A process compensation method for suppressing the springback of semi-steel cable forming

Abstract

The present invention provides a process compensation method for suppressing the springback of semi-steel cable forming, including: Step 1, conduct a cable forming test according to the designed angle. After forming, measure the actual forming angle of the specimen and calculate the springback angle; Step 2, use the polynomial fitting method based on the least square method and the numerical fitting method based on linear interpolation to fit the angle data, and perform residual analysis through Python to preferentially determine the fitting method; Step 3, analyze the reasons for the deviation of the forming state caused by angle compensation, and propose a straight-line segment length correction strategy to solve the compensation increment problem; Step 4, use Python for data processing, adopt the compensation strategy combined with the correction strategy to form an automatic forming parameter optimization program to complete the data compensation work. The present invention reduces the forming angle deviation of the semi-steel cable, improves the forming accuracy and efficiency of the semi-steel cable, and can install the cable according to the three-dimensional wiring plan.

Description

Technical Field

[0001] The present invention belongs to the technical field of the conversion from three-dimensional wiring design to manufacturing and assembly of semi-rigid cables, and particularly relates to a process compensation method for suppressing the springback of semi-rigid cable forming. Background Art

[0002] According to the three-dimensional wiring plan, the process of forming a semi-rigid coaxial cable using a semi-rigid coaxial cable forming machine and auxiliary tooling in cooperation with automated production equipment is as follows: The cable is cut according to the total length of the three-dimensional wiring, the welding part is deoxidized and polished, and then tinning operation is carried out. On this basis, automated stripping is carried out. The cable after stripping is not removed from the stripping part and directly enters the semi-rigid coaxial cable forming machine for automated forming. After forming, the stripping part is removed, and the final welding operation is carried out.

[0003] The use of the forming machine has greatly improved the forming efficiency and production efficiency. When the semi-rigid coaxial cable is bent, the bending head applies a moment M to the semi-rigid coaxial cable, and the cable deforms under its action. Before the internal stress of the coaxial cable reaches the yield strength of the material, it undergoes elastic deformation, and the deformation characteristics follow a linear distribution in the form of Hooke's law. During the bending process of the forming machine, when the load exceeds the yield limit of the material, the coaxial cable undergoes plastic deformation, but during this process, there is still some elastic deformation. When unloading in the elastic deformation region, the deformation of the coaxial cable will start to recover until the internal stress of the cable disappears. Therefore, when the bending is completed, during the unloading process, the elastic deformation part will undergo corresponding springback to release the internal stress.

[0004] The release of internal stress is the main reason for the springback of the cable. This phenomenon causes a deviation between the actual forming of the cable and the three-dimensional wiring plan, greatly reducing the forming accuracy of the cable, thus seriously affecting the conversion efficiency from the three-dimensional design of the cable to manufacturing. And during the formal assembly process of the semi-rigid cable, it is difficult for the operator to install the formed cable according to the three-dimensional wiring plan. The operator still needs to fine-tune the forming state of the cable according to the physical object, increasing the process of fine-tuning the forming state of the cable, reducing the production efficiency. Moreover, when the cable is welded, it is relatively difficult to adjust the forming of some short cables, and the applied forming force is likely to directly affect the solder joints, which may affect the reliability and stability of the operation of electronic equipment.

[0005] Since the coaxial cable is a composite material, its springback characteristics after bending belong to the category of non-linear analysis, and it is difficult to establish a springback compensation model through simulation analysis. Therefore, it is difficult to establish a prediction model through simulation analysis to predict the springback compensation value. Currently, there is still a lack of an effective method to suppress the springback of cable forming and reduce the forming deviation of semi-rigid cables. Therefore, it is necessary to explore a feasible process compensation strategy to further improve the forming accuracy and efficiency of coaxial cables. Summary of the Invention

[0006] The object of the present invention is to provide a process compensation method for suppressing the springback of semi-steel cable forming, so as to effectively suppress the springback of semi-steel cable forming and make up for the forming deviation caused by the existing process.

