Rebound compensation control method based on incremental forming of tailor-welded blanks with different thicknesses

Abstract

The invention discloses a springback compensation control method based on differential-thickness tailor-welded blank incremental forming, and belongs to the technical field of plate incremental forming. The method specifically comprises the steps that an incremental forming three-dimensional mathematical model of the differential-thickness tailor-welded blank conical part is constructed; based on the three-dimensional mathematical model, the obtained springback curve of the different-thickness tailor-welded blank conical part is compared with the theoretical contour line to obtain the springback difference value of the thick side and the thin side of the different-thickness tailor-welded blank conical part; further, the feeding amount of the side, with the large springback amount, of the different-thickness tailor-welded blank conical part is obtained; the method comprises the following steps: segmenting and dividing a different-thickness tailor-welded blank conical part on the basis of the forming depth of the different-thickness tailor-welded blank conical part, respectively applying corresponding feed amounts to the thick side and the thin side of each segment of the divided different-thickness tailor-welded blank conical part for processing, and after the thick side of each segment of the different-thickness tailor-welded blank conical part is processed, carrying out last-step reverse compensation processing on the thin side. And machining of each section of the different-thickness tailor-welded blank conical part is completed, and machining is conducted circularly in the machining mode till machining of the different-thickness tailor-welded blank conical part is completed. The forming precision and quality of the machined part are effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of sheet metal incremental forming, in particular to a springback compensation control method based on incremental forming of tailor-welded plates with differential thickness. Background Art

[0002] Incremental forming is an advanced manufacturing process that uses rapid prototyping technology to discretize complex three-dimensional models into several layers in the height direction, control the forming tool head to process layer by layer, and finally obtain the desired part shape. Compared with traditional sheet metal forming processes, this technology has smaller forming force and higher flexibility, does not require molds, and can realize the processing of complex products, but it is prone to large springback during the forming process, which directly affects the quality and accuracy of the formed parts. In response to this problem, Zhang Xu et al. studied the influence of different parameters on the quality of sheet metal incremental forming and analyzed the compensation method for springback defects; Wen Huaixing et al. used the orthogonal experimental method to analyze the influence of processing parameters on the springback amount and proposed the use of negative compensation to reduce springback; Du Zhihao et al. studied a mechanism based on magnetic vibration to reduce part springback, etc.

[0003] Tailor-welded blanks with differential thickness refer to two or more metal sheets of different thicknesses connected into a sheet through welding according to the overall process performance requirements of the formed part. It is an important technical path to achieve product lightweighting. Tailor-welded blanks with differential thickness can effectively achieve lightweighting while ensuring the structural strength of the formed part, and have been widely used in the automotive, aerospace and other fields. For progressively formed parts with large changes in forming angles, a reasonable design of tailor-welded blanks with differential thickness can achieve uniform wall thickness of the formed part according to the cosine theorem of wall thickness variation in the processing area. However, during the progressive forming process of tailor-welded blanks with differential thickness, there is a large difference in the springback on both sides of the sheet metal, which leads to a significant decrease in the dimensional accuracy of the formed part, directly affecting the product quality. In response to this phenomenon, Guo Qiuhua et al. used the BP neural network method to establish a springback prediction model for the springback problem of conical parts, and concluded that the greater the downward pressure, the smaller the springback; Wang Yongqiang et al. studied the incremental forming of 5052 and 6061 dissimilar aluminum alloy tailor-welded plates, and found that the accumulation of bottom material, the contact mode between the sheet and the tool head, and the quality of the weld would affect the accuracy of the formed parts. It was proposed that the weld would cause changes in the mechanical properties and thickness of the forming area, thereby affecting the forming accuracy and springback effect; An Zhiguo, Zhao Xiumin, Qin Qin, Jiang Zhihong et al. reduced the springback by controlling parameters such as the forming height and feed rate, but they all studied the overall springback control of the formed parts, and did not improve the springback error in a targeted manner according to the characteristics of the thin and thick plate sides. Summary of the invention

[0004] The purpose of the present invention is to provide a springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness, which adopts differential feed rates on the thin and thick sides of the tailor-welded blanks, and performs reasonable feed rate compensation on the side with larger springback based on the original standard feed rate, so as to improve the overall springback of the formed parts and improve the forming accuracy of the parts. The present invention is achieved through the following technical solutions.

