A method of forming an aluminum alloy housing of varying wall thickness

Abstract

The present application relates to the technical field of metal plasticity, in particular to a forming method of aluminum alloy shell with different wall thicknesses, comprising the following steps: providing aluminum alloy sheet; stamping forming the aluminum alloy sheet in a stamping die, the stamping die comprising a punch assembly and a die assembly matched with the punch assembly, the punch assembly comprising a first punch segment corresponding to a thick wall area of the shell and a second punch segment corresponding to a thin wall area of the shell, and the forming end surface of the first punch segment protruding a first distance relative to the forming end surface of the second punch segment in the die closing direction. Through the differential design of the forming surface height of the punch assembly and the die assembly, that is, the protrusion of the first punch segment matches the depression of the first die segment, the aluminum alloy shell with thick wall area and thin wall area is directly formed in one die closing stamping action, without subsequent machining or welding, which significantly improves the production efficiency and material utilization.

Description

Technical Field

[0001] This invention relates to the field of metal plasticity technology, specifically a method for forming aluminum alloy shells with different wall thicknesses. Background Technology

[0002] Aluminum alloy housings are widely used in new energy vehicle battery packs, motor controllers, electronic device heat sinks, and aerospace structural components due to their advantages such as low density, high specific strength, good thermal conductivity, and corrosion resistance. With the increasing demand for lightweight and integrated product design, structural forms that simultaneously contain thick-walled and thin-walled areas on a single housing are becoming increasingly common. For example, new energy vehicle battery pack housings require thick-walled areas in load-bearing parts such as mounting lugs and reinforcing ribs to ensure structural strength, while large-area coverage areas are designed as thin-walled areas to reduce weight; motor housings require thickening at the junction box mounting base and thinning at the base of the heat sink fins.

[0003] Currently, the main methods for manufacturing aluminum alloy shells with different wall thicknesses include the following: Casting. High-pressure casting or squeeze casting processes are used to directly form shells of varying wall thicknesses through mold cavity design. However, during aluminum alloy casting, thick-walled areas solidify slowly, easily leading to internal defects such as shrinkage cavities and porosity; thin-walled areas, due to difficulties in filling the mold, are prone to surface defects such as cold shuts and incomplete filling. When the wall thickness difference is significant, the difference in solidification shrinkage between the thick-walled and thin-walled areas results in severe shell deformation, making it difficult to guarantee dimensional accuracy. Furthermore, the mechanical properties of cast aluminum alloys are generally lower than those of wrought aluminum alloys, making it difficult to meet the requirements for high-strength load-bearing shells.

[0004] Machining method. First, a blank of uniform wall thickness is prepared by casting or extrusion, then excess material is removed by CNC milling to obtain different wall thicknesses. This method has extremely low material utilization, long processing cycle, and high production cost. Furthermore, the machining process damages the streamline structure of the aluminum alloy, weakening the fatigue performance of the shell.

[0005] Welding method. Thick-walled and thin-walled plates, formed separately, are joined into a single shell by welding. The heat input generated during welding leads to large shell deformation, high residual stress, coarsening of the microstructure in the weld zone, and decreased corrosion resistance. For shells with high airtightness requirements (such as battery pack shells), welding quality is unstable, and leakage rate is difficult to control.

[0006] Spin forming is a method that uses a spinning wheel to apply localized plastic deformation to a rotating blank, thereby reducing wall thickness. However, existing spin forming technology is mainly used for uniform wall thickness reduction in rotating parts or gradual wall thickness changes in simple conical parts, and it is difficult to adapt to aluminum alloy shells with complex non-axisymmetric features. In addition, spin forming has low efficiency, making it uneconomical for mass-produced shells.

[0007] Traditional stamping forming method. This method uses equal-clearance stamping dies to draw or bulge aluminum alloy sheets, obtaining shells with uniform wall depth or uncontrollable wall thickness distribution. Existing stamping dies maintain a consistent clearance between the punch and die across the entire profile, making it impossible to directly form shells with significant wall thickness differences in a single stamping operation. If uneven deformation is forcibly created in different areas of the sheet metal through stamping, thin-walled areas are prone to cracking due to excessive thinning, while thick-walled areas wrinkle due to insufficient deformation, resulting in extremely low forming limits.

