Automatic edge pressing device for stainless steel plate and method thereof

Abstract

The invention relates to the field of metal plastic forming and automatic machining equipment, in particular to an edge pressing device and method for an automatic stainless steel plate. The device comprises a C-shaped rack, a servo driving mechanism, a main actuating hydraulic cylinder, a flexible magnetorheological blank pressing head and a compensation hydraulic cylinder, according to the device, a high-molecular flexible film and internal magnetorheological fluid are combined to construct an edge pressing execution end, and a static pressure fluid loop is constructed between a head hydraulic cylinder and a tail hydraulic cylinder of a rack; the method is characterized in that blank holder force is provided by following the rules of power-off flexible deformation fitting and power-on rigid locking forming, and blank holder reaction force is utilized to drive a compensation hydraulic cylinder to generate reverse extension thrust; a traditional rigid pressing head is abandoned, the problems of local stress concentration and surface damage caused by rigid contact are solved through magnetorheological fluid phase change, meanwhile, the opening deformation torque of the rack is automatically counteracted through a static pressure fluid loop, and the precision and stability of the edge pressing axis are effectively guaranteed.

Description

Technical Field

[0001] This invention relates to the field of metal plastic forming and automated processing equipment, specifically to an automated edge pressing device and method for stainless steel plates. Background Technology

[0002] In the processing of stainless steel sheet forming, edge pressing is a key process to ensure product forming quality and dimensional accuracy. Due to limitations in upstream manufacturing processes, the stainless steel sheets to be processed generally have thickness tolerances, and the yield strength and work hardening characteristics of different batches of materials fluctuate. Their edges often have complex high curvature profiles. To perform edge pressing on stainless steel sheets, existing solutions generally use rigid indenters or simple flexible indenters for mechanical pressing, and rely on open-loop fixed stroke control to complete plastic forming. Although this solution has certain processing capabilities in standard flat plates or low-precision scenarios, the rigid indenter cannot adapt to high curvature edges and thickness tolerance positions, which easily causes local stress concentration and surface damage. The simple flexible indenter lacks stiffness adjustment capability and is difficult to provide sufficient plastic forming force. In addition, high pressure edge load often causes the equipment frame to open and deform, causing the edge pressing axis to shift. Moreover, the traditional solidification mechanical action and control architecture is difficult to perceive the strain energy accumulation and rheological state inside the material in real time, resulting in a large amount of springback at the end of the edge pressing and poor process repeatability, making it difficult to support the high consistency and precision forming of complex profile plates.

[0003] Therefore, how to balance the conformal fit of the contact interface and the transmission of high-rigidity forming force during the edge pressing process, and how to identify the risk of high material springback in real time for dynamic adaptive compensation, has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides an automated pressing device and method for stainless steel plates. Specifically, the technical solution of the present invention is as follows: An automated edge-pressing device for stainless steel sheets includes: A C-shaped frame, wherein a lower mold base for supporting the stainless steel plate to be processed is fixed at the bottom of the C-shaped frame; A servo motor is fixed to the top of the C-shaped frame, and its output shaft is coaxially connected to a ball screw. The ball screw extends into the inner cavity of the C-shaped frame and is connected to a sliding seat. A main actuation hydraulic cylinder is fixedly connected to the bottom of the sliding seat. A main actuation hydraulic chamber is formed inside the main actuation hydraulic cylinder. A pressure head housing is fixedly connected to the end of the piston rod. A polymer flexible membrane is sealed and fixed at the bottom opening of the pressure head housing, forming a sealed magnetorheological fluid closed chamber. The magnetorheological fluid closed chamber is filled with magnetorheological fluid, and an excitation coil is fixedly arranged in a matrix array on its inner wall. The compensating hydraulic cylinder is vertically fixed to the pressure-bearing side of the back of the C-shaped frame. Its upper and lower ends are respectively hinged to the rear top and rear bottom sides of the C-shaped frame. The rodless chamber of the compensating hydraulic cylinder is directly connected to the main actuation hydraulic chamber through a high-pressure oil pipe, forming a closed hydrostatic fluid circuit.

[0005] In one embodiment, a linear guide rail is provided on the inner wall of the C-shaped frame, and the sliding seat forms a sliding guide engagement with the linear guide rail.

[0006] In one embodiment, the ball screw is coaxially connected to the output shaft of the servo motor via a flexible coupling.

[0007] In one embodiment, the pressing head housing is a hollow bell-shaped structure, and the edge of the polymer flexible film is sealed and fixed to the bottom end face of the pressing head housing by a flange plate.

[0008] An automated method for pressing stainless steel sheets includes: S1. Control the servo motor to drive the ball screw to rotate, causing the sliding seat to move downwards, keeping the excitation coil in a de-energized state, so that the polymer flexible film contacts the edge of the stainless steel plate and undergoes free deformation to achieve conformal bonding. S2. A preset initial current is passed through the excitation coil to cause the magnetorheological fluid to undergo a chaining effect and become rigidly locked, and the servo motor is controlled to continue to output macroscopic downward pressure to force the stainless steel plate to undergo plastic deformation. S3. Real-time acquisition of the high-frequency torque fluctuation signal of the servo motor, and acquisition of the transient pressure pulse signal inside the main actuation hydraulic chamber; S4. Integrate the high-frequency torque fluctuation signal in the time dimension to obtain the input work fluctuation amount, and extract the peak value of the transient pressure pulse signal to obtain the transient deformation resistance. S5. Calculate the phase difference between the input work fluctuation and the transient deformation resistance on the time axis, and determine whether the phase difference deviates from the preset standard safety range; when the phase difference deviates from the preset standard safety range, determine that the stainless steel plate has entered the high rebound risk zone, dynamically adjust the duty cycle of the pulse width modulation signal input to the excitation coil, and simultaneously control the servo motor to increase the over-bending compensation stroke; when the phase difference does not deviate from the preset standard safety range, maintain the current state of the excitation coil and continue to execute according to the original downward stroke.

[0009] In one embodiment, in step S2, the stainless steel plate generates a reaction force on the pressure head housing and presses the piston rod of the main actuation hydraulic cylinder upward, causing the high-pressure fluid in the main actuation hydraulic chamber to be pumped into the rodless chamber of the compensation hydraulic cylinder through the high-pressure oil pipe, so that the compensation hydraulic cylinder generates an extension thrust and applies a reverse head-down torque to the C-shaped frame to counteract the opening deformation torque.

[0010] In one embodiment, in step S5, when the high-frequency torque fluctuation signal continues to rise and the transient pressure pulse signal exhibits high-frequency jitter, causing the phase difference to deviate from the preset standard safety range, it is determined that the stainless steel material has locally entered the work hardening stage and accumulated elastic deformation energy, and the system enters the high rebound risk zone.

[0011] In one embodiment, in step S5, when it is determined that the high rebound risk zone has been entered and the downward stroke has reached five percent, the electromagnetic field strength of the excitation coil is reduced proportionally, so that the shear yield stress of the magnetorheological fluid decreases and exhibits a micro-yield state.

[0012] In one embodiment, in step S5, the stainless steel plate is forced to undergo microscopic plastic flow and release internal residual stress by the physical yielding of the polymer flexible membrane in the micro-yield state in conjunction with the over-bending compensation stroke movement of the servo motor.

[0013] In one embodiment, step S5 is followed by: S601. Control the servo motor to reverse and drive the sliding seat to rise; S602. Control the excitation coil to de-energize, so that the magnetorheological fluid returns to a highly fluid state, and the polymer flexible film smoothly separates from the surface of the stainless steel plate.

