85 lines
3.0 KiB
Plaintext
85 lines
3.0 KiB
Plaintext
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// Herringbone Gear
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// A herringbone, or double-helical gear, is a cylindrical gear type with angled teeth in opposing directions. This allows the quietness and smoothness of a helical gear, without applying a directional load while turning
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// Set units
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@settings(defaultLengthUnit = mm)
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// Define a function to create a herringbone gear
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fn herringboneGear(nTeeth, module, pressureAngle, helixAngle, gearHeight) {
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// Calculate gear parameters
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pitchDiameter = module * nTeeth
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addendum = module
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deddendum = 1.25 * module
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baseDiameter = pitchDiameter * cos(pressureAngle)
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tipDiameter = pitchDiameter + 2 * module
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// Define a function to create a rotated gear sketch on an offset plane
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fn herringboneGearSketch(offsetHeight) {
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// Calculate the amount to rotate each planar sketch of the gear given the gear helix angle and total gear height
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helixCalc = acos(offsetHeight * tan(helixAngle) / (tipDiameter / 2))
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// Using the gear parameters, sketch an involute tooth spanning from the base diameter to the tip diameter
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herringboneGearSketch = startSketchOn(offsetPlane(XY, offset = offsetHeight))
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|> startProfile(at = polar(angle = helixCalc, length = baseDiameter / 2))
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|> involuteCircular(
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startRadius = baseDiameter / 2,
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endRadius = tipDiameter / 2,
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angle = helixCalc,
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tag = $seg01,
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)
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|> line(endAbsolute = polar(angle = 160 / nTeeth + helixCalc, length = tipDiameter / 2))
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|> involuteCircular(
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startRadius = baseDiameter / 2,
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endRadius = tipDiameter / 2,
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angle = -(4 * atan(segEndY(seg01) / segEndX(seg01)) - (3 * helixCalc)),
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reverse = true,
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)
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// Position the end line of the sketch at the start of the next tooth
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|> line(endAbsolute = polar(angle = 360 / nTeeth + helixCalc, length = baseDiameter / 2))
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// Pattern the sketch about the center by the specified number of teeth, then close the sketch
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|> patternCircular2d(
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%,
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instances = nTeeth,
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center = [0, 0],
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arcDegrees = 360,
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rotateDuplicates = true,
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)
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|> close()
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// Create a center hole with an 8mm diameter
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|> subtract2d(tool = circle(center = [0, 0], radius = 4))
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return herringboneGearSketch
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}
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// Draw a gear sketch on the base plane
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gearSketch001 = herringboneGearSketch(offsetHeight = 0)
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// Draw a gear sketch that has been rotated by the helix angle
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gearSketch002 = herringboneGearSketch(offsetHeight = gearHeight / 2)
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// Draw a gear sketch at the total gear height that reverses the angle direction
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gearSketch003 = clone(gearSketch001)
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|> translate(z = gearHeight)
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// Loft each rotated gear sketch together to form a herringbone gear
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herringboneGear = loft(
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[
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gearSketch001,
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gearSketch002,
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gearSketch003
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],
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vDegree = 1,
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)
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return herringboneGear
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}
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herringboneGear(
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nTeeth = 25,
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module = 1,
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pressureAngle = 14,
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helixAngle = 40,
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gearHeight = 8,
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)
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