scad/MCAD/screw.scad

   1 // Parametric screw-like things (ball screws, augers)
   2 // License: GNU LGPL 2.1 or later.
   3 // © 2010 by Elmo Mäntynen
   4
   5 include <curves.scad>
   6
   7 /* common screw parameter
   8 length
   9 pitch = length/rotations: the distance between the turns of the thread
  10 outside_diameter
  11 inner_diameter: thickness of the shaft
  12 */
  13
  14 //Uncomment to see examples
  15 //test_auger();
  16 //test_ball_groove();
  17 //test_ball_groove2();
  18 //test_ball_screw();
  19
  20 module helix(pitch, length, slices=500){
  21     rotations = length/pitch;
  22     linear_extrude(height=length, center=false, convexity=10, twist=360*rotations, slices=slices, $fn=100)
  23         child(0);
  24 }
  25
  26 module auger(pitch, length, outside_radius, inner_radius, taper_ratio = 0.25) {
  27     union(){
  28         helix(pitch, length)
  29         polygon(points=[[0,inner_radius],[outside_radius,(inner_radius * taper_ratio)],[outside_radius,(inner_radius * -1 * taper_ratio)],[0,(-1 * inner_radius)]], paths=[[0,1,2,3]]);
  30         cylinder(h=length, r=inner_radius);
  31     }
  32 }
  33
  34 module test_auger(){translate([50, 0, 0]) auger(40, 80, 25, 5);}
  35
  36
  37 module ball_groove(pitch, length, diameter, ball_radius=10) {
  38     helix(pitch, length, slices=100)
  39         translate([diameter, 0, 0])
  40         circle(r = ball_radius);
  41 }
  42
  43 module test_ball_groove(){ translate([0, 300, 0]) ball_groove(100, 300, 10);}
  44
  45 module ball_groove2(pitch, length, diameter, ball_radius, slices=200){
  46     rotations = length/pitch;
  47     radius=diameter/2;
  48     offset = length/slices;
  49     union(){
  50         for (i = [0:slices]) {
  51             assign (z = i*offset){
  52                 translate(helix_curve(pitch, radius, z)) sphere(ball_radius, $fa=5, $fs=1);
  53             }
  54         }
  55     }
  56 }
  57
  58 module test_ball_groove2(){translate([0, 0, 0]) ball_groove2(100, 300, 100, 10);}
  59
  60 module ball_screw(pitch, length, bearing_radius=2) {
  61
  62 }
  63
  64 module test_ball_screw(){}