[0008] In summary, existing technologies lack an efficient manufacturing method that can directly form aluminum alloy shells of different wall thicknesses through stamping and by utilizing the differentiated design of the mold structure itself. Therefore, it is necessary to provide a new aluminum alloy shell forming method to solve the aforementioned technical problems. Summary of the Invention

[0009] To address the problems in existing technologies, this invention provides a method for forming aluminum alloy shells with different wall thicknesses. This method solves the technical problems of numerous forming defects, low material utilization, low production efficiency, and high cost in the manufacturing of aluminum alloy shells with different wall thicknesses. The method adopts a stamping process and, through the differentiated design of the forming surfaces of the die punch and die assembly, directly forms an aluminum alloy shell with thick and thin wall areas in a single die closing action. It has high forming accuracy, high production efficiency, high material utilization, and is suitable for mass production.

[0010] The technical solution adopted by this invention to solve its technical problem is: a method for forming aluminum alloy shells of different wall thicknesses, comprising the following steps: Aluminum alloy sheets are available; The aluminum alloy sheet is placed in a stamping die for stamping. The stamping die includes a punch assembly and a die assembly that cooperates with the punch assembly. The punch assembly includes a first punch section corresponding to the thick-walled area of ​​the shell and a second punch section corresponding to the thin-walled area of ​​the shell. The forming end face of the first punch section protrudes a first distance relative to the forming end face of the second punch section in the die closing direction. The die assembly includes a first die section corresponding to the thick-walled area and a second die section corresponding to the thin-walled area. The bottom surface of the cavity of the first die section is recessed a second distance relative to the bottom surface of the cavity of the second die section in the die closing direction. The punch assembly and the die assembly are driven to close, and the aluminum alloy sheet is stamped and formed, so that a thick-walled area is formed between the first punch section and the first die section, and a thin-walled area is formed between the second punch section and the second die section. The wall thickness of the thick-walled area is greater than the wall thickness of the thin-walled area, and the difference between the wall thickness of the thick-walled area and the thin-walled area is equal to the sum of the first distance and the second distance.

[0011] The beneficial effects of this invention are: (1) The aluminum alloy shell forming method with different wall thicknesses described in this invention uses the differentiated design of the forming surface height of the punch assembly and the die assembly, that is, the protrusion of the first punch section and the concavity of the first die section are matched. In one die-clamping action, an aluminum alloy shell with thick wall area and thin wall area is directly formed without subsequent machining or welding, which significantly improves production efficiency and material utilization. By setting the third punch section and the third die section with the transition area and adopting the transition slope structure, the wall thickness change between the thick wall area and the thin wall area is smooth and continuous, avoiding stress concentration and discontinuous structure caused by sudden wall thickness, and improving the fatigue life and structural reliability of the shell.

[0012] (2) The aluminum alloy shell forming method with different wall thicknesses described in this invention adopts a modular structure design. Both the punch section and the die section are detachable inserts. By replacing punch inserts of different heights and die inserts of different depths, the wall thickness difference can be quickly adjusted, so that the same set of molds can meet the production needs of shells of various specifications. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0014] Figure 1 A schematic diagram of a forming method for an aluminum alloy shell with different wall thicknesses provided by the present invention; Figure 2 This is a schematic diagram of the molding method with pretreatment provided by the present invention. Detailed Implementation

[0015] The embodiments and descriptions in the specification above are merely illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. Example

[0017] This embodiment provides a method for forming aluminum alloy shells with different wall thicknesses, suitable for manufacturing the lower shell of a new energy vehicle battery pack. The lower shell is rectangular, approximately 1200mm long, 800mm wide, and 150mm deep. The central area at the bottom of the shell is a large thin-walled region, designed with a minimum wall thickness of 1.2mm and a maximum wall thickness of 2.6-2.7mm, to reduce weight. The flange edges around the shell and the mounting lugs at the four corners are thick-walled regions, designed with a wall thickness of 3.0mm to ensure connection strength and load-bearing capacity. A transition zone exists between the thick-walled and thin-walled regions, with the wall thickness gradually decreasing from 3.0mm to 1.2mm, and the transition zone width is 30mm. The wall thickness ratio of the thick-walled to the thin-walled regions is 2.5.

[0018] Reference Figure 1 , Figure 2 The molding method of this embodiment includes the following steps: Step S1: Provide aluminum alloy sheet.

