disable sketching auto constraints?
"But seriously, Attach a file here that requires removing sketch constraints.
Unless you are doing artistic work (I always use the example of a Maple Leaf with my students) I can't imagine why someone would not want auto-constraints. You can scrub force the constraints that you want."
Reviving a dead thread, but try the following..
I would add a video if I knew how, but I'll just add steps:
1. Using the line tool, draw 3 lines (not dimensioned) to make a right triangle, and then add a center-point-circle to the vertical leg (not on the center of the line)
2. use the move tool to move the vertical leg.
expected result: the vertical leg and circle move while the horizontal leg and hypotenuse stretch.
actual result: the sketch of the triangle scales larger moving to the right and shrinks moving to the left. (?)
3. delete all auto constraints and manually constrain the triangle points with coincidents.
4. use the move tool to move the vertical leg.
expected result: same as previously but leaving the circle behind.
actual result: it works! now to get the circle in there...
5. undo move
6. manually constrain the center point of the circle to the vertical leg with a coincident.
7. move the vertical leg like before
expected result: same as the original
actual result: the entire sketch moves. (?)
8. delete the circle coincident and replace it with a center constraint.
expected result: same as original
actual result: it works, and what should have taken 5 seconds only took me 15 minutes.
This is just one example of the many frustrations of fusion 360 constraints, and it makes design incredibly frustrating during the rough out stages. Perhaps if you are replicating a dimensioned layout or using measurements taken from an actual object it comes in handy. Also this idea that you should draw lines slightly skewed to avoid the auto constraints is not what should be expected in a precision cad design tool. More work to avoid a flawed system.
"If you don't want it to happen, you've just got to learn to sketch in such a way that it doesn't happen."
This is not a case of too many dimensions/constraints, but too few. You have a VERY under-constrained example here. Under-constrained systems are free to react to any change (move, drag, adding a dimension) however they want. There is no "right" answer here. What you are seeing in the sketch is a valid solution to the set of constraints you have given it. The fact that you get your expected result if you do things differently is just luck. Your expected result, and the default result are both valid solutions to the constraint + geometry system you have described. That is all that Fusion (or any constrained sketch system) guarantees.
To get your desired result, you need to fix a point in the triangle. You can do this by using the Fix constraint, or by dimensioning to a fixed location:
This is also why you will see here many recommendations for fully constraining your sketch. That will guarantee that the reaction to any edit is predictable. Under-constrained sketches will be squirrely by their very nature.
Jeff Strater
Engineering Director