[0014] Compared with the prior art, the present invention has at least the following advantages: 1. This invention utilizes a flexible membrane in conjunction with a magnetorheological fluid. When the excitation coil is de-energized, the membrane undergoes free deformation to contact the edge of a stainless steel plate, achieving conformal bonding. When energized, the magnetorheological fluid undergoes a chaining effect and becomes rigidly locked. The servo motor continues to output macroscopic downward pressure, forcing the stainless steel plate to undergo plastic deformation. The main actuation hydraulic chamber and the rodless chamber of the compensation hydraulic cylinder are connected by a high-pressure oil pipe to form a closed hydrostatic fluid circuit. The pressure reaction force pushes the piston rod upward, pumping the high-pressure fluid into the compensation hydraulic cylinder, generating an extension thrust that applies a reverse head-down torque to the frame to counteract the opening deformation torque. 2. This invention acquires high-frequency fluctuation signals of servo motor torque and transient pressure pulse signals in real time. After integration and peak extraction, it calculates the phase difference between the total input power and transient deformation resistance on the time axis to determine whether it deviates from the preset standard safety range and whether it has entered the high rebound risk zone. When it is determined to enter the high risk zone and the downward stroke reaches five percent, the electromagnetic field strength is reduced proportionally to make the magnetorheological fluid enter the micro-yield state. The flexible membrane physical yielding and the servo motor over-bending compensation stroke movement are combined to force the stainless steel plate to undergo micro-plastic flow to release the internal residual stress. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the device; Figure 2 This is a schematic diagram of the main actuation hydraulic chamber structure of the device; Figure 3 This is a schematic diagram of the closed cavity structure of the magnetorheological fluid in the device; Figure 4 This is a flowchart of the method of the present invention.

[0016] In the diagram: 1. C-type frame; 2. Lower mold base; 3. Stainless steel plate; 4. Servo motor; 5. Output shaft; 6. Ball screw; 7. Sliding seat; 8. Main actuation hydraulic cylinder; 9. Main actuation hydraulic chamber; 10. Piston rod; 11. Pressing head housing; 12. High-polymer flexible membrane; 13. Magnetorheological fluid sealed chamber; 14. Magnetorheological fluid; 15. Excitation coil; 16. Compensating hydraulic cylinder; 17. Rodless chamber; 18. High-pressure oil pipe; 19. Linear guide rail; 20. Flexible coupling; 21. Flange pressure plate. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0018] Example 1 An automated edge-pressing device for stainless steel sheets, such as Figures 1 to 3 As shown, it includes: C-type frame 1, with a lower mold base 2 fixed at the bottom of the C-type frame 1 for supporting the stainless steel plate 3 to be processed; Servo motor 4 is fixed to the top of C-type frame 1. Its output shaft 5 is coaxially connected to ball screw 6. Ball screw 6 extends into the inner cavity of C-type frame 1 and is connected to sliding seat 7. The main actuation hydraulic cylinder 8 is fixed to the bottom of the sliding seat 7. The main actuation hydraulic chamber 9 is formed inside the main actuation hydraulic cylinder 8. The piston rod 10 is fixed to the end of the pressing head housing 11. The bottom opening of the pressing head housing 11 is sealed and fixed with a polymer flexible membrane 12, forming a closed magnetorheological fluid sealed cavity 13. The magnetorheological fluid sealed cavity 13 is filled with magnetorheological fluid 14, and its inner wall is fixed with excitation coils 15 in a matrix array. The compensating hydraulic cylinder 16 is vertically fixed to the pressure-bearing side of the back of the C-shaped frame 1. Its upper and lower ends are respectively hinged to the rear top and rear bottom sides of the C-shaped frame 1. The rodless chamber 17 of the compensating hydraulic cylinder 16 is directly connected to the main actuation hydraulic chamber 9 through the high-pressure oil pipe 18, forming a closed static pressure fluid circuit. In existing stainless steel plate pressing equipment, rigid pressing heads are prone to local stress concentration at high curvature edges and thickness tolerance positions, while simple flexible pressing heads are difficult to provide sufficient plastic forming force. To address this problem, this embodiment sets a C-shaped frame 1 as the load-bearing component of the whole machine. The C-shaped frame 1 can be integrally machined from QT600 ductile iron or ZG310-570 cast steel, with a throat depth of 350mm to 800mm and a column thickness of 80mm to 180mm. The lower mold base 2 is fixed to the bottom working end of the C-shaped frame 1. The working surface of the lower mold base 2 is machined into a support profile corresponding to the edge curvature of the stainless steel plate 3. The surface roughness of the profile can be controlled between Ra0.8μm and Ra1.6μm to reduce the slippage of the plate. The servo motor 4 is fixed on the top of the C-type frame 1. The rated power can be 5kW to 22kW and the rated torque can be 31N·m to 140N·m. It works with the ball screw 6 to convert the rotational motion into linear displacement in the pressing direction. The lead of the ball screw 6 can be 10mm to 25mm and the rated dynamic load can be selected from 80kN to 300kN according to the pressing force requirements. The sliding seat 7 is connected to the ball screw 6 nut pair and serves as the mounting base for the main actuation hydraulic cylinder 8, so that the mechanical, electrical and hydraulic parts transmit force along the same pressure axis; the main actuation hydraulic cylinder 8 is preferably a single piston rod 10 hydraulic cylinder, with a cylinder diameter of 80mm to 160mm and a working pressure of 10MPa to 31.5MPa, forming a main actuation hydraulic chamber 9 inside; The lower end of the piston rod 10 is fixed with the pressure head housing 11. The pressure head housing 11 and the polymer flexible membrane 12 together form a closed cavity of the sealed magnetorheological fluid 14. The volume of the closed cavity can be 0.2L to 2L. The magnetorheological fluid 14 can be a commercial magnetorheological fluid 14 with a carbonyl iron powder volume fraction of 20% to 45%. The excitation coils 15 are arranged in a matrix array on the inner wall of the closed cavity. Specifically, they can be installed in an embedded manner. The center distance of the coils is set to 15mm to 30mm, and they are covered with a non-magnetic stainless steel liner with a thickness of 1.0mm to provide physical protection. This is used to establish an adjustable electromagnetic field, so that the magnetorheological fluid 14 can maintain its flow dynamics at low field strength to achieve adhesion, and increase the shear yield stress at higher field strength to bear the edge load.

