Adjustable die for bending and pressing arc of aluminum veneer

Abstract

The application belongs to the technical field of molds, and provides an adjustable mold for bending and arc pressing of aluminum veneer, which comprises a base, a first lower mold body, a second lower mold body, a first driving mechanism, a second driving mechanism and a controller. The controller can obtain the displacement of the upper mold under pressure and the pressure value of the veneer in real time, construct a pressure-displacement response curve and calculate the instantaneous stiffness change rate. When the instantaneous stiffness change rate continuously decreases relative to the stable average of the elastic deformation stage, and the cumulative decrease exceeds the preset threshold, it is determined that the plastic deformation starting inflection point is reached, the convergence speed of the die opening width is dynamically calculated, the two sets of driving mechanisms are driven to drive the lower mold body to slide, and the die opening width is dynamically adjusted with the stamping stroke. After the upper mold is pressed into place and the pressure meets the standard, the lower mold body performs small-amplitude high-frequency reciprocating micro-vibration at the pressure-maintaining position, effectively eliminating the residual stress of the veneer, accurately adapting to the bending and arc pressing processing requirements of the aluminum veneer, effectively suppressing the springback of the workpiece, and greatly improving the forming quality of the aluminum veneer.

Description

Technical Field

[0001] This invention relates to the field of mold technology, and in particular to an adjustable mold for bending and pressing aluminum single-panel. Background Technology

[0002] In the field of aluminum single-panel bending and arc pressing processing, existing molds are mainly divided into two categories: fixed structure and plug-in adjustable structure.

[0003] Fixed molds have a fixed orifice width and forming arc that are determined after manufacturing and cannot be adjusted according to processing requirements. In multi-specification, small-batch, and customized production scenarios, the only solution is to frequently disassemble and replace the entire mold set to adapt to different products. This changeover process is time-consuming and negatively impacts production cycle time. While adjustable molds with insert blocks of varying thicknesses can change the orifice width by placing blocks of different thicknesses at different positions, their adjustment range is limited by the thickness specifications of the insert blocks, allowing switching only between a limited number of discrete settings and preventing continuous adjustment of the orifice width.

[0004] Furthermore, aluminum's elastic modulus is about one-third that of steel, and its springback after bending and unloading can be two to three times that of steel. This makes controlling the springback of aluminum panels more difficult than that of steel. Currently, all adjustable dies follow a working mode of pre-stamping adjustment and in-stamping locking. That is, the lower die assembly is adjusted to the target spacing and rigidly locked before stamping starts, and the lower die assembly remains stationary during the stamping process. However, in the actual bending process, the contact point between the sheet and the lower die edge, i.e., the bending fulcrum, should move accordingly with the increase of bending force. The locked die forcibly fixes this fulcrum at the edge position, and the plastic deformation is forced to concentrate in the area near the fulcrum, unable to extend into the depth of the sheet as the upper die moves downward. Therefore, the springback is difficult to control effectively. At the same time, a large amount of residual stress remains inside the aluminum panel after forming, which is the direct cause of springback and slow deformation in the later stage. However, the existing dies remain stationary during the bottom holding pressure stage, passively maintaining the shape only by static pressure, and lack the means to actively eliminate residual stress. Summary of the Invention

[0005] The purpose of this invention is to provide an adjustable mold for bending and pressing aluminum single-panel, thereby solving or at least alleviating one or more of the above-mentioned problems and other problems existing in the prior art.

[0006] To achieve the above objectives, the main technical solutions adopted by the present invention include: An adjustable mold for bending and pressing aluminum single panels includes: Base; A guiding mechanism is mounted on the base, and a first lower die body and a second lower die body are slidably disposed on the guiding mechanism. A die opening for receiving upper die stamping is formed between the first lower die body and the second lower die body. A first drive mechanism and a second drive mechanism, both of which are mounted on the base; The first driving mechanism is used to drive the first lower mold body to move along the length direction of the guide mechanism, and the second driving mechanism is used to drive the second lower mold body to move along the length direction of the guide mechanism. The controller is signal-connected to the first drive mechanism and the second drive mechanism; The controller is used to acquire the current downward displacement of the upper die and the current pressure value of the upper die acting on the plate in real time. Based on the current downward displacement and the current pressure value, a pressure-displacement response curve is constructed and the instantaneous stiffness change rate is calculated. When the instantaneous stiffness change rate is detected to continuously decrease relative to its stable average value in the elastic deformation stage and the cumulative decrease exceeds a preset threshold, the point is determined as the inflection point of plastic deformation. The controller dynamically calculates the die opening width convergence speed under the current working condition and drives the first drive mechanism and the second drive mechanism to move the first lower die body and the second lower die body along the length direction of the guide mechanism, so that the width of the die opening continuously and dynamically changes with the downward displacement of the upper die throughout the entire downward stroke of the upper die.

[0007] According to the present invention, an adjustable mold for bending and pressing aluminum single-panel is provided in the controller, wherein the controller is provided with a data acquisition module and a pressure detection module; The data acquisition module is signal-connected to the first grating read head installed on the upper mold, and is used to acquire the current downward displacement of the upper mold in real time; The pressure detection module is connected to the pressure sensor installed on the upper mold and is used to detect the current pressure value exerted by the upper mold on the plate.

[0008] In an adjustable mold for bending and pressing aluminum single-panel according to the present invention, the controller is further provided with a dynamic calculation module, which is connected to the data acquisition module and the pressure detection module respectively, and is used to construct the pressure-displacement response curve and calculate the instantaneous stiffness change rate based on the current downward displacement of the upper mold output by the data acquisition module and the current pressure value output by the pressure detection module.

[0009] In an adjustable mold for bending and pressing aluminum single-panel according to the present invention, the controller is further provided with an inflection point determination module. The inflection point determination module is signal-connected to the dynamic calculation module and is used to receive the instantaneous stiffness change rate output by the dynamic calculation module. The inflection point determination module adopts the sliding window comparison method to compare the current instantaneous stiffness change rate with the previous several values ​​in the window. When it is detected that the instantaneous stiffness change rate continuously decreases relative to the stable average value of the elastic deformation stage and the cumulative decrease exceeds a preset threshold, the point is determined as the inflection point of plastic deformation initiation.

[0010] In an adjustable aluminum single-panel bending and pressing mold according to the present invention, the controller is further provided with a drive control module. The drive control module is signal connected to the inflection point determination module and the first drive mechanism and the second drive mechanism respectively. The drive control module is used to receive the inflection point determination result output by the inflection point determination module, and dynamically calculate the die opening width convergence speed under the current working condition based on the inflection point determination result, and drive the first drive mechanism and the second drive mechanism to drive the first lower die body and the second lower die body to slide respectively.

[0011] In an adjustable mold for bending and pressing aluminum single-panel according to the present invention, the controller is further provided with a displacement feedback module and a deviation correction module. A second grating read head is installed at the bottom of the first lower mold body and the bottom of the second lower mold body. A grating ruler corresponding to the second grating read head is fixedly installed on the base. The displacement feedback module is electrically connected to the second grating read head and is used to obtain the actual displacement of the first lower mold body and the second lower mold body in real time. The deviation correction module is signal-connected to the displacement feedback module and the drive control module. It is used to compare the actual displacement with the target displacement and calculate the deviation when the drive control module drives the first lower mold body and the second lower mold body to slide towards or away from each other to change the mold opening width. The deviation correction module is not working during the micro-vibration stage.

[0012] In an adjustable mold for bending and pressing aluminum single-panel according to the present invention, the controller is further provided with a micro-vibration control module, which is signal-connected to the first drive mechanism and the second drive mechanism; After the upper mold is pressed down to the bottom and the current pressure value reaches a preset threshold, the micro-vibration control module drives the first drive mechanism and the second drive mechanism to drive the first lower mold body and the second lower mold body to reciprocate micro-vibrate at the bottom pressure holding position with an amplitude of 0.1 mm to 0.3 mm and a frequency of 5 Hz to 20 Hz, which continues for 10 seconds to 60 seconds and then stops.