[0005] The present invention provides a springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness, comprising:

[0006] Construct a three-dimensional mathematical model of a tapered tailor-welded blank with differential thickness;

[0007] Based on the three-dimensional mathematical model, a springback curve of a tapered part of a tailor-welded blank with differential thickness is obtained, and based on a comparison between the springback curve of the tapered part of a tailor-welded blank with differential thickness and a theoretical contour line, a springback difference between the thick and thin sides of the tapered part of the tailor-welded blank with differential thickness is obtained;

[0008] Based on the springback difference and the tool head reference feed amount, the feed amount on the side of the tapered part of the tailor-welded blank with a large springback amount is obtained;

[0009] The tapered part of the tailor-made welded blank with differential thickness is divided into sections based on the forming depth of the tapered part of the tailor-made welded blank with differential thickness, and the thick and thin sides of each tapered part of the tailor-made welded blank with differential thickness are respectively given corresponding feed amounts for processing. After the thick side processing of each tapered part of the tailor-made welded blank with differential thickness is completed, the thin side is subjected to the last step of counter-compensation processing to complete the processing of each tapered part of the tailor-made welded blank with differential thickness, and this processing method is cyclically processed until the processing of the tapered part of the tailor-made welded blank with differential thickness is completed.

[0010] In practical applications, due to the large difference in springback on both sides of the sheet during the progressive forming process, the dimensional accuracy of the formed part will be significantly reduced, which will directly affect the product quality. The present invention fully considers the factor that there is a large difference in springback on both sides of the sheet, and improves the springback error in a targeted manner according to the characteristics of the thin and thin sides of the differential thickness plate. Since the springback of the thin measurement is large, the present invention maintains the standard feed rate for the thick side, and performs reasonable feed rate compensation for the thin measurement based on the original standard feed rate. In the process of processing the differential thickness tailored welded plates, they are first divided into sections according to their three-dimensional model depth, and then each section of the differential thickness tailored welded plate is processed in sections. In addition, the present invention also processes the differential thickness tailored welded plates by segmented processing, which can overcome the problem of deformation of the formed parts caused by excessive difference in tool tracks on both sides of the differential thickness tailored welded plates.

[0011] Optionally, the springback difference between the thick and thin sides of the tapered part of the tailor-welded blank based on the comparison between the springback curve of the tapered part of the tailor-welded blank with a difference in thickness and the theoretical contour line is obtained, including:

[0012] At the middle position of the deformation area of ​​the tapered part of the differential thickness welded plate, uniformly select points, of which ≥5, extract the springback value corresponding to each point on the thin side as , the springback amount corresponding to each point on the thick side is , calculate the mean springback of the thick side And the average value of thin springback , based on the mean springback value of the thick side and the mean value of the thin-film springback Obtain the springback difference between the thick and thin sides of the tapered tailor-welded blank Wherein, the deformation area of ​​the tapered part of the tailor-welded blank with differential thickness is the area between the springback curve and the theoretical contour line.

[0013] Optionally, the calculation of the mean springback value of the thick side Calculated by the following formula:

[0014]

[0015] The calculation of the mean springback value of the thick side Calculated by the following formula:

[0016]

[0017] The springback difference between the thick and thin sides of the tapered part of the differential thickness tailor-welded blank Calculated by the following formula:

[0018] .

[0019] Optionally, the feed amount of the side with a larger springback amount of the tapered part of the tailor-welded blank with different thickness is obtained based on the springback difference and the reference feed amount of the tool head, and is calculated by the following formula:

[0020] ,

[0021] In the formula, is the tool head base feed, The feed rate is the feed rate on the side where the springback of the tapered part of the tailor-welded blank with different thickness is large. In the present invention, the springback of the tapered part of the tailor-welded blank with different thickness is large on the thin side.

[0022] Optionally, the step of providing corresponding feed amounts to the thick and thin sides of each segment of the tapered tailor-welded blank after division for processing includes: providing a tool head reference feed amount to the thick side of each segment of the tapered tailor-welded blank after division Processing is performed by feeding the thin side of each section of the tapered tailor-welded blank with a feed amount of For processing.

[0023] Optionally, after the thick side processing of each section of the tapered welded blank with a difference in thickness is completed, the thin measurement is subjected to the last step of counter-compensation processing, including: after the thick side processing of each section of the tapered welded blank with a difference in thickness is completed, the thin measurement distance processing is completed by less than one step distance, and the last step of the thin measurement processing is performed by giving a feed amount The anti-compensation method is used to ensure the transition between the tool paths on the thick and thin sides, so that the tool paths on the thick and thin sides of the tapered tailor-welded blank are on the same horizontal line.

[0024] Optionally, there is a repeated processing area on the anti-compensation side.

