Bug Report/Help Wanted with involute_gears

[Marcio Teixeira]

Hello, I am trying to construct a simple gear using "MCAD/involute_gears.scad" and I have run into numerous problems with misshapen teeth or non-manifold surfaces.

It seems like each time I find a workaround, something else crops up and I am back to square one.

I am posting code that reproduces the problem in the hopes that it can serve either as a bug report, or someone can point out what I am doing wrong.

I've already spent several hours trying to get around this and I'm out of options. Any help would be very much appreciated!

Thank you,

-- Marcio

/* This bug report pertains to the "MCAD/involute_gears.scad" included

 * in version 2015.03-1 of OpenSCAD

 */

use <MCAD/involute_gears.scad>;

$fn = 40;

teeth          = 9;

backlash       = 0.7;

circular_pitch = 143;

bore_diameter  = 1.5;

module non_manifold_and_mishapen() {

    // My first attempt at a gear of the correct size for

    // my project gave me this. The surface is non-manifold,

    // and the tips of the teeth are mishapen (when backlash

    // != 0 and for this particular combination of teeth and

    // circular pitch.)

    gear (

        number_of_teeth = teeth,

        circular_pitch  = circular_pitch,

        backlash        = backlash,

        bore_diameter   = bore_diameter,

        hub_thickness   = 1,

        gear_thickness  = 1,

        rim_thickness   = 1,

        flat            = false

    );

}

module mishapen_gear() {

    // It seems possible to work around the non-manifoldness

    // by making the gear flat and extruding it, but this won't

    // fix the teeth

    gear (

        number_of_teeth = teeth,

        circular_pitch  = circular_pitch,

        backlash        = backlash,

        bore_diameter   = bore_diameter,

        flat            = true

    );

}

module mishapen_gear_hack() {

    // Here is a hack, showing the results I expect.

    intersection() {

        mishapen_gear();

        circle(d=8.51);

    }

}

module non_manifold_combo() {

    // However, combining this into more complex assemblies

    // invariably makes it non-manifold again.

    difference() {

        union() {

            linear_extrude(1)

                mishapen_gear_hack();

            translate([0, 0, 0.1])

                mirror([0,0,1]) {

                    cylinder( d = 10, h = 1 );

                    cylinder( d = 3,  h = 5 );

                }

        }

        cylinder( d = 2, h = 15,center=true);

    }

}

translate([-10,0,0])                    non_manifold_and_mishapen();

translate([  0,0,0])  linear_extrude(1) mishapen_gear();

translate([ 10,0,0])  linear_extrude(1) mishapen_gear_hack();

translate([ 20,0,0])                    non_manifold_combo();