A springback control method and a taking device for a tailor-welded material stamping

Abstract

The present application provides a kind of springback control method of tailor-welded material stamping part, first, the form of hot stamping is used to reduce the springback amount of tailor-welded material stamping;Second, in the first stamping and last stamping, that is, in the stamping of maximum deformation and the last finishing stamping, the block die is used, and the different plate of tailor-welded material is adjusted to the best stamping temperature, stamping force and stamping speed, thereby improving the stamping precision of tailor-welded material, and further reducing springback.

Description

Technical Field

[0001] This invention relates to the field of stamping forming technology, specifically to a springback control method and part removal device for stamped parts made of welded materials. Background Technology

[0002] In automobile manufacturing, the sunroof frame is a key component, and its quality has a significant impact on the safety, sealing, and aesthetics of the vehicle. With the development of automotive lightweighting technology, and because the welded material is made of plates of different strengths, thicknesses, and materials, it can reduce weight while meeting structural performance requirements. Therefore, the application of welded materials in stamped parts of automotive sunroof frames is becoming increasingly widespread.

[0003] Currently, the processing of sunroof frames made of welded materials typically involves multi-stage stamping. For example, in a four-stage stamping process, the first stamping roughly shapes the outline of the sunroof frame; the second and third stampings sequentially form the U-shaped base structure, drainage channels, reinforcing ribs, mounting hole bosses, and other structures; the fourth stamping performs finishing, surface treatment, and functional shaping of the sunroof frame. However, due to the significant differences in the mechanical properties of the various parts of the welded material, the stress distribution during stamping deformation is complex, and the springback pattern is difficult to predict accurately. Therefore, even with multi-stage stamping, it is difficult to guarantee the dimensional accuracy of the sunroof frame stampings, thus affecting product quality. Therefore, there is an urgent need for a more effective method to control the springback of welded material stampings for automotive sunroof frames. Summary of the Invention

[0004] The purpose of this invention is to design a springback control method for stamped parts made of welded materials, in order to solve the problems mentioned in the background art. To achieve the above objective, this invention provides the following technical solution, including the following steps:

[0005] S1. Pre-treatment: After cleaning the surface of the welded material, according to the ideal springback amount and ideal springback trend required by different materials in the primary stamping, the different plates in the welded material are heated to their respective optimal stamping temperature in the primary stamping.

[0006] S2, Primary stamping: The heated welded material is transferred to the primary stamping die for stamping by the part taking device. The primary stamping die is in the form of a block die.

[0007] S3, Intermediate stamping: The heated welded material is transferred sequentially to several sets of intermediate stamping dies in the intermediate stamping stage by the part taking device. None of the several sets of intermediate stamping dies adopt the form of block dies.

[0008] S4, Final stamping: First, the different plates in the welded material after the previous stamping are heated to their respective optimal stamping temperatures in the final stamping. Then, the heated welded material is transferred to the final stamping die for stamping by the part removal device. The final stamping die is in the form of a block die.

[0009] S5. Material is unloaded after online inspection.

[0010] Furthermore, during the stamping process in S3, when the area of ​​the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die does not change, the stamping speed of the intermediate stamping die is V1; when the area of ​​the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die changes, the stamping speed of the intermediate stamping die is V2, and V1 > V2.

[0011] Furthermore, when the area of ​​the high-strength, low-plasticity material in contact with the cavity of the intermediate stamping die changes, the control module will adjust the stamping speed of the intermediate stamping die. The control module is pre-inputted with a threshold value ΔC0 for the rate of change of area. The control module is used to calculate whether the real-time rate of change ΔC1 of the area of ​​the high-strength, low-plasticity material in contact with the cavity of the intermediate stamping die during the stamping process is greater than the rate of change threshold ΔC0.

[0012] Furthermore, the standard stamping speed V0 of the intermediate stamping die is pre-input into the control module, and the control module adjusts the real-time stamping speed V3 of the intermediate stamping die through ΔC1, ΔC0 and V0;

[0013] Where V3 = axV0xΔC0 / ΔC1; a is a pre-input correction coefficient.

[0014] Furthermore, in the stamping process of S3, a vibration-assisted stamping method is adopted, and the vibration frequency of the vibration-assisted stamping is adjusted according to the stamping speed.

[0015] Furthermore, when the area of ​​the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die remains unchanged, the vibration frequency of the vibration-assisted stamping is Z1; when the area of ​​the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die changes, the vibration frequency of the vibration-assisted stamping is Z2, and Z1 > Z2.

[0016] Furthermore, when the area of ​​the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die changes, the control module will adjust the vibration frequency of the vibration-assisted stamping. The standard vibration frequency Z0 of the vibration-assisted stamping is pre-input into the control module, and the control module adjusts the real-time vibration frequency Z3 of the vibration-assisted stamping through V3, V2 and Z0.

[0017] Where Z3 = bxZ0xV3 / V2; b is a pre-input correction coefficient.

[0018] Furthermore, vibration-assisted stamping is adopted in the stamping process of S2 and S4. The vibration frequency of vibration-assisted stamping is determined according to the thickness of the welding material corresponding to different modules in the segmented mold. Let the standard thickness be d0, the actual thickness of the welding material corresponding to different modules be di, and the standard vibration frequency be Z0. Then the actual vibration frequency Zi corresponding to different modules is Zi=qxZ0xdi / d0; q is a pre-input correction coefficient.

[0019] Furthermore, step S0 is provided before step S1;

[0020] S0. Determination of standard values ​​for process parameters: Select the constituent plates of the welded material and obtain the mechanical property parameters of each plate through experiments, including elastic modulus, yield strength, tensile strength, elongation and hardening index; then establish a finite element model of the welded material to simulate the springback amount and springback trend of each plate in the welded material under different stamping process parameters. When the ideal springback amount and ideal springback trend are achieved, the value of the process parameter is selected as the standard value. The process parameter includes stamping speed, temperature and vibration frequency.

[0021] Furthermore, the finite element model simulation analysis simulates each stamping process to determine the standard values ​​of the process parameters for each stamping process; the ideal dimension after the previous stamping stage is the ideal dimension before the next stamping stage.

[0022] The present invention also discloses a part removal device for stamped parts made of welded material, including a multi-axis robotic arm and a vacuum adsorption unit installed on the execution end of the multi-axis robotic arm. The surface of the vacuum adsorption unit is covered with a high-temperature resistant flexible silicone material. The distribution of the vacuum adsorption unit matches the center of gravity and stress points of the welded material.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: First, the present invention uses hot stamping to reduce the amount of springback in the stamping of the welded material; second, it uses segmented dies in the first stamping and the last stamping, that is, the stamping with the largest deformation and the final finishing stamping, to adapt and adjust the stamping temperature, stamping force and stamping speed of different plates of the welded material to improve the stamping accuracy of the welded material and further reduce springback. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the stamping process of the present invention. Detailed Implementation

[0026] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0027] Example: A method for controlling the springback of stamped parts made of welded materials, comprising the following steps:

[0028] S0. Determination of Standard Values ​​for Process Parameters: Select the constituent plates of the welded material and obtain the mechanical property parameters of each plate through experiments, including elastic modulus, yield strength, tensile strength, elongation, and hardening index. Then, establish a finite element model of the welded material to simulate the springback amount and springback trend of each plate under different stamping process parameters. When the ideal springback amount and ideal springback trend are achieved, the value of that process parameter is selected as the standard value. This process parameter includes stamping speed, temperature, and vibration frequency. The finite element model simulation analysis simulates each stamping process to determine the standard values ​​of the process parameters in each stamping process. The ideal dimension after the previous stamping stage is the ideal dimension before the next stamping stage. Through finite element analysis, the optimal stamping speed, temperature, and vibration frequency in each stamping process are simulated. Then, relevant correction values ​​from actual experiments are used to correct the theoretical and actual stamping to ensure the accuracy of stamping.

