"""Metric spring and lock washers: DIN 137 form A curved spring washers and DIN 6797 form A external tooth lock
washers.

- curved (DIN 137 A): the annulus d1 x d2, s thick, curved about the X axis so that it stands h (max, the free height)
  tall: the region of the annulus between two coaxial cylinders (axis parallel to X) of radii R and R + s, with R
  chosen so that the inner surface rises h - s at the rim. Its lowest point is on the XY plane at the origin.
- tooth (DIN 6797 A): envelope, the flat blank, an annulus d1 x d2, s thick, on the XY plane; the standard gives the
  number of teeth (6 or 8) and the overall height (at least 2 s) but not the teeth's shape, so they are not modelled.
Centred on the origin.
"""
from steve import Model

size = "M4"  # Nominal size (screw)
style = "curved"  # Washer style
material = "spring-steel"  # Material

# mm. DIN 137 (1985) form A, curved: (d1 min = nominal, d2 nominal, s nominal, h max)
CURVED = {"M2": (2.2, 4.5, 0.3, 1.0), "M2.5": (2.8, 5.5, 0.3, 1.1), "M3": (3.2, 6, 0.4, 1.3), "M4": (4.3, 8, 0.5, 1.6),
          "M5": (5.3, 10, 0.5, 1.8), "M6": (6.4, 11, 0.5, 2.2), "M8": (8.4, 15, 0.5, 3.4), "M10": (10.5, 18, 0.8, 4.0)}
# mm. DIN 6797:1988-07 form A, external teeth: (d1 min = nominal, d2 max = nominal, s nominal, number of teeth)
TOOTH = {"M2": (2.2, 4.5, 0.3, 6), "M2.5": (2.7, 5.5, 0.4, 6), "M3": (3.2, 6, 0.4, 6), "M4": (4.3, 8, 0.5, 8),
         "M5": (5.3, 10, 0.6, 8), "M6": (6.4, 11, 0.7, 8), "M8": (8.4, 15, 0.8, 8)}
MATERIALS = {"spring-steel": ("steel-generic", "#4a4c50"), "stainless": ("stainless-304", "#c9ccd0")}

material_id, colour = MATERIALS[material]
model = Model()
if style == "curved":
    d1, d2, s, h = CURVED[size]
    r2, k = d2 / 2, h - s
    R = (r2 * r2 + k * k) / (2 * k)      # inner surface radius: it rises k at y = +-d2/2
    model.cylinder("blank", r2, h + 2, at=(0, 0, -1), name="Blank")
    model.cylinder("hole", d1 / 2, h + 2, at=(0, 0, -1), op="cut", name="Hole")
    model.cylinder("shell", R + s, 2 * d2, at=(-d2, 0, R + s), direction=(1, 0, 0), op="new", name="Shell")
    model.cylinder("shell_in", R, 2 * d2, at=(-d2, 0, R + s), direction=(1, 0, 0), op="cut", body="shell", name="Shell inside")
    model.combine("washer", "blank", ["shell"], op="intersect", name="Washer")
else:
    d1, d2, s, teeth = TOOTH[size]
    with model.sketch("washer_sketch", on="XY", name="Washer") as sk:
        sk.circle("outside", (0, 0), d2 / 2)
        sk.circle("inside", (0, 0), d1 / 2)
    model.extrude("washer", "washer_sketch", distance=s, name="Washer")
model.material(material_id, color=colour)
result = model.result()