Core Classification and characteristic analysis of Hydraulic press drive technology

At present, the mainstream hydraulic press drive technologies in the industry mainly fall into two categories: pump-accumulator drive and direct pump drive. These two drive paths are suitable for hydraulic press products of different tonnages and application scenarios, and their technical characteristics are significantly different.

Ⅰ. Pump-Accumulator Drive Technology

Pump-accumulator drive is an early popularized drive method for large traditional hydraulic presses. Its technical core is to store the high-pressure working fluid output by the hydraulic pump through the accumulator and release the stored high-pressure oil during the equipment operation stage to supplement the instantaneous flow demand of the system. The advantage of this drive mode lies in the fact that the capacity of the hydraulic pump and the drive motor can be selected based on the average usage of the high-pressure working fluid, without the need to configure a high-power motor according to the peak flow rate, thus reducing the initial installation cost of the equipment.

However, from the perspective of technical characteristics, pump-accumulator drive has inherent limitations: on the one hand, the system output pressure is always maintained at the high-pressure level of the accumulator and does not automatically adjust with load changes. Regardless of the size of the processing load, the system always maintains a high-pressure output, resulting in a large amount of energy waste. The overall power consumption is much higher than that of direct pump drive. On the other hand, the system structure is complex, requiring the configuration of large-capacity energy storage devices, intricate pipelines and control valve groups. The equipment occupies a large area, has high maintenance costs, and has relatively low pressure control accuracy, making it difficult to meet the demands of high-precision processing. At present, this technology is mainly applied to traditional large-tonnage free forging hydraulic presses. One drive system can simultaneously drive multiple hydraulic presses, which to a certain extent offsets its inherent defects.

Ⅱ. Direct Pump Drive Technology

The direct drive technology of the pump eliminates the energy storage device. The high-pressure working fluid is directly delivered to the hydraulic cylinder by the hydraulic pump. The supply direction of the fluid is changed through the distribution valve, and the relief valve limits the maximum pressure of the system and achieves safe overflow. This drive mode has fewer links and a simple structure. The system working pressure can be automatically increased or decreased according to the actual load demand, with no excess pressure loss. Compared with accumulator drive, it can significantly reduce power consumption.

With the development of hydraulic control technology, direct pump drive has given rise to multiple technical branches, catering to the demands of various scenarios: Small and medium-sized general-purpose hydraulic presses generally adopt the traditional scheme of a fixed displacement pump combined with a relief valve, which features a simple structure and low cost, making it suitable for general processing scenarios with low energy consumption requirements. Medium and high-end hydraulic presses are gradually adopting variable pump drive schemes. By adjusting the pump's displacement to meet the load flow requirements, overflow losses are reduced, and the energy consumption level is superior to that of fixed displacement pump schemes. In recent years, the emerging servo direct drive pump control solution, which directly drives the hydraulic pump with a servo motor and regulates the system flow and pressure by changing the motor speed, further amplifies the energy-saving and precision advantages of direct pump drive, and has become the mainstream development direction of current hydraulic press drive technology.

Servo direct drive pump-controlled drive technology: A core technological breakthrough of contemporary hydraulic presses

Servo direct drive pump-controlled drive technology is a representative achievement of the integration of mechanics, electricity and hydraulics, and also the most core technological breakthrough of the new generation of hydraulic presses. It has completely solved the pain points of high energy consumption, low precision and high noise of traditional hydraulic presses.

Ⅰ. Working Principle of Servo Direct Drive Technology

The core logic of the servo direct drive pump control system is "energy supply on demand", where the servo motor directly drives the hydraulic pump, eliminating the high-pressure throttling link in the traditional valve control system. After the user sets the required pressure, speed and stroke parameters for processing through the human-machine interaction interface, the PLC converts the parameters into control electrical signals and sends them to the servo driver to drive the servo motor to rotate. The system collects the current system pressure and slider position data in real time through pressure sensors and grating rulers, and feeds it back to the controller. The deviation is calculated through the PID algorithm, and the speed and torque of the servo motor are dynamically adjusted to achieve precise closed-loop control of the system flow and pressure.

This control method fundamentally eliminates the energy loss and oil temperature rise problems caused by high-pressure throttling in traditional valve-controlled systems. During the pressure-holding stage, the servo motor can reduce its rotational speed to an extremely low level, only replenishing the system leakage. During the no-load stage, the motor can be shut down with almost no energy consumption. Overall, compared with traditional hydraulic presses, it can save 30% to 70% of electricity, and the energy-saving effect is very significant.

Ⅱ. Core Technical Advantages of the Servo Direct Drive System

Compared with traditional drive schemes, the servo direct drive pump control system has achieved performance leaps in multiple dimensions:

1. Significantly improved control accuracy: Through full closed-loop feedback control and high-speed algorithms, the repeat positioning accuracy of the servo hydraulic press can reach ±0.03mm, and the pressure control accuracy does not exceed 1%, which can meet the high-precision processing requirements of power battery structural components, precision electronic components, etc., far exceeding the precision level of traditional hydraulic presses.

2. Production efficiency and flexibility improvement: The servo system has a fast response speed, with a response frequency of up to 200Hz, which is dozens of times that of the traditional hydraulic system. It can achieve a faster action rhythm. The working rhythm of a common stamping servo hydraulic press can reach 10 to 15 times per minute, meeting the efficiency requirements of batch production. Meanwhile, parameter adjustment can be completed with one click through the program, and the time for model change adjustment is short, which is suitable for the flexible production needs of multiple varieties and small batches.

3. Optimized operation experience: The direct drive of the servo motor eliminates intermediate transmission links such as couplings and pulleys, increasing mechanical efficiency to over 95%. The operation noise can be reduced from 85dB in traditional systems to below 65dB. At the same time, it reduces mechanical wear, slows down the oil temperature rise, extends the service life of sealing elements and hydraulic oil, and lowers maintenance costs.

At present, servo direct drive technology has been widely applied in multiple fields such as precision stamping, die forging, press-fitting, and straightening, covering high-end manufacturing industries including automobiles, new energy, electronics, lithium batteries, and home appliances. Particularly in the processing of structural components for new energy vehicle power batteries, servo hydraulic presses have become mainstream standard equipment.