Click latch (type 1)

README.md

@@ -35,6 +35,13 @@ For inserting magnets, check out [the jig](#jig).
     - [Glued magnets](#glued-magnets)
     - [Rounded corner frame](#rounded-corner-frame)
     - [Solid frame](#solid-frame)
+  - [Click Latch](#click-latch)
+    - [Length](#length)
+    - [Distance](#distance)
+    - [Latch Strength](#latch-strength)
+    - [Latch Wall Strength](#latch-wall-strength)
+    - [Height](#height)
+    - [Steepness](#steepness)
   - [Half-sized cells](#half-sized-cells)
   - [Corner radius](#corner-radius)
   - [Alignment](#alignment)
@@ -229,6 +236,80 @@ Using the `magnet_frame_style` option, you can change the magnet layer to be ful
 <!-- openscad -o docs/images/magnets-solid.png --camera=0,0,0,40,0,10,200 -D plate_size='[105, 63]' -D magnets=true -D magnet_style=0 -D magnet_frame_style=0 -->
 <img src="docs/images/magnets-solid.png" alt="Solid magnet frame" />
 
+## Click Latch
+
+If you do not wish to use magnets, but still want a more secure fit for your bins, a click latch is an option. A click latch grips the bottom of the bin.
+
+> [!WARNING]
+> When a bin is placed on the baseplate, the click latch is under constant mechanical stress. This causes the plastic to deform over time ("creep"), reducing the grip strength. _PLA is very susceptible to this._ PETG is more resistant, but long-term tests are still scarce, so _consider this feature experimental_.
+
+<!-- openscad -o docs/images/click1.png --camera=0,0,0,40,0,10,200 -D plate_size='[105, 63]' -D click1=true -->
+<img src="docs/images/click1.png" alt="Click latch" />
+
+There are various parameters you can use to tune the click latch mechanism.
+
+### Length
+
+The latch is composed of two arcs at each end, and an optional middle straight section. The total length of the latch is configured using the `click1_outer_length` property:
+
+<!-- openscad -o docs/images/click1-outer-length-20.png --camera=0,0,0,40,0,10,100 -D plate_size='[42, 42]' -D click1=true -D click1_outer_length=20 -->
+<img src="docs/images/click1-outer-length-20.png" alt="Click latch with click1_outer_length=20" />
+
+The length of the straight section is configured using `click1_inner_length`, which is 0 by default (no straight section). Here is an example with a 20mm straight section:
+
+<!-- openscad -o docs/images/click1-inner-length-20.png --camera=0,0,0,40,0,10,100 -D plate_size='[42, 42]' -D click1=true -D click1_inner_length=20 -->
+<img src="docs/images/click1-inner-length-20.png" alt="Click latch with click1_inner_length=20" />
+
+### Distance
+
+The `click1_distance` property changes the distance that the latch protudes into the bin area. A larger distance can increase grip strength, but makes the bin more difficult to place into the baseplate. Zero distance:
+
+<!-- openscad -o docs/images/click1-distance-0.png --camera=0,0,0,40,0,10,100 -D plate_size='[42, 42]' -D click1=true -D click1_distance=0 -->
+<img src="docs/images/click1-distance-0.png" alt="Click latch with click1_distance=0" />
+
+5mm distance (don't do this):
+
+<!-- openscad -o docs/images/click1-distance-5.png --camera=0,0,0,40,0,10,100 -D plate_size='[42, 42]' -D click1=true -D click1_distance=5 -->
+<img src="docs/images/click1-distance-5.png" alt="Click latch with click1_distance=5" />
+
+### Latch Strength
+
+The `click1_strength` property controls the thickness of the latch itself. This is measured from the very bottom of the latch which, if you look at the gridfinity specification, has a chamfer of 0.7mm, so the strength needs to be higher than this to get any reasonable latch height. Here's an example with `click1_strength=2.5` (and `click1_wall_strength=0`, or else there would not be enough space):
+
+<!-- openscad -o docs/images/click1-strength-2.5.png --camera=0,0,0,40,0,10,100 -D plate_size='[42, 42]' -D click1=true -D click1_strength=2.5 -D click1_wall_strength=0 -->
+<img src="docs/images/click1-strength-2.5.png" alt="Click latch with click1_strength=2.5" />
+
+### Latch Wall Strength
+
+The `click1_wall_strength` property controls the thickness of the wall behind the latch. This wall serves two purposes: It adds rigidity to the baseplate, and it prevents the click latch from bending too far. Note that the wall is measured per cell, so if you have two neighbouring cells, the actual wall thickness will be double this value. An example with `click1_wall_strength=2` (and reduced `click1_strength`):
+
+<!-- openscad -o docs/images/click1-wall-strength-2.png --camera=0,0,0,40,0,10,100 -D plate_size='[84, 42]' -D click1=true -D click1_strength=0.8 -D click1_wall_strength=2 -->
+<img src="docs/images/click1-wall-strength-2.png" alt="Click latch with click1_wall_strength=2" />
+
+Setting the wall strength to 0 disables the backing wall entirely:
+
+<!-- openscad -o docs/images/click1-wall-strength-0.png --camera=0,0,0,40,0,10,100 -D plate_size='[84, 42]' -D click1=true -D click1_wall_strength=0 -->
+<img src="docs/images/click1-wall-strength-0.png" alt="Click latch with click1_wall_strength=0" />
+
+### Height
+
+The `click1_height` property controls the height of the latch.
+
+<!-- openscad -o docs/images/click1-height-0.5.png --camera=0,0,0,40,0,10,100 -D plate_size='[42, 42]' -D click1=true -D click1_height=0.5 -->
+<img src="docs/images/click1-height-0.5.png" alt="Click latch with click1_height=0" />
+
+### Steepness
+
+The arcs of the click latch follow a logistic curve, and `click1_steepness` changes the steepness of that curve. Steepness 0.1:
+
+<!-- openscad -o docs/images/click1-steepness-0.1.png --camera=0,0,0,40,0,10,100 -D plate_size='[42, 42]' -D click1=true -D click1_steepness=0.1 -->
+<img src="docs/images/click1-steepness-0.1.png" alt="Click latch with click1_steepness=0.1" />
+
+Steepness 5:
+
+<!-- openscad -o docs/images/click1-steepness-5.png --camera=0,0,0,40,0,10,100 -D plate_size='[42, 42]' -D click1=true -D click1_steepness=5 -->
+<img src="docs/images/click1-steepness-5.png" alt="Click latch with click1_steepness=5" />
+
 ## Half-sized cells
 
 By default, if there isn't enough room for a full cell on the plate, GridFlock will attempt to fill up remaining space with half-sized cells.

editor.toml

@@ -9,7 +9,7 @@ head-extra = '<script defer src="https://um.yawk.at/script.js" data-website-id="
 file = "gridflock.scad"
 description-extra-html = "<br>For detailed documentation, check the <a href='https://github.com/yawkat/GridFlock/blob/main/README.md'>README</a>.<br><b>Feb 16: I've turned off magnets by default because most people don't use them.</b> If you've saved a design with magnets, you will have to manually turn them on again below."
 umami-track-render = []
-umami-track-export = ["magnets", "magnet_style", "connector_intersection_puzzle", "connector_edge_puzzle", "bed_size"]
+umami-track-export = ["magnets", "magnet_style", "connector_intersection_puzzle", "connector_edge_puzzle", "bed_size", "click1"]
 
 [model.param-metadata.bed_size.presets]
 text = "Printer Presets"
@@ -128,6 +128,29 @@ help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#other-inter
 help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#thumb-screw"
 [model.param-metadata.thumbscrew_diameter]
 display-condition = {js = "thumbscrews"}
+[model.param-metadata.click1]
+help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#click-latch"
+[model.param-metadata.click1_distance]
+display-condition = {js = "click1"}
+help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#distance"
+[model.param-metadata.click1_steepness]
+display-condition = {js = "click1"}
+help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#steepness"
+[model.param-metadata.click1_outer_length]
+display-condition = {js = "click1"}
+help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#length"
+[model.param-metadata.click1_inner_length]
+display-condition = {js = "click1"}
+help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#length"
+[model.param-metadata.click1_height]
+display-condition = {js = "click1"}
+help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#height"
+[model.param-metadata.click1_strength]
+display-condition = {js = "click1"}
+help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#latch_strength"
+[model.param-metadata.click1_wall_strength]
+display-condition = {js = "click1"}
+help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#latch_wall_strength"
 [model.param-metadata.x_segment_algorithm]
 help-link = "https://github.com/yawkat/GridFlock/blob/main/README.md#horizontal"
 [model.param-metadata.y_row_count_first]

gridflock.scad

@@ -36,6 +36,25 @@ magnet_top = 0.5; // 0.25
 // Floor below the magnet. Not structurally important, should be small to minimize filament use
 magnet_bottom = 0.75; // 0.25
 
