calibration: angle coupon -- seven unsupported ramps 30-60 deg for the Overhang slider

prototype/calibration/angle/gen.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+"""Angle coupon: what overhang angle does YOUR printer manage with no support at
+all? Sets the Overhang slider (the surface angle from the plate below which a
+face gets support).
+
+Print it with NO supports (slicer supports off, no fins). ONE solid piece: a bar
+standing on the plate with seven ramps sticking out of it, each underside at its
+own angle from the plate (30-60 deg, every one rising the same 8 mm). Read the
+undersides: the shallowest ramp that printed clean is your Overhang setting.
+Ramp k carries k dots.
+
+    python3 prototype/calibration/angle/gen.py      # -> out/angle-coupon.stl (no build.js: no supports)
+"""
+import math
+import shutil
+import sys
+from pathlib import Path
+
+import trimesh
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+from coupon import bx, dots, write  # noqa: E402
+
+ANGLES = [30, 35, 40, 45, 50, 55, 60]   # the slider runs 30-70; past 60 nearly every printer is fine
+BAR_W, Z0, RISE, TOP_T, W, STEP = 10.0, 2.0, 8.0, 2.0, 10.0, 14.0
+
+
+def ramp(x, side, angle):
+    """A prism off the bar face: underside from (bar, Z0) up to (bar + d, Z0 + RISE),
+    vertical outer face, flat top RISE + TOP_T up."""
+    d = RISE / math.tan(math.radians(angle))
+    y_in, y_out = side * BAR_W / 2, side * (BAR_W / 2 + d)
+    top = Z0 + RISE + TOP_T
+    yz = [(y_in, Z0), (y_out, Z0 + RISE), (y_out, top), (y_in - side * 0.5, top), (y_in - side * 0.5, Z0)]
+    if side < 0:
+        yz = yz[::-1]                     # keep the outline counter-clockwise
+    pts = [(y, z) for y, z in yz]
+    poly = trimesh.path.polygons.Polygon(pts)
+    m = trimesh.creation.extrude_polygon(poly, W)          # outline in XY, extruded along +Z
+    # outline (y, z) drawn as (x', y'), extruded along z' -> map x'->y, y'->z, z'->x
+    m.apply_transform([[0, 0, 1, x], [1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 0, 1]])
+    return m, d
+
+
+parts, rungs = [], []
+for k, a in enumerate(ANGLES):
+    side = 1 if k < 4 else -1
+    x = 4.0 + (k % 4) * STEP
+    m, d = ramp(x, side, a)
+    parts.append(m)
+    parts += dots(k + 1, x + 1.0, side * (BAR_W / 2 + d - 1.5), Z0 + RISE + TOP_T, step=1.4, size=0.9)
+    rungs.append({'id': k + 1, 'angle': a, 'depth': round(d, 1)})
+L = 4.0 + 3 * STEP + W + 4.0
+parts.append(bx(0, L, -BAR_W / 2, BAR_W / 2, 0, Z0 + RISE + TOP_T + 2))
+m = write(__file__, parts, rungs)
+out = Path(__file__).parent / 'out'
+shutil.copy(out / 'coupon_part.stl', out / 'angle-coupon.stl')
+print(f'angle coupon {m.extents.round(1)} mm')
+for r in rungs: print(f"  ramp {r['id']} ({r['id']} dots): {r['angle']} deg, reaches {r['depth']} mm out")