Forging University: Open Die Forging vs. Closed Die Forging

Forging University: Open-Die Forging vs. Closed-Die Forging

Welcome back to Forging University! This is the fourth topic in our 5-part discussion. Today, we’ll compare two popular types of forging: open die vs. closed die. To get started, take a quick look back to Lesson #1, Lesson #2, and Lesson #3 to review forging basics. You can also check out Anderson Shumaker’s forging page for more information.

What is Open Die Forging?

Open die forging (also known as free forging) is the process of deforming metal between multiple dies. These dies do not enclose metal entirely. This is where we get the term “open die.” The dies hammer the metal through a series of movements. This alter the metal’s dimensions until the dies achieve the desired shape. Open die forging is Anderson Shumaker’s specialty.

What is Closed Die Forging?

Closed die forging (also called impression forging) uses pressure to force a metal piece into an enclosed die. This method uses a medium frequency induction heating furnace to heat the metal, thus achieving the desired shapes. As the dies press together, the forged material fills the impressions. The excess metal (called “flash”) is squeezed out.

What are the Advantages and Disadvantages of Both Forging Methods?

Die forging is the best method to meet tolerances. As a result of die forging, finished parts are completely filled. Die forging also creates the least amount of flashing. Most importantly, die forging helps save customers money in material costs.

Open die forging offers:

Excellent fatigue resistance and improved microstructure
Finer grain size and continuous grain flow
Increased strength (longer product life)
Reduced chance of voids in finished product
Less material waste (cost savings)

Open die forging’s final step is typically machining. Machining achieves accuracy and a desired finish. To this end, Anderson Shumaker keeps machining and finishing in-house. We like saving our customers time and money.

On the other hand, closed die forging offers:

Better surface finish
No material limitation
Is an economic choice for large runs
Achieves tighter tolerances and net shapes

However, closed-die forging does have some drawbacks. It’s not economical for short runs (which is an Anderson Shumaker specialty), it requires costly set-up, and compared to open-die forging, this process can present a dangerous working environment if building provisions cannot cope with the powerful vibrations.