The content of this article contains information regarding forging presses and their use.
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A forging press functions by deploying a vertical ram that exerts gradual and controlled pressure on a die that holds a workpiece. This process resembles drop forging but utilizes a constant pressure instead of repeated strikes. The steady motion provided by the ram allows deeper penetration into the workpiece, leading to consistent plastic deformation across the material.
There are two primary types of forging press dies: open and closed. In open die forging, the die partially encloses the workpiece, allowing some movement, while in closed die forging—also known as impression die forging—the die completely encloses the workpiece.
Forging presses apply pressure using either hydraulic or mechanical forces. Mechanical forging presses employ a flywheel to store energy that is transferred through a crank system to move the ram. These presses can exert pressures reaching up to 12,000 tons.
On the other hand, hydraulic forging presses create force through high-pressure fluid. Capable of delivering up to 75,000 tons of force, these presses are ideal for more challenging and demanding tasks.
The variety of forging presses is defined by their size and the amount of force they deliver to achieve the plastic deformation necessary in the workpiece.
The core aspect of modern forging operations is the capability to generate and concentrate substantial force on a workpiece. High-performance forging presses—critical equipment in metal forming and fabrication—deliver the intense power needed to deform and plasticize metals to achieve the most precise tolerances, shapes, and surface finishes. These industrial machines operate using either open or closed dies, catering to a wide range of applications in automotive, aerospace, oil and gas, and heavy machinery industries. Numerous methods exist to produce the required force in forging presses, and these machines are distinguished by their force-generation mechanisms—mechanical, hydraulic, screw, servo, pneumatic, and upsetters.
Forging presses can also be categorized based on their frame design, which can be either straight-sided or C-frame. Straight-sided forging presses feature two parallel sides, offering maximum rigidity for high-tonnage forgings and large batch operations. In contrast, C-frame presses have one side open for easier access, accommodating smaller-scale operations, maintenance, and die changes.
The most basic type of forging press is a mechanical press that has a ram moving vertically to apply pressure and squeeze a workpiece into the desired shape using dies. Modern forging presses represent a significant technological advancement beyond the old hammer-and-anvil methods of ancient times, which deformed materials using a series of blows. Today, high-speed, automated, and programmable presses provide the consistency, repeatability, and product quality demanded by precision parts manufacturing. Other types of forging presses include hydraulic, screw, servo, pneumatic, and upsetters, each producing similar shapes and capable of forging robust metals and alloys—even those with moderate ductility that would shatter under rapid impact or drop forging.
Hydraulic forging presses generate force by using hydraulic power—fluid mechanics based on Pascal's Law—to achieve immense pressure required for metal deformation. By applying a small initial force to a hydraulic fluid, a larger area of fluid displacement creates the significant force needed to operate the ram, shaping the metal workpiece under low to high tonnage capacities depending on design. These presses typically operate more slowly compared to mechanical presses, providing extended contact times with the workpiece, which is ideal for forging high-strength alloys and precision components.
Hydraulic forging commonly uses open dies, allowing for the free deformation of workpieces. This process is particularly suitable for isothermal forging and for producing large, complex shapes due to its slow, controlled compression rate. Advanced hydraulic forging presses can handle up to 50,000 tons of force, with die beds measuring up to 12 feet by 32 feet—enabling the production of crankshafts, engine blocks, turbine discs, and shipbuilding components.
Hydraulic forging dies endure significant wear because of prolonged contact with heated workpieces. This wear reduces die lifespan, which is a key consideration for press maintenance and production planning. The contact duration varies depending on workpiece material, temperature, and the degree of metal deformation required. Hydraulic presses excel in forging processes requiring deep, controlled deformation and are favored for forming large billets, seamless rings, and custom shafts.
Mechanical forging presses operate via a powerful motor and a controller equipped with a clutch and crankshaft assembly, delivering a fixed stroke profile for every press cycle. The ram accelerates to maximum speed mid-stroke, generating peak forging force at the stroke's bottom—a process ideal for high-volume, precision forging of small to medium-sized metal parts. Automatic knockout or liftout pins are integrated to quickly eject the forged piece from the die, enhancing cycle time and production efficiency.
