Equation-based curves in Sketcher 1

[treddie]

Hello.

Is there any way to build equation-based curves in Sketcher. I know how to do this when building a DATUM curve, but it seems odd that ProE does not offer the same functionality in Sketcher (say, when building a sketch from within a Variable Section Sweep). The datum curve approach gives you the option of building the curve by clicking "From Equation". Sketcher does not. And building a relation does not offer the ability to "sweep" out a curve based on the parameter "t" as with the datum curve's "From Equation" option.

The reason I need this is that I have a closed curve that much change shape (or size) according to the value of trajpar when building a Variable Section Sweep. But building a datum curve first doesn't cut it because the VSS can't access the contents of the datum curve to alter it via trajpar. You can only use Sketch > Edge > Use, which means you're stuck with the dimensions of the datum curve as previously built.

The only other option I can think of is to use secondary trajectories for the VSS to follow, but that opens up a whole can of worms, and in my case, a zillion extra trajectories to accurately shape the feature I need. It also means I would have to approximate the original curve by a spline, and this then makes the construction inaccurate and prone to interpolation errors.

Thank you for any responses,
treddie

 

[mburlone]

Treddie,

Have you tried using the equation-based datum curves as pieces of a boundary blend? You can write the equations for the curves after you have made your sweep trajectory. It might help to make a coordinate system for each equation-based datum curve so that the origin of the coordinate system lies on the sweep trajectory.

 

[treddie]

Hi mburlone.

Thank you for replying. I like your idea, but doesn't a boundary blend require 4 edges?. I'll try your idea with 3 for a Variable Section Sweep. I'm concerned, though, that it won't maintain the same proportions of the original equation based curve (the curve that will do the swept); the other two curves being the control curves.

 

[treddie]

mburlone>
NOW I think I see what you're saying. After a conversation over at MCAD Central, I realize I haven't been realizing the power of the Boundary Blend, particularly blending to a point, which I didn't know you could do (I thought the BBlend needed 4 EDGES).

Just tested your idea and it works great!

Thanks for your help!