[0013] In an adjustable mold for bending and pressing aluminum single-panel according to the present invention, the first driving mechanism and the second driving mechanism each include a driving motor, a lead screw and a bearing with a seat. The driving motor and the bearing with a seat are fixedly mounted on the base. One end of the lead screw is fixedly connected to the rotating shaft of the driving motor through a coupling, and the other end of the lead screw is rotatably connected to the bearing with a seat. The lead screw nut on the lead screw in the first drive mechanism is fixedly connected to the bottom of the first lower mold body; The lead screw nut on the lead screw in the second drive mechanism is fixedly connected to the bottom of the second lower mold body; The drive motor is connected to the controller via a signal connection.

[0014] In an adjustable aluminum single-panel bending and pressing mold according to the present invention, the guiding mechanism includes at least two guide slide rails arranged in parallel to each other. The guide slide rails are fixedly installed on the base. The bottom of the first lower mold body and the bottom of the second lower mold body are both provided with guide slide grooves. The first lower mold body and the second lower mold body are slidably installed on the guide slide rails through the corresponding guide slide grooves.

[0015] This invention also provides a method for bending and arc-forming an aluminum single panel using a mold, comprising the following steps: S1: Place the aluminum panel to be processed on the upper surface of the first lower mold body and the second lower mold body; S2: The controller controls the first drive mechanism and the second drive mechanism to drive the first lower mold body and the second lower mold body to slide back and forth, so that the mold opening width increases to a preset initial value; S3: Start the upper mold to move downward. The controller obtains the current downward displacement of the upper mold and the current pressure value of the upper mold acting on the plate in real time. Based on the current downward displacement and the current pressure value, a pressure-displacement response curve is constructed and the instantaneous stiffness change rate is calculated. When the instantaneous stiffness change rate is detected to continuously decrease relative to its stable average value in the elastic deformation stage and the cumulative decrease exceeds the preset threshold, the point is determined as the inflection point of plastic deformation. The convergence speed of the mold opening width under the current working condition is dynamically calculated, and the first drive mechanism and the second drive mechanism are driven to drive the first lower mold body and the second lower mold body to slide towards each other, so that the mold opening width gradually decreases. S4: After the upper mold is pressed down to the bottom and the current pressure value reaches the preset threshold, the controller stops driving the first lower mold body and the second lower mold body to slide towards each other, and drives the first driving mechanism and the second driving mechanism to drive the first lower mold body and the second lower mold body to reciprocate micro-vibrate at the bottom pressure holding position with an amplitude of 0.1 mm to 0.3 mm and a frequency of 5 Hz to 20 Hz for 10 seconds to 60 seconds and then stops. S5: The controller keeps the first drive mechanism and the second drive mechanism in the energized and locked state, so that the first lower mold body and the second lower mold body remain in the current position, the upper mold returns, and the formed workpiece is taken out.

[0016] This invention has at least the following beneficial effects: By acquiring the current downward displacement of the upper die and the current pressure applied to the sheet metal in real time during the upper die stamping process, and constructing a pressure-displacement response curve and calculating the instantaneous stiffness change rate, the system can accurately identify the starting moment of plastic deformation of the sheet metal when the instantaneous stiffness change rate reaches an inflection point. This triggers a dynamic narrowing of the die opening width at that moment. The die opening width continuously and dynamically changes with the downward displacement of the upper die throughout the entire downward stroke, allowing the bending fulcrum to actively migrate inward during the upper die's downward press. This enables the plastic deformation zone to expand evenly into the depth of the sheet metal, preventing the plastic deformation from being forcibly concentrated near the fulcrum. From a forming mechanism perspective, this suppresses springback and improves the angle retention accuracy of the formed workpiece.

[0017] By combining the data acquisition module with the first grating reader installed on the upper mold and the pressure detection module with the pressure sensor, the displacement signal and pressure signal are synchronously and independently acquired, providing a reliable data foundation for the accurate construction of the response curve and ensuring the timeliness and reliability of the inflection point determination.

[0018] By monitoring the continuous downward trend of the instantaneous stiffness change rate and judging the cumulative decrease through the inflection point determination module, it can adapt to aluminum single panels of different thicknesses and materials, and accurately issue a trigger signal at the initial moment of the sheet yielding, providing precise timing control for the die adjustment action.

[0019] The drive control module comprehensively calculates the die width convergence speed based on the proportional, integral, and derivative control effects of the pressure deviation, so that the die width convergence speed is adaptively adjusted according to the actual working conditions. The convergence action is only started after the sheet enters the plastic stage and the speed is continuously controllable, thus realizing the coordination and synchronization between die width adjustment and sheet deformation process.

[0020] By cooperating with the displacement feedback module and the second grating reader, and through the deviation correction module comparing and correcting the deviation between the actual displacement and the target displacement, positioning errors caused by factors such as lead screw clearance, mechanical friction, and thermal expansion are eliminated, ensuring that the actual position of the lower mold body is consistent with the target position, and that the actual change in the mold opening width strictly follows the downward pressing process of the upper mold.

[0021] The micro-vibration control module drives the first and second drive mechanisms to reciprocate the two lower mold bodies at the bottom pressure holding position after the upper mold is pressed down to the bottom and the pressure reaches the preset threshold. This applies dynamic disturbance to the internal micro-stress field without changing the macro-bending angle of the sheet material, so that the residual stress generated during the bending process can be effectively released in the pressure holding stage, thereby reducing the occurrence of springback from the root. At the same time, no additional processes or equipment are required, simplifying the process flow.

[0022] The drive mechanism, consisting of a drive motor, a lead screw, and a bearing seat, and the guide mechanism, consisting of a guide rail and a guide groove, achieves precise conversion from the rotational motion of the drive motor to the linear sliding of the lower die body. This ensures the linearity of the movement and the positional stability of the two lower die bodies during the sliding adjustment process and when subjected to stamping loads, and ensures the uniformity and consistency of the die opening throughout the entire width direction.

[0023] By increasing the die opening width to a preset initial value before the upper die descends, lateral extension space is reserved for the bottom of the sheet material, avoiding bulging and stress concentration caused by severe compression of the bottom material at the moment the die opening closes; by performing micro-vibration treatment after the upper die is pressed down to the bottom, residual stress inside the molded workpiece is actively released; by keeping the drive mechanism energized and locked before demolding to fix the lower die body in the current position, it is ensured that the workpiece will not undergo secondary deformation due to the movement of the die body during demolding, and finally a dimensionally stable molded workpiece is obtained. Attached Figure Description

[0024] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the guide groove of the present invention; Figure 3 This is a block diagram illustrating the controller architecture principle of the present invention.

[0025] Explanation of icon numbers: 1. Base; 2. First lower mold body; 3. Second lower mold body; 4. Drive motor; 5. Lead screw; 6. Bearing with seat; 7. Grating ruler; 8. Second grating reader; 9. Guide slide rail; 10. Guide groove; 11. Controller; 1101. Data acquisition module; 1102. Drive control module; 1103. Pressure detection module; 1104. Displacement feedback module; 1105. Deviation correction module; 1106. Micro-vibration control module; 1107. Dynamic calculation module; 1108. Inflection point determination module; 12. First grating reader; 13. Pressure sensor. Detailed Implementation

[0026] The following will describe in detail the implementation of this application with reference to the accompanying drawings and embodiments, so that the implementation process of how this application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0027] Please refer to Figures 1 to 3 As shown, an embodiment of the present invention provides an adjustable mold for bending and pressing aluminum single-panel, including a base 1, a guide mechanism, a first drive mechanism, a second drive mechanism, and a controller 11, wherein: A guide mechanism is mounted on a base 1, and a first lower die body 2 and a second lower die body 3 are slidably disposed on the guide mechanism, forming a die opening between the first lower die body 2 and the second lower die body 3 for accommodating the upper die stamping. A first drive mechanism and a second drive mechanism are both mounted on the base 1. The first drive mechanism drives the first lower die body 2 to move along the length direction of the guide mechanism, and the second drive mechanism drives the second lower die body 3 to move along the length direction of the guide mechanism. A controller 11 is signal-connected to the first drive mechanism and the second drive mechanism.

