Types and Working Principles of Servo Presse

Types and Working Principles of Servo Presses

Servo presses are presses driven and controlled by servo motors. Thanks to their digital motion control capability, servo presses allow precise programming of force, stroke, and speed, making them suitable for modern forming and press-fit applications that require high accuracy and flexibility.

In a typical servo press, the servo motor drives the mechanical transmission—such as a crank, connecting rod, screw, or hydraulic pump—while the control system manages motion profiles through pre-programmed curves. Even at low operating speeds, a servo press can reach its nominal rated force, enabling controlled forming without excessive impact.

Classification of Servo Presses

Servo presses can be broadly classified into four main types based on their drive and transmission mechanisms.

1. Servo Crank Press

A servo crank press is based on the traditional mechanical crank mechanism, where an eccentric shaft drives the slider in a sinusoidal motion. In conventional crank presses, the rated tonnage is typically reached before the bottom dead center, and the stroke length is fixed.

By replacing the conventional motor with a servo motor, the servo crank press introduces programmable motion control. This allows engineers to modify stroke profiles, dwell time, and speed at different positions, combining the high efficiency of mechanical presses with the controllability typically associated with hydraulic systems.

2. Servo Screw Press

Traditional friction screw presses rely on continuously rotating friction discs, resulting in high energy consumption and significant variability due to manual influence. Servo screw presses replace friction-driven mechanisms with servo motor control, greatly improving repeatability and energy efficiency.

In servo screw presses, the motor stops immediately when control voltage is removed, meaning energy consumption outside the actual pressing operation is minimal—often reduced by around 60% compared to friction presses. This design enables stable operation, precise energy delivery, and rapid short-stroke forming, making servo screw presses suitable for hot forging and refractory forming applications.

3. Servo Hydraulic Press

Servo hydraulic presses use a servo motor to drive the hydraulic pump directly, controlling oil flow and pressure without traditional proportional valves. This approach significantly simplifies the hydraulic circuit while improving response accuracy.

Compared with conventional hydraulic presses, servo hydraulic presses offer lower noise, reduced energy consumption, improved flexibility, and higher overall efficiency. They are widely used in processes such as die forging, stamping, press fitting, and straightening.

Servo hydraulic press technology was developed earlier in Japan and Europe and has already entered large-scale industrial application in these regions. In comparison, domestic development is still progressing, with only a limited number of manufacturers achieving mature servo hydraulic solutions.

Engineering Perspective on Servo Press Selection

Each type of servo press has its own mechanical characteristics and application boundaries. Selecting the appropriate servo press requires evaluating process requirements such as force profile, stroke control, cycle time, energy efficiency, and part consistency—rather than relying on a single “universal” solution.