Added involute_gear_od() function.

Changed some teardrop holes to teardrop plus.
Reimplemented teardrop_plus() again.
2025-09-04 20:56:07 +02:00 · 2020-07-28 21:24:01 +01:00 · 2020-07-20 20:39:01 +01:00 · 2020-07-20 16:55:55 +01:00 · 2020-07-18 23:53:15 +01:00 · 2020-07-18 19:28:26 +01:00
20 changed files with 346 additions and 86 deletions
--- a/libtest.scad
+++ b/libtest.scad
@@ -73,7 +73,7 @@ use <tests/spades.scad>
 use <tests/springs.scad>
 use <tests/SSRs.scad>
 use <tests/stepper_motors.scad>
-use <tests/swiss_clips.scad>
+use <tests/Swiss_clips.scad>
 use <tests/toggles.scad>
 use <tests/transformers.scad>
 use <tests/tubings.scad>
--- a/printed/door_hinge.scad
+++ b/printed/door_hinge.scad
@@ -74,7 +74,7 @@ module door_hinge(door_thickness) {                         //! Generates STL fo
                            square([1, thickness + door_thickness]);
                    }
                    translate([dia / 2, thickness + door_thickness / 2])
-                        teardrop(r = screw_clearance_radius(pin_screw), h = 0);
+                        teardrop_plus(r = screw_clearance_radius(pin_screw), h = 0);
                }
        linear_extrude(thickness)
            difference() {
@@ -127,7 +127,7 @@ module door_hinge_stat_stl() { //! Generates the STL for the stationary part
                            square([dia, 1], center = true);
                    }
                    translate([0, dia / 2 + stat_clearance])
-                        teardrop(r = screw_clearance_radius(pin_screw), h = 0);
+                        teardrop_plus(r = screw_clearance_radius(pin_screw), h = 0);
               }
    }
 }
--- a/readme.md
+++ b/readme.md
@@ -24,18 +24,18 @@ See [usage](docs/usage.md) for requirements, installation instructions and a usa
 <tr><td> <a href = "#Belts">Belts</a> </td><td> <a href = "#LED_meters">LED_meters</a> </td><td> <a href = "#Rod">Rod</a> </td><td> <a href = "#Carriers">Carriers</a> </td><td> <a href = "#Fillet">Fillet</a> </td><td> <a href = "#Polyholes">Polyholes</a> </td></tr>
 <tr><td> <a href = "#Blowers">Blowers</a> </td><td> <a href = "#LEDs">LEDs</a> </td><td> <a href = "#SCS_bearing_blocks">SCS_bearing_blocks</a> </td><td> <a href = "#Corner_block">Corner_block</a> </td><td> <a href = "#Gears">Gears</a> </td><td> <a href = "#Rounded_rectangle">Rounded_rectangle</a> </td></tr>
 <tr><td> <a href = "#Bulldogs">Bulldogs</a> </td><td> <a href = "#Leadnuts">Leadnuts</a> </td><td> <a href = "#SK_brackets">SK_brackets</a> </td><td> <a href = "#Door_hinge">Door_hinge</a> </td><td> <a href = "#Hanging_hole">Hanging_hole</a> </td><td> <a href = "#Sphere">Sphere</a> </td></tr>
-<tr><td> <a href = "#Buttons">Buttons</a> </td><td> <a href = "#Light_strips">Light_strips</a> </td><td> <a href = "#SMDs">SMDs</a> </td><td> <a href = "#Door_latch">Door_latch</a> </td><td> <a href = "#Layout">Layout</a> </td><td> <a href = "#Teardrops">Teardrops</a> </td></tr>
-<tr><td> <a href = "#Cable_strips">Cable_strips</a> </td><td> <a href = "#Linear_bearings">Linear_bearings</a> </td><td> <a href = "#SSRs">SSRs</a> </td><td> <a href = "#Fan_guard">Fan_guard</a> </td><td> <a href = "#Maths">Maths</a> </td><td></td></tr>
-<tr><td> <a href = "#Cameras">Cameras</a> </td><td> <a href = "#Mains_sockets">Mains_sockets</a> </td><td> <a href = "#Screws">Screws</a> </td><td> <a href = "#Fixing_block">Fixing_block</a> </td><td> <a href = "#Offset">Offset</a> </td><td></td></tr>
-<tr><td> <a href = "#Circlips">Circlips</a> </td><td> <a href = "#Microswitches">Microswitches</a> </td><td> <a href = "#Sealing_strip">Sealing_strip</a> </td><td> <a href = "#Flat_hinge">Flat_hinge</a> </td><td> <a href = "#Quadrant">Quadrant</a> </td><td></td></tr>
-<tr><td> <a href = "#Components">Components</a> </td><td> <a href = "#Microview">Microview</a> </td><td> <a href = "#Sheets">Sheets</a> </td><td> <a href = "#Foot">Foot</a> </td><td> <a href = "#Round">Round</a> </td><td></td></tr>
-<tr><td> <a href = "#DIP">DIP</a> </td><td> <a href = "#Modules">Modules</a> </td><td> <a href = "#Spades">Spades</a> </td><td> <a href = "#Handle">Handle</a> </td><td> <a href = "#Rounded_cylinder">Rounded_cylinder</a> </td><td></td></tr>
-<tr><td> <a href = "#D_connectors">D_connectors</a> </td><td> <a href = "#Nuts">Nuts</a> </td><td> <a href = "#Spools">Spools</a> </td><td> <a href = "#PCB_mount">PCB_mount</a> </td><td> <a href = "#Rounded_polygon">Rounded_polygon</a> </td><td></td></tr>
-<tr><td> <a href = "#Displays">Displays</a> </td><td> <a href = "#O_ring">O_ring</a> </td><td> <a href = "#Springs">Springs</a> </td><td> <a href = "#PSU_shroud">PSU_shroud</a> </td><td> <a href = "#Sector">Sector</a> </td><td></td></tr>
