Origami MagSafe wallet and phone stand, folded from one flat print

// A MagSafe card wallet printed as one flat sheet a few layers high and folded like a
// paper kit: a card pocket, a note pocket, a seat for a magnet ring and an outer flap
// that pops into a triangle as a phone stand. Every fold goes toward the top of the
// print, so the bed side becomes the outside. No glue, no loose parts.

/* [Wallet] */
// Number of cards it should hold.
cards = 4; // [2:1:5]
// Room for folded bank notes, in mm.
cash_room = 1; // [0:0.5:2]
// Outer diameter of the stick-on MagSafe ring.
magnet_diameter = 56; // [50:0.5:60]

/* [Print] */
// Thickness of the panels. Three layers of 0.2.
panel_thickness = 0.6; // [0.4:0.1:1]
// Thickness of the fold lines. Two layers of 0.2.
fold_thickness = 0.4; // [0.2:0.02:0.6]
// Room around a card, per side.
card_play = 1; // [0.5:0.25:2]

/* [Preview] */
// 0 is the flat sheet you print. 100 shows it folded.
fold = 0; // [0:5:100]
// Pops the flap into a phone stand. Works when fold is 100.
stand = 0; // [0:10:100]

/* [Colour] */
// Display only, the STL carries no colour.
color_wallet = "SteelBlue"; // [SteelBlue, Silver, Gainsboro, White, DimGray, Black, SlateGray, FireBrick, ForestGreen, Goldenrod]

/* [Hidden] */
$fn = 64;
card_long = 85.6;
card_short = 54;
card_t = 0.76;
bed = 174;                 // what we allow ourselves of a 180 mm bed

t = panel_thickness;
ft = min(fold_thickness, t);
flex = min(0.2, ft);       // folds that bend every day: one layer

W = max(card_short + 2 * card_play, magnet_diameter + 2);   // back panel, upright
H = card_long + 1;
Wc = W - 1.5;              // front panel, clear of the side fold
inner = cards * card_t + cash_room + 2 * t;   // cards, divider, notes, tab heads
s_bc = inner + 2 * t;      // fold between back and front
s_left = s_bc + t;         // side flap, around the front panel as well
s_bot = s_bc + 2 * t + 0.3;   // stand flap, around the side flap too
s_cd = cash_room + 3 * t;  // fold between front and divider, around the notes
divider_h = 55;

r = 3;                     // corner radius of the panels
edge = r + 1;              // folds stop this far from a corner
flap_w = 10;
neck_w = 12;
neck_l = 2.5;
head_l = 7;
barb = 2;
tip_w = 4;
slit = t + 0.6;

// Stand flap: leg, crease, leg, hook band, hook.
crease_w = 8;
hook_band = 4;
hook_l = 9;
hook_w = 16;
hook_slit = t + 0.8;
flap_len = min(68, bed - H - s_bot - hook_band - hook_l);
leg = (flap_len - crease_w) / 2;
leg_half_w = 26;
y_closed = flap_len + hook_band / 2;   // slit heights on the front panel
y_stand = [0.58 * flap_len, 0.72 * flap_len];

// Magnet ring, high on the back so the wallet hangs low on the phone.
ring_w = 5;
ring_cy = H - magnet_diameter / 2 - 2.5;

// Triangle of the stand, for the preview.
l1 = leg + crease_w / 2;
l2 = leg + crease_w / 2 + hook_band / 2;
base = y_stand[0];
alpha = acos((l1 * l1 + base * base - l2 * l2) / (2 * l1 * base));
beta = acos((l2 * l2 + base * base - l1 * l1) / (2 * l2 * base));

f = fold / 100;
k = fold >= 100 ? stand / 100 : 0;
A = 90 * f;                 // each fold band turns 90 degrees at both of its edges
D = 20 * f;                 // tabs dive through their slit
hook_turn = (165 + (10 - beta) * k) * f;

xc0 = W / 2 + s_bc;         // where the front panel starts in the flat sheet

echo(str("Flat sheet: ", W + s_left + flap_w + neck_l + head_l + s_bc + Wc, " x ",
  H + s_bot + flap_len + hook_band + hook_l, " mm"));

// ---- 2D helpers ----
module rounded(rad) { offset(r = rad) offset(delta = -rad) children(); }

// A slot with round ends, long side along x.
module slot(l, w) {
  hull() for (s = [-1, 1]) translate([s * (l - w) / 2, 0]) circle(d = w);
}

// ---- Back panel: phone side ----
module back3d() {
  difference() {
    linear_extrude(height = t)
      difference() {
        rounded(r) translate([-W / 2, 0]) square([W, H]);
        // thumb slot inside the ring, to slide the cards up
        translate([0, ring_cy]) rotate(90) slot(36, 16);
      }
    // groove one layer deep on the bed side that centres the magnet ring
    translate([0, ring_cy, -0.01])
      linear_extrude(height = 0.21)
        difference() {
          circle(d = magnet_diameter + 0.6);
          circle(d = magnet_diameter - 2 * ring_w - 0.6);
        }
  }
}