[0019] This embodiment uses 6063-O temper aluminum alloy sheet with a thickness of 3.0 mm and dimensions of 1250 mm × 850 mm. Before supplying the aluminum alloy sheet, it undergoes pretreatment. Local pre-stretching is performed on the corresponding thick-walled areas using a specialized fixture. The pre-stretch deformation is 10%, inducing work hardening in this area and improving deformation resistance. After pretreatment, different areas of the aluminum alloy sheet exhibit differentiated deformation capabilities, creating favorable conditions for subsequent differential wall thickness stamping.

[0020] Step S2: Place the aluminum alloy sheet into a stamping die for stamping and forming.

[0021] The stamping die used in this embodiment includes a punch assembly 100 and a die assembly 200. The punch assembly 100 includes an upper die base 110, an upper backing plate 120, and a punch insert assembly installed below the upper backing plate 120. The punch insert assembly includes a first punch insert 131 corresponding to the thick-walled area of ​​the housing, a second punch insert 132 corresponding to the thin-walled area of ​​the housing, and a third punch insert 133 corresponding to the transition area. The forming end face of the first punch insert 131 protrudes a first distance h1 relative to the forming end face of the second punch insert 132 in the die closing direction, where h1 is 0.9 mm. The forming end face of the third punch insert 133 is a transition slope that gradually decreases in the direction from the thick-walled area to the thin-walled area, gradually changing from h1 = 0.9 mm to 0 mm.

[0022] The die assembly 200 includes a lower die base 210, a lower backing plate 220, and a die insert assembly mounted above the lower backing plate 220. The die insert assembly includes a first die insert 231 corresponding to the thick-walled region, a second die insert 232 corresponding to the thin-walled region, and a third die insert 233 corresponding to the transition region. The bottom surface of the cavity of the first die insert 231 is recessed by a second distance h2 relative to the bottom surface of the cavity of the second die insert 232 in the die closing direction, where h2 is 0.9 mm. The bottom surface of the cavity of the third die insert 233 is a transition slope that gradually decreases in the direction from the thick-walled region to the thin-walled region, gradually changing from h2 = 0.9 mm to 0 mm.

[0023] The first forming gap between the first punch insert 131 and the first die insert 231 is 3.0 mm, the second forming gap between the second punch insert 132 and the second die insert 232 is 1.2 mm, and the transition forming gap between the third punch insert 133 and the third die insert 233 gradually changes from 3.0 mm to 1.2 mm. The wall thickness difference between the thick-walled region and the thin-walled region is 1.8 mm, which is equal to the sum of the first distance h1 (0.9 mm) and the second distance h2 (0.9 mm).

[0024] Each punch insert is fixed to the upper pad 120 by a first wedge block 141 and a first shim group 142, and each die insert is fixed to the lower pad 220 by a second wedge block 241 and a second shim group 242. By adjusting the thickness of the first shim group 142 and the second shim group 242, the first distance h1 and the second distance h2 can be adjusted to meet the production requirements of shells with different wall thickness differences.

[0025] The stamping die also includes a blank holder mechanism. The blank holder mechanism includes an upper blank holder plate 151 and a lower blank holder plate 152. The upper blank holder plate 151 is disposed around the periphery of the punch assembly 100 and is connected to the upper die holder 110 via a first nitrogen spring 161. The lower blank holder plate 152 is disposed around the periphery of the die assembly 200 and is connected to the lower die holder 210 via a second nitrogen spring 162. During die closing, the upper blank holder plate 151 and the lower blank holder plate 152 contact the aluminum alloy sheet before the punch insert assembly and the die insert assembly, applying blank holder force to the aluminum alloy sheet to prevent uneven material flow during stamping, which could lead to wrinkling or wall thickness deviation.

[0026] Step S3: Drive the punch assembly and the die assembly to close the mold and stamp the aluminum alloy sheet.

[0027] The pre-treated aluminum alloy sheet is placed on the die assembly 200, and the stamping equipment is started to drive the punch assembly 100 downward. During the die closing process, the upper pressure plate 151 and the lower pressure plate 152 first contact the aluminum alloy sheet and apply pressure. Subsequently, the first punch insert 131, the second punch insert 132, and the third punch insert 133 contact the aluminum alloy sheet sequentially or simultaneously, causing the aluminum alloy sheet to undergo differentiated plastic deformation in different areas. Since the first forming gap (3.0 mm) is greater than the second forming gap (1.2 mm), the deformation of the aluminum alloy sheet at the corresponding position in the thick-walled area is small, basically maintaining the original thickness or only slightly thinning, forming a thick-walled area; the deformation at the corresponding position in the thin-walled area is large, and the sheet is significantly thinned, forming a thin-walled area; in the transition area, the sheet wall thickness smoothly transitions along the gradual gap. The formed shell has a precisely controlled wall thickness distribution, with a wall thickness of approximately 3.0 mm in the thick-walled area, approximately 1.2 mm in the thin-walled area, and a wall thickness that gradually changes from 3.0 mm to 1.2 mm in the transition area.