+/* [Click latch (Experimental)] */
+
+// Enable the click latch. WARNING: The plastic can deform over time, do not use PLA! PETG might be fine, but there are no long-term tests yet
+click1 = false;
+// Distance that the click latch extends into the bin area
+click1_distance = 1; // .1
+// Steepness of the click latch arc
+click1_steepness = 1; // .1
+// Length of the full click latch
+click1_outer_length = 30;
+// Length of the straight piece in the middle of the click latch. The arced pieces take up the remaining space
+click1_inner_length = 0;
+// Height of the click latch
+click1_height = 3; // .1
+// Thickness of the click latch. This is measured from the bottom of the baseplate profile
+click1_strength = 1.6; // .1
+// Thickness of the non-bending wall behind the click latch. This wall provides stability and prevents the click latch from bending too far
+click1_wall_strength = 1; // .1
+
 /* [Intersection Puzzle Connector] */
 
 // Enable the intersection puzzle plate connector. This is similar to GridPlates/GRIPS. Small puzzle connectors are added cell intersections.
@@ -134,10 +153,13 @@ edge_adjust = [0, 0, 0, 0];
 // Override the content of individual cells. Each character in this string modifies one cell. The order goes from west to east, then south to north. A 'c' stands for a normal cell. An 's' stands for a solid plate without a cell cutout. An 'e' stands for an empty square
 cell_override = "";
 // Test patterns
-test_pattern = 0; // [0:None, 1:Half, 2:Padding, 3:Numbering, 4:Wall]
+test_pattern = 0; // [0:None, 1:Half, 2:Padding, 3:Numbering, 4:Wall, 5:Click]
 
 /* [Hidden] */
 
+// Resolution of the click latch.
+click1_steps = 15;
+
 _MAGNET_GLUE_TOP = 0;
 _MAGNET_PRESS_FIT = 1;
 _MAGNET_GLUE_BOTTOM = 2;
@@ -245,6 +267,20 @@ module cell(half=[false, false], connector=[false, false, false, false], positiv
                         }
                     }
                 }
+                if (click1) translate([0, 0, _profile_height/2]) {
+                    if (!half.x) cube([click1_outer_length, size.y-click1_wall_strength*2, _profile_height], center=true);
+                    if (!half.y) cube([size.x-click1_wall_strength*2, click1_outer_length, _profile_height], center=true);
+                }
+            }
+            if (click1) {
+                if (!half.x) {
+                    translate([0, -size.y/2, 0]) rotate([90, 0, -90]) do_sweep(_click1_sweep, convexity=4);
+                    translate([0, size.y/2, 0]) rotate([90, 0, 90]) do_sweep(_click1_sweep, convexity=4);
+                }
+                if (!half.y) {
+                    translate([-size.x/2, 0, 0]) rotate([90, 0, 180]) do_sweep(_click1_sweep, convexity=4);
+                    translate([size.x/2, 0, 0]) rotate([90, 0, 0]) do_sweep(_click1_sweep, convexity=4);
+                }
             }
             if (magnets) {
                 translate([0, 0, -_magnet_level_height]) linear_extrude(height = _magnet_level_height) {
@@ -353,6 +389,96 @@ module puzzle_female(positive) {
     }
 }
 
