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Sketcher lines randomly inverting (Creo 2.0)

sjd

New member
In Creo 2.0 I often use sketches as references for planes. I find it easier to just edit a sketch and let the planes readjust themselves when regenerated. I use the = constraint a lot to control spacings.

One thing I really hate about Creo 2.0 is that a line with an = constraint on it will occasionally flip to the opposite direction. It keeps the correct length but is now facing 180 degrees in the wrong direction. This can then cause havoc to my models!

I know this can happen when for one reason or another the polarity of a plane is switched and so any lines that have been referenced off it will flip... that's fair enough. But it can happen whilst working in a sketch. One second it's fine, then suddenly a line will be facing the wrong way! I have to keep deleting the = constraint, dragging it to the right side and reapplying the constraint.

Anyone else experience this? And more importantly know a workaround to stop it happening?
... Or is it just one of those Creo glitches that you have to live with?
 
I experience this very often, but...these problems do have their own reasons:

1) I create some sketches with references based on surfaces
2) my models are made of surfaces not solids, thus these surfaces tends to change the normal direction(why, when that is a separate topic I do not want to dive into now), and this is the major cause behind discussed problem
3) because I am aware of this issue, all really significant sketches are always placed on datums(problem solved until I change the direction of datum plane which is very rare to me)

it does also happen in VSS, when I use projected curve on the surface which changed the normal direction

anyway, nevertheless it is single sketch or sketch embeded in VSS, you always have a conotrol over orietnation of this sketch, and you should play with this first before its entities do somersault and you are up to change everything manually
 
Thanks for your response!

I try where possible to avoid using surfaces as references in sketches as I am aware that as models are updated and edited they can have a tendency to change their normal direction.

The particular problem I am having occurs whilst I am actually working in a sketch. Surely a reference cannot change it's normal direction whilst I am still in a sketch? I will have drawn part of the sketch correctly, but before finishing the sketch I will notice that some lines (usually ones with an = constraint) will have switched direction but kept the same length. It seems very odd and I am yet to work out exactly what it is that causes the inversion as I usually only notice by chance.
 

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