Very Small Errors Appearing in Assemblies

[TechWise]

I'm a relative newcomer to Fusion 360 having previously used Inventor. I am having an issue with very small distance and angle errors appearing in assemblies. The result of this is that when I try to measure a distance from one end of the assembly to the other, it actually reads a very small angle between the two faces instead of a distance.

Here is a very simple example. The middle piece is extruded to 810mm, yet when placed in the assembly, it measures 810mm plus a very small amount. 

Here is precisely the same piece placed elsewhere in the assembly, yet the measured distance is different again.

Finally, when I try to measure from the very front of the assembly to the very back, it tells me a very small angle instead of a distance:

 I've never faced this issue in Inventor before. Any ideas what's going wrong?

[jhackney1972]

Please attach this or another assembly that illustrates your issue so the forum users can take it apart and try to see where the issue is coming from.  If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save to your hard drive. Then use the Attachments section of a forum post to attach it.

[TechWise]

I have been able to generate a test case with only the 3 components and two joints. The model is exporting now.

[jhackney1972]

You may have exported it but have you attached it to a post reply, I do not see it?

[TechWise]

Sorry, I was waiting for the export to complete and sent the screengrab in the meantime. Test case should now be attached. The cross piece is extruded to 810mm but measures a different distance once placed in the assembly. I've been able to replicate the issue when reloading the exported file into Fusion at my end, so hopefully it's replicated for you too.

[jhackney1972]

I do not share your issue.  Take a look at the Screencast, I measure it in three different ways, all 810mm long.  If you can record a Screencast showing how you are getting the error, I would love to see it.

[jhackney1972]

You also need to change your decimal precision, in your preferences, to something realistic.  Find me anyone who can measure millimeters to the precision you are using and I will eat my hat!  Even if I set mine to that precision, it still measures 810mm.

[TechWise]

Thanks for looking at this. I had closed Fusion and opened it again there when you replied and the issue seems to be gone now. Were it not for the screengrabs I captured I would not have believed that would happen so I'm at a bit of a loss to explain it. If I can recreate the issue, I will do a screen capture.

On a good day, I'm lucky to achieve +/- 1mm in the workshop! I only cranked the resolution right up as part of my own faultfinding efforts to figure out where the error might be getting introduced in the larger assembly.  I only realised there was an issue when I tried to measure all the way from front to back in the larger assembly and the inspect tool reported a very small angle rather than a distance.

[TheCADWhisperer]

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

Oops, I see you did attach file.

Are all of your sketches fully defined?

Do you have any unresolved issues highlighted in yellow (or red) in your Timeline?

[TechWise]

Yes, all sketches are fully defined. In any event, it's an extrusion of a profile so the faces at either end should be perpedicular, since I haven't "extruded to" another face, resulting in a possible angle. I've simply extruded the profile a fixed distance.

I have been unable to recreate the issue since rebooting Fusion. The screenshots in the previous post with small errors were generated, then I closed Fusion and waited for replies to come in. When I launched Fusion after John's response and opened the project again, the errors were gone. I think I'll just have to file this one under "unexplained".