[0007] The technical solution for achieving the object of the present invention is as follows:

[0008] A process compensation method for suppressing the springback of semi-steel cable forming, comprising the following steps:

[0009] Step 1, carry out cable forming tests according to the designed angle. After the forming is completed, measure the actual forming angle of the specimen and calculate the springback angle.

[0010] Step 2, use different fitting methods to fit the forming angle data, perform residual analysis through Python, and preferably determine the fitting method to be used to obtain the springback equation.

[0011] Step 3, analyze the reasons for the deviation of the forming state caused by angle compensation, and calculate the length increment generated by the bending angle according to the arc length formula.

[0012] Step 4, input the set bending angle into the springback equation to obtain the cable compensation angle, and substitute the cable compensation angle into the arc length formula to calculate the compensation increment generated by multiple bends. Subtract the compensation increment from the total length to determine the compensated cable length.

[0013] Compared with the prior art, the present invention has the following remarkable advantages:

[0014] (1) When the semi-steel cable is formed, the internal stress of the elastic deformation part is released, resulting in the springback of the cable forming. At present, there is no effective method or strategy to suppress the springback of cable forming. Starting from the process strategy of angle compensation, the present invention proposes to adopt an active reverse process compensation strategy to suppress the springback of cable forming to make up for the deficiencies of the existing technology.

[0015] (2) The angle compensation strategy of the present invention takes into account that the increment generated by angle compensation will cause deviation of the forming state, and further analyzes that the forming machine program should also adopt a straight-line segment length correction strategy to ensure that the formed cable conforms to the three-dimensional output state.

[0016] (3) The angle compensation strategy of the present invention can accurately solve the compensation angle according to the springback equation and interpolation function of the cable, so as to minimize the forming deviation of the cable to the greatest extent. Description of the Drawings

[0017] Figure 1 It is a flow chart of the design idea for suppressing the springback of cable forming in the present invention.

[0018] Figure 2AThis is the actual angle polynomial fitting diagram based on the least squares method.

[0019] Figure 2B This is the springback angle polynomial fitting diagram based on the least squares method.

[0020] Figure 3A This is a numerical fitting diagram of the actual angle based on linear interpolation.

[0021] Figure 3B This is a numerical fitting diagram of the rebound angle based on linear interpolation.

[0022] Figure 4 Schematic diagram of the forming state change after angle compensation.

[0023] Figure 5 Schematic diagram of the correction of the straight line segment length to compensate for the angle.

[0024] Figure 6 Flowchart for automated molding parameter optimization.

[0025] Figure 7 This is a comparison chart of total manufacturing time. DETAILED DESCRIPTION

[0026] In order to further illustrate the technical scheme and technical principle of the present invention, the present invention is specifically introduced below in combination with specific embodiments and drawings.

[0027] The present invention adopts the following technical scheme to solve the problem of cable forming springback: carry out cable forming tests, respectively adopt polynomial fitting method and numerical fitting method to fit data, obtain semi-steel cable springback equation and linear interpolation function, select the best fitting method to be used, combine the numerical fitting method with the length correction strategy to form an automated forming parameter process program based on Python, complete the data compensation work, and carry out experiments to verify that the process compensation method can improve the accuracy and efficiency of forming.

[0028] Combination Figure 1 The process compensation method for suppressing cable forming springback specifically comprises the following steps:

[0029] Step 1. Carry out cable forming test. Use a forming machine to bend the cable forming specimen according to the designed angle. After forming, use a two-dimensional imaging instrument to measure the angle of the specimen and calculate the rebound angle.

[0030] Set the molding machine parameters, unload the semi-steel cable and install it in the molding machine fixture position. According to the commonly used molding angle range, the design bending angle is shown in Table 1. The molding machine is used to bend the cable molding specimens according to the designed angle, and a total of 15 cable molding specimens are prepared.

