107 lines
3.0 KiB
Python
107 lines
3.0 KiB
Python
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import cadquery as Cq
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import math
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import unittest
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def hirth_joint(radius=60,
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radius_inner=40,
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radius_centre=30,
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base_height=20,
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n_tooth=16,
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tooth_height=16,
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tooth_height_inner=2):
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"""
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Creates a cylindrical Hirth Joint
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"""
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# ensures secant doesn't blow up
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assert n_tooth >= 5
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# angle of half of a single tooth
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theta = math.pi / n_tooth
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# Generate a tooth by lofting between two curves
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inner_raise = (tooth_height - tooth_height_inner) / 2
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# Outer tooth triangle spans a curve of length `2 pi r / n_tooth`. This
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# creates the side profile (looking radially inwards) of each of the
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# triangles.
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outer = [
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(radius * math.tan(theta), 0),
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(0, tooth_height),
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(-radius * math.tan(theta), 0),
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]
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inner = [
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(radius_inner * math.sin(theta), 0),
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(radius_inner * math.sin(theta), inner_raise - tooth_height_inner / 2),
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(0, inner_raise + tooth_height_inner / 2),
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(-radius_inner * math.sin(theta), inner_raise - tooth_height_inner / 2),
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(-radius_inner * math.sin(theta), 0),
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]
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tooth = (
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Cq.Workplane('YZ')
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.polyline(inner)
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.close()
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.workplane(offset=radius - radius_inner)
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.polyline(outer)
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.close()
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.loft(combine=True)
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.val()
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)
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tooth_centre_radius = radius_inner * math.cos(theta)
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teeth = (
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Cq.Workplane('XY')
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.polarArray(radius=radius_inner, startAngle=0, angle=360, count=n_tooth)
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.eachpoint(lambda loc: tooth.located(loc))
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.intersect(Cq.Solid.makeCylinder(
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height=base_height + tooth_height,
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radius=radius,
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))
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)
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base = (
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Cq.Workplane('XY')
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.cylinder(
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height=base_height,
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radius=radius,
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centered=(True, True, False))
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.faces(">Z").tag("bore")
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.union(teeth.val().move(Cq.Location((0,0,base_height))))
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.clean()
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)
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#base.workplane(offset=tooth_height/2).circle(radius=radius,forConstruction=True).tag("mate")
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base.polyline([(0, 0, 0), (0, 0, 1)], forConstruction=True).tag("mate")
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return base
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def hirth_assembly():
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"""
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Example assembly of two Hirth joints
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"""
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rotate = 180 / 16
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obj1 = hirth_joint().faces(tag="bore").cboreHole(
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diameter=10,
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cboreDiameter=20,
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cboreDepth=3)
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obj2 = (
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hirth_joint()
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.rotate(
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axisStartPoint=(0,0,0),
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axisEndPoint=(0,0,1),
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angleDegrees=rotate
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)
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)
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result = (
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Cq.Assembly()
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.add(obj1, name="obj1", color=Cq.Color(0.8,0.8,0.5,0.3))
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.add(obj2, name="obj2", color=Cq.Color(0.5,0.5,0.5,0.3), loc=Cq.Location((0,0,80)))
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.constrain("obj1?mate", "obj2?mate", "Axis")
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.solve()
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)
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return result
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class TestJoints(unittest.TestCase):
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def test_hirth_assembly(self):
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print(Cq.__version__)
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hirth_assembly()
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if __name__ == '__main__':
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unittest.main()
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