A die machining process for aluminum-magnesium alloy multi-press deep cavity forming

Abstract

The application discloses a die machining process for aluminum-magnesium alloy multi-pressure material deep cavity forming, which comprises the following steps: minimum drawing depth calibration and stamping direction simulation; forming optimization and forming margin calculation; inner pressure material arrangement and material supplement analysis; during the material supplement analysis; multi-circle design and pressure configuration; die machining assembly; staged debugging and partition pressure regulation; high-angle pre-loss and surface quality improvement; margin test correction. The application solves the problem that the single-action equipment of cold stamping forming cannot realize bidirectional air top and staged air top through the embedded self-pressure source mode, successfully utilizes the multi-circle combination mode of external double-pressure ring and internal pressure ring, realizes multiple motion pressure material, thereby greatly reduces the cavity depth of deep cavity automobile cover forming, reduces the stretching material removal amount, realizes the deep cavity forming technology depth reduction mode for aluminum-magnesium alloy, thereby realizes the deep cavity forming of high yield strength aluminum-magnesium alloy, and also provides a replicable mode for the forming of other lightweight materials.

Description

Technical Field

[0001] This invention relates to the field of automotive body panel mold technology, and in particular to a mold processing technology for deep cavity forming of aluminum-magnesium alloy multi-pressure material. Background Technology

[0002] Cold stamping forming of automotive body panel molds (hereinafter referred to as molds) is a major forming mode for low-cost and high-quality development of automobiles. The manufacturing process of mold cold stamping forming involves stretching and plastically deforming sheet metal. Its forming capability depends on the movement mode of the pressure device and the forming performance of the material. However, with the rise and development of new energy vehicles, automotive lightweighting has become an important issue in the automotive industry. Lightweight vehicles will reduce energy demand and improve vehicle safety. Currently, the development of lightweighting mainly focuses on two directions: replacing traditional sheet metal with lightweight sheet metal such as aluminum-magnesium alloys and reducing sheet metal thickness using high-strength sheets.

[0003] Aluminum-magnesium alloys, as excellent and inexpensive lightweight materials, have been highly favored in the development of the automotive industry. However, their application range and effectiveness are significantly limited by their poor ductility, high springback, difficulty in forming, and material strength issues. Although new aluminum-magnesium alloys with high yield strength are constantly emerging, their poor formability still prevents their widespread application. The main factors restricting their forming are threefold:

[0004] On the one hand, there is the influence of the cold pressure forming mode of the mold. Because the machine tool can only move up and down and is mostly single-action in cold stamping forming, that is, there is an air ejector rod on the lower die to provide pressure for the blank holder ring. In order to ensure the forming control of the material, a large process supplement is required to make the blank holder ring move from the highest point of forming to the lowest point of forming, and to make it approximately flat to ensure the initial state of the material. This results in a lot of process supplements for adjusting the drawing angle. The process supplements continuously increase the drawing depth, which makes it more difficult to form lightweight materials such as aluminum and magnesium alloys, and sometimes even impossible to form them.

[0005] The second aspect is the influence of product shape. As the aesthetics, novelty and mechanical performance of vehicles increase, the shape of automotive body panels is becoming more and more complex, and the curvature and depth are also increasing. Considering the forming performance of materials, it is necessary to select appropriate stamping angles to supplement the process of automotive body panels to ensure that the materials can be formed.

[0006] Thirdly, the material's ductility, resilience, and compressive strength also play a role. Aluminum-magnesium alloy sheets have poor ductility, and high-strength aluminum-magnesium alloy materials have a series of cold stamping forming problems such as poor ductility, strong resilience, and difficulty in secondary forming, which makes it impossible to perform high-ductility forming.

[0007] In summary, the deep cavity cold stamping forming of aluminum-magnesium alloy sheets has become a key challenge for the industry. This has led to the need to separate automotive body panels for partition forming and welding, or to simplify the shape at the expense of aesthetics and quality, or even to abandon the application of aluminum-magnesium alloy materials in favor of ordinary sheet materials. Summary of the Invention

[0008] To address the shortcomings in the aforementioned background technology, this invention proposes a mold processing technology for deep cavity forming of aluminum-magnesium alloys with multiple pressing materials, which solves the technical problem that aluminum-magnesium alloy materials cannot be widely applied to automotive body panels.

[0009] The technical solution of this application is as follows:

[0010] A mold processing technology for deep cavity forming of aluminum-magnesium alloys with multiple blanks includes the following steps:

[0011] Step 1, Minimum drawing depth calibration and stamping direction simulation; find the optimal stamping direction for stamping, focusing on two key directions: forming difficulties, concentration of excess margin areas, and minimum height of formed products, to provide a basic calculation basis and main forming layout for subsequent unified handling of difficulties and reduction of deep cavity forming depth;

[0012] Step 2, Forming optimization and forming margin calculation; using the simulated stamping direction as the stamping direction, optimize the product shape, smooth the negative angle area and transition the material flow, smooth the overall shape, then establish a simulated process supplement to form a process model, and perform batch CAE analysis and forming optimization on the model, and process supplement optimization, so that the difficult forming area and the excess margin area are concentrated in the internal area.

[0013] Step 3, Internal pressure material arrangement and replenishment analysis: Delete the deep concave and flattened surfaces in the initial process automotive body panel product model to restore it to a state containing deep concave parts. Then, find scrap areas near the areas of concentrated molding difficulties and excess material in the early stage, drill holes in the scrap areas, and arrange internal pressure material edge rings around the holes to create a material replenishment area inside the automotive body panel product model. This replenishes material in the areas of molding difficulties and excess material, eliminating molding difficulties and excess material problems.

