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PD: Fix exception from InvoluteGear with zero fillets

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While gears without a root fillet may have limited real-live use cases,
during number-input it happens regulary to have a zero fillet radius as
intermediate state. With this commit such a situation is now handled
gracefully.
This commit is contained in:
Jonas Bähr
2023-02-14 22:48:43 +01:00
committed by Uwe
parent 4f87850788
commit d5e341b044
2 changed files with 62 additions and 16 deletions
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23
src/Mod/PartDesign/PartDesignTests/TestInvoluteGear.py
View File

@@ -130,6 +130,29 @@ class TestInvoluteGear(unittest.TestCase):
self.assertNoIntersection(hub.Shape, makeCircle(tip_diameter/2 - delta), "Teeth extent below tip circle")
self.assertNoIntersection(hub.Shape, makeCircle(root_diameter/2 + delta), "Teeth extend beyond root circle")
def testZeroFilletExternalGearProfile_BaseAboveRoot(self):
gear = InvoluteGearFeature.makeInvoluteGear('InvoluteGear')
# below 42 teeth, with default dedendum 1.25, we have some non-involute flanks
gear.NumberOfTeeth = 41
gear.RootFilletCoefficient = 0
self.assertSuccessfulRecompute(gear)
self.assertClosedWire(gear.Shape)
def testZeroFilletExternalGearProfile_BaseBelowRoot(self):
gear = InvoluteGearFeature.makeInvoluteGear('InvoluteGear')
# above 41 teeth, with default dedendum 1.25, the root is within the involute flank
gear.NumberOfTeeth = 42
gear.RootFilletCoefficient = 0
self.assertSuccessfulRecompute(gear)
self.assertClosedWire(gear.Shape)
def testZeroFilletInternalGearProfile(self):
gear = InvoluteGearFeature.makeInvoluteGear('InvoluteGear')
gear.ExternalGear = False
gear.RootFilletCoefficient = 0
self.assertSuccessfulRecompute(gear)
self.assertClosedWire(gear.Shape)
def testUsagePadGearProfile(self):
profile = InvoluteGearFeature.makeInvoluteGear('GearProfile')
body = self.Doc.addObject('PartDesign::Body','GearBody')

55
src/Mod/PartDesign/fcgear/involute.py
View File

@@ -63,7 +63,7 @@ def CreateExternalGear(w, m, Z, phi,
Rf = Rc # radius at top of fillet, assuming fillet below involute
filletWithinInvolute = Rf > Rb # above the base circle we have the involute,
# below we have a straight line towards the center.
if (filletWithinInvolute):
if (filletWithinInvolute and fRad > 0):
# In this case we need tangency of the involute and the fillet circle.
# It has to be somewhere between max(Rb,Rroot) and Rc.
# So we need the radius r from the origin depending on the tangent angle, for both:
@@ -149,7 +149,16 @@ def CreateExternalGear(w, m, Z, phi,
t_inc = 2.0 * pi / float(Z)
thetas = [(x * t_inc) for x in range(Z)]
w.move(fillet) # start at top of fillet
# Make sure we begin *exactly* where our last curve ends.
# In theory start == rotate(end, angle_of_last_tooth), but in practice we have limited
# precision. Especially if we don't have a fillet, we end at rootNext, not filletNext.
# And even though these two should also be equal, they are calculated differently,
# which is enough for the resulting wire not being closed any more.
# So to be on the save side, we begin at rotate(end, angle_of_last_tooth), not start.
if fRad > 0:
w.move(rotate(filletNext, thetas[-1])) # start at top of front profile
else:
w.move(rotate(rootNext, thetas[-1])) # start at top of front profile
for theta in thetas:
w.theta = theta
@@ -171,10 +180,12 @@ def CreateExternalGear(w, m, Z, phi,
w.line(filletR) # line down to topof fillet
if (rootNext[1] > rootR[1]): # is there a section of root circle between fillets?
w.arc(rootR, fRad, 0) # back fillet
if fRad > 0:
w.arc(rootR, fRad, 0) # back fillet
w.arc(rootNext, Rroot, 1) # root circle arc
w.arc(filletNext, fRad, 0)
if fRad > 0:
w.arc(filletNext, fRad, 0)
w.close()
return w
@@ -239,14 +250,16 @@ def CreateInternalGear(w, m, Z, phi,
# interpretation of it: The tangent angle of the involute experiences the same rotation as the
# involute itself. So its is just a simple offset: Our q(r) becomes qi(r) - qc(i) - phi_corr,
# where phi_corr is the amount we (virtually) turn our involute around the origin.
phi_corr = genInvolutePolar(Rb, Rroot) + atan(fRad / Rroot)
q = lambda r: (sqrt(r**2 - Rb**2) / Rb
- asin((r**2 - fRad**2 - Rc**2) / (2 * fRad * Rc))
- phi_corr)
q_prime = lambda r: (r / (sqrt(-Rb**2 + r**2) * Rb)
- r / (fRad * Rc * sqrt(1 - 1/4 * (r**2 - fRad**2 - Rc**2)**2 / (fRad**2 * Rc**2))))
Rf = findRootNewton(q, q_prime, x_min=max(Rb, Rc), x_max=Rroot)
if (fRad > 0):
phi_corr = genInvolutePolar(Rb, Rroot) + atan(fRad / Rroot)
q = lambda r: (sqrt(r**2 - Rb**2) / Rb
- asin((r**2 - fRad**2 - Rc**2) / (2 * fRad * Rc))
- phi_corr)
q_prime = lambda r: (r / (sqrt(-Rb**2 + r**2) * Rb)
- r / (fRad * Rc * sqrt(1 - 1/4 * (r**2 - fRad**2 - Rc**2)**2 / (fRad**2 * Rc**2))))
Rf = findRootNewton(q, q_prime, x_min=max(Rb, Rc), x_max=Rroot)
else:
Rf = Rroot # no fillet
# ****** calculate angles (all in radians)
@@ -298,8 +311,16 @@ def CreateInternalGear(w, m, Z, phi,
t_inc = 2.0 * pi / float(Z)
thetas = [(x * t_inc) for x in range(Z)]
w.move(fillet) # start at top of front profile
# Make sure we begin *exactly* where our last curve ends.
# In theory start == rotate(end, angle_of_last_tooth), but in practice we have limited
# precision. Especially if we don't have a fillet, we end at rootNext, not filletNext.
# And even though these two should also be equal, they are calculated differently,
# which is enough for the resulting wire not being closed any more.
# So to be on the save side, we begin at rotate(end, angle_of_last_tooth), not start.
if fRad > 0:
w.move(rotate(filletNext, thetas[-1])) # start at top of front profile
else:
w.move(rotate(rootNext, thetas[-1])) # start at top of front profile
for theta in thetas:
w.theta = theta
@@ -324,10 +345,12 @@ def CreateInternalGear(w, m, Z, phi,
w.curve(*invR[1:])
if (rootNext[1] > rootR[1]): # is there a section of root circle between fillets?
w.arc(rootR, fRad, 1) # back fillet
if fRad > 0:
w.arc(rootR, fRad, 1) # back fillet
w.arc(rootNext, Rroot, 1) # root circle arc
w.arc(filletNext, fRad, 1)
if fRad > 0:
w.arc(filletNext, fRad, 1)
w.close()