373 lines
15 KiB
OpenSCAD
373 lines
15 KiB
OpenSCAD
|
/*
|
||
|
* ISO-standard metric threads, following this specification:
|
||
|
* http://en.wikipedia.org/wiki/ISO_metric_screw_thread
|
||
|
*
|
||
|
* Copyright 2017 Dan Kirshner - dan_kirshner@yahoo.com
|
||
|
* This program 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.
|
||
|
*
|
||
|
* This program 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.
|
||
|
*
|
||
|
* See <http://www.gnu.org/licenses/>.
|
||
|
*
|
||
|
* Version 2.3. 2017-08-31 Default for leadin: 0 (best for internal threads).
|
||
|
* Version 2.2. 2017-01-01 Correction for angle; leadfac option. (Thanks to
|
||
|
* Andrew Allen <a2intl@gmail.com>.)
|
||
|
* Version 2.1. 2016-12-04 Chamfer bottom end (low-z); leadin option.
|
||
|
* Version 2.0. 2016-11-05 Backwards compatibility (earlier OpenSCAD) fixes.
|
||
|
* Version 1.9. 2016-07-03 Option: tapered.
|
||
|
* Version 1.8. 2016-01-08 Option: (non-standard) angle.
|
||
|
* Version 1.7. 2015-11-28 Larger x-increment - for small-diameters.
|
||
|
* Version 1.6. 2015-09-01 Options: square threads, rectangular threads.
|
||
|
* Version 1.5. 2015-06-12 Options: thread_size, groove.
|
||
|
* Version 1.4. 2014-10-17 Use "faces" instead of "triangles" for polyhedron
|
||
|
* Version 1.3. 2013-12-01 Correct loop over turns -- don't have early cut-off
|
||
|
* Version 1.2. 2012-09-09 Use discrete polyhedra rather than linear_extrude ()
|
||
|
* Version 1.1. 2012-09-07 Corrected to right-hand threads!
|
||
|
*/
|
||
|
|
||
|
// Examples.
|
||
|
//
|
||
|
// Standard M8 x 1.
|
||
|
// metric_thread (diameter=8, pitch=1, length=4);
|
||
|
|
||
|
// Square thread.
|
||
|
// metric_thread (diameter=8, pitch=1, length=4, square=true);
|
||
|
|
||
|
// Non-standard: long pitch, same thread size.
|
||
|
//metric_thread (diameter=8, pitch=4, length=4, thread_size=1, groove=true);
|
||
|
|
||
|
// Non-standard: 20 mm diameter, long pitch, square "trough" width 3 mm,
|
||
|
// depth 1 mm.
|
||
|
//metric_thread (diameter=20, pitch=8, length=16, square=true, thread_size=6,
|
||
|
// groove=true, rectangle=0.333);
|
||
|
|
||
|
// English: 1/4 x 20.
|
||
|
//english_thread (diameter=1/4, threads_per_inch=20, length=1);
|
||
|
|
||
|
// Tapered. Example -- pipe size 3/4" -- per:
|
||
|
// http://www.engineeringtoolbox.com/npt-national-pipe-taper-threads-d_750.html
|
||
|
// english_thread (diameter=1.05, threads_per_inch=14, length=3/4, taper=1/16);
|
||
|
|
||
|
// Thread for mounting on Rohloff hub.
|
||
|
//difference () {
|
||
|
// cylinder (r=20, h=10, $fn=100);
|
||
|
//
|
||
|
// metric_thread (diameter=34, pitch=1, length=10, internal=true, n_starts=6);
|
||
|
//}
|
||
|
|
||
|
|
||
|
// ----------------------------------------------------------------------------
|
||
|
function segments (diameter) = min (50, ceil (diameter*6));
|
||
|
|
||
|
|
||
|
// ----------------------------------------------------------------------------
|
||
|
// diameter - outside diameter of threads in mm. Default: 8.
|
||
|
// pitch - thread axial "travel" per turn in mm. Default: 1.
|
||
|
// length - overall axial length of thread in mm. Default: 1.
|
||
|
// internal - true = clearances for internal thread (e.g., a nut).
|
||
|
// false = clearances for external thread (e.g., a bolt).
|
||
|
// (Internal threads should be "cut out" from a solid using
|
||
|
// difference ()).
|
||
|
// n_starts - Number of thread starts (e.g., DNA, a "double helix," has
|
||
|
// n_starts=2). See wikipedia Screw_thread.
|
||
|
// thread_size - (non-standard) axial width of a single thread "V" - independent
|
||
|
// of pitch. Default: same as pitch.
|
||
|
// groove - (non-standard) subtract inverted "V" from cylinder (rather than
|
||
|
// add protruding "V" to cylinder).
|
||
|
// square - Square threads (per
|
||
|
// https://en.wikipedia.org/wiki/Square_thread_form).
