A power hammer, also known as a forged power hammer, is a mechanical device that uses various means like steam, hydraulics, spring, etc., to create pressure. Modern versions of such hammers come with pneumatic or electric hammers. Simply put, we can say that a hammer works wherever an object is held when a force is applied in the opposite direction of its rapid movement. These mechanical devices use some form of pressure to generate force. The punch is fast and hits with great force compared to the power of a hydraulic press.
Given the size of hydraulic presses, power hammers are also quite large compared to other tools. The greater the effort, the greater the desired result. These are preferred for smoother and more consistent results as the full mass of the device gets the necessary vibration and movement from the weights. In this article, we have added some of the main types of power hammer and their working.
Types of Power Hammers
Following are the common types of forging power hammers used in the forging shop:
- Hydraulic Power Hammers
- Pneumatic Power Hammers
- Helve Power Hammers
- Lever-Spring Power Hammers
- Steam or Air Power Hammers
Hydraulic Power Hammer
Hydraulic power hammers or hydraulic presses use very high hydraulic pressures in their hydraulic cylinders. Hydraulic power hammers used 200 to 300 times atmospheric pressure for heavy forgings. This includes the press itself and the hydraulic drive. Since the whole process is completed in one press, the production speed is faster than hammer forging. Hydraulic presses automatically control die speed, impact pressure, and path. Unlike mechanical presses and hammers, it operates quietly and has little vibration. Since no pump can provide sufficient oil output at 200-300 times atmospheric pressure, it is common to use accumulators and boosters that increase the hydraulic pressure delivered by the pump to 40-50 times the force of 75,000 tons. Nevertheless, 1000-10,000 tonne hydraulic presses are often used in the forging industry. Hydraulic press ram speeds range from 30 to 90 strokes per minute. Hydraulic presses are used for the high-speed production of nuts, bolts, screws, and rivets.
Working of Hydraulic Power Hammer:
Hydraulic power hammers / hydraulic presses are hydraulically operated. This is the reason for their name, but it is also what sets them apart. Pascal’s Law, the mechanical principle of mechanics, is a fundamental function of hydraulic hammers. When you apply pressure to one part of the liquid, the pressure is transmitted to all areas of the liquid, amplifying the force. Hydraulic power hammers use incompressible hydraulic fluid, and the pressure is stored in a small canister. This hydraulic system provides power to the machine.
Pneumatic Power Hammers
The Pneumatic Power Hammer is a mechanical forging hammer that uses a non-muscular power source to lift the hammer prior to striking and accelerating the hammer into the workpiece being hammered. Commonly known as a “free type power forging hammer”. A typical pneumatic power hammer consists of a frame, anvil, and a reciprocating ram that holds the hammer’s head or die. Place the workpiece on the lower anvil or die and hit the workpiece with the head or upper die. A direct descendant of the trigger hammer, the power hammer differs in that the power hammer has a mechanical linkage and spring arrangement, storing potential energy in compressed air or steam to accelerate the ram on the downstroke. This will give you more strength as well as shedding weight.
Working of Pneumatic Power Hammers
The diagram shows a typical configuration of a pneumatic power hammer. Figure showing a cylinder (C) in which pistons reciprocate. The piston is connected to the main engine shaft via a crank and connecting rod mechanism. The air valve is operated by a hand lever. The air valve is in the air passage from cylinder (C) to cylinder (B). Another piston works in the cylinder (B). This piston has a tup at its base and can slide within a fixed guide.
Place the tup on the anvil. To initiate tup movement, move the cylinder (C) piston down and create a vacuum above the cylinder (B) piston. This creates a suction effect on the piston and the impact begins to lift. Air is forced out of the cylinder (C) to cylinder (B) just before the end of the upstroke of the piston in cylinder (B). In-cylinder (B) air is compressed by the upward stroke of the piston. This pushes the piston down and pushes the racket down at high speed. This process is repeated over and over to record the required shots.
Helve Power Hammer
A Helve power hammer, also known as a trip or tilt power hammer, is a giant power hammer. These are a type of blacksmith’s hammer, with multiple hammers set up in the smithy, also known as a hammermill. These forging hammers are typically lifted by a cam and suddenly released to drop under gravity. Shell hammers were primarily powered by water wheels. Used in gypsum forging to turn iron blocks into more workable bars. In addition, they are also used to make various items out of wrought iron, slats (a type of brass), steel, and other metals.
Working of Helve Power Hammer
The Working Principle of the Helve hammer is different for different types of Helve hammers or Tilt Power Hammer.
A tilt hammer, or tail helve hammer, has a pivot in the center of the shaft and is lifted by pushing down on the opposite end of the head. In practice, such hammerheads were apparently limited to 100 weights (approximately 50 kg) but were capable of very high impact velocities. This made it suitable for pulling the iron down to a smaller size for cutlery crafts. It was also used in brass battery work to make brass (or copper) pots and pans.
The belly handle hammer is of the type commonly found in fine shops and is used to work pig iron into malleable bar iron. This was caused by the cam hitting the stem between the pivot and the head. The head usually weighed a quarter of a ton. This was probably due to the wooden handle being overstressed with the heavy head.
The Nose Helve hammers appear to have been rare until the late 18th or early 19th century.
Lever-Spring Power Hammer
Ultra-lightweight power hammer for small forging. It consists of a heavy frame with a vertical ledge on top. This lug is a housing for the bearing in which the leaf spring oscillates. One end of this spring has a connecting rod and the other end has a vertical tup. The tup supports weight and moves vertically up and down between fixed guides.
The connecting rod is attached at its lower end to the eccentric sheave. The eccentric sheave is also connected to the crank wheel which operates the hammer & presses the treadle downwards. As a result, the sheave rotates through the crank wheel & therefore the laminated spring starts oscillating in the bearing. The vibration of this spring moves the tup up and down. In this way, the required punch is provided at work. The connecting rod stroke and impact strength are adjusted with a hand lever.
Working of Lever-Spring Hammer
It belonged to the motor hammer category and was powered by a belt-driven electric motor. The Ram Hammer uses an integral spring to strike a heated workpiece vertically, shaping it under pressure.
Steam or Air Power Hammer
Steam hammers can be run with either steam or compressed air. This includes moving rams, rods, and pistons, lifting tools, high-pressure double-acting steam cylinders, housings or frames, and anvils. In these types of forging hammers, steam first enters through the bottom of the cylinder, lifting the piston along with the other moving parts. The force-velocity is about 3 m/s, but the mass of moving parts is up to 5000 kg. When the required blow is needed, the lever is actuated to open the upper slide, allowing steam to enter the top of the cylinder, and leaving the exhaust steam at the bottom. So, you get the blow you want.
Working of Steam of Air hammer:
A single-acting steam hammer is lifted by the pressure of steam injected into the bottom of the cylinder and dropped by gravity when the pressure is released. In the more common double-acting steam hammer, steam is also used to push down the ram, giving the die a heavy blow.
Application of Power Hammer:
A power hammer is a tool mainly used in the forging process. In addition to forging, these tools are also used for fastening rivets and striking steel tools. The primary purpose and uses of power hammers are very similar to manual hammers. The design and use of a blacksmith’s hammer is like a manual hammer, but cuts and welds are more precise. To understand the purpose of a power hammer, understanding the forging process is a must. Click here to read about the forging process.
As you know, these power hammers allow you to completely transform your workpiece. This usually deforms only the surface of the workpiece that meets the hammer and anvil. The interior of the workpiece is relatively safe.
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