Tutorials - How to make a Involute Spur Gear !!

Spur Gear Design

Initially Take a Note on Spur Gear dimensions as follows

Module = 4mm

Number of teeth =39

Pitch Circle Diameter =156 mm

Pressure Angle =20 Deg

Addendum Circle Diameter =167.4 mm

Root Diameter = 149.70 mm

Dedendum Circle Diameter =130 mm

Hole size 80 mm

Tooth thickness =6.28mm

Base Circle Diameter =156cos(20)=146.592mm

Step 1

• ·         Select the Front plane,
• ·         Draw 130mm  Diameter circle and a  Hole 80mm Diameter circle,
• ·         Extrude 50 mm.

Step 2

Draw three circles vice the diameters are

• ·         Addendum Circle Diameter =167.4 mm,
• ·         Pitch Circle Diameter =156 mm,
• ·         Base Circle Diameter =156cos(20)=146.592mm.

Step 3 

For involute curve we need to put some parametric equations as follows

Follow the procedure and paste the equations

• Menu bar -  Insert - Model datum – Curve - In the menu manager  - From equation - Done
• Now the select the PRT_CSYS_DEF  and Cartesian (a notepad box will open)
• Just paste the following equations without modify anything..,

Base_circle_radius=146.592/2

Angle=t*90

Cir_len=(PI*Base_circle_radius*t)/2

X_ins=Base_circle_radius*cos(Angle)

Y_ins=Base_circle_radius*sin(Angle)

X=X_ins+(Cir_len*sin(Angle))

Y=Y_ins-(Cir_len*cos(Angle))

Z=0

(Note : Here  146.592/2 mm is Base Circle Radius)

File - Save - Close notepad -Preview - OK

Now you see the curve

Step 4

• ·         Again Go to sketcher using  previous sketching plane (Take references before draw )
• ·         Menu bar/right click Sketcher - References
• ·         Pick the curve and the middle circle as references.
•       Then draw a center point arc with radius of 6.28 mm on the middle circle and the starting point should start from the curve.
• Exit Sketcher

(Note : Tooth thickness=6.28mm on pitch circle)

Then

Datum point - Select the curve - offset = .50

Step 5

Now we make a datum plane passing through this point and the central axis. Then we reflect the curve about datum plane.

• Datum plane - Select the point and the axis - OK
• Now Datum plane created.

Select the curve and mirror it with reference to Datum plane.

Step 6  Now we use the curve to define the tooth profile.

Sketcher - the create an entity from edge option from tool bar - Select the two curves

Sketch - References select the three circles. Select the references as shown in the figure.

Draw two connecting lines and two center point arc as shown in figure.

Then trim the unnecessary lines to make the profile.

(Note : The profile must be closed at the end)

Step 7

Finally extrude the profile and pattern it about the central axis.

Hide all the unnecessary curves

Well the involute Spur Gear is formed successfully.