[0014] Step 4: During the material replenishment analysis, if the material replenishment cannot eliminate cracks or make difficult-to-form areas, it is necessary to return to step 1, reselect the stamping direction, and repeat steps 1-3 until the forming difficulties and excess margin problems are eliminated.

[0015] Step 5, Multi-ring design and pressure configuration; Multi-ring design involves designing the blank holder force after forming analysis and establishing the digital model of the automotive body panel product.

[0016] Step 6: Mold processing and assembly;

[0017] Step 7: Staged debugging and zoned voltage regulation;

[0018] Step 8, High-angle pre-dressing and dough improvement;

[0019] Step 9, Margin test correction;

[0020] Step 10: Finished product shipped out.

[0021] Further, step 1 includes the following steps:

[0022] Step 1.1, Constructing the thinnest envelope of the product; Construct the minimum envelope cuboid in the form of the minimum cuboid envelope for the digital model of the automotive body panel product, then extract the mid-plane in the height direction of the cuboid to establish a rectangle, extract the midline in the length and width directions of the rectangle to form the rotation axis in the length and width directions.

[0023] Step 1.2: Rotate the automotive body panel product model sequentially along the longitudinal axis and the width axis of rotation until a position with no negative angle appears, or a position with a single negative angle in a non-critical area is reached. Record this position as the minimum drawing depth. Then, continue to rotate the automotive body panel product model, calibrating the rotation angle range with no negative angle or a single negative angle. When a negative angle appears, continue rotating until a state with no negative angle or a single negative angle reappears. Continue recording the rotation angle range until a full 90 degrees is reached. The recorded rotation angle range with no negative angle or a single negative angle is the usable stamping angle area.

[0024] Step 1.3: Within the stamping angle range, the automotive body panel product model is rotated again along the longitudinal axis and the width axis of rotation, and the concentration of forming difficulties and excess margin areas is preliminarily analyzed. The excess margin areas are concentrated in one or several areas, and there are scrap areas around the excess margin areas. At the same time, the corresponding forming difficulty areas should also coincide with the excess margin areas as much as possible. The direction with the smallest rotation angle at this time is the stamping direction to be simulated.

[0025] Furthermore, step 2 includes the following steps:

[0026] Step 2.1: Smooth and transition the material in the negative corner area. Construct an envelope surface on the negative corner area to enclose it, thereby creating a negative corner-free surface. The envelope surface is the minimum slope from the upper edge to the lower edge of the negative corner area. After the envelope surface is constructed, perform aesthetic optimization and smooth overlap on the envelope surface.

[0027] Step 2.2: Smooth the overall shape transition, smoothing out small islands and areas with small curvature changes in the product.

[0028] Step 2.3, Simulation Process Supplement Establishment. When establishing the simulation process supplement, the first step is to simplify the profile. The deep concave parts in the molding difficulty area and excess margin concentration area analyzed in the previous stage are flattened to form a simplified profile of the automotive body panel product with a shallow concave center. Based on this automotive body panel product, the process supplement is established according to the conventional model to form the process supplement profile. Then, CAE analysis is performed, and the process supplement is optimized based on the CAE analysis results. Other molding difficulties are optimized to obtain the initial process automotive body panel product digital model.

[0029] Furthermore, step 3 includes the following steps:

[0030] Step 3.1, internal pressure material arrangement, which is the arrangement of the internal pressure ring. It is necessary to select the waste area and expand the space as much as possible to maximize the range within the waste area so as to arrange the embedded self-pressure source more flexibly.

[0031] Step 3.2: The internal pressure material should be simplified as much as possible to reduce the difficulty of subsequent debugging and the uncertainty of molding, based on the ability to complete the material supplementation and elimination of the influence of molding difficulties and excess margin areas.

[0032] Step 3.3: Try to use a single round rib arrangement pattern for the drawbars, and avoid square rib locking, stepped ribs, and multi-rib patterns, so as to facilitate excessive adjustment of the drawbars during later debugging.

[0033] Step 3.4: During CAE analysis, perform multiple analyses of the blank holder force, calculating from the minimum blank holder force to the maximum blank holder force multiple times. Select the minimum blank holder force increased by 5%-10% as the blank holder force to form a minimum blank holder force with adjustment margin, so as not to increase the load on the embedded self-pressure source and cause structural problems.

[0034] Step 3.5, Material replenishment analysis: Taking the largest cracked area analyzed in conventional processes as the center, continuously expand the size of the waste material opening for calculation until the largest cracked area is eliminated.

[0035] Furthermore, step 5 includes the following steps:

[0036] Step 5.1: The external blank holder ring adopts a double-ring design, namely an upper die blank holder ring and a lower die blank holder ring. The upper die blank holder ring adopts an embedded self-pressure source mode. The embedded self-pressure source can use a nitrogen cylinder to solve the self-pressure problem of the upper ring. The external double ring adopts a drawing bead + adjustment bead mode.

[0037] Step 5.2, the movement sequence of the outer pressure ring and the inner pressure ring is consistent; the upper die pressure ring of the inner pressure ring also adopts the embedded pressure source design mode, but the formation of the inner pressure ring needs to be 5-25mm lower than the outer pressure ring to ensure that the outer pressure ring presses the material first.

