PartDesign InvoluteGear/ro

Shaft design wizard

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PartDesign: Angrenaj cilindric cu dinți drepți în evolventă
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Part Design → Involute gear...
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Description

Descriere

Acest instrument vă permite să creați un profil 2D al unei roți dințate în evolventă. Acest profil 2D este complet parametric și poate fi extrudat cu funcția PartDesign Pad.

Pentru a face un profil elicoidală, acesta trebuie extrudat cu ajutorul instrumentului Sweep folosind o elice ca traiectorie

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

Usage

Create the profile

Cum se folosește

1. Go to the Part Design → Involute gear... menu.
2. Set the Involute parameters.
3. Click OK.
4. Profilul în evolventă este creat în afara corpului activ. Trageți-l și plasați-l într-un corp pentru a aplica alte funcții, cum ar fi extrudarea.

Create a spur gear

1. Select the gear profile in the Tree view.
2. Press the PartDesign Pad button.
3. Set the pad's DateLength 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 DateHeight to the desired face width of the gear.
6. To set the desired helical angle an Expression for the DateTurns 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 DateName 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 DateHelical 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 DateTurns 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 DateName of the profile.

Properties

• Angrenaj Extern: True or false

• Precizie ridicată: True or false

• Modulul:

Diametrul primitiv împărțit la numărul de dinți. Sau: Modulul X Numărul de dinți = Diametrul Primitiv (acestea sunt diametrele tangente într-o pereche de roți).

Acestea depind de distanța centrală a arborilor suport și de raportul de reducere a vitezei dintre cei doi arbori.

• Număr de dinți: Definește numărul de dinți.

• Unghiul de presiune: Unghiul ascuțit între linia de acțiune (tracțiune) și o linie normală la linia care leagă centrele de angrenaje (tangentă la cercurile primitive).

Valoarea implicită este de 20 de grade. (More 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 DatePressure 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

Related

• FCGear Workbench

Shaft design wizard

Set tip

PartDesign

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• Structure tools: Part, Group
• Helper tools: Create body, Create sketch, Edit sketch, Map sketch to face

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• Extras: Migrate, Sprocket, Involute gear, Shaft design wizard
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