Joint error message in Fusion 360 got you down? No stress. Here’s an easy way to navigate them.

In this Fusion 360 Quick Tip, we demonstrate how to get past a common joint error message in Fusion 360. In the example in the video above, we have a four-bar linkage that’s almost complete. All that is left to do is to add the last Revolute joint.

Using the Joint command, we make sure that the motion type is set to Revolute, and then we can select the two edges that define the Revolute axis. However, when we do that, we get a warning saying the selected joint type would result in a conflict, and moving forward creates errors on all of the joints. Why isn’t this working?

Well, Fusion 360 is trying to connect two specific edges together, but they aren’t coplanar with each other. The Revolute joint requires that the two edges are coplanar. So, they must be off by a small amount.

Try the Cylindrical joint type

We need this joint to revolve and also slide so it can slide over into the correct location. To do this, start by using the Cylindrical joint type. This opens up two degrees of freedom — the revolute and the slider. If you select those same two edges, the part will now move into place without the error message.

The four joints are now created. However, the assembly looks… interesting. All you have to do is rotate these parts into location. Now we can see that the four bar linkage is working as expected.

Performing a Section Analysis

Let’s investigate why the Revolute joint didn’t work and why the Cylindrical joint did work. You can do this by creating a Section Analysis.

As we section into the design and we zoom up, we can see that there is a gap between two specific edges. Fusion 360 was trying to connect those edges together with the Revolute joint but couldn’t because of the Revolute joint above it that was already created.

Using the Measure command

We can confirm this is the case by using the Measure command. By selecting the two planar faces, we can see that they are off by 0.001.

So, this is why the joint was failing. We were able to get around it by using the Cylindrical joint type. However, the best thing to do here would be to fix the 3D model so the faces are coplanar with each other.

Ready to try this method out?