Two tangent mates

Dean_Gardner

Has anyone ever managed to have one part mate tangentially in two positions?  I have a plate with rollers moving along two tracks from one position to another and this should work, but Onshape thinks that i am over defining the assembly, which i am not.  If i remove one of the tangent propagation options on either mate, it works.  But of course that does not provide the movement i need.  Anyone have a workaround for this type of mate?

Dean_Gardner

Solved it! The pink part has tangent surfaces as well, so in fact it was overdefined!  When the pink part is just made from cylinders and does not have the attached tangent geometry, it works well.

eric_pesty

Good to see you sorted it out! You could probably just pick the circular edge at the end of the pink part (instead of the surface) to get around that issue.
If everything else fails, you can always use some intermediate "dummy" geometry like sketches/surfaces/curves. In this case a sketch with just line with the end "tangent" to a curve representing the centerline of the track and mated to the pink part would remove any risk of over-constraining anything.

Dean_Gardner

The dummy sketches is how i solved it in the end, they worked and it dawned on me!  Thanks.