Formula to define the radius of a helix

[chrisb99]

Hi,

I'm trying to define a helix using an equation to define the radius.

Siemens online help isn't spectacular and I haven't found the menus very intuitive.

Can anyone offer any guidance?

Thanks

Chris

 

[MickyV007]

Have a look at attachment...

Best regards,

Michaël.

NX7.5.4.4 + TC Unified 8.3
Win 7 64 bit

 

[chrisb99]

I know the radius relative to the angle (decreasing radius, 7 pitches in total) and can work out x and y rules from this.

How do I enter that into a law curve? I keep getting 'Expression does not exist for law'

Thanks

 

[PSI-CAD]

Hi Chris,

Which NX Version are you using ?

Regards
Didier Psaltopoulos

http://www.psi-cad.com

 

[chrisb99]

Using NX7.5

Thanks

 

[cowski]

To use law curves, you need an expression named "t"; this will be used as the parameter in your parametric equations. Create a new expression:
[ul][li]Type: Number, constant[/li]
[li]Name: t[/li]
[li]Formula: 0 (zero)[/li][/ul]

Since you have worked out other values in terms of the angle, you may want to enter a few helper expressions:
[ul][li]Type: Number, constant[/li]
[li]Name: turns[/li]
[li]Formula: 7[/li]
[li]Type: Number, angle, degrees[/li]
[li]Name: angle[/li]
[li]Formula: turns * 360 * t[/li][/ul]

When NX evaluates your law curve, it will automatically vary the parameter t from 0 to 1. Your other expressions will be evaluated accordingly (angle will range from 0 to [turns * 360]). You can now write your x, y, and z expressions in terms of the angle.

www.nxjournaling.com

 

[JohnRBaker]

Whatever approach you undertake, if there's any chance at all that you're soon going to upgrade to anything newer than NX 7.5, I wouldn't waste a lot of time since the Helix has been completely redesigned in NX 8.0 and virtually all aspects, including Length, Pitch, Radius/Diameter, Start Angle, Origin, Direction, etc., can now be controlled as part of the feature definition itself without the need to write any 'law curve' equations.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[macdacc]

Hi,

Have a look at attachment...
Helix - conical shape created using expressions in NX 7.5

Best Regards