[0028] Step S4: Online detection and feedback adjustment.

[0029] After stamping, an ultrasonic wall thickness detection device is used to measure the wall thickness of the formed shell. The ultrasonic wall thickness detection device includes multiple ultrasonic probes arranged along the shell contour, with a detection frequency of 20Hz and a detection accuracy of ±0.05mm. After acquiring the actual wall thickness data, the data processing unit compares the actual wall thickness with the target wall thickness. When the deviation between the actual wall thickness and the target wall thickness exceeds ±0.10mm, the data processing unit sends a feedback signal. If the actual wall thickness in the thick-walled area is too large, the first punch insert with a larger protrusion height or the first die insert with a larger concave depth is replaced; if the actual wall thickness in the thin-walled area is too small, the die-closing pressure of the servo press is reduced or the protrusion height of the corresponding punch insert in the thin-walled area is lowered. Through online detection and feedback adjustment, wall thickness accuracy control in mass production is achieved. Example

[0030] This embodiment provides a method for forming aluminum alloy housings of different wall thicknesses using a multi-station progressive stamping die, suitable for manufacturing motor controller housings. The housing is rectangular, approximately 300mm long, 200mm wide, and 80mm deep. The bottom of the housing is a thin-walled area with a designed wall thickness of 1.0mm; the side walls and four mounting posts are thick-walled areas with a designed wall thickness of 2.5mm; the transition zone width is 15mm.

[0031] The stamping die used in this embodiment is a multi-station progressive stamping die, which includes blanking station, pre-drawing station, differential wall thickness forming station, shaping station and punching and trimming station in sequence along the feeding direction.

[0032] The blanking station is equipped with blanking dies for punching aluminum alloy strip into blanks of a predetermined profile. The blank material is 6063-O temper aluminum alloy sheet. The pre-drawing station is equipped with pre-drawing dies, and the gap between the punch and die of the pre-drawing die is uniform. During the pre-drawing process, the material undergoes some thinning, but the wall thickness distribution is basically uniform.

[0033] The differential wall thickness forming station is equipped with a differential wall thickness forming die. The differential wall thickness forming die includes a punch assembly and a die assembly. The punch assembly includes a first punch section corresponding to the thick-walled area and a second punch section corresponding to the thin-walled area. The forming end face of the first punch section protrudes a first distance of 0.75mm relative to the forming end face of the second punch section. The die assembly includes a first die section corresponding to the thick-walled area and a second die section corresponding to the thin-walled area. The bottom surface of the cavity of the first die section is recessed a second distance of 0.75mm relative to the bottom surface of the cavity of the second die section. The first forming gap is 2.5mm, the second forming gap is 1.0mm, and the transition forming gap gradually changes from 2.5mm to 1.0mm. Based on the pre-drawn semi-finished product, the differential wall thickness forming die transforms the uniform wall thickness of the semi-finished product into different wall thicknesses, maintaining the thick-walled area at approximately 2.5mm and reducing the thin-walled area to approximately 1.0mm.

[0034] The forming station is equipped with forming molds, which are used to finish the shells after forming with different wall thicknesses, eliminate the slight springback and surface unevenness generated during the forming process, and improve the dimensional accuracy and surface quality of the shells.

[0035] The punching and trimming station is equipped with punching and trimming dies, which are used to punch mounting holes, heat dissipation holes, etc. on the housing and remove excess edge material to obtain the final housing product.

[0036] Each workstation is connected by an automatic feeding mechanism to achieve continuous automated production, with a production efficiency of 10-20 pieces per minute or more. Example

[0037] This embodiment provides a method for forming aluminum alloy shells of different wall thicknesses by setting a gradient friction coating on the forming surface of the mold, focusing on optimizing material flow distribution and improving wall thickness accuracy.

[0038] In this embodiment, the forming surfaces of the first punch section, the second punch section, the first die section, and the second die section are all provided with gradient friction coatings. The gradient friction coatings are prepared using physical vapor deposition (PVD) technology, and the coating material is a TiAlN-based composite coating. By adjusting the carbon content and surface texture in the coating, the friction coefficients of different regions are differentiated.