// ---- Front panel and divider, to the right of the back in the flat sheet ----
// A point that ends up at folded x sits at xc0 + W/2 - x in the sheet.
module front2d() {
  difference() {
    rounded(r) translate([xc0, 1]) square([Wc, H - 3]);
    // notch in the top edge to pinch notes and cards
    translate([xc0 + W / 2, H + 1]) circle(r = 10);
    // slits for the two barbed tabs of the side flap
    for (y = tab_y())
      translate([xc0 + W - flap_w - 0.2 - slit / 2, y]) rotate(90) slot(neck_w + 1.5, slit);
    // slits for the hook of the stand flap: closed, and two stand positions
    for (y = concat([y_closed], y_stand))
      translate([xc0 + W / 2, y]) slot(hook_w + 1, hook_slit);
  }
}

module band_bc2d() { translate([W / 2 - 0.05, edge + 1]) square([s_bc + 0.1, H - 3 - 2 * edge]); }

module band_cd2d() { translate([xc0 + edge, 1 - s_cd - 0.05]) square([Wc - 2 * edge, s_cd + 0.1]); }

module divider2d() {
  difference() {
    rounded(r) translate([xc0 + 1, 1 - s_cd - divider_h]) square([Wc - 2, divider_h]);
    // scoop in what becomes the top edge of the divider
    translate([xc0 + W / 2, 1 - s_cd - divider_h - 3]) circle(r = 10);
  }
}

// ---- Side flap, drawn on the right and mirrored to the left ----
function tab_y() = [0.26 * H, 0.74 * H];

module band_side2d() { translate([W / 2 - 0.05, edge]) square([s_left + 0.1, H - 2 * edge]); }

module flap2d() {
  x0 = W / 2 + s_left;
  hull() {
    translate([x0 - 0.01, edge]) square([0.02, H - 2 * edge]);
    for (y = [edge + 6, H - edge - 6]) translate([x0 + flap_w - 2, y]) circle(r = 2);
  }
}

module tab2d(yc) {
  x1 = W / 2 + s_left + flap_w;
  hw = neck_w + 2 * barb;
  translate([x1 - 0.01, yc - neck_w / 2]) square([neck_l + 1, neck_w]);
  hull() {
    for (s = [-1, 1]) translate([x1 + neck_l + 0.75, yc + s * (hw / 2 - 0.75)]) circle(d = 1.5);
    translate([x1 + neck_l + head_l - tip_w / 2, yc]) circle(d = tip_w);
  }
}

// ---- Stand flap, below the back panel ----
module band_bot2d() { translate([-(W / 2 - edge), -s_bot - 0.05]) square([W - 2 * edge, s_bot + 0.1]); }

// One leg between y0 and y0 + len, with two ribs on the print top.
module leg3d(y0, len) {
  linear_extrude(height = t) rounded(2) translate([-leg_half_w, y0]) square([2 * leg_half_w, len]);
  for (x = [-12, 12]) translate([x - 0.8, y0 + 2, t - 0.01]) cube([1.6, len - 4, t]);
}

module strip2d(half_w, y0, len) { translate([-half_w, y0 - 0.05]) square([2 * half_w, len + 0.1]); }

module hook2d(y_top) {
  hull() {
    translate([-hook_w / 2, y_top - 0.02]) square([hook_w, 0.02]);
    for (s = [-1, 1]) translate([s * (hook_w / 2 - 3), y_top - hook_l + 3]) circle(r = 3);
  }
}

// ---- Folding ----
module ext(h) { linear_extrude(height = h) children(); }
// Turn the children around a fold line on the bed: along x at height y, or along y at x.
module hinge_x(y, a) { translate([0, y, 0]) rotate(a = a, v = [1, 0, 0]) translate([0, -y, 0]) children(); }
module hinge_y(x, a) { translate([x, 0, 0]) rotate(a = a, v = [0, 1, 0]) translate([-x, 0, 0]) children(); }

module front_chain() {
  hinge_y(W / 2, -A) {
    ext(ft) band_bc2d();
    hinge_y(xc0, -A) {
      ext(t) front2d();
      hinge_x(1, -A) {
        ext(ft) band_cd2d();
        hinge_x(1 - s_cd, -A) ext(t) divider2d();
      }
    }
  }
}

module side_chain() {
  hinge_y(W / 2, -A) {
    ext(ft) band_side2d();
    hinge_y(W / 2 + s_left, -A) {
      ext(t) flap2d();
      for (y = tab_y()) hinge_y(W / 2 + s_left + flap_w, -D) ext(t) tab2d(y);
    }
  }
}

module stand_chain() {
  y1 = -s_bot;                 // start of the first leg
  y2 = y1 - leg;               // start of the crease
  y3 = y2 - crease_w;          // start of the second leg
  y4 = y1 - flap_len;          // start of the hook band
  y5 = y4 - hook_band;         // start of the hook
  turn = (alpha + beta) * k / 2;
  hinge_x(0, -A) {
    ext(ft) band_bot2d();
    hinge_x(y1, -(A - alpha * k)) {
      leg3d(y2, leg);
      hinge_x(y2, -turn) {
        ext(flex) strip2d(22, y3, crease_w);
        hinge_x(y3, -turn) {
          leg3d(y4, leg);
          hinge_x(y4, -hook_turn / 2) {
            ext(flex) strip2d(hook_w / 2, y5, hook_band);
            hinge_x(y5, -hook_turn / 2) ext(t) hook2d(y5);
          }
        }
      }
    }
  }
}

module wallet() {
  back3d();
  front_chain();
  mirror([1, 0, 0]) side_chain();
  stand_chain();
}

color(color_wallet) wallet();

// Preview only: the magnet ring once folded, the phone once the stand is out.
if (fold > 0)
  color("Goldenrod") translate([0, ring_cy, -0.8])
    linear_extrude(height = 1) difference() {
      circle(d = magnet_diameter);
      circle(d = magnet_diameter - 2 * ring_w);
    }
if (k > 0)
  color("DimGray") translate([-35.5, ring_cy - 80, -8.8])
    linear_extrude(height = 8) rounded(8) square([71, 147]);