Add an "internal involute gear" command and feature
This reuses the same (external) tooth profile from pygear but swap some parameters to make the resulting gear internal. This prototype is mostly a copy of the external involute gear. Eventually we should refactor this to share more code but this has to be coordinated with the megagrant endevour. Otherwise merging becomes a nightmere. Note that in contrast to the involute rack I choose to base the "thickness" on the pitch diameter, not the root diameter. This has the benefit of keeping the outside diameter stable when e.g. adjusting the clearance. And setting the outside diameter directly could result in an invalid shape when chaning the numnber of teeth. The default head value of "-0.4" is choosen to match the invernal gear profile from the PartDewign WB.
This commit is contained in:
Jonas Bähr
@@ -19,7 +19,7 @@
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import os
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import FreeCAD
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import FreeCADGui as Gui
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from .features import ViewProviderGear, InvoluteGear, InvoluteGearRack
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from .features import ViewProviderGear, InvoluteGear, InternalInvoluteGear, InvoluteGearRack
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from .features import CycloidGear, BevelGear, CrownGear, WormGear, TimingGear, LanternGear, HypoCycloidGear
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@@ -79,7 +79,15 @@ class CreateInvoluteGear(BaseCommand):
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GEAR_FUNCTION = InvoluteGear
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Pixmap = os.path.join(BaseCommand.ICONDIR, 'involutegear.svg')
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MenuText = 'Involute gear'
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ToolTip = 'Create an Involute gear'
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ToolTip = 'Create an external involute gear'
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class CreateInternalInvoluteGear(BaseCommand):
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NAME = "internalinvolutegear"
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GEAR_FUNCTION = InternalInvoluteGear
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Pixmap = os.path.join(BaseCommand.ICONDIR, 'involutegear.svg')
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MenuText = 'Internal involute gear'
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ToolTip = 'Create an internal involute gear'
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class CreateInvoluteRack(BaseCommand):
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@@ -272,6 +272,147 @@ class InvoluteGear(BaseGear):
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def __setstate__(self, state):
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return None
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class InternalInvoluteGear(BaseGear):
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"""FreeCAD internal involute gear
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Using the same tooth as the external, just turning it inside-out:
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addedum becomes dedendum, clearance becomes head, negate the backslash, ...
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"""
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def __init__(self, obj):
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super(InternalInvoluteGear, self).__init__(obj)
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self.involute_tooth = InvoluteTooth()
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obj.addProperty(
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"App::PropertyBool", "simple", "precision", "simple")
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obj.addProperty("App::PropertyInteger",
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"teeth", "gear_parameter", "number of teeth")
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obj.addProperty(
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"App::PropertyLength", "module", "gear_parameter", "normal module if properties_from_tool=True, \
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else it's the transverse module.")
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obj.addProperty(
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"App::PropertyFloat", "shift", "gear_parameter", "shift")
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obj.addProperty(
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"App::PropertyLength", "height", "gear_parameter", "height")
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obj.addProperty(
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"App::PropertyLength", "thickness", "gear_parameter", "thickness")
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obj.addProperty(
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"App::PropertyAngle", "pressure_angle", "involute_parameter", "pressure angle")
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obj.addProperty(
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"App::PropertyFloat", "clearance", "gear_parameter", "clearance")
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obj.addProperty("App::PropertyInteger", "numpoints",
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"precision", "number of points for spline")
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obj.addProperty(
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"App::PropertyAngle", "beta", "gear_parameter", "beta ")
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obj.addProperty(
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"App::PropertyBool", "double_helix", "gear_parameter", "double helix")
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obj.addProperty(
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"App::PropertyLength", "backlash", "tolerance", "backlash")
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obj.addProperty(
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"App::PropertyBool", "reversed_backlash", "tolerance", "backlash direction")
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obj.addProperty(
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"App::PropertyFloat", "head", "gear_parameter", "head_value * modul_value = additional length of head")
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obj.addProperty(
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"App::PropertyBool", "properties_from_tool", "gear_parameter", "if beta is given and properties_from_tool is enabled, \
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gear parameters are internally recomputed for the rotated gear")
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obj.addProperty("App::PropertyPythonObject",
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"gear", "gear_parameter", "test")
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obj.addProperty("App::PropertyLength", "dw",
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"computed", "pitch diameter", 1)
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obj.addProperty("App::PropertyLength", "transverse_pitch",
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"computed", "transverse_pitch", 1)
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obj.addProperty("App::PropertyLength", "outside_diameter",
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"computed", "Outside diameter", 1)
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self.add_limiting_diameter_properties(obj)
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obj.gear = self.involute_tooth
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obj.simple = False
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obj.teeth = 15
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obj.module = '1. mm'
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obj.shift = 0.
