A hydraulic press is a press machine that uses hydraulic pressure, or fluid pressure, in order to exert force on an object. Also known as Bramah presses, after their inventor Joseph Bramah, hydrolic presses depend on Pascal's principle; mainly, that the pressure throughout a closed system will act with equal force on all areas. As both the most common and most efficient type of industrial press, hydraulic presses apply a large lifting or compressing force that cannot be achieved using pneumatic presses or mechanical presses.
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.
C-Frame Guided Platen Drawing Presses - Savage Engineering & Sales, Inc.
Custom Compression Molding Hydraulic Presses - Phoenix Hydraulic Presses, Inc.
Plastic Molding Hydraulic Press - Macrodyne Hydraulic Presses & Automation
Industrial Hydraulic Press System - Macrodyne Hydraulic Presses & Automation
Hydraulic Press - Macrodyne Hydraulic Presses & Automation
200 Ton Roll-Bed Hydraulic Press - Phoenix Hydraulic Presses, Inc.
Hydraulic press, also known as Bramah press, follows Pascal's principle that states if you apply pressure to an enclosed fluid, it is transmitted to every part of the fluid, even to the walls of the container. The versatility, efficiency and dependability of hydraulics have made it, by far, the most common equipment found at numbers of facilities. They are classified based on design and application; for example, laminating presses, laboratory press, transfer press and forging presses are named after their application. Similarly, C-Frame Presses and H-frame presses are differentiated by the design.
The force achieved with hydraulic presses is unparallel, same force cannot be achieved with mechanical and pneumatic presses. There are many other advantages:
The cost of hydraulic press is significantly lower than the mechanical presses. Since hydraulic presses are simple and have fewer moving parts, they prove easy to maintain and troubleshoot, in comparison to other available options. If they breakdown parts, like crankshaft, packing and solenoid coils can be replaced easily without tearing down the machine apart. Moreover, hydraulic equipment and supplies can be easily available globally, this means low downtime and low maintenance cost.
Unlike other presses that deliver full power only at the bottom, hydraulic presses can relay full power at any point in the stroke. This eliminates the need to buy heavy 200-ton press just to deliver 100 tons force throughout the stroke. This advantage specially proved helpful in drawing operations.
A press designed to exert 100 tons of pressure, or less, if you have set it up that way, will exert that much pressure irrespective of mistakes one makes in setting it up. As an operator, you do not need to fret about overloading, smashing a die and breaking the press. These presses are designed in such a way that when a hydraulic press reaches its set pressure, it opens the relief valve at that limit; therefore, there is no danger of overload.
You can control and adjust many things in hydraulic press according to need, be it the duration of pressure dwell, the direction, ram force, the speed, and the release of force, all can be adjusted to align with the requirement. Hydraulic presses are designed to be applicable in a wide range job within its tonnage range, from deep draws to shell reductions, to straightening and assembly processes. They do far more than just going up and down.
Since the press does not need flying wheel and has fewer moving parts, it makes a lot lower noise than mechanical presses. The present day hydraulic presses with properly mounted pumping unit exceed the current Federal standards for noise. Therefore, complying with noise standards and regulation has never been an issue with hydraulic presses.
The built-in overload protection also serves well to tools. As the pressure is always same, there is no danger of damaging tools with overloading. The lacks shock, vibration and impact help auxiliary equipment, such as press brakes and machine guards, to last longer.
Presses get its name from the drive source that generates the pressure on the die to stamp a metal piece into finished product. It is self-explanatory that hydraulic press has a hydraulic system to create that pressure. They are used for making beverage cans and automotive parts, including many other things, by stamping aluminum, brass or high-strength steels based on the application. There is a range of hydraulic presses, including laminating presses, forging presses, laboratory press, C-frame presses, transfer press, machine guards, and compression press, that are designed for specific purposes.
In a simple hydraulic design, pressure is preset, and once that is achieved, a valve activates pressure reversal to stop overload. With this press design, there is no need of sophisticated guiding system, as the die tends to guide the press itself. They have application in deep-draw products, as the press applies full tonnage uniformly over the length of the stroke.
However, maintenance plays a big role in keeping hydraulic equipment running optimally and efficiently. Here we are discussing preventive maintenance measures that your operator should follow.
The thumb rule to know the condition of hydraulic presses is leaks. A leaky machine performs way below the capacity. An operator should check if there are leaks around the O-ring seals, the ram of the press, hydraulic lines, hose end fittings and valve seats. Only specific type of oil mentioned in the operator manual should be used in press. For smooth functioning and reducing wear and tear, hydraulic machines should be lubricated sufficiently, especially around seals.
A press in good condition can build working pressure in half or one second. If a press takes more than more than two to three seconds to build required working pressure, it indicates that either the press has issue with the pump or relief valve. However, mostly the problem is associated with the pump, only occasionally, the functioning of relief valve deters pressure build up. The common problems with valve include dirt in the line and too wide opening. The issue with pump is related to insufficient revolutions per minute creating not enough pressure.
Any unfamiliar sound must be investigated promptly to find the source and rectify it. The most common source of banging noises during the press operation is the valve shifts. Other noises can be because of insufficient lubrication.
The most common electronic problems with hydraulics presses are associated with coils and relays. Coils have a life cycle of 3 million strokes, where as relays are designed for 1 million strokes, and they should be replaced after that period. The replacement reduces troubleshooting effort and downtime. Records should be kept using hour meter and non-resettable cycle counter, as they help in maintenance of the machine. Other things that you have to care about are fittings, loose wires and frayed hoses, as frayed hoses and incorrect crimped fittings can lead to plumbing failures in any machines.
The easiest way to extend the life of hydraulic presses is to maintain oil and its temperature during operation. If press is run with low oil level and dirty oil, it can adversely affect the life. The best way to ascertain the presence of dirt in oil is to perform oil samplings, change filters if the oil has dirt particles in it.
Ideally, operational temperature of a press is around 120 degrees F, and if it gets higher than that, it starts to intervene in the operation. To maintain the optimum temperature, use air and water coolers. These units should be maintained properly, especially the radiator, which tends to attract dirt.
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.
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
- 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.