Blend twists and turns for no reason!

[mrubino]

I'm looking for some expert advise or a tutorial on blending. I'm using Blend Protrusion on a complicated shape using multiple sections, after the 3rd section the blend has a mind of it's own and starts to twist whatever way it wants. I can also see this twist starting in the 2nd blended section. I made sure all the arrows are facing in the same direction but this doesn't seem to help. Is there a better way? In I-Deas and NX I used Lofting is there something like that in Creo?

Thank you!

[Patriot_1776]

You have the option to rotate the section in relation to the last section in swept blends. Not sure what command you used.

[sschroeder]

A surface boundary blend is like lofting. If you create your sections first, then you can use the "boundary blend" function to drive a surface through the sections. You can add control points and cross curves to control the "twist" if needed. When finished you can "solidfiy" the surface into a solid.

[mrubino]

I'm figuring out how to use "Boundary Blend" command per your previous recommendation and created a simple blend but now I'm trying to figure out how to "solidify" the surface into a solid. Is this a command that I just can't find or is part of a previous command?

Also is there any information or tutorials on these operations?

Thanks,

Mike Rubino

[BrianMartin]

Do you have a screen shot of what's happening? Blends are usually not difficult to figure out. When you get into Swept Blends and Variable Section Sweeps with multiple trajectories, that can start giving odd twisting motions that require additional constraints to fix.

For a blend, it if't twisting, check your start points. You said you made sure the arrows in the sections were all facing the same direction. That's good... but you also have to make sure the start points are in the same relative location and that you have the same number of points in each section. If you do not have the same number of sections, you'll need to add one or more Blend Vertices to make up the difference.

I've never seen a simple blend misbehave when these guidelines are followed... but anything's possible! If we could see a screen shot, I think I could diagnose the problem right away.

Thanks!

-Brian

[mrubino]

Hi Brian, I appreciate you answering my blend question. I'm attaching a screen shot as you requested.

Thanks,

Mike

[bpenza]

Brian,

I've also had problems with twists in simple blends. You mention making sure that all start points are in same position. This certainly does fix the problem. However, I find that once the sections are created, trying to get the start point of each section in the same place can be very frustrating. Is there a very simple way to do this?

Sometimes the start points are easy to drag into position and sometimes they don't. Also, sometimes I've been able to right click and get a menu to appear, but this doesn't always happen.

What is the definitive way to change a start point in a section?

Thanks .

-Brett