# Creating a Helix

This task shows the various methods for creating helical 3D curves, such as coils and springs for example.

Open the Helix1.CATPart document.

1. Click Helix .

 The Helix Curve Definition dialog box appears.
2. Select a starting point.

3. Select an axis.

4. Set the type parameters:

• Pitch: the distance between two revolutions of the curve
You can define the evolution of the pitch along the helix using a law.
1. Click the Law... to display the Law Definition dialog box.
 The 2D viewer enables you to preview the law evolution before applying it. The Law Viewer allows you to: visualize the law evolution and the maximum and minimum values, navigate into the viewer by panning and zooming (using to the mouse), trace the law coordinates by using the manipulator, change the viewer size by changing the panel size reframe on by using the viewer contextual menu change the law evaluation step by using the viewer contextual menu (from 0.1 (10 evaluations) to 0.001 (1000 evaluations)).
2. Choose type of law to be applied to the pitch.
It can stay Constant, or evolve according to a S type law.
 For the S type pitch, you need to define a second pitch value. The pitch distance will vary between these two pitch values, over the specified number of revolutions.
3. Click OK to return to the Helix Curve Definition dialog box.
• Height: the global height of the helical curve, in the case of a constant pitch type helix
• Orientation: defines the rotation direction (clockwise or counter clockwise)
• Starting Angle: defines where the helical curve starts, in relation to the starting point.
This parameter can be set only for the Constant pitch only.
5. Set the radius variation parameters:

 Taper Angle: the radius variation from one revolution to the other. It ranges from -90° to 90° excluded.  For a constant radius, set the taper angle to 0. Way: defines the taper angle orientation. Inward: the radius decreases Outward: the radius increases. Profile: the curve used to control the helical curve radius variation. The radius evolves according to the distance between the axis and the selected profile (here the orange curve). Note that the Starting point must be on the profile.
6. Click Reverse Direction to invert the curve direction.

7. Click OK to create the helix.

 The helical curve (identified as Helix.xxx) is added to the specification tree. Parameters can be edited in the 3D geometry. For further information, refer to Editing Parameters.