[0028] During the stamping process, the controller 11 continuously acquires the current downward displacement of the upper die and the current pressure value of the upper die acting on the sheet metal. Based on these two sets of data, it internally constructs a response curve of pressure changing with displacement, and calculates the instantaneous stiffness change rate at the current moment. When the controller 11 detects that the instantaneous stiffness change rate continuously decreases relative to its stable average value in the elastic deformation stage and the cumulative decrease exceeds a preset threshold, it determines this point as the inflection point of plastic deformation. Subsequently, based on the pressure-displacement relationship under the current working conditions, it calculates the appropriate convergence speed of the die opening width and drives the first drive mechanism and the second drive mechanism to move the first lower die body 2 and the second lower die body 3 along the length direction of the guide mechanism, so that the width of the die opening continuously and dynamically changes with the change of the downward displacement of the upper die throughout the entire downward stroke of the upper die.

[0029] Specifically, in this embodiment, the controller 11 includes a data acquisition module 1101 and a pressure detection module 1103. The data acquisition module 1101 is connected to a first grating reader 12 mounted on the upper mold and is used to acquire the current downward displacement of the upper mold in real time. The pressure detection module 1103 is connected to a pressure sensor 13 mounted on the upper mold and is used to detect the current pressure value exerted by the upper mold on the plate. Through the above settings, the data acquisition module 1101 reads the position signal of the upper mold via the first grating reader 12. The first grating reader 12 works in conjunction with a grating ruler fixedly mounted on the frame to output a digital pulse signal or analog voltage signal reflecting the real-time position of the upper mold. After receiving the signal, the data acquisition module 1101 converts it into the current downward displacement data of the upper mold. The pressure detection module 1103 detects the pressure exerted by the upper mold on the plate in real time via the pressure sensor 13.

[0030] In this embodiment, the controller 11 also includes a dynamic calculation module 1107. The dynamic calculation module 1107 is signal-connected to the data acquisition module 1101 and the pressure detection module 1103, respectively, and is used to receive the current downward displacement of the upper mold output by the data acquisition module 1101 and the current pressure value output by the pressure detection module 1103. The dynamic calculation module 1107 smooths the received displacement and pressure data to eliminate noise signals that may be mixed in during sampling. Then, it constructs a response curve reflecting the current deformation behavior of the plate material with displacement as the abscissa and pressure as the ordinate. Based on the ratio of pressure change to displacement change between adjacent sampling points on the curve, it calculates the instantaneous stiffness change rate, which reflects the instantaneous ability of the plate material to resist deformation at the current deformation moment. The sampling frequency of the dynamic calculation module 1107 is not less than 1000 Hz, the width of the sliding window is set to 10 to 50 sampling points, and the smoothing process uses a sliding window filtering algorithm to filter the input displacement and pressure values.

[0031] In this embodiment, the controller 11 also includes an inflection point determination module 1108. The inflection point determination module 1108 is signal-connected to the dynamic calculation module 1107 and is used to receive the instantaneous stiffness change rate output by the dynamic calculation module 1107. Internally, the inflection point determination module 1108 first identifies the stable average value of the instantaneous stiffness change rate when the plate is in the elastic deformation stage. This stable average value is obtained by taking the arithmetic mean of the instantaneous stiffness change rates of multiple sampling points within the elastic stage. Subsequently, the inflection point determination module 1108 compares the instantaneous stiffness change rate at the current moment with this stable average value, using a sliding window comparison method with a window size of 10 sampling points. When the instantaneous stiffness change rate is detected to show a continuous decreasing trend relative to the stable average value, and the total magnitude of the decrease exceeds a preset threshold, the current moment is determined as the inflection point of plastic deformation. When the plate is in the elastic deformation stage, the pressure increases essentially linearly with displacement, and the instantaneous stiffness change rate remains within a relatively stable numerical range. The average value of this stage serves as the benchmark for subsequent determinations. As the sheet begins to plastically yield, the increase in pressure relative to the increase in displacement gradually decreases, and the instantaneous rate of change of stiffness subsequently declines. The inflection point determination module 1108 accurately identifies the critical moment when the sheet transitions from elastic deformation to plastic deformation by capturing the starting point of this downward trend. The inflection point determination module 1108 outputs the determination result to other modules of the controller 11, providing a trigger signal for the subsequent calculation of the die width convergence speed.

[0032] As a preferred embodiment, the inflection point determination module 1108 uses a sliding window comparison method to determine the trend of the instantaneous stiffness change rate. The window size N is 10 sampling points. The initial stage value is defined as the stable average value of the instantaneous stiffness change rate from the time the upper mold contacts the plate until the inflection point appears. When the instantaneous stiffness change rate value decreases more than 5 times relative to the stable average value and the cumulative decrease exceeds 15% of the stable average value, the inflection point determination module 1108 determines the point as the inflection point of plastic deformation. The preset threshold of 15% can be adjusted according to the mechanical properties of different grades of aluminum alloys. For 5052 aluminum alloy, it can be set to 12%, and for 6061 aluminum alloy, it can be set to 18%.

[0033] In this embodiment, the controller 11 also includes a drive control module 1102. The drive control module 1102 is connected to the inflection point determination module 1108, the first drive mechanism, and the second drive mechanism. The drive control module 1102 receives the inflection point determination result output by the inflection point determination module 1108. After confirming that the sheet has entered the plastic deformation stage, it calculates a control quantity based on the deviation between the currently detected pressure value and the target pressure value, according to the control actions in the proportional, integral, and derivative directions. This control quantity determines the convergence speed of the die opening width. The proportional action responds instantly based on the magnitude of the current deviation, the integral action accumulates historical deviations to eliminate steady-state errors, and the derivative action makes adjustments in advance based on the trend of deviation changes to suppress oscillations. The drive control module 1102 converts the calculated control quantity into speed commands or position commands and sends them to the first drive mechanism and the second drive mechanism via a bus or pulse direction signal. The first drive mechanism and the second drive mechanism drive the first lower die body 2 and the second lower die body 3 to slide towards each other along the length direction of the guide mechanism according to the received commands, so that the die opening width gradually decreases. Through the combined effect of the above three links of proportional, integral, and derivative, the die width is accurately and continuously dynamically adjusted throughout the entire downward stroke of the upper die.

[0034] As a preferred implementation, for 5052 aluminum alloy sheets with a thickness of 1.0 mm to 3.0 mm, the recommended range for proportional gain is 0.3 to 1.5, the recommended range for integral gain is 0.05 to 0.3, and the recommended range for derivative gain is 0 to 0.5. For 6061 aluminum alloy sheets with a thickness of 1.0 mm to 3.0 mm, the recommended range for proportional gain is 0.5 to 2.5, the recommended range for integral gain is 0.08 to 0.4, and the recommended range for derivative gain is 0 to 1.0. The specific values ​​of the above parameters are determined through on-site trial and error: initially set the proportional gain to 0.5, the integral time to 3 seconds (the ratio of proportional gain to integral time), and the derivative gain to 0. Observe the pressure response curve; if pressure oscillations occur, gradually decrease the proportional gain; if the response is slow, gradually increase the proportional gain until the system response speed and stability reach a balance. Different thicknesses and materials of aluminum panels correspond to different optimal ratios, integral and derivative control parameters.