[0019] To address the opening deformation of the C-shaped frame 1 caused by the pressure reaction force, a compensating hydraulic cylinder 16 is installed on the pressure side of the back of the frame. Its rodless chamber 17 is directly connected to the main actuation hydraulic chamber 9 via a high-pressure oil pipe 18, forming a hydrostatic fluid circuit that can synchronously increase pressure with load changes without the need for external detection elements. The key technical point of this structure is that the pressure head part takes into account both contour fitting and forming force transmission through the combined effect of the polymer flexible membrane 12 and the magnetorheological fluid 14, while the frame compensation part suppresses the offset of the pressure axis through the volume coupling between the main actuation hydraulic chamber 9 and the compensating hydraulic cylinder 16. During actual assembly, the closed static pressure fluid circuit can be pre-filled with No. 32 or No. 46 anti-wear hydraulic oil. The pre-fill pressure can be set from 1MPa to 3MPa to eliminate pipeline backlash and improve compensation response speed. When the pressing operation is carried out by this device, contour fitting, forming stiffening and reverse pull compensation of the frame can be achieved simultaneously without adding an independent frame compensation drive unit. Linear guide rail 19 is provided on the inner wall of C-type frame 1, and sliding seat 7 and linear guide rail 19 form a sliding guide fit; in order to solve the problem that sliding seat 7 may wobble, twist and move laterally under high pressure side load, linear guide rail 19 is provided on the inner wall of C-type frame 1 as a guide pair. Linear guide 19 refers to a mechanical guide element that provides constraint along the direction of the pressing edge movement and allows the sliding seat 7 to perform linear motion with a single degree of freedom. Two parallel roller type heavy-duty linear guides 19 can be used. The guide width can be 35mm to 65mm and the rated static load can be 90kN to 250kN. Four or six sliders are fixed to the back of the sliding seat 7, which cooperate with the linear guide rails 19 on both sides to restrict the three degrees of freedom of pitch, yaw and roll. The parallelism between the guide rail mounting base and the axis of the ball screw 6 can be controlled within 0.03mm per 300mm. The preload level of the sliding seat 7 and the guide rail can be selected as medium preload or heavy preload to reduce the reversing backlash. This guiding method is consistent with the driving direction of the ball screw 6, so that when the pressure head housing 11 is pressed down, it will not cause lateral load due to the reaction force of the main actuation hydraulic cylinder 8.

[0020] For pressing devices with a large processing length, the arrangement of guide rail in front and ball screw 6 behind can also be adopted, or the arrangement of guide rail symmetrically distributed on both sides and ball screw 6 located in the middle can be adopted, but all of them should meet the requirement that the sliding seat 7 moves smoothly along the set pressing axis. The effect of this technical feature is that, through clear sliding guide constraints, the main actuation hydraulic cylinder 8 and the pressing head housing 11 can maintain a stable posture, reduce uneven contact of the polymer flexible film 12 and force bias of the magnetorheological fluid 14, and improve the consistency of the pressing line. The ball screw 6 and the output shaft 5 of the servo motor 4 are coaxially connected via a flexible coupling 20. To reduce the additional load caused by the installation error between the motor output shaft 5 and the ball screw 6, and to reduce the distortion caused by high-frequency torque fluctuations in the mechanical transmission chain, the ball screw 6 and the output shaft 5 of the servo motor 4 are coaxially connected through a flexible coupling 20. The flexible coupling 20 refers to a torque transmission element with certain radial, angular and axial compensation capabilities, and can be a plum blossom-shaped flexible coupling 20, a diaphragm coupling or a bellows coupling. Preferably, a plum blossom-shaped flexible coupling 20 is used, whose rated torque can be 1.5 to 2.5 times the rated torque of the motor, the allowable radial compensation can be 0.1 mm to 0.3 mm, and the allowable angular compensation can be 0.5° to 1.5°. This connection method ensures that the angular displacement and torque output by the servo motor 4 can be directly transmitted to the ball screw 6. On the other hand, it absorbs the shaft misalignment caused by the slight deformation of the C-type frame 1 under load, and avoids the upper bearing of the ball screw 6 bearing excessive bending moment.

[0021] Since the method requires real-time acquisition of the high-frequency torque fluctuation signal of the servo motor 4, the use of the flexible coupling 20 is also beneficial to suppress the meshing cycle disturbance caused by the gear reduction mechanism, so that the torque signal is closer to the material deformation resistance change itself; during assembly, the coaxiality of the two half shafts of the coupling with the motor shaft and the lead screw shaft can be controlled within 0.05mm, and the pre-tightening screw adopts an anti-loosening structure to ensure the stability of torque transmission during long-term operation. The pressure head housing 11 has a hollow bell-shaped structure, and the edge of the polymer flexible film 12 is sealed and fixed to the bottom end face of the pressure head housing 11 by the flange pressure plate 21. The pressure head housing 11 adopts a hollow bell-shaped structure, which means that the upper part of the housing forms an installation area connected to the piston rod 10 of the main actuation hydraulic cylinder 8, and the lower part forms an annular opening, providing space for the magnetorheological fluid 14 to be contained. The structure can be made of 304 stainless steel, 40Cr tempered steel or aluminum alloy with wear-resistant inner lining, and the wall thickness can be 4mm to 12mm; the bell-shaped structure gives the upper part of the cavity sufficient rigidity, and the lower opening can cover the edge of the stainless steel plate 3 to be pressed area. The edge of the polymer flexible membrane 12 is sealed and fixed to the bottom end face of the pressure head housing 11 by the flange pressure plate 21. The flange pressure plate 21 can be an annular pressure plate with a thickness of 5mm to 15mm. M5 to M8 fastening screws are distributed circumferentially with a screw spacing of 20mm to 40mm. The polymer flexible membrane 12 can be made of polyurethane elastomer, fluororubber or thermoplastic polyurethane film, with a thickness of 1mm to 4mm and a Shore A hardness of 70 to 95, to take into account wear resistance, oil resistance and elastic deformation ability; sealing and fixing refers to the leak-proof connection between the edge of the flexible membrane and the end face of the shell through the flange pressure plate 21, sealing gasket and fasteners. If necessary, oil-resistant sealant can be added to the contact surface. The technical advantage of the bell-shaped hollow structure combined with the flange pressure plate 21 fixing method is that the volume of the magnetorheological fluid 14 closed cavity is stable, the excitation coil 15 is clearly distributed in space, and the flexible membrane forms a controllable downward bulging deformation surface when it is pressed, which can make the contact pressure cover the pressing edge area instead of being concentrated on a certain rigid point. For plate edges of different widths, flange pressure plates 21 and flexible membrane components of different diameters can also be replaced to adapt to pressing edge widths of 20mm to 120mm.

[0022] Example 2 An automated edge pressing method for stainless steel sheets, such as Figure 4 As shown, it includes: S1. Control the servo motor 4 to drive the ball screw 6 to rotate, which in turn drives the sliding seat 7 to move downwards, keeping the excitation coil 15 in a de-energized state, so that the polymer flexible film 12 contacts the edge of the stainless steel plate 3 to undergo free deformation and achieve conformal bonding. S2. A preset initial current is passed into the excitation coil 15 to cause the magnetorheological fluid 14 to undergo a chaining effect and be rigidly locked. The servo motor 4 is controlled to continue to output macroscopic downward pressure to force the stainless steel plate 3 to undergo plastic deformation. S3. Real-time acquisition of the high-frequency torque fluctuation signal of the servo motor 4, and acquisition of the transient pressure pulse signal inside the main actuation hydraulic chamber 9; S4. Integrate the high-frequency torque fluctuation signal in the time dimension to obtain the input work fluctuation, and extract the peak value of the transient pressure pulse signal to obtain the transient deformation resistance. S5. Calculate the phase difference between the input work fluctuation and the transient deformation resistance on the time axis, and determine whether the phase difference deviates from the preset standard safety range. When the phase difference deviates from the preset standard safety range, it is determined that the stainless steel plate 3 has entered the high rebound risk zone. The duty cycle of the pulse width modulation signal of the input excitation coil 15 is dynamically adjusted, and the servo motor 4 is controlled to increase the over-bending compensation stroke. When the phase difference does not deviate from the preset standard safety range, the current state of the excitation coil 15 is maintained and the original downward stroke is continued.

