Open Die Forging Vs. Closed Die Forging

When it comes to metal forging, the two most common methods are open die forging and closed die forging. While each method offers unique advantages and manufacturing capabilities, choosing the proper method for your project depends on a range of factors, including the complexity of the forged parts, volume, and performance properties.

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At Great Lakes Forge, we specialize in open die metal forging. In this guide, we'll break down the differences between open die forging and closed die forging, including the processes, the outcomes, and the applications that tend to work best for each method.

What is the Difference Between Open Die and Closed Die Forgings?

Open die forging and closed die forging are fundamentally different in how they shape metal, the applications they serve, and the outcomes they achieve. Open and closed die forging processes are not interchangeable since they consist of different functionalities and physical parameters. Key differences between open die forging and closed die forging include:

• Open die forging shapes metal in open space, while closed die forging uses molds under high pressures
• Open die forging can create large parts; closed die forging is best for small parts
• Open die forging can produce parts with custom shapes; closed die forging is limited to the mold's dimensions
• Closed die forging achieves tighter tolerances than open die forging
• Open die forging is more cost-effective for low-volume jobs; closed die forging excels in high-volumes

The Open Die Forging Process

As its name suggests, the open die metal forging process is achieved within a relaxed environment free of encasing devices. The metal workpiece is heated at temperatures ranging from °F to °F and gradually shaped into the desired configuration. It is altered through skillful "hammering" or pressing movements until the desired shape is achieved. Open die forging is often used for forging large or custom-shaped parts, including shafts, cylinders, and blocks. It is also compatible with a wide range of superior-quality materials, including 13-8 stainless steel, carbon steel, and more.

Advantages of Open Die Forging

Some of the most significant benefits associated with open die forging include:

• Improved fatigue resistance
• Continuous grain flow
• Longer part life
• Increased strength
• Less chance of voids
• Finer grain size
• Custom shape design capabilities

The Closed Die Forging Process

Also referred to as impression die forging, closed die forging uses a closed, high-pressure environment to fill an enclosed die. The process involves placing heated metal between two dies, creating a precise impression as the material is pressed into shape. This method is ideal for producing complex parts with consistent dimensions and is commonly used for smaller, high-volume components. Closed die forging excels in applications requiring tight tolerances, precise repeatability, and mass volumes.

Advantages of Closed Die Forging

The benefits associated with closed die forging include:

• Dimensions with tighter tolerances and various shapes can be achieved
• More precise, consistent impressions
• Ability to reproduce nearly any shape or size
• Better surface finish
• Reduced need for additional machining
• Cost-effective for large production runs

Choosing Between Open Die and Closed Die Forging for Your Project Needs

Multiple factors should be considered before deciding which forging method is best for your project, including the part's complexity, the production volume, and the tolerance requirements.

Part Complexity

If the part is relatively simple, open die forging will likely be the more cost-effective method. However, if the part is complex, closed die forging may be necessary to achieve the desired shape and tolerances.

Volume of Production

Closed die forging is generally more efficient for high-volume production runs, while open die forging is usually better suited for lower volume or custom orders. Closed die forging requires more specialized equipment and tooling than open die forging, which can affect cost and lead times.

Tolerance Requirements

Closed die forging typically results in tighter tolerances and a smoother surface finish than open die forging. If your part doesn't require tight tolerances, open die forging is likely the more cost-effective forging method.

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Great Lakes Forge is Your Source for Superior-Quality Open Die Forgings

If you need custom open die forgings, Great Lakes Forge is your solution. We specialize in crafting durable, high-performance parts tailored to your exact specifications. Our team combines decades of expertise in open die forging with advanced technology to deliver superior results for even the most demanding applications.

In addition to our forging capabilities, we offer a range of secondary services to ensure your components meet the performance characteristics necessary for your application. Secondary services we offer include:

• Heat treating: Heat treating enhances the material properties of your open die forged parts, including strength, hardness, wear resistance, and more.
• CNC Machining & Milling: We use CNC machining and milling equipment to create components with exceptionally tight tolerances and custom dimensions.
• CNC Turning: Our CNC turning capabilities create precise cylindrical components, including shafts, spindles, and more.
• Fast, On-Time Deliveries: We go the extra mile to ensure you get your custom open die forged components with quick turnaround times.

Contact Great Lakes Forge for Expert Open Die Forging Services

Great Lakes Forge is your trusted provider of open die forging services for metal part manufacturing. Contact us for more information on our custom forging service options, or call us at 800-748-, and we'll help you find the best custom forging solutions for your project.

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