What is a hydraulic press and how does it work?
A hydraulic press is a forming machine that converts oil pressure in a closed circuit into force by Pascal's principle: a pump delivers oil under pressure to the main cylinder, the piston drives the ram carrying the upper die, and the force is applied to the workpiece. Pressure × piston area = force; the larger the area, the more tonnage the same pressure produces.
How does it work?
A cycle completes in three stages. Closing: the ram descends fast and unloaded — this stage does not affect part quality, it only shortens the cycle. Working: when the die touches the part, speed drops and pressure rises; while the material flows, the force is available at every point of the stroke. Return: the directional valve reverses the circuit and the ram travels back up. Working pressure sets the force, pump flow sets the speed — the two are designed independently.
How does it differ from a mechanical (eccentric) press?
An eccentric press strikes with the energy stored in a flywheel, through a crank: it is fast, but delivers full tonnage only close to bottom dead centre. The advantage of the hydraulic press is not speed but control: nominal force at any desired point of the stroke, speed profiled to the part, the stroke stopped wherever needed, and blank-holder force set independently of the drawing force. That is why deep drawing, hot moulding, composites and sizing are done on hydraulic presses.
Main components
- Frame — the steel structure that carries the force; open-gap C-frame or closed H-frame.
- Main cylinder and ram — the piston that produces the force and the moving mass that carries the upper die.
- Hydraulic power unit — pump, motor, oil tank, valve group and cooling.
- Cushion (ejector) — the second circuit that restrains the blank in deep drawing and ejects the part in forming.
- Controls — PLC/HMI: recipes, speed-force profiles, the safety chain.
All the terms — daylight, stroke, net usable area, cushion stroke — are defined in the press glossary.
How do you choose the right press?
Tonnage is not picked from a catalogue; it is calculated from the part's material, thickness, formed area and the type of process. The same part asks for one force in deep drawing and another in cutting. Frequent questions are on the FAQ page; share your part drawing and the technical quotation is prepared with tonnage, bolster and stroke. ÖZKOÇ has built hydraulic presses in İstanbul since 1964, from 70 to 7,000 tonnes — all 16 press families are here.