How to mate 2 circular parts using 2 concentric and 1 planar mates?

paul_ragot

Hello,

How do you assemble 2 circular parts (ex: 2 discs) so they are concentric , and to clock 1 to the other, line up a hole on 1 with a cylindrical boss on the other? As per picture. A simple planar mate is used for the planar faces. 
Thanks,

mahir

Mates work a little differently in Onshape. Since mate connectors are like mini axis systems, you really only need 2 mates - 1 revolute and 1 cylindrical. The cylindrical mate is like the traditional concentric mate, only making the axes of two cylinders coincedent but allowing axial "sliding". The revolute mate is a combination of concentricity and coincidence/offset of planes. As long as you set up your mate connectors in locations that make sense, like the center of circular face of the hole, it should work as you intend. I'm guessing someone here will probably whip out a video explaining the whole process.

bradley_sauln

@paul_ragot welcome to the wonderful world of Onshape! We use higher-order mates between parts to help make relationships between parts more realistic. As @mahir mentioned, we have a lot of great training videos available to walk you through how this works. Here is a great starting point: https://www.onshape.com/videos/assembly-mates

paul_ragot

Hello,

This seemingly trivial case is not obvious.
I tried 2 cylindrical, changed 1 to revolute, nada. I get an overconstrained condition. I tried a lot of combinations with no luck.
It is theoretically hyperstatic, as the 2 cylinders (outer and boss) both eliminate the same d.o.f.

Part is public: 2 circular part assembly

Thanks,

mahir

@paul_ragot, your parts were modeled such that this mate scheme is impossible. The distance between the central axis and the eccentric axis was not the same for both parts. Once that was fixed, the mating worked fine. See my doc below.

https://cad.onshape.com/documents/57bdc4fcaf4c0c10708cae11/w/1ae104845d502c831b95d11d/e/cf776e8da1701dffaad3b8f0

paul_ragot

Hello Mahir,

Yes, 1 of those details that are so obvious but to the creator!
Thank you very much for taking the time to resolve this-works fine now.
Regards,

mahir

No problem