unable to get a pierce relationship

[Scarecrow]

Hi there,
this is really frustrating me in two ways:
I don't understand why it won't show a pierce relationship.
Why I can't figure it out myself.

Here's a very simple sweep:
two guide curves starting on the front and right planes.
One profile in the shape of an ellipse drawn on the top plane.
While selecting the profile and then the start point of one of my guide curves I am only offered a co-incident, horizontal and vertical relationship. Can anyone tell me why the pierce relation is not showing as an option?? Clearly I'm missing a very basic piece of knowledge here.

THanks

Gerry B

 

[Theophilus]

Gerry,

Normally you should create the guide curves before the profile. This is so the guide curves actually intersect the plane you create your profile sketch on. However, the simple way to make certain you always get the pierce relationship to function is to create a plane on the end of your guide curve.

To do so, select the point at the end of your curve, then control-select the curve itself (or the near segment of the curve). Add a plane perpendicular to your curve, and place your profile sketch on that plane. You will be able to pierce your profile to your guide curve this way. For multiple curves, make sure the other curves truly touch/intersect the profile plane and they can be pierced as well. (It's best/most-stable if the other guide curves' ends perfectly coincide with the profile plane.)

Hope that helps.




Jeff Mowry
Industrial Designhaus, LLC

http://www.industrialdesignhaus.com

 

[TheTick]

Pierce is used to constrain a sketch point to the point where a curve or edge not contained in the sketch crosses through the sketch plane. If the outside curve does not cros the sketch plane (i.e. falls short) or is coplanar with the sketch plane, then pierce will not work.

If the ladies don't find you handsome, they should at least find you handy.

 

[Arlin]

> While selecting the profile and then the START POINT of one of my guide curves

Pierce relationship requires you to select the guide CURVE itself and not the 'start point.' Note: As Tick mentioned, the guide curve must intersect or end on the sketch plane of you profile.

 

[Scarecrow]

thanks to all who replied. I spent a good deal of time on just figuring out why and how the pierce relation works, and I do have a much better grasp on it. Although it still seems like a bit of black art in some instances.

More on this later as much part progresses.

Cheers

Gerry B

 

[TheTick]

I reread your original post to try and get a better idea of what you are doing. It appears you are working in reverse w.r.t. guide curves and profiles.

Typically, one uses pierce to constrain a point in a profile sketch to to a guide curve. That way, the point in the profile follows the guide curve as it moves along the guide.

It appears that you are doing the reverse, attempting to constrain a point in a guide curve to a curve in a profile. While this may be possible as far as sketch constraints go, I doubt it will give you the effect you are seeking once you go to make your feature.

If the ladies don't find you handsome, they should at least find you handy.