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InternalInvoluteGear

FCGear

Descripción

Debido a la favorable relación de engrane y su fabricación relativamente sencilla, el dentado de espiral es la forma de diente más común en la construcción de máquinas. Las ruedas dentadas se encuentran allí donde se desea transferir movimiento y fuerza de una pieza a otra. Se pueden encontrar, por ejemplo, en máquinas, coches, relojes o electrodomésticos. A menudo, el movimiento se transmite directamente de una rueda dentada a otra, pero a veces también a través de una cadena. Además, se puede cambiar el sentido de giro. También es posible cambiar un movimiento radial a uno lineal mediante un cremallera involuta.

De izquierda a derecha: engranaje recto, engranaje helicoidal, engranaje helicoidal doble

Uso

1. Cambie a entorno de trabajo FCGear.
2. Hay varias formas de invocar el comando:
   • Presione el botón engranaje evolvente en la barra de herramientas.
   • Seleccione la opción Gear → Engranaje evolvente del menú.
3. Cambie el parámetro de engranaje a las condiciones requeridas (ver Propiedades).

Propiedades

Un objeto FCGear InvoluteGear se deriva de un objeto Part Feature y hereda todas sus propiedades. También tiene las siguientes propiedades adicionales:

Datos

accuracy

• Datosnumpoints (Integer): Default is 20. Change of the involute profile. Changing the value can lead to unexpected results.
• Datossimple (Bool): Default is false, true generates a simplified display (without teeth and only a cylinder in pitch diameter).

base

• Datosheight (Length): Default is 5 mm. Value of the gear width.
• Datosmodule (Length): Default is 1 mm. Module is the ratio of the reference diameter of the gear divided by the number of teeth (see Notes).
• Datosnum_teeth (Integer): Default is 15. Number of teeth (see Notes).

computed

• Datosaddendum_diameter (Length): Default is 17 mm. Outside diameter, measured at the addendum (the tip of the teeth).
• Datosangular_backlash (Angle): (read-only) The angle by which this gear can turn without moving the mating gear.
• Datospitch_diameter (Length): Default is 15 mm. The pitch diameter.
• Datosroot_diameter (Length): (read-only) The root diameter, measured at the foot of the teeth.
• Datostransverse_pitch (Length): Default is 3.14 mm. The transverse pitch.
• Datostraverse_module (Length): Default is 1 mm. The traverse module of the generated gear.

fillets

• Datoshead_fillet (Float): Default is 0 mm. A fillet for the tooth-head.
• Datosroot_fillet (Float): Default is 0 mm. A fillet for the tooth-root.
• Datosundercut (Bool): Default is false, true changes the profile of the tooth root (see Notes).

helical

• Datosdouble_helix (Bool): Default is false, true creates a double helix gear (see Notes).
• Datoshelix_angle (Angle): Default is 0 °. With the helix angle β a helical gear is created – positive value → rotation direction right, negative value → rotation direction left (see Notes).
• Datosproperties_from_tool (Bool): Default is false. If true and Datoshelix_angle is not zero, gear parameters are recomputed internally for the rotated gear.

hole

• DatosAxle_hole (Bool): Default is false. true enables a central hole for an axle.
• DatosAxle_holesize (Length): Default is 10 mm. Diameter of the hole for an axle.
• Datosoffset_hole (Bool): Default is false, true enables an offset hole.
• Datosoffset_holeoffset (Length): Default is 10 mm. The offset of the offset hole.
• Datosoffset_holesize (Length): Default is 10 mm. The diameter of the offset hole.

involute

• Datospressure_angle (Angle): Default is 20 ° (see Notes).
• Datosshift (Float): Default is 0. Generates a positive and negative profile shift (see Notes).

tolerance

• Datosbacklash (Length): Default is 0. Backlash, also called lash or play, is the distance between the teeth at a gear pair.
• Datosclearance (Float): Default is 0.25 (see Notes).
• Datoshead (Float): Default is 0. This value is used to change the tooth height.
• Datosreversed_backlash (Bool): true backlash decrease or false (default) backlash increase see Notes).

version

• Datosversion (String):

Notas

• beta: When beta is changed, pitch diameter also changes. The following formula illustrates how the parameters interact: d = m * Z / cos beta (Z = number of teeth, d = pitch diameter, m = module). This means for the spur gear: cos beta = 0 and for the helical gear: cos beta > 0. However, a helix angle of less than 10° has hardly any advantages over straight teeth.
• clearance: At a gear pair, clearance is the distance between the tooth tip of the first gear and the tooth root of the second gear.
• double_gear: To use the double helical gearing the helix angle β (beta) for the helical gearing must first be entered.
• module: Using ISO (International Organization for Standardization) guidelines, Module size is designated as the unit representing gear tooth-sizes. Module (m): m = 1 (p = 3.1416), m = 2 (p = 6.2832), m = 4 (p = 12.566). If you multiply Module by Pi, you can obtain Pitch (p). Pitch is the distance between corresponding points on adjacent teeth.
• shift: Profile shift is not merely used to prevent undercut. It can be used to adjust center distance between two gears. If a positive correction is applied, such as to prevent undercut in a pinion, the tooth thickness at top is thinner.
• teeth: If the number of teeth is changed, the pitch diameter also changes (dw).
• undercut: Undercut is used when the number of teeth of a gear is too small. Otherwise the mating gear will cut into the tooth root. The undercut not only weakens the tooth with a wasp-like waist, but also removes some of the useful involute adjacent to the base circle.
• pressure_angle: 20° is a standard value here. The pressure angle is defined as the angle between the line-of-action (common tangent to the base circles) and a perpendicular to the line-of-centers. Thus, for standard gears, 14.5° pressure angle gears have base circles much nearer to the roots of teeth than 20° gears. It is for this reason that 14.5° gears encounter greater undercutting problems than 20° gears. Important. the pressure angle changes with a profile shift. Only change the parameter, if sufficient knowledge of the gear geometry is available.
• reversed_backlash: If there are several gears, pay attention to which gear the parameter is set for.

