Circular dependency suddenly appeared?

[nigel76FS8]

Not certain what's going on, but the design of a key I did over the last few days has vanished. I have taken an older model, and turned it as much as possible into one that can be modified via the global parameters ("Change parameters" menu) for future re-use, and I want the design to be parametric, obviously - I'm a locksmith, and these are big old keys that are frequently variations on a theme.

Anyway, the design works, all is well, and so I saved out an STL for the printer, and went away. I then found the STL is too big for the printer - it's a giant key - so I went into the model to tweak the length of the shaft, and suddenly, there's a Circular Dependency error, which left me looking at a blank screen. Rolling the timeline marker didn't help, and nothing else worked, so I then hit Undo about 15 times, until the model came back.

The error:

Error: Circular dependency found: from Collar to Sketch12.
First feature in timeline: Collar
Last feature in timeline: Sketch12
Total 5 features

I understand what it means, I just don't see how it suddenly happened now? It isn't like I'm changing anything that could refer to the stuff further along the timeline. Worse? Changing it back doesn't reset or remove the error. The model disappears!

Also: bug report: the "Copy" button doesn't copy the entire Error. See the (mostly scarily blank) screenshot.

https://a360.co/2JzBdkE is the share link. Password is "Symbad"

[jeff_strater]

@nigel76FS8 - thank you for posting the link to the model.  These cases are of interest to us, so we appreciate you reporting them.  We will investigate this model to see what we can find.  But, if you have any idea of how this happened, we would appreciate information about the last operation you did when this occurred, so we can reproduce it.

[nigel76FS8]

No, that's why it is so odd! The model was perfectly well behaved over several hours of modification and such.

It looks like somehow the program is using a projected reference from the future of the timeline, from the description, but I can't think why that would suddenly happen.

If you can't get it to happen, just go to the first extrusion, and do literally anything, and it'll die horribly.

[nigel76FS8 · Accepted solution]

Ok, I think I've fixed it.

The error was complaining about "Collar", and that referencing something later in the timeline - which it wasn't.

After undoing lots and restarting, etc, I eventually got it to where I could still see the model and then edit Collar. Which is a single circle on an offset plane! Pretty easy to see nothing was wrong with it, Plane 9 was created in the previous timeline step, but I changed the reference plane to another one, then back to Plane 9. It seems to have worked! Note that simply reselecting Plane 9 didn't work - the software was "already using that" and nothing changed, I had to select something else, then come back.

Acid test: Changing the parameter for the overall shaft length in the first extrusion...

Yes! It works!

[jeff_strater · Accepted solution]

glad you were able to fix the issue.  I did a little digging, and, as you've discovered, the problem is in the "collar" sketch.  It contains a projected line that apparently references geometry from the future:

deleting this line seems to fix the cycle, as shown in the screencast below.  But, my question is:  how did that line come into existence?  Do you have any idea?  Did you reorder any features in the timeline while you were working?  Any memory you have that can help us would be appreciated!

[nigel76FS8]

Hi Jeff, 

Sorry, no idea! No, I don't think I did reorder the timeline, but it is possible. 

Thanks for the help. 

[zhuravliki]

It happened to me multiple times. It is very annoying Fusion 360 bug:

When Fusion becomes busy for different reason (auto-saving, calculating, redrawing...) any click on any timeline element causes this element, and everything related to it on the timeline, disappearance. Then, 'Circular Dependence' error pops up. I have no idea why left mouse click on the timeline causes the deletion of the elements or features, but it happens to me three - four times a week. It does not affecting simple models just because the Fusion actions delay is very short on them, and it is very hard to hit timeline element exactly at the same time. For the real models with multiple bodies and not 'just two spheres and one cubic' geometry, Fusion freezes for 5 - 15 seconds every five minutes for performing auto operations. It is very easy to click on the timeline element exactly at that time and create the mess in your model. Undo helps sometimes in such cases, but most of the time you need to close the design without saving and reopen it again. You will be lucky if you save the normal copy recently.

It is very frustrating Fusion 360 modeling, with enabled timeline, flaw.