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CAD tip CAD tip # 9038:

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Q - question

Double helix - twisted pair in Inventor

A - answer The Equation Curve function (parametric 3D sketch) can be used also to generate double helix (helix on helix), e.g. to make a model of a twisted-pair cable.

An example:

To model such assembly, just use the function "Equation Curve" (3D Sketch > Draw > Equation Curve) and then Sweep (3D Model > Create > Sweep) of a circular profile along this curve.

Fot the equation curve, use e.g. the following parameters:

x(t) = cos(1 rad*t*PI)*100+cos(1 rad*t*PI)*5*cos(10 rad*t*PI)
y(t) = 5*sin(10 rad*t*PI)+80*t
z(t) = sin(1 rad*t*PI)*100+sin(1 rad*t*PI)*5*cos(10 rad*t*PI)
tmin = 0 ul
tmax = 6 ul

In the equations, the value of "10 rad" represents the number of wire twists per each loop of the helix, "80" is the pitch (height) of a half-loop of the helix, "100" is the radius of the helix, "5" is the wire radius.

Using this 3D sketch and sweeping of a circular profile (2D sketch) perpendicular to the curve you can make one wire. The second wire (with different color) is only rotated and offset. The rotation angle is 180/"twists per loop" (here: 18) and the offset in the Z axis is "half-loop pitch"/"twists per loop" (here: 8).

Similarly you can create also other types of 3D models, e.g. cooling pipes, etc.

100% *  CAD 
17.1.2013    2677x  
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applies to: Inventor 2013 ·

See also:
Tip 9692:Unfoldable spiral-helix sheet metal in Inventor.
Tip 8832:Bent coil (helix) in Inventor.
Tip 6650:Break curve at all listed distances (stations).
Tip 6537:How to model a 3D thread (screw) in AutoCAD?
Tip 5321:How to model a 3D spiral in Inventor?

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