-<tr><td> <a href = "#Extrusion_brackets">Extrusion_brackets</a> </td><td> <a href = "#Opengrab">Opengrab</a> </td><td> <a href = "#Stepper_motors">Stepper_motors</a> </td><td> <a href = "#Printed_box">Printed_box</a> </td><td> <a href = "#Sweep">Sweep</a> </td><td></td></tr>
-<tr><td> <a href = "#Extrusions">Extrusions</a> </td><td> <a href = "#PCB">PCB</a> </td><td> <a href = "#Swiss_clips">Swiss_clips</a> </td><td> <a href = "#Ribbon_clamp">Ribbon_clamp</a> </td><td> <a href = "#Thread">Thread</a> </td><td></td></tr>
-<tr><td> <a href = "#Fans">Fans</a> </td><td> <a href = "#PCBs">PCBs</a> </td><td> <a href = "#Toggles">Toggles</a> </td><td> <a href = "#SSR_shroud">SSR_shroud</a> </td><td> <a href = "#Tube">Tube</a> </td><td></td></tr>
-<tr><td> <a href = "#Fuseholder">Fuseholder</a> </td><td> <a href = "#PSUs">PSUs</a> </td><td> <a href = "#Transformers">Transformers</a> </td><td> <a href = "#Screw_knob">Screw_knob</a> </td><td></td><td></td></tr>
+<tr><td> <a href = "#Buttons">Buttons</a> </td><td> <a href = "#Light_strips">Light_strips</a> </td><td> <a href = "#SMDs">SMDs</a> </td><td> <a href = "#Door_latch">Door_latch</a> </td><td> <a href = "#Horiholes">Horiholes</a> </td><td> <a href = "#Teardrops">Teardrops</a> </td></tr>
+<tr><td> <a href = "#Cable_strips">Cable_strips</a> </td><td> <a href = "#Linear_bearings">Linear_bearings</a> </td><td> <a href = "#SSRs">SSRs</a> </td><td> <a href = "#Fan_guard">Fan_guard</a> </td><td> <a href = "#Layout">Layout</a> </td><td></td></tr>
+<tr><td> <a href = "#Cameras">Cameras</a> </td><td> <a href = "#Mains_sockets">Mains_sockets</a> </td><td> <a href = "#Screws">Screws</a> </td><td> <a href = "#Fixing_block">Fixing_block</a> </td><td> <a href = "#Maths">Maths</a> </td><td></td></tr>
+<tr><td> <a href = "#Circlips">Circlips</a> </td><td> <a href = "#Microswitches">Microswitches</a> </td><td> <a href = "#Sealing_strip">Sealing_strip</a> </td><td> <a href = "#Flat_hinge">Flat_hinge</a> </td><td> <a href = "#Offset">Offset</a> </td><td></td></tr>
+<tr><td> <a href = "#Components">Components</a> </td><td> <a href = "#Microview">Microview</a> </td><td> <a href = "#Sheets">Sheets</a> </td><td> <a href = "#Foot">Foot</a> </td><td> <a href = "#Quadrant">Quadrant</a> </td><td></td></tr>
+<tr><td> <a href = "#DIP">DIP</a> </td><td> <a href = "#Modules">Modules</a> </td><td> <a href = "#Spades">Spades</a> </td><td> <a href = "#Handle">Handle</a> </td><td> <a href = "#Round">Round</a> </td><td></td></tr>
+<tr><td> <a href = "#D_connectors">D_connectors</a> </td><td> <a href = "#Nuts">Nuts</a> </td><td> <a href = "#Spools">Spools</a> </td><td> <a href = "#PCB_mount">PCB_mount</a> </td><td> <a href = "#Rounded_cylinder">Rounded_cylinder</a> </td><td></td></tr>
+<tr><td> <a href = "#Displays">Displays</a> </td><td> <a href = "#O_ring">O_ring</a> </td><td> <a href = "#Springs">Springs</a> </td><td> <a href = "#PSU_shroud">PSU_shroud</a> </td><td> <a href = "#Rounded_polygon">Rounded_polygon</a> </td><td></td></tr>
+<tr><td> <a href = "#Extrusion_brackets">Extrusion_brackets</a> </td><td> <a href = "#Opengrab">Opengrab</a> </td><td> <a href = "#Stepper_motors">Stepper_motors</a> </td><td> <a href = "#Printed_box">Printed_box</a> </td><td> <a href = "#Sector">Sector</a> </td><td></td></tr>
+<tr><td> <a href = "#Extrusions">Extrusions</a> </td><td> <a href = "#PCB">PCB</a> </td><td> <a href = "#Swiss_clips">Swiss_clips</a> </td><td> <a href = "#Ribbon_clamp">Ribbon_clamp</a> </td><td> <a href = "#Sweep">Sweep</a> </td><td></td></tr>
+<tr><td> <a href = "#Fans">Fans</a> </td><td> <a href = "#PCBs">PCBs</a> </td><td> <a href = "#Toggles">Toggles</a> </td><td> <a href = "#SSR_shroud">SSR_shroud</a> </td><td> <a href = "#Thread">Thread</a> </td><td></td></tr>
+<tr><td> <a href = "#Fuseholder">Fuseholder</a> </td><td> <a href = "#PSUs">PSUs</a> </td><td> <a href = "#Transformers">Transformers</a> </td><td> <a href = "#Screw_knob">Screw_knob</a> </td><td> <a href = "#Tube">Tube</a> </td><td></td></tr>
 <tr><td> <a href = "#Geared_steppers">Geared_steppers</a> </td><td> <a href = "#Panel_meters">Panel_meters</a> </td><td> <a href = "#Tubings">Tubings</a> </td><td> <a href = "#Socket_box">Socket_box</a> </td><td></td><td></td></tr>
 <tr><td> <a href = "#Green_terminals">Green_terminals</a> </td><td> <a href = "#Pillars">Pillars</a> </td><td> <a href = "#Variacs">Variacs</a> </td><td> <a href = "#Strap_handle">Strap_handle</a> </td><td></td><td></td></tr>
 <tr><td> <a href = "#Hot_ends">Hot_ends</a> </td><td> <a href = "#Pin_headers">Pin_headers</a> </td><td> <a href = "#Veroboard">Veroboard</a> </td><td></td><td></td><td></td></tr>
@@ -5229,6 +5229,7 @@ Rounded fillet for adding to corners.
