Gradient iteration optimization method for automobile stamping part springback compensation

Abstract

The invention relates to the technical field of automobile part optimization, in particular to a gradient iterative optimization method for automobile stamping part springback compensation, which can realize real-time closed-loop control, and compresses deviation response time from a minute level of a traditional method to a millisecond level (less than 2ms) by integrating 800Hz high-frequency monitoring and PROFINET real-time communication technologies, so that the error response time is reduced, and the error response time is reduced. And on-line control over the whole process of punching, detecting and adjusting is achieved. And dynamic calibration of a forming force fluctuation threshold value is combined with self-adaptive adjustment of the friction coefficient, so that the production stability (CPK value) is improved from 1.0 to 1.67, the production stability is remarkably improved, and the service life of the mold is remarkably prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive part optimization, and particularly to a gradient iteration optimization method for springback compensation of automotive stamping parts. Background Art

[0002] Currently, the inner panel of an automotive door is an important component inside the vehicle. It is located inside the door and plays a role in support and protection. The inner panel of the door is usually made of metal (such as steel or aluminum alloy), and may include some plastic or composite material components for decoration or other functions. Its main functions include: providing necessary rigidity and strength for the door, being able to absorb part of the energy during a collision; protecting the safety of the passengers inside the vehicle; serving as an installation platform for various internal components (such as window control switches, audio systems, etc.).

[0003] Currently, the traditional manufacturing process of the inner panel of an automotive door in the existing technology mainly includes the following steps: 1. Design and die making: According to the product design drawings, the dies are designed and the corresponding dies are manufactured, including drawing dies, trimming dies, punching dies, etc.

[0004] 2. Raw material preparation: Select suitable sheet materials (such as cold-rolled steel sheets), and cut them into suitable sizes and shapes according to requirements.

[0005] 3. Stamping forming: Use a stamping machine to process the sheet material into the required shape through a series of processes, and these processes may include drawing, trimming, punching, flanging, shaping, etc.

[0006] Each of the above processes needs to be completed using specific dies to ensure the accuracy and quality of the parts.

[0007] 4. Inspection and trimming: Conduct quality inspection on the stamped parts to ensure that there are no problems such as cracks and wrinkles. Trim the parts if necessary, such as removing burrs or correcting deformations.

[0008] 5. Post-treatment: Including surface treatment (such as electroplating, painting), assembling other components (such as interior parts, sealing strips, etc.).

[0009] However, the following technical problems exist in the above existing technology: 1. The traditional offline detection has a long cycle and cannot capture the dynamic deviations during the stamping process in real time, resulting in slow response.

[0010] 2. In the traditional method, the core process parameters such as blank holding force and drawing speed are set based on experience and cannot accurately adapt to the fluctuations of material properties and the requirements of complex geometric features, resulting in a low first-pass qualification rate.

[0011] 3. The existing technology adopts a single parameter adjustment mode (such as only adjusting the clamping force or only changing the drawing speed), ignoring the coupling effect between process parameters. It often leads to a vicious cycle of adjusting the clamping force causing material rupture and reducing the speed causing wrinkles, and the compensation efficiency is low.

[0012] Therefore, a gradient iterative optimization method for springback compensation of automobile stamping parts is needed to solve the above problems. Summary of the invention

[0013] The present invention provides a gradient iterative optimization method for springback compensation of automotive stamping parts. The present invention can realize real-time closed-loop control. By integrating 800Hz high-frequency monitoring and PROFINET real-time communication technology, the deviation response time is compressed from the minute level of the traditional method to the millisecond level (<2ms), realizing the online control of the entire process of "stamping-detection-adjustment". The dynamic calibration of the forming force fluctuation threshold combined with the adaptive adjustment of the friction coefficient improves the production stability (CPK value) from 1.0 to 1.67, significantly improving the production stability and mold life.

