15-Moonstone

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Looking for a specific type of Rotational Equation Curve

Forum|Forum|1 year ago
May 15, 2024
5 replies
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I have successfully used a specifically sized flat Equation curve in my die designs. I have on a number of occasions however needed to use the same radius and spacing around a rotation which to this point have been very fudgy.

Below is the equation that I have been using.

This results in a curve like the following.

Would it be possible to make an equation curve to the below shape?

The spacing would be the same as with the top example but I would somehow need to be able to define a center or slope. Can this be done?

General

Best answer by kdirth

If you are looking to follow a true radius, I agree with @KenFarley that a cylindrical equation may work well:

You may also want to consider using construction geometry to get the desired path: Create a curve for the sine wave to follow. Create a surface sweep using relations to create the sine wave around the curve. Use/copy edge of surface.

kdirth

21-Topaz I

Are you looking for something like this:

There is always more to learn.

P

pimm

Author

15-Moonstone

Kdirth: This is a very nice arithmetic style curve but unfortunately not what I'm trying to achieve.

What I am looking for is a curve that doesn't have any 3 dimensional depth. The rotation that I am looking for above would be similar to taking a cross sectional slice of a Recess Peanut Butter Cup. (The rotation I have been looking for would be on the same 2D axis.)

P

pimm

Author

15-Moonstone

Kdirth: Would it be possible to share a file of the construction example that you show above?

I might have trouble loading the file if it is after Creo version 7 but I at least would like to ask.

I am trying to step by step replicate this example but it appears that your sweep feature feeds the relation and I can't follow how the sweep was created.

Thank you!

Paul

tbraxton

22-Sapphire II

You are looking to superimpose a periodic function (sine/cosine) on a circle? Something that would look like this?

P

pimm

Author

15-Moonstone

Tbraxton:

Yes; in the same orientation of what you show. The challenge would be in keeping the inside radii the same as the outside radii and also maintaining a uniform spacing.

tbraxton

22-Sapphire II

This is possible to do in Creo using curve from equation functionality. The parametric equation (cartesian coordinates) of the picture I posted above is:

K

KenFarley

21-Topaz II

Have you looked into using cylindrical equations (r, theta, z) instead of cartesian? It might make the mathematics more straightforward.

tbraxton

22-Sapphire II

This gives you direct control of parameters in a single feature. Getting the syntax of the equations is the only tricky part to this. Amplitude, frequency and radial offset of the zero-amplitude circle are defined in the equations shown here in Creo syntax. You should be able to cut/paste this into your curve from equation feature definition. Make sure to set the domain of t from 0 to 360 (degrees) to cover a complete circle. 0-180 for half circle.

x=(1.5+0.5*sin(20*t))*cos(t)
y=(1.5+0.5*sin(20*t))*sin(t)
z=0

Curve from equation in cartesian system: