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What is a <a href="https://huntermachinery.com/" target="_self">Hydraulic Press</a>?
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A hydraulic press is a mechanical device that uses the static pressure of a liquid, as defined by Pascal‘s principle, to shape, deform, and configure various types of metals, plastics, rubber, and wood. The mechanism of a hydraulic press consists of a mainframe, power system, and controls.
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Pascal‘s principle states that when pressure is applied to a confined liquid, a pressure change occurs in the liquid. For a hydraulic press, the pressure in a liquid is applied by a piston that works like a pump to create mechanical force.
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Chapter Two: How a <a href="http://www.huntermachinery.com/vertical-hydraulic-press-machine/" target="_self">Hydraulic Press Machine</a> Works
The process of a hydraulic press begins when a hydraulic fluid is forced into a double acting piston. The compressive force inside the small hydraulic cylinder pushes the fluid into a larger cylinder where more force and pressure are applied. The movement of the larger piston forces the fluid back into the smaller piston cylinder.
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The passage of the fluids between the two pistons creates increased pressure that produces mechanical force to drive the anvil on a hydraulic press downward onto a workpiece that is deformed to produce a desired shape. Once the movement is complete, the pressure is released and the anvil returns to its original position.
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How a Hydraulic Press Works
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The components of a hydraulic press include two cylinders, two pipes, and two pistons. One of the cylinders is the ram and the other is the plunger; they are connected by a chamber that is filled with hydraulic fluid.
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Ram
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In many hydraulic systems, several rams are used, the number of which depends on the working load. Multiple small rams are preferred over a single larger one to allow for better control over the thrust force. Fluid is supplied to the ram by a pump and hydraulic accumulator that works between the rams and the pump.
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Accumulator
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The accumulator stores hydraulic pressure as a fluid, which is released when required. The configuration of a hydraulic accumulator is a cylinder with a piston that is spring loaded or pneumatically pressurized. The pump continuously pumps hydraulic fluid into the accumulator to keep the pressure in it constant. The inlet of the accumulator is attached to the pump, while the outlet is attached to the machine.
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Without the accumulator, the pump would have to be continually running. The accumulator helps avoid this by serving as a storage container for the energy needed to operate the machine.
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Pump
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The three types of hydraulic pumps are vane, gear, and piston with piston pumps being the most commonly used. The pumps for a hydraulic press are a positive displacement pump, which means they deliver a constant amount of fluid with each pumping cycle. The positive displacement pump can be fixed or variable with a fixed pump working at a constant speed while a variable pump changes speeds and can be reversed.
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The reason that piston pumps are best suited for hydraulic presses is their ability to perform in high pressure hydraulic systems. The pump operates at large volumetric levels due to its low fluid leakage. The types of piston pumps include axial, bent axis, and radial.
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Cylinders
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The number of cylinders in a <a href="http://www.huntermachinery.com/vertical-hydraulic-press-machine/single-column-hydraulic-press/" target="_self">single column hydraulic press</a> varies according to its design. The function of the cylinders is to generate the compressive force that drives the anvil and die. In a two cylinder design, the diameter of the cylinder that carries the ram is larger, while the diameter of the second cylinder that carries the plunger is smaller. Cylinders are metal pipes with two ports for the input and output of hydraulic fluid.
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The cylinders are connected by a pipe containing hydraulic fluid. When the plunger in the small cylinder applies pressure to the hydraulic fluid through a downward action, the created pressure is applied to the ram. The action in the smaller cylinder by the downward movement of the plunger is that of a mechanical actuator used to produce unidirectional force by a unidirectional stroke.
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Hydraulic Press Process
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The mechanical results of the pressure created in the hydraulic system can be seen in the animation below where a plane slug is placed under the anvil, and pressure created by the cylinders drives the ram that drives the anvil down into the slug and forces it into the die.
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Types of Hydraulic Presses
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Hydraulic presses play a major role in the fabrication, assembly, and production of components for machinery and parts for commercial and industrial products. The differences between the types of hydraulic presses are determined by several factors, which include their frame and the metals used to manufacture them.
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