Limitaciones

A 2D tooth profile, obtained by setting the Datosheight to zero, cannot be used with features requiring a 2D shape. For example PartDesign Pad and PartDesign AdditiveHelix features do not accept such a profile as base. For technical details, please refer to the related issue on GitHub.

Fórmulas útiles

Standard Spur Gears

Aquí "standard" se refiere a aquellos engranajes rectos sin coeficiente de cambio de perfil (${\displaystyle x}$).

Basic formulas common to internal and external standard spur gears

Symbol	Term	Formula	FCGear Parameter
${\displaystyle m}$	Module	-	${\displaystyle {\texttt {module}}}$
${\displaystyle z}$	Number of Teeth	-	${\displaystyle {\texttt {teeth}}}$
${\displaystyle \alpha }$	Pressure Angle	Typically, ${\displaystyle \alpha =20^{\circ }}$	${\displaystyle {\texttt {pressure}}{\_}{\texttt {angle}}}$
${\displaystyle d}$	Reference Diameter or Pitch Diameter	${\displaystyle z\cdot m}$	${\displaystyle {\texttt {dw}}}$
${\displaystyle h_{a}^{*}}$	Addendum Coefficient	Typically, ${\displaystyle h_{a}^{*}=1}$	${\displaystyle h_{a}^{*}=1+{\texttt {head}}}$
${\displaystyle h_{f}^{*}}$	Dedendum Coefficient	Typically, ${\displaystyle h_{f}^{*}=1.25}$	${\displaystyle h_{f}^{*}=1+{\texttt {clearance}}}$
${\displaystyle h_{a}}$	Addendum	${\displaystyle h_{a}=h_{a}^{*}\cdot m}$	-
${\displaystyle h_{f}}$	Dedendum	${\displaystyle h_{f}=h_{f}^{*}\cdot m}$	-
${\displaystyle h}$	Tooth Height or Tooth Depth	${\displaystyle h=h_{a}+h_{f}}$ Typically, ${\displaystyle h=2.25\cdot m}$	-
${\displaystyle x}$	Profile Shift Coefficient	For standard gears, ${\displaystyle x=0}$	${\displaystyle {\texttt {shift}}}$

Basic formulas specific to external standard spur gears

Symbol	Term	Formula
${\displaystyle d_{a}}$	Tip Diameter	${\displaystyle d_{a}=d+2\cdot h_{a}}$ Typically, ${\displaystyle d_{a}=(z+2)\cdot m}$
${\displaystyle d_{f}}$	Root Diameter	${\displaystyle d_{f}=d-2\cdot h_{f}}$ Typically, ${\displaystyle d_{f}=(z-2.5)\cdot m}$

Basic formulas specific to internal standard spur gears

Symbol	Term	Formula
${\displaystyle d_{a}}$	Tip Diameter	${\displaystyle d_{a}=d-2\cdot h_{a}}$ Typically, ${\displaystyle d_{a}=(z-2)\cdot m}$
${\displaystyle d_{f}}$	Root Diameter	${\displaystyle d_{f}=d+2\cdot h_{f}}$ Typically, ${\displaystyle d_{f}=(z+2.5)\cdot m}$

Basic formulas specific for a pair of external standard spur gears

Symbol	Term	Formula
${\displaystyle a}$	Center Distance	${\displaystyle a={\frac {d_{1}+d_{2}}{2}}}$
${\displaystyle c}$	Tip and Root Clearance	${\displaystyle c_{1}=h_{f2}-h_{a1}}$ ${\displaystyle c_{2}=h_{f1}-h_{a2}}$ Typically, ${\displaystyle c=0.25\cdot m}$

• Helical and double helical gearing
  • pitch diameter (dw) = module * teeth : cos beta
  • axle base = (pitch diameter (dw) 1 + pitch diameter (dw) 2) : 2
  • addendum diameter = pitch diameter (dw) + 2 * module
  • module = pitch diameter (dw) * cos beta : teeth

Programación

Utilice el poder de Python para automatizar el modelado de sus engranajes:

import FreeCAD as App
import freecad.gears.commands
gear = freecad.gears.commands.CreateInvoluteGear.create()
gear.teeth = 20
gear.beta = 20
gear.height = 10
gear.double_helix = True
App.ActiveDocument.recompute()
Gui.SendMsgToActiveView("ViewFit")

InternalInvoluteGear

FCGear