+/**
+ * @Summary Prepare geometry for do_sweep, which sweeps a polygon along a path
+ * @param polygon The polygon to sweep. Array of 2D points
+ * @param path The path to sweep along. Array of 3D points
+ * @return Geometry data to pass to do_sweep
+ */
+function prepare_sweep(polygon, path) = let(
+    ring_faces = function (base_index) [
+            for (i = [0:len(polygon)-1]) [
+                base_index + (i + 1) % len(polygon), 
+                base_index + len(polygon) + (i + 1) % len(polygon), 
+                base_index + len(polygon) + i, 
+                base_index + i
+            ]
+        ],
+    points = [for (pt_path = path) each [for (pt_poly = polygon) pt_path + [pt_poly.x, pt_poly.y, 0]]],
+    first_face = reverse([each [0:len(polygon)-1]]),
+    last_face = [each [len(polygon)*(len(path)-1):len(polygon)*len(path)-1]],
+    faces = [
+        first_face,
+        for (i = [0:len(path)-2]) each ring_faces(i * len(polygon)),
+        last_face
+    ]
+) [points, faces];
+
+/**
+ * @Summary Display a sweep prepared by prepare_sweep
+ * @param sweep The value returned by prepare_sweep
+ */
+module do_sweep(prep, convexity=2) {
+    polyhedron(points = prep[0], faces = prep[1], convexity = convexity);
+}
+
+/**
+ * @Summary Clip a polygon along an edge (one step of the Sutherland-Hodgman algorithm)
+ * @param polygon The input polygon to clip
+ * @param contains A lambda taking a single point that returns whether that point is clipped or not
+ * @param find_intersection A lambda taking a point inside and outside the result area (in that order), that returns the point where the line between those points intersects the start of the clipping region
+ * @return The clipped polygon, potentially with duplicate points
+ */
+function clip_polygon_edge(polygon, contains, find_intersection) = 
+    [for (i = [0:len(polygon)-1]) let (
+        here = polygon[i],
+        prev = i == 0 ? polygon[len(polygon) - 1] : polygon[i - 1],
+        here_inside = contains(here),
+        prev_inside = contains(prev),
+    ) each
+        here_inside ?
+            prev_inside ? [here] : [find_intersection(here, prev), here] :
+            prev_inside ? [find_intersection(prev, here)] : []
+    ];
+
+/**
+ * @Summary Clip a polygon using the Sutherland-Hodgman algorithm so that all resulting points satisfy `pt.x <= max.x && pt.y <= max.y`
+ * @param polygon The polygon to clip
+ * @param max The bounds to clip to
+ * @return The clipped polygon, with no duplicate points
+ */
+function clip_polygon_max(polygon, max) = let(
+    step = function(dimension, pg) clip_polygon_edge(pg, function (pt) pt[dimension] <= max[dimension], function (inside, outside) let (factor = (max[dimension] - inside[dimension]) / (outside[dimension] - inside[dimension])) inside + (outside - inside) * factor),
+    clipped = step(0, step(1, polygon)),
+    deduplicated = [for (i = 0, prev = clipped[len(clipped) - 1]; i < len(clipped); prev = clipped[i], i = i + 1) each clipped[i] == prev ? [] : [clipped[i]]]
+) deduplicated;
+
+// the maximum width of the baseplate profile (at the very bottom of the profile)
+_baseplate_max_strength = _BASEPLATE_PROFILE[3].x;
+// the full polygon of the baseplate profile
+_baseplate_polygon = [
+    [0, 0],
+    for (pt = _BASEPLATE_PROFILE) pt + [-_baseplate_max_strength, 0]
+];
+
+_click1_polygon = let(shiftx = _baseplate_max_strength-click1_strength) [for (pt = clip_polygon_max([for (pt = _baseplate_polygon) [pt.x+shiftx, pt.y]], [0, click1_height])) [pt.x-shiftx, pt.y]];
+/**
+ * @Summary Logistic function used for the click1 arc
+ * @param x coordinate
+ */
+function click1_path_base(x) = 1/(1+exp(-click1_steepness*x));
+_click1_path = let (
+    arc_length = (click1_outer_length - click1_inner_length) / 2,
+    low = click1_path_base(-arc_length/2),
+    high = click1_path_base(arc_length/2),
+    scale = click1_distance / (high - low),
+    arc = [for (x = [-arc_length/2:arc_length/click1_steps:arc_length/2]) [-(click1_path_base(x)-low)*scale, 0, x - (click1_outer_length-arc_length)/2]]
+) [
+    each arc,
+    for (pt = reverse(arc)) [pt.x, pt.y, -pt.z]
+];
+_click1_sweep = prepare_sweep(_click1_polygon, _click1_path);
+
 /**
  * @Summary Get the index of the last cell in a segment
  * @param count The number of cells on each axis
@@ -659,6 +785,11 @@ module chamfer_triangle() {
     polygon([[-extend, -extend], [1 + extend, -extend], [-extend, 1 + extend]]);
 }
 