|
||
|
// rectangle - (non-standard) "Rectangular" thread - ratio depth/(axial) width
|
||
|
// Default: 1 (square).
|
||
|
// angle - (non-standard) angle (deg) of thread side from perpendicular to
|
||
|
// axis (default = standard = 30 degrees).
|
||
|
// taper - diameter change per length (National Pipe Thread/ANSI B1.20.1
|
||
|
// is 1" diameter per 16" length). Taper decreases from 'diameter'
|
||
|
// as z increases.
|
||
|
// leadin - 0 (default): no chamfer; 1: chamfer (45 degree) at max-z end;
|
||
|
// 2: chamfer at both ends, 3: chamfer at z=0 end.
|
||
|
// leadfac - scale of leadin chamfer (default: 1.0 = 1/2 thread).
|
||
|
module metric_thread (diameter=8, pitch=1, length=1, internal=false, n_starts=1,
|
||
|
thread_size=-1, groove=false, square=false, rectangle=0,
|
||
|
angle=30, taper=0, leadin=0, leadfac=1.0)
|
||
|
{
|
||
|
// thread_size: size of thread "V" different than travel per turn (pitch).
|
||
|
// Default: same as pitch.
|
||
|
local_thread_size = thread_size == -1 ? pitch : thread_size;
|
||
|
local_rectangle = rectangle ? rectangle : 1;
|
||
|
|
||
|
n_segments = segments (diameter);
|
||
|
h = (square || rectangle) ? local_thread_size*local_rectangle/2 : local_thread_size / (2 * tan(angle));
|
||
|
|
||
|
h_fac1 = (square || rectangle) ? 0.90 : 0.625;
|
||
|
|
||
|
// External thread includes additional relief.
|
||
|
h_fac2 = (square || rectangle) ? 0.95 : 5.3/8;
|
||
|
|
||
|
tapered_diameter = diameter - length*taper;
|
||
|
|
||
|
difference () {
|
||
|
union () {
|
||
|
if (! groove) {
|
||
|
metric_thread_turns (diameter, pitch, length, internal, n_starts,
|
||
|
local_thread_size, groove, square, rectangle, angle,
|
||
|
taper);
|
||
|
}
|
||
|
|
||
|
difference () {
|
||
|
|
||
|
// Solid center, including Dmin truncation.
|
||
|
if (groove) {
|
||
|
cylinder (r1=diameter/2, r2=tapered_diameter/2,
|
||
|
h=length, $fn=n_segments);
|
||
|
} else if (internal) {
|
||
|
cylinder (r1=diameter/2 - h*h_fac1, r2=tapered_diameter/2 - h*h_fac1,
|
||
|
h=length, $fn=n_segments);
|
||
|
} else {
|
||
|
|
||
|
// External thread.
|
||
|
cylinder (r1=diameter/2 - h*h_fac2, r2=tapered_diameter/2 - h*h_fac2,
|
||
|
h=length, $fn=n_segments);
|
||
|
}
|
||
|
|
||
|
if (groove) {
|
||
|
metric_thread_turns (diameter, pitch, length, internal, n_starts,
|
||
|
local_thread_size, groove, square, rectangle,
|
||
|
angle, taper);
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
|
||
|
// chamfer z=0 end if leadin is 2 or 3
|
||
|
if (leadin == 2 || leadin == 3) {
|
||
|
difference () {
|
||
|
cylinder (r=diameter/2 + 1, h=h*h_fac1*leadfac, $fn=n_segments);
|
||
|
|
||
|
cylinder (r2=diameter/2, r1=diameter/2 - h*h_fac1*leadfac, h=h*h_fac1*leadfac,
|
||
|
$fn=n_segments);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
// chamfer z-max end if leadin is 1 or 2.
|
||
|
if (leadin == 1 || leadin == 2) {
|
||
|
translate ([0, 0, length + 0.05 - h*h_fac1*leadfac]) {
|
||
|
difference () {
|
||
|
cylinder (r=diameter/2 + 1, h=h*h_fac1*leadfac, $fn=n_segments);
|
||
|
cylinder (r1=tapered_diameter/2, r2=tapered_diameter/2 - h*h_fac1*leadfac, h=h*h_fac1*leadfac,
|
||
|
$fn=n_segments);
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
|
||
|
|
||
|
// ----------------------------------------------------------------------------
|
||
|
// Input units in inches.
|
||
|
// Note: units of measure in drawing are mm!
|
||
|
module english_thread (diameter=0.25, threads_per_inch=20, length=1,
|
||
|
internal=false, n_starts=1, thread_size=-1, groove=false,
|
||
|
square=false, rectangle=0, angle=30, taper=0, leadin=0,
|
||
|
leadfac=1.0)
|
||
|
{
|
||
|
// Convert to mm.