[0038] Step 5.3, Pressure Configuration; Pressure configuration refers to the pressure configuration of the embedded pressure source and the coordination of pressure between the external and internal pressure rings; the external and internal pressure rings of the lower die are configured and allocated directly according to the pressure configuration and air ejector distribution pattern of conventional die pressure rings; when configuring the pressure of the external pressure ring of the upper die, select an appropriate number of nitrogen cylinders for configuration, and the upper die pressure ring of the internal pressure ring needs to be configured with a larger range.

[0039] Furthermore, when performing the mold processing and assembly in step 6, in terms of processing accuracy, ultra-precision machining is added to ensure higher surface finish and continuity; in terms of consistency, the upper mold and the outer and inner pressure rings of the upper mold need to be processed as a whole during precision machining and ultra-precision machining to avoid overlapping problems caused by processing of separate parts. The lower mold and the outer and inner pressure rings of the lower mold are processed in the same way.

[0040] Furthermore, step 7 is performed during the mold manufacturing debugging stage to ensure the conformity of the actual mold movement state and the comprehensiveness of the molding. Due to the multi-pressure ring mode, timing errors can occur, causing automotive body panels to fail to be molded, or even resulting in mold damage. The main reasons are pressure imbalance, pressure misalignment, and pressure imbalance. Pressure imbalance is mainly caused by excessive pressure on the outer pressure ring of the upper mold, preventing the air ejector rod from lifting, resulting in direct molding without upper mold control and causing molding imbalance. Pressure misalignment occurs when the movement trajectories of the outer and inner pressure rings are inconsistent, with the inner pressure ring being higher than the outer pressure ring, causing material folding and preventing molding. Pressure imbalance occurs because the pressure rings are under unbalanced force, causing tilting during movement, preventing molding or jamming the cavity, resulting in mold damage. Therefore, a step-by-step debugging and zone-based pressure adjustment method is used to eliminate these problems.

[0041] Furthermore, step 7 includes the following steps:

[0042] Step 7.1, phased debugging: First, reduce the pressure of all embedded pressure sources to 85% of the theoretical limit using the pressure pack of the pressure ring. At the same time, increase the pressure adjustment pads of all pressure rings by 2mm to conduct molding experiments and check the consistency of movement and its conformity with the theoretical movement state. Then, gradually increase the pressure in increments of 3% each time. When inconsistencies occur, adjust the arrangement of the lower mold ejector rods and reduce the pressure increase of the inner pressure ring pressure pack until the movement state is consistent. Then, continue to adjust the pressure in the same increment until it reaches or slightly exceeds the theoretical pressure limit to initially solve the problems of pressure imbalance and pressure disorder.

[0043] Step 7.2: When a pressure imbalance occurs during the staged commissioning process, it is necessary to adjust the position of the nitrogen cylinder or add a pressure regulating pad to the lower nitrogen cylinder to eliminate the pressure imbalance problem.

[0044] Step 7.3, zoned voltage adjustment is a method of gradually reducing the height of the voltage regulating pad after staged debugging to ensure the overall shape is in place.

[0045] Furthermore, when performing step 8, pre-cutting is performed on the large-area abrupt fillet, either directly during mold processing or during the initial debugging stage.

[0046] Further, step 9 involves testing the blank holder force by increasing or decreasing it to confirm the acceptable blank holder force range. This is done by starting with a 10T reduction in the normal blank holder force as a starting point for the molding experiment, then increasing the blank holder force by 5T increments until the blank holder force reaches 20% of the designed blank holder force. The stable molding pressure area is then checked, and any defective conditions are adjusted and corrected to expand the molding margin, improve the adaptability of the mold to interchangeable machine tools, and enhance the durability of the mold application. When simultaneous pressure increases and decreases cannot correct molding defects, molding margin tests are performed on each internal blank holder ring at 3T increments, and molding defects are adjusted and corrected to further expand the molding margin and increase the tolerance for molding consistency. Finally, the median value of the pressure range used to obtain a good automotive body panel is rounded down as the final calibrated blank holder force.

[0047] Compared with existing technologies, the mold processing technology for deep cavity forming of aluminum-magnesium alloys provided by this invention is based on CAE analysis and innovative integration of craftsmanship experience. It optimizes forming by simulating changes in stamping direction and adjusting areas with high forming margins. Through an embedded self-pressure source-assisted blank holder mode, it opens up scrap areas in areas with high forming margins and uses a multi-blade mode to internally add material, eliminating the influence of forming difficulties and high forming margins. An external double blank holder mode solves the problem of the blank holder area needing to be at the bottom of the forming surface in conventional forming methods. Innovative debugging and surface quality improvement modes reduce the height of deep cavity forming and overcome forming difficulties and high forming margins, thus achieving low-cost, high-material-utilization deep cavity forming of aluminum-magnesium alloys. This invention is applicable to deep cavity forming of aluminum-magnesium sheets, aluminum sheets, magnesium-aluminum sheets, and other difficult-to-form sheets. The sheet thickness used in the experiment was 0.5-2mm.

[0048] The beneficial effects of this invention include:

[0049] 1. This invention solves the problem of single-action cold stamping equipment being unable to perform bidirectional and tiered air presses by embedding a self-pressure source. It successfully utilizes a multi-ring combination mode of external double pressure rings and internal pressure rings to achieve multi-motion material pressing, thereby significantly reducing the cavity depth of deep-cavity automotive body panel forming and reducing the amount of material stretched. This provides a technical depth reduction mode for deep cavity forming of aluminum-magnesium alloys, enabling deep cavity forming of high-yield-strength aluminum-magnesium alloys. It also provides a replicable mode for forming other lightweight materials, offering a new technical solution for deep cavity forming of lightweight materials and promoting the low-cost and rapid application of lightweight materials.

