NopSCADlib/utils/core/polyholes.scad

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OpenSCAD

//
// 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/>.
//
//
//! A method of making 3D printed holes come out the right size regardless of the printer, providing
//! it gets the linear dimensions right. See <https://hydraraptor.blogspot.com/2011/02/polyholes.html>
//!
//! The module provides `poly_circle()`, `poly_cylinder()` and `poly_ring()` that is useful for making printed washers and pillars.
//!
//! `poly_cylinder()` has a `twist` parameter which can be set to make the polygon rotate each layer.
//! This can be used to mitigate the number of sides being small and make small holes stronger and more round, but is quite slow due to the
//! large increase in the number of facets.
//! When set to 1 the polygons alternate each layer, when set higher the rotation takes `twist + 1` layers to repeat.
//! A small additional rotation is added to make the polygon rotate one more side over the length of the hole to make it appear round when
//! veiwed end on.
//!
//! When `twist` is set the resulting cylinder is extended by `eps` at each end so that the exact length of the hole can be used without
//! leaving a scar on either surface.
//
function sides(r, n = undef) = is_undef(n) ? max(round(4 * r), 3) : n ? max(n, 3) : r2sides(r); //! Optimium number of sides for specified radius
function corrected_radius(r, n = undef) = r / cos(180 / sides(r, n)); //! Adjusted radius to make flats lie on the circle
function corrected_diameter(d, n = undef) = 2 * corrected_radius(d / 2 , n); //! Adjusted diameter to make flats lie on the circle
module poly_circle(r, sides = undef) { //! Make a circle adjusted to print the correct size
n = sides(r, sides);
circle(r = corrected_radius(r, n), $fn = n);
}
module poly_cylinder(r, h, center = false, sides = undef, chamfer = false, twist = 0) {//! Make a cylinder adjusted to print the correct size
if(twist) {
slices = ceil(h / layer_height);
twists = min(twist + 1, slices);
sides = sides(r, sides);
rot = 360 / sides / twists * (twists < slices ? (1 + 1 / slices) : 1);
if(center)
for(side = [0, 1])
mirror([0, 0, side])
poly_cylinder(r = r, h = h / 2, sides = sides, twist = twist);
else
render(convexity = 5)
for(i = [0 : slices - 1])
translate_z(i * layer_height - eps)
rotate(rot * i)
poly_cylinder(r = r, h = layer_height + 2 * eps, sides = sides);
}
else
extrude_if(h, center)
poly_circle(r, sides);
if(h && chamfer)
poly_cylinder(r + layer_height, center ? layer_height * 2 : layer_height, center, sides = sides(r, sides));
}
module poly_ring(or, ir, sides = undef) { //! Make a 2D ring adjusted to have the correct internal radius
cir = corrected_radius(ir, sides);
filaments = (or - cir) / extrusion_width;
if(filaments > 3 + eps)
difference() {
circle(or);
poly_circle(ir, sides);
}
else
if(filaments >= 2)
difference() {
offset(or - cir)
poly_circle(ir, sides);
poly_circle(ir, sides);
}
else
difference() {
poly_circle(or, sides);
offset(-squeezed_wall)
poly_circle(or, sides);
}
}
module poly_tube(or, ir, h, center = false) //! Make a tube adjusted to have the correct internal radius
extrude_if(h, center)
poly_ring(or, ir);
module drill(r, h = 100, center = true) //! Make a cylinder for drilling holes suitable for CNC routing, set h = 0 for circle
extrude_if(h, center)
circle(r = corrected_radius(r, r2sides(r)));
module poly_drill(r, h = 100, center = true) //! Make a cylinder for drilling holes suitable for CNC routing if cnc_bit_r is non zero, otherwise a poly_cylinder.
if(cnc_bit_r)
drill(r, h, center = true);
else
poly_cylinder(r, h, center);
//
// Horizontal slot
//
module slot(r, l, h = 100) //! Make a horizontal slot suitable for CNC routing, set h = 0 for 2D version
extrude_if(h)
hull() {
translate([l / 2,0])
drill(r, 0);
translate([-l / 2,0])
drill(r, 0);
}