The Case for Open Die vs. Closed Die Forging

Anderson Shumaker is proud to be an open die forge shop. However, this isn’t the only forging technique available. Sometimes our clients wonder which method gives the best advantage: open die or closed die forging? Let’s take a look at each.

Open Die Forging

Open die forging, also known as free forging, is when a heated piece of metal is deformed between multiple dies that do not entirely enclose the metal. The metal is stamped by dies hammer. These dies alter the metal’s dimensions until it reached its final shape.

It all starts with an ingot, or heated metal piece. This metal is heated until it becomes ductile. The ductile material is then hammered on a press until it conforms to its desired shape. A skilled forge master turns the metal between hammer blows to ensure correct grain flow. Open die forging often requires cycles of heating and pressing to achieve a finished piece. This method is an ideal for forging: blocks, cylinders, discs, flats, plates, rounds, shafts, and many custom shapes that require attention to detail and skill.

Open die forging does not require custom dies. Therefore, it is often cost-effective and faster. However, one disadvantage is that open die forged pieces often require machining. Because open die forging is not as precise, secondary machining is needed to finish the piece. Thankfully, skilled open die forge shops like Anderson Shumaker specialize in near-net shaped forging. This means are open die forgings often require minimal machining to be finished. We offer all machining in-house to save our clients time and cost.

Closed Die Forging

Closed die forging, also known as impression forging, uses pressure to force a metal piece to fill an enclosed die impression to form a predetermined shape. As the dies press together, the material fills the impressions, and the excess metal (flash) is squeezed out.

This process starts with metal that is heated until it is malleable but not yet liquid. This metal is compressed into two dies that form a mold. The extra metal that forms along the die’s edges is cut away, leaving the final shape.

Closed die forging is ideal for parts that need to be produced in large runs. One disadvantage to closed die forging is that sometimes the metal doesn’t fit all the creases of the mold, which can create an incomplete part. Unlike open die forging, forge masters cannot physically see the part as it is forged, so it is harder to make necessary corrections during the process. Another disadvantage is the closed dies themselves; to make the forging, the dies first need to be designed and created, which takes both time and cost. The cooling time of a close die forging can also create problems. The excess metal at the edges of the die cools faster than the metal on the inside, which can sometimes affect the finished product’s strength and integrity.

Which Forging Process is Right for My Project?

Every project is different, and critical issues like turnaround time, end-use, material grade, and run quantity needed all help determine which forging process is best for which product. Another important consideration is the skill and capabilities of your forging partner.

Anderson Shumaker has over 100 years of experience in open die forging, and many in-house value-added services at no cost to our clients. If you’re interesting in learning more about our processes, contact us today at [email protected] or request a quote to get your project rolling!