cad-modeling

name	cad-modeling
description	Expert skill for parametric 3D CAD model development with design intent and configuration management
allowed-tools	["Read","Write","Glob","Grep","Bash"]
metadata	{"specialization":"mechanical-engineering","domain":"science","category":"design-development","priority":"high","phase":1,"tools-libraries":["SolidWorks","CATIA","Siemens NX","PTC Creo","Autodesk Inventor"]}
graph	{"domains":["domain:mechanical-engineering"],"skillAreas":["skill-area:physics-simulation","skill-area:mathematical-reasoning","skill-area:motion-planning"],"roles":["role:systems-integration-engineer","role:research-engineer"]}

3D CAD Modeling Skill

Purpose

The 3D CAD Modeling skill provides expert capabilities for parametric 3D CAD model development with proper design intent, configuration management, and best practices for model quality and reusability.

Capabilities

• SolidWorks, CATIA, NX, Creo workflow automation
• Parametric feature-based modeling best practices
• Assembly design and constraint management
• Design table and configuration creation
• Top-down and bottom-up assembly strategies
• Part family and library component creation
• Model validation and quality checking
• CAD data exchange and translation

Usage Guidelines

Part Modeling

Design Intent Capture

1. Sketch Best Practices

   • Fully constrain all sketches
   • Use construction geometry
   • Apply meaningful dimensions
   • Reference design features, not edges

2. Feature Planning

   Order of features:
   1. Primary form (base feature)
   2. Secondary forms
   3. Positioned features
   4. Detail features (rounds, chamfers)
   5. Reference geometry
   

3. Parametric Relationships

   • Link related dimensions
   • Use equations for complex relationships
   • Create global variables for key parameters
   • Document design equations

Feature Best Practices

Feature Type	Best Practice
Extrude	Use mid-plane when symmetric
Revolve	Full 360 or symmetric angle
Sweep	Keep profile perpendicular to path
Loft	Match profile vertex count
Fillet	Apply late in feature tree
Pattern	Use linear/circular for regular arrays

Model Quality

1. Geometry Checks

   • No self-intersecting geometry
   • Minimum wall thickness maintained
   • Draft analysis for molded parts
   • Undercut detection

2. File Management

   • Meaningful part names
   • Custom properties populated
   • Revision history maintained
   • Linked reference files documented

Assembly Modeling

Assembly Strategies

1. Bottom-Up Assembly

   • Components modeled independently
   • Assembled using mates/constraints
   • Best for: Standard components, reusable parts

2. Top-Down Assembly

   • Layout sketch defines relationships
   • Parts reference assembly geometry
   • Best for: Highly integrated systems

3. Hybrid Approach

   • Combine strategies as appropriate
   • Use skeleton/layout for key interfaces
   • Independent modeling for standard parts

Mate/Constraint Best Practices

1. Constraint Types

   Type	Use Case
   Coincident	Face-to-face contact
   Concentric	Shaft/hole alignment
   Distance	Offset positioning
   Angle	Angular relationship
   Tangent	Curved surface contact

2. Degree of Freedom

   • Fully constrain or document remaining DOF
   • Use limit mates for motion range
   • Consider mechanism simulation needs

Large Assembly Management

1. Performance Optimization

   • Use lightweight/simplified representations
   • Create configurations for assembly states
   • Suppress unused components
   • Use envelope geometry for space claims

2. Reference Management

   • Minimize external references
   • Document all in-context relationships
   • Use published geometry when possible

Configuration Management

1. Part Configurations

   • Variations: Sizes, materials, features
   • Design table for multiple configurations
   • Display states for visualization

2. Assembly Configurations

   • Bill of materials variations
   • Exploded views
   • Suppressed component states

Process Integration

• ME-003: 3D CAD Model Development

Input Schema

{
  "part_type": "component|assembly|drawing",
  "design_requirements": {
    "function": "string",
    "envelope": {
      "length": "number (mm)",
      "width": "number (mm)",
      "height": "number (mm)"
    },
    "interfaces": "array of interface definitions",
    "material": "string"
  },
  "reference_geometry": "file path or description",
  "configurations_needed": "array of configuration names",
  "manufacturing_method": "machined|cast|molded|sheet_metal|additive"
}

Output Schema

{
  "model_info": {
    "file_path": "string",
    "file_format": "native|STEP|IGES",
    "revision": "string"
  },
  "geometry_summary": {
    "bounding_box": "object",
    "volume": "number (mm3)",
    "surface_area": "number (mm2)",
    "mass": "number (kg)"
  },
  "quality_check": {
    "fully_constrained": "boolean",
    "no_errors": "boolean",
    "rebuild_time": "number (s)"
  },
  "configurations": "array of config names",
  "custom_properties": "object"
}

Best Practices

1. Plan feature order before modeling
2. Use symmetric features when design is symmetric
3. Avoid external references when possible
4. Create reusable part templates
5. Document design intent in model notes
6. Validate geometry before release

Integration Points

• Connects with Requirements Flowdown for design inputs
• Feeds into GD&T Drawing for documentation
• Supports FEA Structural for analysis
• Integrates with DFM Review for manufacturability