[0023] The edge pressing method is used in the aforementioned device, and the edge pressing of the stainless steel plate 3 is completed through the coordinated mechanical action and control calculation; the conformal bonding refers to the formation of a contact interface that matches the curvature and thickness profile of the polymer flexible film 12 when the magnetorheological fluid 14 is in a flow state, as the shape of the plate edge changes; the rigid locking refers to the magnetic particles inside the magnetorheological fluid 14 aligning along the magnetic lines of force and establishing an anti-shear network after the excitation coil 15 forms an electromagnetic field, thereby increasing the equivalent shear yield stress of the medium in the closed cavity. In this method, the input work fluctuation refers to the cumulative fluctuating work calculated based on the relationship between the high-frequency torque fluctuation component output by the servo motor 4 and the angular displacement over time. The transient deformation resistance refers to the material's resistance to plastic deformation per unit time, obtained by mapping the peak pressure pulse of the main actuation hydraulic chamber 9. The phase difference refers to the offset between the total input work change sequence and the transient deformation resistance change sequence on the same time base. In practice, the stainless steel plate 3 is fixed to the lower mold base 2. The plate thickness can be 0.5mm to 6mm, and the material can be 304, 316L, or 430 stainless steel. In S1, the controller sends a downward pressure command to the servo motor 4, and the sliding seat 7 moves downward at an approach speed of 20mm / s to 200mm / s; the excitation coil 15 remains de-energized, the viscosity of the magnetorheological fluid 14 is at its basic state, and after the flexible membrane contacts the edge of the plate, it generates elastic local protrusions and fluid redistribution within the range of 0.1mm to 2mm to eliminate the local gaps caused by the thickness error of the plate edge; the completion of the conformal bonding can be determined by the position threshold, the contact force threshold, or the servo torque mutation threshold, where the contact force threshold can be set to 50N to 300N; In S2, the controller supplies a preset initial current to the excitation coil 15. The current of a single coil can be 0.5A to 3A, and the current establishment time can be less than 20ms. The shear yield stress of the magnetorheological fluid 14 can be increased from several kPa to 20kPa to 80kPa. The servo motor 4 switches the pressing speed to the forming speed. The forming speed can be 1mm / s to 20mm / s, so that the blank holder force is gradually increased to the process setting value. The blank holder force can be 10kN to 150kN. The stainless steel plate 3 undergoes plastic bending or blank holder forming under the support of the lower mold base 2. In S3, the high-frequency torque fluctuation signal can be obtained by the torque estimation module inside the servo driver, and the sampling frequency can be from 1kHz to 20kHz; the transient pressure pulse signal can be obtained by the pressure sensor set on the main actuation hydraulic chamber 9, with a range of 0MPa to 40MPa, and the sampling frequency is synchronized with the torque signal or an integer multiple thereof; in the feature extraction of S4, in order to eliminate the background noise of the mechanical transmission chain, the high-frequency torque fluctuation signal is pre-filtered with a high-pass filter with a cutoff frequency of 150Hz to extract the fluctuation component, and the pressure pulse signal is filtered with a band-pass filter to retain the effective characteristic frequency band from 10Hz to 500Hz; In S4, the controller multiplies the extracted high-frequency torque fluctuation component by the motor angular velocity to obtain the instantaneous fluctuation power, and then accumulates it according to the sampling period to obtain the input work fluctuation sequence; specifically, the discrete calculation model of this input work fluctuation sequence is determined by the following formula: In the formula, As of the date The cumulative value of the input work fluctuation at each sampling point For the first The high-frequency fluctuation component of torque at each sampling point For the first The motor angular velocity corresponding to each sampling point The discrete sampling period of the system, The current sampling point number is a positive integer. It is an accumulated variable, with values ​​ranging from 1 to... Positive integers; in addition, the system simultaneously performs bandpass filtering and peak extraction on the pressure signal, and the extracted peak value corresponds to the transient deformation resistance during the pressing process; In S5, the controller uses cross-correlation calculation, zero-crossing alignment, or characteristic peak alignment to determine the phase difference between the two sequences; the controller can use a discrete cross-correlation function to process the total input work sequence and the transient deformation resistance sequence; specifically, let the input work fluctuation sequence within the current observation window be... The transient deformation drag debasement sequence is The sequence length is Then the discrete cross-correlation function of the two It can be represented as: in, The number of time-off samples. This is the index of the sampling points for the discrete-time series, with a value of [value]. arrive The controller iterates through a reasonable offset range to find an integer; By obtaining the offset of the maximum value and multiplying it by the sampling period, the phase difference between the two sequences on the time axis can be obtained. The standard safety interval can be obtained in advance through sample calibration, for example, it can be set to -10ms to +10ms, or converted to a phase angle of less than 15°.

[0024] When the phase difference exceeds this range, it indicates that the input energy and the material's resistance to deformation have deviated. The controller will reduce the pulse width modulation duty cycle of the excitation coil 15 from the reference value by 5% to 30%, and at the same time instruct the servo motor 4 to increase the over-bending compensation stroke by 0.05mm to 1.5mm. When the phase difference is within the standard safe range, the original excitation state is maintained and the original stroke continues. The effect of this method is that by using the pressing execution method of first bonding and then increasing stiffness, and combining the synchronous calculation of torque and pressure signals, the medium stiffness and pressing displacement at the end of the pressing section can be dynamically corrected when the material properties fluctuate. In actual control, the following steps can be taken: Align the original torque sample value output by the servo driver with the motor angular velocity sample value recorded inside the controller using the same clock timestamp to obtain a set of one-to-one torque-speed sample pairs; The original pressure sample values ​​output by the pressure sensor are resampled or interpolated to the same time base as the torque sample to avoid phase calculation distortion caused by different sampling frequencies. The torque sequence is processed to remove DC components and retain high frequencies to extract the high-frequency fluctuation components of torque that characterize the material deformation resistance disturbance. The pressure sequence is processed to remove baselines and filter peaks to extract the pulse peak sequence related to the instantaneous yield of the material. The instantaneous power is calculated point-by-point based on torque-velocity sampling and accumulated to obtain the total input power time series. Then, the pressure pulse peak value is converted into a transient deformation resistance time series according to a preset calibration table or a preset proportional relationship. The conversion logic of the preset proportional relationship adopts the following linear mapping model: In the formula, For mapping after the first Transient deformation resistance within a sampling window; The extracted pressure pulse peak value within this window; since the baseline subtraction of the pressure sequence has been clearly performed in the previous step, there is no need to superimpose the system back pressure compensation constant here, and the pure instantaneous yield resistance increment of the material can be directly characterized. This is based on the effective area of ​​the main actuation hydraulic chamber 9 and the equivalent proportionality coefficient calibrated for the material being processed; The sampling window number is a positive integer. System back pressure compensation constant The method of obtaining the value is as follows: when the main actuation hydraulic cylinder 8 is under no-load pressure and the polymer flexible membrane 12 is not in contact with the stainless steel plate 3 to be processed, read the steady-state basic pressure value in the main actuation hydraulic chamber 9, and calculate the value by multiplying the steady-state basic pressure value by the effective force-bearing area of ​​the piston in the main actuation hydraulic chamber 9. Time alignment is performed on two time series within the same window length, and the phase difference result is output with the center time of the window as the current judgment time. The phase difference result is sent to the high rebound risk judgment module on one hand, and to the excitation coil 15 duty cycle adjustment module and the over-bending compensation stroke generation module on the other hand. The logical function of the preset initial current is to switch the magnetorheological fluid 14 from a free-fitting state to an initial stiffening state that can bear the blank holder force. The method for determining it is as follows: first, estimate the initial surface pressure required for the blank holder stage based on the target plate thickness, target blank holder force, and effective contact area of ​​the flexible film; then, according to the current-yield stress calibration curve of the magnetorheological fluid 14 sample, select the minimum coil current value that can make the shear yield stress reach the initial surface pressure requirement, and use this value as the preset initial current under the corresponding process formula.