[0025] Optionally, the cyclic processing in this processing mode until the processing of the tapered part of the tailor-welded blank with different thickness is completed also includes:

[0026] The thickness variation area of ​​the tapered tailor-welded blank is obtained by the thickness of the three-dimensional mathematical model, and the middle weld position is used as the boundary line of the tool path variation on both sides of the thick and thin plates;

[0027] During machining, a starting point is set on the thick side, and the tool head moves from the starting point to the feed rate. Start machining, when the tool head crosses the dividing line, execute the springback difference Compensate the press command to feed amount Processing the thin side; when the tool head completes the thin side processing and crosses the dividing line, the tool head executes the retract command and retracts a springback difference , and then the feed rate The thin side is processed, and this processing method is circulated until the processing of the tapered part of the tailor-welded blank with different thickness is completed.

[0028] Beneficial Effects

[0029] In the process of processing the tailor-welded blanks with differential thickness, the present invention adopts a processing method of differential feed amount, performs reasonable feed amount compensation on the side of the plate with larger springback amount on the basis of the original standard feed amount, and maintains the standard feed amount on the side of the plate with smaller springback amount, thereby improving the difference in overall springback amount on both sides of the formed part of the tailor-welded blank with differential thickness, thereby improving the precision of the formed part and improving the forming quality.

[0030] The present invention also processes the tailor-welded plates with different thicknesses in a segmented processing manner to ensure that the final tool paths on both sides of the thickness are located at the same horizontal line, so as to prevent deformation of the formed parts caused by excessive difference in the tool paths on both sides of the thickness, thereby improving the accuracy and consistency of the formed parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The figure is a schematic flow chart of the springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness according to the present invention;

[0032] Figure 2The figure shows a schematic diagram of a three-dimensional mathematical model for incremental forming of a tapered part of a tailor-welded blank with a difference in thickness constructed according to the present invention;

[0033] Figure 3 The figure shows the springback amount on both sides of the tapered part of the differential thickness tailor-welded blank according to the present invention;

[0034] Figure 4 The figure shows a schematic diagram of the differential feed amount on both sides of the tapered part of the differential thickness tailor-welded blank of the present invention;

[0035] Figure 5 The figure shows a schematic diagram of the segmented processing of the tapered part of the tailor-welded plate with different thickness according to the present invention. DETAILED DESCRIPTION

[0036] The following is a further description in conjunction with the accompanying drawings and specific embodiments. In the description of the present invention, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features.

[0037] Example 1

[0038] This embodiment introduces a springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness, including:

[0039] Construct a three-dimensional mathematical model of a tapered tailor-welded blank with differential thickness;

[0040] Based on the three-dimensional mathematical model, a springback curve of a tapered part of a tailor-welded blank with differential thickness is obtained, and based on a comparison between the springback curve of the tapered part of a tailor-welded blank with differential thickness and a theoretical contour line, a springback difference between the thick and thin sides of the tapered part of the tailor-welded blank with differential thickness is obtained;

[0041] Based on the springback difference and the tool head reference feed amount, the feed amount on the side of the tapered part of the tailor-welded blank with a large springback amount is obtained;

[0042] The tapered part of the tailor-made welded blank with differential thickness is divided into sections based on the forming depth of the tapered part of the tailor-made welded blank with differential thickness, and the thick and thin sides of each tapered part of the tailor-made welded blank with differential thickness are respectively given corresponding feed amounts for processing. After the thick side processing of each tapered part of the tailor-made welded blank with differential thickness is completed, the thin side is subjected to the last step of counter-compensation processing to complete the processing of each tapered part of the tailor-made welded blank with differential thickness, and this processing method is cyclically processed until the processing of the tapered part of the tailor-made welded blank with differential thickness is completed.

[0043] In practical applications, due to the large difference in springback on both sides of the sheet during the progressive forming process, the dimensional accuracy of the formed part will be significantly reduced, directly affecting the product quality. The present invention fully considers the factor that there is a large difference in springback on both sides of the sheet, and improves the springback error in a targeted manner according to the characteristics of the thin and thin sides of the differential thickness plate. Since the springback of the thin measurement is large, the present invention maintains the standard feed rate for the thick side, and performs reasonable feed rate compensation for the thin measurement based on the original standard feed rate. In the process of processing the differential thickness tailored welded plates, they are first divided into sections according to their three-dimensional model depth, and then each section of the differential thickness tailored welded plate is processed in sections. In addition, the present invention also processes the differential thickness tailored welded plates by means of segmented processing, which can overcome the problem of deformation of the formed part caused by excessive difference in tool tracks on both sides of the differential thickness tailored welded plates. Figure 1 As shown, it is a flow chart of the springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness according to the present invention.

