A quick Google search that a "Palletizing Robot" has been around for some time. The below ebay offering is interesting.
http://www.ebay.com/itm/Axis-palletizing-robot-manipulator-model-with-no-arduino-servo-control-board-/271275924586?_trksid=p2054897.l4275
https://www.google.com/search?as_q=Palletizing+Robot+&as_epq=&as_oq=&as_eq=&as_nlo=&as_nhi=&lr=&cr=&as_qdr=all&as_sitesearch=&as_occt=any&safe=images&tbs=&as_filetype=&as_rights=