Constrains direction flipping with change of Parameter

[Anonymous]

Sometimes when I change a parameter or other part a fully constrained sketch will fail because an arc or line will flip relative to something else. For example if a line is tangent to a circle in a sketch but a changed parameter rotates the sketch it can resolve with the line tangent to the wrong side of the circle. I know it is because some constrains can have two valid solutions or are binary. Is there any way to fix fully constrained sketches with binary solutions or at least a trick to avoid making them? 

I know adding constraints lowers the degrees of freedom until it is "fully constrained" at which point with given dimensions there should be only one solution the shape can solve to. From that state no points can move but some constraints are binary and there can be two or more possible fixed states. Usually with changes in the dimensions or parameters and the sketch solves the way you expect but sometimes it finds the other fixed state you don't want. I think it happens more with rotations of things and bigger changes in parameters. 

Does anyone else run into this problem or have any advice?

[davebYYPCU]

Only to say if you give Fusion 2 choices to pick from, you will get disappointed more often, than not.  There will be a set of constraint / dimensions, to remove the choice, and prove only one outcome.

Might help....

[chrisplyler]

I feel your pain. Sometimes it's easy to figure out, sometimes it's not so easy.

Try adding a construction line or other construction geometry, that is itself constrained, in such a way that will force a single solution out of the otherwise possible two solutions.

[mihai.stanimir]

This is my main challenge with Fusion as my designs rely heavily on parameters and changing the overall dimensions of whatever I'm building. I have to resort to all sorts of hacks and workarounds that slow me down considerably. It's many hundreds of hours lost on this problem alone over the years. I wish Fusion attempted to preserve the general sketch layout where possible instead of flipping things. Most of the time the solution is to just slide the sketch left or right by some distance (or half the sketch, but I'd be happy with just the full sketch translation).

[MichaelT_123]

Hi Fellows,

This issue started at the interception of F360, where original algorithms were (re-)created.

FOR SOME REASON, the TF360 abandoned basic dictums of general algebra. In this particular case, the problem is that they have despised "sign". There are also other very fundamental deviations from topological axioms causing parametric model breaks.

The foundation of core algorithms process "Gone With The Wind" ... now only smell wandering around.

There is not possible to change the past; rebuilding the F360 kernel would be distractive and costly. So, there is only one solution at your disposal, ... open the window, take a deep breath, turn around diligently, and find a different ... breeze.

Solved: Dimension ZERO - Autodesk Community - Fusion 360

Regards

MichaelT