[0031] Table 1

[0032] Test number Set bending angle Test number Set bending angle Test number Set bending angle 1 10° 6 60° 11 110° 2 20° 7 70° 12 120° 3 30° 8 80° 13 130° 4 40° 9 90° 14 140° 5 50° 10 100° 15 150°

[0033] After the forming is completed, a two-dimensional imaging instrument is used to measure the angles of the specimens, and the actual forming angle data are obtained as shown in Table 2. Fourteen sample points are inserted at intervals among the original 15 sample points, and the bending forming and angle measurement steps are repeated.

[0034] Table 2

[0035] Test number 1 2 3 4 5 Designed angle 10° 20° 30° 40° 50° Actual angle 2.42° 13.78° 24.05° 35.75° 45.37° Springback angle 7.58° 6.22° 5.95° 4.25° 4.63° Test number 6 7 8 9 10 Designed angle 60° 70° 80° 90° 100° Actual angle 55.95° 65.55° 75.33° 84.25° 94.9° Springback angle 4.05° 4.45° 4.67° 5.75° 5.1° Test number 11 12 13 14 15 Designed angle 110° 120° 130° 140° 150° Actual angle 104.9° 115° 125.2° 134.5° 144.8° Springback angle 5.1° 5° 4.8° 5.5° 5.2°

[0036] Step 2. Use the polynomial fitting method based on the least squares method and the numerical fitting method based on linear interpolation to fit the angle data, perform residual analysis through Python, and then preferentially determine the fitting method to be used.

[0037] Use the polynomial fitting method based on the least squares method to fit the actual angle and springback angle data of 15 sample points and 29 sample points as Figure 2A 、 Figure 2B shown, Figure 2A 、 Figure 2B showing that the actual angle and the designed angle present an approximately linear relationship, while the springback angle and the input angle present a complex non-linear relationship. When the input angle is less than 60°, as the input angle increases, the springback angle decreases significantly. When the input angle is greater than 60°, as the input angle increases, the springback angle increases slowly.

[0038] Calculate the residuals through Python. When fitting with a fifth-order equation, the fitting residuals of the actual angles of 15 sample points are 1.53, the fitting residuals of the springback angles are 1.56, the fitting residuals of the actual angles of 29 sample points are 4.67, and the fitting residuals of the springback angles are 3.74. Further calculate the fitting of the sixth-order equation with the same number of points. The fitting residuals of the actual angles are 4.29, and the fitting residuals of the springback angles are 3.28.

[0039] Figure 2 shows that under the condition of constant order of polynomial fitting, its optimization degree is limited. The increase in the number of sample points will lead to an increase in the residual values of polynomial fitting. Therefore, the increase in the number of sample points does not significantly increase the optimization ability of polynomial fitting, and the order of the fitting curve is the key parameter for fitting.

[0040] Analyze using the polynomial approximation theory. When the order is too high, the fitting parameters are prone to the Runge phenomenon, resulting in oscillations of the fitting values and a decrease in the calculation convergence degree. Therefore, from the perspective of non-linear equations, use a fifth-order polynomial equation to fit the springback angle data, and the springback equation is as shown in Equation (1).

[0041] y = 1.315×10 -9 x 5-4.712×10 -7 x 4 +5.107×10 -5 x 3 -0.0008125x 2 -0.1262x + 8.891(1)

[0042] In Equation (1), y represents the cable springback angle, and x represents the input angle, that is, the set bending angle.

[0043] The actual angle and springback angle data of 15 sample points and 29 sample points are fitted by using the numerical fitting method based on linear interpolation as Figure 3A 、 Figure 3B shown, Figure 3A 、 Figure 3B It shows that the linear interpolation fitting effect of 15 sample points is better than that of 29 sample points. Based on the characteristics of linear interpolation, the data of 29 sample points are substituted into the fitting function of 15 sample points for residual analysis. The residual value of the actual angle linear interpolation fitting is 2.07, and the residual value of the springback angle linear interpolation is 2.40.

