Clamp-on kitchen roll holder for a caravan worktop

// A kitchen roll holder that clamps onto the edge of a worktop, made for a caravan
// kitchenette. Two identical clamp brackets with a thumb-screw bolt on top; two plugs in
// the roll core drop into open-top slots. Built from straight rectangles; corners and
// edges are polished afterwards as a final step, never as part of the construction.
// Uses threads.scad by Ryan A. Colyer, released with CC0 into the public domain.
// Published on RemixCAD as remixcad/threads.
use <remixcad/threads/threads.scad>

/* [Parts] */
// Render the assembly, or one part laid down for printing.
part = "assembly"; // [assembly, bracket, bolt, plug]

/* [Worktop] */
// Thickness of the worktop at the edge, including any lip hanging down.
worktop_thickness = 30; // [10:1:60]
// How far the jaws reach over and under the worktop.
grip_depth = 30; // [18:1:80]
// Height of the hook at the end of the bottom jaw, to grab behind a rail or lip. Zero removes it.
hook_height = 0; // [0:1:30]

/* [Roll] */
// Largest diameter of a full kitchen roll.
roll_diameter = 130; // [90:5:180]

/* [Colour] */
// Colour the printed parts are shown in. Display only, the STL carries no colour.
color_print = "SteelBlue"; // [SteelBlue, White, Gainsboro, Silver, DimGray, Black, SlateGray, FireBrick, ForestGreen, Goldenrod]

/* [Hidden] */
T = worktop_thickness;
width = 22;          // bracket width along the edge, the print height
back = 10;           // upright in front of the edge
jaw = 10;            // top jaw, carries the thread
foot = 6;            // bottom jaw, thin so it fits over a cabinet
hook_t = 5;          // hook thickness
slack = 3;           // spare jaw opening, taken up by the bolt
bolt_size = 10;      // M10
tolerance = 0.5;     // taken off the thread for printing
knob_d = 28;
knob_h = 8;
pad_h = 2;

pin_d = 10;          // pin on the plug
pin_fit = 0.6;
under = 10;          // material under the pin
lip = 8;             // lip in front of the slot
rise = 8;            // arm height above the top of the pin
funnel = 3;          // funnel at the slot entry
edge_gap = 10;       // room between a full roll and the worktop edge

plug_d = 36;         // nose of the plug, fits any core
plug_tip_d = 32;
plug_len = 28;
flange_d = 52;
flange_t = 2;

round_r = 2;         // profile corner polish
chamfer = 1.2;       // face edge polish
smoothness = 48;

// Preview only.
roll_length = 230;
core_d = 42;

gap = T + hook_height + slack;
top0 = hook_height + slack;          // underside of the top jaw, worktop surface at z = 0
bolt_x = grip_depth / 2;
bolt_len = jaw + hook_height + slack + 6;

slot_w = pin_d + pin_fit;
arm_h = under + pin_d + rise;
seat_x = -(roll_diameter / 2 + edge_gap);
reach = -seat_x + slot_w / 2 + lip;
arm_z0 = -roll_diameter / 2 - slot_w / 2 - under;
pin_z = arm_z0 + under + slot_w / 2;
up_z0 = min(arm_z0, -T - foot);

shoulder_h = (flange_d - plug_d) / 2;
pin_len = width + 8;
plug_h = plug_len + shoulder_h + flange_t + pin_len;
// Where a typical core lands on the 45 degree shoulder.
contact_z = plug_len + (core_d - plug_d) / 2;
flange_out = plug_len + shoulder_h + flange_t;
bracket_y = roll_length / 2 - contact_z + flange_out + 1 + width / 2;

echo(str("Bracket: ", reach + grip_depth, " x ", top0 + jaw - up_z0, " x ", width, " mm"));

// The polish: a closing pass rounds the concave corners, an opening pass the convex
// ones. Applied over the finished straight shape, never during it.
module polish2d(r) {
  if (r > 0)
    offset(r = r, $fn = smoothness)
      offset(r = -2 * r, $fn = smoothness)
        offset(r = r, $fn = smoothness)
          children();
  else
    children();
}

// Extrude with a 45 degree chamfer on both faces, built from thin slices so it stays
// fast. One slice per 0.2 mm, the same as a print layer.
module polish_extrude(h, c) {
  if (c > 0) {
    n = ceil(c / 0.2);
    s = c / n;
    translate([0, 0, c]) linear_extrude(height = h - 2 * c) children();
    for (i = [0 : n - 1]) {
      inset = c - (i + 0.5) * s;
      translate([0, 0, i * s])
        linear_extrude(height = s + 0.001) offset(delta = -inset) children();
      translate([0, 0, h - (i + 1) * s - 0.001])
        linear_extrude(height = s + 0.001) offset(delta = -inset) children();
    }
  } else {
    linear_extrude(height = h) children();
  }
}

// ---- Bracket ----
// One 2D profile of axis-aligned squares, in the XZ plane.
// Origin: the worktop surface at z = 0, its edge at x = 0, the worktop toward +x.