[0014] The technical solution adopted by the present invention to solve the above technical problems is: A gradient iterative optimization method for springback compensation of automobile stamping parts comprises the following steps: S1. Set the initial blank holding force according to the yield strength of the stamping sheet; S2, set the initial drawing speed according to the ratio of the stamping plate thickness to the die corner radius; S3, determining the initial friction coefficient based on the anisotropy coefficient of the stamping sheet material; S4. Real-time monitoring of the contour deviation of automobile stamping parts after demoulding during the continuous stamping process. When the contour deviation exceeds ±0.8mm: If the deviation is symmetrically distributed, adjust the blank holder force in steps of 5kN / times. If the deviation is positive, increase the blank holder force; if the deviation is negative, reduce the blank holder force. If the deviation is asymmetrically distributed, adjust the drawing speed in steps of 2mm / s / times. S5. Detect the fluctuation range of stamping forming force. When the fluctuation range exceeds 15% of the set threshold, press 0.02 / step to adjust the friction coefficient; S6, execution parameter adjustment; S7. Perform three-dimensional profile scanning on the stamping parts and measure the springback amount of the characteristic surface and the fillet filling degree; S8. Based on the measurement results, adjust the blank holding force first and then optimize the drawing speed.

[0015] Further, setting the initial blank-holding force according to the yield strength of the stamping sheet in step S1 includes: when the yield strength of the stamping sheet ≤ 180 MPa, the blank-holding force is 120 kN - 150 kN; when 180 MPa < the yield strength of the stamping sheet ≤ 250 MPa, the blank-holding force is 150 kN - 180 kN; when the yield strength of the stamping sheet > 250 MPa, the blank-holding force is 180 kN - 220 kN.

[0016] Further, in step S2, when the ratio of the thickness of the stamping sheet to the radius of the die fillet ≤ 0.5, the initial drawing speed is 50 mm - 60 mm / s; when 0.5 < the ratio of the thickness of the stamping sheet to the radius of the die fillet ≤ 1, the initial drawing speed is 40 mm - 50 mm / s; when the ratio of the thickness of the stamping sheet to the radius of the die fillet > 1, the initial drawing speed is 30 mm - 40 mm / s.

[0017] Further, in step S3, when the anisotropy coefficient r of the stamping sheet material ≤ 1.2, the friction coefficient is 0.08 - 0.10; when 1.2 < the anisotropy coefficient r of the stamping sheet material ≤ 1.5, the friction coefficient is 0.10 - 0.12; when the anisotropy coefficient r of the stamping sheet material > 1.5, the friction coefficient is 0.12 - 0.15.

[0018] Further, the execution parameter adjustment in step S6 includes: S61. Fix the drawing speed and scan the blank-holding force range in 10 kN steps; S62. Optimize the matching value of the drawing speed in 5 mm / s steps; S63. Synchronously adjust the friction coefficient and the die clearance, and each adjustment amount does not exceed ±3% of the initial value.

[0019] Further, for the profile deviation monitoring in step S4, a laser displacement sensor array is used, 8 - 12 detection points are arranged along the periphery of the stamping die, the sampling frequency ≥ 500 Hz, and the deviation vector direction of each point is calculated in real time.

[0020] Further, in step S7, a blue light structured light measuring instrument is used to perform three-dimensional profile scanning on the stamping sheet, and the measurement accuracy ≤ 0.02 mm.

[0021] Further, the determination method for the fluctuation range of the stamping forming force in step S5 is: take the average value of the forming forces of 100 consecutive stampings, and the fluctuation amplitude threshold is set to ±10% of the average value.

[0022] Further, in step S1, when the thickness of the stamping sheet ≥ 2.0 mm, the initial blank-holding force is additionally increased by 10% - 15%; when the surface of the stamping sheet has a galvanized layer, the initial value of the friction coefficient is reduced by 0.02 - 0.03.

