Open Die Forging VS Closed Die Forging

 In custom metal forging, manufacturing capability, metal manufacturing

The ancient process of forging is an indispensable part of modern metalworking. The basic idea is simple: you’re shaping metal by heating it and hammering it into a new form. Forging today is quite complex, with many different approaches and techniques. One of the most important distinctions is open die forging and closed die forging. Choosing between these techniques has a significant impact on your final product and can mean the difference between the success or failure of a project. This significance means considering the open die vs closed die forging question is crucial. In this guide, we will introduce the two approaches and consider how to decide between them.

What is open-die forging?

Let’s start with open die forging. This technique is the process of deforming and reshaping metal between dies that do not totally enclose the piece, resulting in free flow metal condition. The open die forging process stamps metal pieces between multiple dies until reaching the final shape. Though you’ve reached the desired shape, secondary machining is often required to ensure the metal pieces have the correct final dimensional characteristics. The open die process typically produces metal pieces like rings and shafts. However, the process can also make a variety of custom shapes. Open die forging increases the strength of metal, as the dies hammer impact distorts/refines the piece’s grain structure, making it internally more uniform. This feature creates final products with improved fatigue resistance and high strength. The level of increased strength and fatigue resistance is dependent on the level of deformation imparted to the original workpiece.

What is closed die forging?

The other side of the open die vs closed die forging question is closed die forging, also known as impression die forging. This technique uses high pressure to compress metal into dies that enclose the piece. Where the open die forging process uses flat dies, closed forging moulds metal into the shape of custom dies. First, the metalworker presses or hammers the material into the bottom die or die cavity. Secondly, the top die compresses the material into the desired shape. Unlike open die forging, this process typically results in a more precise final geometric shape. Any subsequent machining is very minimal, thus resulting in reduced waste of metal and, generally, a final product of a greater geometric complexity. Like the other technique, closed die forging strengthens the metal piece by refining its grain structure.

Open die vs closed die forging

These two forging techniques have distinct advantages and disadvantages. Though both processes increase the strength of the final shape, open die forging lends itself more readily to simpler and larger shapes. Also, open die forging can be used as a pre-forming operation in order to displace volumes of material, where required, then to be finished using closed die forging. The process’s simplicity means it is often cheaper to employ, especially when only needing a short production run. However, this simplicity means open die forging often cannot achieve high precision. Imprecision necessitates further work to create a wide range of complex shapes. Open die forging involves more human involvement than closed, which makes it a good choice for free-flow forging and custom pieces.b

Closed die forging is typically more expensive than open die forging. The moulding dies you need must be machined, which adds costs, and the process creates material waste, or ‘flash’. This disadvantage is much less noticeable when you’re producing large numbers of products, and the proportion of flash waste is minimal, compared to the mass of the final shape. The primary advantage of closed die forging is precision. The high pressure of impression die forging creates custom pieces with a clean surface finish, without sacrificing strength. These attributes make the closed die process ideal for producing smaller, complex shapes, and higher production run rates.


The two forging techniques do not directly compete. The decision in the open die vs closed die forging question depends on the producer’s needs. Open die forging is well suited to creating large metal parts such as long shafts and rollers. This feature means it is typically used in the railway and aircraft industries. By contrast, closed die forging is best used to create small, complex products. Many industries rely on closed die forging to create smaller parts and hardware, including the automotive, mining and agricultural sectors.

Deciding between open and closed die forging processes will come down to your particular needs. How many products are you aiming to use? Do you need a simple or a complex metal piece? How large are the parts going to be? Asking these questions as you consider your production needs will help you make the right decision. Ideally, you’ll have access to both processes. Outsourcing your work to forging specialists is a great way to achieve this.

Our offer

At Greg Sewell Forgings, we have your production needs covered. Closed-die forging is a core part of our manufacturing capabilities. Our expert team can produce a range of simple and complex metal products, whatever your needs. We use the latest machinery and industry innovations to ensure high-quality work. Our service extends to custom stainless steel fabrication and other advanced techniques. We’re always happy to discuss your forging needs and options, so don’t hesitate to reach out. At Greg Sewell Forgings, we’re confident we can help you throughout the manufacturing process and ensure your work succeeds.

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