assembly - revolute joint parametric rotation angle relative, not absolute

[jhorstink]

In an assembly with two blocks (example attached) I can rotate the second block by parameter, but after the rotation I still can rotate it freely by hand. When I change the rotation parameter again, the movement starts at the current position. Somehow the parametric rotation is relative, not absolute. All other dimensions are absolute, driven by the parameters. I would like to have the rotation absolute, in the 'as built' orientation, or with another reference, but I don't see how to accomplish that.

Using bodies or components made no difference.

Thanks in advance.

[paul.clauss · Accepted solution]

Hi @jhorstink

Thanks for posting! I had a look into this behavior this afternoon and have some thoughts to share.

In your file, you are using a revolute joint, which leaves one rotational degree of freedom. I found that, if I dragged the part some amount, did not Capture Position, and then edited the angle_1 parameter, the rotational movement appeared to be applied from the current position of the model, as you found. In all cases, it appeared that the angle of rotation applied to the joint referenced the current position of the flag that is shown that can be used to drive the joint position.

I believe what is happening here is that the angle_1 parameter applied in the revolute joint is being applied to define the initial alignment of the revolute joint rather than actually defining how much the joint has been rotated. Using a Rigid joint instead of the revolute joint may give the behavior you expect - the angle_1 parameter can then be used to drive the actual rotation (or current angular position) of the rotating component without interference from the current rotational position of the revolute joint.

I have shown this in the screencast below - please feel free to reach out if you have any questions!

[jhorstink]

Hi @paul.clauss,

Thanks for your answer and indeed, the rotation angle is really used as a parameter now. Looking back it is logical, it is already in the name of the joint. A revolute joint can rotate freely, it is quite different from a (parametric) angled rigid joint. The same applies when using a slider joint, you can change the distance with a parameter, but after that you can still slide the second part. When you want the distance as a parameter a rigid joint is what you need.

[JYZMT]

Hello,

I just tried this. does any one know if its still working? the dialogue box does not appear. When I look at the mp4 movie (in the first attachment post), the script is run, then the dialogue is pulled across from the right? (17 seconds in to the mp4). I assume this is coming in from another screen? is it possible the dialogue is working, but just off my screen somewhere?

Second question... is there any update on the native pattern feature? Any better way to pattern a component with a translation and rotation? 

If this does not work, my next thought was to do a vertical pattern, then make a rotation joint to each component, driven by multiple of a rotation parameter? but it means re applying every time a component is added or subtracted. 

Any other ideas???

Thanks

[jhorstink]

Hello,

Yes, it is still functioning. The dialogbox pops up when you start to edit the joint.

You can then change it from 'revolute' to 'rigid' etc.

Regards,

[JYZMT]

I appear to have posted this in entirely the wrong thread!!!! So it makes little sense. Sorry about this. I had loads of similar posts up and replied in the wrong one I guess. 

This is the tread I wanted. https://forums.autodesk.com/t5/fusion-360-design-validate/patterning-by-translation-and-rotation/td-...

I'll post there instead. 

Sorry again.