[0025] The physical meaning of the standard safety range is the allowable normal response hysteresis range between the change in total input work and the change in transient deformation resistance. This range is used to distinguish between normal plastic forming conditions and potentially high springback conditions; its source can be: Multiple edge-pressing experiments were conducted on stainless steel samples of the same grade, thickness, and target curvature. The phase difference distribution in the samples whose springback after forming met the process requirements was recorded, and the allowable fluctuation range on both sides of the statistical center value was set as the standard safety range. For different material batches, this range can also be recalibrated according to the batch, or corrected based on the measured deviation of yield strength on the basis of the existing range. In one specific implementation, if the control window length is set to 20ms, the controller can update the local sequence of total input power and transient deformation resistance every 2ms, and output the phase difference of the current window each time it is updated; If the phase difference exceeds the standard safety range in two or more consecutive update cycles, the system enters enhanced monitoring mode and continues to make further judgments based on the torque increase trend and pressure jitter level within the subsequent window to avoid false triggering caused by a single abnormal pulse. Through the above step-by-step processing, the logical relationship between total input power, transient deformation resistance, phase difference, standard safety range and their triggering results can be made clearer, making it easier for those skilled in the art to implement accordingly. S3 to S5 can be summarized as a set of phase judgment models. The purpose of this model is not to obtain a certain force or displacement value, but to identify whether the input energy and the material yield response still maintain a stable matching relationship, so as to make an online judgment on the risk of high rebound when the internal elastic strain energy of the material cannot be directly measured in real time. The phase determination model can be logically divided into four parts: input layer, feature construction layer, alignment determination layer, and execution layer. The input layer receives torque sample values, angular velocity sample values, and pressure sample values. The feature construction layer forms a total input work time series based on the torque sample values ​​and angular velocity sample values, and forms a transient deformation resistance time series based on the pressure sample values. The alignment decision layer compares the order of peak occurrence, degree of overlap of rising segments, or extreme position of cross-correlation between two time series under a unified time reference, and outputs the phase difference and its deviation direction; the execution layer selects to maintain, reduce the field, or increase the cornering compensation stroke based on the deviation result. The model as a whole represents the correspondence between the input energy at the driving end during the pressing process, the change in the plastic resistance of the sheet, and the increase or decrease in the risk of springback: when the material is in a stable plastic flow state, the change in total input energy and the change in transient deformation resistance are relatively synchronized in time; when the material experiences local work hardening or flow instability, the temporal relationship between the two undergoes an identifiable shift, so this shift can be used as an indirect characterization of high springback risk. S4 performs integration on the high-frequency torque fluctuation signal in the time dimension to obtain the input work fluctuation amount. This means that the extracted high-frequency torque fluctuation component at the same sampling time is first paired with the corresponding angular velocity sampling value or angular displacement increment, and then an instantaneous fluctuation power sequence or fluctuation work micro-element sequence is formed. The sequence is then accumulated along the time axis to obtain the input work fluctuation amount that characterizes the transient deformation resistance disturbance of the material. The reason for this approach is that torque only represents the driving end torque level, while the total input work also depends on the motion process under the action of that torque; therefore, only after establishing a one-to-one correspondence between torque and angular velocity or angular displacement increment can there be a clear and direct physical correspondence between the total input work and the actual pressing edge input energy. In step S2, the stainless steel plate 3 generates a reaction force on the pressure head housing 11 and presses the piston rod 10 of the main actuation hydraulic cylinder 8 upward, causing the high pressure fluid in the main actuation hydraulic chamber 9 to be pumped into the rodless chamber 17 of the compensation hydraulic cylinder 16 through the high pressure oil pipe 18, so that the compensation hydraulic cylinder 16 generates an extension thrust and applies a reverse head-down torque to the C-type frame 1 to counteract the opening deformation torque. During the S2 plastic pressing stage, the stainless steel plate 3 generates a reaction force on the pressing head housing 11 that increases synchronously with the pressing force. This force is transmitted to the main actuation hydraulic cylinder 8 via the piston rod 10, causing the hydraulic oil pressure in the main actuation hydraulic chamber 9 to increase. Since the main actuation hydraulic chamber 9 and the rodless chamber 17 of the compensating hydraulic cylinder 16 are directly connected through the high-pressure oil pipe 18, the high-pressure fluid in the main actuation hydraulic chamber 9 will enter the rodless chamber 17 of the compensating hydraulic cylinder 16 under the action of pressure difference; the extension thrust here refers to the piston rod of the compensating hydraulic cylinder 16 extending relative to the cylinder after being pressed in the rodless chamber 17, and forming a supporting thrust between the hinge points at both ends. The pulling force acts on the pressure side of the back of the C-type frame 1, which can form a closing offset torque in the geometry of the frame that is opposite to the opening direction of the working end. In order to keep the compensation effect in line with the change of the pressure edge load, the effective area of ​​the main actuation hydraulic chamber 9, the effective area of ​​the rodless chamber 17 of the compensation hydraulic cylinder 16, the inner diameter of the oil pipe and the pre-charge pressure of the circuit can be set together. For example, the effective area of ​​the main actuation hydraulic cylinder 8 can be 8000mm², the effective area of ​​the rodless chamber 17 of the compensating hydraulic cylinder 16 can be 5000mm² to 12000mm², the inner diameter of the connecting oil pipe can be 6mm to 16mm, and the length can be 0.3m to 1.5m. By adjusting the area ratio of the two hydraulic chambers, the axial thrust generated by the compensating hydraulic cylinder 16 can be within the range of 5kN to 80kN, meeting the frame compensation requirements of equipment of different tonnages; when the pressure force increases and the front of the frame tends to open, the thrust of the back compensating hydraulic cylinder 16 increases synchronously, which can reduce the tilt of the axis of the ball screw 6. In the experiment, the relative opening between the upper and lower ends of the working port of the frame can be reduced from 0.20mm to less than 0.05mm. The function of this technical feature is that the compensation driving force comes directly from the pressing process itself, without relying on additional detection of frame deformation before independent control. Therefore, it has a shorter mechanical response path under high load change conditions.

[0026] In step S5, when the high-frequency torque fluctuation signal continues to rise and the transient pressure pulse signal exhibits high-frequency jitter, causing the phase difference to deviate from the preset standard safety range, it is determined that the stainless steel material has entered the work hardening stage and accumulated elastic deformation energy, and the system enters the high rebound risk zone. This step addresses the issues of work hardening and springback that easily occur in the plastic forming of stainless steel, and provides the criteria for determining the high springback risk zone. In this method, work hardening refers to the phenomenon that the stress required for the material to continue deforming increases with the increase of plastic strain. Elastic deformation energy refers to the energy that is temporarily stored in the material due to the elastic distortion of the crystal lattice and may be converted into springback displacement after unloading. In practice, the controller performs sliding window processing on the high-frequency torque fluctuation signal collected by S3, with a window length ranging from 5ms to 50ms, and calculates the mean slope and fluctuation amplitude within the window; it also extracts the peak-to-peak value, peak frequency, and pulse interval variation coefficient from the pressure pulse signal; the specific data flow and calculation rules are defined as follows: For the average torque slope, the controller calculates the average torque sample value for each window in multiple consecutive sliding windows, and obtains the slope of these average values ​​as a function of time by linear fitting using first-order forward difference or least squares method. For the pulse interval variation coefficient, the controller records the time interval between all adjacent pressure pulse peaks within the current window, calculates the ratio of the standard deviation to the mean of these time intervals, and uses this as a quantitative indicator to characterize the degree of jitter irregularity; the specific formula for calculating this pulse interval variation coefficient is as follows: In the formula, The pulse interval variation coefficient; This represents the total number of pulse intervals within the current calculation window; For the first The time interval between the peak values ​​of adjacent pressure pulses; This is the average value of all pulse intervals within this window.