[0044] Residual numerical analysis shows that when calculating the residuals of 15 sample points and 29 sample points data, the residual value of the numerical fitting method is smaller than that of the polynomial fitting method. Therefore, the numerical fitting method based on linear interpolation should be used as the fitting method to compensate the program.

[0045] The springback function of the semi-steel cable obtained by the numerical fitting method based on linear interpolation is a piecewise function, and the linear interpolation function is established as shown in Equation (2).

[0046]

[0047] In Equation (2), 2 ≤ n ≤ 13, n represents the nth test number, y(x) represents the cable springback angle, x represents the input angle, that is, the set bending angle, x1 - x 15 represents the input angle, and y1 - y 15 represents the corresponding springback angle.

[0048] Step 3. Analyze the reasons for the deviation of the forming state caused by angle compensation, and propose a straight-line segment length correction strategy to solve the compensation increment problem.

[0049] When using the linear interpolation method to compensate the angle, assume that the cable needs to be bent N times during forming, that is, bent at N positions on the cable, corresponding to N times of angle compensation. The length of the corresponding bending section increases with the increase of the compensation angle, and the increased length is the arc length corresponding to the compensation angle. The increment ΔL generated by compensating the i-th bending angle can be calculated according to the arc length formula (3) i .

[0050]

[0051] In Equation (3), θ represents the compensation angle, and r represents the bending radius. Through Equation (3), the total increment of the cable compensation angle can be calculated as At this time, the increment generated by the compensation angle will cause an increase in the program calculation length of the cable, and the increase in the total length will in turn cause the rearward movement of the equipment fixture. However, the actual off-line length does not change, which will ultimately lead to an error in the cable forming position. The schematic diagram of the change in the forming state after angle compensation is as Figure 4 shown.

[0052] Figure 4 The total increment generated by the angle compensation shown above will cause the cable to shift to the right. To ensure that the actual forming result of the cable meets the three-dimensional design requirements, the length increment generated by the compensation angle should be deducted by an equal length from the straight line area to ensure that the actual compensation angle only affects the bending and the total length does not change, and the forming machine fixture does not displace. The schematic diagram of the compensation angle combined with the straight line segment length correction is as Figure 5 shown.

[0053] In summary, only by combining the angle compensation method and the straight line segment length correction strategy can the state where the automatically formed cable matches the three-dimensional output be finally achieved.

[0054] Step 4. The process of using the compensation method combined with the correction strategy to perform data processing through Python to form an optimized program for automatic forming parameters is as Figure 6 shown, and the data compensation work is completed using this method.

[0055] Figure 6 The process of the optimized program for automatic forming parameters shown above is to first read the bending report file through Python. After determining the line data, the data that does not participate in the compensation at the header and footer are stored in a preset list according to the characteristics of the bending report, and the forming data rows are split and loaded into the list. At this time, the bending angle information can be locked through the corresponding positions in the list.

[0056] Then, the linear interpolation function is used for bending compensation. The linear interpolation function represents the relationship between the actual angle and the input angle. In the actual application process, only the output value of the bending report needs to be input as the actual value into the linear interpolation function to solve the corresponding compensation input parameters.

[0057] Then, the straight line length correction strategy is used to correct the straight line according to the compensation angle. The straight line area in the program is corrected according to the increment generated by the compensation angle calculation. The corrected data is stored in a temporary variable. After the straight line compensation is completed, the compensation data replaces the old value (original length and angle data) in the original line data list to form a new line data, and the line data is added to the preset list. Finally, the preset list content is output to the document established by the script, and the data compensation work is finally completed.

[0058] Step 5. Conduct experiments to verify the effectiveness of the process compensation method in improving molding accuracy and molding efficiency.

[0059] A Python random function was used to select 10 integer points between 5° and 100° as the bending test angle. A compensation program was used to compensate the angle. After the cable was formed, a two-dimensional imaging instrument was used to measure the angle of the sample. The test data are shown in Table 3.

