How to Create a Variable Helix in NX

I was recently asked about how to create a variable helix in NX. You can easily do this by using a variable spring with a variable pitch. What’s the trick for creating a variable spring with variable pitch in NX? Using the Helix, you will need to specify a helical spline along a vector or a spine curve. You can specify law types to define variable pitch (the distance between each turn) and size values.

Note: We will be covering other commonly overlooked functions, like variable helix, at our first-ever virtual edition of NX University–a one-day event covering new features, hidden gems, and best practices for NX Design and Manufacturing users.

You may also control the angle, size, orientation, and length of a helix using on-screen handles.

The resulting helix feature creates a defining By Poles spline which is not displayed in the Part Navigator but which can be analyzed and edited using QuickPick.

This example shows you how to create a helix that will be used to create a spring of varying diameter and pitch. Law functions will be used to define and manipulate both diameter and pitch.

1. Start with Sketch

Using sketch, create three lines and constraint to my specifications and then finish my sketch function.

Use bridge curve command to complete my profile. This profile will be used for Helix Size curves and spine pitch.

Choose Helix from curve tab .

Orientation group, CSYS dialog Select Absolute CSYS.

2. Set Parameters and Law Type

In the Size group, set the parameters as shown. (Watch curve selection in the border bar, fine curves in total.)

Select a law curve to determine the diameter of the helix.

The curvature characteristics of the spline curve are used to define the diameter of the helix, dependent on length.

In the Pitch group, set Law Type to Cubic Along Spine. (Watch curve selection in the border bar, fine curves in total.)

3. Select as a Profile for the Spine

Select the sketch as a profile for spine and click middle mouse button to advance.

Specify a new location anywhere on the spine.

Use the scene dialog or Values along Spine in the dialog box to set the follow options: Point 1= 2mm and Curve %= 0%

Specify a new location anywhere on the spine.

Use the scene dialog   or Values along Spine in the dialog box to set the following options: Point 1 = 5mm and Curve % = 5%.

Specify a new location anywhere on the spine.

Use the scene dialog or Values along Spine in the dialog box to set the following options: Point 1 = 5mm and Curve % = 95%.

Specify a new location anywhere on the spine.

Use the scene dialog or Values along Spine in the dialog box to set the following options: Point 1 = 2mm and Curve % = 100%.

4. Create the Tube

Chose Home tab –> Feature group –> More roll down –> sweep gallery –> Tube.

Select helix curves.

In the Cross Section group, set the following options:

In the Setting Section group, set the following options:

Click OK.

The helical spring is created.

The ends of the spring show the helix has a 2 mm pitch during the first and last 5% of the spine, then a 5 mm. Pitch for the rest of the helix.

Voila! You now have a variable helix. Enjoy!

For more tutorials like our variable helix NX CAD tutorial, check out our library of articles.