 Utilities for making involute gears.

 Formulas from <https://khkgears.net/new/gear_knowledge/gear_technical_reference/involute_gear_profile.html>
+<https://khkgears.net/new/gear_knowledge/gear_technical_reference/calculation_gear_dimensions.html>
 and <https://www.tec-science.com/mechanical-power-transmission/involute-gear/calculation-of-involute-gears/>

 ```involute_gear_profile()``` returns a polygon that can have the bore and spokes, etc, subtracted from it before linear extruding it to 3D.
@@ -5239,6 +5240,10 @@ the practical minimum.

 The clearance between tip and root defaults to module / 6, but can be overridden by setting the ```clearance``` parameter.

+The origin of the rack is the left end of the pitch line and its width is below the pitch line. I.e. it does not include the addendum.
+
+```involute_worm_profile()``` returns a tooth profile that can be passed to ```thread()``` to make worms.
+

 [utils/gears.scad](utils/gears.scad) Implementation.

@@ -5247,14 +5252,18 @@ The clearance between tip and root defaults to module / 6, but can be overridden
 ### Functions
 | Function | Description |
 |:--- |:--- |
-| ```centre_distance(m, z1, z2, pa)``` | Calculate distance between centres taking profile shift into account |
+| ```centre_distance(m, z1, z2, pa = 20)``` | Calculate distance between centres taking profile shift into account |
 | ```involute(r, u)``` | Involute of circle radius r at angle u in radians |
+| ```involute_gear_od(m, z, pa = 20)``` | involute gear outside diameter given modulus, tooth count and pressure angle |
+| ```involute_rack_tooth_profile(m, pa = 20, clearance = undef)``` | Calculate rack tooth profile given module and pressure angle |
+| ```involute_worm_profile(m, pa = 20, clearance = undef)``` | Calculate worm profile suitable for passing to thread() |
 | ```profile_shift(z, pa)``` | Calculate profile shift for small gears |

 ### Modules
 | Module | Description |
 |:--- |:--- |
-| ```involute_gear_profile(m, z, pa = 20, clearance = undef, steps = 20)``` | Calculate profile given module, number of teeth and pressure angle |
+| ```involute_gear_profile(m, z, pa = 20, clearance = undef, steps = 20)``` | Calculate gear profile given module, number of teeth and pressure angle |
+| ```involute_rack_profile(m, z, w, pa = 20, clearance = undef)``` | Calculate rack profile given module, number of teeth and pressure angle |

 ![gears](tests/png/gears.png)

@@ -5279,6 +5288,31 @@ Method to print holes in mid air. See <https://hydraraptor.blogspot.com/2014/03/
 ![hanging_hole](tests/png/hanging_hole.png)


+<a href="#top">Top</a>
+
+---
+<a name="Horiholes"></a>
+## Horiholes
+Utilities for depicting the staircase slicing of horizontal holes made with [`teardrop_plus()`](#teardrops), see <https://hydraraptor.blogspot.com/2020/07/horiholes-2.html>
+
+
+[utils/horiholes.scad](utils/horiholes.scad) Implementation.
+
+[tests/horiholes.scad](tests/horiholes.scad) Code for this example.
+
+### Functions
+| Function | Description |
+|:--- |:--- |
+| ```teardrop_plus_x(r, y, h)``` | Calculate the ordinate of a compensated teardrop given y and layer height. |
+
+### Modules
+| Module | Description |
+|:--- |:--- |
+| ```horihole(r, z, h = 0, center = true)``` | For making horizontal holes that don't need support material and are correct dimensions |
+
+![horiholes](tests/png/horiholes.png)
+
+
 <a href="#top">Top</a>

 ---
@@ -5543,6 +5577,8 @@ specify a chamfer angle.
 Threads are by default solid, so the male version is wrapped around a cylinder and the female inside a tube. This can be suppressed to just get the helix, for
 example to make a printed pot with a screw top lid.

+A left hand thread can be made by using mirror([0,1]).
+
 Threads with a typical 60 degree angle appear too bright with OpenSCAD's primitive lighting model as they face towards the lights more than the top and sides of
 a cylinder. To get around this a colour can be passed to thread that is used to colour the cylinder and then toned down to colour the helix.

@@ -5569,7 +5605,7 @@ Threads obey the $fn, $fa, $fs variables.
 |:--- |:--- |
 | ```female_metric_thread(d, pitch, length, center = true, top = -1, bot = -1, colour = undef)``` | Create female thread with metric profile |
 | ```male_metric_thread(d, pitch, length, center = true, top = -1, bot = -1, solid = true, colour = undef)``` | Create male thread with metric profile |
-| ```thread(dia, pitch, length, profile, center = true, top = -1, bot = -1, starts = 1, solid = true, female = false, colour = undef)``` | Create male or femail thread, ends can be tapered, chamfered or square |
+| ```thread(dia, pitch, length, profile, center = true, top = -1, bot = -1, starts = 1, solid = true, female = false, colour = undef)``` | Create male or female thread, ends can be tapered, chamfered or square |

 ![thread](tests/png/thread.png)

@@ -5849,6 +5885,9 @@ This ensures `hull` and `minkowski` results have the correct dimensions when sph
 For making horizontal holes that don't need support material.
 Small holes can get away without it, but they print better with truncated teardrops.

