A flexible control method for forging press

Abstract

The present invention relates to the technical field of hydraulic presses, and in particular discloses a flexible control method for a forging press, comprising the following steps: S1, using a control panel of the forging press to send a start signal to a controller, and after receiving the start signal, the controller controls a filling mechanism of a hydraulic system to fill a liquid storage chamber with liquid, so that a system pressure is generated in the liquid storage chamber of the forging press; S2, using a hydraulic system to drive a slider to close a mold, before the slider reaches a speed change point, the controller outputs a signal to the hydraulic system to change the pressure and flow of the liquid in the liquid storage chamber, after the slider reaches the speed change point, the controller outputs a fixed-value pressure and flow signal to the hydraulic system, and the hydraulic system drives the slider to change the working state until the slider works to the surface of the material; S3, when the slider works to the surface of the material and starts to increase pressure, the controller controls the hydraulic system to output the pressure and flow signals of the liquid in the liquid storage chamber in sections and gradually decreases until the pressure reaches a preset value.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic presses, and in particular discloses a flexible control method for a forging press. Background Art

[0002] Traditional hydraulic press control solutions mainly use position control or rough pressure control, and most of them only optimize a single action. This control method has significant deficiencies in product molding technology, because position control has limited structural influence on product molding, while the internal molecular structure differences and pressure change speed of different pressure sections in the material plastic process are crucial to the molding results. Traditional solutions fail to accurately control pressure changes, resulting in unstable product molding quality. In addition, the position control of traditional hydraulic presses is mostly fixed-value proportional deceleration, and there is a lot of vibration when switching speeds, which affects equipment stability and product accuracy.

[0003] For example, the invention publication number is: CN117621533A, and the patent name is: A control method for the rapid descent of a composite hydraulic press slider, the hydraulic press slider is driven by a main hydraulic cylinder and a return hydraulic cylinder; the main hydraulic cylinder replenishes the hydraulic medium to the working chamber through a filling valve when the slider is rapidly descending; the return hydraulic cylinder adjusts the hydraulic medium discharged from the working chamber through a proportional throttle valve when the slider is rapidly descending; the balancing hydraulic cylinder is used to offset part of the gravity of the slider assembly, and the medium pressure in the working chamber of the balancing hydraulic cylinder is adjusted by an accumulator; the back pressure valve is used to adjust the medium pressure in the working chamber of the return hydraulic cylinder during the working stage of the slider;

[0004] The working chamber of the main hydraulic cylinder is connected with the b port of the charging valve and the hydraulic system supply port; the working chamber of the return hydraulic cylinder is connected with the a port of the proportional throttle valve, the a port of the back pressure valve and the hydraulic system supply port; the a port of the charging valve, the b port of the proportional throttle valve and the b port of the back pressure valve are connected with the medium collection box; the working chamber of the balance hydraulic cylinder is connected with the accumulator oil port; xs are the displacement, velocity and acceleration of the slider respectively; pa is the medium pressure in the working chamber of the main hydraulic cylinder, and Aa is the working area of ​​the main hydraulic cylinder; pb is the medium pressure in the working chamber of the return hydraulic cylinder, and Ab is the working area of ​​the return hydraulic cylinder; pc is the medium pressure in the working chamber of the balance hydraulic cylinder, and Ac is the working area of ​​the balance hydraulic cylinder; xs is detected by a displacement sensor; pa, pb and pc are detected by pressure sensors; and are obtained by numerical differentiation calculation.

[0005] This invention patent flexibly handles the process of the hydraulic press from fast to slow by adjusting the switching amount of the proportional valve, effectively reducing the impact of the hydraulic press from fast to slow and smoothly transitioning the action. However, the adjustment accuracy and response speed of the proportional throttle valve are not enough to cope with complex working conditions, resulting in the slider's movement accuracy and stability being affected during the switching process between the fast downward and working forward stages. Summary of the invention

[0006] In order to overcome the shortcomings and deficiencies in the prior art, an object of the present invention is to provide a flexible control method for a forging press to solve the above technical problems.