[0023] The advantages of the present invention are: 1. The present invention can realize real-time closed-loop control. By integrating 800Hz high-frequency monitoring and PROFINET real-time communication technology, the deviation response time is compressed from the minute level of the traditional method to the millisecond level (<2ms), realizing the online control of the entire process of "stamping-detection-adjustment". The dynamic calibration of the forming force fluctuation threshold combined with the adaptive adjustment of the friction coefficient improves the production stability (CPK value) from 1.0 to 1.67, significantly improving the production stability and mold life.

[0024] 2. Based on the quantitative grading of the yield strength, thickness / fillet ratio and anisotropy coefficient of the stamping material, the present invention establishes a scientific setting system for initial parameters. The first-piece qualified rate is increased from 65% of the traditional method to 92.3%, and a surface treatment correction mechanism is introduced (the galvanized layer reduces the friction coefficient by 0.02) to solve the problem of coating material parameter adaptation.

[0025] 3. The invention has created a three-stage parameter decoupling strategy: the first stage locks the speed to optimize the blank holder force, the second stage fixes the blank holder force to optimize the drawing speed matching value, and the third stage adjusts the friction and gap to solve the multi-parameter coupling problem. The embodiment shows that the springback amount is reduced by 66.7% after optimization (from 1.2mm→0.4mm). The laser array is used to analyze the deviation vector direction in real time, and the partition speed adjustment is implemented in a targeted manner (the right half mold speeds down 2mm / s, and the left half mold speeds up 2mm / s), which increases the efficiency of local deviation repair by 3 times. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Embodiment 1: The following describes the implementation process of the present invention in detail in combination with the stamping production process of a certain model of automobile door inner panel: Step S1: Initial blank holding force setting Step S1.1 Obtaining material parameters: DC04 cold-rolled steel plate with a plate thickness of 1.2 mm was selected, and the yield strength σ_s=210 MPa (satisfied with the range of 180 MPa<σ_s≤250 MPa) was measured by tensile test.

[0028] Step S1.2 Calculate the blank holder force. The initial blank holder force is selected as 165 kN, the median value of 150 kN-180 kN.

[0029] Step S1.3 Thickness Compensation: Since the sheet thickness 1.2mm < 2.0mm, no additional compensation mechanism is triggered. Step S1.4 Surface Treatment Correction: Since a galvanized layer (thickness 20μm) is detected on the sheet surface, the initial friction coefficient value is reduced by 0.02.

[0030] Step S2: Determination of Initial Drawing Speed Step S2.1 Die Parameter Measurement: The upper die fillet radius R = 8mm, the lower die fillet radius R = 6mm, and the maximum fillet radius R = 8mm is taken as the calculation reference.

[0031] Step S2.2 Thickness / Fillet Ratio Calculation: t / R = 1.2 / 8 = 0.15 (meeting the condition of ratio ≤ 0.5). Step S2.3 Speed Setting: The initial drawing speed is selected as 50 - 60mm / s, and the intermediate value 55mm / s is taken.

[0032] Step S2.4 Equipment Calibration: A high-precision displacement sensor (Heidenhain LS186M, resolution 0.001mm) is installed on the hydraulic press to ensure a speed control accuracy of ±0.5%.

[0033] Step S3: Initial Friction Coefficient Configuration Step S3.1 Anisotropy Test: The r value (plastic strain ratio) is measured by a unidirectional tensile test: r0 in the rolling direction = 1.35; r45 in the 45° direction = 1.28; r90 in the vertical direction = 1.42; Step S3.2 Average r Value Calculation: r = (r0 + 2r45 + r90) / 4 = 1.34 (meeting the range of 1.2 < r ≤ 1.5).

[0034] Step S3.3 Friction Coefficient Setting: The initial value 0.10 is selected and corrected to 0.08 due to the galvanized layer.

[0035] Step S3.4 Lubricant Selection: Water-based lubricant FD-520 (Matsumura Chemical, Japan) is used and controlled at 35 ± 2cP by a viscometer.

[0036] Step S4: Implementation of Dynamic Compensation Adjustment Step S4.1 Monitoring System Configuration: A laser displacement sensor array (Keyence LK-H020, 12 measuring points arranged in a ring), the sampling frequency is set to 800Hz, and data transmission uses PROFINET real-time industrial Ethernet with a delay < 2ms.