+Using teardrop_plus() or setting the plus option on other modules will elongate the teardrop vertically by the layer height, so when sliced the staircase tips
+do not intrude into the circle. See <https://hydraraptor.blogspot.com/2020/07/horiholes-2.html>
+

 [utils/core/teardrops.scad](utils/core/teardrops.scad) Implementation.

@@ -5857,12 +5896,12 @@ Small holes can get away without it, but they print better with truncated teardr
 ### Modules
 | Module | Description |
 |:--- |:--- |
-| ```semi_teardrop(h, r, d = undef, center = true, chamfer = 0)``` | A semi teardrop in the positive Y domain |
-| ```teardrop(h, r, center = true, truncate = true, chamfer = 0)``` | For making horizontal holes that don't need support material, set ```truncate = false``` to make traditional RepRap teardrops that don't even need bridging |
+| ```semi_teardrop(h, r, d = undef, center = true, chamfer = 0, plus = false)``` | A semi teardrop in the positive Y domain |
+| ```teardrop(h, r, center = true, truncate = true, chamfer = 0, plus = false)``` | For making horizontal holes that don't need support material, set ```truncate = false``` to make traditional RepRap teardrops that don't even need bridging |
 | ```teardrop_chamfer(h, center, chamfer)``` | Helper module for adding chamfer to a teardrop |
-| ```teardrop_plus(h, r, center = true, truncate = true, chamfer = 0)``` | Slightly bigger teardrop to allow for the 3D printing staircase effect |
-| ```tearslot(h, r, w, center = true, chamfer = 0)``` | A horizontal slot that doesn't need support material |
-| ```vertical_tearslot(h, r, l, center = true, chamfer = 0)``` | A vertical slot that doesn't need support material |
+| ```teardrop_plus(h, r, center = true, truncate = true, chamfer = 0)``` | Slightly elongated teardrop to allow for the 3D printing staircase effect |
+| ```tearslot(h, r, w, center = true, chamfer = 0, plus = false)``` | A horizontal slot that doesn't need support material |
+| ```vertical_tearslot(h, r, l, center = true, chamfer = 0, plus = false)``` | A vertical slot that doesn't need support material |

 ![teardrops](tests/png/teardrops.png)

--- a/tests/gears.scad
+++ b/tests/gears.scad
@@ -35,7 +35,7 @@ $show_numbers = false;

 module gears() {
    color(pp1_colour)
-        rotate($t * 360)
+        rotate(-$t * 360)
            linear_extrude(eps, center = true, convexity = z1)
                difference() {
                    involute_gear_profile(m, z1, pa);
@@ -45,13 +45,21 @@ module gears() {

    color(pp2_colour)
        translate([centre_distance(m, z1, z2, pa), 0])
-            rotate(180 + 180 / z2 + -$t * 360 * z1 / z2)
+            rotate(180 + 180 / z2 + $t * 360 * z1 / z2)
               linear_extrude(eps, center = true, convexity = z2)
                    difference() {
                         involute_gear_profile(m, z2, pa);

                         circle(r = m * z2 / 10);
                    }
+
+    z3 = floor((z1 + z2) / PI);
+    angle = -$t * 360 + 90 - floor(z1 / 4) * 360 / z1; // Line up the rack 1/4 turn around the gear
+    pitch = m * PI;
+    color(pp3_colour)
+        translate([(angle % ((z3 / z1) * 360)) / 360 * z1 * pitch, -centre_distance(m, z1, 0, pa)])
+            linear_extrude(eps, center = true)
+                involute_rack_profile(m, z3, 3 * m, pa);
 }

 rotate(is_undef($bom) ? 0 : [70, 0, 315])
--- a/tests/horiholes.scad
+++ b/tests/horiholes.scad
@@ -0,0 +1,90 @@
+//
+// NopSCADlib Copyright Chris Palmer 2020
+// nop.head@gmail.com
+// hydraraptor.blogspot.com
+//
+// This file is part of NopSCADlib.
+//
+// NopSCADlib is free software: you can redistribute it and/or modify it under the terms of the
+// GNU General Public License as published by the Free Software Foundation, either version 3 of
+// the License, or (at your option) any later version.
+//
+// NopSCADlib is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+// without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+// See the GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License along with NopSCADlib.
+// If not, see <https://www.gnu.org/licenses/>.
