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Knowledge Base


What is Hydraulics?
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control, and transmission of power by the use of pressurized liquids. Hydraulic topics range through most science and engineering disciplines, and cover concepts such as pipe flow, dam design, fluidics and fluid control circuitry, pumps, turbines, hydropower, computational fluid dynamics, flow measurement, river channel behavior and erosion. The word "hydraulics" originates from the Greek word hydraulikos.
What is a Hydraulic Press?
A hydraulic press is a machine for applying a large lifting or compressive force.
Who invented Hydraulic Press?
Joseph Bramah, of England invented and was issued a patent for his press in 1795. Joseph Bramah is also known for his development of the toilet flush and used to install toilets. He studied the existing literature on the motion of fluids and put this knowledge into the development of the press.
Principle driving Hydraulic Presses?
Pascal’s Law: Developed by French mathematician Blaise Pascal Pressure exerted anywhere in a confined fluid is transmitted equally in all directions throughout the fluid.
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Different types of Presses

  • Hydraulic Press: Working fluid is Hydraulic Oil
  • Pneumatic Press: Working fluid is Compressed Air
  • Mechanical or Power Press: Working by electric motor coupled with crank mechanism.
  • Hydro-pneumatic Press: Using both Compressed Air and Hydraulic Oil

Hydraulic Press Vocabulary

  • Bed - The main foundation and supporting structure upon which the operating parts of the machine are mounted and guided.
  • Bolster: A Bolster plate is attached to the top surface of the press bed.
  • Cylinder - Cylinder assembly consists of a cylinder, piston, ram, packing, and seals. Piston diameter and oil pressure determine the force (tonnage) that a given press can deliver.
  • Daylight - The clearance from the bolster bottom (when fully retracted) to press bed.
  • Frame - The main structure of the press containing the cylinder and the working surfaces.
  • Stroke - Stroke length can be set for any distance within the stroke limits of the cylinder. Adjustments include: top of stroke, pre-slowdown point, and bottom of stroke.
  • Throat Clearance - The distance from the vertical centerline of the ram to the frame member behind the bed. This distance determines the largest diameter piece that can be positioned with the part centerline under the center of the ram.
  • Moving Plate - A plate which is mounted on the cylinder Ram and moves when the cylinder extended.
  • Dual Push Buttons - A most common method of actuating hydraulic presses considering the safety of the operator.
  • Pendant: Electrical control device with Push Buttons Mounted
  • Work Height - The distance from the floor to the top of the bed.
How to select the right Hydraulic Press?

Know your Application

Different application requires different type of press for e.g. C Frame presses provide easy access from three sides; 4-column presses insure even pressure distribution. Straight-side presses offer the rigidity required for off-center loading in progressive die applications. The more critical the work, more demanding the tolerances, the greater should be the reserve tonnage capacity.

Keep in mind the various jobs to be performed on the press in future.

It is always a good idea to plan for a little higher capacity press in terms of tonnage, bed size and day light. In future the press can be re-tooled for any different application, if the need be.

Freeze your specifications of the press before taking quote from the vendor.

To cut short the time always be ready with the exact specifications of the press you are willing to order. Changing the specifications after talking to the vendor may consume un-necessary time of both the vendor and the customer.

Be ready with the drawings of your part

Providing the part drawings for which the press is to be used is always the best way to ensure that you would get a solution from the press manufacturer.
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Tonnage

Is the tonnage required in Hydraulic Press same as that required in a Mechanical Press? The Answer is “Yes”. The formula for calculating the tonnage is same in both cases. The tooling may be changed. But in the case of a hydraulic press you can adjust tonnage quickly and easily, by tuning the press to the right tonnage for each specific job.

Accessories

Hydraulic Press comes with a great deal of additional accessories to improve the productivity, safety and quality of the Press.

These commonly include

  • Automatic cycle controls
  • Linear Scales and Rotary Encoders
  • Limit switches and Proximity for distance reversal
  • Air-Oil Coolers or Water-Oil Cooler
  • Sliding beds
  • Rotary index tables
  • Die cushions
  • Ejection cylinders
  • Electronic safety curtains
  • Touch screen man machine interface
  • Servo system feedback for precise, consistent, repeatable stroke control
Why Hydraulic Presses?

