In the oring part, create a datum plane and mate to it.

Jonathan T. Schmidt
http://www.schmidtmotorworks.com

Hi Metfuel,

It just so happens that I have been doing the exact same thing recently.

You will need to have a datum plane running perpendicular through the o-ring.  I use this to create an offset from the bottom of the o-ring groove, or other appropriate reference as required, to the datum plane at half the o-ring thickness.

Also you should have an axis to allow you to align you o-ring to the o-ring groove, assuming it to be circular.

If for some unusual situation you have an o-ring which is to fit into a irregular or non-circular groove, three datums would you best option possibly.

I hope this is of help

Best Regards

Dave

Even better is create a datum plane as already suggested but use the "centre" mating condition using a 1 to 2 approach.
You then don't need to have a positional expression for 1/2 the o-ring groove.
Guess this would depend on the appliction a bit though.

Hope that's useful.

Mark Benson
CAD Support Engineer

How about using interpart expressions?