# Creating scalable associative geometry/features in NX

Pinion Gear using Through Curves with associative, scaled geometry (NX9)

1. ### Step 1:

Before we get started; looking at this design as with any design, we want to parameterize elements that could change at a later date. This is beyond the scope of a simple model making exercise and more in step with actual real-world, dynamic, product design environments. For the sake of this tutorial, we are going to parameterize the helix angle but this could be the pinion shaft diameter, spline count, and/or any number of elements. This is where design 'future proofing' and paramaterization really come into play.

2. ### Step 2:

Create an expression, name it angle_sections with a value of 15, units = degrees

3. ### Step 3:

Create the following sketch on the XY plane:

Tip: Construct the highlighted curves; use symmetry across Y, then use a circular pattern to create 6 instances. The unneeded portions of the base diameter are then trimmed away. Finished sketch should be fully constrained.

4. ### Step 4:

Insert > Associative Copy > Pattern Geometry

For the Pitch Angle, select formula, then the expression angle_sections, select OK

Notice the option in Settings for Associative geometry generation? You will want to look for Associative options in everything NX.

We now have 3 sets of associative curves, 15 degrees apart, all on the same plane. We still need elements at 45 mm, 95 mm and those elements need scaling; 75% and 50% respectively.

5. ### Step 5:

Extrude the first 15 degree instance 45 mm

6. ### Step 6:

Scale the extrude to 75% in all directions but 'Z'

7. ### Step 7:

Extrude the second 15 degree section to 95 mm

8. ### Step 8:

Scale this body to 50% in all directions but 'Z'

9. ### Step 9:

Hide the "Pattern Geometry"

Resulting bodies thus far:

We now have 3 sections with associative orientation and displacement in 'Z'

10. ### Step 10:

Create a Through Curves feature; section 1 is the base profile, section 2 is the edge curves of the 1st (45 mm) scaled body, section 3 is the edge curves of the 2nd (95 mm) scaled body.

Tip: The selection order is important; you want the same start curve & direction in each section. Using the Connected Curves filter, look to "options" and select Chain Between. This will allow automatic chaining after selecting a few curves.

11. ### Step 11:

Remove reference bodies from Reference Set and hide bodies

12. ### Step 12:

Final solid body

13. ### Step 13:

Test associativity:

Edit User Expression/angle_sections to 25 degrees and the resultant change; all sections are associative.