[0007] To achieve the above object, a flexible control method of a forging press according to the present invention is characterized by comprising the following steps:

[0008] S1, using the control panel of the forging press to send a start signal to the controller, and after receiving the start signal, the controller controls the filling mechanism of the hydraulic system to fill the liquid storage chamber, so that the system pressure is generated in the liquid storage chamber of the forging press;

[0009] S2, using the hydraulic system to drive the slider to close the mold. Before the slider reaches the speed change point, the controller outputs a signal to the hydraulic system to change the pressure and flow rate of the liquid in the liquid storage chamber. After the slider reaches the speed change point, the controller outputs a fixed pressure and flow rate signal to the hydraulic system, and the hydraulic system drives the slider to change the working state until the slider is fed to the material surface;

[0010] S3, when the slider moves to the material surface and starts to increase pressure, the controller controls the hydraulic system to output the pressure and flow signals of the liquid in the liquid storage chamber in sections and gradually decreases until the pressure reaches the preset value.

[0011] Furthermore, the flexible control method of the forging press also includes the following steps:

[0012] S4, when the pressure reaches the preset value, the controller controls the slider to remain stationary through the hydraulic system to maintain the pressure. After the pressure maintenance is completed, the controller controls the pressure relief valve to open to release the liquid in the liquid storage chamber;

[0013] S5, after the liquid in the liquid storage chamber is released and the pressure is eliminated, the controller controls the hydraulic system to drive the slide block to open the mold until the return stroke stops.

[0014] Furthermore, in step S2, the changing flow signal output by the controller changes once every 95-105 ms.

[0015] Furthermore, in the step S2, the speed change point of the slider is a fast-to-slow speed change point, and the controller controls the hydraulic system to drive the slider to quickly close the mold until the slider reaches X millimeters away from the fast-to-slow speed change point. The controller starts to transmit a flow signal to the hydraulic system to reduce the closing speed of the slider, so that the slider enters a slow working state.

[0016] Furthermore, the value range of X is 5mm-45mm.

[0017] Furthermore, during the mold opening process of the slider in step S5, a return stop point is pre-set by the controller. When the pressure in the liquid storage chamber is eliminated, the controller controls the hydraulic system to drive the slider to open the mold smoothly at an increasing speed. When the slider is Y mm away from the return stop point, the speed begins to decrease until the slider is in a stationary state without rebound.

[0018] Furthermore, the pressure value range of the fixed-value pressure signal output by the controller is 5MPa-20MPa, and the flow value range of the fixed-value flow signal output by the controller is 10L / min-50L / min.

[0019] Furthermore, the increasing speed range of the slider during the mold opening process is 0.1m / s-1m / s, and the return speed range is 0.5m / s-2m / s.

[0020] Furthermore, the proportional valve and servo valve in the hydraulic system form a closed-loop control with the pressure sensor and the displacement sensor, and the pressure data is sampled and analyzed every Z milliseconds as a cycle. Then, the controller calculates the deceleration ratio of the slider according to the pressure change value within the cycle and uses the deceleration ratio to control the hydraulic system to drive the slider to decelerate. When the pressure change stops, the slider moves to the material surface.

[0021] Furthermore, in step S5, when the slider is performing the return motion, the controller monitors the slider displacement in real time through pulse position detection. When the slider is within a certain range from the return stop point, a deceleration control signal is output, and the speed of the slider gradually decreases from a fast return to a stable stop state. The whole machine action completes the closed loop, and the hydraulic system enters a standby state, waiting for the next cycle command.

[0022] The flexible control method of the slider of a servo high-speed forging hydraulic press of the present invention is connected to the electrical signal of the controller through the control panel to receive the start command of the operator. After the controller analyzes the command, it activates the filling mechanism in the hydraulic system, including a fast filling device and a logic valve, and injects hydraulic oil into the liquid storage chamber through a hydraulic pump and a pipeline to establish system pressure. The pressure sensor monitors and feeds back the pressure in the liquid storage chamber to ensure its stability. The mold closing action of the slider is driven by the hydraulic system, and the speed is adjusted by the proportional valve and the servo closed-loop control system. When approaching the speed change point, the controller dynamically adjusts the pressure and flow signals according to the sensor data to achieve flexible deceleration and stable working progress of the slider. During the pressurization process, the pressure and flow are linearly controlled in sections by the servo system and the proportional valve to ensure the uniformity of material forming. After the pressure is maintained, the pressure relief valve releases the pressure smoothly, the slider opens the mold, and the displacement sensor and the servo system control the return action of the slider until it stops accurately.

