You could use it to model a CNC machine, but you'd probably need to make new components. It would also be difficult to model the changing load as the spinning tool plunges into metal, but you could model dynamic deformation and response of the machine given the loads. It is difficult to model changing 3D contacts in modelica, although a new approach to solving newton's equations, dialectic mechanics may fix this problem

NEMA isn't a type of motor, it's a connection standard used for motors. You might be able to model stepper motors with some of the components in the modelica standard library for magnetic modeling.