[0050] 2. The multi-pressure ring mode significantly reduces the material requirements in the process replenishment area by reducing the molding depth. Experiments have shown that it can improve material utilization by 5%-25%, which can significantly reduce the material cost of automotive body panels in the later stage; providing a mature technical solution for low cost and high quality.

[0051] 3. The method of concentrating the difficult forming area and the excess forming area and adding material through the internal pressure edge ring provides a brand-new technical solution for forming products with insufficient forming margin. It can significantly expand the material forming margin and provide an excellent technical solution for expanding the material margin of cold stamping, thereby helping to reduce the process and cost of forming lightweight complex parts and merging parts.

[0052] 4. Adding a pressure pack solves the problem of pressure decay in mold application pressure components, greatly improves mold durability, and provides a stable manufacturing mode for mass automated manufacturing. Attached Figure Description

[0053] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0054] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the core concept of the present invention and the following embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0056] To address the technical problems mentioned in the background section, this invention conducts multi-batch comprehensive cold stamping performance tests on high yield strength aluminum-magnesium alloy materials, disassembles and analyzes the functions of each module of the mold forming process, performs repeatability experiments, and continuously optimizes and corrects the forming and stress simulation capabilities of CAE analysis; and innovatively develops a multi-pressure deep cavity forming technology for aluminum-magnesium alloys.

[0057] This invention utilizes minimum stretch calibration and stamping direction optimization to aggregate the over-forming margin range, thereby optimizing and reducing the forming cavity depth. It supplements the over-forming margin area with additional material through scrap zone opening and internal pressure core mode; innovatively applies an embedded self-pressure source to assist forming pressure mode, achieving self-pressure internal pressure forming; and further reduces forming depth through an embedded self-pressure source-assisted multi-ring pressure mode. It ensures the forming perfection and accuracy of each area through staged debugging and zoned pressure adjustment, and improves product dimensional accuracy and surface quality through high-angle pre-cutting and surface enhancement. This comprehensively enhances craftsmanship and high-end technology; significantly reduces deep cavity forming depth, changes the mold forming mode to greatly release forming space, and, based on significantly reducing process supplementation and improving material utilization, enables high-yield-strength deep cavity forming of high-quality aluminum-magnesium alloy materials. This allows for the low-cost, high-utilization application of aluminum-magnesium alloy materials in the automotive body panel field; provides excellent technical solutions for the high-quality, large-scale application of aluminum-magnesium alloys; and provides technical support for the application of new materials and significant cost reduction in automobiles.

[0058] A mold processing technology for multi-pressure deep cavity forming of aluminum-magnesium alloys, such as... Figure 1 As shown, it includes the following steps:

[0059] 1. Minimum drawing depth calibration and stamping direction simulation: This mainly involves finding the optimal stamping direction for forming, focusing on two key directions: the concentration of forming difficulties and excess margin areas, and the lowest possible height of the formed product. This provides a basic calculation basis and main forming layout for subsequent unified handling of difficulties and reduction of deep cavity forming depth. The specific method is as follows:

[0060] 1.1 Construction of the thinnest envelope of the product: The minimum envelope cuboid is constructed in the form of the minimum cuboid envelope for the digital model of the automotive body panel product. Then, the mid-plane in the height direction of the cuboid is extracted to establish a rectangle. The center lines in the length and width directions of the rectangle are extracted to form the rotation axes in the length and width directions.

[0061] 1.2. Rotate the automotive body panel product numeral (hereinafter referred to as numeral) sequentially along the longitudinal axis and the width axis of rotation until a numeral without negative angles appears, or a numeral with a single negative angle in a non-critical area is placed. Record this position as the minimum drawing depth. Then, continue to rotate the numeral, calibrating the rotation angle range of no negative angle or single negative angle. When a negative angle appears on the product, continue to rotate. After the state of no negative angle or single negative angle appears again, continue to record the rotation angle range until it reaches 90 degrees. The rotation angle range of no negative angle or single negative angle recorded at this time is the stamping angle usable area.

[0062] 1.3 Within the stamping angle range, the digital model is rotated again along the longitudinal axis and the width axis of rotation, and the concentration of forming difficulties and excess margin areas is preliminarily analyzed. The excess margin areas are concentrated in one or a few areas (the number should be as small as possible), and there are scrap areas around the excess margin areas. At the same time, the corresponding forming difficulty areas should also coincide with the excess margin areas as much as possible (generally, except for complex forming shapes at the edges and corners, the excess margin areas and the difficulty areas are consistent, and the forming difficulties of edge and corner load shapes are not related to deep cavity forming and can be solved in other ways). The direction with the smallest rotation angle at this time is the stamping direction to be simulated.

[0063] 2. Forming optimization and forming margin calculation: Taking the stamping direction to be simulated as the stamping direction, optimize the product shape, smooth the negative angle area and transition the material flow, and smooth the overall shape. Then, establish a simulated process supplement to form a process model, and perform batch CAE analysis and forming optimization on the model. The process supplement optimization will concentrate the difficult forming area and the excess margin area in the internal area. The specific method is as follows:

[0064] 2.1 For the negative angle area, smoothing and material flow are necessary. Because cold stamping of the mold involves simple linear up-and-down movement, negative angles are not allowed, as they would cause mold interference and render the mold unusable. Therefore, an enveloping surface is constructed on the negative angle area to envelop it, thus creating a negative angle-free surface. The enveloping surface is the minimum slope from the upper edge to the lower edge of the negative angle area. After the enveloping surface is constructed, it is aesthetically optimized and smoothly overlapped to enhance the product's appearance and eliminate the molding problems caused by the enveloping surface.