[0023] Beneficial effects of the present invention: The scheme of the present invention significantly improves the operating accuracy and forming quality of the forging press by introducing flexible control algorithms and servo closed-loop control. The pressure and flow control of the system is more precise, reducing oil circuit impact and mechanical vibration, thereby reducing the oil circuit leakage rate and the breakage rate of mechanical structural parts, and improving the overall life and reliability of the hydraulic press. In addition, the whole machine runs more smoothly and with lower noise, enhancing the user experience. The interlocking mechanism of position and pressure also improves the safety of the hydraulic press during mold closing, ensuring the safety of the operator and the normal operation of the equipment. Through this flexible control method, it can adapt to different process requirements, improve the versatility and flexibility of the equipment, and bring higher production efficiency and lower maintenance costs to users. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic flow chart of the flexible control method of the forging press of the present invention;

[0025] Figure 2 It is a structural schematic diagram of a forging press adopting the flexible control method of the present invention;

[0026] Figure 3 It is a pseudo code schematic diagram of the controller in the flexible control method of the forging press of the present invention.

[0027] Reference numerals include:

[0028] 1. Forging press; 2. Support seat; 3. Controller; 4. Hydraulic system; 5. Control panel; 11. Main oil cylinder; 12. Upper ejector device; 13. Lower ejector device; 14. Filling mechanism; 21. Auxiliary oil cylinder; 22. Upper die connecting seat; 23. Lower die connecting seat. DETAILED DESCRIPTION

[0029] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments and drawings. The contents mentioned in the implementation modes are not intended to limit the present invention.

[0030] See also Figures 1 to 3 As shown, a flexible control method of a forging press of the present invention comprises the following steps:

[0031] S1, the control panel 5 of the forging press 1 is connected to the controller 3 by electrical signals, as an interface for manual input, when the operator triggers the start signal, the controller 3 parses the start command through the signal receiving module and transmits it to the hydraulic system 4. The filling mechanism 14 in the hydraulic system 4 includes a fast filling device and a logic valve, which quickly injects hydraulic oil into the liquid storage cavity through a hydraulic pump and a hydraulic pipeline, and uses a pressure sensor to monitor the pressure change in the liquid storage cavity in real time to ensure that the system pressure is stable within a preset range, so as to provide a power source for the subsequent actions of the slider.

[0032] S2, the rapid mold closing process of the slider is driven by the hydraulic system 4, which jointly adjusts the running speed of the slider through the proportional valve and the servo closed-loop control system. Before the slider approaches the speed change point, the controller 3 outputs the adjusted pressure and flow signals through the real-time monitoring data of the pressure sensor and the displacement sensor, so that the speed and pressure of the slider change dynamically. The speed change point is controlled by the fast-to-slow logic switching node. When the slider reaches the set speed change point, the controller 3 switches to the fixed value output mode to ensure that the slider enters the slow working state. At the same time, the flexible deceleration algorithm is used to avoid mechanical shock and achieve stable working action.

[0033] S3, after the slider moves to the material surface, the controller 3 performs linear segmented control on the hydraulic system 4 through the servo system and the proportional valve, and gradually outputs the pressure and flow signals of the liquid in the liquid storage chamber. The entire pressurization process is performed by the pressure sensor with a sampling period of Z milliseconds for real-time pressure detection. When the pressure change reaches the preset end value, the controller 3 stops the pressurization signal to ensure the uniformity of the plastic pressure of the material during the molding process and avoid surface defects on the workpiece.

[0034] Specifically, the flexible control method of the forging press further includes the following steps:

[0035] S4, when the pressure in the liquid storage chamber reaches the preset value, the controller 3 keeps the slider stationary through the proportional valve and servo valve in the hydraulic system 4, and starts the pressure holding program. At this time, the slider remains stationary to eliminate the internal tension of the material and ensure the accuracy of the molding size. After the pressure holding is completed, the controller 3 activates the superimposed pressure relief valve to steadily release the liquid pressure in the liquid storage chamber through the hydraulic pipeline, and the slider is ready to open the mold.

