View A Video on Hydrualic Press - A Quick Introduction There are many different types of hydraulic press; each with its own set of applications, although there is some overlap. Those that use a ram and a solid, stable surface are considered
platen presses. For instance,
C-frame presses can be used for a variety of industrial operations including forming, straightening, blanking, punching, drawing and riveting. H-frame presses are used similarly for a wide range of industrial applications such as coining, crimping, bending, punching and trimming.
Laminating presses and
vacuum presses on the other hand, have a few specialized applications such as applying film to a variety of materials as well as encapsulating layers of materials in plastic for electronics industries, credit cards and identity cards.
Stamping presses, much like laminating presses, have specialized applications and are used for the two main purposes of shaping or cutting materials by deformation with a die for metalworking or automotive industries.
Transfer presses are used for the stamping and molding of plastic, rubber and metal such as in the medical and aerospace industries.
Press brakes cold work sheet metal and bend or fold them into different shapes. Forging presses are used to form only metal products.
A hydraulic press is a type of power press. Power presses can be pneumatic, hydraulic or mechanical. Pneumatic presses serve applications similar to hydraulic presses, including piercing, metal working, crimping, stamping, bending and punching. However, pneumatic presses use compressed air in order to gain movement and are not capable of creating the extremely high pressures of hydraulic presses. The various types of hydraulic presses are typically differentiated not only by application but by design and operation as well. C-frame presses can be operated manually or automatically and take up less floor space than most hydraulic presses due to their narrow but sturdy c-shaped frame, generally made from steel, which provides minimal deflection. H-frame presses differ from C-frame presses as a result of the welded H-shape of their frame as well as being able to handle multiple operations. Laminating presses are manually operated compression presses with two openings that are known as plates. One is used for heating whereas the other is used for cooling, thus making the lamination process faster as a result of the simultaneous cooling of one platen while heating the other. Transfer presses work by feeding flat plastic, rubber or metal blanks automatically into the right end of the press. From there, feed bar fingers take the part and move it from die to die. Most machines are designed to handle extremely heavy loads, reaching 3500 tons but they can also be small machines which can handle about 15 tons.
Hydraulic presses are powered by hydraulics, which provide force through fluid pressure. Consisting of the main components used in a hydraulic system, the basic form of a hydraulic press is comprised of a set of cylinders, pistons, also called punches, hydraulic pipes and a stationary anvil, or die. The piston, which is a mechanical device that provides a plunging or thrusting motion, uses liquid under pressure to exert a compressive force upon the anvil. The liquid is first forced into the cylinder by a pump or lever. The hydraulic system consists of two cylinders; the fluid, usually oil or water, is poured in the smaller of the two cylinders. This cylinder is often referred to as the slave cylinder. The small piston is located in this cylinder and is pushed so that it compresses the fluid that will then flow through a pipe into the larger cylinder, also known as the master cylinder. The pressure of the compressed liquid is then exerted on the larger cylinder and the larger piston in the master cylinder pushes the fluid back to the smaller cylinder. The force applied on the fluids in the smaller cylinder results in a larger force when pushed in the master cylinder. This force brings the punch in contact with the die, and deforms the material into the desired product shape. Typically constructed from stainless steel and other durable materials, hydraulic presses are available in both single and multi-station configurations. Single station presses consist of a single set of press tools, a die and punch, inside of a table. Multi-station presses have multiple sets of press tools, which either perform the same operation on many materials or perform various press operations on single or multiple materials as they move between stages.
Alternatives to hydraulic presses include mechanical presses, electric presses and pneumatic presses. Mechanical presses are driven by a flywheel which stores energy then releases it, thus transferring energy to the main slide by the use of mechanisms such as a crank, eccentric, knuckle joint or toggle. In a mechanical press, the stroke of the slide is adjustable within the limits of daylight. In addition, the strokes are also classified by the number of slides or ram they have, which can be single, double or triple action. All-electric presses are fairly recent developments, offering more efficient drive systems due to the mechanical linkage of the ram with the drive motor. This ensures that the controller is able to give a signal to the motor for a specific speed. If the motor is not overloaded then that speed will be reached. Also, the elimination of hydraulic fluid variations is beneficial because hydraulic fluid changes across time and temperatures, they can even vary within a single day. Pneumatic presses are advantageous because they can have stroke cycles of up to 400 strokes per minute, or SPM. Even at high stroke speeds, pneumatic presses are able to offer a controlled flow rate that makes them ideal for applications in which the material flow rate, or ram velocity, is crucial. Pneumatic presses do not convert rotary motion to linear motion and therefore have fewer moving parts than hydraulic press or machine presses. However, for applications requiring shear force and the ability to reach high pressure, hydraulic presses remain the best solution.