+//
+$layer_height = 0.25;
+include <../utils/core/core.scad>
+use <../utils/horiholes.scad>
+
+show_disc = true;
+use_horihole = true;
+thickness = 6;
+length = 60;
+height = 20;
+overlap_x = 15;
+overlap_y = 10;
+
+module hole_positions() {
+    x0 = (length - 40) / 2;
+    for($i = [0 : 4], $z = 5 + $i * layer_height / 5, $r = 3)
+        translate([x0 + $i * 10, $z])
+            children();
+
+    for($i = [0 : 4], $z = 15 + $i * layer_height / 5, $r = 0.5 + $i / 2)
+        translate([x0 + $i * 10, $z])
+            children();
+}
+
+module horiholes_stl(t = thickness) {
+    rotate([90, 0, 0])
+        difference() {
+            linear_extrude(t, center = true) {
+                difference() {
+                    square([length, height]);
+
+                    hole_positions()
+                        if(use_horihole)
+                            horihole($r, $z);
+                        else
+                            teardrop_plus(h = 0, r = $r);
+                }
+            }
+        }
+    if(t == thickness)
+        translate([length / 2, 0])
+            rounded_rectangle([length + 2 * overlap_x, thickness + 2 * overlap_y, 2], 5);
+}
+
+module horiholes() {
+    stl_colour(pp1_colour)
+        rotate([-90, 0, 0])
+            horiholes_stl(eps);
+
+    if(show_disc)
+        hole_positions()
+            color(silver)
+                cylinder(r = $r, h = eps, center = true, $fn = 360);
+
+    hole_positions()
+        color("red")
+            linear_extrude(2 * eps, center = true)
+                intersection() {
+                    difference() {
+                        square(8, center = true);
+
+                        horihole($r, $z);
+                    }
+
+                    circle($r, $fn = 360);
+                }
+}
+
+if($preview)
+    rotate(is_undef($bom) ? 0 : [70, 0, 315])
+        horiholes();
+else
+    horiholes_stl();
--- a/tests/png/door_hinge.png
+++ b/tests/png/door_hinge.png
--- a/tests/png/flat_hinge.png
+++ b/tests/png/flat_hinge.png
--- a/tests/png/gears.png
+++ b/tests/png/gears.png
--- a/tests/png/horiholes.png
+++ b/tests/png/horiholes.png
--- a/tests/png/teardrops.png
+++ b/tests/png/teardrops.png
--- a/tests/png/thread.png
+++ b/tests/png/thread.png
--- a/tests/png/wire.png
+++ b/tests/png/wire.png
--- a/tests/printed_box.scad
+++ b/tests/printed_box.scad
@@ -67,7 +67,7 @@ module box1_external_additions() {

 module box1_holes() {
    box1_feet_positions()
-        teardrop(r = screw_pilot_hole(foot_screw(foot)), h = 10, center = true);
+        teardrop_plus(r = screw_pilot_hole(foot_screw(foot)), h = 10, center = true);
 }


--- a/tests/teardrops.scad
+++ b/tests/teardrops.scad
@@ -41,7 +41,10 @@ module teardrops() {

                        translate([20, 10])
                            semi_teardrop(h = 0, r = 3);
-                    }
+
+                        translate([20, 20])
+                            teardrop(h = 0, r = 3, truncate = false, plus = true);
+                   }
                }
                translate([40, 0, 1.5]) {
                    h = 3 + eps;
@@ -61,6 +64,9 @@ module teardrops() {

                    translate([20, 10])
                        semi_teardrop(h = h, r = 3, chamfer = chamfer);
+
+                    translate([20, 20])
+                        teardrop(h = h, r = 3, truncate = false, plus = false, chamfer = chamfer);
                }
            }
 }
--- a/tests/thread.scad
+++ b/tests/thread.scad
@@ -26,27 +26,27 @@ profile = thread_profile(pitch / 2, pitch * 0.366, 30);

 module threads()
    for(female = [false, true]) translate([0, female ? -20 : 0]) {
-    length = female ? 8  : 40;
-    dia = female ? 8 : 8 - pitch;
-    colour = female ? brass : silver;
+        length = female ? 8  : 40;
+        dia = female ? 8 : 8 - pitch;
+        colour = female ? brass : silver;

-    thread(dia, starts * pitch, length, profile, starts = starts, top = 45, bot = 45, female = female, colour = colour);
+        thread(dia, starts * pitch, length, profile, starts = starts, top = 45, bot = 45, female = female, colour = colour);

-    color(colour)
-        translate([20, 0])
-            thread(dia, starts * pitch, length, profile, starts = starts, top = 0, bot = 0, female = female);
+        color(colour)
+            translate([20, 0])
+                thread(dia, starts * pitch, length, profile, starts = starts, top = 0, bot = 0, female = female);

-    translate([40, 0])
-        thread(dia, starts * pitch, length, profile, starts = starts, top = -1, bot = -1, female = female, colour = colour);
+        translate([40, 0])
+            thread(dia, starts * pitch, length, profile, starts = starts, top = -1, bot = -1, female = female, colour = colour);

-    color(colour)
-        translate([60, 0])
-            thread(dia, 2 * pitch, length, profile, starts = 2, top = -1, bot = -1, female = female);
+        color(colour)
+            translate([60, 0])
+                thread(dia, 2 * pitch, length, profile, starts = 2, top = -1, bot = -1, female = female);

-    color(colour)
-        translate([80, 0])
-            thread(dia, pitch, length, profile, starts = 1, top = -1, bot = -1, female = female);
-}
+        color(colour)
+            translate([80, 0])
+                thread(dia, pitch, length, profile, starts = 1, top = -1, bot = -1, female = female);
+    }

 let($show_threads = true)
    threads();
--- a/utils/core/teardrops.scad
+++ b/utils/core/teardrops.scad
@@ -20,17 +20,32 @@
 //
 //! For making horizontal holes that don't need support material.
 //! Small holes can get away without it, but they print better with truncated teardrops.
+//!