[0036] S5, when the pressure of the liquid in the liquid storage chamber is eliminated, the controller 3 dynamically controls the mold opening process of the slider through the displacement sensor and the servo system. The slider initially moves upward smoothly at an increasing speed, and the pressure in the liquid storage chamber is gradually released through logical control. When the slider approaches the return stop point Y mm, the controller 3 automatically outputs a decreasing signal, the slider speed gradually slows down, and finally stops at the set stop point, i.e., the origin, to avoid rebound.

[0037] Specifically, in step S2, the controller 3 outputs a changing flow signal to adjust the movement speed of the slider. According to the requirements of the forging process and the dynamic response characteristics of the hydraulic system 4, the adjustment period of the flow signal is set to 90-120ms. This period is short enough to ensure smooth changes in the slider speed while avoiding excessive impact on the hydraulic system 4. In this process, the controller 3 accurately calculates the required flow change based on the current position of the slider and the preset process parameters, and adjusts the flow of the hydraulic oil in real time through the proportional valve or servo valve. The most suitable data can be determined based on the actual application scenario and system test results.

[0038] Specifically, during the operation of the forging press 1, the slider switching from fast die closing to slow working speed is a critical speed change point. According to the specific requirements of the forging process, the controller 3 will begin to intervene at X millimeters before the slider approaches this speed change point, and adjust the flow signal to reduce the slider's die closing speed. The value range of X is set to 5mm-45mm, and fine-tuning is allowed according to different materials and processes. In the interval of 5mm to 45mm from the speed change point, the controller 3 gradually reduces the hydraulic oil flow rate to allow the slider to decelerate smoothly and avoid impact on the material or mold. The controller 3 uses a built-in algorithm to accurately calculate and output the corresponding flow signal based on the feedback from the pressure sensor and the displacement sensor, and adjusts the flow rate of the hydraulic oil through a proportional valve or a servo valve to achieve a smooth transition of the slider speed.

[0039] By precisely controlling the speed change point of the slider in step S2, the solution of the present invention significantly improves the control accuracy of the forging process and the product quality. Compared with the prior art, this flexible control method effectively reduces the mechanical impact and noise during the forging process, reduces the wear of the mold and equipment, and thus extends the service life of the equipment. In addition, by reducing the impact, the method also helps to improve the molding quality of the material and reduce the surface defects of the product, such as cracks and deformation.

[0040] Specifically, in step S5, the return action of the slider is precisely managed by the controller 3 to ensure that it stops smoothly and accurately at the predetermined position. The return stop point Y preset by the controller 3 is determined according to the requirements of the forging process and the dynamic characteristics of the mechanical structure. During the implementation process, when it is detected that the pressure in the liquid storage chamber is eliminated, that is, the signal indicates that the slider has completed the pressure maintenance and is ready to open the mold, the controller 3 immediately starts the return action. The slider first starts to open the mold smoothly at an increasing speed. The speed at this stage is controlled between 0.1m / s and 1m / s to ensure the smoothness of the action.

[0041] As the slider approaches the return stop point, the controller 3 gradually reduces the speed. When the slider is Y mm away from the stop point (the range of Y can be set between 5mm-45mm to adapt to different process requirements and mechanical characteristics), the controller 3 outputs a decreasing signal to decelerate the slider until it is completely stationary and achieves a rebound-free state. This process involves precise control of the flow control valve and proportional valve in the hydraulic system 4 to achieve smooth speed changes and precise stops.

[0042] By precisely controlling the return stop point of the slide, workpiece damage or mold damage caused by excessive travel or rebound can be avoided, thereby improving product quality and consistency. In addition, smooth mold opening and precise stopping also help reduce noise and vibration, improve the working environment, and increase production efficiency.

[0043] In the flexible control method of the forging press of this embodiment, the controller 3 is responsible for outputting accurate fixed-value pressure and flow signals to meet the requirements of a specific forging process. Specifically, the fixed-value pressure signal range output by the controller 3 is set to 5MPa to 20MPa, which covers the pressure range required for most forging applications, and can ensure effective forming of the material while avoiding excessive load on the mold and equipment.