[0027] When the average torque value continues to rise monotonically over multiple consecutive windows, and the rate of increase is higher than a predetermined threshold, such as 1% higher than the rated torque every 10ms, and at the same time the pressure pulse exhibits high-frequency jitter, such as the peak standard deviation increasing by more than 30% compared to the previous stable stage, or the number of pulse peaks increasing by more than 20% per unit time, it can be considered that the material is locally obstructed and the plastic flow is unstable. The controller further aligns the total input power curve within the current window with the transient deformation resistance curve in time. If the phase difference obtained continues to deviate from the preset safety range for more than the set duration, such as more than 20ms to 100ms, the system is determined to have entered the high rebound risk zone. This judgment method does not rely on a single force or displacement value, but uses the combined characteristics of torque change trend and pressure pulse disturbance to describe the state of strain energy accumulation inside the material. For different grades of stainless steel, a correspondence table between phase difference threshold and springback amount can be established through pre-experimentation, thereby correcting the judgment boundary of the high springback risk zone and adapting the control parameters to the differences in material batches. The term "continuous increase" does not refer to an instantaneous increase at a single sampling point, but rather to a situation where the average slope of the torque is positive within at least two consecutive sliding windows, preferably three sliding windows, and the average value of the subsequent window is not lower than the average value of the previous window minus the allowable noise band. The allowable noise band can be taken as 0.2% to 1% of the rated torque to eliminate false increases caused by sensor noise and minor mechanical disturbances. High-frequency jitter optimization does not simply refer to a higher pressure value, but rather to an increase in both the dispersion and density of pressure pulse peaks. In other words, within the same observation window, there is both an increase in the standard deviation of the peak value and an increase in the number of peaks per unit time, or a significant increase in the coefficient of variation of the pulse interval. The purpose of this definition is to distinguish between a single normal impact peak and a continuous unstable plastic flow state. The physical significance of the high springback risk zone is that although the material is still in the process of being compressed and formed at the end of the current pressing stage, the matching relationship between the input energy and the material yield response has deviated from the stable plastic flow state. The local area is more likely to release the accumulated elastic deformation energy after unloading and generate a large springback. Its decision-making role in control is as the triggering condition for subsequent field reduction control and over-bending compensation control. Specifically, the controller will only output a high rebound risk flag and perform micro-yield adjustment and motion matching compensation when the three conditions of continuous torque increase, high-frequency pressure fluctuation, and continuous phase difference deviating from the standard safe range meet the preset combination rules; if only one or two of these conditions are abnormal, the controller can maintain the original process parameters and continue to monitor in order to reduce the probability of misjudgment. In one example, 10 windows in the middle of the forming process where the material plastic flow is relatively stable can be selected as reference stable stages to obtain the baseline values ​​of the mean torque, the standard deviation of the peak pressure, and the pulse frequency. Then, in the real-time window at the end, the values ​​are compared with the baseline values. When the slope of the mean torque is continuously positive, the increase of the standard deviation of the peak pressure reaches a predetermined proportion, and the phase difference deviation continues to exceed the set time, it is determined that the high rebound risk zone has been entered. The logic structure for determining the high rebound risk zone may include a trend identification unit, a disturbance identification unit, a phase verification unit, and a result output unit: the trend identification unit receives the high-frequency torque fluctuation signal and outputs the trend result indicating whether it continues to rise; the disturbance identification unit receives the transient pressure pulse signal and outputs the disturbance result indicating whether there is high-frequency jitter. The phase verification unit receives the total input work sequence and the transient deformation resistance sequence and outputs the phase result indicating whether it continuously deviates from the standard safe range; the result output unit only issues a high rebound risk flag when the aforementioned three types of results meet the preset combination conditions. The physical relationship represented by this logic is as follows: the continuous increase in torque corresponds to the overall increase in the resistance that the drive end needs to overcome in order to maintain plastic forming; the high-frequency jitter of the pressure pulse corresponds to the intermittent and non-uniform plastic flow in the contact area; and the continuous deviation of the phase difference indicates that the input energy and the material yield response no longer maintain a stable following relationship. When all three occur together, it further indicates that there is a risk of localized work hardening, accumulation of elastic deformation energy, and amplified rebound after unloading in the material. Because the three types of signals are cross-verified, compared to judging solely based on the pressure peak value or solely based on the absolute value of torque, it can reduce false triggering caused by single impact, occasional friction, or instantaneous speed adjustment of the motor.

[0028] In step S5, when it is determined that the high rebound risk zone has been entered and the downward stroke has reached five percent, the electromagnetic field strength of the excitation coil 15 is reduced proportionally, so that the shear yield stress of the magnetorheological fluid 14 decreases and presents a micro-yield state. When the system has determined that it has entered the high rebound risk zone, if the magnetorheological fluid 14 is still kept in a fully rigid state, the local stress peak between the surface layer of the stainless steel plate 3 and the pressure head may continue to rise, and the unloading rebound will increase. Therefore, within the last five percent of the total set stroke of the pressing stroke, the controller implements proportional field reduction control on the excitation coil 15. The micro-yield state here refers to the state in which the magnetorheological fluid 14 still has a certain load-bearing capacity, but allows a small relative flow after the shear stress on the contact surface reaches a low threshold. During implementation, if the total downward stroke is 20mm, then the last 5% corresponds to a 1mm interval; the controller will reduce the pulse width modulation duty cycle of the excitation coil 15 from, for example, 80% to 60% to 75%, or reduce the coil current from 2A to 1.2A to 1.8A, so that the shear yield stress of the magnetorheological fluid 14 is reduced by 10% to 40%; To prevent insufficient clamping force due to excessively rapid descent, the duty cycle can be continuously adjusted according to a linear function, a piecewise linear function, or an exponential decay function with the remaining stroke. For example, when the remaining stroke is 1 mm, the duty cycle decreases by 2% to 4% for every 0.1 mm. After the shear yield stress of the magnetorheological fluid 14 decreases, a controlled small yield can occur between the polymer flexible membrane 12 and the edge of the plate. The yield can be 0.01 mm to 0.20 mm, thereby reducing the stress peak at the contact surface. This treatment does not eliminate the load-bearing function of the magnetorheological fluid 14, but rather retains the necessary blank holder force while introducing limited compliance during the stage when the risk of material springback increases. Through this feature, the load distribution at the end of the blank holder is changed from rigid concentrated contact to limited flow support, which helps to reduce the residual elastic energy before springback. The stage where the downward stroke reaches 5% can be determined by comparing the cumulative downward displacement recorded by the controller with the target total downward stroke in the current process formula. Before the start of S1, the controller writes the target total downward stroke into the current workpiece parameter table. During the execution of S2 and S5, it continuously reads the encoder position of the servo motor 4 or the converted displacement of the ball screw 6 to obtain the real-time cumulative downward displacement. When the remaining stroke is less than or equal to 5% of the target total downward stroke, it is determined that the stage of 5% has been entered. If the equipment uses the contact point as the zero position, the cumulative downward displacement can be calculated from the moment the conformal bonding is completed; if the equipment uses the top dead point as the zero position, the controller can first deduct the approach section idle stroke and then compare the effective forming stroke to avoid different clamping heights affecting the final judgment. The significance of proportional reduction in the control logic is to ensure that the decrease in electromagnetic field strength corresponds to the remaining stroke, phase difference deviation, or high rebound risk level, rather than reducing it to a low value all at once; its specific execution can be carried out in the following order: First, read the phase difference deviation of the current window and classify it into mild, moderate or severe risk levels; then, select the corresponding descent slope based on whether the current remaining journey is in the first half or the second half of the final stage. The pulse width modulation duty cycle or coil current is gradually reduced according to the selected slope; after each adjustment, the pressure pulse and torque fluctuation are read. If there are signs of insufficient clamping force or loss of adhesion, the field reduction is stopped or the position is reversed to the previous level. Through this sequential control, it can be ensured that the micro-yield state is gradually established while maintaining the clamping effect. The determination of the micro-yield state can be achieved by means related to process calibration. For example, in the experimental stage, the variation range of the stiffness of the magnetorheological fluid 14 supporting the flexible membrane under different duty cycles or different coil currents is measured first. Then, the electromagnetic field range that can keep the plate edge continuously compressed and allow the flexible membrane to have controlled yielding of 0.01 mm to 0.20 mm is selected as the micro-yield working area. During operation, when the controller adjusts the coil drive to the working area, it is considered that the magnetorheological fluid 14 has entered the micro-yield state, and the state signal is output to the subsequent bending compensation coordination module. By supplementing the above definition, the three key judgment and control nodes of five percent, proportional reduction, and micro-yield state can have clear determination methods and decision-making roles.

