Sweep instability

[SWISGR8]

I have helical torsion spring part with of course a helix-driven sweep as the base. It has a straight "tang" on one end and a formed "tang" at the other, both sweeps are off the base helix. The formed tang is on the end opposite the beginning of the helix curve and uses a 3D sketch for path. Basically, to simulate the relaxed and tensioned states, I use configurations which have an angular diff of no more than 30-40deg. Sometimes they switch perfectly, but sometimes it loses the formed tang in the process and has this error:

"Warning
Formed tang FORM 3D sketch
A solution cannot be determined for this sketch. Consider: o Moving the sketch closer to the desired solution by dragging or changing dimension values.
o Adding more dimensions or relations to further define the sketch.
o Changing the dimensioning scheme."

If you look at the sketch that it doesnt like, it doesnt look like it's moving like it is supposed to relative to the end of the helix, but of course when the switch is ok, it does.

I've even had one of the same exact configurations that failed, work when I gave it a new name (with same exact parameter values in the design table - I'm positive they were exact other than name). Any ideas on this? I realize SW seems to sometimes have problems when sketch planes and/or sketch-referenced planes move or shift (as they do here with the varying helix end position, but there's got to be a way to get more stability. Like I say, sometimes it works w/o a hitch and then other times forget it. Very tough to make documentation when this is the case. Also, I've tried to make multiple configurations to slowly approach the new configuration values instead of a sudden jump and possibly leaving it confused, but that was not sure-fire either.

Any ideas, anyone? I've tried to simplfy things as much as I can in terms of reference planes etc, assuming that would help keep SW calculations from getting hosed.

 

[handleman]

Can you post the file?

-handleman, CSWP (The new, easy test)

 

[TheTick]

I've done a few torsion springs. Sketches for the arms on the moving end can lose their way. My solution was to create a surface and use the surface edge as the sweep guide. The moving arm is then rotated by moving the surface.

Example: "TorsionSpringByTheTick.zip"

http://www.esoxrepublic.com/models/

If I were to redo this model, I would use "Move Bodies" ("Move/Copy") to rotate the arm instead of using a pattern. Also, I would clean up surfaces at the end using "Delete Bodies".

Honesty may be the best policy, but insanity is a better defense.

http://www.EsoxRepublic.com

-SolidWorks API VB programming help

 

[TheTick]

p.s. There is also a barrel-shaped torsion spring in "Hinge.zip"

 

[SWISGR8]

Thanks both,

Handleman, did that once as a picture, is that what you mean? Either way, I havent done that in a while either so can you give me some quick and dirty pointers on posting?

 

[handleman]

Use the "Step 3 Attachment" just below the text entry area to upload your .sldprt file to engineering.com.

-handleman, CSWP (The new, easy test)

 

[SWISGR8]

Does this work?

 

[SWISGR8]

Thanks, guess I didnt look too carefully. I sent an edwg, rather not send a part if not needed, but I realize edwg doesnt show much other than the desired result. I use a lot of planes in an effort to keep things as unambiguous, but my understanding or intent could be wrong. I figure SW must keep track of planes in a 3D ref frame i.e. 2D plane with a positive normal direction based on its defining parameters (sketch entities, etc) and their relative locations.