NopSCADlib/vitamins/screw.scad

//
// NopSCADlib Copyright Chris Palmer 2018
// nop.head@gmail.com
// hydraraptor.blogspot.com
//
// This file is part of NopSCADlib.
//
// NopSCADlib is free software: you can redistribute it and/or modify it under the terms of the
// GNU General Public License as published by the Free Software Foundation, either version 3 of
// the License, or (at your option) any later version.
//
// NopSCADlib is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
// without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along with NopSCADlib.
// If not, see <https://www.gnu.org/licenses/>.
//

//
//! Machine screws and wood screws with various head styles.
//!
//! For an explanation of `screw_polysink()` see <https://hydraraptor.blogspot.com/2020/12/sinkholes.html>.
//
include <../utils/core/core.scad>

use <washer.scad>
use <nut.scad>
use <../utils/rounded_cylinder.scad>
use <../utils/thread.scad>
include <inserts.scad>

function screw_head_type(type)        = type[2];     //! Head style hs_cap, hs_pan, hs_cs, hs_hex, hs_grub, hs_cs_cap, hs_dome
function screw_radius(type)           = type[3] / 2; //! Nominal radius
function screw_head_radius(type)      = type[4] / 2; //! Head radius
function screw_head_height(type)      = type[5];     //! Head height
function screw_socket_depth(type)     = type[6];     //! Socket or slot depth
function screw_socket_af(type)        = type[7];     //! Socket across flats
function screw_max_thread(type)       = type[8];     //! Maximum thread length
function screw_washer(type)           = type[9];     //! Default washer
function screw_nut(type)              = type[10];    //! Default nut
function screw_pilot_hole(type)       = type[11];    //! Pilot hole radius for wood screws, tap radius for machine screws
function screw_clearance_radius(type) = type[12];    //! Clearance hole radius
function screw_nut_radius(type) = screw_nut(type) ? nut_radius(screw_nut(type)) : 0; //! Radius of matching nut
function screw_boss_diameter(type) = max(washer_diameter(screw_washer(type)) + 1, 2 * (screw_nut_radius(type) + 3 * extrusion_width)); //! Boss big enough for nut trap and washer
function screw_head_depth(type, d = 0) =             //! How far a counter sink head will go into a straight hole diameter d
    screw_head_height(type)
        ? 0
        : let(r = screw_radius(type)) screw_head_radius(type) - max(r, d / 2) + r / 5;

function screw_longer_than(x) = x <=  5 ?  5 : //! Returns shortest screw length longer or equal to x
                                x <=  6 ?  6 :
                                x <=  8 ?  8 :
                                x <= 10 ? 10 :
                                x <= 12 ? 12 :
                                x <= 16 ? 16 :
                                ceil(x / 5) * 5;

function screw_shorter_than(x) = x >= 20 ? floor(x / 5) * 5 : //! Returns longest screw length shorter than or equal to x
                                 x >= 16 ? 16 :
                                 x >= 12 ? 12 :
                                 x >= 10 ? 10 :
                                 x >=  8 ?  8 :
                                 x >=  6 ?  6 :
                                 5;

function screw_smaller_than(d) = d >= 2.5 && d < 3 ? 2.5 : floor(d); // Largest diameter screw less than or equal to specified diameter

function screw_insert(screw, i = 0) = let(d = screw_radius(screw) * 2)
     i >= len(inserts) ? undef
                       : insert_screw_diameter(inserts[i]) == d ? inserts[i]
                                                                : screw_insert(screw, i + 1);

module screw(type, length, hob_point = 0, nylon = false) { //! Draw specified screw, optionally hobbed or nylon
    description = str("Screw ", nylon ? "Nylon " : "", type[1], length < 10 ? " x  " : " x ", length, "mm", hob_point ? str(", hobbed at ", hob_point) : "");
    vitamin(str("screw(", type[0], "_screw, ", length, arg(hob_point, 0, "hob_point"), arg(nylon, false, "nylon"), "): ", description));

    head_type   = screw_head_type(type);
    rad         = screw_radius(type) - eps;
    head_rad    = screw_head_radius(type);
    head_height = screw_head_height(type);
    socket_af   = screw_socket_af(type);
    socket_depth= screw_socket_depth(type);
    socket_rad  = socket_af / cos(30) / 2;
    max_thread  = screw_max_thread(type);
    thread = max_thread ? length >= max_thread + 5 ? max_thread
                                                   : length
                        : length;
    d = 2 * screw_radius(type);
    pitch = metric_coarse_pitch(d);
    colour = nylon || head_type == hs_grub ? grey(40) : grey(80);

    module shaft(socket = 0, headless = false) {
        point = screw_nut(type) ? 0 : 3 * rad;
        shank  = length - thread - socket;

        if(show_threads && !point && pitch)
            translate_z(-length)
                male_metric_thread(d, pitch, thread - (shank > 0 || headless ? 0 : socket), false, top = headless ? -1 : 0, solid = !headless, colour = colour);
        else
            color(colour * 0.9)
                rotate_extrude() {
                    translate([0, -length + point])
                        square([rad, length - socket - point]);

                    if(point)
                        polygon([
                            [0.4, -length], [0, point - length], [rad, point - length]
                        ]);
                }

        if(shank > 0)
            color(colour)
                translate_z(-shank - socket)
                    cylinder(r = rad + eps, h = shank);
    }

    module cs_head(socket_rad, socket_depth) {
        head_t = rad / 5;
        head_height = head_rad + head_t;

        rotate_extrude()
            difference() {
                polygon([[0, 0], [head_rad, 0], [head_rad, -head_t], [0, -head_height]]);

                translate([0, -socket_depth + eps])
                    square([socket_rad, 10]);
            }

        translate_z(-socket_depth)
            linear_extrude(socket_depth)
                difference() {
                    circle(socket_rad + 0.1);

                    children();
                }
    }

    explode(length + 10) {
        if(head_type == hs_cap) {
            color(colour) {
                cylinder(r = head_rad, h = head_height - socket_depth);

                translate_z(head_height - socket_depth)
                    linear_extrude(socket_depth)
                        difference() {
                            circle(head_rad);

