Revolute connectors, breaking

olivier_benoit

I cannot find a way to solve the connections of 4 parts linked with 4 revolute connectors.
This is supposed to be easy but I have tried for hours all options without success.

https://cad.onshape.com/documents/22eb8f99d7e3e06f78902120/w/0c35ca4e6d26c9e708ce6871/e/04c744e30db0c1a6878d0f51

Any help would be appreciated

michael_mcclain

You have a non-parallel face on "Part 1 <2>". You need to change "Revolute 1" to a "cylindrical mate" and instead of selecting the face for your mate connector, select the mate connector of the cylindrical face (inside of hole).

This will give you motion, but you still have an issue with that face being skewed very slightly (less than 0.5 degrees). Look in "Sketch 1" in "Lower Triangle" and constrain the line of the face with the "Horizontal" constraint. This will give you the parallel face you need to make the mate function properly in the future.

FYI I selected mating faces until I found the one that did not say "parallel distance." This showed me that one face was strange. I would also try to make sure that your sketches are more constrained and you start seeing more black lines in the sketcher. That sketch has many unconstrained entities.

michael_mcclain

Also, in general Planar faces are better to use for mate connectors, but in the case of the faces not being parallel then you have no choice but to choose a cylindrical face.

The reason Planar faces are stronger than cylindrical is because you can chamfer or fillet the edge of the hole and you wont lose the reference of the center of the hole in the face. If you had a cylindrical face selected and you add a fillet or chamfer, then the mate connector will move deeper into the hole because the edge of the cylinder has been moved by the fillet or chamfer.

michael_mcclain

You have a non-parallel face on "Part 1 <2>". You need to change "Revolute 1" to a "cylindrical mate" and instead of selecting the face for your mate connector, select the mate connector of the cylindrical face (inside of hole).

This will give you motion, but you still have an issue with that face being skewed very slightly (less than 0.5 degrees). Look in "Sketch 1" in "Lower Triangle" and constrain the line of the face with the "Horizontal" constraint. This will give you the parallel face you need to make the mate function properly in the future.

FYI I selected mating faces until I found the one that did not say "parallel distance." This showed me that one face was strange. I would also try to make sure that your sketches are more constrained and you start seeing more black lines in the sketcher. That sketch has many unconstrained entities.

michael_mcclain

Also, in general Planar faces are better to use for mate connectors, but in the case of the faces not being parallel then you have no choice but to choose a cylindrical face.

The reason Planar faces are stronger than cylindrical is because you can chamfer or fillet the edge of the hole and you wont lose the reference of the center of the hole in the face. If you had a cylindrical face selected and you add a fillet or chamfer, then the mate connector will move deeper into the hole because the edge of the cylinder has been moved by the fillet or chamfer.

olivier_benoit

Thanks a lot Michael, this is very very useful, I can get back to work on my design now!

michael_mcclain

Feel free to reach out to the community forum anytime. There are plenty of experienced users just chomping at the bit to solve any problem you may run into.