openscad 2d involute gear

involute_gear_2d.scad

module gear_shape_2d (
	number_of_teeth = 15,
	circular_pitch = false, diametral_pitch = false,
	pressure_angle = 28,
	clearance = 0.2,
	circles=0,
	backlash=0,
	involute_facets=0)
{
	if (circular_pitch==false && diametral_pitch==false)
		echo("MCAD ERROR: gear module needs either a diametral_pitch or circular_pitch");

	//Convert diametrial pitch to our native circular pitch
	circular_pitch = (circular_pitch!=false?circular_pitch:180/diametral_pitch);

	// Pitch diameter: Diameter of pitch circle.
	pitch_diameter  =  number_of_teeth * circular_pitch / PI;
	pitch_radius = pitch_diameter/2;
	echo ("Teeth:", number_of_teeth, " Pitch radius:", pitch_radius);

	// Base Circle
	base_radius = pitch_radius*cos(pressure_angle);

	// Diametrial pitch: Number of teeth per unit length.
	pitch_diametrial = number_of_teeth / pitch_diameter;

	// Addendum: Radial distance from pitch circle to outside circle.
	addendum = 1/pitch_diametrial;

	//Outer Circle
	outer_radius = pitch_radius + addendum;

	// Dedendum: Radial distance from pitch circle to root diameter
	dedendum = addendum + clearance;

	// Root diameter: Diameter of bottom of tooth spaces.
	root_radius = pitch_radius-dedendum;
	backlash_angle = backlash / pitch_radius * 180 / pi;
	half_thick_angle = (360 / number_of_teeth - backlash_angle) / 4;

	gear_shape (
		number_of_teeth,
		pitch_radius = pitch_radius,
		root_radius = root_radius,
		base_radius = base_radius,
		outer_radius = outer_radius,
		half_thick_angle = half_thick_angle,
		involute_facets=involute_facets);
}