[0044] Example 2

[0045] Based on Example 1, this example introduces a specific implementation process of a method for controlling springback compensation based on incremental forming of tailor-welded blanks with differential thickness. Figure 2 As shown, a three-dimensional mathematical model for incremental forming of a tapered part of a tailor-welded blank with a difference in thickness is constructed for the present invention, which specifically includes the following contents:

[0046] 1. Calculate the springback difference between the thick and thin sides

[0047] Based on the comparison between the springback curve of the tapered part of the tailor-welded blank with a difference in thickness and the theoretical contour line, the springback difference between the thick and thin sides of the tapered part of the tailor-welded blank with a difference in thickness is obtained, including:

[0048] At the middle position of the deformation area of ​​the tapered part of the differential thickness welded plate, uniformly select points, of which ≥5, such as Figure 3 As shown, the springback corresponding to each point on the thin side is extracted as , the springback amount corresponding to each point on the thick side is , calculate the mean springback of the thick side And the average value of thin springback , based on the mean springback value of the thick side and the mean value of the thin-film springback Obtain the springback difference between the thick and thin sides of the tapered tailor-welded blank ; Wherein, the deformation area of ​​the tapered part of the differential thickness welded plate is the area between the springback curve and the theoretical contour line. In the process of taking points, the step intervals of the points taken on both sides of the thickness are the same.

[0049] Calculate the mean springback value of the thick side Calculated by the following formula:

[0050]

[0051] Calculate the mean springback value of the thick side Calculated by the following formula:

[0052]

[0053] Springback difference between the thick and thin sides of the tapered tailor-welded blank Calculated by the following formula:

[0054] .

[0055] Based on the springback difference and the tool head reference feed amount, the feed amount on the side with a large springback amount of the tapered part of the differential thickness welded blank is obtained by the following formula:

[0056] ,

[0057] In the formula, is the tool head base feed, The feed amount is the side with larger springback of the tapered part of the differential thickness welded plate.

[0058] In this embodiment, the side with a larger springback of the tapered tailor-welded blank is the thin side of the tapered tailor-welded blank, and the side with a smaller springback is the thick side. Figure 4 As shown, the supply amount is given to the thin-measurement of the tapered parts of the tailor-welded blanks with different thicknesses. Processing is performed to provide a supply amount to the thick side For processing.

[0059] 2. Segment processing

[0060] Since the thin plates and thick plates on both sides of the tapered tailor-welded blanks are processed with different feed rates, the springback amount, i.e., the deformation amount, of the thin and thick plates will increase with the increase of the number of tool paths, which will cause the tool head processing height difference to gradually increase, and then cause a large gap in the tool head processing trajectory, affecting the workpiece forming quality. Therefore, this embodiment adopts a segmented processing method to overcome the above shortcomings.

[0061] Firstly, the thickness variation area of ​​the tapered part of the tailor-welded blank with differential thickness is obtained through the thickness of the pre-built 3D model, and the middle weld position is used as the boundary line of the tool path variation on both sides of the thick and thin plates.

[0062] like Figure 5 As shown, the formed part is divided into multiple sections for processing according to the forming depth of the tapered part of the differential thickness tailor-welded blank, and each section is processed as follows:

[0063] The tool head base feed is , that is, the step length, is the difference in springback between the thick and thin sides of the tapered tailor-welded blank, and k is the threshold of the number of processing steps. If k is a non-integer, k is directly rounded down to retain only the integer part.

[0064] When processing the k+1th step, the tool paths on both sides of the thickness are returned to the same horizontal line. The tool path contour line at the position is used as the reference, and the anti-compensation thin measurement is performed for a feed amount. There is a certain repeated processing area on the anti-compensation side, such as Figure 4 As shown, this ensures the transition between the tool rails on both sides and makes the tool rails on both sides located on the same horizontal line.

[0065] In this embodiment, k is set to 4. That is, after the fifth step of processing the thick side in each segment, the thick side processing is completed. At this time, since the feed amount for the thick side processing is , so the knife track height is 5* . With 5* The tool path contour line at the position is used as the reference for anti-compensation and thin measurement of a feed amount At this time, due to the different springback amounts on both sides of the thick and thin parts, the different feed amounts applied result in the thin measurement distance being processed less than one step. The anti-compensation method is used to ensure the transition between the tool paths on the thick and thin sides, so that the tool paths on both sides are on the same horizontal line.

[0066] During actual machining, a starting point is set on the thick side, and the tool head moves from the starting point to the feed rate. Start machining, when the tool head crosses the dividing line, execute the springback difference Compensate the press command to feed amount Processing the thin side; when the tool head completes the thin side processing and crosses the dividing line, the tool head executes the retract command and retracts a springback difference , and then the feed rate The thin side is processed and this processing method is cyclic until all the pre-divided sections of the tapered tailor-welded blank are processed.