[0029] In step S5, the physical yielding of the polymer flexible membrane 12 in a micro-yield state is combined with the overbending compensation stroke movement of the servo motor 4 to force the stainless steel plate 3 to undergo micro-plastic flow and release the internal residual stress. This step specifies the specific control mechanism in the high rebound risk zone; the over-bending compensation stroke refers to the additional downward displacement added on the basis of the original target forming displacement, which is used to offset the rebound after unloading; physical yielding refers to the restricted deformation and media redistribution of the contact interface of the polymer flexible membrane 12 when the magnetorheological fluid 14 is in a micro-yield state. During implementation, after the controller descends, it sends an additional displacement command to the servo motor 4. The over-turning compensation stroke can be from 0.05mm to 1.5mm, preferably set in stages according to the phase difference deviation. For example, if the phase difference deviates from the safe range by 10%, it increases by 0.1mm; if it deviates by 30%, it increases by 0.4mm; and if it deviates by 50%, it increases by 0.8mm. To achieve continuous dynamic adjustment of the over-turning compensation stroke to adapt to different levels of work hardening risk, the over-turning compensation stroke... Deviation from phase difference The following calculation model applies: In the formula, To compensate for travel during cornering, This is the phase difference deviation. To find the maximum value function, The compensation gain coefficient is pre-calibrated for a specific batch of materials. The upper limit of the preset standard safety range is the critical value. Through this continuous adjustment model, the controller can smoothly convert any phase deviation exceeding the safety range into additional displacement commands for the servo motor 4, avoiding displacement step shocks caused by piecewise discrete control. Since the magnetorheological fluid 14 has transitioned from a fully rigid state to a slightly yielding state, the newly added displacement will not be entirely converted into peak compressive stress on the surface of the plate. Instead, a portion of the instantaneous peak value will be absorbed by the local yielding of the polymer flexible film 12, making the actual contact load distribution acting on the stainless steel plate 3 more gradual. This synergistic effect promotes a small amount of plastic elongation in the plate edge bending area under a lower stress gradient, i.e., microscopic plastic flow. Microscopic plastic flow can be verified by changes in residual curvature after forming, reduction in springback angle after unloading, or surface residual stress testing. For example, in a 1.5mm thick 304 stainless steel sample, the springback angle can be 1.8° when using simple overbending compensation. After using micro-yield yielding and overbending compensation in combination, the springback angle can be reduced to the range of 0.8° to 1.2°. This result shows that the controlled yielding of the flexible membrane not only avoids the local damage directly caused by the additional displacement, but also makes the additional displacement more effectively converted into the amount of plastic correction required to reduce springback.

[0030] The motion coordination is not a simple superposition of two actions, but has a clear sequential relationship and load distribution relationship: first, the magnetorheological fluid 14 is brought into a micro-yield state by the field reduction control to establish a contact interface with limited compliance; Then, the servo motor 4 outputs the over-bending compensation stroke, so that the new displacement is redistributed between the local yielding of the flexible membrane and the continued plastic deformation of the sheet. The purpose is to avoid applying additional displacement in a fully rigid contact state in the high springback risk zone. Otherwise, the additional displacement is more likely to be directly converted into a local surface stress peak, rather than into a stable and uniform plastic correction. The collaborative process can be logically divided into three consecutive stages: the first stage is the compliance establishment stage, at which time the electromagnetic field strength decreases, the equivalent support stiffness of the magnetorheological fluid 14 decreases, and the flexible membrane obtains controlled yielding ability. The second stage is the displacement redistribution stage, at which point the bending compensation stroke input by servo motor 4 is partially absorbed by the flexible membrane and partially transmitted to the bending area of ​​the plate edge. The third stage is the stress release stage, at which point supplementary plastic flow occurs locally at the edge of the plate under a relatively gentle contact pressure gradient, thereby reducing the residual stress retained in the form of elastic energy storage. This establishes a clear cause-and-effect relationship: because the contact interface changes from a completely rigid support to a finite compliant support, the additional downward displacement will not be concentrated in a single local area; and because the additional displacement is redistributed and transformed into a more uniform plastic extension, the elastic energy that can be released after unloading is reduced, and the rebound amount is correspondingly reduced. In this embodiment, microscopic plastic flow refers to the continuous generation of small, cumulative plastic strain increments in the material surface or bending transition zone without the occurrence of obvious indentation, tearing, or instability and wrinkling. Its determination does not require direct observation of the microstructure changes at the crystal level on the production site, but can be indirectly characterized by macroscopic measurable results, such as a reduction in the springback angle after compensation, an improvement in the consistency of the target curvature, a decrease in the residual stress test value, or a reduction in the final forming dispersion of the same batch of workpieces. In the micro-yield state, the flexible membrane provides controlled buffering, and the servo motor 4 provides additional forming displacement. The two work together to change the local stress state of the plate edge from elastic energy storage to a stress state of a small amount of supplementary plastic deformation, thereby reducing springback.