The mechanical forging process places significant mechanical stress on dies yet applies minimal impact load compared to drop hammers. To prevent rapid wear or breakage, these presses use hardened tool steel dies, increasing die longevity and process reliability. However, the associated costs for custom tooling and die fabrication can be high, and changing dies on mechanical presses is often labor-intensive and time-consuming.
With advancements in automation and digital controls, modern mechanical forging presses achieve production rates of up to 70 strokes per minute. This enhancement in speed significantly reduces labor costs and increases throughput, making them highly suitable for mass production runs such as automotive components, hand tools, and hardware. Their high repeatability and fast operation support critical just-in-time manufacturing strategies.
The screw forging process, also known as screw press forging, employs a large flywheel and screw mechanism powered by either friction, electric, or hydraulic drive systems. Like hydraulic presses, screw presses operate at a slower pace, allowing for controlled deformation of the workpiece. The motor drives the screw, delivering a continuous, controlled pressure as it pushes the ram downward in a long stroke. Screw presses are highly suited for forging non-ferrous alloys, tool steels, and heavy-duty industrial components, with force capabilities reaching up to 31,000 tons.
A servo forging press is an advanced forging machine that utilizes a servo motor to drive an eccentric gear, precisely controlling slider movement. This innovative process converts the motor's driving force into linear reciprocating motion via screws, cranks, and elbow rods, enabling meticulous control over the slider's position, speed, stroke, and forging pressure. Sophisticated electronic controls and programmable logic controllers (PLC) make servo forging presses ideal for precision metal forming, high-mix low-volume manufacturing, and industries demanding flexible, energy-efficient, and highly-accurate production.
The transmission mechanism of a servo motor forging press transfers energy from the servo motor to the actuator, which drives the slider in a reciprocating motion to complete the forging process. While servo-motor forging presses generally have limited torque, restricting them to low-tonnage forging applications, they excel at complex, small batch, and custom metal part production.
Overall, servo presses are designed for energy efficiency and reduced maintenance, making them environmentally conscious solutions for modern manufacturing. These presses are also known for their quick setup, repeatable performance, and intelligent diagnostics—supporting Industry 4.0 initiatives in smart factories.
Pneumatic presses utilize compressed air or gas as their power source, which is directed into a cylinder attached to the ram. As the cylinder fills, air pressure causes the ram to move downward, delivering a smooth, controllable stroke for forging. Once the forming process is complete, the air or gas is vented, allowing the ram to return to its initial position. Pneumatic forging presses are well-suited for light to medium-duty work, including precision forging, deep drawing, assembly, punching, and blanking—offering fast actuation and lower maintenance costs. They are commonly used for shaping non-ferrous metals, aluminum, and light gauge steels, as well as applications requiring fast cycle times without the need for extremely high force.
Upset forging, also known as heading, is a metal forming technique utilizing a specialized horizontal forging press called an upsetter. The upsetter delivers axial force with a horizontally-moving ram, pressing the heated workpiece between two die halves. The heading tool—a punch or heading die—applies pressure along the longitudinal axis, displacing and reshaping the end of the workpiece. Two gripper and cavity dies—with one fixed and one movable—firmly secure the material, while a puncher mounted on the header slide drives the forging action.
This process begins with the movable die sliding toward the stationary die, ensuring the workpiece is held securely. The punch or ram then advances, forcing the workpiece to conform to the die cavities. Upon completion of each cycle, the punch or ram retracts and the movable die releases the newly forged part. Multiple cycles can be repeated as needed for complex shapes or multi-stage forging processes.
Preheating the workpiece before upset forging is a best practice, as it promotes optimal grain flow, reduces forging forces, and maintains metal integrity. The result is a forged component with superior mechanical properties such as increased tensile strength, fatigue resistance, and enhanced durability—qualities highly sought after in critical components.