[0037] Step S4.2 First-piece Inspection Data:

[0038] (where: * indicates exceeding the threshold of ±0.8 mm) Step S4.3: Deviation pattern analysis: Measuring points 2, 5, and 8 show positive deviations (exceeding the tolerance by 0.84 mm); measuring points 3, 6, and 9 show negative deviations (-0.76 mm); the deviation distribution shows an asymmetric characteristic (the deviation amount in the right half > the left half).

[0039] Step S4.4: Execution of adjustment strategy Start adjusting the drawing speed: Reduce the speed of the right half die area by 2 mm / s to 53 mm / s, and increase the speed of the left half die area by 2 mm / s to 57 mm / s. After adjustment, detect: The maximum deviation is reduced to 0.52 mm.

[0040] Step S5: Control of forming force fluctuation Step S5.1; Data acquisition: Use a Kistler 9232A piezoelectric force sensor to continuously collect 100 stamping forming force data (sample frequency 1 kHz).

[0041] Step S5.2: Calculation of reference value: Average forming force F avg = 1780 kN, fluctuation threshold ΔF = ±178 kN (10% of F avg )

[0042] Step S5.3: Handling of abnormal working conditions: At the 123rd stamping, F = 1620 kN (lower than the lower limit value of 1602 kN) was recorded, triggering the adjustment of the friction coefficient. The current friction coefficient μ = 0.08 → increased to 0.10. After adjustment, the fluctuation amplitude recovered to ±8.5%.

[0043] Step S6: Coordinated optimization of parameters Step S6.1: Blank holding force scanning: Fix the drawing speed at 55 mm / s, and the blank holding force adjustment sequence: 155 kN → 165 kN → 175 kN → 185 kN.

[0044] Quality index comparison is as follows:

[0045] Select 175 kN as the optimal blank holding force.

[0046] Step S6.2: Speed optimization: Lock the blank holding force at 175 kN, and the speed adjustment gradient: 50 mm / s → 53 mm / s → 56 mm / s → 59 mm / s.

[0047] Forming quality monitoring table is as follows:

[0048] (where *exceeds the 0.3mm threshold, **triggers an alarm) 53mm / s is selected as the optimal speed.

[0049] Step S6.3 Synchronous fine-tuning: Die clearance compensation: Add a 0.08mm shim in the area corresponding to measuring point 2, and adjust the friction coefficient to 0.09.

[0050] Total adjustment amount: ΔBinder force = +6.06% (150 → 175kN) ΔSpeed = -3.6% (55 → 53mm / s) ΔFriction coefficient = +12.5% (0.08 → 0.09) Step S7: 3D profile verification: Step S7.1 Measuring equipment: Use a GOM ATOS Q blue light scanner (measurement accuracy 0.018mm), set the scanning resolution to 0.1mm, and the single-frame scanning time < 20s.

[0051] Step S7.2 Feature detection: The theoretical height of the sheet is 15.0mm → measured 14.96mm (springback amount 0.04mm).

[0052] Step S8: According to the measurement results, first adjust the binder force and then optimize the drawing speed. The parameter optimization record is:

[0053] After optimization by this method, the following technical indicators are achieved: The springback amount is reduced from the initial 1.2mm to 0.4mm (a 66.7% reduction), the fillet filling degree is increased from 91% to 97.5%, the single-piece forming time is shortened from 8.2s to 7.5s, and the die life is increased from 300,000 times to 420,000 times.

