Sketches flip when part changes

delek_turner

Hey guys, I've been having a problem with sketches tied to part faces (or sketches tied to planes tied to part faces). Sometimes, when a part or configuration changes, sketches on the faces of the part will flip their normal... so for example:

Before the configuration change, this sketch was mirrored so that the dots at the bottom were constrained to the holes at the top, and the square sketch part was flipped over and constrained to the gray part. The constraints all seem to still be intact actually, but because of the flip...


How do I deal with this? It's double annoying because it'll do it on configuration changes so things break when things are modified that way too.

Thanks a ton,
Del

kevin_o_toole_1

My initial suspicion for this case is that if you do a part mirror instead of a sketch mirror, things will behave much better.

Most reasonably sized sketches develop implicit chirality as you build them (this thing goes to the left of this, etc.) which means that sudden changes to the configuration can cause the solver to look for a solution down the "wrong path" and end up finding contradictions. A part mirror, on the other hand, isn't constraint-based, so it's usually much more robust to upstream changes.

If that isn't it, post a link to the public document! Many on the forum here would be happy to help diagnose and solve the issue.

paul_chastell

One thing that can be problematic with large changes of plane angle is that there is no way to vary the 'horizontal' and 'vertical' directions in the sketch so that they change smoothly for every plane change. You may be hitting a jump in horizontal/vertical, which would cause the solver extra pain. If you have a linear edge in the model before this sketch that you could refer to as 'horizontal' all the time for that sketch then you could try replacing all horizontal and vertical relations with parallel/perpendicular to that edge and see whether that helps with the rebuilds.