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ME-430 INTRODUCTION TO COMPUTER AIDED DESIGN
Helical Gear – using Surface Features
Pro/ENGINEER 2001
Dr. Herli Surjanhata

Create a one side solid protrusion for base feature of helical involute gear as shown
below:




Create gear parameters by

Set Up -> Parameters -> Part -> Create -> Integer





Enter diametral_pitch P
Enter a value of 8

Continue to create the following parameters:

Parameter Type Value Description
N Integer 39 No of teeth
AGMA_quality Integer 10
tooth_form String 20 DEG INV
2
– AGMA

Full-Depth
PA Real Number 20.0 pressure_angle

Create relations for the gear parameters. From Part menu, select

Relations -> Add

Enter the following:

DP = N/P
or
pitch_dia_gear = no_gear_teeth/diametral_pitch



Hit Enter key
twice.

Select Edit Rel and enter the following relations with a text editor.

A = 1/P addendum = 1/diametral_pitch
B = 1.25/P dedendum = 1.25/diametral_pitch
DA = DP + 2 * A outside_dia_gear = pitch_dia_gear +
2*addendum
DD = DP – 2 * B root_dia_gear = pitch_dia_gear -
2*dedendum
DB = DP * COS(PA) Base_gear_dia = pitch_dia_gear * cos
(pressure_angle)
CP = PI/P circular_pitch = pi/diametral_pitch
FW = 3 * CP Face_width


Save the file and exit the editor.

Select Show Rel to view parameters and verify the relations. Close the information
window.

Select Relations and pick the protrusion. Note the diametral dimension e.g.
∅
d0.
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Select Edit Rel and add the following relations:

d0 = DA
d1 = FW
theta_4 = 360/(2*N)
theta_1 = 360/(4*N)
phi_p = sqrt((DP/DB)^2-1)
theta_2 = 180/pi*phi_p - atan(phi_p)
theta_3 = theta_4 - theta_1 - theta_2
alpha = theta_2 + theta_1

Save the file and exit the editor.

Done -> Regenerate

Rename the coordinate system,

Set Up -> Name, pick the coordinate system and enter the new name

involute_csys

Create a datum curve for the involute tooth profile.


Select the Create Datum Curve icon.
From Equation -> Done

Pick the INVOLUTE_CSYS -> Cylindrical.
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The text editor appears, and enter the following equations:



phi=t*sqrt((DA/DB)^2-1)
r=0.5*db*sqrt(1+phi^2)
theta=(180/pi*phi-atan(phi))-alpha
z=0

File -> Exit -> Yes

Preview the curve and select OK.




INVOLUTE
CURVE
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Create a second datum curve for the root of the tooth.



Select the Create Datum Curve icon.

Sketch -> Done

Pick datum FRONT for the sketching plane and datum TOP for the TOP reference.

In addition to the default references, carefully pick the inside endpoint of the involute
datum curve.

Sketch a center line through the INVOLUTE_CSYS and create an angular dimension
from datum TOP.

Sketch a second centerline through the INVOLUTE_CSYS that is also aligned to the
inside end point of the involute datum curve.








Use the Arc, Center and Ends icon to sketch an arc with the
center aligned to the coordinate system, and the ends aligned
with the centerlines. The arc should lie inside the datum curve.
– see Figure below.


Create a diametral dimension for the arc.

Second centerline
First centerline
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Use the Line icon to create a line from the inside point of the
involute datum curve to the arc.





From Sketch pull-down menu, select Relation.



Sketch this
line!
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Select Add. Enter the following relations:

sd1 = theta_4
sd3 = DD


Pick the
, and then click the OK button.

Mirror the involute profile consisted of 2 datum curves previously created.

Feature -> Copy
Mirror -> Select -> Dependent -> Done




Select the two datum curves from the
model tree.

Done Sel -> Done

Make Datum -> Through

Select the datum axis A_1 from the model.

Through -> Point/Vertex – make sure Point/Vertex is highlighted, and the rest
(e.g. AxisEdgeCurv, Plane, Cylinder) is unchecked.

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Pick the
lowest
point as

shown on
the left.

Done





The resulted curve is shown on
the left.


Add helix angle as a new parameter.

Setup -> Parameters -> Part -> Create -> Real Number -> beta (for helix
angle)

-> 20 -> -> Done.




Create a sweep trajectory datum curve


Select the Create Datum Curve icon.
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From Equation -> Done

Pick the INVOLUTE_CSYS
Cylindrical

Type the following equations in the editor.



File -> Exit -> Yes
Preview the curve and select OK.

Create a normal trajectory datum curve


Select the Create Datum Curve icon.

Sketch -> Done
Pick the RIGHT datum plane as sketching plane.
Okay
Top -> Pick the TOP datum plane
Pick the right face of the cylinder as an additional reference.


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Sketch a straight line on the datum axis.

Pick the

, and then click the OK button.




Create a new variable section sweep surface. Select

From Insert pull-down menu, select

Surface -> Variable Section Sweep

Norm To Traj -> Select Traj

Pick the sweep trajectory as the origin trajectory.

Done Sel -> Done

Use Norm Traj -> Done
Select Traj – Pick the normal trajectory curve.
Done Sel -> Done -> Done
Open Ends -> Done
Sketch this horizontal
line.
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Use this
icon select

Loop, and pick each of the
three curve segments needed
for surface.

From Sketch pull-down menu, select
References
Sweep
trajectory
Normal
trajectory
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Select all the references in the reference
window.

Delete -> Close

Pick the
, and then click the OK button.

Copy the cutting surface

From Insert pull-down menu, select

Surface Operation -> Transform
Move -> Copy -> Done
Pick the surface just previously created
Done Sel
Rotate -> CSys

Pick the INVOLUTE_CSYS
Z axis
Okay


Type in: 360/N

Done Move


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Insert -> Cut -> Use Quilt

Query select the transformed surface.

->

Group the cutting surface and cut

Feature -> Group -> Cancel the Open window.
Local Group



Type in: cut

Select the last two features (transformed surface and cut from the model tree)


Done Sel -> Done

Pattern -> Pick the Group CUT from the Model Tree

Click on dimension 9.2°


Type in: 360/N

Done



Done


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Create a coaxial hole of 1.2 inches diameter for the shaft.

Create a chamfer 45° x d with d = 0.05 at the both sides of the hole.





Create a cut for the
keyway with the dimension
as shown on the left.



Hide the datum curves and surface



Select the curves and surface in the model tree,
right click mouse button, and select Hide


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The resulted gear is shown below: