The Collaborative International Dictionary of English v.0.48:

drop forge \drop forge\ n.
   a device for making large forgings, in which a heavy hammer
   drops onto the metalwork to be forged, pressing it into a
   form or anvil underneath, or between dies.

   Syn: drop hammer, drop press. [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

drop forge
    n 1: device for making large forgings [syn: drop forge, drop
         hammer, drop press]