[0035] In this embodiment, the controller 11 also includes a displacement feedback module 1104 and a deviation correction module 1105. Second grating read heads 8 are installed at the bottom of both the first lower mold body 2 and the bottom of the second lower mold body 3. Grating rulers 7, corresponding one-to-one with the second grating read heads 8, are fixedly installed on the base 1. The displacement feedback module 1104 is electrically connected to the second grating read heads 8 and is used to acquire the actual displacement of the first lower mold body 2 and the second lower mold body 3 in real time. The deviation correction module 1105 is signal-connected to the displacement feedback module 1104 and to the drive control module 1102. When the drive control module 1102 drives the first lower mold body 2 and the second lower mold body 3 to slide towards or away from each other to change the mold opening width, the deviation correction module 1105 compares the actual displacement returned by the displacement feedback module 1104 with the current target displacement and calculates the deviation between the two. Then, based on this deviation, a correction command is generated and sent to the drive control module 1102. The drive control module 1102 controls the first and second drive mechanisms to make minor adjustments according to the correction command until the deviation between the actual displacement and the target displacement is reduced to within the allowable range. This allowable error is set to ±0.01 mm. Through the above-mentioned fully closed-loop position control, positioning errors caused by lead screw backlash, mechanical friction, thermal expansion, etc., are eliminated, ensuring the accuracy of mold opening width adjustment.

[0036] The control mode switching between the deviation correction module 1105 and the micro-vibration control module 1106 is executed according to the following logic: During the working stage where the drive control module 1102 drives the first lower mold body 2 and the second lower mold body 3 to slide towards each other to change the mold opening width, the deviation correction module 1105 is in an active state and continuously performs closed-loop position correction. When the upper mold is pressed down to the bottom and the current pressure value reaches the preset threshold, the controller 11 sends a command to the drive control module 1102 to stop the sliding towards each other, and the drive control module 1102 then controls the first drive mechanism and the second drive mechanism to stop rotating. After the drive motor 4 completely stops rotating, the controller 11 records the current position of the first lower mold body 2 and the second lower mold body 3 as the bottom pressure holding position and sets this position as the reference position for micro-vibration. Subsequently, the micro-vibration control module 1106 is activated, generating periodic position commands centered on this reference position, and controlling the first drive mechanism and the second drive mechanism to perform reciprocating micro-vibration near the bottom pressure holding position. The deviation correction module 1105 does not operate during the micro-vibration phase to avoid control conflicts between its closed-loop correction function and the periodic position commands of the micro-vibration control module 1106. The time interval between the stop of the opposing sliding and the start of micro-vibration does not exceed 50 milliseconds to ensure that the die width does not passively drift due to the power failure of the drive motor 4 during the switching process.

[0037] In this embodiment, the controller 11 is further provided with a micro-vibration control module 1106. The micro-vibration control module 1106 is signal-connected to the first drive mechanism and the second drive mechanism. After the upper mold is pressed down to the bottom and the current pressure value reaches the preset threshold, the micro-vibration control module 1106 generates a periodically changing position command according to the set amplitude and frequency values, and sends the position command to the first drive mechanism and the second drive mechanism through a bus or pulse direction signal. The first drive mechanism and the second drive mechanism are controlled to perform high-frequency forward and reverse rotation near the bottom pressure holding position, respectively driving the first lower mold body 2 and the second lower mold body 3 to perform reciprocating micro-vibration at the bottom pressure holding position with an amplitude of 0.1 mm to 0.3 mm and a frequency of 5 Hz to 20 Hz, which continues for 10 seconds to 60 seconds and then stops. The duration of this micro-vibration is determined based on the thickness of the sheet material; a shorter duration is used for thinner sheets, and a longer duration is used for thicker sheets. For 1.0 mm thick aluminum panels, the duration is 10 to 20 seconds; for 2.0 mm thick aluminum panels, it is 20 to 40 seconds; and for 3.0 mm thick aluminum panels, it is 40 to 60 seconds. The amplitude of this micro-vibration is much smaller than the total change in the die width during the closing stage, and it does not change the macroscopic bending angle of the already formed sheet material. The effect of the micro-vibration is only applied to the microscopic stress field inside the material, promoting the effective release of residual stress during the pressure holding stage.

[0038] To verify the effect of micro-vibration on residual stress elimination, the applicant used the blind hole method to test the residual stress of the aluminum single-panel bending component after micro-vibration treatment. The test results showed that after micro-vibration treatment with an amplitude of 0.2 mm, a frequency of 10 Hz, and a duration of 30 seconds, the peak value of residual stress in the bending corner area was significantly reduced compared with the control sample without micro-vibration treatment, and the uniformity of stress distribution along the bending line was significantly improved, proving that micro-vibration treatment has an active stress elimination effect on residual stress.

[0039] In this embodiment, both the first and second drive mechanisms include a drive motor 4, a lead screw 5, and a bearing 6. The drive motor 4 and the bearing 6 are both fixedly mounted on the base 1. One end of the lead screw 5 is fixedly connected to the rotating shaft of the drive motor 4 via a coupling, and the other end of the lead screw 5 is rotatably connected to the bearing 6. The lead screw nut on the lead screw 5 in the first drive mechanism is fixedly connected to the bottom of the first lower mold body 2. The lead screw nut on the lead screw 5 in the second drive mechanism is fixedly connected to the bottom of the second lower mold body 3. The drive motor 4 is signal-connected to the controller 11. When the drive motor 4 receives the drive command from the controller 11, the shaft of the drive motor 4 rotates and drives the lead screw 5 to rotate through the coupling. The lead screw nut on the lead screw 5 is threadedly engaged with the lead screw 5. When the lead screw 5 rotates, the lead screw nut moves linearly along the axis of the lead screw 5. Since the lead screw nut in the first drive mechanism is fixedly connected to the bottom of the first lower die body 2, and the lead screw nut in the second drive mechanism is fixedly connected to the bottom of the second lower die body 3, the linear movement of the lead screw nut drives the corresponding lower die body to slide along the length direction of the guide mechanism. The rotational motion of the drive motor 4 is precisely converted into the linear sliding of the lower die body, realizing the precise adjustment of the die opening width. The lead screw 5 is equipped with a telescopic dust cover to prevent aluminum chips and dust generated by bending from entering the lead screw pair, extending the service life of the lead screw 5 and the lead screw nut. The lead screw 5 and the lead screw nut need to be lubricated regularly to ensure the smooth operation and accuracy maintenance of the lead screw pair.

[0040] In this embodiment, the guiding mechanism includes at least two parallel guide rails 9. The guide rails 9 are fixedly mounted on the base 1 and extend parallel to the length of the base 1, together forming the sliding guide surface of the lower mold body. The bottom of the first lower mold body 2 has guide grooves 10, the same number and corresponding in position as the guide rails 9. Similarly, the bottom of the second lower mold body 3 also has guide grooves 10, the same number and corresponding in position as the guide rails 9. The first lower mold body 2 is slidably mounted on the guide rails 9 via the guide grooves 10 at its bottom, and the second lower mold body 3 is slidably mounted on the guide rails 9 via the guide grooves 10 at its bottom. The guide grooves 10 and guide rails 9 are in a sliding fit. The guide rails 9 constrain the movement direction of the guide grooves 10, ensuring that the first lower mold body 2 and the second lower mold body 3 can only slide along the length of the guide rails 9 without shifting or rotating in other directions. The aforementioned guiding mechanism ensures the straightness and stability of the first lower mold body 2 and the second lower mold body 3 during the sliding process, effectively avoiding misalignment and deviation problems that are prone to occur during adjustment. Lubricating oil needs to be added to the guide rail 9 and guide groove 10 regularly to ensure smooth operation and maintain the precision of the sliding pair.

[0041] When bending aluminum panels using the above-mentioned mold, the following steps are included: S1: Place the aluminum panel to be processed on the upper surface of the first lower mold body 2 and the second lower mold body 3.

