Hammers have been continuously used for both open die and impression die forging, and are generally considered the most flexible in the variety of forging operations they can perform. They are characterized by a heavy ram, which contains the upper die. The ram is raised and allowed to fall or is driven onto the workpiece, which is placed on the bottom die. A large, heavy anvil supports the structure and holds the lower or stationary die. Hammers apply energy and cause deformation at very high rates. They are therefore suitable for alloys that can be deformed rapidly without forming cracks and splits in the workpiece. Aluminum 7xxx alloys and most magnesium alloys are not forged in hammers for this reason.
Hammers are classified according to the way in which the ram is raised and whether it falls freely or is driven.
Board Hammers Board hammers, or board drop hammers, which gave rise to the term "drop forging", operate by gravity only. The ram is raised mechanically to a predetermined height, which cannot be varied between blows, but can be reset between jobs. Cycle rates are high, as many as seventy per minute, and the energy imparted to the workpiece is the same on each blow. The workpiece is typically struck several times in impression die forging.
Board hammers are rated by their falling weight. They range in size from 100 to 7500 pounds, but nearly all are between 500 and 6500 pounds. The anvil serves as an inertia block and usually weighs 20 times as much as the hammer.
Air-lift hammers Air-lift hammers are similar to board hammers except that the ram is raised by action of air cylinders. On some hammers, the height can be varied on each stroke, either by the operator or by pre-programmed blow control. Air-lift hammers range in size from 500 to 10,000 pounds falling weight. Many air operated hammers are conversions from steam hammers and operate with power down as well as power up operation.
Steam or Air-Powered Hammers Steam or air-powered hammers are similar to air-lift hammers except that the hammer is raised either by steam or air, and is powered down onto the workpiece by pressurized steam or air, adding controlled energy and speed beyond gravity. Striking force can be varied on each stroke over the entire range from a light tap to full power. The complete control of each work stroke places higher requirements on operator skills than for other types of hammer. In a growing number of cases, they are being controlled by programmable systems.
Steam and air hammers are the largest and most powerful of conventional forging hammers, and typically range in weight from 1000 to 50,000 pounds. Double-frame hammers for open die forging have been built to 220,000 pounds, but 24,000 pounds is the usual maximum size. Anvils weigh 10 to 25 times as much as the hammer ram, and require massive underground installations.
Impacters A modification of air-driven hammers is the impacter, where two rams of equal weight are propelled horizontally toward each other and impact in a central location. Impacters can be automated to forge several hundred parts per hour, and generally are not designed for manual operation as are vertical air-powered hammers.
Other Types Other types of hammers, such as vertical counterblow, helve, trip and impacters are used less extensively. Largest hammers are often counterblow machines where both top and bottom die move simultaneously. Information on various hammers is available in Forging Industry Association literature.
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Hammers have been continuously used for both open die and impression die forging, and are generally considered the most flexible in the variety of forging operations they can perform. They are characterized by a heavy ram, which contains the upper die. The ram is raised and allowed to fall or is driven onto the workpiece, which is placed on the bottom die. A large, heavy anvil supports the structure and holds the lower or stationary die. Hammers apply energy and cause deformation at very high rates. They are therefore suitable for alloys that can be deformed rapidly without forming cracks and splits in the workpiece. Aluminum 7xxx alloys and most magnesium alloys are not forged in hammers for this reason.
Hammers are classified according to the way in which the ram is raised and whether it falls freely or is driven.
Board Hammers Board hammers, or board drop hammers, which gave rise to the term "drop forging", operate by gravity only. The ram is raised mechanically to a predetermined height, which cannot be varied between blows, but can be reset between jobs. Cycle rates are high, as many as seventy per minute, and the energy imparted to the workpiece is the same on each blow. The workpiece is typically struck several times in impression die forging.
Board hammers are rated by their falling weight. They range in size from 100 to 7500 pounds, but nearly all are between 500 and 6500 pounds. The anvil serves as an inertia block and usually weighs 20 times as much as the hammer.
Air-lift hammers Air-lift hammers are similar to board hammers except that the ram is raised by action of air cylinders. On some hammers, the height can be varied on each stroke, either by the operator or by pre-programmed blow control. Air-lift hammers range in size from 500 to 10,000 pounds falling weight. Many air operated hammers are conversions from steam hammers and operate with power down as well as power up operation.
