Springback control method for tailor-welded material stamping part and part taking device

Abstract

The invention provides a springback control method for a tailor-welded material stamping part. The springback control method comprises the steps that firstly, the stamping springback amount of tailor-welded materials is reduced in a hot stamping mode; and secondly, a partitioning die is adopted for first-time stamping and last-time stamping, namely stamping with the maximum deformation and final fine trimming stamping, adaptive adjustment of the optimal stamping temperature, stamping force and stamping speed is conducted on different plates made of tailor-welded materials, then the stamping precision of the tailor-welded materials is improved, and springback is further reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of stamping forming process, in particular to a springback control method and a taking device for a tailor-welded blank stamping part. BACKGROUND

[0002] In automobile manufacturing, the automobile sunroof frame as a key component, its quality has an important influence on the safety, sealing and aesthetics of the automobile; with the development of automobile lightweight technology, and because the tailor-welded blank is welded by plates with different strength, thickness and material, it can achieve weight reduction while meeting the structural performance requirements, so the tailor-welded blank is increasingly widely used in automobile sunroof frame stamping parts.

[0003] At present, for the sunroof frame adopting tailor-welded blank, its processing mode is usually in the form of multi-stage stamping, such as when four-stage stamping is adopted, the first stamping is to preliminarily form the approximate outline of the sunroof frame; the second and third stampings are to successively stamp the U-shaped basic structure, the drainage groove, the reinforcing rib, the mounting hole boss and other structures; the fourth stamping is to perform finishing, surface treatment and functional forming on the sunroof frame; however, due to the large difference in mechanical properties of each part of the tailor-welded blank, the stress distribution is complex during stamping deformation, and the springback law is difficult to accurately predict, therefore, even if the multi-stage stamping form is adopted, it is also difficult to ensure the dimensional accuracy of the sunroof frame stamping part, thereby affecting the product quality. Therefore, there is an urgent need for a relatively effective springback control method for controlling the tailor-welded blank stamping part of the automobile sunroof frame. SUMMARY

[0004] The purpose of the present application is to design a springback control method for a tailor-welded blank stamping part to solve the problems raised in the background art. To achieve the above purpose, the present application provides the following technical solution: comprising the following steps: S1, pretreatment: after surface cleaning treatment of the tailor-welded blank, according to the ideal springback amount and ideal springback trend required by different materials in the tailor-welded blank in primary stamping, the different plates in the tailor-welded blank are heated to their respective optimal stamping temperatures in primary stamping; S2, primary stamping: the heated tailor-welded blank is transferred to the primary stamping die for stamping by the taking device, and the primary stamping die adopts the form of block die; S3, intermediate stamping: the tailor-welded blank after temperature compensation is transferred to a plurality of sets of intermediate stamping dies in intermediate stamping in turn by the taking device, and the plurality of sets of intermediate stamping dies do not adopt the form of block die; S4, final stamping: after the different plates in the tailor-welded blank after the previous stage of stamping are heated to their respective optimal stamping temperatures in final stamping, the heated tailor-welded blank is transferred to the final stamping die for stamping by the taking device, and the final stamping die adopts the form of block die. S5, discharging after online detection.

[0005] Further, in the stamping process in S3, when the material area of the high-strength and 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 material area of the high-strength and 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.

[0006] Further, when the material area of the high-strength and low-plasticity region in contact with the cavity of the intermediate stamping die changes, the control module will regulate the stamping speed of the intermediate stamping die, and the control module is pre-inputted with a change rate threshold ΔC0 of the area, and the control module is used to calculate whether the real-time change rate ΔC1 of the material area of the high-strength and low-plasticity region in contact with the cavity of the intermediate stamping die in the stamping process is greater than the change rate threshold ΔC0.

[0007] Further, the control module is pre-inputted with a standard stamping speed V2 of the intermediate stamping die, and the control module regulates the real-time stamping speed V3 of the intermediate stamping die through ΔC1, ΔC0 and V2; wherein V3=axV2xΔC0 / ΔC1; a is a pre-inputted correction coefficient.

[0008] Further, 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.

[0009] Further, when the material area of the high-strength and low-plasticity region 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 material area of the high-strength and 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.

[0010] Further, when the material area of the high-strength and low-plasticity region in contact with the cavity of the intermediate stamping die changes, the control module will regulate the vibration frequency of the vibration-assisted stamping, and the control module is pre-inputted with a standard vibration frequency Z2 of the vibration-assisted stamping, and the control module regulates the real-time vibration frequency Z3 of the vibration-assisted stamping through V3, V2 and Z2; wherein Z3=bxZ2xV3 / V2; b is a pre-inputted correction coefficient.

