Constraint engine wrongly complains of overly constrained sketch

[Witsend3486]

Hello,

In the sketch below the constraint engine refuses to set tangent constraints at the left ends of the 21" and 20" arcs saying that the sketch is overly constrained.  To be honest, I don't see any reason for this.  Also, i have successfully drawn this sketch before, so I suspect something in the recent software update may be the cause.

The centers were all located as point elements, the arcs were then drawn as center point arcs, dimensioned, and then connected with lines.  Is the sketch engine automatically adding constraints like the subtended angle of the arc?  Is there any way to turn that off or delete the constraint?  I don't see any constraint markers that I didn't put there.  Is there any way to see all the constrains that Fusion thinks it is working with?  (That would be a useful feature to add if it doesn't exist.)

If I did it right, there is a link to this example sketch at the bottom of the post.

Regards,

Bill

http://a360.co/1zAQnM0

[Anonymous]

I have been fighting unusual constraint issues since the January update as well.  I think there is a glitch in the 2D sketch tool as a result.

[innovatenate]

Bill,

Thanks for reporting this. I note if I delete the dimensions from the arcs and then add the tangent constraints, the constrains will be created successfully. I can then go back and add dimensions (the same exact values). This is probably a bug with the constraint solver. I will escalate this issue to development and circle back here with any information that I discover.

Thanks for taking the time to document this!

[Witsend3486 · Accepted solution]

I did what you said and it worked.  Joy, joy!

Thank you,

Bill

[cekuhnen]

for me those warnings often result into removing the constraints and testing different combinations - kinda a love and hate situation.

[nhfoley]

There is very clearly something wrong with the constraint solver. I am sketcing a simple arc and trying to dimension it, but trying to then move that arc with a dimension causes this error to emerge:

There is nothing else in the sketch or model. I have recreated this geometry several times in new files, replicating the results. When I try to change the dimension circled in red, I get an over constrained error. Trying different numbers sometimes causes the solver to update, and sometimes gives an overconstrained error. There is clearly no non-zero dimension of this line that should overconstrain the sketch.