Tangent constraint snaps on the wrong side of the line

[ltomuta]

https://autode.sk/3IEFYWB

How can I tell now on which side of the line should that circle snap to?

[TheCADWhisperer]

1. Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

2. It appears that you have Projected a Face rather than just the Edge.  I prefer to Project only that which I actually need.  (I turn off Auto-projection in my Preferences.  I think most of the experts turn this off.)

3. What happens if you turn off the Body visibility?  I am wondering if Fusion isn't projecting a new edge from the Body.  Attach the file here and end all doubt.  (You can get rid of any extraneous stuff first.  Make sure it still exhibits the behavior you showed in video.)

4. What happens if you move the circle closer to Tangent before adding the Constraint?

[ltomuta]

I'm pretty sure I projected the body (five of them actually) and with two of the resulting contours the tangent constraint seemed to work just fine. 

Then I had to rotate the other three objects and the illustrated behavior started to show up after the sketch projection was automatically updated to reflect the new position.

Moving the circle closer to the contour does not help.

[TheCADWhisperer]

Those don't sound like techniques that I would use?

Q1. Are all of your sketches fully defined?

Q2. Are there any unresolved issues highlighted in your timeline?

Q3. Are you using Joints rather than Move/Rotate?

Q4. Why, oh why would you Project a body?

Q5. Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

[ltomuta]

1. Yes.
2. Nope.
3. Yes.
4. I do CAM as my main job and most of my designs revolve around supporting that. In this case I need to EDM the contour of some components and project body gives that contour. Project edges/faces would be a bad idea in this case.
5 I will post a link to a test project if I get some time to clean this up and find a way o reproduce the issue.

[TheCADWhisperer]

@ltomuta 

Make sure you turn off 3D sketching and do not move the sketch off of parent sketch plane. 

[jeff_strater]

what you are seeing is a valid (if undesirable) solution to the instructions you gave it.  You told Fusion to make the circle tangent to the line.  It did that.  This is a constraint system with an infinite number of solutions, and one of those was selected.  The usual answer is to provide the system with some more information (other constraints, or dimensions) to try to force the solution that you want.

Now, having said that, I agree that this result is undesirable, because it forces the circle to move more than is necessary, and the bias should always be towards minimum movement.  If you would like our solver team to look at this, please share the design here, and we can do that.  Perhaps this is a good test case for the solver to improve the behavior.