topic Re: Possible cylindrical joint bug in Fusion Support Forum

Possible cylindrical joint bug

trhodesL6HUL — Thu, 27 Apr 2017 20:47:44 GMT

I think I found a cylindrical joint bug (since I haven't found someone that can explain this behavior).

Figure 1) There are two cylindrical joints among the three 5-way connectors. One between the left and center connector, and one between the right and center connector.

After applying a third cylindrical joint between the left and right connector (circled in red), Fusion 360 can't seem to compute it. Below is what happens:

I hope this is just me doing something wrong. But after asking several people, I suspect that it might be a bug. Is anyone able to recreate this problem?

Re: Possible cylindrical joint bug

innovatenate — Fri, 28 Apr 2017 14:31:14 GMT

I can recreate the issue also. I suspect you are right about there being a bug here. I can get the last joint in there if I cheat a bit, but it produces a warning and isn't an effective work-around. I've created a report (Internally referenced as FUS-32367) for development to review this.

For now, you may be able to work around this by using capture position and a pattern in the timeline. Note that I used a slider joint in this example.

I hope that helps. Let me know if you have any questions.

Re: Possible cylindrical joint bug

trhodesL6HUL — Fri, 28 Apr 2017 16:06:29 GMT

Thank you, Nathan. Will I be notified when the bug is resolved? My project (and buying a Fusion 360 license depends on it). I will try your fix today.

Re: Possible cylindrical joint bug

innovatenate — Fri, 28 Apr 2017 16:36:50 GMT

At this point, I'm not 100% sure if it is a bug or a limitation. However, I (or someone from development) will circle back with you as soon as we know more. If that suggestion doesn't help, please let me know. There is usually more than one way to accomplish any given task. I'll be happy to help!

Thanks,

Re: Possible cylindrical joint bug

trhodesL6HUL — Fri, 28 Apr 2017 20:22:01 GMT

I don't understand what you did in your screencast. This is my first time using Fusion. I can't afford to lose anymore time on this project, so I'm going to switch back to Inventor 2015 for the time being until there's a fix.

Re: Possible cylindrical joint bug

innovatenate — Fri, 28 Apr 2017 21:11:27 GMT

Here is a better screencast that is a paced a bit more deliberate and is more comprehensive. I hope it helps, if anything for learning purposes.

Re: Possible cylindrical joint bug

trhodesL6HUL — Fri, 28 Apr 2017 21:55:07 GMT

Wow, Nathan! Fusion 360 is great. I've never seen that component pattern feature before. That saves so much time for assemblies. Thank you for breaking that down. I will continue using Fusion 360 with your workaround for the time being. Having that 3rd cylindrical joint would help me sleep better at night, but the work around should get me through as long as I always use the capture position feature to recalculate the pattern positions.

Re: Possible cylindrical joint bug

TheCADWhisperer — Sun, 30 Apr 2017 13:50:23 GMT

I think the angle that you used in Sketch1 is a rounded approximation.

I think if you use geometry to solve (or at least solve out to 8 decimal places) that it will work as expected.

Re: Possible cylindrical joint bug

TheCADWhisperer — Sun, 30 Apr 2017 15:09:10 GMT

Re: Possible cylindrical joint bug

trhodesL6HUL — Mon, 01 May 2017 18:15:07 GMT

@TheCADWhisperer Thank you for the demo.

How does adding more decimals to that angle affect mating three connectors together? No matter what the angle is, they're all at the same angle. Three should mate without a problem, since it's just making a triangle, no?

Re: Possible cylindrical joint bug

TheCADWhisperer — Mon, 01 May 2017 19:11:00 GMT

@trhodesL6HUL wrote:

..
Three should mate without a problem, since it's just making a triangle, no?

No. Are you mating axis or are you mating arc center points.

If you intend to add shafts between the connectors - the geometry must be correct.

With the correct geometry - it works as expected.

You can't violate the geometry.

If you use geometry - you don't even need angle dimension. (my revised model using different technique and a few changes for manufacturability)

Re: Possible cylindrical joint bug

trhodesL6HUL — Mon, 01 May 2017 19:17:59 GMT

Thank you for the file. Can you explain why three don't align mating axis? The angle between each cylinder was 60 deg. Geometrically, three connectors should make a triangle if they all have the same angle (31.7 deg). I understand adding the precision for the full structure, but not for the triangle.