|
||
|
mm_diameter = diameter*25.4;
|
||
|
mm_pitch = (1.0/threads_per_inch)*25.4;
|
||
|
mm_length = length*25.4;
|
||
|
|
||
|
echo (str ("mm_diameter: ", mm_diameter));
|
||
|
echo (str ("mm_pitch: ", mm_pitch));
|
||
|
echo (str ("mm_length: ", mm_length));
|
||
|
metric_thread (mm_diameter, mm_pitch, mm_length, internal, n_starts,
|
||
|
thread_size, groove, square, rectangle, angle, taper, leadin,
|
||
|
leadfac);
|
||
|
}
|
||
|
|
||
|
// ----------------------------------------------------------------------------
|
||
|
module metric_thread_turns (diameter, pitch, length, internal, n_starts,
|
||
|
thread_size, groove, square, rectangle, angle,
|
||
|
taper)
|
||
|
{
|
||
|
// Number of turns needed.
|
||
|
n_turns = floor (length/pitch);
|
||
|
|
||
|
intersection () {
|
||
|
|
||
|
// Start one below z = 0. Gives an extra turn at each end.
|
||
|
for (i=[-1*n_starts : n_turns+1]) {
|
||
|
translate ([0, 0, i*pitch]) {
|
||
|
metric_thread_turn (diameter, pitch, internal, n_starts,
|
||
|
thread_size, groove, square, rectangle, angle,
|
||
|
taper, i*pitch);
|
||
|
}
|
||
|
}
|
||
|
|
||
|
// Cut to length.
|
||
|
translate ([0, 0, length/2]) {
|
||
|
cube ([diameter*3, diameter*3, length], center=true);
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
|
||
|
|
||
|
// ----------------------------------------------------------------------------
|
||
|
module metric_thread_turn (diameter, pitch, internal, n_starts, thread_size,
|
||
|
groove, square, rectangle, angle, taper, z)
|
||
|
{
|
||
|
n_segments = segments (diameter);
|
||
|
fraction_circle = 1.0/n_segments;
|
||
|
for (i=[0 : n_segments-1]) {
|
||
|
rotate ([0, 0, i*360*fraction_circle]) {
|
||
|
translate ([0, 0, i*n_starts*pitch*fraction_circle]) {
|
||
|
//current_diameter = diameter - taper*(z + i*n_starts*pitch*fraction_circle);
|
||
|
thread_polyhedron ((diameter - taper*(z + i*n_starts*pitch*fraction_circle))/2,
|
||
|
pitch, internal, n_starts, thread_size, groove,
|
||
|
square, rectangle, angle);
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
|
||
|
|
||
|
// ----------------------------------------------------------------------------
|
||
|
module thread_polyhedron (radius, pitch, internal, n_starts, thread_size,
|
||
|
groove, square, rectangle, angle)
|
||
|
{
|
||
|
n_segments = segments (radius*2);
|
||
|
fraction_circle = 1.0/n_segments;
|
||
|
|
||
|
local_rectangle = rectangle ? rectangle : 1;
|
||
|
|
||
|
h = (square || rectangle) ? thread_size*local_rectangle/2 : thread_size / (2 * tan(angle));
|
||
|
outer_r = radius + (internal ? h/20 : 0); // Adds internal relief.
|
||
|
//echo (str ("outer_r: ", outer_r));
|
||
|
|
||
|
// A little extra on square thread -- make sure overlaps cylinder.
|
||
|
h_fac1 = (square || rectangle) ? 1.1 : 0.875;
|
||
|
inner_r = radius - h*h_fac1; // Does NOT do Dmin_truncation - do later with
|
||
|
// cylinder.
|
||
|
|
||
|
translate_y = groove ? outer_r + inner_r : 0;
|
||
|
reflect_x = groove ? 1 : 0;
|
||
|
|
||
|
// Make these just slightly bigger (keep in proportion) so polyhedra will
|
||
|
// overlap.
