Pitch and roll are rotating around same axis on a ball joint.

[spaceman_2298]

Pitch and roll are rotating around same axis on the ball joint.

Steps to reproduce:
1. Create an 'As built' ball joint.

2. Preview motion of pitch and roll and find that they are same.

[jhackney1972]

In the video I have locked the Ball Joint in the Yaw axis.  I then lock the Pitch and the Roll at separate times.  You can see clearly that the motion is not on the same axis.  If you are arguing the motion goes through the same pivot point, that is correct but the motions are not on the same axis.  Model is attached if you want to try it yourself.

[jeff_strater]

see message #5 in this thread:  ball-joint-mysteries .

This one also has detailed information:  scratching-the-ball 

[spaceman_2298]

Thank you, John, for the reply. I find that the model you attached works as expected but the one I make has some trouble. I am attaching a demo model that has a problem. Am I missing something?

[jhackney1972]

I apologize for the late reply, I had to attend a get-together and I am just getting back to your post.  The reason you are getting two axis identical, in my opinion, is the Ball Joint was placed on the midpoint of the edge of the two components.  I replaced the joint with one on two points, basically the same position, just points not on the edge. 

When you are test any joint, using the Drive Joint command gives you a better picture.  Model I used in the video is attached.

[spaceman_2298]

Thank you, John, for the reply. Strangely, the model you have given also behaves oddly on my end. I tried creating a joint as suggested with no avail. Pitch and roll are oddly staying on same axis.

[jhackney1972]

I am at a loss, using my defined method I get three axis every time.  I hope someone else can give you more insight into your issue.

[davebYYPCU]

You are not alone, if there is a fix in Jeff’s references, I missed it.

[novalidtitle]

Anyone else have suggestions? I keep trying different things including what John suggested above and I can not get a 3 axis joint to work. Two of them are always the same. Really confusing as to why it works correctly for John but when we try that method we still get 2 on the same plane.

[matranc03]

Having the same problem on the lastest Fusion still. Roll is moving on the same axis as Pitch.

[TheCADWhisperer]

@matranc03 

Can you File>Export your *.f3d (or f3z) file to your local drive and then Attach it here to a Reply?

[matranc03]

@TheCADWhisperer as requested. I've tried settings custom axis in the joint limits menu as well because my main goal is to set limits such that the stem doesn't interfere with the cup to then animate what the maximum range of motion would be based on the assembly's global origin (as this reflects proper anatomical nomenclature easiest), but in the attached file they're the default ones. I also briefly read some forum posts about the behaviour likely being due to Fusion's use of euler angles instead of quaternions, but I did not see a solution within these discussions.