                            circle(socket_rad, $fn = 6);
                        }

            }
            shaft();
        }
        if(head_type == hs_grub) {
            color(colour) {
                r = show_threads ? rad - pitch / 2 : rad;
                translate_z(-socket_depth)
                    linear_extrude(socket_depth)
                        difference() {
                            circle(r);

                            circle(socket_rad, $fn = 6);
                        }

                shaft(socket_depth, true);

                if(show_threads)
                    translate_z(-length)
                        cylinder(r = r, h = length - socket_depth);
            }
        }
        if(head_type == hs_hex) {
            color(colour)
                cylinder(r = head_rad, h = head_height, $fn = 6);

            shaft();
        }
        if(head_type == hs_pan) {
            socket_rad = 0.6 * head_rad;
            socket_depth = 0.5 * head_height;
            socket_width = 1;
            color(colour) {
                rotate_extrude()
                    difference() {
                        rounded_corner(r = head_rad, h = head_height, r2 = head_height / 2);

                        translate([0, head_height - socket_depth])
                            square([socket_rad, 10]);
                    }

                linear_extrude(head_height)
                    difference() {
                        circle(socket_rad + eps);

                        square([2 * socket_rad, socket_width], center = true);
                        square([socket_width, 2 * socket_rad], center = true);
                    }
            }
            shaft();
        }

        if(head_type == hs_dome) {
            lift = 0.38;
            h = head_height - lift;
            r = min(2 * head_height, (sqr(head_rad) + sqr(h)) / 2 * h); // Special case for M2
            y = sqrt(sqr(r) - sqr(head_rad));
            color(colour) {
                rotate_extrude() {
                    difference() {
                        intersection() {
                            translate([0, -y + lift])
                                circle(r);

                            square([head_rad, head_height]);
                        }
                        translate([0, head_height - socket_depth])
                            square([socket_rad, 10]);
                    }
                }
                linear_extrude(head_height)
                    difference() {
                        circle(socket_rad + eps);
                        circle(socket_rad, $fn = 6);
                    }
            }
            shaft();
        }

        if(head_type == hs_cs) {
            socket_rad = 0.6 * head_rad;
            socket_depth = 0.3 * head_rad;
            socket_width = 1;
            color(colour)
                cs_head(socket_rad, socket_depth) {
                    square([2 * socket_rad, socket_width], center = true);
                    square([socket_width, 2 * socket_rad], center = true);
                }

            shaft(socket_depth);
        }

        if(head_type == hs_cs_cap) {
            color(colour)
                cs_head(socket_rad, socket_depth)
                    circle(socket_rad, $fn = 6);

            shaft(socket_depth);
        }
    }
}

module screw_countersink(type, drilled = true) { //! Countersink shape
    head_type   = screw_head_type(type);
    head_rad    = screw_head_radius(type);
    rad = screw_radius(type);
    head_t = rad / 5;
    head_height = head_rad + head_t;

    if(head_type == hs_cs || head_type == hs_cs_cap)
        translate_z(-head_height)
            if(drilled)
                cylinder(h = head_height + eps, r1 = 0, r2 = head_rad + head_t);
            else
                render() intersection() {
                    cylinder(h = head_height + eps, r1 = 0, r2 = head_rad + head_t);

                    cylinder(h = head_height + eps, r = head_rad + eps);
                }
}

function screw_polysink_r(type, z) = //! Countersink hole profile corrected for rounded staircase extrusions.
    let(rad = screw_radius(type),
        head_t = rad / 5,
        head_rad = screw_head_radius(type)
    )
    limit(head_rad + head_t - z + (sqrt(2) - 1) * layer_height / 2, screw_clearance_radius(type), head_rad);

module screw_polysink(type, h = 100, alt = false) { //! A countersink hole made from stacked polyholes for printed parts
    head_depth = screw_head_depth(type);
    assert(head_depth, "Not a countersunk screw");
    layers = ceil(head_depth / layer_height);
    rmin = screw_clearance_radius(type);
    sides = sides(rmin);
    lh = layer_height + eps;
    render(convexity = 5)
        for(side = [0, 1]) mirror([0, 0, side]) {
            for(i = [0 : layers - 1])
                translate_z(i * layer_height) {
                    r = screw_polysink_r(type, i * layer_height + layer_height / 2);
                    if(alt)
                        rotate(i % 2 == layers % 2 ? 180 / sides : 0)
                            poly_cylinder(r = r, h = lh, center = false, sides = sides);
                    else
                        poly_cylinder(r = r, h = lh, center = false);
                }

            remainder = h / 2 - layers * layer_height;
            if(remainder > 0)
                translate_z(layers * layer_height)
                    poly_cylinder(r = rmin, h = remainder, center = false);
        }
}

module screw_and_washer(type, length, star = false, penny = false) { //! Screw with a washer which can be standard or penny and an optional star washer on top
    washer = screw_washer(type);
    head_type = screw_head_type(type);

    if(head_type != hs_cs && head_type != hs_cs_cap) {
        translate_z(exploded() * 6)
            if(penny)
                penny_washer(washer);
            else
                washer(washer);

        translate_z(washer_thickness(washer)) {
            if(star) {
                translate_z(exploded() * 8)
                    star_washer(washer);

                translate_z(washer_thickness(washer))
                    screw(type, length);
            }
            else
                screw(type, length);
        }
    }
    else
        translate_z(eps)
            screw(type, length);
}