+//! Using teardrop_plus() or setting the plus option on other modules will elongate the teardrop vertically by the layer height, so when sliced the staircase tips
+//! do not intrude into the circle. See <https://hydraraptor.blogspot.com/2020/07/horiholes-2.html>
 //
-module teardrop(h, r, center = true, truncate = true, chamfer = 0) { //! For making horizontal holes that don't need support material, set ```truncate = false``` to make traditional RepRap teardrops that don't even need bridging
+module teardrop(h, r, center = true, truncate = true, chamfer = 0, plus = false) { //! For making horizontal holes that don't need support material, set ```truncate = false``` to make traditional RepRap teardrops that don't even need bridging
    module teardrop_2d(r, truncate) {
-        hull() {
-            circle4n(r);
-            if(truncate)
-                translate([0, r / 2])
-                    square([2 * r * (sqrt(2) - 1), r], center = true);
-            else
-                polygon([[0, 0], [eps, 0], [0, r * sqrt(2)]]);
-        }
+        er = layer_height / 2 - eps;    // Extrustion edge radius
+        R = plus ? r + er : r;          // Corrected radius
+        offset = plus ? -er : 0;        // Offset inwards
+        hull()
+            for(side = [0 : 1])
+                mirror([side, 0, 0])
+                    intersection() {
+                        hull()
+                        translate([offset, 0]) {
+                            circle4n(R);
+
+                            if(truncate)
+                                translate([0, R / 2])
+                                    square([2 * R * (sqrt(2) - 1), R], center = true);
+                            else
+                                polygon([[0, 0], [eps, 0], [0, R * sqrt(2)]]);
+                        }
+                        translate([0, -2 * R])
+                            square([R, 4 * R]);
+                    }
    }

    render(convexity = 5)
@@ -40,23 +55,23 @@ module teardrop(h, r, center = true, truncate = true, chamfer = 0) { //! For mak
    teardrop_chamfer(h, center, chamfer) {
        linear_extrude(eps, center = true)
            teardrop_2d(r + chamfer / 2, truncate);
+
        translate_z(-chamfer / 2)
            linear_extrude(eps, center = true)
                teardrop_2d(r, truncate);
    }
 }

-module semi_teardrop(h, r, d = undef, center = true, chamfer = 0) { //! A semi teardrop in the positive Y domain
-    module semi_teardrop_2d(r, d) {
+module semi_teardrop(h, r, d = undef, center = true, chamfer = 0, plus = false) { //! A semi teardrop in the positive Y domain
+    module semi_teardrop_2d(r, d)
        intersection() {
            R = is_undef(d) ? r : d / 2;
-            teardrop(r = R, h = 0);
+            teardrop(r = R, h = 0, plus = plus);

            sq = R + 1;
            translate([-sq, 0])
                square([2 * sq, sq]);
        }
-    }

    render(convexity = 5)
        extrude_if(h, center)
@@ -65,22 +80,21 @@ module semi_teardrop(h, r, d = undef, center = true, chamfer = 0) { //! A semi t
    teardrop_chamfer(h, center, chamfer) {
        linear_extrude(eps, center = true)
            semi_teardrop_2d(r + chamfer / 2, d);
+
        translate_z(-chamfer / 2)
            linear_extrude(eps, center = true)
                semi_teardrop_2d(r, d);
    }
 }

-module teardrop_plus(h, r, center = true, truncate = true, chamfer = 0) //! Slightly bigger teardrop to allow for the 3D printing staircase effect
-    teardrop(h, r + layer_height / 4, center, truncate, chamfer);
+module teardrop_plus(h, r, center = true, truncate = true, chamfer = 0) //! Slightly elongated teardrop to allow for the 3D printing staircase effect
+    teardrop(h, r, center, truncate, chamfer, plus = true);

-module tearslot(h, r, w, center = true, chamfer = 0) { //! A horizontal slot that doesn't need support material
-    module tearslot_2d(r, w) {
-        hull() {
-            translate([-w / 2, 0]) teardrop(r = r, h = 0);
-            translate([w / 2, 0]) teardrop(r = r, h = 0);
-        }
-    }
+module tearslot(h, r, w, center = true, chamfer = 0, plus = false) { //! A horizontal slot that doesn't need support material
+    module tearslot_2d(r, w)
+        hull()
+            for(x = [-1, 1])
+                translate([x * w / 2, 0]) teardrop(r = r, h = 0, plus = plus);

    extrude_if(h, center)
        tearslot_2d(r, w);
@@ -88,19 +102,19 @@ module tearslot(h, r, w, center = true, chamfer = 0) { //! A horizontal slot tha
    teardrop_chamfer(h, center, chamfer) {
        linear_extrude(eps, center = true)
            tearslot_2d(r + chamfer / 2, w);
+
        translate_z(-chamfer / 2)
            linear_extrude(eps, center = true)
                tearslot_2d(r, w);
    }
 }

-module vertical_tearslot(h, r, l, center = true, chamfer = 0) { //! A vertical slot that doesn't need support material
-    module vertical_tearslot_2d(r, l) {
-        hull() {
-            translate([0,  l / 2]) teardrop(0, r, true);
-            translate([0, -l / 2]) circle4n(r);
-        }
-    }
+module vertical_tearslot(h, r, l, center = true, chamfer = 0, plus = false) { //! A vertical slot that doesn't need support material
+    module vertical_tearslot_2d(r, l)
+        hull()
+            for(y = [-1, 1])
+                translate([0,  y * l / 2])
+                    teardrop(0, r, true, plus = plus);

    extrude_if(h, center)
        vertical_tearslot_2d(r, l);
@@ -108,6 +122,7 @@ module vertical_tearslot(h, r, l, center = true, chamfer = 0) { //! A vertical s
    teardrop_chamfer(h, center, chamfer) {
        linear_extrude(eps, center = true)
            vertical_tearslot_2d(r + chamfer / 2, l);
+
        translate_z(-chamfer / 2)
            linear_extrude(eps, center = true)
                vertical_tearslot_2d(r, l);
@@ -123,4 +138,3 @@ module teardrop_chamfer(h, center, chamfer) { //! Helper module for adding chamf
                        hull()
                            children();
 }
-
--- a/utils/gears.scad
+++ b/utils/gears.scad
@@ -21,6 +21,7 @@
 //! Utilities for making involute gears.
 //!
 //! Formulas from <https://khkgears.net/new/gear_knowledge/gear_technical_reference/involute_gear_profile.html>
+//! <https://khkgears.net/new/gear_knowledge/gear_technical_reference/calculation_gear_dimensions.html>
 //! and <https://www.tec-science.com/mechanical-power-transmission/involute-gear/calculation-of-involute-gears/>
 //!
 //! ```involute_gear_profile()``` returns a polygon that can have the bore and spokes, etc, subtracted from it before linear extruding it to 3D.
@@ -30,18 +31,25 @@
 //! the practical minimum.
 //!
 //! The clearance between tip and root defaults to module / 6, but can be overridden by setting the ```clearance``` parameter.
+//!
+//! The origin of the rack is the left end of the pitch line and its width is below the pitch line. I.e. it does not include the addendum.
+//!
+//! ```involute_worm_profile()``` returns a tooth profile that can be passed to ```thread()``` to make worms.
