Closed Die Forging

This is variation of impression die forging without flash (Figure 21.5b). It has better utilization of material than open flat dies, better physical properties, closer dimensional, tolerance, high production rate, etc. In impression die forging the heated workpiece is placed between two required shaped die and is pressed or hammered. During hammering or pressuring it takes the shape of the die. A small amount of material is forced outside the die impression, which is finally trimmed. The flash helps to build up pressure on the material between the dies which ensures the filling of dies cavity.

Advantages of Closed Die Forging

• There is saving of time because trimming is not required in this process.
• There is batter utilization of work materials.
• It has excellent reproductivity with good dimensional accuracy.
• Forging of complicated shape may be made.
• The products have good mechanical properties due to proper control of grain flow of the metal.
• It has high production rate.

Disadvantages of Closed Die Forging

• Tooling cost is high; therefore, it is suitable for large production run.