[0065] 2.2 Smooth transition of overall shape mainly involves smoothing small islands and areas with small curvature changes in the product to reduce molding and adjustment difficulties. The principle of smoothing is that, on the one hand, the shape can be corrected in the later shaping process, and on the other hand, it is necessary to avoid the formation of slippage areas that may affect the product.

[0066] 2.3. Simulation process supplementation establishment: When establishing the simulation process supplementation, the first step is to simplify the surface. The deep concave parts in the molding difficulty area and the excess margin concentration area analyzed in the previous stage (this part is generally the maximum excess margin area, so it can be ignored in this step and the influence of the pressure ring downward movement can be eliminated by flattening) are flattened to form a simplified surface model with a shallow concave center. Based on this surface model, the process supplementation is established according to the conventional mode to form the process supplementation surface. Then, CAE analysis is performed, and the process supplementation is optimized according to the analysis results. Other molding difficulties are optimized to obtain the initial process surface model.

[0067] 3. Internal pressure material arrangement and replenishment analysis: The deep concave and flattened surfaces in the initial process model are deleted, restoring it to a state containing the deep concave portion. Then, waste material areas are located near the concentrated molding difficulties and excess material areas from the early stages. Holes are drilled within these waste material areas, and internal pressure material retainers are arranged around the holes to create a material replenishment area within the model. This replenishes material in the molding difficulty and excess material areas, eliminating molding difficulties and excess material problems. The key points of this step are as follows:

[0068] 3.1 Internal pressure material arrangement: The internal pressure material arrangement refers to the arrangement of the internal pressure ring. It is necessary to select the waste area and expand the space as much as possible to maximize the range within the waste area so as to arrange the embedded self-pressure source more flexibly.

[0069] 3.2 The internal pressure material should be simplified as much as possible to reduce the difficulty of subsequent debugging and the uncertainty of molding, while being able to complete the material supplementation and elimination of the influence of molding difficulties and excess margin areas.

[0070] 3.3. Try to use a single round bar arrangement pattern for the drawbars, and avoid square bar locking, stepped bar, and multi-bar patterns, so as to facilitate excessive adjustment of the drawbars during later debugging.

[0071] 3.4 During CAE analysis, perform multiple analyses of the blank holder force, calculating from the minimum blank holder force to the maximum blank holder force multiple times. Select the minimum blank holder force by increasing it by 5%-10% to form a minimum blank holder force with adjustment margin, so as not to increase the load of the embedded self-pressure source and cause structural problems.

[0072] 3.5, Material replenishment analysis: Taking the largest cracked area analyzed in conventional processes as the center, the size of the waste material opening is continuously increased for calculation until the largest cracked area is eliminated.

[0073] 4. During the material replenishment analysis, if cracking and difficult-to-form areas cannot be eliminated regardless of the material replenishment process, it is necessary to return to step 1, reselect the stamping direction, and repeat steps 1-3 until the forming difficulties and excess allowance issues are eliminated. Only then can the next step be proceeded.

[0074] 5. Multi-ring design and pressure configuration; Multi-ring design mainly involves designing the blank holder force using technical means after molding analysis and establishing the process digital model. Because the multi-ring structure is an innovation of the traditional structure, the overall mold forming motion mode and motion mechanism have changed. Therefore, the motion mode and force conditions need to be changed during the design. First, the double-ring pressing of the upper and lower dies of the outer blank holder solves the problem of the upper die protrusion contacting the material first and failing to form due to the lower cavity and higher blank holder position caused by the lowering of the cavity and the raising of the blank holder position. However, it also causes the influence of the double-ring motion mode on the forming motion. At the same time, the matching of the motion of the outer blank holder and the consistency of the motion sequence must be considered. Otherwise, the inconsistency of motion will cause the inability to form. The specific methods are as follows:

[0075] 5.1 The external blank holder ring adopts a double-ring design, namely an upper die blank holder ring and a lower die blank holder ring. This avoids the problem of the upper die protrusion contacting the material before the blank holder ring due to the raised blank holder position, which would prevent molding. This reduces the overall molding depth and significantly reduces the amount of material supplemented in the process, improving material utilization and reducing costs. However, the overall molding motion changes during bidirectional pressing, resulting in the simultaneous molding of the upper and lower die protrusions, increasing the molding difficulty. Moreover, the upper die position of a typical single-action press generally lacks an ejector pin and cannot provide differential pressure. Therefore, the blank holder ring of the upper die adopts a double-ring design. The embedded self-pressure source mode can use elastic components such as nitrogen cylinders (standard parts) to solve the problem of self-pressure of the upper ring; at the same time, in order to solve the problem of simultaneous bidirectional forming of the upper and lower dies, the outer double ring is designed with draw beads and adjustment ribs. The draw beads are designed according to the normal mold design state; the adjustment ribs are located near the maximum forming sliding area and the bidirectional contact area, and their length is designed according to the area length + 30mm. The center of the rib is 25-30mm outside the normal draw bead, and the height of the rib is half the height of the normal draw bead, so as to adjust the feeding during later debugging.

