3D Sketches and constraints

[Fully_Defined]

I am a regular Solidworks user, but I have flirted with Fusion 360 for design for a few years. More for CAM.

I am trying to wrap my head around 3D sketches in Fusion 360, and especially sketch constraints. I want to be able to constrain 3D sketch entities coincident to planes I define in advance; I have argued for the ability to constrain to planes before on this forum, but I was received as someone who doesn't understand Fusion and it went nowhere.

Can someone explain:

1) Where is the 3D sketch button hiding?

2) Once I am in a 3D sketch, how would I project a plane (since that seems to be required) to constrain to it? It seems counterintuitive!

I use 3D sketches a lot in Solidworks for a lot of things, but I'm lost in Fusion.

[Fully_Defined]

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@davebYYPCU wrote:

Just a square on the XY plane, centered on the origin, with legs of equal length perpendicular to the XY plane. Can you walk me through that?

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Now I get what you're trying to do.

If you think you know how to do this specific thing in a 3D sketch, then by all means let me know how you would do it. Earlier you questioned why I would not just do this in multiple 2D sketches, and I guess that's a fair question but it just isn't relevant. I only referred to a small part of the weldment, with the most basic of sketch relations, and Fusion 360 would not behave how I would expect or want. If I can at least solve that, then I could use what I learned an apply it to the rest of the 3D sketch.

[Fully_Defined]

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@jeff_strater wrote:

we're not allowed to mention any dates, but I think that 2020 will be a good year.  It's coming soon.

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Jeff, this screenshot kind of proves you have some bugs to work out.

I took the same center rectangle and deleted the construction lines and center point. I replaced it with three points: two points coincident with the center of two sides, and a center point horizontal and vertical to either.

I then dragged the whole thing to the origin and voila. I can't think of a good reason why this same thing wouldn't work with a center rectangle.

[therealsamchaney]

Hi @jeff_strater , is there any update on new constraints for 3D sketch? Primarily I would love to see the following:
-Ability to constrain points to be coincident to a plane

-Ability to constrain lines to be a certain angle to or parallel or perpendicular to a plane

-Ability to create construction planes from within the sketch environment based on the lines and points that exist in that sketch

These constraints would make 3D sketching extremely useful for many things including creating rails for complicated lofts, and creating complicated shapes like polyhedra (and being able to control the relationships between all of the edges and faces parametrically).

Thanks!

-Sam

[bwnicholspe]

Yep the August 2021 iteration of 3D sketching still leaves something to be desired, in terms of significant workflow ambiguity for reliably constraining a 3D sketch, which after three days of head-pounding, still remain an elusive mystery to me.

1. There seems to be an implied sketch plane that needs to be respected. In the example shown, when constraining the legs of two rectangles, one from the XY plane and the other from ZX along a common line (in this case the x-axis) it's seemingly a crapshoot which plane the perpendicular constraint lands on, and which line out of 4 possible candidates it's actually referring to. Further, to my knowledge, it is not possible to deterministically evaluate which pair of entities are bound by ANY sketch constraint.

2. Often after a 'sketch is over-constrained' error, ALL 3D sketch constraints become unselectable and the only recourse seems to be restarting the sketch-edit session. 

3. Inscrutability, simple polygons, even on the XY plane, become impossible to completely constrain as verified by turning black,  DESPITE all line & point entities being IMMOVABLE via either dragging or the move command. And yes, I am CERTAIN that all entities are on the XY sketch plane!

As much of the pain it is to overlay 2D sketches using construction planes, workflow disambiguation still seems well-worth it at this point.

Prove me wrong, please, as this feature would be a real timesaver! 

[TheCADWhisperer]

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@bwnicholspe wrote:

Prove me wrong, please, as this feature would be a real timesaver! 

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Please Attach your file here.

It probably would have been best to start a new discussion thread with a link back to this one for reference.

[bwnicholspe]

UPDATE: Turns-out two or three of the points at the corners of the rectangle were NOT constrained along the Z axis -- discoverable only by selecting the points and vigorously agitating with the MOVE command. Suggest perhaps a 'Check Constraints' utility highlighting ALL entities (including points) which are NOT fully-constrained, or some visual cue in the UI indicating that segment endpoints are unconstrained.

But I stand by my comments that

1) It is not always possible (yes, now I see the color-changing on-hover behavior) to determine which pair of entities are bound by a constraint, particularly COINCIDENT constraints. By extension, it sure would be handy to be able to EDIT a constraint and thereby change one of the bound entities without blowing it away and starting-over, which may or may not entail first determining the implied sketch plane it was drawn upon.  And...

2) Constraints selectability mysteriously goes dark, requiring a restart of the sketch-session.

Lastly a pedagogical observation, when starting out with 3D sketching it seems prudent to limit the types of constraints used. Perpendicular, coincident,  horizontal-vertical, co-linear and dimension will take you pretty far on orthogonal projects. Master a couple of simple orthogonal say tooling or backyard designs to get a feel for capabilities and limitations.  

[bwnicholspe]

Thanks, good idea, but I'm bagging 3D sketching till the next go around of improvements. Just spent another six hours of head-pounding and basically dead-ended with unresolvable constraint errors.

While the concept of having a single 3D sketch is appealing, I've found in its current iteration even relatively simple orthogonal 3D sketches quickly become unreliably unconstrainable.

Which is contrary to the 'free advice' given for when to use 3D sketches, i.e. 'use for lofting and complex surface definition' yada yada. But if the code as it stands can't reliably, efficiently and predictably handle an orthogonal 'backyard project' case, I don't have a great deal of confidence that it's gonna perform to my satisfaction on the machine designs I have queued-up in the pipeline.

Really thinkin' I need to give Inventor a test drive…