Often known as “impression die forging”, closed die forging involves two or more dies containing impressions brought together. This simple process displays great versatility. Manufacturers can create a nearly limitless array of shapes and complex metal parts in this way.
Closed die forging under controlled conditions permits the creation of forgings of all sizes within relatively tight tolerances. However, manufacturers usually employ this process to produce small, intricately shaped and patterned components in high volumes.
Custom die forgings play an important role in several important economic sectors, including the aerospace, automotive, manufacturing, electronic, semiconductor, construction and food processing industries.
The process of custom closed die forgings utilizes two or more metal dies. During this forging process, the manufacturer to some extent reproduces and automates the action of a blacksmith striking hot metal on an anvil to change the shape of a metal part.
With the assistance of a machine, a manufacturer programs the upper die to strike a heated metal billet placed on the lower die. This process may rely upon a variety of different forging methods.
Closed die forging machines rely upon two well lubricated tooling dies: a moving lower die (or “anvil die”) and a moving upper die (or “hammer die”). Each die consists of strong, durable material, such as high grade steel alloys. The die contains a partial negative impression of the shape of the final part.
The manufacturer places heated metal on the well lubricated bottom die. The heating process causes the metal surface to become malleable. (This step requires the use of a sufficient quantity of material to reproduce the final part.) The two dies then move towards each other, each shaping the metal during the compression process.
The molds will cover the entire metal in whole or in part. The dies together can rapidly generate copies of a particular part, reproducing the shape and conformation reliably within a reasonably high level of accuracy.
During the compression process, a small quantity of molten metal may flow along recesses on the edges of both dies called a “flash gutter”. This plug cools quickly. Efforts to eliminate flash completely resulted in the development of “true closed die forging” techniques using completely closed die cavities.
Manufacturers will often run heated metal on an assembly line through a series of automated closed die forging workstations in order to first shape the part and then impress additional details into the metal. The part may emerge from a final finisher cavity displaying fine details on the surface, for example.
Today, manufacturers often use sophisticated temperature controls to impact the creation of metal components. For instance, to produce custom die forgings displaying properties desired by a customer, a manufacturer may manipulate the temperature of the raw material:
To perform hot forging, a manufacturer heats metal into a molten state. The material will then undergo reshaping and forming in the casting and forging processes.
The manufacturer conducts forging on unheated metal at room temperatures, using intense high pressure to form a desired shape or impression in the raw material. This method of forging sometimes permits the reshaping of aluminum, for instance.
The manufacturer heats the metal prior to forging, but does not cause the raw material to lose its structural integrity. Metal will not recrystallize as a result of this type of forging, but it will assume a different shape.
Manufacturers sometimes distinguish the closed die forging process from another popular types of forging, open die forging. That process moves hot metal through workstations in which a die will only come into contact with a part of the workpiece at any given time.
The closed die forging process offers some distinct advantages over many forms of casting or open die forging from a manufacturing standpoint.
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