pirouette/plate.py

# @author Arnaud Morin <arnaud.gfpv@mailops.fr>
# SPDX-License-Identifier: Apache-2.0
#

from math import cos, radians, sin

import cadquery as cq

from frame_params import (CF_DENSITY, FIT, TBONE_D, TENON_L, THICKNESS)


def _custom_filets(wp, corners, tol=1e-4):
    """The edges that run through the flat pattern (parallel to Z) at the
    given (x, y) corners."""
    picked = []
    for e in wp.edges().vals():
        vs = e.Vertices()
        if len(vs) != 2:
            continue
        a, b = vs[0].toTuple(), vs[1].toTuple()
        if abs(a[0] - b[0]) > 1e-6 or abs(a[1] - b[1]) > 1e-6:
            continue
        if any(abs(a[0] - cx) < tol and abs(a[1] - cy) < tol for cx, cy in corners):
            picked.append(e)
    return wp.newObject(picked)


def _mortises():
    """(x, y, angle) of the four arm root mortises, in the plate's own frame.
    angle is the mortise's long axis, which is radial."""
    return [(25.3 * cos(radians(a)),
             25.3 * sin(radians(a)), a) for a in (45.0, 135.0, 225.0, 315.0)]


def plate():
    # one quadrant, from the +X axis to the +Y axis
    quadrant = [
        (21, 0.0),
        (15, 7.0),
        (28.5, 22.9),
        (13.9, 23.7),
        (7.5, 20.5),
        (0.0, 20.5),
    ]
    # mirrored across the Y axis (x -> -x) gives quadrant 2, joining quadrant
    # 1 into the top half -- both ends now sit on the X axis, so mirrorX()
    # below can close the loop by mirroring that half across it in turn
    top_half = quadrant + [(-x, y) for x, y in reversed(quadrant)][1:]

    p = (
        cq.Workplane("XY")
        .polyline(top_half)
        .mirrorX()
        .extrude(THICKNESS)
    )

    # Filets
    p = _custom_filets(p, [(21, 0), (-21, 0), (-21, -0), (21, -0)]).fillet(2)
    p = _custom_filets(p, [(15, 7), (-15, 7), (-15, -7), (15, -7)]).fillet(2)
    p = _custom_filets(p, [(28.5, 22.9), (-28.5, 22.9), (-28.5, -22.9), (28.5, -22.9)]).fillet(4.5)
    p = _custom_filets(p, [(13.9, 23.7), (-13.9, 23.7), (-13.9, -23.7), (13.9, -23.7)]).fillet(2)
    p = _custom_filets(p, [(7.5, 20.5), (-7.5, 20.5), (-7.5, -20.5), (7.5, -20.5)]).fillet(6.5)

    # Add holes for 20x20 FC
    p = (
        p.faces(">Z")
        .workplane()
        .pushPoints([(10, 10), (-10, 10), (-10, -10), (10, -10)])
        # Holes are 2.2 to fit 2.0 screws
        .hole(2.2)
    )

    # Add holes for 25.5x25.5 FC
    p = (
        p.faces(">Z")
        .workplane()
        .pushPoints([(18.03, 0), (-18.03, 0), (0, -18.03), (0, 18.03)])
        # Holes are 2.2 to fit 2.0 screws
        .hole(2.2)
    )

    # Add holes for standoff
    x, y = (14, 20)
    p = p.faces(">Z").workplane().pushPoints(
        [(sx * x, sy * y) for sx in (-1.0, 1.0) for sy in (-1.0, 1.0)]
    ).hole(2.2)

    # Arm mortises
    length, width = TENON_L + FIT, THICKNESS
    r = TBONE_D / 2.0
    hl, hw = length / 2.0, width / 2.0
    body = (cq.Workplane("XY")
            .polyline([(-hl, -hw), (hl, -hw), (hl, hw), (-hl, hw)])
            .close().extrude(THICKNESS))
    bones = cq.Workplane("XY")
    for u in (-(hl - r), hl - r):
        for v in (-hw, hw):
            bones = bones.moveTo(u, v).circle(r)
    bones = bones.extrude(THICKNESS)

    for x, y, a in _mortises():
        # two separate cuts, not one combined cutter -- a compound of the
        # rectangle plus 4 tangent circles confuses the boolean into leaving
        # sliver solids behind
        p = p.cut(body.rotate((0, 0, 0), (0, 0, 1), a).translate((x, y, 0)))
        p = p.cut(bones.rotate((0, 0, 0), (0, 0, 1), a).translate((x, y, 0)))

    # Triangle cuts to reduce weight
    cut1 = (
        cq.Workplane("XY")
        .polyline([
            (6.5, -9),
            (6.5, 9),
            (1, 0),
        ]).close()
        .extrude(THICKNESS)
        .edges("|Z")
        .fillet(1.0)
    )
    cut2 = (
        cq.Workplane("XY")
        .polyline([
            (9.5, -9),
            (9.5, 9),
            (15, 0),
        ]).close()
        .extrude(THICKNESS)
        .edges("|Z")
        .fillet(1.0)
    )
    cut3 = (
        cq.Workplane("XY")
        .polyline([
            (11, 15),
            (-11, 15),
            (0, 4),
        ]).close()
        .extrude(THICKNESS)
        .edges("|Z")
        .fillet(1.0)
    )

    p = (
        p.cut(cut1)
        .cut(cut1.mirror("YZ"))
    )
    p = (
        p.cut(cut2)
        .cut(cut2.mirror("YZ"))
    )
    p = (
        p.cut(cut3)
        .cut(cut3.mirror("XZ"))
    )

    return p


result = plate()

assert result.solids().size() == 1, "plate is not one solid"

if "show_object" not in globals():          # running outside CQ-editor
    def show_object(*args, **kwargs):
        pass

show_object(result)


if __name__ == "__main__":

    v = result.val().Volume()
    print("plate      mass %.2f g each, %.2f g for two" % (v * CF_DENSITY, 2 * v * CF_DENSITY))