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obj.pressure_angle = '20. deg'
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obj.beta = '0. deg'
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obj.height = '5. mm'
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obj.thickness = '5 mm'
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obj.clearance = 0.25
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obj.head = -0.4 # using head=0 and shift=0.5 may be better, but makes placeing the pinion less intuitive
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obj.numpoints = 6
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obj.double_helix = False
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obj.backlash = '0.00 mm'
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obj.reversed_backlash = False
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obj.properties_from_tool = False
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self.obj = obj
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obj.Proxy = self
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def add_limiting_diameter_properties(self, obj):
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obj.addProperty("App::PropertyLength", "da",
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"computed", "inside diameter", 1)
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obj.addProperty("App::PropertyLength", "df",
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"computed", "root diameter", 1)
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def generate_gear_shape(self, fp):
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fp.gear.double_helix = fp.double_helix
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fp.gear.m_n = fp.module.Value
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fp.gear.z = fp.teeth
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fp.gear.undercut = False # no undercut for internal gears
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fp.gear.shift = fp.shift
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fp.gear.pressure_angle = fp.pressure_angle.Value * np.pi / 180.
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fp.gear.beta = fp.beta.Value * np.pi / 180
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fp.gear.clearance = fp.head # swap head and clearance to become "internal"
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fp.gear.backlash = fp.backlash.Value * \
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(fp.reversed_backlash - 0.5) * 2. # negate "reversed_backslash", for "internal"
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fp.gear.head = fp.clearance # swap head and clearance to become "internal"
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# checksbackwardcompatibility:
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if "properties_from_tool" in fp.PropertiesList:
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fp.gear.properties_from_tool = fp.properties_from_tool
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fp.gear._update()
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# computed properties
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fp.dw = "{}mm".format(fp.gear.dw)
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fp.transverse_pitch = "{}mm".format(fp.gear.pitch)
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fp.outside_diameter = fp.dw + 2 * fp.thickness
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# checksbackwardcompatibility:
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if not "da" in fp.PropertiesList:
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self.add_limiting_diameter_properties(fp)
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fp.da = "{}mm".format(fp.gear.df) # swap addednum and dedendum for "internal"
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fp.df = "{}mm".format(fp.gear.da) # swap addednum and dedendum for "internal"
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pts = fp.gear.points(num=fp.numpoints)
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rotated_pts = pts
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rot = rotation(-fp.gear.phipart)
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for i in range(fp.gear.z - 1):
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rotated_pts = list(map(rot, rotated_pts))
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pts.append(np.array([pts[-1][-1], rotated_pts[0][0]]))
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pts += rotated_pts
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pts.append(np.array([pts[-1][-1], pts[0][0]]))
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outer_circle = Part.Wire(Part.makeCircle(fp.outside_diameter / 2.))
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if not fp.simple:
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wi = []
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for i in pts:
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out = BSplineCurve()
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out.interpolate(list(map(fcvec, i)))
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wi.append(out.toShape())
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wi = Wire(wi)
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wi.reverse() # turn inside out
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if fp.height.Value == 0:
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return Part.makeCompound([outer_circle, wi])
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elif fp.beta.Value == 0:
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sh = Face([outer_circle, wi])
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return sh.extrude(App.Vector(0, 0, fp.height.Value))
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else:
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tool = helicalextrusion(
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wi, fp.height.Value, fp.height.Value * np.tan(fp.gear.beta) * 2 / fp.gear.d, fp.double_helix)
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return Part.makeCylinder(fp.outside_diameter / 2., fp.height.Value).cut(tool)
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else:
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inner_circle = Part.Wire(Part.makeCircle(fp.dw / 2.))
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inner_circle.reverse()
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sh = Face([outer_circle, inner_circle])
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return sh.extrude(App.Vector(0, 0, fp.height.Value))
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def __getstate__(self):
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return None
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def __setstate__(self, state):
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return None
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class InvoluteGearRack(BaseGear):
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@@ -37,6 +37,7 @@ class GearWorkbench(Workbench):
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Icon = os.path.join(__dirname__, 'icons', 'gearworkbench.svg')
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commands = [
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"CreateInvoluteGear",
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"CreateInternalInvoluteGear",
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"CreateInvoluteRack",
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"CreateCycloidGear",
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"CreateBevelGear",
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@@ -50,7 +51,7 @@ class GearWorkbench(Workbench):
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return "Gui::PythonWorkbench"
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def Initialize(self):
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from .commands import CreateCycloidGear, CreateInvoluteGear
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from .commands import CreateCycloidGear, CreateInvoluteGear, CreateInternalInvoluteGear
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from .commands import CreateBevelGear, CreateInvoluteRack, CreateCrownGear
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from .commands import CreateWormGear, CreateTimingGear, CreateLanternGear
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from .commands import CreateHypoCycloidGear
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@@ -59,6 +60,7 @@ class GearWorkbench(Workbench):
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self.appendMenu("Gear", self.commands)
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# Gui.addIconPath(App.getHomePath()+"Mod/gear/icons/")
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Gui.addCommand('CreateInvoluteGear', CreateInvoluteGear())
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Gui.addCommand('CreateInternalInvoluteGear', CreateInternalInvoluteGear())
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Gui.addCommand('CreateCycloidGear', CreateCycloidGear())
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Gui.addCommand('CreateBevelGear', CreateBevelGear())
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Gui.addCommand('CreateInvoluteRack', CreateInvoluteRack())
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