cad

What I do

• Create 2D drawings and 3D models of mechanical parts
• Generate technical documentation and manufacturing files
• Perform geometric constraint solving and parametric modeling
• Support assembly design and component routing
• Export designs for manufacturing or simulation

When to use me

• When creating mechanical designs for manufacturing
• When generating detailed engineering drawings
• When building 3D models for visualization or simulation
• When designing assemblies with multiple components
• When preparing files for CNC machining or 3D printing

Key Concepts

CAD File Formats

Format	Type	Applications
STEP	3D neutral	Exchange, CAD interoperability
IGES	3D neutral	Legacy CAD exchange
STL	3D mesh	3D printing, rapid prototyping
DXF	2D	Drawing exchange
DWG	2D	AutoCAD native format
OBJ	3D mesh	Visualization, 3D graphics
Parasolid	3D	Siemens NX, SolidWorks

Parametric Modeling

# Example: Creating a parameterized part
class ParametricPart:
    def __init__(self, **dimensions):
        self.dimensions = dimensions
    
    def create_sketch(self, points):
        """Create 2D profile from points"""
        return {
            "type": "sketch",
            "entities": points,
            "constraints": []
        }
    
    def extrude(self, sketch, depth):
        """Extrude sketch to create 3D feature"""
        return {
            "type": "extrude",
            "profile": sketch,
            "depth": depth,
            "direction": "positive"
        }
    
    def create_hole(self, location, diameter, depth):
        """Create a hole feature"""
        return {
            "type": "hole",
            "center": location,
            "diameter": diameter,
            "depth": depth
        }

Geometric Constraints

• Coincident: Two points occupy same location
• Collinear: Points lie on same line
• Parallel: Lines have same direction
• Perpendicular: Lines intersect at 90°
• Concentric: Centers coincide
• Equal: Dimensions or radii match
• Tangent: Curves touch without crossing

Assembly Design

# Assembly constraint types
ASSEMBLY_CONSTRAINTS = {
    "mate": {
        "description": "Two faces in contact, opposite directions",
        "degrees_removed": 3
    },
    "flush": {
        "description": "Two faces coplanar",
        "degrees_removed": 2
    },
    "angle": {
        "description": "Constrained angular relationship",
        "degrees_removed": 2
    },
    "insert": {
        "description": "Axial insertion (e.g., pin in hole)",
        "degrees_removed": 2
    }
}

Common CAD Software

Software	Vendor	Strengths
SolidWorks	Dassault Systèmes	Mechanical, assemblies
CATIA	Dassault Systèmes	Complex surfaces, aerospace
NX	Siemens	Advanced manufacturing
Inventor	Autodesk	Mechanical, simulation
Fusion 360	Autodesk	Cloud, accessible
Onshape	PTC	Web-based, collaboration
FreeCAD	Open source	Free, parametric