|
||
|
x_incr_outer = (! groove ? outer_r : inner_r) * fraction_circle * 2 * PI * 1.02;
|
||
|
x_incr_inner = (! groove ? inner_r : outer_r) * fraction_circle * 2 * PI * 1.02;
|
||
|
z_incr = n_starts * pitch * fraction_circle * 1.005;
|
||
|
|
||
|
/*
|
||
|
(angles x0 and x3 inner are actually 60 deg)
|
||
|
|
||
|
/\ (x2_inner, z2_inner) [2]
|
||
|
/ \
|
||
|
(x3_inner, z3_inner) / \
|
||
|
[3] \ \
|
||
|
|\ \ (x2_outer, z2_outer) [6]
|
||
|
| \ /
|
||
|
| \ /|
|
||
|
z |[7]\/ / (x1_outer, z1_outer) [5]
|
||
|
| | | /
|
||
|
| x | |/
|
||
|
| / | / (x0_outer, z0_outer) [4]
|
||
|
| / | / (behind: (x1_inner, z1_inner) [1]
|
||
|
|/ | /
|
||
|
y________| |/
|
||
|
(r) / (x0_inner, z0_inner) [0]
|
||
|
|
||
|
*/
|
||
|
|
||
|
x1_outer = outer_r * fraction_circle * 2 * PI;
|
||
|
|
||
|
z0_outer = (outer_r - inner_r) * tan(angle);
|
||
|
//echo (str ("z0_outer: ", z0_outer));
|
||
|
|
||
|
//polygon ([[inner_r, 0], [outer_r, z0_outer],
|
||
|
// [outer_r, 0.5*pitch], [inner_r, 0.5*pitch]]);
|
||
|
z1_outer = z0_outer + z_incr;
|
||
|
|
||
|
// Give internal square threads some clearance in the z direction, too.
|
||
|
bottom = internal ? 0.235 : 0.25;
|
||
|
top = internal ? 0.765 : 0.75;
|
||
|
|
||
|
translate ([0, translate_y, 0]) {
|
||
|
mirror ([reflect_x, 0, 0]) {
|
||
|
|
||
|
if (square || rectangle) {
|
||
|
|
||
|
// Rule for face ordering: look at polyhedron from outside: points must
|
||
|
// be in clockwise order.
|
||
|
polyhedron (
|
||
|
points = [
|
||
|
[-x_incr_inner/2, -inner_r, bottom*thread_size], // [0]
|
||
|
[x_incr_inner/2, -inner_r, bottom*thread_size + z_incr], // [1]
|
||
|
[x_incr_inner/2, -inner_r, top*thread_size + z_incr], // [2]
|
||
|
[-x_incr_inner/2, -inner_r, top*thread_size], // [3]
|
||
|
|
||
|
[-x_incr_outer/2, -outer_r, bottom*thread_size], // [4]
|
||
|
[x_incr_outer/2, -outer_r, bottom*thread_size + z_incr], // [5]
|
||
|
[x_incr_outer/2, -outer_r, top*thread_size + z_incr], // [6]
|
||
|
[-x_incr_outer/2, -outer_r, top*thread_size] // [7]
|
||
|
],
|
||
|
|
||
|
faces = [
|
||
|
[0, 3, 7, 4], // This-side trapezoid
|
||
|
|
||
|
[1, 5, 6, 2], // Back-side trapezoid
|
||
|
|
||
|
[0, 1, 2, 3], // Inner rectangle
|
||
|
|
||
|
[4, 7, 6, 5], // Outer rectangle
|
||
|
|
||
|
// These are not planar, so do with separate triangles.
|
||
|
[7, 2, 6], // Upper rectangle, bottom
|
||
|
[7, 3, 2], // Upper rectangle, top
|
||
|
|
||
|
[0, 5, 1], // Lower rectangle, bottom
|
||
|
[0, 4, 5] // Lower rectangle, top
|
||
|
]
|
||
|
);
|
||
|
} else {
|
||
|
|
||
|
// Rule for face ordering: look at polyhedron from outside: points must
|
||
|
// be in clockwise order.
|
||
|
polyhedron (
|
||
|
points = [
|
||
|
[-x_incr_inner/2, -inner_r, 0], // [0]
|
||
|
[x_incr_inner/2, -inner_r, z_incr], // [1]
|
||
|
[x_incr_inner/2, -inner_r, thread_size + z_incr], // [2]
|
||
|
[-x_incr_inner/2, -inner_r, thread_size], // [3]
|
||
|
|
||
|
[-x_incr_outer/2, -outer_r, z0_outer], // [4]
|
||
|
[x_incr_outer/2, -outer_r, z0_outer + z_incr], // [5]
|
||
|
[x_incr_outer/2, -outer_r, thread_size - z0_outer + z_incr], // [6]
|
||
|
[-x_incr_outer/2, -outer_r, thread_size - z0_outer] // [7]
|
||
|
],
|
||
|
|
||
|
faces = [
|
||
|
[0, 3, 7, 4], // This-side trapezoid
|
||
|
|
||
|
[1, 5, 6, 2], // Back-side trapezoid
|
||
|
|
||
|
[0, 1, 2, 3], // Inner rectangle
|
||
|
|
||
|
[4, 7, 6, 5], // Outer rectangle
|
||
|
|
||
|
// These are not planar, so do with separate triangles.
|
||
|
[7, 2, 6], // Upper rectangle, bottom
|
||
|
[7, 3, 2], // Upper rectangle, top
|
||
|
|
||
|
[0, 5, 1], // Lower rectangle, bottom
|
||
|
[0, 4, 5] // Lower rectangle, top
|
||
|
]
|
||
|
);
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
}
|