Driving joint affects unconnected joints

[Teunsegers]

When setting a joint to a given value it affects several other unconnected joints. This also happens when using the align command. Capturing positions does not seem to remedy the situation.

Note, these joints are all instances of the same component. They seem to adopt an obsolete default value from one the first versions of that component. This value was removed and updates were applied. Even with the old default value in place I would not expect this behavior. Note: This old value is not the "home" for the joint. Idk where it keeps coming from.

Even motion studies can't manage to get everything in line.

How do I line up my components without joining them to the floor (because they aren't meant to be joined there, but they should align with it when extended)?

@mickey.wakefieldany ideas?

[mickey.wakefield · Accepted solution]

Hi - I just got finished with the last issue....

You've got a really large assembly with dozens of rebuild errors and an assembly structure that doesn't seem to correspond to your functional groups.

You did not appear to have a grounded element anywhere in the top level assembly the last time you sent it to me, and your one grounded element was in a subassembly - but remember - a grounded part in a subassembly will no longer be grounded when you move to a higher level....it is ignored in the context of the higher assembly.

You may be seeing seemingly unrelated movements because there may be other joints connecting the parts....sometimes not directly, but through 2, 3 or even more joints. They are all connected. 

It helps to break the problem into manageable pieces by having functional sub-assemblies and adding your joints and motion studies in these subassemblies.

Remember that Fusion 360 is a manufacturing tool. You appear to be trying to use it to do visual animations. While we can do motion studies, their purpose is to test for fit and function of individual motion subassemblies.

[Teunsegers]

Hey Mickey,

I know my project isn't typical. Sorry about that.

I thought I had done enough grounding with that sub-assembly. I have now grounded the component that all those joints hook up to and the behavior has normalized. This solves the problem and I understand grounding a bit better now.

Thank you.

P.S.
"It helps to break the problem into manageable pieces by having functional sub-assemblies and adding your joints and motion studies in these subassemblies."
I did that with all the recurring parts (like those joints are all built separately), the problem occurred when adding them all to the main assembly. I'll try segregation more, but I've found it difficult because most parts heavily build of each other and I need to make cuts in many places across many components.

[laughingcreek]

All sorts of joint behaviour confusion can occur when you have bodies and components living at the same level in the browser hierarchy.  Not generally considered a good practice-

[Teunsegers]

Ok, I did not know that. I'll reorganize those bodies into new components. In this case the issue was caused by poor grounding though.