Steam or Air-Powered Hammers Steam or air-powered hammers are similar to air-lift hammers except that the hammer is raised either by steam or air, and is powered down onto the workpiece by pressurized steam or air, adding controlled energy and speed beyond gravity. Striking force can be varied on each stroke over the entire range from a light tap to full power. The complete control of each work stroke places higher requirements on operator skills than for other types of hammer. In a growing number of cases, they are being controlled by programmable systems.
Steam and air hammers are the largest and most powerful of conventional forging hammers, and typically range in weight from 1000 to 50,000 pounds. Double-frame hammers for open die forging have been built to 220,000 pounds, but 24,000 pounds is the usual maximum size. Anvils weigh 10 to 25 times as much as the hammer ram, and require massive underground installations.
Impacters A modification of air-driven hammers is the impacter, where two rams of equal weight are propelled horizontally toward each other and impact in a central location. Impacters can be automated to forge several hundred parts per hour, and generally are not designed for manual operation as are vertical air-powered hammers.
Other Types Other types of hammers, such as vertical counterblow, helve, trip and impacters are used less extensively. Largest hammers are often counterblow machines where both top and bottom die move simultaneously. Information on various hammers is available in Forging Industry Association literature.
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Hammers have been continuously used for both open die and impression die forging, and are generally considered the most flexible in the variety of forging operations they can perform. They are characterized by a heavy ram, which contains the upper die. The ram is raised and allowed to fall or is driven onto the workpiece, which is placed on the bottom die. A large, heavy anvil supports the structure and holds the lower or stationary die. Hammers apply energy and cause deformation at very high rates. They are therefore suitable for alloys that can be deformed rapidly without forming cracks and splits in the workpiece. Aluminum 7xxx alloys and most magnesium alloys are not forged in hammers for this reason.
Hammers are classified according to the way in which the ram is raised and whether it falls freely or is driven.
Board Hammers Board hammers, or board drop hammers, which gave rise to the term "drop forging", operate by gravity only. The ram is raised mechanically to a predetermined height, which cannot be varied between blows, but can be reset between jobs. Cycle rates are high, as many as seventy per minute, and the energy imparted to the workpiece is the same on each blow. The workpiece is typically struck several times in impression die forging.
Board hammers are rated by their falling weight. They range in size from 100 to 7500 pounds, but nearly all are between 500 and 6500 pounds. The anvil serves as an inertia block and usually weighs 20 times as much as the hammer.
Air-lift hammers Air-lift hammers are similar to board hammers except that the ram is raised by action of air cylinders. On some hammers, the height can be varied on each stroke, either by the operator or by pre-programmed blow control. Air-lift hammers range in size from 500 to 10,000 pounds falling weight. Many air operated hammers are conversions from steam hammers and operate with power down as well as power up operation.
Steam or Air-Powered Hammers Steam or air-powered hammers are similar to air-lift hammers except that the hammer is raised either by steam or air, and is powered down onto the workpiece by pressurized steam or air, adding controlled energy and speed beyond gravity. Striking force can be varied on each stroke over the entire range from a light tap to full power. The complete control of each work stroke places higher requirements on operator skills than for other types of hammer. In a growing number of cases, they are being controlled by programmable systems.
Steam and air hammers are the largest and most powerful of conventional forging hammers, and typically range in weight from 1000 to 50,000 pounds. Double-frame hammers for open die forging have been built to 220,000 pounds, but 24,000 pounds is the usual maximum size. Anvils weigh 10 to 25 times as much as the hammer ram, and require massive underground installations.
Impacters A modification of air-driven hammers is the impacter, where two rams of equal weight are propelled horizontally toward each other and impact in a central location. Impacters can be automated to forge several hundred parts per hour, and generally are not designed for manual operation as are vertical air-powered hammers.
Other Types Other types of hammers, such as vertical counterblow, helve, trip and impacters are used less extensively. Largest hammers are often counterblow machines where both top and bottom die move simultaneously. Information on various hammers is available in Forging Industry Association literature.
Return to Table of Contents
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