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## 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:

1. Update parameters
2. Get failed geometry
3. Edit definition of said curve
4. Type in "A1" and "A2" which updates the limits
5. Get the desired geometry

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

Thanks!

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1 ACCEPTED SOLUTION

Accepted Solutions

## Re: Datum Curve from Equation - Limits set by relation

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

## Re: Datum Curve from Equation - Limits set by relation

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.

## Re: Datum Curve from Equation - Limits set by relation

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

## Re: Datum Curve from Equation - Limits set by relation

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.

## Re: Datum Curve from Equation - Limits set by relation

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

There is always more to learn in Creo.
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