What's the rule for defining the base part with 0 DOF in Assembly?

[Drkwing]

In the previous CAD software I used, when creatring an assembly, the software automatically defines the first part added to assembly as the Base Part (or Ground Part). The term implies that base part has no degree of freedom, or in other words fixed in space. Thus by mating other parts to the base part you can decrease the DOFs of the newcomers.

During the assembly process I can easily change the base part if needed.

But unfortunately in UG NX2 I let alone changing the base part, cant even see which the base part is. I am also not sure that a base or grounded part concept is available in UG.

I will be glad if anyone can help me with the concept of assembly with respect to the base part.

Regards

 

[innes]

NX2 doesn't seem to have the concept of a base part, so you have to constrain it yourself. I find it useful to define some datums at the top level of the assembly and mate the base part to those datums in order to "lock it down".