Upset forging is frequently employed as an intermediate stage in closed-die or progressive forging sequences. Its primary applications include the production of fasteners (bolts, screws, nuts, and rivets), flanged shafts, axles, pipeline fittings, and specialty automotive, aerospace, and construction parts.
The forging press process is generally faster and more cost-effective compared to other methods. It results in a grain flow that enhances the strength of the final product. The diagram below illustrates the differences in grain flow among various methods: casting, machining, and forging. Casting typically exhibits no distinct grain flow, machining maintains a straight grain flow, while forging produces a grain flow that conforms to the shape of the piece.
The texture of the forged piece is continuous, which contributes to enhanced strength in the final product.
Throughout the forging process, the grain structure of the material is compressed, which reduces stress on corners and fillets, thereby increasing the overall strength of the piece.
Forging helps minimize metallurgical defects like porosity and alloy segregation, leading to less time required for machining the finished piece and better results during heat treatment.
Since forging eliminates voids and porosity, the pieces can be machined post-forging without compromising dimensional accuracy or quality. Tolerances are typically within 0.01 to 0.02 inches (0.25 to 0.5 mm).
Forging offers cost savings through efficient raw material usage, decreased machining time, and the ability to reclaim die material.
The longevity of a die depends on factors such as the materials being processed, the strength of the material, the precision of the required tolerances, and the complexity of the design.
Forging presses come in a broad range of tonnages, from a few hundred to several thousand tons, and can achieve working speeds of up to 40 or 50 parts per minute. The process typically completes parts in a single squeeze, although complex and intricate designs may slow down production. Forging presses are suitable for mass-producing a variety of components, including nuts, bolts, rivets, screws, brake levers, bearing races, valves, and many other parts.
In press forging, dies typically feature minimal draft, enabling the production of intricate and detailed shapes with high dimensional accuracy. Forging techniques can achieve deep protrusions, extending up to six times the material's thickness. By design, draft angles can be minimized or entirely removed to enhance precision.
Various ferrous metals, such as stainless steel, can be used in forging processes. Additionally, non-ferrous metals are particularly well-suited for press forging due to their desirable properties in shaping.
In press forging, the speed, stroke length, and pressure of the die are automatically regulated to ensure precision and operational efficiency.
The press forging process offers similar capabilities as other manufacturing techniques and can utilize CNC programming for design input, including automated blank feeding and removal of forged components.
Plastic deformation penetrates deeply into the workpiece, ensuring uniform deformation throughout the metal.
Like all manufacturing processes, safety is a critical consideration. A benefit of press forging is that it generally does not require specialized training for operators, apart from ensuring safety protocols are followed.
Forged components exhibit enhanced toughness and strength due to their continuous grain structure. Press forging also improves the flexibility of the final products, making them more ductile. Additionally, forged parts are anisotropic, meaning their properties vary along different axes due to the grain alignment.
Each forged component maintains consistent structural characteristics from the initial to the final part. The controlled and monitored production process ensures uniform composition and structure, minimizing variations in machinability and eliminating transfer distortion.
Press forging can be applied to a wide variety of metals, although some are more suitable for the process than others. The metals commonly used include carbon steel, stainless steel, tool steel, aluminum, titanium, brass, and copper. High-temperature alloys containing cobalt, nickel, and molybdenum are also amenable to press forging. The selection of metal depends on the specific requirements of the final product, considering factors such as strength, durability, and weight.
Bar stock is selected based on its grain structure, mechanical properties, shape, dimensions, surface quality, and suitability for mass production.
Steel must be heated to approximately 2200°F (1200°C) to be suitable for press forging. This heating process enhances the steel's ductility and malleability, allowing it to be shaped effectively under pressure. The increased plasticity of the steel ensures that a billet can be formed permanently without the risk of cracking.
Aluminum is ideal for forging because it is lightweight, corrosion resistant, and durable. Forgings of aluminum are used in applications requiring performance and the ability to endure excessive stress. Aluminum has high thermal conductivity, design flexibility, and fracture toughness. It can be forged using open or closed dies and does not require preheating before being forged.