[0042] S2: Controller 11 controls the first drive mechanism and the second drive mechanism to drive the first lower mold body 2 and the second lower mold body 3 to slide back and forth, so that the mold opening width increases to a preset initial value. The preset initial value is set according to the thickness of the sheet material, which is 6 to 10 times the thickness of the sheet material. For aluminum single panels with a thickness of 1.0 mm, it is 6 to 8 times; for aluminum single panels with a thickness of 2.0 mm, it is 7 to 9 times; and for aluminum single panels with a thickness of 3.0 mm, it is 8 to 10 times. The purpose of this step is to reserve lateral extension space for the bottom of the sheet material to avoid the bottom material being subjected to strong lateral compression at the moment the mold opening closes, which would cause wavy bulging and stress concentration.

[0043] It should be noted that after step S2 is completed, the upper mold starts its downward movement, and no force is applied to the upper mold before it contacts the sheet material. Once the upper mold begins to contact the sheet material, the pre-pressure of the upper mold gradually builds up, and the sheet material is slightly pressed between the upper end faces of the first lower mold body 2 and the second lower mold body 3. In step S2, the die opening width increases from back-to-back sliding, and then in step S3, it decreases from front-to-back sliding. During this transition, the upper mold has already contacted the upper surface of the sheet material and applied a pre-pressure no less than several times the weight of the sheet material. This pre-pressure is sufficient to stably press the sheet material between the upper end faces of the first lower mold body 2 and the second lower mold body 3, thereby ensuring that the sheet material does not experience horizontal positioning displacement during the die opening width transition. Simultaneously, the friction between the upper end faces of the two lower mold bodies and the sheet material increases significantly under the pre-pressure, further limiting the lateral sliding of the sheet material during the die opening width transition.

[0044] S3: The upper die begins its downward movement. Controller 11 acquires the current downward displacement of the upper die and the current pressure value exerted by the upper die on the sheet metal in real time. Based on the current downward displacement and pressure value, a pressure-displacement response curve is constructed, and the instantaneous stiffness change rate is calculated. When the instantaneous stiffness change rate is detected to continuously decrease relative to its stable average value in the elastic deformation stage, and the cumulative decrease exceeds a preset threshold, this point is determined as the inflection point of plastic deformation initiation. The die opening width convergence speed under the current working condition is dynamically calculated, and the first and second drive mechanisms are driven to respectively drive the first lower die body 2 and the second lower die body 3 to slide towards each other, causing the die opening width to gradually decrease. The purpose of this step is to make the bending fulcrum dynamically move inward as the upper die presses down, forcing the plastic deformation zone to extend uniformly deeper into the sheet metal, thus suppressing springback in principle.

[0045] S4: After the upper mold is pressed down to the bottom and the current pressure value reaches the preset threshold, the controller 11 stops driving the first lower mold body 2 and the second lower mold body 3 to slide towards each other, and drives the first drive mechanism and the second drive mechanism to drive the first lower mold body 2 and the second lower mold body 3 to reciprocate micro-vibrate at the bottom pressure holding position with an amplitude of 0.1 mm to 0.3 mm and a frequency of 5 Hz to 20 Hz, which continues for 10 seconds to 60 seconds and then stops. The purpose of this step is to actively eliminate the residual stress inside the plate through micro-amplitude high-frequency vibration, and suppress springback from the root. The amplitude of the micro-vibration is much smaller than the total change in the die opening width in the closing section, which is insufficient to change the macroscopic bending angle of the plate. The micro-vibration only acts on the stress field at the microscopic level inside the material.

[0046] In step S4, the switching between the deviation correction module 1105 and the micro-vibration control module 1106 is performed according to the following logic: When the upper mold is pressed down to the bottom and the current pressure value reaches a preset threshold, the controller 11 first sends a command to the drive control module 1102 to stop the opposing sliding. The drive control module 1102 controls the first drive mechanism and the second drive mechanism to stop rotating. After the drive motor 4 completely stops rotating, the controller 11 records the current positions of the first lower mold body 2 and the second lower mold body 3 as the bottom pressure holding position and sets this position as the reference position for micro-vibration. Subsequently, the micro-vibration control module 1106 is activated and generates periodic position commands centered on this reference position. The time interval between the stopping of opposing sliding and the start of micro-vibration does not exceed 50 milliseconds to ensure that the mold opening width does not passively drift during the switching process. The deviation correction module 1105 is inactive during the micro-vibration stage.

[0047] S5: Controller 11 keeps the first drive mechanism and the second drive mechanism in the energized and locked state, so that the first lower mold body 2 and the second lower mold body 3 remain in the current position, the upper mold returns, and the formed workpiece is taken out.

[0048] Specifically, in this embodiment, the controller 11 is also provided with a convergence speed calculation module, which is signal-connected to the inflection point determination module 1108 and the drive control module 1102. After receiving the inflection point determination result from the inflection point determination module 1108, the convergence speed calculation module dynamically calculates the optimal convergence speed for the die width under the current working condition according to the following equation. : ; in, As the baseline convergence speed, This represents the stable mean of the instantaneous rate of change of stiffness during the elastic deformation stage. The current instantaneous rate of change of stiffness. For the target pressure value, This is the current pressure value. The first derivative of the instantaneous rate of change of stiffness with respect to time. The characteristic time constant of the material; The weighting coefficients are and satisfy the following conditions: , The value range is 0.35 ~ 0.65; The value range is 0.25 ~ 0.55; The value range is 0.03 ~ 0.12; and It is a non-linear adjustment index; The convergence rate calculation module will calculate the... The output is sent to the drive control module 1102, and the drive control module 1102, according to... Control the operating speed of the first drive mechanism and the second drive mechanism.

[0049] The stiffness attenuation term is: The pressure deviation item is: The material characteristics are: .

[0050] Assume the dimensions of each parameter are as follows:

[0051] Example of parameter settings: Taking a 2.0 mm thick 5052-H32 aluminum alloy sheet as an example, the parameters are set as follows:

[0052] Calculation examples under different working conditions: Working condition 1: The sheet material has just entered the plastic deformation stage Setting parameters: , , Substitute the parameters into the equation: .

[0053] At this point, the pressure deviation contributes the most (0.2887), and the die opening closes at a relatively fast speed to push the sheet metal into shape.

[0054] Working Condition 2: Fully Plastic Deformed Stage of the Sheet Setting parameters: , , Substitute the parameters into the equation: .

[0055] At this point, the stiffness attenuation term becomes dominant (0.3235), and the die closing speed is determined by the degree of material softening.

[0056] Condition 3: The sheet material is about to be formed. Setting parameters: , , Substitute the parameters into the equation: .

[0057] At this point, the stiffness attenuation term contributes the most (0.4723), and the die continues to close. However, in actual control, when... achieve When the rate is above 90%, the drive control module 1102 will... Amplitude limiting is applied to prevent overshoot.

[0058] Operating Condition 4: Actual Output After Amplitude Limiting Intervention Working condition three calculation The value is 0.7429 mm / s, but at the end of the molding process, to avoid overshoot, the drive control module 1102 will determine the current pressure value. With target pressure value The proportional relationship. When At that time, the drive control module 1102 controls the drive in the following manner. Limiting the amplitude: like ,but ; Taking working condition three as an example: According to the width restriction rules: ,at this time It is limited to below 0.45 mm / s.

[0059] By dynamically calculating the optimal convergence speed for the die width according to the above equation using the convergence speed calculation module, the following beneficial effects are achieved: First, the convergence speed of the die opening width is no longer a fixed value or determined by a single variable. Instead, it integrates information from three dimensions: the degree of material stiffness attenuation, pressure deviation, and changes in material characteristics. This directly reflects the softening process of the sheet material, enabling faster convergence when the sheet material is sufficiently softened to utilize plastic flow capacity. When the sheet material is not sufficiently softened, the die opening slows down its convergence to avoid excessive compression.