[0076] 5.2 The movement sequence of the outer and inner pressure rings is consistent; the upper pressure ring of the inner pressure ring also adopts the embedded pressure source design mode, but the formation of the inner pressure ring needs to be 5-25mm lower than that of the outer pressure ring to ensure that the outer pressure ring presses the material first; at the same time, in order to ensure that the operation of the inner pressure ring is consistent with the later movement of the outer ring, the upper and lower pressure of the inner ring needs to be less than that of the outer ring, and there should be a larger space, so pressure configuration is required.

[0077] 5.3 Pressure Configuration; Pressure configuration mainly involves the pressure configuration of the embedded self-pressure source and the coordination of pressure between the external and internal pressure rings; Since the external and internal pressure rings of the lower die are driven by the air ejector rod of the pressure equipment, they can be configured and allocated directly according to the conventional pressure configuration and air ejector distribution pattern of the pressure rings of the mold; When configuring the pressure of the external pressure ring of the upper die, it is necessary to select an appropriate number of nitrogen cylinders according to the pressure force between 1.1 and 1.2 (because the pressure of nitrogen cylinders has standard limits, the configuration pressure has a range). The upper die pressure ring of the internal pressure ring needs to be configured within a larger range, selecting an appropriate number of nitrogen cylinders according to the range of 1.2-1.4; At the same time, in order to ensure the consistency of the timing movement when all pressure rings move, it is necessary to connect the nitrogen cylinders of each pressure ring in series and add an external pressure pack to adjust the pressure and maintain durability.

[0078] 6. Mold processing and assembly: Due to the difficulty in forming lightweight materials and the multi-faceted fit of the mold, corresponding improvements are needed on the basis of conventional processing and assembly during mold processing and assembly. In terms of processing accuracy, ultra-precision machining is required to ensure higher surface finish and continuity. In terms of consistency, the upper mold and its outer and inner pressure rings need to be processed as a whole during precision and ultra-precision machining to avoid overlapping problems caused by processing of separate parts. The lower mold and its outer and inner pressure rings are processed in the same way.

[0079] 7. Step-by-step debugging and zoned pressure adjustment; This process is mainly carried out during the debugging stage of mold manufacturing. Its main purpose is to ensure the conformity of the actual mold movement state and the comprehensiveness of molding. Traditional single-blade ring molds only need to adjust the adaptability of the blank holder force and the molding margin. However, in the multi-blade ring mode, timing disorder problems will occur, causing automotive body panels to fail to be molded, or even mold damage. The main reasons are pressure imbalance, pressure disorder, and pressure imbalance. Pressure imbalance is mainly caused by excessive pressure on the upper mold's outer blank holder ring, causing the air ejector rod to fail to lift, resulting in direct molding without upper mold control and forming imbalance. Pressure disorder is caused by inconsistent movement trajectories between the outer and inner blank holder rings, with the inner blank holder ring being higher than the outer blank holder ring, causing material folding and failure to be molded. Pressure imbalance is caused by the unbalanced force on the blank holder rings, resulting in tilting during movement, failure to be molded, or jamming of the cavity, causing mold damage. Therefore, step-by-step debugging and zoned pressure adjustment are needed to eliminate the above problems. The specific methods are as follows:

[0080] 7.1 Step-by-step debugging: First, reduce the pressure of all embedded pressure sources to 85% of the theoretical limit using the pressure pack of the pressure ring. At the same time, increase the pressure adjustment pads of all pressure rings by 2mm to conduct molding experiments and check the consistency of motion and its conformity with the theoretical motion state. Then, gradually increase the pressure in increments of 3% each time. When inconsistencies occur, adjust the arrangement of the lower mold ejector rods and reduce the pressure increase of the inner pressure ring pressure pack until the motion state is consistent. Then, continue to adjust the pressure in the same increment until it reaches or slightly exceeds the theoretical pressure limit to initially solve the problems of pressure imbalance and pressure disorder.

[0081] 7.2 When a pressure imbalance occurs during the staged commissioning process, it is necessary to adjust the position of the nitrogen cylinder or add a pressure regulating pad to the lower nitrogen cylinder to eliminate the pressure imbalance problem.

[0082] 7.3 Zoned Pressure Adjustment; Zoned pressure adjustment is a method of gradually reducing the height of the pressure adjustment pads after staged debugging to achieve the overall molding. The main steps are as follows: First, the pressure adjustment pads of the outer pressure ring are gradually lowered in increments of 0.5mm to check the molding performance and movement. When poor movement or molding occurs, the height of the pressure adjustment pads in different areas is adjusted in the same way as the normal molding mode to ensure the molding effect. After the pressure adjustment of the outer pressure ring is completed, the pressure of the inner pressure ring is adjusted in descending order until the molding is normal.

[0083] 8. High-angle pre-cutting and surface quality improvement: This step mainly solves product quality problems such as warping caused by the release of material stress during the molding of lightweight materials and warping caused by multiple rounds of mold lifting. The specific method is to pre-cut the large-area abrupt rounded corners. Pre-cutting can be done directly during mold processing or in the early stage of debugging. The method is to start from 5mm inward from the upper edge of the convex rounded corner of the abrupt surface and end at the top line of the convex rounded corner, and make a 0-0.05mm gradual pre-cutting to offset the molding warping and achieve the purpose of excellent surface quality.