module profile_raw() {
  // Upright, in front of the worktop edge.
  translate([-back, up_z0]) square([back, top0 + jaw - up_z0]);
  // Top jaw, carries the clamping bolt.
  translate([-1, top0]) square([grip_depth + 1, jaw]);
  // Bottom jaw, pulled up against the underside.
  translate([-1, -T - foot]) square([grip_depth + 1, foot]);
  // Hook, grabs behind a rail or lip under the worktop.
  if (hook_height > 0)
    translate([grip_depth - hook_t, -T - 1]) square([hook_t, hook_height + 1]);
  // Arm in front of the edge, with the open-top slot for the plug pin.
  difference() {
    translate([-reach, arm_z0]) square([reach, arm_h]);
    translate([seat_x, pin_z]) {
      circle(d = slot_w, $fn = smoothness);
      translate([-slot_w / 2, 0]) square([slot_w, arm_h]);
    }
    translate([seat_x, arm_z0 + arm_h])
      polygon([[-slot_w / 2 - funnel, 1], [slot_w / 2 + funnel, 1],
               [slot_w / 2 + funnel, 0], [slot_w / 2, -funnel],
               [-slot_w / 2, -funnel], [-slot_w / 2 - funnel, 0]]);
  }
}

module profile() {
  polish2d(round_r) profile_raw();
}

module bracket_body() {
  translate([0, width / 2, 0])
    rotate([90, 0, 0])
      polish_extrude(width, chamfer) profile();
}

module bracket() {
  // The clamp thread is cut straight into the top jaw.
  ScrewHole(bolt_size, jaw + 2, [bolt_x, 0, top0 - 1], [0, 0, 0],
            tolerance = tolerance)
    bracket_body();
}

// ---- Clamp bolt ----
// An octagonal knob, the thread, and a flat tip narrower than the thread so the bolt
// can be screwed through the jaw. Modelled knob down, the way it prints.

module clamp_bolt() {
  polish_extrude(knob_h, chamfer) polish2d(2) circle(d = knob_d, $fn = 8);
  translate([0, 0, knob_h - 0.01])
    ScrewThread(bolt_size, bolt_len, tolerance = tolerance);
  translate([0, 0, knob_h + bolt_len - 0.01])
    cylinder(d = bolt_size - 3, h = pad_h, $fn = smoothness);
}

// ---- Core plug ----
// A nose that fits any core, a 45 degree shoulder that centres the core, a flange and
// the pin that drops into the slot. Modelled nose down, the way it prints.

module plug() {
  c = 1;
  z1 = plug_len;
  z2 = z1 + shoulder_h;
  z3 = z2 + flange_t;
  rotate_extrude($fn = smoothness)
    polygon([[0, 0], [plug_tip_d / 2, 0], [plug_d / 2, z1], [flange_d / 2, z2],
             [flange_d / 2, z3], [pin_d / 2, z3], [pin_d / 2, plug_h - c],
             [pin_d / 2 - c, plug_h], [0, plug_h]]);
}

// ---- Preview only: worktop and roll ----

module worktop() {
  w = 2 * bracket_y + 120;
  if (hook_height > 0) {
    // A lip at the edge, the worktop thinner behind it.
    translate([0, -w / 2, -T]) cube([grip_depth - hook_t - 1, w, T]);
    thin = max(4, T - hook_height - 1);
    translate([0, -w / 2, -thin]) cube([grip_depth + 90, w, thin]);
  } else {
    translate([0, -w / 2, -T]) cube([grip_depth + 90, w, T]);
  }
}

module roll() {
  translate([seat_x, roll_length / 2, pin_z]) rotate([90, 0, 0])
    difference() {
      cylinder(d = roll_diameter, h = roll_length, $fn = smoothness);
      translate([0, 0, -1]) cylinder(d = core_d, h = roll_length + 2, $fn = smoothness);
    }
}

// ---- Layout ----

if (part == "bracket") {
  // On its side, ready to print. Print it twice, left and right are the same.
  color(color_print) translate([0, 0, width / 2]) rotate([90, 0, 0]) bracket();
} else if (part == "bolt") {
  color(color_print) clamp_bolt();
} else if (part == "plug") {
  color(color_print) plug();
} else {
  color("BurlyWood") worktop();
  color("WhiteSmoke") roll();
  for (s = [-1, 1]) {
    color(color_print) translate([0, s * bracket_y, 0]) bracket();
    // Bolt from the top, its tip on the worktop.
    color("DimGray") translate([bolt_x, s * bracket_y, knob_h + bolt_len + pad_h])
      rotate([180, 0, 0]) clamp_bolt();
  }
  color("DimGray") translate([seat_x, roll_length / 2 - contact_z, pin_z])
    rotate([-90, 0, 0]) plug();
  color("DimGray") translate([seat_x, -(roll_length / 2 - contact_z), pin_z])
    rotate([90, 0, 0]) plug();
}