Revolute Joint Constraints Affecting Multiple Components

rex_hanson

I am trying to model a duct network for a dust collection system. I've created models of a Wye joint and have placed it in the assembly in a couple of different locations using a revolute constraint. When I try to spin the connection at the second joint, it causes the connection at the first instance of the component to also spin.

How can I prevent this from happening?

NeilCooke

@rex_hanson it's not that the revolute joint is affecting other joints, it's the fact that the other joints have free degrees of freedom. So when you drag one part, the constraint solver has no idea which DOFs you want to move and takes a best guess. In your case the best thing you should do is to use fastened mates throughout. Once fastened (the joint will likely rotate to default position), expand the mate in the instance list you can edit one of the mate connectors to change it's angle. Then your pipe will be in the correct position, fastened, and not affected by any other mates. Hope that makes sense.

Tony_C_

Another quick thought.

Taking this as an example, when I ran the pipe here in-between the fittings it was the LAST thing I did. And I use the in-context tool to do that.  None of my piping has mates on it, just the fittings.

Just remember never to move the pipe...only update its context. 

mthiesmeyer

Hi Rex,

Could you post a link to your doc here? It is hard to debug something like this without seeing how you have mated your parts.

Best,

Mike

rex_hanson

Here is the link:
https://cad.onshape.com/documents/5800daf91fc15da7b6a0a37d/w/b10fb2b6bc7a166ba9d6d17d/e/ecd06abc6ef94c0d9f142722

If you select the last component in the model tree (Wye 6-45 <20>, then drag the rotation handle that is sticking up in the air then you will see the other pipes moving around because it appears to be impacting the other instance of the Wye 6-45 constraint.

NeilCooke

@rex_hanson it's not that the revolute joint is affecting other joints, it's the fact that the other joints have free degrees of freedom. So when you drag one part, the constraint solver has no idea which DOFs you want to move and takes a best guess. In your case the best thing you should do is to use fastened mates throughout. Once fastened (the joint will likely rotate to default position), expand the mate in the instance list you can edit one of the mate connectors to change it's angle. Then your pipe will be in the correct position, fastened, and not affected by any other mates. Hope that makes sense.

rex_hanson

I wasn't aware I could specify an angle with the fasten connector. I thought my only choices were to play with it until it selected the right mate connector orientation, and then I could apply an offset. Can I specify a rotation angle for the revolute joint connector? Thank you!

Tony_C_

Best thing to do it put a mate on there and get it about where you want it then click on it and it will show you the degree it currently positioned.  Then you can edit the mate knowing about where you want it to be.  

Tony_C_

Also, I think a few of those could be fasten mates or sliders.

Tony_C_

Another quick thought.

Taking this as an example, when I ran the pipe here in-between the fittings it was the LAST thing I did. And I use the in-context tool to do that.  None of my piping has mates on it, just the fittings.

Just remember never to move the pipe...only update its context. 

rex_hanson

Thanks! I need to learn how to use the in-context capabilities.