Cannot "break link" from body to projected sketch

[rnl9t]

I am working on developing a flat pattern for a curved sheet metal part.  Because the shape is mildly complicated, encompasing curved edges, a roughly conical shape, and one crease, it is not possible to do a naive "unrolling."  My plan was to project the body into a sketch, calculate the length along the curve at various points, and then move the sketch points around to reflect these lengths, resulting in a rough pattern that can be taken to the shop and pressed into prototypes for refinement.  My hope was that the curved edges would stretch in roughly the right way--or, at least, more accurately than if I were simply to sort of scribble them on paper.

The trouble comes once the body is projected. The sketch is fixed and nothing can move.  Reading other forum questions, I learn that it is necessary to "break link" so that the sketch objects will be free to move.

Below is a screen cap of right-clicking on the sketch.  There is no "break link" option.  I have also tried turning off Design History, so that ALL parametric links are theoretically broken, to no avail.  I checked and I am using the latest build, Windows 7.

So I have two questions:

1) Narrowly, how do I break the link between a sketch and the body it was projected from?  Why do I not see a "break link" option?

2) Broadly, is there a better way to find a flat pattern?  A way to unroll a curved metal part?  And, since metals typically must be overbent to achieve the right shape, is there a way to curl the part a little more to serve as a model for CAM to make dies?

[Anonymous · Accepted solution]

Hi, as for the Break Link option for purple projected geometry, you need to first actually go into the sketch, by right clicking on it in the browser tree and choosing Edit.  Then you can individually select geometry, or do click and drag to create a selection box (note left to right and right to left dragging has different behavior), and right click to see Break Link if you have indeed selected projected geometry.

I'm not sure of the best way currently in Fusion 360 to make a 2D pattern that is to be formed into a 3D surface.  It sounds like you have a pretty good idea.  I would probably first try and get a feel for the mathematical behavior of the shape with posterboard cutout, if it's not too complex if shape.

Good luck!

Jesse

[rnl9t]

Thank you, that worked, aside from a few points that refuse to be broken free (but can be worked around).

Tomorrow I will have my mill draw this pattern on some paper, and if all seems well, on some sheet metal for testing.

[Anonymous]

Great!  Other issues with points include 1) insuring the geometry is not in another sketch (can turn off visibility via the light bulbs in the browser tree), 2) selecting the point while editing a sketch and right clicking for Delete Coincident, which removes a coincident constraint if present, 3) left clicking and holding the mouse button on the point to get a list of superimposed geometry, and going through checking each superimposed point.

Jesse