Variable Section Sweep Problems

[jdurston]

I am having all kinds of problems trying to create this variable section sweep. (I am trying to cap off the entire end*, but since I have lowered my expectations and trying to do it in parts.) Here, I am just trying to create a surface sweep using the 2 trajectories shown. The result doesn't even come close to following either trajectory. Anyone have any idea what is happening here?


*- This is the butt of a rifle.





Any general suggestions on how to model this. I am trying to convert a facet file to closed surface and then hopefully to a solid. I am happy to send you the file (appears to be too big for this site.)

 

[jsantangelo]

From the picture it almost looks like there are some constraints in the sketch are causing some issues. Post more pics.

 

[design-engine]

a variable section sweep that comes to a point is always a bad idea. Same as using a three part boundary. Just don't allow the trajectories to touch and your VSS feature will work just fine.

There would be possibly four alternate techniques for obtaining the form your looking for.

try these two:

1 sweep over extended then merge
2 use four part boundaries then trim back to look like a three part boundary

Edited by: design-engine

 

[tobbo]

Your problem might have occured when you made your sketch (in your VSS), did you use the"use edge" command? (on a existing sketch or edge?)if so, remove the constrains and try again...


But on the other hand... 4 part boundaries and trimbacks are better...


//Tobias
Edited by: tobbo

 

[gkbeer]

Think of sweeping along the tangent lines instead of along the intersecting corners.
Let the relevant positions of the trajectories change scale the swept sketch anamorphically.


OOPS! the sketch should say
Swept section A-C

 

[jdurston]

I was thinking that it may have something to do with sketch profile as well.


It is most definitely a case where I am using the edge. In this case it's a nearly identical vss on the other side, but the curvature is a little different. I am using edge of the vss on the other side; so, that I can have a prayer of merging the surfaces together later on.





Here's the vss on the left side. This sketch profile is a spline. I tried to make sure the spline was a smooth curve and did not "inflect". Later on, I tried replacing this spline with an arc and a straight line without having any success in fixing the trajectory.





Here's the vss on the left hand side. Everything looks good here.





Here is the sketch profile on the right hand side. I just used edge of the other vss (on the left hand side).





Here is the result on the right hand side. You can see the origin and the other trajectory highlighted, but the sweep does it's own thing.


Iwas beginning to think that the use edge is the issue. It's almost like it wants to follow the curvature on the left hand side.





I tried replacing the Use Edge with a straight line. The yellow path line seems to indicate an issue with the origin path at the base.





It looks like the top trajectory follows a path that comes to point above the end point and bounces off and loops down to the end point The origin trajectory appears to make 270 loop and then a straight line back to the end point.


(Try to ignore the bad vss which is a mirror image issue from the other side of the part.)


I wonder if it just doesn't like the trajectories. (Looks like a bug to me.)


Thanks for your help!


JD

 

[jdurston]

The plot thickens. I opened a call with PTC. The model I sent to them works fine in WF4 M070. I'm on WF4 M040. So, I asked them to open the part in WF4 M040, and guess what. That's fine too. What gives?


I have now sent him the config.pro to see if there is something in there that is causing the issue.


While I was on the call, he suggested trying a boundary blend. I thought you needed 2 curves in each direction. Not so. 1 curve in one direction and 2 curves in the other direction works fine.


I bet you guys already knew this. I am still learning about all this.


BTW, the call is C7063675 in case anyone has similar issue. I am hoping this will at least lead to an SPR or one that already exists for this issue.


Cheers,


JD
Edited by: jdurston

 

[kdem]

From your pictures it looks like your reference selections under the references tab are different for the two sides.

 

[tobbo]

yepp, you can make a boundary blend with 3 curves... but it wont give you any good and smoothsurface!!! so, dont do that ;-) always use 4 part boundaries..and trim back if nessesary.


//Tobias

 

[jdurston]

It turned out that those weird surfaces were a kind of fluke. I reloaded the same part later on and it regenerated fine.


Thanks for all tips!