[0039] In the corresponding thick-walled regions, the coefficient of friction of the gradient friction coating ranges from 0.08 to 0.12, which falls into the low-friction coefficient range. A low friction coefficient helps reduce the deformation resistance of the material in the thick-walled regions, promotes material flow from the thick-walled regions to the thin-walled regions, and prevents wrinkling due to material accumulation in the thick-walled regions.

[0040] In the corresponding thin-walled region, the coefficient of friction of the gradient friction coating is 0.20 to 0.30, which belongs to the high friction coefficient region. The high friction coefficient increases the deformation resistance of the material in the thin-walled region, inhibits excessive material flow into the thin-walled region, and prevents the thin-walled region from cracking due to excessive thinning.

[0041] At the corresponding transition zone, the coefficient of friction of the gradient friction coating gradually increases from 0.12 to 0.20 along the direction from the thick-walled region to the thin-walled region, forming a region with a gradual change in the coefficient of friction. The smooth transition of the coefficient of friction allows the material flow velocity to change gradually, avoiding uneven wall thickness or surface scratches caused by abrupt changes in flow.

[0042] The gradient friction coating has a thickness of 2μm to 5μm, which ensures both the stability and wear resistance of the friction performance, while avoiding the impact of an excessively thick coating on the accuracy of the mold surface. A CrN transition layer is also provided between the coating and the mold substrate to improve the coating's bonding strength.

[0043] By setting a gradient friction coating, the material flow distribution in different wall thickness areas is further optimized without changing the mold geometry. This makes it easier for material to flow into thick-walled areas and suppresses material flow into thin-walled areas. In synergy with the mold gap differentiation, the accuracy and consistency of wall thickness distribution are further improved. Example

[0044] This embodiment provides a method for forming aluminum alloy shells of different wall thicknesses by comprehensively applying the above-mentioned technologies, for manufacturing the upper shell of a new energy vehicle battery pack. The shell is a large rectangular shell, approximately 1500mm in length, 1000mm in width, and 120mm in depth. The shell has multiple thick-walled areas (mounting base, reinforcing rib root, 4.0mm thick), a large thin-walled area (top plate area, 1.5mm thick), and a complex transition area (wall thickness gradually changes from 4.0mm to 1.5mm).

[0045] The molding method in this embodiment comprehensively adopts the following technical means: Multi-station progressive stamping: Using a five-station progressive stamping die, blanking, pre-drawing (uniform wall depth), differential wall thickness forming, shaping, punching and trimming are completed sequentially.

[0046] Differential wall thickness forming die: The punch assembly includes a first punch section (protruding 1.25mm), a second punch section (reference surface), and a third punch section (transition slope); the die assembly includes a first die section (recessed 1.25mm), a second die section (reference surface), and a third die section (transition slope). The first forming gap is 4.0mm, and the second forming gap is 1.5mm. Each punch and die section is a detachable insert, fixed by wedge blocks and shim assemblies.

[0047] Gradient friction coating: friction coefficient of 0.10 in thick-walled region, friction coefficient of 0.25 in thin-walled region, and friction coefficient gradually changes from 0.10 to 0.25 in transition region.

[0048] The blanking mechanism uses nitrogen springs to drive the upper and lower blanking plates, and the blanking force is 15% of the clamping force.

[0049] Online inspection: Sixteen ultrasonic probes are arranged at key locations on the housing, with a detection frequency of 50Hz and a deviation threshold of ±0.08mm.

[0050] Through the synergistic effect of the aforementioned comprehensive technical means, this embodiment successfully achieved one-time stamping forming of a large and complex aluminum alloy shell. The wall thickness of the thick-walled area is 4.0±0.10mm, the wall thickness of the thin-walled area is 1.5±0.08mm, and the wall thickness of the transition area is smoothly and gradually changes, without defects such as cracks, wrinkles, or excessive springback. Compared with the existing casting + machining solution, the material utilization rate is increased from about 35% to about 85%, the production cycle time is shortened from about 20 minutes / piece to about 2 minutes / piece, and the production cost is reduced by about 60%.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for forming aluminum alloy shells of different wall thicknesses, characterized in that, Includes the following steps: Aluminum alloy sheets are available; An aluminum alloy sheet is placed in a stamping die for stamping. The stamping die includes a punch assembly and a die assembly that cooperates with the punch assembly. The punch assembly includes a first punch section corresponding to the thick-walled area of ​​the shell and a second punch section corresponding to the thin-walled area of ​​the shell. The forming end face of the first punch section protrudes a first distance relative to the forming end face of the second punch section in the die closing direction. The die assembly includes a first die section corresponding to the thick-walled area and a second die section corresponding to the thin-walled area. The bottom surface of the cavity of the first die section is recessed a second distance relative to the bottom surface of the cavity of the second die section in the die closing direction. The driving punch assembly and die assembly are closed to stamp the aluminum alloy sheet, forming a thick-walled area between the first punch section and the first die section, and a thin-walled area between the second punch section and the second die section. The wall thickness of the thick-walled area is greater than that of the thin-walled area, and the difference in wall thickness between the thick-walled area and the thin-walled area is equal to the sum of the first distance and the second distance.

