Spring Compression Animation ...
 

What is the correct procedure for animating a spring compressing. I've tried the squash deformer but my geometry doesn't want to cooperate. The surfaces are separating, in spite of being grouped.

I don't think this is your direct problem but it may help, you could have a couple of different sized springs and use blendshapes to go between the stretched out one and the compressed one.

Chris

use a lattice deformer on the curve you're creating your spring with, (i'm assuming you extruded a circle along a CV or EP curve)not on the finished spring itself. that way the roundness of the spring won't also deform.