Create a spiral tube (coil)

Create a surface in the shape of a spiral tube (helix) in order to model objects such as appliance cords or springs.

First you need to model a spiral curve to act as a rail. You then place a small circle or other closed curve at the beginning of the spiral to act as the profile. Finally, you use Swept surface tools such as Extrude or Rail surface to produce the coil.

Create the spiral curve

1. Draw a straight line that has the height of the spiral.
2. From one end of this line, create another straight line, perpendicular to it. The length of this second line should equal the radius of the spiral.
3. Choose Surfaces > Swept Surfaces > Rail Surface .
4. In the control window set both Generation Curves and Rail Curves to 1, and set Rotate Xform to an angle of 360 or more. 360 degrees will produce one coil, 720 degrees will produce two coils, and so on.
5. Select the second curve as the Generation Curve and the first curve as the Rail Curve to create a spiral surface.
6. Choose Curve Edit > Create > Duplicate Curve and select the outside edge of the surface.
7. Delete (or hide) the surface and keep only the curve.

Create the coil surface

1. Place a small closed curve (such as a circle) centered at the beginning of the spiral, and perpendicular to it.
2. Choose Surfaces > Swept Surfaces > Extrude (with Style set to Tube) or Surfaces > Swept Surfaces > Rail Surface (with Generation Curves set to 1 and Rail Curves set to 1).
3. Select the small closed curve first, then the spiral curve.
   

Create a helical shape

1. Create a generation curve and a rail curve. The distance between the generation curve and rail curve is the radius of the helix.
2. Choose Surfaces > Swept Surfaces > Rail Surface .
3. In the Rail Surface Control window:
   • Set Generation Curves to 1.
   • Set Rail Curves to 1.
   • Set Sweep Mode to View.
   • Set the Sweep Projection to the plane to which the generation curve is parallel.
   • Set the Sweep Pivot to Off Curve.
   • Turn on Auto. Recalc.
4. Click the generation curve.
5. A 3D locator appears and you are prompted for the generation curve pivot. Use magnet snapping to move it to the starting point of the rail curve. Then click Go.
6. Click the rail curve.
7. A curve locator appears for the rail curve pivot. Move the locator to the starting point of the rail curve, then click Go.

   The generation curve’s pivot point moves along the rail curve. Since the pivot is offset from the actual generation curve, the generation curve sweeps the new surface at an offset from the rail curve.

8. In the Rotate Transform field, enter the degrees of rotation you want as the generation curve travels around the rail curve.

   For example, if you enter 360, the generation curve makes one full revolution as it travels the length of the rail curve.

   helix curves helix curves active