What are Power Hammers?
Power hammers are mechanical forging hammers that use an electrical power source or steam to raise the hammer preparatory to striking and accelerate it onto the work being hammered. Also called “Open Die Power Forging Hammers.” They have been used by blacksmiths, bladesmiths, metalworkers, and manufacturers since the late 1880s, having replaced trip hammers.
Design and operation
A typical power hammer consists of a frame, an anvil, and a reciprocating ram holding a hammerhead or die. The workpiece is placed on the lower anvil or die and the head or upper die strikes the workpiece.
The power hammer is a direct descendant of the trip hammer, differing in that the power hammer stores potential energy in an arrangement of mechanical linkages and springs, in compressed air, or steam, and by the fact that it accelerates the ram on the downward stroke.
This provides more force than simply allowing the weight to fall. Predecessors like trip hammers, steam drop hammers, board or strap hammers, used the power source to raise the ram or hammerhead, but let it fall solely under gravity.
Power hammers are rated by the weight of moving parts that act directly on the workpiece. This includes the weight of the parts that may consist of the upper die, ram, mechanical linkage arms and spring(s) or ram, piston, and associated connecting rod(s). Specific design elements are dictated by the power source. The largest power hammer was powered by steam and was rated at 125 short tons (113 t).
Types of Power Hammers
There are various different types of forging power hammers that are widely used in the market.
- Pneumatic Hammers
- Steam or Air Hammers
- Helve Hammers
- Hydraulic Power Hammer
- Lever-Spring Hammers
1. Pneumatic Power Hammer
Pneumatic power hammers are quite a typical form of mechanical device which is responsible for carrying the cylinder in which the piston works. This piston is found to be connected to the main motor shaft with the help of a crank and a connecting rod mechanism. A hand lever is also involved which operates the air valve.
The air valve is provided through the different cylinders. Another piston also works inside the cylinder which carries the tup at its bottom and is made to slide fixed guides. In order to make the tup move, the piston in the cylinder is moved downwards in order to create the vacuum above the piston inside the other cylinder. This is responsible for providing a suction effect on the piston due to which the tup starts lifting.
Near the end of an upward stroke of the piston, in-cylinder, the air is forced from one cylinder to another where the air is compressed due to the upward stroke of the piston. This is responsible for forcing the piston and thus moving the tup downwards with high velocity. This operation is repeated on a regular basis and the required blows are obtained.
2. Steam or Air Power Hammer
A steam-power hammer is referred to as those which can be performed by the effect of either steam or compressed air. These are the device which includes a moving ram, rod, piston, a lifting tool, a double-acting high-pressure steam cylinder, housing or frame, and anvil.
These are the forging power hammers wherein the steam gets entered initially and then at the bottom of the cylinder; the piston gets lifted upwards along with the other moving parts. The amount of force is considered as 3m/sec whereas the mass of the moving parts is nearly 5000kg.
Whenever the blow is required, the lever gets energized automatically where the top sliding value is opened in order to receive the steam from above of the cylinder and the exhaust steam which remains on the bottom. Thus, the required blows are obtained.
3. Helve Power Hammer
A helve power hammer is also referred to as a trip or tilt power hammer which is a huge powered hammer. These are the types of forging power hammers wherein more than one helve hammer is installed in a forge which is also referred to as a hammer mill.
These forging power hammers are normally lifted with a cam which is suddenly released to drop the force of gravity. The helve hammers are mechanical devices that are mostly hydraulically driven by a water wheel.
Also, these are used in order to make blooms, made of iron into more workable bar iron in the finery forges.
4. Hydraulic Power Hammer
The hydraulic hammers are also termed hydraulic presses which use 200 to 300 times higher oil pressure as compared to the atmospheric pressure in a hydraulic cylinder. The hydraulic presses are applied in heavy forgings which consist of a press and a hydraulic drive. The rate of production in hydraulic presses is observed to be faster as compared to the other hammer forgings through which the single squeezing action is completed.
The hydraulic hammer is found to have low noise and vibration as in these types of devices the speed, low pressure, and die travel, are controlled automatically. The presses which can provide a force of 75000 tons are quite common these days. The hydraulic presses are used in forging industries which widely range from 1000 tons to 10,000 tons. These presses are mostly used for the production of nuts, bolts, screws, and rivets.
5. Lever Spring Hammer
A lever-spring hammer is a quite light type of power hammer that is mostly used for small forgings. These types of hammers consist of a heavy frame with a vertical projection at its top which acts as a housing to bearing in which the laminated spring is found oscillating.
There are two ends of this string wherein one end is responsible for carrying a connecting rod and the other end a vertical tup. The tup is responsible for carrying the weight and moves vertically upwards and downwards within the fixed guides.
The connecting rod is attached with an eccentric sheave at its lower end. Further, the eccentric sheave is connected to the crank wheel which is responsible for operating the hammer and pressing the treadle downwards.
This is what makes the sheave rotate through the crank wheel and therefore the laminated spring starts oscillating in the bearing. This continuous oscillation of the spring leads the tup to move upwards and downwards. Therefore, the required blows are provided on the job and the hand lever is operated in order to adjust the stroke of the connecting rod and the intensity of blows.