[0029] S1. Pre-treatment: After cleaning the surface of the welded material, based on the ideal springback amount and ideal springback trend required by different materials in the initial stamping, the different plates in the welded material are heated to their respective optimal stamping temperatures in the initial stamping. The heating material can be induction heating, which is exothermic. Different plates have different heating temperatures. For example, the optimal stamping temperature of thicker plates is higher than that of thinner plates, the optimal stamping temperature of high-strength plates is higher than that of low-strength plates, and the optimal stamping temperature of low-plasticity plates is higher than that of high-plasticity plates. This eliminates the problem of multiple plates not being at their respective optimal stamping temperatures in the welded material due to the uniform stamping temperature in the previous hot stamping process, thus reducing the effect of hot stamping in reducing springback.

[0030] S2. Primary stamping: The heated welded material is transferred to the primary stamping die by the part taking device for stamping. The primary stamping die adopts the form of a segmented die. The segmented die can control the stamping force and stamping speed of each die according to the results of finite element analysis and in combination with specific experiments, so as to ensure that each piece of sheet is fully stamped and reduce the springback problem caused by large dimensional deformation during the first stamping.

[0031] S3, Intermediate stamping: The heated welded material is sequentially transferred to several sets of intermediate stamping dies in the intermediate stamping stage by the part taking device. None of the intermediate stamping dies are in the form of segmented dies. This process is still carried out in the form of hot stamping, which ensures stamping efficiency while reducing springback.

[0032] S4. Final stage stamping: First, the different plates in the welded material after the previous stage stamping are heated to their respective optimal stamping temperatures in the final stage stamping. Then, the heated welded material is transferred to the final stage stamping die by the part removal device for stamping. The final stage stamping die adopts a segmented die form to ensure that each plate is fully stamped, thereby improving the stamping accuracy during the final finishing stamping and enabling each plate to achieve a high ideal size.

[0033] S5. After holding the pressure for a period of time and cooling, online testing is carried out. If the test is qualified, the material can be unloaded through the part removal device, thereby realizing the complete stamping of the welded material.

[0034] In other embodiments, during the stamping process in S3, when the area of ​​the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die remains unchanged, the stamping speed of the intermediate stamping die is V1; when the area of ​​the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die changes, the stamping speed of the intermediate stamping die is V2, and V1 > V2. By adjusting the stamping speed of the stamped part when stamping different materials during the stamping process, the stamping quality is improved and stress concentration is reduced. Furthermore, when the area of ​​the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die changes, the control module adjusts the stamping speed of the intermediate stamping die. The control module is pre-inputted with a threshold value ΔC0 for the rate of change of area. The control module is used to calculate the stamping speed of the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die during the stamping process. The real-time change rate ΔC1 of the material area in the high-strength, low-plasticity region of the die cavity is checked against the threshold ΔC0. When ΔC1 is less than ΔC0, the stamping speed is increased, thereby improving stamping efficiency. When ΔC1 is greater than ΔC0, the stamping speed is decreased, thus reducing stamping quality and reducing stress concentration, thereby reducing springback. The control module is pre-input with the standard stamping speed V0 of the intermediate stamping die. The control module uses ΔC1, ΔC0, and V0 to regulate the real-time stamping speed V3 of the intermediate stamping die. V3 = axV0xΔC0 / ΔC1, and V3 < V1. a is a pre-input correction coefficient derived from finite element analysis and actual experiments. This allows for the regulation of the stamping speed, thereby improving the stamping process of intermediate-level stamping.

