topic Re: All black sketch but not fully constrained. in Fusion Support Forum

All black sketch but not fully constrained.

msecco — Sat, 25 Jul 2020 15:19:24 GMT

Is this sketch fully constrained?

Hide constraints to clarify:

All lines are black, but:

Angle dimensions are missing:

Inventor exemples:

Re: All black sketch but not fully constrained.

g-andresen — Sat, 25 Jul 2020 17:05:02 GMT

Hi,

please share your design to take a look.

günther

Re: All black sketch but not fully constrained.

msecco — Sat, 25 Jul 2020 17:16:47 GMT

hI.

https://a360.co/2D6196m

Re: All black sketch but not fully constrained.

HughesTooling — Sat, 25 Jul 2020 17:26:34 GMT

Here's what I get in my old copy of Alibre. I always liked their use of 3 colours for DOF feedback.

Mark

Re: All black sketch but not fully constrained.

msecco — Sat, 25 Jul 2020 19:59:16 GMT

Hi @HughesTooling

It is a very good idea.

I never liked this too:

Re: All black sketch but not fully constrained.

wmhazzard — Sun, 26 Jul 2020 02:50:03 GMT

@msecco In your case from what I was told by Autodesk, they consider a line constrained if it has two constraints on it, say starting at the origin and having a vertical or horizontal constraint on it. They do not consider the end point of the line part of the line so the length of the line has nothing to do with fully constraining the line. I, and I think many others find that ludicrous but that is the way it is. I think some of the sketch constraint problems relate back to that faulty logic.

Re: All black sketch but not fully constrained.

professor.secco — Mon, 03 Aug 2020 00:35:27 GMT

And it is worse than I thought, the sketch icon also says that it is fully constrained when it is NOT!

Re: All black sketch but not fully constrained.

TrippyLighting — Mon, 03 Aug 2020 16:14:42 GMT

After some experimentation, it looks to be the culprit is the mirror constraint.

Of course, mirroring an entire sketch is also not a recommended practice in any CAD software, but that might be beside the point.

Re: All black sketch but not fully constrained.

msecco — Mon, 03 Aug 2020 17:08:07 GMT

@TrippyLighting Only Fusion 360 has this problem.

I tested (and asked to test) this with Inventor, Onshape, SolidWorks and @HughesTooling tested with Alibre, all of them show the sketch not fully constrained, evem when mirrored.

@wmhazzard said, that for autodesk, a segment with two restrictions is considered constrained. When mirroring, a symmetry constraint is added at each point in the sketch. Thus, all segments are mistakenly considered restricted in Fusion 360.

If remains a single point with some degree of freedom, the sketch cannot be considered completely restricted.

Re: All black sketch but not fully constrained.

TrippyLighting — Mon, 03 Aug 2020 17:14:36 GMT

@msecco wrote:

@TrippyLighting Only Fusion 360 has this problem.

Yep, no surprise. I don't mean that derogatory in any way. Fusion 360's sketch engine is very new compared to the sketch engines in other software packages.

@msecco wrote:

If remains a single point with some degree of freedom, the sketch cannot be considered completely restricted.

Agreed!