Creating a reference frame - options

[prdave00]

I have a part that I've dumbed down (considerably) and attached 2 options as to how to establish a DRF for purposes of discussion. The drawings are also intentionally incomplete. The part consists of 3 feet with a domed tip that will sit on an irregular surface. There is a also a spherical socket that would interface with a shaft with a ball at the end. For the sake of discussion assume the part can be made out of a high-modulus plastic and will be secured to the irregular surface that I referred to.

The first pass will be to machine the part, but will eventually have the net shape molded (including the feet) with the socket secondarily machined in. With that in mind I am leaning towards option B since the feet will establish a machined-to-molded relationship (i.e., the socket will bot be present prior to machining). Theoretically, the 3X domed surfaces constrain all degrees of freedom, right?

Does either option make sense?

 

[ptruitt]

I would suggest having two drawings: A casting drawing and a machining drawing. The circularity of a sphere puzzles me. Only one datum is presented in the second option, but a second datum is referenced. I think folks are wondering how to get started with comments. I also know there will be those wondering how this is going to be measured without using maximum material boundaries on the Datum A in the second example, if hard gaging is to be used. I am wondering what plastic material can handle the wall sections shown.

Peter Truitt
Minnesota

 

[fsincox]

Understanding the function of the part is very important in determining these issues. Quite frankly it is hard to imagine what is actually going on here.
Frank