[0067] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness, characterized by comprising: Construct a three-dimensional model of a tapered part of a tailor-welded blank with differential thickness; Based on the three-dimensional mathematical model, a springback curve of a tapered part of a tailor-welded blank with differential thickness is obtained, and based on a comparison between the springback curve of the tapered part of a tailor-welded blank with differential thickness and a theoretical contour line, a springback difference between the thick and thin sides of the tapered part of the tailor-welded blank with differential thickness is obtained; Based on the springback difference and the tool head reference feed amount, the feed amount on the side of the tapered part of the tailor-welded blank with a large springback amount is obtained; The tapered part of the tailor-made welded blank with differential thickness is divided into sections based on the forming depth of the tapered part of the tailor-made welded blank with differential thickness, and the thick and thin sides of each tapered part of the tailor-made welded blank with differential thickness are respectively given corresponding feed amounts for processing. After the thick side processing of each tapered part of the tailor-made welded blank with differential thickness is completed, the thin side is subjected to the last step of counter-compensation processing to complete the processing of each tapered part of the tailor-made welded blank with differential thickness, and this processing method is cyclically processed until the processing of the tapered part of the tailor-made welded blank with differential thickness is completed.

2. The springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness according to claim 1 is characterized in that: The springback difference between the thick and thin sides of the tapered part of the tailor-welded blank based on the difference in thickness is obtained by comparing the springback curve of the tapered part of the tailor-welded blank with the theoretical contour line, including: At the middle position of the deformation area of ​​the tapered part of the thickness difference welded plate, the points, of which ≥5, extract the springback value corresponding to each point on the thin side as , the springback amount corresponding to each point on the thick side is , calculate the mean springback of the thick side And the average value of thin springback , based on the mean springback value of the thick side and the mean value of the thin-film springback Obtain the springback difference between the thick and thin sides of the tapered tailor-welded blank ; wherein the deformation area of ​​the tapered part of the differential thickness welded plate is the area between the rebound curve and the theoretical contour line.

3. The springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness according to claim 2 is characterized in that: The calculation of the mean springback value of the thick side Calculated by the following formula: ， The calculation of the mean springback value of the thick side Calculated by the following formula: ， The springback difference between the thick and thin sides of the tapered part of the differential thickness tailor-welded blank Calculated by the following formula: 。 4. The springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness according to claim 3 is characterized in that: The feed amount on the side with a larger springback amount of the tapered part of the tailor-welded blank with a different thickness is obtained based on the springback difference and the tool head reference feed amount, and is calculated by the following formula: ， In the formula, is the tool head base feed, The feed amount is the side with larger springback of the tapered part of the differential thickness welded plate.

5. The method for controlling springback compensation based on incremental forming of tailor-welded blanks with differential thickness according to claim 4 is characterized in that: The processing of each segment of the tapered tailor-welded blank with a difference in thickness by respectively giving corresponding feed amounts to both sides of the tapered part comprises: giving a tool head reference feed amount to the thick side of each segment of the tapered tailor-welded blank with a difference in thickness; Processing is performed by feeding the thin side of each section of the tapered tailor-welded blank with a feed amount of For processing.

6. The springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness according to claim 5 is characterized in that: After the thick side processing of each section of the tapered welded blank with different thickness is completed, the thin measurement is subjected to the last step of counter compensation processing, including: after the thick side processing of each section of the tapered welded blank with different thickness is completed, the thin measurement distance processing is completed by less than one step distance, and the last step of the thin measurement processing is performed by giving a feed amount The anti-compensation method is used to ensure the transition between the tool paths on the thick and thin sides.

7. The springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness according to claim 6 is characterized in that: There is a repeated processing area on the anti-compensation side.

8. The springback compensation control method based on incremental forming of tailor-welded blanks with differential thickness according to claim 7 is characterized in that: The cyclic processing in this processing mode until the processing of the tapered part of the tailor-welded blank with different thickness is completed also includes: The thickness variation area of ​​the tapered tailor-welded blank is obtained by the thickness of the three-dimensional mathematical model, and the middle weld position is used as the boundary line of the tool path variation on both sides of the thick and thin plates; During machining, a starting point is set on the thick side, and the tool head moves from the starting point to the feed rate. Start machining, when the tool head crosses the dividing line, execute the springback difference Compensate the press command to feed amount Processing the thin side; when the tool head completes the thin side processing and crosses the dividing line, the tool head executes the retract command and retracts a springback difference , and then the feed rate The thin side is processed, and this processing method is circulated until the processing of the tapered part of the tailor-welded blank with different thickness is completed.

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