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.
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:
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.
Some of the most significant benefits associated with open die forging include:
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.
The benefits associated with closed die forging include:
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.
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.
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.
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.
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:
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.
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Start Your QuoteOpen die forging is the process of deforming a piece of metal between multiple dies that do not completely enclose the material. The metal is altered as the dies “hammer” or “stamp” the material through a series of movements until the desired shape is achieved. Products formed through open forging often need secondary machining and refining to achieve the tolerances required for the finished specifications. Open die forging is widely used for the products in small quantity that are simple, rather than complex, such as discs, rings, sleeves, cylinders and shafts. Custom shapes can also be produced with open die forging. The strength of the grain structure will be increased during the deformation process due to the repeated working of the steel billet. Another benefit of open die forging is that the fatigue resistance and strength of products will be improved. Besides, voids could be effectively reduced after open die forging.
Closed die forging (also known as as impression die forging) is a metal forming process that compress a piece of metal under high pressure to fill an enclosed die impression. For some special shapes, second forging operation is required to reach final shapes and dimensions. The type of material, tightness of tolerances, and need for heat treatment can determine the cost of a closed die forged part.
Definition
Open die forging is also called free forging. In open die forging, the billet is placed between multiple dies that do not enclose the metal entirely. The dimensions will be changed by hammering and stamping the metal through a series of movement until the final dimensions are achieved.
Closed die forging process, is also referred to as impression die forging. It utilizes high pressure to compress the metal piece to fill an enclosed die impression for required shapes. A medium frequency induction heating furnace is used to heat the metal for pressing into dies.
Process
The technique of both open die forging and closed die forging is different. In general, for closed die forging, the molding dies are first precision machined and cost is high. The metal bars are then placed on between upper and lower dies and forged to any shapes needed. After closed die forging very less or no machining will be operated due to its high accuracy throughout the process. So closed die forging is also a net shape or near net shape process.
For open die forging, enormous compressive forces are imposed by the continuous strike of a forging hammer to deform the metal billets. Unlike closed die forging, dies of open die forging is very simple. And secondly machining operation is always carried out.
Advantages & Disadvantages
Open Die Forging Closed Die Forging Advantages Better fatigue resistance and improved microstructure The internal grain structure formation increases the tightness and strength of the products. Continuous grain flow and finer grain size Economic for large production runs. Increased strength and longer part life No material limitation Less material waste Better surface finish Reduced chance of voids Less or no machining required for its close tolerances Valuable cost savings Dimensions of tighter tolerances and net shapes can be achieved Disadvantages It is not capable of forming close tolerance and higher precision parts It is not very economical for short runs due to the high cost of die production Machining is often required to achieve desired dimensions Closed die forging presents a dangerous working environmentApplication
Closed die forging and open die casting are the most common used forging methods for steel parts. Forging is popular because of its improved internal grain structure and can produce stronger and tougher products.
In Open die forging, a rough or precision machining is normally further required after the open die forging process as imprecise dimensions are achieved by hammering. Thus, open die forging is more suitable for large parts in a number of tons. Generally, the products in forging method include forged long shafts, forged rollers, and forged cylinders, which are mostly used for the application of railway and aircraft industry.
However, closed die forging is preferred for small critical parts with safety consideration because of its high precision. It is highly used to produce small products like forged fittings, forged lifting & rigging hardware, forged automotive parts, etc. Oilfield, automotive, forestry & agriculture, and mining are some of the industries that rely on closed die forging technique.