[0011] Further, the vibration assisted stamping mode is adopted in the stamping processes 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 block die, the standard thickness is d0, the thickness of the tailor-welded blank actually 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.

[0012] Further, the step S0 is further arranged before the step S1. S0, determination of the standard value of the process parameter: selecting each component plate of the tailor-welded blank, and obtaining the mechanical property parameters of each plate through experiments, including the elastic modulus, yield strength, tensile strength, elongation and hardening index; then, a finite element model of the tailor-welded blank is established, the springback amount and springback trend of each plate in the tailor-welded blank under different stamping process parameters are simulated, when the ideal springback amount and ideal springback trend are reached, the value of the process parameter is selected as the standard value, the process parameter includes the stamping speed, temperature and vibration frequency.

[0013] Further, 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.

[0014] The application further discloses a taking device for the tailor-welded blank stamping part, which comprises a multi-axis mechanical arm and a vacuum adsorption unit arranged on the execution end of the multi-axis mechanical arm, and the surface of the vacuum adsorption unit is covered with high-temperature-resistant flexible silica gel material; the distribution of the vacuum adsorption unit is matched with the gravity center and stress position of the tailor-welded blank.

[0015] Compared with the prior art, the application has the following beneficial effects: firstly, the hot stamping form is adopted to reduce the stamping springback amount of the tailor-welded blank; secondly, the block die is adopted in the first stamping and the last stamping, that is, the stamping with the largest deformation and the last finishing stamping, the best stamping temperature, stamping force and stamping speed are adaptively adjusted for different plates of the tailor-welded blank, so as to improve the stamping precision of the tailor-welded blank and further reduce the springback. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0017] Figure 1 It is a stamping flowchart of the application. DETAILED DESCRIPTION

[0018] To further clarify the technical means and effects taken by the present application to achieve the predetermined inventive purpose, the specific embodiments, structures, features and effects thereof according to the present application are described in detail below in conjunction with the drawings and preferred embodiments.

[0019] Embodiment: A springback control method for a tailor-welded material stamping part, comprising the following steps: S0, determination of process parameter standard value: select each component plate of the tailor-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 tailor-welded material to simulate the springback amount and springback trend of each plate in the tailor-welded material under different stamping process parameters, and when the ideal springback amount and ideal springback trend are reached, the value of the process parameter is selected as the standard value, including stamping speed, temperature and vibration frequency; the finite element model simulation analysis is performed on each stamping process to determine the standard value of the process parameter in each stamping process; wherein the ideal size after the previous stamping is the ideal size before the next stamping; through finite element analysis, the optimal stamping speed, temperature and vibration frequency in each stamping process are simulated, and then the actual experimental correction value is used for correction in theory and actual stamping to ensure the accuracy of stamping.

[0020] S1, pretreatment: after surface cleaning treatment of the tailor-welded material, according to the ideal springback amount and ideal springback trend required by different materials in the tailor-welded material in primary stamping, the different plates in the tailor-welded material are heated to their respective optimal stamping temperature in primary stamping; wherein the heating material can adopt the heat release of induction heating, and the heating temperature of different plates is different, for example, the optimal stamping temperature of thick plates is greater than that of thin plates, the optimal stamping temperature of high-strength plates is greater than that of low-strength plates, and the optimal stamping temperature of low-plasticity plates is greater than that of high-plasticity plates, thereby eliminating the problem that in the past, the consistent stamping temperature in hot stamping caused that multiple plates in the tailor-welded material were not at their respective optimal stamping temperature, thereby reducing the effect of reducing springback in hot stamping.

[0021] S2, primary stamping: the heated tailor-welded material is transferred to the primary stamping die through the taking device for stamping, and the primary stamping die adopts the form of block die; wherein the stamping force and stamping speed of each block die can be controlled according to the results of finite element analysis combined with specific experiments, thereby ensuring sufficient stamping of each plate and reducing the springback problem caused by large size deformation in the first stamping.

[0022] S3, intermediate stamping: the temperature-compensated tailor-welded blank is transferred to a plurality of intermediate stamping dies in sequence by a picking device for stamping, and the plurality of intermediate stamping dies do not adopt the form of a segmented die; the process is still carried out in the form of hot stamping, which ensures the stamping efficiency while reducing springback.

