OpenSCAD module for simple gears with round teeth

README.md

Simple module that makes gears with circular-shaped teeth. The gears maintain their shape even for extremely low teeth numbers up to 2. Parameters:

• teeth: number of teeth.
• step: width of one teeth (diameter of the circle).

Two gears produced with the same step will transfer movement, so one typically fixes a step for all the gears and varies teeth for each gear, which decides the radius and transfer ratio. Example:

$fn = 50;
color("yellow") translate([3.26,0.15]) rotate(90-$t*360/15) gear(15, 1);
color("red") translate([-2.02,-2.9]) rotate(-15+$t*360/4) gear(4, 1);
color("green") translate([-3.02,-5.65]) rotate(-42-$t*360/5) gear(5, 1);

gear.scad

module gear(teeth, step, height=0.2) {
    angle = 360/(teeth*2);
    radius = (step/2) / sin(angle/2);
    apothem = (step/2) / tan(angle/2);
    
    module circles() {
        for (i = [1:teeth])
            rotate(i * angle * 2) translate([radius,0,0]) circle(step/2);
    }
    
    linear_extrude(height) difference() {
        union() {
            circle(apothem);
            circles();
        }
        rotate(angle) circles();
    }
}

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