Drop forging is a process used to shape metal into complex shapes by dropping heated metal into a punch and die which compresses to gradually change the shape of the metal. The process of drop forming is very simple. The workpiece is placed into a die and punch, then the impact of a ram on the punch causes the heated material, which is very malleable, to conform to the shape of the punch and die cavities. Typically only one ram is needed to completely form the part. The extra space between the die and punch is called the flash. It acts as a relief valve for the extreme pressure produced by the closing of the die halves but is eventually trimmed off of the finished part.
The equipment used in the drop forming process is commonly known as a power drop hammer. These may be powered by air, hydraulics, or mechanics. Depending on how the machine is powered, the mass of the ram, and the drop height, the striking force can be anywhere from 11,000 to 425,000 pounds. The materials that are used most commonly in drop forging are aluminium, copper, nickel, mild steel, stainless steel, and magnesium. Mild steel is the best choice, and magnesium generally performs pretty poorly as a drop forging material.