SCAD Library MCAD Skill

Use MCAD when the runtime prompt lists MCAD and the requested part needs established mechanical primitives, especially gears.

Imports

Use the narrowest MCAD file needed:

use <MCAD/involute_gears.scad>

Use include <MCAD/units.scad> only when constants from the file are required. Prefer use for module-only imports because it avoids top-level demonstration geometry.

Best Uses

• Use gear() from MCAD/involute_gears.scad for spur gears when exact involute tooth geometry matters.
• Use bevel_gear() or bevel_gear_pair() for bevel gears when the request explicitly asks for them.
• Use MCAD motor/servo helpers only when exact module names and signatures are known.
• Use MCAD regular shapes when they simplify geometry without reducing editability.

Generation Pattern

Expose gear controls as top-level parameters and call MCAD inside a wrapper module:

use <MCAD/involute_gears.scad>

/* [Gear] */
teeth = 24;            // min: 8 max: 160 step: 1
circular_pitch = 220;  // min: 80 max: 600 step: 5
pressure_angle = 20;   // min: 14.5 max: 25 step: 0.5
gear_thickness = 8;    // min: 2 max: 40 step: 0.5
bore_diameter = 5;     // min: 1 max: 40 step: 0.5

module printable_gear() {
  gear(
    number_of_teeth=teeth,
    circular_pitch=circular_pitch,
    pressure_angle=pressure_angle,
    bore_diameter=bore_diameter,
    gear_thickness=gear_thickness,
    rim_thickness=gear_thickness,
    hub_thickness=gear_thickness,
    flat=true
  );
}

printable_gear();

Quality Rules

• For gears, expose teeth count, pitch, pressure angle, bore diameter, and thickness.
• Keep pressure angle default at 20 degrees unless specified.
• Add bore and hub features intentionally; do not leave a solid gear when an axle hole is likely needed.
• Prefer MCAD gear modules over hand-drawn rectangular tooth approximations.

Avoid

• Do not use broad include statements when use is sufficient.
• Do not invent MCAD module names.
• Do not copy MCAD source into generated SCAD.