cad-verifier - SKILL.md Agent Skill

name: cad-verifier description: "Product Engineering Agent — mathematical specs, verified CAD, assembly verification, BOM with vendor pricing" triggers: - gear - differential - verify CAD - tooth count - bevel gear - spur gear - generate gear - mechanical assembly - assembly fit - tolerance - bill of materials - BOM - vendor pricing - math spec

Product Engineering Agent — Skill Reference

Mathematical verification system for AI-generated CAD geometry, assembly fit checking, and Bill of Materials generation with vendor pricing.

The Problem

AI-generated gears with zero teeth were passing visual inspection — they looked like smooth cylinders but had no actual gear teeth. This plugin provides mathematical verification to catch these issues and extends into full product-engineering workflows.

When to Use

Use this skill when:

Generating gears (spur, bevel, helical)
Creating differentials or gearboxes
Verifying CAD models before manufacturing
Calculating gear ratios and dimensions
Checking assembly fit (shaft/hole tolerances)
Generating a priced Bill of Materials
Producing mathematical specification sheets

Available Tools

cad_generate_spur_gear

Generate a verified spur gear with mathematical tooth counting.

Parameters:

module: Gear module (tooth size in mm)
num_teeth: Number of teeth
face_width: Width of gear face in mm

cad_generate_bevel_gear

Generate a verified bevel gear for angular power transmission.

Parameters:

module: Gear module
num_teeth: Number of teeth
face_width: Face width in mm
cone_angle: Pitch cone angle (default: 45°)

cad_generate_differential

Generate a complete differential assembly with verified gears.

Parameters:

module: Gear module for all gears
ring_gear_teeth: Ring gear tooth count
pinion_teeth: Pinion tooth count
spider_teeth: Spider gear count (default: 10)
side_gear_teeth: Side gear count (default: 16)

cad_calculate_gear_ratio

Calculate gear ratio and dimensions from tooth counts.

Parameters:

driver_teeth: Number of teeth on the driver gear
driven_teeth: Number of teeth on the driven gear
module: Gear module (default: 2.0)

cad_math_spec (v2)

Generate a full mathematical specification sheet for a gear.

Parameters:

module: Gear module (mm)
num_teeth: Number of teeth
face_width: Face width (mm)
pressure_angle: Pressure angle in degrees (default: 20°)

Returns pitch diameter, outer diameter, root diameter, base circle diameter, addendum, dedendum, clearance, circular pitch, tooth thickness, and face-width/module ratio.

cad_verify_assembly (v2)

Verify shaft/hole assembly fit against standard tolerance grades.

Parameters:

shaft_diameter: Shaft outer diameter in mm
hole_diameter: Hole inner diameter in mm
fit_type: press, transition, or clearance (default: clearance)

cad_generate_bom (v2)

Generate a Bill of Materials with vendor pricing.

Parameters:

items: Array of objects, each with:
- part: Part name
- material: Material key (e.g. steel_round_bar, bearing_608zz)
- quantity: Quantity (default: 1)
- weight_kg: Weight in kg (default: 1.0)

Supported materials: steel_round_bar, aluminum_6061, brass_360, nylon_6, bearing_608zz, bearing_6001, m3_socket_cap, m5_socket_cap, dowel_pin_3mm, retaining_ring_8mm.

Gear Formulas

Pitch Diameter    = module × num_teeth
Outer Diameter    = module × (num_teeth + 2)
Root Diameter     = module × (num_teeth - 2.5)
Base Circle Dia.  = pitch_diameter × cos(pressure_angle)
Addendum          = module
Dedendum          = 1.25 × module
Circular Pitch    = π × module
Tooth Thickness   = circular_pitch / 2
Gear Ratio        = driven_teeth / driver_teeth
Center Distance   = module × (teeth1 + teeth2) / 2

Verification Checks

Toothless Detection: Rejects gears with zero teeth
Undercut Warning: Flags gears with <17 teeth
Module Validation: Warns on non-standard modules (ISO 54)
Face Width Ratio: Checks width/module ratio (ideal: 8-12)
Assembly Fit (v2): Validates press / transition / clearance tolerances
BOM Pricing (v2): Cross-references vendor catalog for line totals