topic Re: Constraints using arcs in Fusion Support Forum

Constraints using arcs

jbasiago — Thu, 26 Nov 2020 21:32:12 GMT

I'm creating sketches that have arcs defined tangent to a line, but sometimes, the geometry does not resolve, yet if I add constraints, Fusion complains that the geometry is over constrained. Here are two identical sketches that have identical constraints and dimensions, yet one resolves and the other does not. I've attached the project file for you to look at as well. It seems to be related to the order in which the geometry and constraints are applied, but for the life of me, I can't figure out a pattern. This is a simple situation, but it gets very annoying when the geometry gets more complicated and then seems to fail. Thanks for your help.

Geometry does not resolveGeometry does resolve

Re: Constraints using arcs

TheCADWhisperer — Thu, 26 Nov 2020 23:05:47 GMT

I am not at my Fusion machine to check the file, but it appears to me that there is an extra = constraint that should not be needed.

Re: Constraints using arcs

jbasiago — Fri, 27 Nov 2020 16:53:23 GMT

Thanks for looking. There are only two equal constraints in each drawing. There is a vertical and a horizontal constraint as well. Then there are three dimensions. I believe all of the constraints are the same, but I could be wrong.

Any help appreciated.

Jack

Re: Constraints using arcs

g-andresen — Fri, 27 Nov 2020 17:15:59 GMT

Hi Jack,

The reason for this is that the constraint in the centre of the arc is lost (white dot) when the sketch is made.
In the screencast I reconstructed a procedure how to clean it up again.
Probably there is an irritation because the centre of the arc and the connection of the two lines (5 in) meet in one point.

günther

Re: Constraints using arcs

jbasiago — Fri, 27 Nov 2020 18:27:29 GMT

Gunther,

Thanks for finding the issue. This seems like a bug to me, but I understand Fusion is looking for a different way to constrain the arc. I used the two lines to constrain the diameter and angle of the arc, when I probably should have used the one line to constrain the diameter and the arc angle to constrain the angle. I just approached it the wrong way. But it still seems like Fusion should recognize the geometry as a proper constraint. I guess there are right and wrong ways to do things in fusion.

Thanks again.