[0023] S4, final stamping: the different plates in the tailor-welded blank after the previous stamping are heated to their respective optimal stamping temperatures for the final stamping, and then the heated tailor-welded blank is transferred to a final stamping die for stamping by a picking device, and the final stamping die adopts the form of a segmented die; this ensures sufficient stamping of each plate, thereby improving the stamping precision during the final finishing stamping, and making each plate reach a relatively high ideal size.

[0024] S5, after a certain period of pressure holding and cooling, online detection is performed, and after passing, the tailor-welded blank can be discharged by a picking device, thereby realizing complete stamping of the tailor-welded blank.

[0025] In other embodiments, during the stamping process in S3, when the area of the high-strength, 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, 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; by adjusting the stamping speed of the stamping piece during the stamping process when stamping different materials, the stamping quality is improved and stress concentration is reduced; in addition, when the area of the high-strength, low-plasticity region material in contact with the cavity of the intermediate stamping die changes, the control module will control the stamping speed of the intermediate stamping die, the control module has a pre-input area change rate threshold ΔC0, the control module is used to calculate whether the real-time change rate ΔC1 of the area of the high-strength, low-plasticity region material in contact with the cavity of the intermediate stamping die during the stamping process is greater than the change rate threshold ΔC0; when ΔC1 is less than ΔC0, the stamping speed is increased, thereby improving the stamping efficiency; when ΔC1 is greater than ΔC0, the stamping speed is reduced, thereby reducing the stamping speed, improving the stamping quality, and reducing stress concentration, thereby reducing springback; the control module has a pre-input standard stamping speed V2 of the intermediate stamping die, and the control module controls the real-time stamping speed V3 of the intermediate stamping die through ΔC1, ΔC0, and V2; wherein V3=axV2xΔC0 / ΔC1; and V3V1, a is a pre-input correction coefficient and is obtained from finite element analysis and actual experimental process; thereby the stamping speed can be controlled, and the stamping process of the intermediate stamping is improved.

[0026] In addition, in the stamping process in S3, the vibration assisted stamping mode is adopted, micro slip between internal grains of the material can be generated, dislocation movement resistance is reduced, the flow stress of the material is reduced, the material is more uniformly filled in the mold cavity, and the vibration can also inhibit the elastic recovery after the stamping unloading; the vibration frequency of the vibration assisted stamping can be adjusted according to the stamping speed, so as to prevent defects caused by the vibration frequency at a fixed frequency, for example, if the vibration frequency is too low when the stamping is too fast, the effect is poor; and if the vibration frequency is too high when the stamping is too slow, the stamping part is easily damaged; therefore, when the material area of the high-strength and low-plasticity region 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 material area of the high-strength and 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; when the material area of the high-strength and low-plasticity region in contact with the cavity of the intermediate stamping die changes, the control module controls the vibration frequency of the vibration assisted stamping, the standard vibration frequency Z2 of the vibration assisted stamping is pre-input on the control module, and the control module controls the real-time vibration frequency Z3 of the vibration assisted stamping through V3, V2 and Z2; wherein Z3=b x Z2 x V3 / V2; b is a pre-input correction coefficient, so as to realize real-time adjustment of the vibration frequency when the stamping speed is large, and the vibration frequency is reduced when the stamping speed is small, and the stamping quality of the stamping part is ensured. In the stamping process in S2 and S4, the vibration assisted stamping mode is adopted, the vibration frequency of the vibration assisted stamping is determined according to the thickness of the tailor-welded material corresponding to different modules in the split die, the standard thickness is d0, the actual thickness of the tailor-welded material 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 pre-input correction coefficient, since the split die is adopted, different vibration frequencies can be set on each die, so as to adapt to different strength plates, and the stamping quality is improved while the springback is reduced; when the plate thickness is large, a larger vibration frequency is used to ensure the stamping effect, and when the thickness is small, a smaller vibration frequency is used to prevent material damage caused by excessive vibration.

[0027] The application further discloses a taking device for the tailor-welded material stamping part, which comprises a multi-axis mechanical arm and a vacuum adsorption unit installed on the execution end of the multi-axis mechanical arm, and the surface of the vacuum adsorption unit is covered with high-temperature-resistant flexible silica gel material.