2. The method for forming aluminum alloy shells with different wall thicknesses according to claim 1, characterized in that: The punch assembly also includes a third punch section corresponding to the transition area between the thick-walled area and the thin-walled area. The forming end face of the third punch section is a transition slope, which gradually decreases along the direction from the thick-walled area to the thin-walled area. The die assembly also includes a third die section corresponding to the transition zone. The bottom surface of the cavity of the third die section is a transition slope, which gradually decreases from the thick-walled area to the thin-walled area. During mold closing, a transition forming gap is formed between the third punch section and the third die section, and the transition forming gap gradually decreases along the direction from the thick-walled area to the thin-walled area.

3. A method for forming aluminum alloy shells of different wall thicknesses according to claim 1 or 2, characterized in that: The first punch section, the second punch section, and / or the third punch section are punch inserts that are detachably mounted on the punch assembly; The first die section, the second die section, and / or the third die section are die inserts that are detachably mounted on the die assembly; The wall thickness difference between the thick-walled and thin-walled regions can be adjusted by replacing the punch inserts with different protrusion heights and / or the die inserts with different recess depths.

4. The method for forming aluminum alloy shells with different wall thicknesses according to claim 1, characterized in that: The stamping die is mounted on a servo press, and the slide motion curve of the servo press includes: During the rapid descent phase, the slider descends at the initial speed until the punch assembly contacts the aluminum alloy sheet. In the slow forming section, the slider continues to descend at a second speed, which is less than the first speed, causing the aluminum alloy sheet to gradually deform.

5. The method for forming aluminum alloy shells with different wall thicknesses according to claim 1, characterized in that: The stamping die also includes a blank holder mechanism, which includes: The upper pressure plate is located on the periphery of the punch assembly and is connected to the punch assembly through the first elastic element; The lower pressure plate is located on the periphery of the die assembly and is connected to the die assembly via a second elastic element; During mold closing, the upper and lower pressure plates contact the aluminum alloy sheet before the punch and die assemblies, applying pressure to the aluminum alloy sheet.

6. The method for forming aluminum alloy shells with different wall thicknesses according to claim 5, characterized in that: The forming surfaces of the first punch section, the second punch section, the first die section, and the second die section are all provided with a gradient friction coating. The coefficient of friction of the gradient friction coating is lower in the thick-walled region than in the thin-walled region.

7. The method for forming aluminum alloy shells with different wall thicknesses according to claim 1, characterized in that: Before supplying aluminum alloy sheets, the aluminum alloy sheets are pre-treated, including pre-stretching at the corresponding thick-walled areas, with a pre-stretch deformation of 5% to 15%.

8. The method for forming aluminum alloy shells with different wall thicknesses according to claim 2, characterized in that: The stamping process also includes an online inspection step: An ultrasonic wall thickness testing device was used to test the wall thickness of the formed shell to obtain the actual wall thickness data. Compare the actual wall thickness data with the target wall thickness data; When the deviation between the actual wall thickness data and the target wall thickness data exceeds the preset threshold, a feedback signal is issued. The feedback signal is used to adjust the mold closing parameters of the servo press or replace the punch insert and / or die insert.

9. The method for forming aluminum alloy shells with different wall thicknesses according to claim 5, characterized in that: The stamping die is a multi-station progressive stamping die, which includes blanking station, pre-drawing station, differential wall thickness forming station, shaping station and punching and trimming station in sequence along the feeding direction; The pre-drawing station is used to pre-form aluminum alloy sheets into semi-finished products with uniform wall thickness; Differential wall thickness forming station is used to transform the uniform wall thickness of semi-finished products into different wall thicknesses.

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