Mirroring a component breaks its internal joints

[lure23]

I like designing things modular. A component can take care of its internal joints, and upper layers can just "use" it.

However, when I today used "mirror component", Fusion 360 correctly places those copies, but their internal joints no longer restrict the movement. 

Copies fall apart

Looking at this in the browser, both Joints and Sketches in my component's main level are gone:

The missing bits

Is this intended behaviour?  If so, what would be the reason anyone would want this??

[chrisplyler · Accepted solution]

I cannot say whether it is intended behavior or not. Seems like internal joints SHOULD be included. I wonder if the developers just haven't done the work required so that F360 can identify those joints that would work as they are, and those joints that might have undesirable behavior when mirrored. Just a thought.

But I can say this:

It appears in the picture you provided that the assembly you mirrored, and thus the components nested within it, are symmetrical. If that is the case, you could just as easily have copy/pasted the assembly, which WILL included its internal joints. Hope this helps.

[jeff_strater]

@lure23 - your observation is correct.  When you mirror a set of components, or a sub-assembly, the joints are not also mirrored.  The reasons why not are mainly that a mirrored set of components would then require mirrored coordinate systems (left-handed coordinate systems), and Fusions internal joints solver cannot today deal with such reversed coordinate systems.  Perhaps someday this could be supported, but for now, you will have to re-apply the joints in any mirrored set of components.

[TrippyLighting]

I most cases mirroring a components is a bad idea for a number of reasons. One of them it does not allow you to create a proper BOM.

[lure23]

Thanks for the explanation, @jeff_strater 

I can buy that, but think this would be a place where Fusion 360 could warn me, as a user that "if you apply mirror on this component, the internal joints will be lost".  That would have been helpful, since I would normally trust that if there's no warning, there will be no surprises.

Fusion 360 gives such warnings elsewhere. It would also make the user understand this is a limitation, not a bug that needs reporting.

[chrisplyler]

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@lure23 wrote:

...I would normally trust that if there's no warning, there will be no surprises.

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Just playing devil's advocate here.... If you think about Joints and their orientation/location requirements, then it no longer seems like a surprise that a Mirror wouldn't include them.