[0060] Second, the nonlinear adjustment index and The introduction of this feature allows for flexible adjustment of the control curve, making it easy to adapt to aluminum panels of different thicknesses and materials. When When the value is too large, the control effect of stiffness attenuation is concentrated in the later stage; when The smaller control response is concentrated in the early stage, enabling the equations to adapt to a wide range of operating conditions, from thin plates to thick plates, and from soft aluminum alloys to hard aluminum alloys.

[0061] Third, material characteristics The introduction of this factor allows the convergence speed of the die orifice to predict the trend of stiffness changes. When stiffness decreases rapidly, this factor is negative, and the convergence speed is appropriately reduced to allow the material sufficient deformation time and prevent excessive uneven deformation. When the decrease in stiffness slows down, this factor approaches zero, and its influence on the convergence speed tends to disappear. This control strategy can effectively avoid plate cracking or stress concentration caused by excessive convergence. Three weighting coefficients are used. The independent adjustability allows this solution to adapt to the differences in mechanical properties of different grades of aluminum alloys. For machining 5052 aluminum alloy, this can be achieved by increasing the... Enhance the response to stiffness decay; for materials with good plastic flow, such as 6061 aluminum alloy, this can be achieved by increasing... Enhanced response to pressure deviation.

[0062] Fourth, material characteristic time constant The introduction of this parameter enables the equation to quantitatively describe the sensitivity of different materials to the convergence rate, incorporating the differences in material constitutive properties into the calculation scheme for the convergence speed of the die width. This parameter allows the control algorithm to adapt to different sheet materials, significantly improving control accuracy and material adaptability.

[0063] Fifth, in accordance with constraints. In addition, the end-stage pressure limiting strategy ensures that the die convergence speed does not exceed the allowable operating range of the equipment under any working conditions, fundamentally avoiding product quality problems caused by abnormal speed.

[0064] It is worth noting that the output of the convergence speed calculation module... As the speed command input to the drive control module 1102, the PID control in the drive control module 1102 is responsible for converting the speed command into a specific motor drive signal and executing closed-loop speed control. That is, the convergent speed calculation module is responsible for generating the speed target value, and the drive control module 1102 is responsible for executing and tracking the speed target.

[0065] Working principle and process: The workflow of the convergence speed calculation module is as follows: Step 1: The convergence speed calculation module continuously waits for the output status of the inflection point determination module 1108. Before the inflection point determination module 1108 outputs the inflection point determination result, the convergence speed calculation module remains in standby mode and does not perform convergence speed calculation.

[0066] Step Two: After the inflection point determination module 1108 outputs the inflection point determination result, the convergence speed calculation module is activated and begins data acquisition. It automatically and continuously acquires the current pressure value from the pressure detection module 1103. Read the continuous-time stiffness sequence from the dynamic calculation module 1107. Simultaneously read the preset from the parameter memory. , , Weighting coefficients ,index Parameters such as these.

[0067] Step 3: The convergence rate calculation module calculates based on... Time series data computation The central difference method is used: The calculations are performed, and low-pass filtering is used to eliminate signal noise.

[0068] Step 4: The convergence speed calculation module substitutes all the above parameters into the equation to calculate the optimal convergence speed for the die width under the current working conditions. .

[0069] Step 5: The convergence rate calculation module calculates the... Two levels of clipping are applied. The first level is hardware clipping: if... Then take ;like Then take This ensures that the output speed does not exceed the equipment's capacity. The second level is pressure segmentation limiting: based on the current pressure value and the target pressure value... The proportional relationship further limits the upper limit of output speed, when Segmented amplitude limiting is activated at the specified time.

[0070] Step Six: The convergence speed calculation module will complete the calculation after amplitude limiting. The signal is sent to the drive control module 1102. The drive control module 1102 then... By controlling the rotational speeds of the first and second drive mechanisms, the closing speed of the die opening width can be precisely controlled.

[0071] Step 7: The above steps are repeated in each control cycle to achieve dynamic adjustment of the die convergence speed according to the material state; when the current pressure reaches the forming threshold and remains stable for a preset time, the controller stops driving the actuator to move downward, and the bending forming process is completed.

[0072] In summary, the working principle and usage method of the adjustable bending and pressing die for aluminum single-panel in this application are as follows: The mold includes a base 1, a guiding mechanism, a first driving mechanism, a second driving mechanism, and a controller 11. The guiding mechanism is mounted on the base 1, and a first lower mold body 2 and a second lower mold body 3 are slidably disposed on the guiding mechanism, forming a die opening between them for receiving the upper mold stamping. Both the first and second driving mechanisms are mounted on the base 1 and are used to drive the first lower mold body 2 and the second lower mold body 3 to move along the length of the guiding mechanism, respectively. The controller 11 is signal-connected to the first and second driving mechanisms.

[0073] In use, the aluminum panel to be processed is first placed on the upper surface of the first lower mold body 2 and the second lower mold body 3. The controller 11 controls the first drive mechanism and the second drive mechanism to drive the first lower mold body 2 and the second lower mold body 3 to slide back and forth, so that the width of the mold opening increases to a preset initial value. This preset initial value is set according to the thickness of the sheet material, which is 6 to 10 times the thickness of the sheet material. For aluminum panels with a thickness of 1.0 mm, it is 6 to 8 times; for aluminum panels with a thickness of 2.0 mm, it is 7 to 9 times; and for aluminum panels with a thickness of 3.0 mm, it is 8 to 10 times. This leaves a lateral extension space at the bottom of the sheet material, so as to avoid the bottom material being subjected to strong lateral compression at the moment the mold opening closes, which would cause bulging and stress concentration.

[0074] The upper mold then begins its descent. During this descent, the first grating reader 12 installed on the upper mold reads the position signal in real time and transmits it to the data acquisition module 1101 within the controller 11. The pressure sensor 13 installed on the upper mold detects the pressure value exerted by the upper mold on the plate material in real time and transmits it to the pressure detection module 1103 within the controller 11. After receiving the displacement and pressure data, the dynamic calculation module 1107 within the controller 11 constructs a pressure-displacement response curve with displacement as the abscissa and pressure as the ordinate. It then calculates the instantaneous stiffness change rate based on the ratio of pressure change to displacement change between adjacent sampling points on the curve. The sampling frequency of the dynamic calculation module 1107 is no less than 1000 Hz, and a sliding window filtering algorithm is used to smooth the input displacement and pressure values. The window size is set to 10 to 50 sampling points. The inflection point determination module 1108 compares the instantaneous stiffness change rate at the current moment with the values ​​at several previous moments. Internally, the module first identifies the stable mean value of the instantaneous stiffness change rate when the plate is in the elastic deformation stage. This stable mean value is obtained by taking the arithmetic mean of the instantaneous stiffness change rates at multiple sampling points within the elastic stage. Using a sliding window comparison method with a window size of 10 sampling points, when the instantaneous stiffness change rate is detected to show a continuous decrease relative to this stable mean value, and the cumulative decrease exceeds a preset threshold, this moment is determined as the starting inflection point where the plate transitions from elastic deformation to plastic deformation. As a preferred embodiment, the initial stage value is defined as the stable average value of the instantaneous stiffness change rate from the time the upper mold contacts the plate until the inflection point appears. When the instantaneous stiffness change rate value decreases more than 5 times relative to the stable average value and the cumulative decrease exceeds 15% of the stable average value, the inflection point determination module 1108 determines the point as the inflection point of plastic deformation. The preset threshold of 15% can be adjusted according to the mechanical properties of different grades of aluminum alloys. For 5052 aluminum alloy, it can be set to 12%, and for 6061 aluminum alloy, it can be set to 18%.

