Blend not working where Boundary Blend is

[IbrahimTayyab]

I am trying to create a 3d "shelled" object by blending the outer edges together to form the shape and then blending the inner edges to remove material.

I am trying to create a blend using the references below however it fails to generate.

Using the same references boundary blend seems to work just fine, I am not sure why this is so.

I tried using a circle to circle blend and it worked fine and the wavy to wavy blend worked fine as well.

I have no idea what the problem here is.

By the way would this be called a shelled object or hollowed object or what would be the appropriate term?

I am using creo parametric 9.0 student version

[IbrahimTayyab]

I was able to make the part using boundary blend however I am just interested in wanting to know why blend was not working.

[tbraxton · Accepted solution]

For swept blends note the following restrictions:

•For a closed trajectory profile, one section must be located at the start point and at least one other section at another location.

•Section references at the chain start and end points of the trajectory are dynamic and update if the trajectory is trimmed.

•Section locations can be referenced to model geometry, a curve for example, but modifying the trajectory may invalidate the references. In this case the swept blend feature will fail.

•All sections must contain the same number of entities.

It is not working due to the requirement of each sketch in a blend must have an equal number of entities in the sketch. One entity (arc) exists between each set of 2 x. Your wavy sketch has more entities than the circle sketch. The red x shows the entities in the sketch. You can rectify this by dividing the circle into the same number of arcs and matching the blend vertices.

[IbrahimTayyab]

Thank you very much for the easy to understand explanation and thank you for taking the time out of your day. 👍

[KenFarley]

A question I would have about thinking that this is a correct part : Did you wish to have the tilted transitions from the circle to the wavy profiles?

It looks like the start of the bottom curve (circle) is angularly offset from the start of the wavy curve.

These are some of my concerns when I use blends to create geometry:

(1) As has been stated, the number of entities in the two section sketches must be the same.

(2) The start points of the two section sketches must be explicitly defined to what I want, otherwise you get a "twisty" blend.

(3) When transitioning from two very different curves, the length of the segments in the circle can be adjusted to give very different results. This is something that is especially evident when going from a circle to a rectangular profile.

(4) What kind of tangency requirements do I have to meet at the ends?

(5) Does what I create "seem" like it will be manufacturable, if that's my ultimate intention.

There are a lot of ways to play around with the geometry that a blend can give me. It's a pretty powerful feature creation method.

[IbrahimTayyab]

Hello,
Yes you're right I did not mean to have the tilted transition, so that method does not seem to work well. I have just fixed it by creating it by using blend. Thank you very much for your guidance, it certainly gave me a whole new perspective on how to approach I didn't even think to create different length segments to change the geometry, that was definitely enlightening.

On another note, while creating this, as I divided the circle into 14 segments using divide I found the method I used to be quite tedious. That is creating 15 construction lines and setting the angle of each by hand. Do you know of a way I can speed up this process, as in something similar to the pattern feature but within the sketcher environment?

Thanks for the help,
Ibrahim Tayyab

[IbrahimTayyab]

Came across a video explaining how to do what tbraxton explained, might be helpful for anyone struggling with it.

https://www.youtube.com/watch?v=gJy9AMgnwd4