[0084] 9. Margin Test Correction: The margin test correction involves increasing or decreasing the blank holder force to confirm the acceptable blank holder force range. The method is to start with a molding experiment by reducing the normal blank holder force by 10T, then increase the blank holder force by 5T increments until the blank holder force reaches 20% of the design blank holder force. Then, check the stable molding pressure area and adjust and correct any defective conditions to expand the molding margin, improve the adaptability of the mold to interchangeable machine tools, and enhance the durability of the mold application. When simultaneous pressure increases and decreases cannot correct molding defects, perform a molding margin test of 3T increments on each internal blank holder and adjust and correct any molding defects to further expand the molding margin and increase the tolerance for molding consistency. Finally, the median value of the pressure range used to obtain a good automotive body panel is rounded down as the final calibrated blank holder force.

[0085] 10. Finished product; After the entire process is completed, the mold will meet the factory requirements. After appearance treatment and finishing, it can be shipped as a finished product.

[0086] All aspects not detailed in this invention are conventional technical means known to those skilled in the art.

[0087] The above content shows and describes the basic principles, main features, and beneficial effects of the present invention. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A mold processing technology for deep cavity forming of aluminum-magnesium alloy multi-pressure blanks, characterized in that... Includes the following steps: Step 1, Minimum drawing depth calibration and stamping direction simulation; find the optimal stamping direction for stamping, focusing on two key directions: forming difficulties, concentration of excess margin areas, and minimum height of formed products, to provide a basic calculation basis and main forming layout for subsequent unified handling of difficulties and reduction of deep cavity forming depth; Step 2, Forming optimization and forming margin calculation; Using the simulated stamping direction as the stamping direction, optimize the product shape, smooth the negative angle area and the material flow transition, smooth the overall shape, then establish a simulated process supplement to form a process model, and perform batch CAE analysis and forming optimization on the model, thereby concentrating the difficult forming area and the excess margin area in the internal area. Step 3, Internal pressure material arrangement and replenishment analysis: Delete the deep concave and flattened surfaces in the initial process automotive body panel product model to restore it to a state containing deep concave parts. Then, find scrap areas near the areas of concentrated molding difficulties and excess material in the early stage, drill holes in the scrap areas, and arrange internal pressure material edge rings around the holes to create a material replenishment area inside the automotive body panel product model. This replenishes material in the areas of molding difficulties and excess material, eliminating molding difficulties and excess material problems. Step 4: During the material replenishment analysis, if the material replenishment cannot eliminate cracks or make difficult-to-form areas, it is necessary to return to step 1, reselect the stamping direction, and repeat steps 1-3 until the forming difficulties and excess margin problems are eliminated. Step 5, Multi-ring design and pressure configuration; Multi-ring design involves designing the blank holder force after forming analysis and establishing the digital model of the automotive body panel product. Step 6: Mold processing and assembly; Step 7: Staged debugging and zoned voltage regulation; Step 8, High-angle pre-dressing and dough improvement; Step 9, Margin test correction; Step 10: Finished product shipped out; Step 1 includes the following steps: Step 1.1, Constructing the thinnest envelope of the product; Construct the minimum envelope cuboid in the form of the minimum cuboid envelope for the digital model of the automotive body panel product, then extract the mid-plane in the height direction of the cuboid to establish a rectangle, extract the midline in the length and width directions of the rectangle to form the rotation axis in the length and width directions. Step 1.2: Rotate the automotive body panel product model sequentially along the longitudinal axis and the width axis of rotation until a position with no negative angle appears, or a position with a single negative angle in a non-critical area is reached. Record this position as the minimum drawing depth. Then, continue to rotate the automotive body panel product model, calibrating the rotation angle range with no negative angle or a single negative angle. When a negative angle appears, continue rotating until a state with no negative angle or a single negative angle reappears. Continue recording the rotation angle range until a full 90 degrees is reached. The recorded rotation angle range with no negative angle or a single negative angle is the usable stamping angle area. Step 1.3: Within the stamping angle range, rotate the automotive body panel product model sequentially along the longitudinal axis and the width axis of rotation, and preliminarily analyze the concentration of forming difficulties and excess margin areas. Find the excess margin areas concentrated in one or several areas, and find the waste areas around the excess margin areas. At the same time, the forming difficulty area coincides with the excess margin area. The direction with the smallest rotation angle at this time is the stamping direction to be simulated.

2. The mold processing technology for deep cavity forming of aluminum-magnesium alloy multi-pressure material according to claim 1, characterized in that: Step 2 includes the following steps: Step 2.1: Smooth and transition the material in the negative corner area. Construct an envelope surface on the negative corner area to enclose it, thereby creating a negative corner-free surface. The envelope surface is the minimum slope from the upper edge to the lower edge of the negative corner area. After the envelope surface is constructed, perform aesthetic optimization and smooth overlap on the envelope surface. Step 2.2: Smooth the overall shape transition, smoothing out small islands and areas with small curvature changes in the product. Step 2.3, Simulation Process Supplement Establishment. When establishing the simulation process supplement, the first step is to simplify the profile. The deep concave parts in the molding difficulty area and excess margin concentration area analyzed in the previous stage are flattened to form a simplified profile of the automotive body panel product with a shallow concave center. Based on this automotive body panel product, the process supplement is established according to the conventional model to form the process supplement profile. Then, CAE analysis is performed, and the process supplement is optimized based on the CAE analysis results. Other molding difficulties are optimized to obtain the initial process automotive body panel product digital model.

