Open Die Forging

In open die forging, the hot workpiece is placed between two flat dies and is hammered to produce the desired shape. There is no flow of metal in this process. This is a slow process and may be performed by presses in addition to hammer (Figure 21.5a). It is repeatedly manipulated between the dies until the final shape is achieved. Cogging is successive deformation of a bar along its length using an open die drop forge. It is commonly used to work a piece of raw material to the proper thickness. Once the proper thickness is achieved the proper width is achieved via edging. Edging is the process of concentrating material using a concave shaped open die. The process is called edging because it is usually carried out on the ends of the workpiece. Fullering is a similar process that thins out sections of the forging using a convex shaped die. These processes prepare the workpieces for further forging processes.

Figure 21.5 Open and Closed Die Forging

Limitations of Open Die Forging

• It is limited to short run production.
• It has less control on mechanical properties and dimensions.

• It is restricted to simple shapes only.
• Machining is often required after forging.
• It has poor material utilizations.