[0028] It should be noted that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements can also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements can also be present. As used herein, the terms "upper", "lower", "left", "right", "front", "rear", and the like as can be used herein, merely describe

[0029] The above descriptions are only the preferred embodiments of the present application, not intended to limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiments, it is not intended to limit the present application, any person skilled in the art can make some changes or modifications to the above disclosed technical contents to make equivalent embodiments with equivalent changes, but as long as it does not deviate from the technical solution of the present application, any modification, equivalent change and modification of the above embodiments according to the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A method for controlling the springback of a stamped part made of tailor-welded material, characterized in that: The following steps are involved: S1. Pretreatment: After cleaning the surface of the tailor-welded material, the different sheets of the tailor-welded material are heated to their respective optimal stamping temperatures during the primary stamping according to the ideal springback amount and ideal springback trend required by the different materials in the tailor-welded material during the primary stamping. S2. Primary stamping: The heated welded material is transferred to the primary stamping die through the removal device for stamping. The primary stamping die adopts the form of a block die; S3, intermediate stamping: The welded materials after reheating are transferred to several sets of intermediate stamping dies in the intermediate stamping through the pick-up device for stamping. None of the intermediate stamping dies are in the form of block dies; S4, final stamping: First, the different plates of the welded material after the previous stamping are heated to their respective optimal stamping temperatures for the final stamping. The heated welded material is then transferred to the final stamping die for stamping by a pick-up device. The final stamping die is in the form of a segmented die. S5. Unloading after online inspection.

2. The springback control method for tailor-welded stamping parts according to claim 1, characterized in that: During the stamping process in S3, when the area of ​​the material in the high-strength and 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 material in the high-strength and 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.

3. The springback control method for tailor-welded stamping parts according to claim 2, characterized in that: 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 regulate the stamping speed of the intermediate stamping die. The control module is pre-input with an area change rate threshold ΔC0. The control module is used to calculate whether the real-time change rate ΔC1 of the high-strength, low-plasticity material area in contact with the cavity of the intermediate stamping die during the stamping process is greater than the change rate threshold ΔC0.

4. The springback control method for tailor-welded stamping parts according to claim 3, characterized in that: The control module is pre-input with the standard stamping speed V2 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 V2; Where V3 = axV2 x ΔC0 / ΔC1; a is the correction coefficient entered in advance.

5. The springback control method for tailor-welded stamping parts according to claim 4, characterized in that: In the stamping process in S3, a vibration-assisted stamping method is adopted, and the vibration frequency of the vibration-assisted stamping is adjusted according to the stamping speed.

6. The springback control method for tailor-welded stamping parts according to claim 5, characterized in that: When the area of ​​the material in the high-strength and low-plasticity region 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 material in the high-strength and 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.

7. The springback control method for tailor-welded stamping parts according to claim 6, characterized in that: 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 vibration frequency of the vibration-assisted stamping. The control module has pre-input the standard vibration frequency Z2 of the vibration-assisted stamping. The control module adjusts the real-time vibration frequency Z3 of the vibration-assisted stamping through V3, V2 and Z2. Where Z3=bxZ2xV3 / V2; b is the correction coefficient entered in advance.

8. The springback control method for tailor-welded stamping parts according to claim 1, characterized in that: Vibration-assisted stamping is used 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 block mold. Assuming the standard thickness is d0, the actual thickness of the welding material corresponding to different modules is di, and the standard vibration frequency is Z0, then the actual vibration frequency corresponding to different modules is Zi=qxZ0xdi / d0; q is the pre-input correction coefficient.

9. The springback control method for tailor-welded stamping parts according to claim 1, characterized in that: Before step S1, step S0 is also provided; S0. Determination of standard values ​​for process parameters: Select the various components of the tailor-welded material and obtain the mechanical properties of each component through testing, including elastic modulus, yield strength, tensile strength, elongation, and hardening index. Subsequently, a finite element model of the tailor-welded material is established to simulate the springback amount and springback trend of each component 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. Finite element model simulation analysis simulates each stamping process to determine the standard values ​​of the process parameters in each stamping process; among them, the ideal size after the previous stamping is the ideal size before the next stamping.

10. A device for removing stamped parts of tailor-welded materials, used for transferring the tailor-welded materials between stamped parts at each level in the control method according to any one of claims 1 to 9, characterized in that: It includes a multi-axis robotic arm and a vacuum adsorption unit installed on the execution end of the multi-axis robotic arm; the distribution of the vacuum adsorption unit matches the center of gravity and stress-bearing parts of the welding material.

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