[0075] After the inflection point determination module 1108 outputs the inflection point determination result, the convergence rate calculation module is activated. The convergence rate calculation module calculates the convergence rate based on the aforementioned equation, using the current instantaneous rate of change of stiffness K(t) relative to the stable mean value during the elastic stage. The degree of attenuation, the current pressure value F(t) and the target pressure value The deviation and the first derivative of the rate of change of stiffness with respect to time The optimal convergence rate under the current operating conditions is calculated comprehensively. and will The speed command is output to the drive control module 1102. The drive control module 1102 will... As a speed setpoint, the speed command is converted into a specific drive signal through the control of the proportional, integral and derivative directions inside, which controls the first drive mechanism and the second drive mechanism to drive the first lower mold body 2 and the second lower mold body 3 to slide towards each other, so that the width of the die opening changes continuously and dynamically with the change of the downward displacement of the upper mold throughout the entire downward stroke of the upper mold.

[0076] After confirming that the sheet metal has entered the plastic deformation stage, the drive control module 1102 calculates the convergence speed of the die width based on the deviation between the currently detected pressure value and the target pressure value, using proportional, integral, and derivative control actions. The calculated control quantity is then converted into speed or position commands and sent to the first and second drive mechanisms. For 5052 aluminum alloy sheets with a thickness of 1.0 mm to 3.0 mm, the recommended range for proportional gain is 0.3 to 1.5, for integral gain is 0.05 to 0.3, and for derivative gain is 0 to 0.5. For 6061 aluminum alloy sheets with a thickness of 1.0 mm to 3.0 mm, the recommended range for proportional gain is 0.5 to 2.5, for integral gain is 0.08 to 0.4, and for derivative gain is 0 to 1.0. The initial proportional gain is set to 0.5, and the integral time is set to 3 seconds. The integral gain is the ratio of the proportional gain to the integral time. The derivative gain is initially set to 0. Observe the pressure response curve. If pressure oscillation occurs, gradually decrease the proportional gain; if the response is slow, gradually increase the proportional gain until the system response speed and stability reach a balance. The drive motor 4 in the first drive mechanism drives the lead screw 5 to rotate. The lead screw nut moves linearly along the axis of the lead screw 5, thereby driving the first lower die body 2, which is fixedly connected to it, to slide along the guide rail 9. The second drive mechanism drives the second lower die body 3 to slide in the same way. The two lower die bodies slide towards each other, causing the die opening width to gradually decrease. Throughout the entire downward stroke, the die opening width continuously and dynamically changes with the change in the downward displacement of the upper die.

[0077] It should be noted that after step S2 is completed, the upper mold starts its downward movement, and no force is applied to the upper mold before it contacts the sheet material. Once the upper mold begins to contact the sheet material, the pre-pressure of the upper mold gradually builds up, and the sheet material is slightly pressed between the upper end faces of the first lower mold body 2 and the second lower mold body 3. In step S2, the die opening width increases from back-to-back sliding, and then in step S3, it decreases from front-to-back sliding. During this transition, the upper mold has already contacted the upper surface of the sheet material and applied a pre-pressure no less than several times the weight of the sheet material. This pre-pressure is sufficient to stably press the sheet material between the upper end faces of the first lower mold body 2 and the second lower mold body 3, thereby ensuring that the sheet material does not experience horizontal positioning displacement during the die opening width transition. Simultaneously, the friction between the upper end faces of the two lower mold bodies and the sheet material increases significantly under the pre-pressure, further limiting the lateral sliding of the sheet material during the die opening width transition.

[0078] During the die width adjustment process, the second grating reader 8, installed at the bottom of the first lower die body 2 and the bottom of the second lower die body 3, works in conjunction with the grating ruler 7 fixed on the base 1. The displacement feedback module 1104 acquires the actual displacement of the two lower die bodies in real time. The deviation correction module 1105 compares the actual displacement with the target displacement and calculates the deviation. Based on the deviation, it generates a correction command. The drive control module 1102 controls the first drive mechanism and the second drive mechanism to make minor adjustments according to the correction command until the deviation between the actual displacement and the target displacement is reduced to within the allowable range. This allowable error is set to ±0.01 mm, forming a fully closed-loop position control.

[0079] The control mode switching between the deviation correction module 1105 and the micro-vibration control module 1106 is executed according to the following logic: During the working stage where the drive control module 1102 drives the first lower mold body 2 and the second lower mold body 3 to slide towards each other to change the mold opening width, the deviation correction module 1105 is in an active state and continuously performs closed-loop position correction. When the upper mold is pressed down to the bottom and the current pressure value reaches the preset threshold, the controller 11 sends a command to the drive control module 1102 to stop the sliding towards each other, and the drive control module 1102 then controls the first drive mechanism and the second drive mechanism to stop rotating. After the drive motor 4 completely stops rotating, the controller 11 records the current position of the first lower mold body 2 and the second lower mold body 3 as the bottom pressure holding position and sets this position as the reference position for micro-vibration. Subsequently, the micro-vibration control module 1106 is activated, generating periodic position commands centered on this reference position, and controlling the first drive mechanism and the second drive mechanism to perform reciprocating micro-vibration near the bottom pressure holding position. The deviation correction module 1105 does not operate during the micro-vibration phase to avoid control conflicts between its closed-loop correction function and the periodic position commands of the micro-vibration control module 1106. The time interval between the stop of the opposing sliding and the start of micro-vibration does not exceed 50 milliseconds to ensure that the die width does not passively drift due to the power failure of the drive motor 4 during the switching process.

[0080] When the upper mold is pressed down to the bottom and the current pressure value reaches the preset threshold, the micro-vibration control module 1106 generates a periodically changing position command according to the set amplitude and frequency values, and sends it to the first drive mechanism and the second drive mechanism. The first drive mechanism and the second drive mechanism are controlled to perform high-frequency forward and reverse rotation near the bottom pressure holding position, respectively driving the first lower mold body 2 and the second lower mold body 3 to perform reciprocating micro-vibration at the bottom pressure holding position with an amplitude of 0.1 mm to 0.3 mm and a frequency of 5 Hz to 20 Hz, which lasts for 10 seconds to 60 seconds and then stops. The duration of this micro-vibration is determined according to the thickness of the sheet material. A shorter time is used when the thickness is thinner and a longer time is used when the thickness is thicker. For aluminum single panels with a thickness of 1.0 mm, the duration is 10 seconds to 20 seconds; for aluminum single panels with a thickness of 2.0 mm, the duration is 20 seconds to 40 seconds; and for aluminum single panels with a thickness of 3.0 mm, the duration is 40 seconds to 60 seconds. The amplitude of this micro-vibration is much smaller than the total change in the die width during the closing stage, and it does not change the macroscopic bending angle of the already formed sheet metal, acting only on the stress field at the microscopic level inside the material. To verify the effect of micro-vibration on eliminating residual stress, the applicant used the blind hole method to test the residual stress of the aluminum single-panel bending parts after micro-vibration treatment. The test results show that the peak value of residual stress in the bending corner area after micro-vibration treatment is significantly reduced compared with the control sample without micro-vibration treatment, and the uniformity of stress distribution along the bending line is significantly improved.

[0081] Finally, the controller 11 keeps the first drive mechanism and the second drive mechanism in the energized and locked state, so that the first lower mold body 2 and the second lower mold body 3 remain in the current position, the upper mold returns, and the molded workpiece is taken out.

