I am trying to add a fastened mate to a ring. however the mate always goes to the center

ChrisJ

I am modelling a gas stove trivet. It has an iron outer ring and four supports. The supports are evenly placed around the outer ring. They are welded into place so there is no feature on the ring to attach a mate to.

The problem is every time I try to add a mate to the ring it snaps to the center of the ring. The only way to move it to the outer edge of the ring is to add an offset.

This means if I vary the size of the ring the mate will no longer match and I'll have to come back in and adjust it. While this is of course entirely doable it seems I am missing something and no amount of searching has revealed a solution.

How do I get a fastened mate connector to attach to the outside of the ring (circle)?

https://cad.onshape.com/documents/a9026ef0140c952ae1f80889/w/7a858bc382ff676427d3f366/e/1e32347422fe949cc96414f0?renderMode=0&uiState=665ed8b85afcbb7813e0070b

_anton

As always, there's a number of approaches, but here's one: https://cad.onshape.com/documents/29623ad9a9f974579cb6a278/w/661cb404012748e4088488fc/e/bbcf3ac79be8205f1bbd9143

(Explanation: I made the ring a revolved body, and put a mate connector on the sketch, owned by the body. Now the assembly will have a mate connector to use.)

_anton

I think the Variable Studio approach is the best, just slightly more advanced. Not only because it solves this issue, but because it lets you drive the entire design from one place.

_anton

As always, there's a number of approaches, but here's one: https://cad.onshape.com/documents/29623ad9a9f974579cb6a278/w/661cb404012748e4088488fc/e/bbcf3ac79be8205f1bbd9143

(Explanation: I made the ring a revolved body, and put a mate connector on the sketch, owned by the body. Now the assembly will have a mate connector to use.)

ChrisJ

Thanks _anton. 

I assume this means there is no simple way to solve this problem inside the assembly. I did try to place a mate on the sketch and found I had the same difficulty. I did not think of creating a revolve to create a point to place a mate.

I had thought of adding a feature of some sort as an anchor point for a mate. A revolve is a cleaner method, but means I needed to consider this problem from the very beginning of my design.

Running into an unexpected issue like this and having to redraw the most basic part of your design could mean restarting from scratch as a major change like that can break many downstream parts.

Another solution I came up with was to create a variable studio and then setting the mate offset to the ring diameter and ring height variables and use the same in my sketch.

I was surprised this problem is not more documented as I could find no onshape forum topics or other forums discussing this issue.

NOTE: original post vanished so this is a repost of that.

_anton

I think the Variable Studio approach is the best, just slightly more advanced. Not only because it solves this issue, but because it lets you drive the entire design from one place.

eric_pesty

ChrisJ said:

Thanks _anton. 

I assume this means there is no simple way to solve this problem inside the assembly. I did try to place a mate on the sketch and found I had the same difficulty. I did not think of creating a revolve to create a point to place a mate.

I had thought of adding a feature of some sort as an anchor point for a mate. A revolve is a cleaner method, but means I needed to consider this problem from the very beginning of my design.

Running into an unexpected issue like this and having to redraw the most basic part of your design could mean restarting from scratch as a major change like that can break many downstream parts.

Another solution I came up with was to create a variable studio and then setting the mate offset to the ring diameter and ring height variables and use the same in my sketch.

I was surprised this problem is not more documented as I could find no onshape forum topics or other forums discussing this issue.

NOTE: original post vanished so this is a repost of that.

You don't need to start from scratch, you can always add a separate sketch afterwards to define a mate connector location on the ring...

A simpler and better approach for something like this is to just draw both parts in the same part studio, with the support drawn in its correct location directly, you can then just use a group mate in the assembly.
Another benefit is you would then be able to set the gap between the supports in your design directly independently of the ring size.

Edit: like this: https://cad.onshape.com/documents/bb87cd19f683250c0c05e3b5/w/84e8c07110a7c80e838ac81e/e/806de1ad4e5baad34e289051?renderMode=0&tangentEdgeStyle=1&uiState=6660a30933840c470773debb

ChrisJ

_anton said:

I think the Variable Studio approach is the best, just slightly more advanced. Not only because it solves this issue, but because it lets you drive the entire design from one place.

This is the one I went with.