manufacturing (DFM)
Designing with fabrication constraints in mind ensures successful outcomes:
- Material constraints: Understand material properties and limitations
- Machine capabilities: Design within machine work envelopes and tolerances
- Tool access: Ensure all features are accessible by cutting tools
- Support requirements: Consider support material needs for 3D printing
- Assembly considerations: Design for ease of assembly and disassembly
Iterative Design Process
Successful digital fabrication relies on iterative refinement:
- Design: Create initial model with design intent
- Simulate: Use FEA or other simulation tools to validate design
- Prototype: Fabricate test parts to verify fit and function
- Measure: Characterize actual results (kerf, tolerances, etc.)
- Refine: Adjust design based on measurements and feedback
- Repeat: Iterate until design meets requirements
07 · CAM & Toolpath Generation
Computer-Aided Manufacturing
CAM software translates CAD models into machine instructions (G-code) for fabrication:
- Toolpath generation: Calculate cutting paths for material removal
- Tool selection: Choose appropriate cutting tools for material and operation
- Feed rates and speeds: Optimize cutting parameters for quality and efficiency
- Simulation: Preview toolpaths before actual cutting
- Post-processing: Convert toolpaths to machine-specific G-code
CAM Workflows
Different fabrication processes require different CAM approaches:
Subtractive Manufacturing (CNC, Laser Cutting)
- 2D cutting: Vector paths for laser cutting, plasma cutting
- 2.5D milling: Contour and pocket operations for flat parts
- 3D milling: 3-axis, 4-axis, or 5-axis machining for complex surfaces
- Toolpath strategies: Roughing, finishing, contouring, pocketing
Additive Manufacturing (3D Printing)
- Slicing: Convert 3D model into layers for printing
- Support generation: Create support structures for overhangs
- Infill patterns: Optimize material usage and strength
- Layer optimization: Balance print time, quality, and material usage
08 · Design Tools & Workflows
2D Design Tools
Essential tools for 2D design and vector graphics:
| Tool | Type | Best For |
|---|---|---|
| Inkscape | Vector graphics | SVG creation, laser cutting prep, logo design |
| Illustrator | Professional vector | Complex graphics, print design, professional workflows |
| GIMP | Raster editing | Photo editing, image processing, texture creation |
| ImageMagick | Command-line raster | Batch processing, automation, format conversion |
3D Design Tools
Comprehensive 3D modeling and CAD software:
| Tool | Category | Strengths |
|---|---|---|
| Fusion 360 | CAD/CAM | Integrated design and manufacturing, cloud collaboration |
| FreeCAD | Open-source CAD | Parametric modeling, Python scripting, modular workbenches |
| Blender | 3D modeling | Organic modeling, animation, rendering, CAD Sketcher addon |
| OpenSCAD | Programmatic CAD | Code-based modeling, parametric design, algorithmic generation |
| Rhino + Grasshopper | NURBS + Visual Programming | Complex surfaces, algorithmic design, parametric workflows |
09 · Key Learnings
- Raster vs Vector: Understanding when to use each format is crucial for fabrication workflows
- Parametric Design: Variables and constraints enable flexible, iterative design
- Design Intent: Models should capture not just geometry, but design reasoning
- File Formats: Choosing the right format for each stage of the workflow
- Design for Manufacturing: Consider fabrication constraints from the start
- Start with sketches and design intent before detailed modeling
- Use parametric design to enable easy iteration and variation
- Test designs through simulation and prototyping before final fabrication
- Document design decisions and parameter choices for future reference
- Maintain clean, organized model structure for collaboration and iteration
10 · Conclusion
Computer-aided design forms the foundation of modern digital fabrication. Understanding the principles of 2D and 3D design, parametric modeling, file formats, and design-for-manufacturing enables effective creation of digital models that can be successfully translated into physical objects.
The tools and techniques covered in this introduction provide the groundwork for all subsequent assignments in the course. Mastery of CAD fundamentals—from vector graphics for 2D cutting to parametric 3D modeling for complex assemblies—is essential for successful digital fabrication projects.
As the course progresses, these principles will be applied to specific fabrication processes: laser cutting, 3D printing, CNC machining, and more. Each process has its own requirements and constraints, but all begin with thoughtful digital design.