[0035] Furthermore, in this embodiment, vibration-assisted stamping is used during the stamping process in S3. This allows for microscopic slippage between grains within the material, reducing misalignment resistance and thus lowering the material's flow stress. This enables the material to fill the mold cavity more uniformly, while vibration also suppresses elastic recovery after stamping unloading. The vibration frequency of vibration-assisted stamping can be adjusted according to the stamping speed to prevent defects caused by a fixed frequency. For example, if the stamping speed is too fast and the vibration frequency is too low, the effect will be poor; conversely, if the stamping speed is too slow and the vibration frequency is too high, the stamped part may be damaged. Therefore, when the area of ​​the high-strength, low-plasticity material in contact with the cavity of the intermediate stamping die remains unchanged, the vibration frequency of vibration-assisted stamping is Z1; when the area of ​​the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die remains unchanged, the vibration frequency of vibration-assisted stamping is Z1. When the material area of ​​the high-strength, low-plasticity region in contact with the cavity of the primary stamping die changes, the vibration frequency of the vibration-assisted stamping is Z2, and Z1 > Z2. When the material area of ​​the high-strength, low-plasticity region in contact with the cavity of the intermediate stamping die changes, the control module will adjust the vibration frequency of the vibration-assisted stamping. The control module has a pre-inputted standard vibration frequency Z0 for vibration-assisted stamping. The control module adjusts the real-time vibration frequency Z3 of vibration-assisted stamping through V3, V2, and Z0; where Z3 = b x Z0 x V3 / V2; b is a pre-input correction coefficient, thereby achieving real-time adjustment that increases the vibration frequency when the stamping speed is high and decreases the vibration frequency when the stamping speed is low, thus ensuring the stamping quality of the stamped parts.

[0036] In the stamping processes of S2 and S4, vibration-assisted stamping is used. The vibration frequency of vibration-assisted stamping is determined according to the thickness of the welded material corresponding to different modules in the segmented mold. Let the standard thickness be d0, the actual thickness of the welded material corresponding to different modules be di, and the standard vibration frequency be Z0. Then, the actual vibration frequency Zi corresponding to different modules is Zi = qxZ0xdi / d0; q is a pre-input correction coefficient. Since segmented molds are used, different vibration frequencies can be set on each mold to adapt to sheet metal of different strengths. This can improve stamping quality while reducing springback. When the sheet metal thickness is large, a larger vibration frequency is used to ensure the stamping effect. When the thickness is small, a smaller vibration frequency is used to prevent excessive vibration from damaging the material.

[0037] The present invention also discloses a part removal device for stamped parts made of welded material, including a multi-axis robotic arm and a vacuum adsorption unit installed on the execution end of the multi-axis robotic arm. The surface of the vacuum adsorption unit is covered with a high-temperature resistant flexible silicone material. The distribution of the vacuum adsorption unit matches the center of gravity and stress points of the welded material.

[0038] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component. The terms "upper," "lower," "left," "right," "front," "back," and similar expressions used in this document are for illustrative purposes only.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for controlling the springback of stamped parts made of welded materials, characterized in that, The method comprises the following steps: S1, pretreatment: after surface cleaning treatment of the tailor-welded material, the different plates in the tailor-welded material are heated to the best stamping temperature of each plate in the primary stamping according to the ideal rebound amount and ideal rebound trend required by different materials in the primary stamping; S2, primary stamping: the heated tailor-welded material is transferred to the primary stamping die through a picking device for stamping, and the primary stamping die adopts the form of a block die; S3, intermediate stamping: the tailor-welded material after temperature compensation is sequentially transferred to a plurality of intermediate stamping dies in the intermediate stamping through the picking device for stamping, and the plurality of intermediate stamping dies do not adopt the form of a block die; S4, final stamping: the different plates in the tailor-welded material after the previous stage of stamping are heated to the best stamping temperature of each plate in the final stamping, and then the heated tailor-welded material is transferred to the final stamping die through the picking device for stamping, and the final stamping die adopts the form of a block die; S5, online detection and discharging.

2. The springback control method of a tailor-welded blank stamping as set forth in claim 1, characterized by, In the stamping process in S3, when the area of the high-strength and low-plasticity region material in contact with the cavity of the intermediate stamping die does not change, the stamping speed of the intermediate stamping die is V1; when the area of the high-strength and low-plasticity region material in contact with the cavity of the intermediate stamping die changes, the stamping speed of the intermediate stamping die is V2, and V1>V2.

