Cutting a model in animation

Hi everyone!

Okay, so I am new to blender. I am used to modeling in solidworks, but for this animation blender is more suited.

The animation should demonstrate sample preparation inside a focused ion beam microscope.
The first steps of which are creating a ridge (of platinum)


And then create cuts on each side.

So far, I have been creating this using shape Keys (not sure if that is the best way) and animating their value.

The next step in the process will be a cut under an angle, almost horizontally, that cuts the “wall” loose (see image below, the red shows the area that is removed)

How would you do this in blender? I have no idea how to cut a model in two in an animation.