Hydraulic Press Types
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are used for seating stamping and removing bearings and other high-pressure
assembly, repair and production jobs.
-
use great pressure to secure or assemble parts together.
-
are streamlined-sized, press-shaped like a "C" and normally
consist of a single press application.
- use two plates being pushed together to compress the
material into the mold.
- Forging presses are hydraulically powered metal forming machinery that force metal
blocks to take the shape of a product by using a mold, extreme force
and pressure, and sometimes heat.
- ,
sometimes referred to as 4-column presses, are shaped like an "H"
and can often field more than one press application at a time.
- Hydrolic presses are industrial machines that use fluid pressure to exert force on an object.
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are smaller, single run presses used primarily in research laboratories
and other short and test run situations.
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are used for the lamination of polymers onto the surface of other materials
including lumber, metal and paper.
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refers to liquid injection molding presses which handle plastics that
are created via an injection process.
-
are used to shear, punch, form or assemble materials by using tools
or dies attached to slides or rams.
- Platen presses are large, industrial hydraulic presses that use two large, heated
steel plates to crush, condense, mold and form different products.
-
use energy transfers in the form of compressed airflow to control their
movements. Some typical application are shearing, punching, bending
and forming.
- are hydraulic powered machines that use tools and dies to shear, punch, and form metals.
- Press brakes are manual, mechanical or hydraulic pressing machines that cold work sheet metal into different bent or folded shapes. See here for a press brake calculator.
- are devices that use stamping dies.
-
apply pressure to metal in order to straighten it.
-
are used for the pressing of powdered materials into shaped tablets
or compacts.
- Transfer presses are hydraulic presses which automatically move parts from one stamping process to another using feed bar fingers.
- Vacuum presses are hydraulically powered industrial systems that use air pressure to
provide necessary force and air removal needed for laminating
applications.
Hydraulic Press Terms
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A device that converts fluid power into mechanical movement.
- The amount of time necessary
to wait between the molding and appraisal of molded part properties.
-
A defect at the parting line where the material has shrunk inside the
part.
- The
flat surface that supports the material being worked.
- Plates attached to
the rods that carry the platens or any structure mounted to the bed of
a press. It is sometimes removable.
- Any one of several
types of valves that allows flow in only one direction.
-
The lingering deformation after removal of the force, which compressed
the section. An example is when one uses a fingernail to depress a molded
sample; the impression that remains after a time is the compression set.
-
A feature of hydraulic systems that turns the system off and on at set
pressure points.
- The cylinder,
piston, ram, seals and packing of a press.
- The largest capacity,
vertically, that the press can handle or the vertical clearance from the
underside of the ram to the top of the bolster. The ram must be in its
maximum up position.
- The tooling used in a
press for shearing, punching, forming, drawing or assembling metal or
other materials.
- The final opening through
which injected material flows in order to enter a part cavity.
- Circulates air or water to maintain oil at operating temperature.
- Pressure
caused by fluid under applied force.
- Actuation devices that produce linear motion and force through the use
of pressurized hydraulic fluid.
- Pumps that use mechanical energy to deliver high-pressure fluid flow
to the outlet through pressurized fluid.
- A device that restricts the escape of fluid or entrance of foreign
material.
- A device that contains and transfers the flow and pressure of
hydraulic fluid in hydraulic power systems.
- Removes the part
from the punch/die.
- A press
function that allows it to operate continuously under 10% of its maximum
rated force, as well as to ensure a preheat function at reduced pressure.
- The place where the
mold attaches. It is a series of flat surfaces where one surface is stationary
and the other is moving.
- Long stem or
pole that connects two pieces of the press so that they act together.
- With the ram full
down, it is the clearance over the bed.
- The main feed guide
that runs from the outer face of an injection or transfer mold gate into
a single cavity mold or to runners in a multiple cavity mold.
- Feature that
controls the length of a stroke and can be adjusted accordingly.
- Distance
between the frame member behind the bed to the vertical centerline of
the ram. This measurement affects the size of the piece that can be used.