[0044] At the same time, the fixed flow signal output by the controller 3 ranges from 10L / min to 50L / min, ensuring that the hydraulic system 4 can provide sufficient flow to drive the slider to complete the mold opening and return movements while maintaining the stability and efficiency of the system. During the mold opening process, the slider's incremental speed is controlled between 0.1m / s and 1m / s. This speed range is intended to achieve smooth acceleration of the slider and avoid mechanical shock caused by starting too quickly. In the return stage, the slider's speed range is set to 0.5m / s to 2m / s. This wider speed range allows the slider to return quickly according to actual process requirements, thereby improving production efficiency.

[0045] Specifically, in the hydraulic system 4 of the forging press 1, the proportional valve and the servo valve are used as actuators, and together with the pressure sensor and the displacement sensor, they form a closed-loop control system. The proportional valve and the servo valve can accurately adjust the flow and direction of the hydraulic oil according to the electrical signal sent by the controller 3, thereby controlling the movement of the slider. The pressure sensor monitors the pressure in the liquid storage chamber in real time, and converts the pressure data into an electrical signal and sends it to the controller 3. The displacement sensor monitors the position change of the slider. The controller 3 samples and analyzes these data in a cycle of every Z milliseconds. The value of Z can be set according to the requirements of the system response speed, for example, it can be set to 50 milliseconds to ensure sufficient control accuracy and response speed.

[0046] When the slider approaches the material surface, the controller 3 calculates the required deceleration ratio of the slider based on the pressure change value fed back by the pressure sensor. This deceleration ratio takes into account the requirements of the forging process, the material properties and the performance of the equipment. The controller 3 then adjusts the opening of the proportional valve and the servo valve to reduce the flow of the hydraulic oil and the speed of the slider to achieve precise control of the slider's deceleration. When the pressure change tends to be stable, that is, the pressure reaches the preset value, the slider advances to the material surface at a controlled speed and is ready for forging operations.

[0047] This closed-loop control method significantly improves the control accuracy and response speed of the forging press 1. Compared with the traditional open-loop control system, the closed-loop control can adjust the control strategy in real time to adapt to the changing process conditions, thereby reducing the impact and vibration during the movement of the slider and improving the forming quality of the workpiece. In addition, precise speed control helps to reduce energy consumption and improve the working efficiency of the hydraulic system 4. The closed-loop control also enhances the stability and reliability of the system, reduces the risk of equipment failure due to pressure fluctuations or mechanical deviations, and extends the service life of the equipment. In general, this control method provides higher flexibility and automation level for the forging process, meeting the needs of modern manufacturing for high precision and high efficiency.

[0048] Specifically, in step S5, the return motion of the slider is precisely managed by the controller 3 to ensure that it stops smoothly and accurately at the predetermined position. The controller 3 uses a pulse position detection system, which may include an encoder or a grating ruler and other devices, to monitor the displacement of the slider in real time. The position information provided by the pulse position detection system is transmitted to the controller 3 in the form of pulse signals, and the controller 3 calculates the current position and speed of the slider based on these signals.

[0049] When the slider approaches the return stop point and is within a certain range (for example, it can be set to 10 mm) from the point, the controller 3 starts to output a deceleration control signal. These signals adjust the proportional valve and servo valve in the hydraulic system 4 to reduce the flow of hydraulic oil to the hydraulic cylinder, thereby reducing the speed of the slider. The controller 3 dynamically adjusts the signal based on the preset deceleration curve and actual position feedback to ensure that the slider gradually decelerates from the fast return to a stable stop state.

[0050] The scheme of the present invention realizes flexible control of the movement of the slider by precisely controlling the hydraulic system 4 of the forging press 1. After receiving the start signal from the operator, the controller 3 activates the filling mechanism 14 in the hydraulic system 4 to establish the system pressure. Through the proportional valve and the servo closed-loop control system, the controller 3 dynamically adjusts the speed and pressure of the slider to achieve a smooth transition from fast mold closing to slow working. After the slider is worked to the surface of the material, the controller 3 gradually reduces the pressure and flow through linear segmented control to ensure the uniformity of the plastic pressure of the material. After the pressure maintenance is completed, the slider returns smoothly and finally stops accurately at the set position to complete the closed-loop control.

