125 lines
4.5 KiB
Python
125 lines
4.5 KiB
Python
# @author Arnaud Morin <arnaud.gfpv@mailops.fr>
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# SPDX-License-Identifier: Apache-2.0
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#
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from math import sqrt
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import cadquery as cq
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from frame_params import (CF_DENSITY, FIT, TBONE_D, TENON_L, THICKNESS)
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ARM_MORTISE_R = 8.6543 # arm mortise centre, inboard of the
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# motor axis. Not a free number: the
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# arm's tip tenon sits at radius 46.5
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# (its root radius 19.5, plus arm.py's
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# own 25, plus half a tenon), and the
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# motor axis is at 55.1543, so anything
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# else pushes the tenon off centre in
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# its mortise. At 8.8 it overhung the
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# outer end by 0.046 and fouled the base.
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# spar mortise centre, in the base's own local frame: on the spar
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# centreline, SPAR_OFFSET outboard of the motor axis and SPAR_TENON_POS back
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# along the spar -- both shared with the spar's own tenon, so the mortise
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# and the tenon it keys into can't drift apart. Not linked by import to
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# frame_params or spar.py any more -- keep this pair in step by hand.
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SPAR_OFFSET = 2.5
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SPAR_TENON_POS = 9
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SPAR_MORTISE_X = (SPAR_OFFSET + SPAR_TENON_POS) / sqrt(2.0)
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SPAR_MORTISE_Y = (SPAR_OFFSET - SPAR_TENON_POS) / sqrt(2.0)
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SPAR_MORTISE_ANGLE = 45.0 # +-45 deg to the arm axis
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MORTISE_L = TENON_L + FIT # 4.2
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MORTISE_W = THICKNESS
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BORE_D = 5.0 # 1404 bell / boss clearance
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BOLT_SQ = 9.0 # 1404/1105 M2 pattern -- the DIAGONAL between
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# opposite bolt holes, not the square's side
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BOLT_D = 2.2 # M2 clearance
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BOLT_R = BOLT_SQ / (2.0 * sqrt(2.0))
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def bolt_points():
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return [(sx * BOLT_R, sy * BOLT_R) for sx in (-1, 1) for sy in (-1, 1)]
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def mortises():
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"""(x, y, angle) of the three mortises, in the motor base's own frame
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(origin = motor axis, +Y outboard, arm mortise at -Y). All three are
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MORTISE_L x MORTISE_W -- only position and angle differ."""
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return [
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(0.0, -ARM_MORTISE_R, 90.0),
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(-SPAR_MORTISE_X, SPAR_MORTISE_Y, 90.0 - SPAR_MORTISE_ANGLE),
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(+SPAR_MORTISE_X, SPAR_MORTISE_Y, 90.0 + SPAR_MORTISE_ANGLE),
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]
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def motor_base():
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# the open half-profile has to start and end ON the mirror axis (x = 0)
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# for mirrorY() to stitch it into one closed loop -- otherwise the two
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# halves just don't meet
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part = (
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cq.Workplane("XY")
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.polyline([
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(0.0, -15.5),
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(2.0, -15.5),
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(4.0, -10.0),
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(8.5, -9.5),
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(13.0, -4.5),
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(4.0, 7.0),
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(0.0, 7.0),
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])
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.mirrorY()
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.extrude(THICKNESS)
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)
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#return part
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part = part.edges("|Z").fillet(2.8)
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# motor bell / boss clearance, then the M2 bolt pattern
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part = (part.faces(">Z").workplane(centerOption="ProjectedOrigin")
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.hole(BORE_D))
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part = (part.faces(">Z").workplane(centerOption="ProjectedOrigin")
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.pushPoints(bolt_points()).hole(BOLT_D))
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# the three mortises: arm inboard at -Y, spars at +-45 deg, T-bone
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# relieved on the long edges. One canonical cutter, all the same size,
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# rotated and translated into each of the 3 spots.
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hl, hw = MORTISE_L / 2.0, MORTISE_W / 2.0
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r = TBONE_D / 2.0
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body = (cq.Workplane("XY")
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.polyline([(-hl, -hw), (hl, -hw), (hl, hw), (-hl, hw)])
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.close().extrude(THICKNESS))
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bones = cq.Workplane("XY")
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for u in (-(hl - r), hl - r):
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for v in (-hw, hw):
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bones = bones.moveTo(u, v).circle(r)
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bones = bones.extrude(THICKNESS)
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for x, y, angle in mortises():
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# two separate cuts, not one combined cutter -- a compound of the
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# rectangle plus 4 tangent circles confuses the boolean into leaving
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# sliver solids behind
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part = part.cut(body.rotate((0, 0, 0), (0, 0, 1), angle).translate((x, y, 0)))
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part = part.cut(bones.rotate((0, 0, 0), (0, 0, 1), angle).translate((x, y, 0)))
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return part
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result = motor_base()
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assert result.solids().size() == 1, "motor base is not one solid"
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if "show_object" not in globals(): # running outside CQ-editor
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def show_object(*args, **kwargs):
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pass
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show_object(result)
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# Mass report
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def report():
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vol = result.val().Volume()
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print(f" Mass = {vol * CF_DENSITY:5.2f} g")
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print(f" Mass x4 = {4 * vol * CF_DENSITY:5.2f} g")
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if __name__ == "__main__":
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report()
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