PartDesign: Profilo ad evolvente

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DisegnoPezzo IngranaggioEvolvente

Posizione nel menu
DisegnoPezzo → Ingranaggio Evolvente...
Ambiente
DisegnoPezzo
Avvio veloce
Nessuno
Introdotto nella versione
-
Vedere anche
Nessuno

Description

Descrizione

Questo strumento consente di creare un profilo 2D dell'evolvente di un ingranaggio. Questo profilo 2D è completamente parametrico, e può essere estruso con la funzione DisegnoPezzo Pad di PartDesign.
Per informazioni più dettagliate consultare le voci di Wikipedia per: Gear e Involute Gear

For more detailed information see Wikipedia's entries for: Gear and Involute Gear

Usage

Create the profile

Utilizzo

  1. Andare nel menu Part Design → Involute gear....
  2. Impostare i parametri dell'evolvente
  3. Cliccare su OK.
  4. L'evolvente dell'ingranaggio viene creato al di fuori del corpo attivo. Trascinalo e rilascialo in un corpo per applicarvi ulteriori funzioni, come il riempimento.

Create a spur gear

  1. Select the gear profile in the Tree view.
  2. Press the PartDesign Pad button.
  3. Set the pad's DatiLength to the desired face width of the gear.
  4. Click OK

Create a helical gear

introduced in version 0.19

  1. Select the gear profile in the Tree view.
  2. Press the PartDesign AdditiveHelix button.
  3. Choose as Axis the normal of the gear profile, that is Normal sketch axis introduced in version 0.20. (In earlier versions the Base Z axis can be used as long as the profile's plane has not been altered.)
  4. Choose a Height-Turns mode.
  5. Set the DatiHeight to the desired face width of the gear.
  6. To set the desired helical angle an Expression for the DatiTurns is required.
    1. Click the blue icon at the right of the input field.
    2. Enter the following formula: Height * tan(25°) / (InvoluteGear.NumberOfTeeth * InvoluteGear.Modules * pi), where 25° is an example for the desired helical angle (also known as beta-value) and InvoluteGear is the DatiName of the profile.
    3. Click OK to close the formula editor.
  7. Click OK to close the task panel.

Hint: To make the helical angle an accessible parameter, use a dynamic property:

  1. Select the profile.
  2. In the Property editor activate the Show all option in the context menu.
  3. Again in the context menu, select Add Property. Note: this entry is only available when Show all is active.
  4. In the Add Property dialog:
    1. Choose App::PropertyAngle as Type.
    2. Set Gear as Group.
    3. Set HelicalAngle as Name (without a space).
    4. Click OK
  5. Now a new property DatiHelical Angle (space added automatically), with an initial value of 0.0°, becomes available.
  6. Assign the desired helical angle to the new property.
  7. In the formula of the DatiTurns property of the AdditiveHelix, you can now reference InvoluteGear.HelicalAngle instead of the hard coded value of e.g. 25°; again assuming InvoluteGear is the DatiName of the profile.

Properties

  • External gear: True o false
  • Alta precisione: True o False
  • Modulo: Diametro diviso per il numero di denti.
  • Numero di denti: Impostare il numero di denti.
  • Angolo di pressione: Angolo acuto tra la retta di pressione e la normale alla congiungente i centri degli ingranaggi. Di default è 20 gradi. (Altre info)


Limitations

  • It is currently not possible to adjust the tooth thickness. Tooth and tooth space are distributed equally on the pitch circle. Thus the only way to control backlash is to adjust the center distance in a gear paring.
  • There is currently no undercut in the generated gear profile. That means gears with a low number of teeth can interfere with the teeth of the mating gear. The lower limit depends on the DatiPressure Angle and is around 17 teeth for 20° and 32 for 14.5°. Most practical applications tolerate a missing undercut for gears a little smaller than this theoretical limit though.

Tutorials

How to make gears in FreeCAD

Correlazioni