3. The springback control method of a tailor-welded blank stamping as set forth in claim 2, characterized by, When the area of the high-strength and low-plasticity region material in contact with the cavity of the intermediate stamping die changes, the control module controls the stamping speed of the intermediate stamping die, and the control module has a pre-input area change rate threshold ΔC0, and the control module is used to calculate whether the real-time change rate ΔC1 of the area of the high-strength and low-plasticity region material in contact with the cavity of the intermediate stamping die in the stamping process is greater than the change rate threshold ΔC0.

4. The springback control method of a tailor-welded blank stamping as set forth in claim 3, characterized by, The control module has a pre-input standard stamping speed V0 of the intermediate stamping die, and the control module adjusts the real-time stamping speed V3 of the intermediate stamping die through ΔC1, ΔC0 and V0; Wherein, V3=axV0xΔC0 / ΔC1; a is a pre-input correction coefficient.

5. The springback control method of a tailor-welded blank stamping as set forth in claim 4, characterized by, In the stamping process in S3, a vibration-assisted stamping mode is adopted, and the vibration frequency of the vibration-assisted stamping is adjusted according to the stamping speed.

6. The springback control method of a tailor-welded blank stamping as set forth in claim 5, characterized by, When the area of the high-strength and low-plasticity region material in contact with the cavity of the intermediate stamping die does not change, the vibration frequency of the vibration-assisted stamping is Z1; when the area of the high-strength and low-plasticity region material in contact with the cavity of the intermediate stamping die changes, the vibration frequency of the vibration-assisted stamping is Z2, and Z1>Z2.

7. The springback control method of a tailor-welded blank stamping as set forth in claim 6, characterized by, When the area of the high-strength and low-plasticity region material in contact with the cavity of the intermediate stamping die changes, the control module controls the vibration frequency of the vibration-assisted stamping, and the control module has a pre-input standard vibration frequency Z0 of the vibration-assisted stamping, and the control module adjusts the real-time vibration frequency Z3 of the vibration-assisted stamping through V3, V2 and Z0; Wherein, Z3=bxZ0xV3 / V2; b is a pre-input correction coefficient.

8. The springback control method of a tailor-welded blank stamping as defined in claim 1, wherein The vibration assisted stamping mode is adopted in the stamping process in S2 and S4, the vibration frequency of the vibration assisted stamping is determined according to the thickness of the tailor-welded blank corresponding to different modules in the split die, the standard thickness is d0, the actual thickness of the tailor-welded blank corresponding to different modules is di, the standard vibration frequency is Z0, then the actual vibration frequency Zi corresponding to different modules is q x Z0 x di / d0; q is a correction coefficient input in advance.

9. The springback control method of a tailor-welded blank stamping as defined in claim 1, wherein Before the step S1, a step S0 is further provided. In the step S0, the standard value of the process parameter is determined, the tailor-welded blank is selected, the mechanical property parameters of each plate material are obtained through test, including the elastic modulus, the yield strength, the tensile strength, the elongation and the hardening index; then the finite element model of the tailor-welded blank is established, the springback amount and the springback trend of each plate material in the tailor-welded blank under different stamping process parameters are simulated, when the ideal springback amount and the ideal springback trend are reached, the value of the process parameter is selected as the standard value, the process parameter includes the stamping speed, the temperature and the vibration frequency; The finite element model simulation analysis is performed on each stamping process, so as to determine the standard value of the process parameter in each stamping process; wherein the ideal size after the stamping of the previous stage is the ideal size before the stamping of the next stage.

10. A picking device for tailor-welded blank stampings, for the transfer of tailor-welded blanks between stampings in each stage of the control method according to any one of claims 1 to 9, characterized in that it comprises: The multi-axis mechanical arm, the vacuum adsorption unit mounted on the execution end of the multi-axis mechanical arm; the distribution of the vacuum adsorption unit is matched with the center of gravity and the stress position of the tailor-welded blank.

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