3. The mold processing technology for deep cavity forming of aluminum-magnesium alloy multi-pressure material according to claim 1, characterized in that: Step 3 includes the following steps: Step 3.1, internal pressure material arrangement, which is the arrangement of the internal pressure ring. It is necessary to select the waste area and expand the space to maximize its range within the waste area so as to arrange the embedded self-pressure source more flexibly. Step 3.2: Based on the ability to supplement and eliminate the influence of materials in the difficult and excessive areas of molding, the shape of the internal pressure material is simplified to reduce the difficulty of subsequent debugging and the uncertainty of molding. Step 3.3 adopts a single round rib arrangement pattern for the drawbars to avoid square rib locking, stepped ribs, and multi-rib patterns, so as to facilitate excessive adjustment of the drawbars during later debugging. Step 3.4: During CAE analysis, perform multiple analyses of the blank holder force, calculating from the minimum blank holder force to the maximum blank holder force multiple times. Select the minimum blank holder force increased by 5%-10% as the blank holder force to form a minimum blank holder force with adjustment margin, so as not to increase the load on the embedded self-pressure source and cause structural problems. Step 3.5, Material replenishment analysis: Taking the largest cracked area analyzed in conventional processes as the center, continuously expand the size of the waste material opening for calculation until the largest cracked area is eliminated.

4. The mold processing technology for deep cavity forming of aluminum-magnesium alloy multi-pressure material according to claim 1, characterized in that: Step 5 includes the following steps: Step 5.1: The external blank holder ring adopts a double-ring design, namely an upper die blank holder ring and a lower die blank holder ring. The upper die blank holder ring adopts an embedded self-pressure source mode. The embedded self-pressure source can use a nitrogen cylinder to solve the self-pressure problem of the upper ring. The external double ring adopts a drawing bead + adjustment bead mode. Step 5.2, the movement sequence of the outer pressure ring and the inner pressure ring is consistent; the upper die pressure ring of the inner pressure ring also adopts the embedded pressure source design mode, but the formation of the inner pressure ring needs to be 5-25mm lower than the outer pressure ring to ensure that the outer pressure ring presses the material first. Step 5.3, Pressure Configuration; Pressure configuration refers to the pressure configuration of the embedded pressure source and the coordination of pressure between the external and internal pressure rings; the external and internal pressure rings of the lower die are configured and allocated directly according to the pressure configuration and air ejector distribution pattern of conventional die pressure rings; when configuring the pressure of the external pressure ring of the upper die, select an appropriate number of nitrogen cylinders for configuration, and the upper die pressure ring of the internal pressure ring needs to be configured with a larger range.

5. The mold processing technology for multi-pressure deep cavity forming of aluminum-magnesium alloys according to any one of claims 1-4, characterized in that: When performing step 6 of mold processing and assembly, in terms of processing accuracy, ultra-precision machining is added to ensure higher surface finish and continuity; in terms of consistency, the upper mold and the outer and inner pressure rings of the upper mold need to be processed as a whole during precision machining and ultra-precision machining to avoid overlapping problems caused by processing of separate parts. The lower mold and the outer and inner pressure rings of the lower mold are processed in the same way.

6. The mold processing technology for multi-pressure deep cavity forming of aluminum-magnesium alloys according to claim 5, characterized in that: Step 7 is performed during the mold manufacturing debugging stage to ensure the conformity of the actual mold movement state and the comprehensiveness of the molding; the above problems are eliminated by using step-by-step debugging and zone pressure adjustment.

7. The mold processing technology for multi-pressure deep cavity forming of aluminum-magnesium alloys according to claim 6, characterized in that: Step 7 includes the following steps: Step 7.1, phased debugging: First, reduce the pressure of all embedded pressure sources to 85% of the theoretical limit using the pressure pack of the pressure ring. At the same time, increase the pressure adjustment pads of all pressure rings by 2mm to conduct molding experiments and check the consistency of movement and its conformity with the theoretical movement state. Then, gradually increase the pressure in increments of 3% each time. When inconsistencies occur, adjust the arrangement of the lower mold ejector rods and reduce the pressure increase of the inner pressure ring pressure pack until the movement state is consistent. Then, continue to adjust the pressure in the same increment until it reaches or slightly exceeds the theoretical pressure limit to initially solve the problems of pressure imbalance and pressure disorder. Step 7.2: When a pressure imbalance occurs during the staged commissioning process, it is necessary to adjust the position of the nitrogen cylinder or add a pressure regulating pad to the lower nitrogen cylinder to eliminate the pressure imbalance problem. Step 7.3, zoned voltage adjustment is a method of gradually reducing the height of the voltage regulating pad after staged debugging to ensure the overall shape is in place.

8. The mold processing technology for deep cavity forming of aluminum-magnesium alloy multi-pressure material according to any one of claims 1-4 and 6-7, characterized in that: When performing step 8, pre-minimize large-area abrupt fillet fillets, either by pre-minimizing during mold processing or by correcting the mint fillets during the initial debugging phase.

9. The mold processing technology for deep cavity forming of aluminum-magnesium alloy multi-pressure material according to claim 8, characterized in that: Step 9 involves testing the blank holder force by increasing or decreasing it to confirm the acceptable blank holder force range. The method is to start with a forming experiment by reducing the normal blank holder force by 10T, and then increase the blank holder force by 5T each time until the blank holder force of the blank holder ring increases to 20% of the designed blank holder force. Then check the stable pressure area of ​​molding, and then adjust and correct the defective state to expand the molding margin, improve the adaptability of the mold interchange machine tool and the durability of the mold application; when the molding defect cannot be corrected by simultaneously raising and lowering the pressure, perform a molding margin test of 3T each time on the internal pressure ring and adjust and correct the molding defect. To further expand the molding margin and increase the tolerance rate for molding consistency, the final calibrated blank holder force is then rounded down to the median of the pressure range that ultimately yields a good automotive body panel.

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