Open-Die Forging vs. Closed-Die Forging

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Differences Between Open-Die and Closed-Die Forging

Open-Die Forging

Open die forging is the art of shaping metal by hammering or pressing it between flat or simple contour dies, while manipulating the hot work-piece between each stroke of the equipment.  Since the metal tends to flow equally in all directions away from the high point of pressure, and is not physically confined by a cavity in a die, the process is termed to be “open die forging” as opposed to “closed” or “impression die” forging.

While open die forging generally applies to large, bulky forgings, the process can also be used for very small forgings as well. However, we do not recommended for a volume of forgings to be made with the open-die process. Instead, we specialize in closed-die forging.

Closed-Die Forging

In a closed-die (also called impression-die) process, the dies allow for excess material to be used and the material is forced to certain areas between the dies.  This excess material is called flash. The flash that is extruded between the dies can be costly and, therefore, needs to be minimized. However, flash has a vital use in that without this relief area, the pressure in the cavity could become too high. This could result in the reduction of die life or even the catastrophic failure of the die for forge machine component.  Our die design engineers control the flash area design in such a way as to aid and enhance the flow of the metal. This metal then fills the die impression to maximizing die strength and lifetime.

In production, the trimming of the flash from the forging is just as important as other forging operations. The trimming operation can be used to provide the final “sizing” of the finished forging.  Improper trimming can cause defect and/or distortion which cannot be repaired. So working with a reputable forging partner will help save money and reduce waste.

Advantages and Disadvantages

Pros of Open-Die Forging
– Less tooling cost
– Reduced lead time

Cons of Open-Die Forging
– Not suitable for precision parts
– Machining can often be required for desired features

Pros of Closed-Die Forging
– Stronger part
– Less machining required
– More cost effective for higher volume runs
– Able to achieve tighter tolerances and shapes

Cons of Closed-Die Forging
– Higher cost of die production
– Higher setup costs due to machine and furnaces

Looking to learn more about our forging services? Feel free to reach out and request a quote. We look forward to learning more about your project.