chair-spring.scad

   1 infty = 100;
   2 eps = 0.01;
   3
   4 wall = 2;
   5 spring_y = 23.8;
   6 spring_x = 8;
   7 spring_z = 8.5;
   8
   9 spring_low = 1.2; // mm lower than spring_x
  10
  11 clip_add_z = 5;
  12 clip_w = 15;
  13
  14 // bottom
  15 translate([0, -spring_y/2, 0]) cube([wall, spring_y, spring_z]);
  16
  17 // sides
  18 for (i = [-1,1]) scale([1, i, 1])
  19         translate([0, spring_y/2 - wall, 0])
  20                 cube([spring_x, wall, spring_z]);
  21
  22 // clip
  23 translate([0, -clip_w/2, 0]) cube([wall, clip_w, spring_z + clip_add_z]);
  24
  25 spring_top_r = 9;
  26 spring_y_off = spring_y/4;
  27
  28 difference() {
  29         union() {
  30                 // center beam
  31                 translate([spring_x - wall, -spring_y/2, 0])
  32                         cube([wall, spring_y, spring_z]);
  33                 // round bottom of the spring
  34                 for (i = [-1,1])
  35                         translate([spring_top_r+spring_x- wall- spring_low,
  36                                 i*spring_y_off, 0])
  37                                 cylinder(r = spring_top_r, h = spring_z,
  38                                         $fn = 128);
  39         }
  40         // top of the spring
  41         difference() {
  42                 translate([spring_x, -infty/2, -infty/2]) cube(infty);
  43                 translate([spring_x - 1, 0, -eps]) scale([0.8, 1, 1]) cylinder(r = 2.5, h = spring_z + 2*eps, $fn = 128);
  44         }
  45
  46         // sides
  47         for (i = [-1, 1]) scale([1, i, 1])
  48         translate([-infty/2, spring_y/2, -infty/2]) cube(infty);
  49
  50         // round top of the spring
  51         for (i = [-1,1])
  52                 translate([spring_top_r+spring_x- wall- spring_low,
  53                         i*spring_y_off, -eps])
  54                         cylinder(r = spring_top_r - wall, h = spring_z + 2*eps,
  55                                         $fn = 128);
  56 }
  57
  58 // color("red") translate([23.5, 0, 0]) cylinder(r = 18, h = spring_z);