+function compute_segment_size(count, padding) = [
+    BASEPLATE_DIMENSIONS.x * count.x + padding[_EAST] + padding[_WEST],
+    BASEPLATE_DIMENSIONS.y * count.y + padding[_NORTH] + padding[_SOUTH],
+];
+
 /**
  * @Summary Model a segment, which is piece of the plate without breaks
  * @param count The number of cells in this segment, on each axis
@@ -669,10 +800,7 @@ module chamfer_triangle() {
  * @param global_cell_count If applicable, the global cell count. This is used for vertical screws at plate corners
  */
 module segment(count=[1, 1], padding=[0, 0, 0, 0], connector=[false, false, false, false], global_segment_index=undef, global_cell_index=[0, 0], global_cell_count=[0, 0]) {
-    size = [
-        BASEPLATE_DIMENSIONS.x * count.x + padding[_EAST] + padding[_WEST],
-        BASEPLATE_DIMENSIONS.y * count.y + padding[_NORTH] + padding[_SOUTH],
-    ];
+    size = compute_segment_size(count, padding);
     _edge_puzzle_height_male = edge_puzzle_height_female - edge_puzzle_height_male_delta;
     // whether to cut the male edge puzzle connector to make room for the bin in the next cell. For really short connectors this is not necessary, but there's also no good reason to turn this off, so it's not user configurable at the moment
     _edge_puzzle_overlap = true;
@@ -1014,6 +1142,19 @@ module test_pattern_wall() {
     segment(count = [2, 2], connector=[false, false, false, false], padding=[5, 5, 5, 5]);
 }
 
+module test_pattern_click() {
+    count = [1, 3];
+    // this should give similar wall strength as a neighbouring cell
+    padding = [12, click1_wall_strength, click1_wall_strength, click1_wall_strength];
+    segment(count = count, connector=[false, false, false, false], padding=padding);
+    format_small = function (d) d < 1 ? str(".", d*10) : (d % 1) == 0 ? str(d) : str(d * 10);
+    txt = click1 ? str(format_small(click1_distance), "|", format_small(click1_steepness), "|", format_small(click1_height), "|", format_small(click1_strength), "|", format_small(click1_wall_strength)) : "off";
+    navigate_edge(size = compute_segment_size(count, padding), count = count, padding = padding, index = [0, 2], dir = _NORTH) 
+        translate([0, padding[_NORTH]/2, _profile_height]) 
+        linear_extrude(0.5) 
+        scale([0.7, 1]) text(txt, halign="center", valign="center", size=8);
+}
+
 if (test_pattern == 0) {
     main();
 } else if (test_pattern == 1) {
@@ -1024,4 +1165,6 @@ if (test_pattern == 0) {
     test_pattern_numbering();
 } else if (test_pattern == 4) {
     test_pattern_wall();
+} else if (test_pattern == 5) {
+    test_pattern_click();
 }

justfile

@@ -54,7 +54,7 @@ docs:
                 written.append(output)
         for f in os.listdir("docs/images"):
             if os.path.join("docs/images", f) not in written:
-                os.unlink(f)
+                os.unlink(os.path.join("docs/images", f))
         await asyncio.gather(*tasks)
 
     asyncio.run(main())

test.scad

@@ -26,4 +26,8 @@ assert_eq([3, 6, 1], plan_axis_incremental_vars(axis_norm=10, bed_norm=6.1, star
 assert_eq([2, 6, 2], plan_axis_incremental_vars(axis_norm=10, bed_norm=6.1, start_padding_norm=0.2, end_padding_norm=0.2, force_first=2));
 assert_eq([1, 6, 3], plan_axis_incremental_vars(axis_norm=10, bed_norm=6.1, start_padding_norm=0.2, end_padding_norm=0.2, force_first=1));
 
+assert_eq([[0, 1], [0, 0], [1, 0], [1, 1]], clip_polygon_max([[0, 0], [2, 0], [0, 2]], [1, 1]));
+assert_eq([[1, 1], [0, 1], [0, 0], [1, 0]], clip_polygon_max([[0, 2], [0, 0], [2, 0]], [1, 1]));
+assert_eq([[1, 0], [1, 1], [0, 1], [0, 0]], clip_polygon_max([[2, 0], [0, 2], [0, 0]], [1, 1]));
+
 cube([1, 1, 1]);