[0051] Specifically, see Figure 3 The following describes how the flexible control method of the scheme of the present invention realizes flexible control of the forging press 1 in combination with the forging press in the figure and the flexible control method of the present invention.

[0052] The forging press 1 in the figure mainly includes a three-beam four-column structure, a main cylinder 11, an independent auxiliary mechanism, an upper ejector 12, a lower ejector 13, a filling mechanism 14, and a safety support mechanism (auxiliary cylinder 21). All auxiliary mechanisms can cooperate and work together to meet the needs of multi-function, multi-scenario and multi-application.

[0053] The main oil cylinder 11 is connected to the filling mechanism 14 and the hydraulic system 4 through hydraulic pipelines to achieve rapid delivery and pressure control of hydraulic oil. The auxiliary oil cylinder 21 is installed on the support seat 2 and is connected to the hydraulic system 4 through hydraulic pipelines to drive the upper mold connecting seat 22 to move downward quickly. The upper ejector device 12 and the lower ejector device 13 are respectively connected to the hydraulic system 4 through their own hydraulic pipelines to achieve ejection action. Pressure sensors and displacement sensors are installed in key positions, such as near the main oil cylinder 11 and the slider, and the monitored pressure and position signals are fed back to the controller 3. The independent operating console is connected to the controller 3 through an electrical connection for the operator to input instructions and monitor the system status.

[0054] In actual use, the operation of the forging press 1 includes the following stages:

[0055] Startup phase: The operator triggers the start signal on the independent operation console, and the electrical signal is transmitted to the controller 3 through the electrical connection. The controller 3 interprets the start command and transmits the instruction to the hydraulic system 4 through the signal receiving module. The hydraulic system 4 activates the filling mechanism 14, the hydraulic pump starts to supply oil to the liquid storage chamber, and the pressure sensor monitors the pressure change to ensure that the system pressure is stable within the preset range.

[0056] Slider mold closing stage: The auxiliary oil cylinder 21 starts to work, and the hydraulic oil enters the rod cavity of the auxiliary oil cylinder 21, driving the upper mold connecting seat 22 to move downward quickly. When the slider approaches 10 mm before the speed change point, the position information detected by the displacement sensor is sent to the controller 3, and the system adjusts the proportional valve and servo valve in the hydraulic system 4 to reduce the flow of hydraulic oil and slow down the slider. After the slider reaches the speed change point, the controller 3 switches to the fixed value output mode, and the slider enters the slow working state until it is fed to the material surface.

[0057] Material forming stage: After contacting the surface of the red forging workpiece, the controller 3 performs linear segmented control on the hydraulic system 4 through the servo system and proportional valve, gradually reducing the output pressure and flow. The pressure sensor performs real-time pressure detection with a sampling period of 100 milliseconds. When the pressure change reaches the preset end value, the controller 3 stops the boost signal to ensure the uniformity of the material plastic pressure during the forming process.

[0058] Pressure holding and pressure relief stage: When the pressure reaches the preset value, the controller 3 keeps the slider stationary through the proportional valve and servo valve in the hydraulic system 4 and starts the pressure holding procedure. After the pressure holding is completed, the controller 3 activates the superimposed pressure relief valve to steadily release the liquid pressure in the liquid storage chamber.

[0059] Slider return stage: After the pressure is eliminated, the controller 3 dynamically controls the mold opening process of the slider through the displacement sensor and servo system. The slider initially moves upward smoothly at an increasing speed. When the slider approaches the return stop point of 10 mm, the controller 3 automatically outputs a decreasing signal, and the slider speed gradually slows down and finally stops at the set stop point.

[0060] Auxiliary mechanism action: According to the process requirements, the controller 3 controls the auxiliary cylinder to work in single action or linkage mode, such as primary ejection, secondary ejection, stretching ejection, etc. Each auxiliary cylinder is connected to the hydraulic system 4 through a hydraulic pipeline to achieve mutually coordinated sequential actions.

[0061] The above contents are only preferred embodiments of the present invention. For ordinary technicians in this field, according to the concept of the present invention, there will be changes in the specific implementation methods and application scopes. The content of this specification should not be understood as limiting the present invention.

