One of the problems with robots is that there really is no good universal gripper. Each application requires special grippers and end of arm tooling.
Here is a simple solution that uses a latex balloon, ground coffee, and a little vacuum.
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In a similar vein, Iemca showed a magazine bar loader at IMTS that requires no channels (liner sets) in order to accomodate a wide range of bar diameters.
The bar loader uses magnetic rheological fluid in place of channels. Magnetic rhelogical fluid becomes more viscous in the presence of a magnetic field. Basically the bar loader creates its own channel via a magnetic field being applied to make the MRF nearly solid.