[0031] The steps following S5 include: S601, control the servo motor 4 to reverse and drive the sliding seat 7 to rise; S602, De-energize the excitation coil 15 to restore the magnetorheological fluid 14 to a high fluidity state, and smoothly separate the polymer flexible film 12 from the surface of the stainless steel plate 3. After completing the blanking and final compensation, the blanking head needs to be safely detached from the edge of the plate to avoid secondary friction or tangential tearing damage to the surface of the formed part due to the high rigidity of the magnetorheological fluid 14. To this end, S601 and S602 are executed after S5. In S601, the controller outputs a reverse rotation command to the servo motor 4, so that the ball screw 6 drives the sliding seat 7, the main actuation hydraulic cylinder 8 and the blanking head housing 11 to rise. The return speed can be set from 10 mm / s to 150 mm / s. In the initial return stroke when the blanking head just detaches from the edge of the plate, a lower speed can be used to reduce the risk of surface scratches. After a certain distance away from the workpiece, a higher speed can be switched to speed up the equipment reset response. In S602, the controller cuts off the power supply to the excitation coil 15, and the coil current drops to zero within 1ms to 50ms. The magnetorheological fluid 14 recovers its high fluidity due to the disappearance of the electromagnetic field, and the polymer flexible membrane 12 returns to the initial state with small bulge deformation under the action of its own weight, surface tension and fluid redistribution in the cavity. Smooth separation refers to the gradual decrease in contact pressure between the flexible membrane and the stainless steel plate 3 as the return displacement progresses, rather than direct peeling under high stiffness. To improve separation stability, a brief pressure holding or depressurization control can be set before and after power failure. For example, the pressure of the main actuation hydraulic chamber 9 can be gradually reduced within 0.1s to 0.5s at the beginning of the return stroke to avoid the reverse impact of the compensation hydraulic cylinder 16 caused by the sudden change in the closed static pressure fluid circuit.

[0032] After the demolding is completed, the collected torque, pressure, phase difference, duty cycle and compensation stroke data can be stored as the current workpiece record for the correction of process parameters of the same batch of plates. After adopting this demolding and resetting process, the contact load during the resetting process of the pressing head is significantly reduced, and the risk of wear on the flexible film surface and scratches on the surface of the formed part can be reduced. At the same time, the recovery of the flow dynamics of the magnetorheological fluid 14 also creates the initial conditions for the conformal bonding of the next cycle.

[0033] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. An automated edge-pressing device for stainless steel plates, characterized in that, include: C-type frame (1), the bottom of which is fixed with a lower mold base (2) for supporting the stainless steel plate (3) to be processed; A servo motor (4) is fixed to the top of the C-shaped frame (1), and its output shaft (5) is coaxially connected to a ball screw (6). The ball screw (6) extends into the inner cavity of the C-shaped frame (1) and is connected to a sliding seat (7). The main actuation hydraulic cylinder (8) is fixed to the bottom of the sliding seat (7). The main actuation hydraulic cylinder (8) has a main actuation hydraulic chamber (9) formed inside. The piston rod (10) is fixed to the end of the piston rod (10) with a pressing head housing (11). The bottom opening of the pressing head housing (11) is sealed and fixed with a polymer flexible membrane (12) and forms a closed magnetorheological fluid closed cavity (13). The magnetorheological fluid closed cavity (13) is filled with magnetorheological fluid (14), and its inner wall is fixed with excitation coils (15) in a matrix array. The compensating hydraulic cylinder (16) is vertically fixed to the pressure side of the back of the C-shaped frame (1), and its upper and lower ends are respectively hinged to the rear top and rear bottom of the C-shaped frame (1). The rodless chamber (17) of the compensating hydraulic cylinder (16) is directly connected to the main actuation hydraulic chamber (9) through the high-pressure oil pipe (18) to form a closed static pressure fluid circuit.

2. The automated stainless steel plate pressing device according to claim 1, characterized in that, The inner wall of the C-shaped frame (1) is provided with a linear guide rail (19), and the sliding seat (7) and the linear guide rail (19) form a sliding guide fit.

3. The automated stainless steel plate pressing device according to claim 1, characterized in that, The ball screw (6) and the output shaft (5) of the servo motor (4) are coaxially connected by a flexible coupling (20).

4. The automated stainless steel plate pressing device according to claim 1, characterized in that, The pressing head housing (11) is a hollow bell-shaped structure, and the edge of the polymer flexible film (12) is sealed and fixed to the bottom end face of the pressing head housing (11) by the flange pressure plate (21).

5. A pressing method, applied to the automated pressing device for stainless steel plates as described in claim 1, characterized in that, include: S1. Control the servo motor (4) to drive the ball screw (6) to rotate, drive the sliding seat (7) to move downward, keep the excitation coil (15) in the de-energized state, so that the polymer flexible film (12) contacts the edge of the stainless steel plate (3) to undergo free deformation and achieve conformal bonding; S2. A preset initial current is passed into the excitation coil (15) to cause the magnetorheological fluid (14) to undergo a chaining effect and be rigidly locked, and the servo motor (4) is controlled to continue to output macroscopic downward pressure to force the stainless steel plate (3) to undergo plastic deformation. S3. Real-time acquisition of the high-frequency torque fluctuation signal of the servo motor (4) and acquisition of the transient pressure pulse signal inside the main actuation hydraulic chamber (9); S4. Integrate the high-frequency torque fluctuation signal in the time dimension to obtain the input work fluctuation amount, and extract the peak value of the transient pressure pulse signal to obtain the transient deformation resistance. S5. Calculate the phase difference between the input work fluctuation and the transient deformation resistance on the time axis, and determine whether the phase difference deviates from the preset standard safety range. When the phase difference deviates from the preset standard safety range, it is determined that the stainless steel plate (3) has entered the high rebound risk zone. The duty cycle of the pulse width modulation signal input to the excitation coil (15) is dynamically adjusted, and the servo motor (4) is controlled to increase the over-bending compensation stroke. When the phase difference does not deviate from the preset standard safety range, the current state of the excitation coil (15) is maintained and the original downward stroke continues to be executed.

6. The pressing method according to claim 5, characterized in that, In step S2, the stainless steel plate (3) generates a reaction force on the pressing head housing (11) and presses the piston rod (10) of the main actuation hydraulic cylinder (8) upward, causing the high pressure fluid in the main actuation hydraulic chamber (9) to be pumped into the rodless chamber (17) of the compensation hydraulic cylinder (16) through the high pressure oil pipe (18), so that the compensation hydraulic cylinder (16) generates an extension thrust and applies a reverse head-down torque to the C-type frame (1) to counteract the opening deformation torque.

7. The pressing method according to claim 5, characterized in that, In step S5, when the high-frequency torque fluctuation signal continues to rise and the transient pressure pulse signal exhibits high-frequency jitter, causing the phase difference to deviate from the preset standard safety range, it is determined that the stainless steel material has locally entered the work hardening stage and accumulated elastic deformation energy, and the system enters the high rebound risk zone.

8. The pressing method according to claim 7, characterized in that, In step S5, when it is determined that the high rebound risk zone has been entered and the downward stroke has reached five percent, the electromagnetic field strength of the excitation coil (15) is reduced proportionally, so that the shear yield stress of the magnetorheological fluid (14) decreases and presents a micro-yield state.

9. The pressing method according to claim 8, characterized in that, In step S5, the stainless steel plate (3) is forced to undergo micro-plastic flow and release internal residual stress by the physical yielding of the polymer flexible membrane (12) in the micro-yield state and the over-bending compensation stroke movement of the servo motor (4).

10. The pressing method according to claim 5, characterized in that, The step S5 is followed by: S601, Control the servo motor (4) to reverse and drive the sliding seat (7) to rise; S602. Control the excitation coil (15) to be de-energized, so that the magnetorheological fluid (14) can be restored to a high fluidity state, and the polymer flexible film (12) can be smoothly separated from the surface of the stainless steel plate (3).

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