5.2.2.1 Conventional Impression Die Forging

A simple example of conventional impression die forging is illustrated in Figure 5-11. As the two dies approach, the workpiece undergoes plastic deformation, flowing laterally until it touches the side walls of the impression. A small amount of metal continues to flow outside of the impression, forming flash. As the dies continue to approach, the flash is thinned causing it to cool rapidly and offer increasing resistance to further deformation. The flash, in a sense, becomes part of the tool and helps to build up pressure inside of the cavity. The increased pressure promotes flow of metal into features of the impression previously unfilled.

Dimensional control of the forging in lateral directions is controlled by the walls of the die, and is ensured by complete die fill. Dimensional control in the axial direction is achieved by bringing the die faces to a predetermined position.

While flash can promote complete fill of the cavity, it does so at the cost of extremely high die pressures in the flash area. High pressures are undesirable because they reduce die life and require additional power. A flash gutter is often formed in the dies to receive the flash and allow the dies to reach the predetermined position at lower pressures. A typical flash gutter is shown in Figure 5-12.

Quality and production economy are optimized by using a sequence of forging operations, which are generally classified as "preforming" and "finishing". Most of the work of deformation is accomplished in the preforming operations at relatively low pressures. The finishing operation(s) bring the forging to its final contour and precision. The additional cost of the tooling and production operations is more than offset by higher productivity, increased die life and improved product quality. These factors increase in importance as production quantities increase. Forging in only a final die may be practical for very small runs if the shape is simple enough not to form defects.

Preforming operations may include one or more bending or rolling operations, and one or more preforming, or blocker die operations. Blocker dies are characterized by features such as large radii and generous draft angles, which minimize forging pressures. Usually only the final operation is designated as a finish operation. The types of operation and number of each are determined by the forging source, who is also responsible for design of the tools.

In some cases, the blocker die is the final step, and the forgings are known as "blocker forgings". In addition to the features enumerated above, blocker forgings include generous finishing allowances. They are suitable for moderate quantities of parts.

The complexity of impression die forgings drives the cost.

Forging Industry Association recognizes three impression die shape classes, with one to three shape groups in each, and four to six sub-groups for each shape group. Each shape is systematically identified with a three-digit number. The classification system is shown in Figure 5-13.


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A simple example of conventional impression die forging is illustrated in Figure 5-11. As the two dies approach, the workpiece undergoes plastic deformation, flowing laterally until it touches the side walls of the impression. A small amount of metal continues to flow outside of the impression, forming flash. As the dies continue to approach, the flash is thinned causing it to cool rapidly and offer increasing resistance to further deformation. The flash, in a sense, becomes part of the tool and helps to build up pressure inside of the cavity. The increased pressure promotes flow of metal into features of the impression previously unfilled.

Dimensional control of the forging in lateral directions is controlled by the walls of the die, and is ensured by complete die fill. Dimensional control in the axial direction is achieved by bringing the die faces to a predetermined position.

While flash can promote complete fill of the cavity, it does so at the cost of extremely high die pressures in the flash area. High pressures are undesirable because they reduce die life and require additional power. A flash gutter is often formed in the dies to receive the flash and allow the dies to reach the predetermined position at lower pressures. A typical flash gutter is shown in Figure 5-12.

Quality and production economy are optimized by using a sequence of forging operations, which are generally classified as "preforming" and "finishing". Most of the work of deformation is accomplished in the preforming operations at relatively low pressures. The finishing operation(s) bring the forging to its final contour and precision. The additional cost of the tooling and production operations is more than offset by higher productivity, increased die life and improved product quality. These factors increase in importance as production quantities increase. Forging in only a final die may be practical for very small runs if the shape is simple enough not to form defects.

Preforming operations may include one or more bending or rolling operations, and one or more preforming, or blocker die operations. Blocker dies are characterized by features such as large radii and generous draft angles, which minimize forging pressures. Usually only the final operation is designated as a finish operation. The types of operation and number of each are determined by the forging source, who is also responsible for design of the tools.

In some cases, the blocker die is the final step, and the forgings are known as "blocker forgings". In addition to the features enumerated above, blocker forgings include generous finishing allowances. They are suitable for moderate quantities of parts.

The complexity of impression die forgings drives the cost.

Forging Industry Association recognizes three impression die shape classes, with one to three shape groups in each, and four to six sub-groups for each shape group. Each shape is systematically identified with a three-digit number. The classification system is shown in Figure 5-13.


Return to Table of Contents

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A simple example of conventional impression die forging is illustrated in Figure 5-11. As the two dies approach, the workpiece undergoes plastic deformation, flowing laterally until it touches the side walls of the impression. A small amount of metal continues to flow outside of the impression, forming flash. As the dies continue to approach, the flash is thinned causing it to cool rapidly and offer increasing resistance to further deformation. The flash, in a sense, becomes part of the tool and helps to build up pressure inside of the cavity. The increased pressure promotes flow of metal into features of the impression previously unfilled.

Dimensional control of the forging in lateral directions is controlled by the walls of the die, and is ensured by complete die fill. Dimensional control in the axial direction is achieved by bringing the die faces to a predetermined position.

While flash can promote complete fill of the cavity, it does so at the cost of extremely high die pressures in the flash area. High pressures are undesirable because they reduce die life and require additional power. A flash gutter is often formed in the dies to receive the flash and allow the dies to reach the predetermined position at lower pressures. A typical flash gutter is shown in Figure 5-12.

Quality and production economy are optimized by using a sequence of forging operations, which are generally classified as "preforming" and "finishing". Most of the work of deformation is accomplished in the preforming operations at relatively low pressures. The finishing operation(s) bring the forging to its final contour and precision. The additional cost of the tooling and production operations is more than offset by higher productivity, increased die life and improved product quality. These factors increase in importance as production quantities increase. Forging in only a final die may be practical for very small runs if the shape is simple enough not to form defects.

Preforming operations may include one or more bending or rolling operations, and one or more preforming, or blocker die operations. Blocker dies are characterized by features such as large radii and generous draft angles, which minimize forging pressures. Usually only the final operation is designated as a finish operation. The types of operation and number of each are determined by the forging source, who is also responsible for design of the tools.

In some cases, the blocker die is the final step, and the forgings are known as "blocker forgings". In addition to the features enumerated above, blocker forgings include generous finishing allowances. They are suitable for moderate quantities of parts.

The complexity of impression die forgings drives the cost.

Forging Industry Association recognizes three impression die shape classes, with one to three shape groups in each, and four to six sub-groups for each shape group. Each shape is systematically identified with a three-digit number. The classification system is shown in Figure 5-13.


Return to Table of Contents

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