[0060] Table 3

[0061]

[0062]

[0063] Table 3 shows that the average cable forming deviation before compensation is 5.22°. Table 3 shows that after correction by the compensation program, the deviation between the actual bending angle and the test angle is reduced to within 1°, and the average deviation is 0.52°. The compensation strategy reduces the forming offset caused by springback by 90.03%, thereby basically realizing the installation of cables according to the three-dimensional wiring plan.

[0064] In order to verify the improvement of manufacturing efficiency by forming compensation, 25 cables were prepared in three ways: direct machine forming after compensation, manual correction after forming without compensation, and manual forming. The manufacturing efficiency only refers to the cable forming time, excluding other operation steps such as welding and stripping. The total manufacturing time comparison chart is as follows Figure 7 shown.

[0065] Figure 7 The results show that the secondary manual correction after the automatic molding is completed is 35.29% more efficient than the manual production mode. After further using the compensation program, the efficiency is increased by 72.63% compared with the manual production mode and 57.70% compared with the non-compensation mode (manual correction after molding), indicating that the molding efficiency of the cable is significantly improved after compensation.

[0066] For each of the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should be aware that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in a different order or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0067] Each embodiment in this specification is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other.

[0068] The above has introduced in detail a process compensation strategy for suppressing the springback of semi-steel cable forming. Specific embodiments are used herein to elaborate on the basic principles, main features, and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention.

[0069] At the same time, those skilled in the art should be clear that the present invention is not limited by the above embodiments. The above embodiments and the description in the specification only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements. The scope of protection required by the present invention is defined by the appended claims, the specification, and their equivalents.

Claims

1. A process compensation method for suppressing the springback of semi-steel cable forming, characterized in that The following steps are involved: Step 1: Carry out the cable forming test according to the designed angle, measure the actual forming angle of the sample after forming, and calculate the springback angle; Step 2, different fitting methods are used to fit the forming angle data, residual analysis is performed through Python, the fitting method is selected to obtain the springback equation; Step 3: Analyze the reasons why the angle compensation causes the deviation of the forming state, and calculate the length increment caused by the bending angle according to the arc length formula; Step 4: Input the actual angle value into the springback equation to obtain the cable springback angle, and use the cable springback angle as the compensation angle for bending to enter the arc length formula to calculate the length increment caused by multiple bends; The total length increment is deducted from the straight area of the cable to obtain the compensated cable length.

2. The process compensation method for suppressing the springback of semi-steel cable forming according to claim 1, wherein Step 1 specifically includes the following steps: 1a) Design the bending angle according to the commonly used forming angle range and carry out cable forming tests; 1b) Set the molding machine parameters, unload the semi-steel cable and install it to the molding machine fixture position, and use the molding machine to bend the cable molding specimen according to the designed angle; 1c) After forming, use a two-dimensional imaging instrument to measure the angle of the sample, obtain the actual forming angle data, and calculate the rebound angle.

3. The process compensation method for suppressing the springback of semi-steel cable forming according to claim 1, characterized in that In step 2, the corresponding rebound equation is finally obtained by using a numerical fitting method based on linear interpolation.

4. The process compensation method for suppressing the springback of semi-steel cable forming according to claim 1, wherein, It also includes correcting the straight line area in the bending program based on the calculated total length increment, storing the corrected data in temporary variables, and when the straight line segment compensation is completed, the compensated data replaces the original length and angle data to form new row data, and the corrected result is output after the data is combined.

5. The process compensation method for suppressing the springback of semi-steel cable forming according to claim 1, characterized in that, It also includes step 5, conducting experiments to verify the effectiveness of the process compensation method in improving molding accuracy and molding efficiency: 5a) Use Python random function to select integer points as bending test angles, and use compensation program to compensate the angles; 5b) After the cable is formed, use a two-dimensional imaging instrument to measure the angle of the sample to obtain the actual forming angle data and verify the forming accuracy of the compensation method; 5c) Three methods were used: direct machine forming after compensation, manual correction after forming without compensation, and manual forming. An equal number of cables were prepared in each method. The forming efficiency of the machine after compensation was verified by referring only to the cable forming time.

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