 //
 include <core/core.scad>
 use <maths.scad>

 function involute(r, u) = let(a = degrees(u), c = cos(a), s = sin(a)) r * [c + u * s, s - u * c]; //! Involute of circle radius r at angle u in radians

-function profile_shift(z, pa) = max(1 - z * sqr(sin(pa)) / 2, 0); //! Calculate profile shift for small gears
+function profile_shift(z, pa) = z ? max(1 - z * sqr(sin(pa)) / 2, 0) : 0; //! Calculate profile shift for small gears

-function centre_distance(m, z1, z2, pa) = //! Calculate distance between centres taking profile shift into account
+function centre_distance(m, z1, z2, pa = 20) = //! Calculate distance between centres taking profile shift into account
    let(x1 = profile_shift(z1, pa), x2 = profile_shift(z2, pa)) m * (z1/2 + z2/2 + x1 + x2);

-module involute_gear_profile(m, z, pa = 20, clearance = undef, steps = 20) { //! Calculate profile given module, number of teeth and pressure angle
+function involute_gear_od(m, z, pa = 20) = //! involute gear outside diameter given modulus, tooth count and pressure angle
+    m * (z + 2 * profile_shift(z, pa) + 2);
+
+module involute_gear_profile(m, z, pa = 20, clearance = undef, steps = 20) { //! Calculate gear profile given module, number of teeth and pressure angle
    assert(z >= 7, "Gears must have at least 7 teeth.");
    d = m * z;                                                  // Reference pitch circle diameter
    x = profile_shift(z, pa);                                   // Profile shift
@@ -60,7 +68,7 @@ module involute_gear_profile(m, z, pa = 20, clearance = undef, steps = 20) { //!
    base_r = base_d / 2;
    p1 = involute(base_r, 0);
    p2 = involute(base_r, umax);
-    dist = norm(p2 - p1);                                        // distance between beginning and end of the involute curve
+    dist = norm(p2 - p1);                                       // distance between beginning and end of the involute curve

    base_angle = 2 * acos((sqr(base_r) + sqr(tip_d / 2) - sqr(dist)) / base_r / tip_d) + degrees(2 * ta);
    root_angle = 360 / z - base_angle;
@@ -94,3 +102,37 @@ module involute_gear_profile(m, z, pa = 20, clearance = undef, steps = 20) { //!
            circle(root_r);
        }
 }
+
+function involute_rack_tooth_profile(m, pa = 20, clearance = undef) = //! Calculate rack tooth profile given module and pressure angle
+    let(p = PI * m,                                     // Pitch
+        ha = m,                                         // Addendum
+        c = is_undef(clearance) ? m / 4 : clearance,    // Tip root clearance
+        hf = m + c,                                     // Dedendum
+        hw = 2 * m,                                     // Working depth
+        h = ha + hf,                                    // Tooth depth
+        crest_w = p / 2 - 2 * ha * tan(pa),             // Crest width
+        base_w = crest_w + 2 * hw * tan(pa),            // Base width
+        root_w = p - base_w,                            // Root width
+        clearance_w = root_w - 2 * c * tan(pa),         // Width of clearance without fillet
+        kx = tan(pa / 2 + 45),                          // Fillet ratio of radius and xoffset
+        pf = min(0.38 * m, kx * clearance_w / 2),       // Dedendum fillet radius
+        x = pf / kx,                                    // Fillet centre x offset from corner
+        sides = ceil(r2sides(pf) * (90 - pa) / 360),    // Fillet facets taking $fa, $fs and $fn into account
+        fillet = [ for(i = [0 : sides - 1], a = i * (90 - pa) / sides + 270) [clearance_w / 2 - x,  -hf + pf] + pf * [cos(a), sin(a)] ],
+        reflection = reverse([for(pt = fillet) [p - pt.x, pt.y] ]) // reflect for trailing edge
+    ) concat(fillet, [ [root_w / 2, -hw / 2], [p / 2 - crest_w / 2, ha], [p / 2 + crest_w / 2, ha], [p - root_w / 2, -hw / 2] ], reflection);
+
+module involute_rack_profile(m, z, w, pa = 20, clearance = undef) { //! Calculate rack profile given module, number of teeth and pressure angle
+    p = PI * m;                                     // Pitch
+    hf = 1.25 * m;                                  // Dedendum
+    tooth = involute_rack_tooth_profile(m, pa, clearance);
+    teeth = [for(i = [0 : z - 1], pt = tooth) [pt.x + i * p, pt.y] ];
+
+    polygon(concat([[0, -w], [0, -hf]], teeth, [[z * p, -hf ], [z * p, -w]])); // Add the corners
+}
+
+function involute_worm_profile(m, pa = 20, clearance = undef) = //! Calculate worm profile suitable for passing to thread()
+    let(tooth = involute_rack_tooth_profile(m),
+        pitch = PI * m,
+        y_min = min([for(p = tooth) p.y])
+    ) [for(p = tooth) [p.x - pitch / 2, p.y - y_min, 0]];   // Offset to be positive in y, centred in x and add 0 z ordintate
--- a/utils/horiholes.scad
+++ b/utils/horiholes.scad
@@ -0,0 +1,55 @@
+//
+// NopSCADlib Copyright Chris Palmer 2020
+// 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/>.
+//
+
+//
+//! Utilities for depicting the staircase slicing of horizontal holes made with [`teardrop_plus()`](#teardrops), see <https://hydraraptor.blogspot.com/2020/07/horiholes-2.html>
+//
+include <../utils/core/core.scad>
+
+function teardrop_plus_x(r, y, h) = //! Calculate the ordinate of a compensated teardrop given y and layer height.