Full power throughout the stroke

The full power of a hydraulic press can be delivered at any point in the stroke. Not only at the very bottom, as is the case with mechanical presses.

Lower operating costs

Hydraulic presses are relatively simple, and you may be surprised at the significant cost advantage over mechanical presses in comparable sizes. The numbers of moving parts are few, and these are fully lubricated in a flow of pressurized oil. Breakdowns, when they occur, are usually minor; not, for example, like a broken crankshaft. Replacements of packing, solenoid coils, and occasionally a valve, are typical maintenance items. Not only are these parts inexpensive, but also they are easily replaced without tearing the machine apart. This means more up-time and lower maintenance costs.

More capacity at lower cost

It is easier and less expensive to buy certain kinds of capacity in hydraulic presses. Extra stroke length is easy to provide. Daylight, too, can be added without much additional cost. Similarly, larger table areas and small presses with big bed areas can be provided. Large 200-ton presses with relatively small beds are available; tonnage of the press doesn't dictate what the bed size will be.

More control flexibility

Hydraulic press power is always under control. The ram force, the direction, the speed, the release of force, the duration of pressure dwell, all can be adjusted to fit a particular job. Jobs with light dies can be done with the pressure turned down. The ram can be made to approach the work rapidly, then shifted to a slower speed before contacting the work. Tool life is thus prolonged. Timers, feeders, heaters, coolers, and a variety of auxiliary functions can be brought into the sequence to suit the job. Hydraulic presses can do far more than just go up and down, up and down.
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More flexibility

A single hydraulic press can do a wide variety of jobs within its tonnage range. Commonly seen are deep draws, shell reductions, urethane bulging, forming, blank and pierce, stake, punch, press fits, straightening, and assembly. They are also used for powered metal forming, abrasive wheel forming, bonding, broaching, ball sizing, plastic and rubber compression, and transfer molding.

Better controls of speed and force

Hydraulic presses have major advantage of dwelling and ram speed control, which mechanical presses do not have. In mechanical presses the flywheel directly drives the stroke and there is no control over the speed and force. In a hydraulic press you gain greater control over ram action during stroke, making it more versatile for producing complex shapes. There may be different levels of sophistication in forming the desired shape and you want full control of speed force on the entire stroke. The hydraulic machines can be made with fully programmable control over ram speed and ram position, which is not possible in the mechanical press. For better material properties during forming and longer tool life, the adjustable and slower ram speed are necessary to optimize the material flow, which lead to better product quality. The full control over speed, position and dwell, produces better accuracy, crisp and clean shape and look.

Silent operation

Fewer moving parts and the elimination of a flywheel reduce the overall noise level of hydraulic presses compared to mechanical presses. Properly sized and properly mounted pumping units meet and exceed current Federal standards for noise, even with the pump under full pressure.

Because each phase of the ram movement can be controlled, noise levels can also be controlled. A hydraulic ram can be controlled to pass through the work slowly and quietly.

More compact

A typical 20-ton hydraulic press is eight feet high, six feet deep, and two feet wide. A 200-ton press is only ten feet high, nine feet deep, and a little over three feet wide. At ten times the capacity, the 200-ton press only takes up 50 percent more floor space. Hydraulic presses become less and less expensive compared to mechanical presses.

Low Maintenance

Having fewer moving parts makes Hydraulic Presses less prone to breakdowns. In case of Mechanical Presses the wear and tear of the moving parts is a great issue which is eliminated in the case of a Hydraulic Press.

Hydroforming

Hydroforming is one of the areas in which hydraulic presses have no competition. The hydraulic press ram moves down to close the die and the hydroforming high-pressure fluid fills and acts on to the inside of the tubular parts and expands it to fill the die. This operation requires dwell time at the bottom of the stroke to perform the hydroforming operation. The mechanical presses are not capable to carrying out the hydroforming operation, as they do not have the speed control and also the provision to stay on the bottom for performing the high pressure forming operations.

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The slower speed of the hydraulic press offers a big advantage in hydroforming process over mechanical press, as in hydroforming, tubular and sheet metal components are formed by liquid pressure, which reduce the number of operations and therefore producing the finished component in much lesser time. By hydroforming the components produced are more rigid as compared to the components produced by other processes.