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Nov 29, 2017
04:07 AM

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Nov 29, 2017
04:07 AM

Datum Curve from Equation - Limits set by relation

Hello,

I am working with a geometry that uses a datum curve from an equation.

Certain parameters can be changed by the user in order to manipulate the curve.

The issue I am having:

Based on the parameters, two relations define numbers A1 and A2 which can limit the curve (see pic.).

Unfortunately, I could not make the curve's limits update when the parameters (and subsequently the relations) are set by the user.

It only worked like this until now:

- Update parameters
- Get failed geometry
- Edit definition of said curve
- Type in "A1" and "A2" which updates the limits
- Get the desired geometry

Is there any way to make this work without having to manually insert A1 and A2 each time?

Thanks!

Solved! Go to Solution.

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Nov 29, 2017
11:11 AM

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Nov 29, 2017
11:11 AM

I would suggest trying this:

* Set limits to 0.0 - 1.0, create "w" parameter to replace t and use relation parameters to set limits.

w = ( t + A1 ) + ( t * ( A2 - A1 ) )

x = 4 * cos ( w * 360 )

y = 4 * sin ( w * 360 )

z = w

This spiral equation worked well for me.

There is always more to learn in Creo.

4 REPLIES 4

Nov 29, 2017
10:34 AM

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Nov 29, 2017
10:34 AM

I would first try to enter the names of the parameters controlling the evaluation limits instead of those values. If that doesn't work then enter 0 and 1 and change the equation to use "T+A1" and "*(A2-A1)" to change the limits inside the equation. ( I think those are right - A1 sets the lower level for evaluation and A2-A1 sets the span of the evaluation.) If you post the equations it may help to see the effect.

Nov 29, 2017
04:53 PM

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Nov 29, 2017
04:53 PM

Thanks @dschenken and @kdirth!

Hadn't thought of an extra variable.

So the following worked (D_CNTCT is the diameter of a circle and I wanted my logarithmic spiral to be limited around this circle)

A1= ln(D_CNTCT-10)/EXP_FCTR

A2= ln(D_CNTCT+10)/EXP_FCTR

**w=A1+t*(A2-A1)**

r = exp(EXP_FCTR*w)

theta = 360*w

z=0

Nov 29, 2017
11:11 AM

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Nov 29, 2017
11:11 AM

I would suggest trying this:

* Set limits to 0.0 - 1.0, create "w" parameter to replace t and use relation parameters to set limits.

w = ( t + A1 ) + ( t * ( A2 - A1 ) )

x = 4 * cos ( w * 360 )

y = 4 * sin ( w * 360 )

z = w

This spiral equation worked well for me.

There is always more to learn in Creo.

Nov 29, 2017
11:22 AM

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Nov 29, 2017
11:22 AM

Allowing relations in the limits fields could be a good idea to suggest.

There is always more to learn in Creo.