+    let(fr = h / 2,
+        hpot = r + fr,
+        x2 = sqr(hpot) - sqr(y),
+        x = x2 > 0 ? sqrt(x2) : 0
+    )
+    max(0,
+        y < hpot / sqrt(2) ? x - fr :
+        y < hpot           ? hpot * sqrt(2) - y - fr :
+        0);
+
+module horihole(r, z, h = 0, center = true) { //! For making horizontal holes that don't need support material and are correct dimensions
+    bot_layer = floor((z - r) / layer_height);
+    top_layer = ceil((z + r) / layer_height);
+    render(convexity = 5)
+        extrude_if(h, center)
+            for(i = [bot_layer : top_layer]) {
+                Z = i * layer_height;
+                y = Z - z + layer_height / 2;
+                x = teardrop_plus_x(r, y, layer_height);
+                if(x > 0)
+                    translate([0, y])
+                        difference() {
+                            square([2 * x + layer_height, layer_height], center = true);
+
+                            for(end = [-1, 1])
+                                translate([end * (x + layer_height / 2), 0])
+                                    circle(d = layer_height, $fn = 32);
+                        }
+             }
+}
--- a/utils/thread.scad
+++ b/utils/thread.scad
@@ -26,6 +26,8 @@
 //! Threads are by default solid, so the male version is wrapped around a cylinder and the female inside a tube. This can be suppressed to just get the helix, for
 //! example to make a printed pot with a screw top lid.
 //!
+//! A left hand thread can be made by using mirror([0,1]).
+//!
 //! Threads with a typical 60 degree angle appear too bright with OpenSCAD's primitive lighting model as they face towards the lights more than the top and sides of
 //! a cylinder. To get around this a colour can be passed to thread that is used to colour the cylinder and then toned down to colour the helix.
 //!
@@ -47,7 +49,7 @@ function thread_profile(h, crest, angle, overlap = 0.1) = //! Create thread prof
    let(base = crest + 2 * (h + overlap) * tan(angle / 2))
        [[-base / 2, -overlap, 0], [-crest / 2, h, 0], [crest / 2, h, 0], [base / 2, -overlap, 0]];

-module thread(dia, pitch, length, profile, center = true, top = -1, bot = -1, starts = 1, solid = true, female = false, colour = undef) { //! Create male or femail thread, ends can be tapered, chamfered or square
+module thread(dia, pitch, length, profile, center = true, top = -1, bot = -1, starts = 1, solid = true, female = false, colour = undef) { //! Create male or female thread, ends can be tapered, chamfered or square
    //
    // Apply colour if defined
    //
@@ -61,10 +63,12 @@ module thread(dia, pitch, length, profile, center = true, top = -1, bot = -1, st
    // Extract some properties from the profile, perhaps they should be stored in it.
    //
    h = max([for(p = sprofile) p.y]);
-    maxx = max([for(p = sprofile) p.x]);
-    minx = min([for(p = sprofile) p.x]);
-    crest_xmax = max([for(p = sprofile) if(p.x != maxx) p.x]);
-    crest_xmin = min([for(p = sprofile) if(p.x != minx) p.x]);
+    xs = [for(p = sprofile) p.x];
+    maxx = max(xs);
+    minx = min(xs);
+    crest_xs = [for(p = sprofile) if(p.y == h) p.x];
+    crest_xmax = max(crest_xs);
+    crest_xmin = min(crest_xs);
    //
    // If the ends don't taper we need an extra half turn past the ends to be cropped horizontally.
    //
@@ -129,11 +133,13 @@ module thread(dia, pitch, length, profile, center = true, top = -1, bot = -1, st
                    render() intersection() {
                        polyhedron(points, ends_faces);

-                        len = length - 2 * eps;
+                        shorten = !is_undef(colour);
+                        len = shorten ? length - 2 * eps : length;
+                        offset = shorten ? eps : 0;
                        rotate_extrude()
                            if(female) {
                                difference() {
-                                    translate([0, eps])
+                                    translate([0, offset])
                                        square([r + h + overlap, len]);

                                    if(top_chamfer_h)
@@ -146,7 +152,7 @@ module thread(dia, pitch, length, profile, center = true, top = -1, bot = -1, st
                            else
                                difference() {
                                    hull() {
-                                        translate([0, eps])
+                                        translate([0, offset])
                                            square([r, len]);

                                        translate([0, bot_chamfer_h])
--- a/vitamins/wire.scad
+++ b/vitamins/wire.scad
@@ -50,7 +50,7 @@ module mouse_hole(cable, h = 100, teardrop = false) { //! A mouse hole to allow
    r = wire_hole_radius(cable);

        if(teardrop)
-            vertical_tearslot(r = r, l = 2 * r, h = h);
+            vertical_tearslot(r = r, l = 2 * r, h = h, plus = true);
        else
            rotate(90)
                slot(r, 2 * r, h = h);
Author	SHA1	Message	Date
Chris Palmer	fb41f218fe	Added involute_gear_od() function.	2020-07-28 21:24:01 +01:00
Chris Palmer	e6a26bc7b1	Changed some teardrop holes to teardrop plus.	2020-07-20 20:39:01 +01:00
Chris Palmer	cb4fa40643	Reimplemented teardrop_plus() again.	2020-07-20 16:55:55 +01:00
Chris Palmer	6a26903514	Added blog links for horiholes.	2020-07-18 23:53:15 +01:00
Chris Palmer	d08d949887	Corrected teardrop_plus() shape to be an accurate compensation for slicer staircasing and added a plus option to tearslot(), etc. Added horiholes.scad to depict staircase holes.	2020-07-18 19:28:26 +01:00
Chris Palmer	574a73e527	More spelling	2020-07-14 23:39:36 +01:00
Chris Palmer	87a35126de	Spelling.	2020-07-14 09:48:30 +01:00
Chris Palmer	1ca485b66b	Added involute_worm_profile() and involute_rack_tooth_profile() functions.	2020-07-14 09:47:45 +01:00
Chris Palmer	bc919529d3	Tweaks to thread. Better thread crest detection. No longer shrtens thread by eps (to avoid z fight) if all one colour. Comment about left hand threads.	2020-07-14 09:42:32 +01:00
Chris Palmer	9f4ed2b915	Fixed capitalisation of Swiss_clips.scad.	2020-07-12 00:27:26 +01:00
Chris Palmer	7ce055373a	Add rack to mesh with involute spur gears.	2020-07-07 22:36:34 +01:00