[0082] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept by means of the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. An adjustable mold for bending and pressing aluminum single-panel, characterized in that, include: Base (1); A guiding mechanism is mounted on the base (1). A first lower mold body (2) and a second lower mold body (3) are slidably disposed on the guiding mechanism. A die opening for accommodating upper die stamping is formed between the first lower mold body (2) and the second lower mold body (3). A first drive mechanism and a second drive mechanism are both mounted on the base (1); The first driving mechanism is used to drive the first lower mold body (2) to move along the length direction of the guide mechanism, and the second driving mechanism is used to drive the second lower mold body (3) to move along the length direction of the guide mechanism; A controller (11) is signal-connected to the first drive mechanism and the second drive mechanism; The controller (11) is used to acquire the current downward displacement of the upper die and the current pressure value of the upper die acting on the plate in real time. Based on the current downward displacement and the current pressure value, a pressure-displacement response curve is constructed and the instantaneous stiffness change rate is calculated. When the instantaneous stiffness change rate is detected to continuously decrease relative to its stable average value in the elastic deformation stage and the cumulative decrease exceeds the preset threshold, the point is determined as the inflection point of plastic deformation. The die opening width convergence speed under the current working condition is dynamically calculated, and the first driving mechanism and the second driving mechanism are driven to move the first lower die body (2) and the second lower die body (3) along the length direction of the guide mechanism, so that the width of the die opening changes continuously and dynamically with the change of the downward displacement of the upper die during the entire downward stroke of the upper die.

2. The adjustable mold for bending and pressing aluminum single-panel according to claim 1, characterized in that: The controller (11) is equipped with a data acquisition module (1101) and a pressure detection module (1103). The data acquisition module (1101) is signal-connected to the first grating reader (12) installed on the upper mold, and is used to acquire the current downward displacement of the upper mold in real time; The pressure detection module (1103) is connected to the pressure sensor (13) installed on the upper mold and is used to detect the current pressure value of the upper mold acting on the plate.

3. The adjustable mold for bending and pressing aluminum single-panel according to claim 2, characterized in that: The controller (11) is also equipped with a dynamic calculation module (1107). The dynamic calculation module (1107) is connected to the data acquisition module (1101) and the pressure detection module (1103) respectively. It is used to construct the pressure-displacement response curve and calculate the instantaneous stiffness change rate based on the current downward displacement of the upper mold output by the data acquisition module (1101) and the current pressure value output by the pressure detection module (1103).

4. The adjustable mold for bending and pressing aluminum single-panel according to claim 3, characterized in that: The controller (11) is also equipped with an inflection point determination module (1108). The inflection point determination module (1108) is connected to the dynamic calculation module (1107) and is used to receive the instantaneous stiffness change rate output by the dynamic calculation module (1107). The inflection point determination module (1108) adopts the sliding window comparison method to compare the current instantaneous stiffness change rate with the previous values ​​in the window. When it is detected that the instantaneous stiffness change rate has continuously decreased relative to the stable average value of the elastic deformation stage and the cumulative decrease exceeds the preset threshold, the point is determined as the inflection point of plastic deformation.

5. The adjustable mold for bending and pressing aluminum single-panel according to claim 4, characterized in that: The controller (11) is also provided with a drive control module (1102). The drive control module (1102) is connected to the inflection point determination module (1108) and the first drive mechanism and the second drive mechanism respectively. The drive control module (1102) is used to receive the inflection point determination result output by the inflection point determination module (1108), and dynamically calculate the convergence speed of the mold opening width under the current working condition based on the inflection point determination result, and drive the first drive mechanism and the second drive mechanism to drive the first lower mold body (2) and the second lower mold body (3) to slide respectively.

6. The adjustable mold for bending and pressing aluminum single-panel according to claim 5, characterized in that: The controller (11) is also equipped with a displacement feedback module (1104) and a deviation correction module (1105). A second grating read head (8) is installed at the bottom of the first lower mold body (2) and the bottom of the second lower mold body (3). A grating ruler (7) corresponding to the second grating read head (8) is fixedly installed on the base (1). The displacement feedback module (1104) is electrically connected to the second grating read head (8) and is used to obtain the actual displacement of the first lower mold body (2) and the second lower mold body (3) in real time. The deviation correction module (1105) is signal-connected to the displacement feedback module (1104) and the drive control module (1102). When the drive control module (1102) drives the first lower mold body (2) and the second lower mold body (3) to slide towards or away from each other to change the mold opening width, the deviation module (1105) compares the actual displacement with the target displacement and calculates the deviation, and performs closed-loop correction based on the deviation. The deviation correction module (1105) does not work during the micro-vibration stage.

7. The adjustable mold for bending and pressing aluminum single-panel according to claim 6, characterized in that: The controller (11) is also provided with a micro-vibration control module (1106), which is signal-connected to the first drive mechanism and the second drive mechanism; After the upper mold is pressed down to the bottom and the current pressure value reaches the preset threshold, the micro-vibration control module (1106) drives the first drive mechanism and the second drive mechanism to drive the first lower mold body (2) and the second lower mold body (3) to reciprocate micro-vibration at the bottom pressure holding position with an amplitude of 0.1 mm to 0.3 mm and a frequency of 5 Hz to 20 Hz, which lasts for 10 to 60 seconds and then stops.

8. The adjustable mold for bending and pressing aluminum single-panel according to claim 1, characterized in that: Both the first drive mechanism and the second drive mechanism include a drive motor (4), a lead screw (5) and a bearing (6). The drive motor (4) and the bearing (6) are fixedly mounted on the base (1). One end of the lead screw (5) is fixedly connected to the shaft of the drive motor (4) through a coupling, and the other end of the lead screw (5) is rotatably connected to the bearing (6). The lead screw nut on the lead screw (5) in the first drive mechanism is fixedly connected to the bottom of the first lower mold body (2); The lead screw nut on the lead screw (5) in the second drive mechanism is fixedly connected to the bottom of the second lower mold body (3); The drive motor (4) is signal-connected to the controller (11).

9. The adjustable mold for bending and pressing aluminum single-panel according to claim 1, characterized in that: The guiding mechanism includes at least two parallel guide rails (9), which are fixedly mounted on the base (1). The bottom of the first lower mold body (2) and the bottom of the second lower mold body (3) are provided with guide grooves (10). The first lower mold body (2) and the second lower mold body (3) are slidably mounted on the guide rails (9) through the corresponding guide grooves (10).

10. A method for bending and arc-forming an aluminum single panel using the mold described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1: Place the aluminum single panel to be processed on the upper surface of the first lower mold body (2) and the second lower mold body (3); S2: The controller (11) controls the first drive mechanism and the second drive mechanism to drive the first lower mold body (2) and the second lower mold body (3) to slide back and forth, so that the width of the mold opening increases to a preset initial value; S3: Start the upper mold to move downward. The controller (11) obtains the current downward displacement of the upper mold and the current pressure value of the upper mold acting on the plate in real time. Based on the current downward displacement and the current pressure value, it constructs a pressure-displacement response curve and calculates the instantaneous stiffness change rate. When it is detected that the instantaneous stiffness change rate continuously decreases relative to its stable average value in the elastic deformation stage and the cumulative decrease exceeds the preset threshold, the point is determined as the inflection point of plastic deformation. The convergence speed of the mold opening width under the current working condition is dynamically calculated, and the first driving mechanism and the second driving mechanism drive the first lower mold body (2) and the second lower mold body (3) to slide towards each other, so that the mold opening width gradually shrinks. S4: After the upper mold is pressed down to the bottom and the current pressure value reaches the preset threshold, the controller (11) stops driving the first lower mold body (2) and the second lower mold body (3) to slide towards each other, and drives the first driving mechanism and the second driving mechanism to drive the first lower mold body (2) and the second lower mold body (3) to perform reciprocating micro-vibration at the bottom pressure holding position with an amplitude of 0.1 mm to 0.3 mm and a frequency of 5 Hz to 20 Hz, which lasts for 10 seconds to 60 seconds and then stops. S5: The controller (11) keeps the first drive mechanism and the second drive mechanism in the energized and locked state, so that the first lower mold body (2) and the second lower mold body (3) remain in the current position, the upper mold returns, and the formed workpiece is taken out.

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