Claims

1. A flexible control method for a forging press, characterized in that: The following steps are involved: S1, using a control panel (5) of a forging press (1) to send a start signal to a controller (3), and after receiving the start signal, the controller (3) controls a filling mechanism (14) of a hydraulic system (4) to fill a liquid storage chamber with liquid, so that a system pressure is generated in the liquid storage chamber of the forging press (1); S2, using the hydraulic system (4) to drive the slider to close the mold, before the slider reaches the speed change point, the controller (3) outputs a signal to the hydraulic system (4) to change the pressure and flow rate of the liquid in the liquid storage chamber, after the slider reaches the speed change point, the controller (3) outputs a fixed pressure and flow rate signal to the hydraulic system (4), and the hydraulic system (4) drives the slider to change the working state until the slider is worked to the surface of the material; S3, when the slider moves to the surface of the material and starts to increase the pressure, the controller (3) controls the hydraulic system (4) to output the pressure and flow signals of the liquid in the liquid storage chamber in sections and gradually decreases until the pressure reaches a preset value.

2. The flexible control method of a forging press according to claim 1, characterized in that: The flexible control method of the forging press also includes the following steps: S4, after the pressure reaches the preset value, the controller (3) controls the slider to remain stationary via the hydraulic system (4) to maintain the pressure, and after the pressure maintenance is completed, the controller (3) controls the pressure relief valve to open to release the liquid in the liquid storage chamber; S5, after the liquid discharge pressure in the liquid storage chamber is eliminated, the controller (3) controls the hydraulic system (4) to drive the slide block to open the mold until the return stroke stops.

3. The flexible control method of a forging press according to claim 1, characterized in that: In the step S2, the flow signal output by the controller (3) to change the pressure and flow in the liquid storage chamber of the forging press (1) has a frequency of change of once every 90-120 ms.

4. The flexible control method of a forging press according to claim 1, characterized in that: In step S2, the speed change point of the slider is a fast-to-slow speed change point. The controller (3) controls the hydraulic system (4) to drive the slider to quickly close the mold until the slider reaches a distance of X millimeters from the fast-to-slow speed change point. The controller (3) starts to transmit a flow signal to the hydraulic system (4) to reduce the mold closing speed of the slider, so that the slider enters a slow working state.

5. The flexible control method of a forging press according to claim 4, characterized in that: The value range of X is 5mm-45mm.

6. The flexible control method of a forging press according to claim 2, characterized in that: During the mold opening process of the slider in step S5, a return stop point is pre-set by using the controller (3). When the pressure in the liquid storage chamber is eliminated, the controller (3) controls the hydraulic system (4) to drive the slider to open the mold smoothly at an increasing speed. When the slider is Y millimeters away from the return stop point, the speed begins to decrease until the slider is in a stationary state without rebound.

7. The flexible control method of a forging press according to claim 1, characterized in that: The pressure value range of the fixed-value pressure signal output by the controller (3) is 5MPa-20MPa, and the flow value range of the fixed-value flow signal output by the controller (3) is 10L / min-50L / min.

8. The flexible control method of a forging press according to claim 1, characterized in that: The increasing speed range of the slider during the mold opening process is 0.1m / s-1m / s, and the return speed range is 0.5m / s-2m / s.

9. The flexible control method of a forging press according to claim 1, characterized in that: In step S2, before the slider reaches the speed change point, the pressure sensor samples the pressure change of the liquid in the liquid storage chamber in a cycle of Z milliseconds. Then, the controller (3) calculates the deceleration ratio of the slider according to the pressure change value in the cycle and uses the deceleration ratio to control the hydraulic system (4) to drive the slider to decelerate. When the pressure change stops, the slider moves to the surface of the material.

10. The flexible control method of a forging press according to claim 2, characterized in that: When the slider performs a return motion in step S5, the slider first performs a rapid return motion, and a position signal of the slider is monitored in real time by a displacement sensor and transmitted to a controller (3). When the slider is displaced to a certain distance from a fast-slow speed change point, the controller (3) decelerates the rapid motion of the slider until the return motion stops.

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