Titanium boasts superior weight-to-strength and strength-to-density ratios, along with exceptional corrosion resistance. To enhance its inherent toughness and strength, titanium is heat-treated before being subjected to press forging.
Stainless steel, known for its corrosion resistance and remarkable strength, is versatile for forging into various shapes. Among its many grades, 304(L) and 316(L) are particularly used in press forging. Due to its strength, stainless steel demands higher pressures during forging and is processed at temperatures ranging from 1706°F to 2300°F (930°C to 1260°C).
Once brass is trimmed to the desired lengths, it is heated to approximately 1500°F (815°C) and then forged using either a closed or open die. Brass can be molded into various shapes and sizes, ranging from just a few ounces to several tons. Forged brass offers enhanced strength and durability.
Before forging, copper bars are heated to prepare them for shaping. Once heated, the bars are molded into their final form. Forged copper is known for its outstanding electrical and thermal conductivity. Copper forgings are categorized into high conductivity types and non-electrical grades, which are used for engineering purposes.
Magnesium is known for its low density while offering strength and stiffness that surpasses both steel and aluminum. However, it is more expensive and challenging to forge. The magnesium alloys most suitable for forging include AZ31B, AZ61A, AZ80A, ZK60A, M1A, and HM21A. Pure magnesium poses a risk of ignition, which is why it is typically alloyed with other metals to mitigate this issue.
The press forging process has many qualities that have made it an excellent means for producing high volumes of parts at low cost. Regardless of its wide use, there are drawbacks, limitations, and disadvantages to the process.
Cost is a significant consideration in press forging. The machinery used for this process is large and must be robust to generate the necessary force. The tools and dies used must be custom-made from specific metals.
Press forging is not suitable for producing highly intricate parts and designs. While it can handle components with complex external shapes, it struggles with parts requiring internal cavities and detailed features.
Only parts that can be shaped by pressing two dies together can be manufactured. Delicate features, overhangs, and special additions are not feasible with this method.
Forging press dies are costly and challenging to produce, especially for complex parts. They are crafted from a specific steel type, which must be heat-treated, roughly machined, and finely finished.
Pressing a part in a forging press requires immense pressure, necessitating large and costly equipment.
If a metal needs to be heated before press forging, additional finishing steps are required after the process.
Press forging is limited to producing parts of specific sizes, which excludes large-scale designs.
The types of metals suitable for press forging are restricted. Cast iron, chromium, and tungsten cannot be forged using this method due to their brittleness.
Despite eliminating shrinkage and porosity, press forging can still result in defects such as laps, piping, and die failures in the final product.
Forging presses cannot achieve millimeter-level tolerances.
Metals that require heating before pressing can develop residual stress if not cooled properly after the process.
Scale pits occur when the surface to be forged is inadequately cleaned, particularly in open environment forgings.
Flakes are internal cracks that appear during the cooling phase after heating and pressing, weakening the final product.
Press forging applies pressure gradually, with the die remaining in contact with the workpiece for an extended period, which slows down production.
Forging presses play a crucial role in the manufacturing processes across various industries, including automotive, aerospace, agricultural machinery, oilfield components, tools and hardware, and military ordnance.
In automobiles, press forged components are used at locations subjected to shock and stress. A single car or truck may contain more than 200 press forged parts. Some examples are illustrated in the diagram below.
Both ferrous and nonferrous forgings are utilized in helicopters, piston-engine planes, commercial airliners, and supersonic military jets. Aircraft are engineered with press forged components and may include over 400 distinct forged parts. Examples are shown in the diagram below.
Forged components used in farm tractors and earthmovers include engine and transmission parts, gears, sprockets, levers, shafts, spindles, ball joints, wheel hubs, rollers, yokes, axle beams, bearing holders, and links.
There are more than five hundred forged components in tanks.
Forging press components are crucial in the construction of oil platforms because of their durability, absence of porosity, and capacity to endure high-pressure environments.
The Occupational Safety and Health Administration (OSHA) has established guidelines and standards that manufacturers must adhere to for the safe operation of forging presses.
OSHA's regulations for operating forging presses are detailed in standard 29 CFR Part 1910.
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