Don’t give up on Fusion’s circle constraint


Does anyone recognize this? If you don’t then you have not been trying hard enough.  Fusion is fun, but it is VERY picky. The Circle Constraint does not agree with me. While it is aggravating, Fusion offers well more than enough to compensate.  So the trick is to find out what it wants, so we can reap the benefits.


Pesky center constraint

I was preparing for two more videos, and figured this constraint problem out.  I wanted to constrain a hole to be centered on a curved edge, like the image above.  This procedure has always been hit or miss, and did not want the video capturing me beating the keyboard in frustration for 5 minutes.


The constraint is picky about the method the curve was created, and also the ORDER you pick the features in. These are the 3 methods I will discuss:

  • Hole – Curve – Swap Anchor (Failure)
  • Curve – Hole – Accept (Success)
  • Hole – Fillet – Swap Anchor (Success)

Hole – Curve – Swap Anchor (Failure)


I took the original part, sketched a circle, and pulled it to form the curved surface.  Then attempted to constrain the hole to the curved surface, and anchor to the curved surface.  As discussed this as a big failure.  It has failed over and over in numerous parts.


Curve – Hole – Accept (Success)

    What was equally frustrating, is that it would work sometimes.  Well, I thought it would.  The ORDER was wrong.  In the following image I referenced the curved surface FIRST and then the hole LAST.  Seems to work every time.


Hole – Fillet – Swap Anchor (Success)


I also noticed that the issue did not arise when the curve was a result of a fillet feature.  So here I whacked the curve off and added a Fillet to both corners.


Once again I repeat the procedure from before. I pick the hole, then the Fillet curve, swap the anchor to the Curve, and poof.  The hole updates like it should.


It appears as though the problem stems from the constraint being confused with the sketched geometry coming at it last. I think this only happens with holes, and not extrudes.

So the selecting holes last might be the safest bet, so that the anchor does not have to be swapped.  I’ll let you know if I find more info.