[0054] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: They can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gradient iterative optimization method for springback compensation of automobile stamping parts, characterized in that: Including Next steps: S1. Set the initial blank holding force according to the yield strength of the stamping sheet; S2, set the initial drawing speed according to the ratio of the stamping plate thickness to the die corner radius; S3, determining the initial friction coefficient based on the anisotropy coefficient of the stamping sheet material; S4. Real-time monitoring of the contour deviation of automobile stamping parts after demoulding during the continuous stamping process. When the contour deviation exceeds ±0.8mm: If the deviation is symmetrically distributed, adjust the blank holder force in steps of 5kN / times. If the deviation is positive, increase the blank holder force; if the deviation is negative, reduce the blank holder force. If the deviation is asymmetrically distributed, adjust the drawing speed in steps of 2mm / s / times. S5. Detect the fluctuation range of stamping forming force. When the fluctuation range exceeds 15% of the set threshold, press 0.02 / step to adjust the friction coefficient; S6, execution parameter adjustment; S7. Perform three-dimensional profile scanning on the stamping parts and measure the springback amount of the characteristic surface and the fillet filling degree; S8. Based on the measurement results, adjust the blank holding force first and then optimize the drawing speed.

2. The gradient iterative optimization method for springback compensation of automobile stamping parts according to claim 1 is characterized in that: In the step S1, the initial blank holding force is set according to the yield strength of the stamping part sheet material, including: when the yield strength of the stamping part sheet material is ≤180MPa, the blank holding force is 120kN-150kN; when 180MPa<the yield strength of the stamping part sheet material≤250MPa, the blank holding force is 150kN-180kN; when the yield strength of the stamping part sheet material is>250MPa, the blank holding force is 180kN-220kN.

3. The gradient iterative optimization method for springback compensation of automobile stamping parts according to claim 1 is characterized in that: In the step S2, when the ratio of the stamping part plate thickness to the mold corner radius is ≤0.5, the initial drawing speed is 50mm-60mm / s, when 0.5<the ratio of the stamping part plate thickness to the mold corner radius is ≤1, the initial drawing speed is 40mm-50mm / s, and when the ratio of the stamping part plate thickness to the mold corner radius is >1, the initial drawing speed is 30mm-40mm / s.

4. A gradient iterative optimization method for springback compensation of automobile stamping parts according to claim 1 The method is characterized in that In the step S3, when the anisotropy coefficient of the stamping sheet material r≤1.2, the friction coefficient is 0.08-0.10; when 1.2<the anisotropy coefficient of the stamping sheet material r≤1.5, the friction coefficient is 0.10-0.12; when the anisotropy coefficient of the stamping sheet material r>1.5, the friction coefficient is 0.12-0.

15.

5. The gradient iterative optimization method for springback compensation of automobile stamping parts according to claim 1 is characterized in that: The parameter adjustment performed in step S6 includes: S61, fixed drawing speed, scanning the blank holding force range with a step length of 10 kN; S62, optimize the drawing speed matching value with a step size of 5 mm / s; S63. Adjust the friction coefficient and mold gap synchronously, and the adjustment amount each time shall not exceed ±3% of the initial value.

6. The gradient iterative optimization method for springback compensation of automobile stamping parts according to claim 1 is characterized in that: The contour deviation monitoring in step S4 adopts a laser displacement sensor array, 8-12 detection points are arranged along the periphery of the stamping die, the sampling frequency is ≥500Hz, and the deviation vector direction of each point is calculated in real time.

7. The gradient iterative optimization method for springback compensation of automobile stamping parts according to claim 1 is characterized in that: In the step S7, a blue light surface structured light measuring instrument is used to perform a three-dimensional profile scan on the stamping part sheet, and the measurement accuracy is ≤0.02mm.

8. The gradient iterative optimization method for springback compensation of automobile stamping parts according to claim 1 is characterized in that: The method for determining the fluctuation range of the stamping forming force in step S5 is: taking the average value of the forming force of 100 consecutive stampings, and setting the fluctuation amplitude threshold to ±10% of the average value.

9. The gradient iterative optimization method for springback compensation of automobile stamping parts according to claim 1, characterized in that: In the step S1, when the thickness of the stamping sheet is ≥2.0 mm, the initial blank holding force is additionally increased by 10%-15%; when there is a galvanized layer on the surface of the stamping sheet, the initial value of the friction coefficient is reduced by 0.02-0.03.

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