Base cover processing method

Abstract

The present application belongs to the technical field of metal processing, and discloses a bottom cover processing method, comprising the following steps: S1, stamping aluminum alloy raw materials into bottom cover blanks; S2, feeding the bottom cover blanks into a cleaning line to remove surface attachments of the bottom cover blanks; S3, clamping the cleaned bottom cover blanks on a CNC machine to mill a processing surface with target precision size; S4, feeding the CNC-processed bottom cover workpieces into the cleaning line to remove surface residues of the bottom cover workpieces; S5, placing the second-cleaned bottom cover workpieces in a sandblasting device to roughen the outer surface; S6, mounting the sandblasted bottom cover workpieces on an anodic oxidation production line, electrifying the bottom cover workpieces and placing them in an electrolyte to form an anodic oxidation film on the surface of the bottom cover workpieces by oxidation; and S7, placing the anodically-oxidized bottom cover workpieces in a laser device to form an identification code on the surface of the bottom cover workpieces by laser. The bottom cover processing method provided by the present application takes into account size precision control and appearance quality protection, and effectively improves product yield.

Description

Technical Field

[0001] This invention belongs to the field of metal processing technology, and specifically relates to a method for processing a bottom cover. Background Technology

[0002] Aluminum alloys are widely used in the manufacture of bottom covers for 3C electronic products due to their advantages such as low density, high specific strength, and ease of forming. Currently, the standard processing flow for aluminum alloy bottom covers typically includes: stamping to form a bottom cover blank with a pre-defined shape and foot pad structure; cleaning to remove stamping residue; CNC machining to achieve the target dimensional accuracy; sandblasting and anodizing to meet appearance and corrosion resistance requirements; and laser marking to create traceability markings.

[0003] The existing process described above presents the following technical problems: Residual stress exists inside the stamped bottom cover blank, which is gradually released during subsequent CNC finishing and anodizing processes, causing warping and deformation of the bottom cover blank, affecting the flatness and assembly accuracy of the finished product. To prevent chips generated during CNC finishing from scratching the bottom cover's surface, the industry typically applies a protective film to the surface of the stamped bottom cover blank. However, when the protective film completely covers the foot pad forming area, chips generated by the CNC cutting tool around the foot pad tend to accumulate between the protective film and the foot pad edge, wrapping around the rotating tool and scratching the foot pad's surface, resulting in product scrap.

[0004] Therefore, there is an urgent need in this field for a bottom cover processing method to solve the above-mentioned technical problems. Summary of the Invention

[0005] In view of this, the present invention provides a bottom cover processing method to solve the problems in the prior art where the bottom cover blank after stamping is warped and deformed due to the release of residual stress, and the foot pad area is easily scratched by chips during CNC machining, making it difficult to achieve both processing accuracy and appearance quality.

[0006] To solve the above-mentioned technical problems, the present invention provides a bottom cover processing method, comprising: S1. Aluminum alloy raw material is stamped into a bottom cover blank. During the stamping process, the bottom cover blank is leveled to adjust the stress release direction of the bottom cover blank. A protective layer is applied to the surface of the bottom cover blank so that the protective layer avoids the periphery of the foot pad forming area. S2. The bottom cover blank is fed into the cleaning line to remove the adhering substances on the surface of the bottom cover blank. S3. Cover the surface of the cleaned bottom cover blank with a protective layer, ensuring that the protective layer avoids the periphery of the foot pad forming area, and clamp the bottom cover blank with the protective layer on a CNC machine tool to mill the machining surface with the target precision dimensions. S4. The CNC-machined bottom cover workpiece is sent into the cleaning line to remove the residue on the surface of the bottom cover workpiece. S5. Place the bottom cover workpiece after the second cleaning in a sandblasting device and spray sand particles onto the outer surface of the bottom cover workpiece to roughen the outer surface. S6. The sandblasted bottom cover workpiece is mounted on the anodizing production line. The bottom cover workpiece is energized and placed in the electrolyte to form an anodized film on the surface of the bottom cover workpiece. S7. Place the anodized bottom cover workpiece in a laser device and laser-etch an identification code onto the surface of the bottom cover workpiece.

[0007] As a further improvement of the present invention, S1 includes: S11. Cut aluminum alloy raw materials to form an intermediate sheet with a predetermined shape, and punch screw hole pre-punching structure on the intermediate sheet; S12. Peel off the original protective film from the surface of the intermediate sheet; S13. Place the intermediate sheet after peeling off the original protective film in a forging press, and cold forge a 3D spline structure on the intermediate sheet; S14. The intermediate sheet forming the 3D spline structure is placed in a forging press, and the foot pad structure is cold forged on the intermediate sheet. S15. Place the intermediate sheet forming the foot pad structure in a stamping machine, and punch an elliptical hole, a center hole for the foot pad, and a screw hole on the intermediate sheet. S16. Place the intermediate sheet with punched holes in a stamping machine, perform half-shearing on the intermediate sheet and punch screw holes to obtain the bottom cover blank.

[0008] As a further improvement of the present invention, when the bottom cover blank is leveled in S1, the punch press tonnage and leveling parameters are set so that the stress of the bottom cover blank is released in the direction of the outer surface, so as to counteract the reverse deformation generated in subsequent S3 and S6.

[0009] As a further improvement of the present invention, when the protective layer is applied in S1, a gap is left between the edge of the protective layer and the peripheral edge of the foot pad forming area, and only the probe position is retained on the protective layer.

[0010] As a further improvement of the present invention, the foot pad forming area in S1 is cold forged by a foot pad forming die, the base material of the foot pad forming die is ASP60 tool steel, and a PVD coating is vapor-deposited on the forming surface of the foot pad forming die.

[0011] As a further improvement of the present invention, S3 includes: S31. Place the cleaned bottom cover blank in the first fixture for positioning, start the CNC machine to perform the first CNC machining on the bottom cover blank, and mill the first set of machining surfaces on the bottom cover blank; S32. Position the bottom cover workpiece after the first CNC machining in the second fixture, start the CNC machine to perform the second CNC machining on the bottom cover workpiece, and mill the second set of machining surfaces on the bottom cover workpiece.

[0012] As a further improvement of the present invention, the first clamp in S31 is made of resin material, the second clamp in S32 is made of aluminum alloy material, and the surface hardness of the first clamp and the second clamp is HV450~550, and a wear-resistant coating is provided on the surface of the first clamp and the second clamp.

[0013] As a further improvement of the present invention, in S31 and S32, a PET film is laid on the positioning surface of the first clamp or the second clamp, and the bottom cover workpiece is positioned on the PET film by the positioning holes on the PET film cooperating with the positioning pins on the first clamp or the second clamp.

[0014] As a further improvement of the present invention, in S3, a cutting tool with a bottom edge is used to mill the font markings on the surface of the bottom cover workpiece. The cutting edge angle of the bottom edge is 2.5°~3.0°, and a clearance structure is provided at the center of the bottom edge.

[0015] As a further improvement of the present invention, in S6, the bottom cover workpiece is hung on the titanium alloy hanger at an inclined angle, and a protective plate is installed on the hanger to separate adjacent bottom cover workpieces.

[0016] Compared with existing technologies, the bottom cover processing method provided by this invention adjusts the stress release direction by performing a leveling treatment on the bottom cover blank during the stamping process. This releases the stress of the bottom cover blank towards the outer surface, offsetting the reverse deformation generated during subsequent CNC finishing and anodizing, effectively controlling the flatness and assembly accuracy of the finished bottom cover. Simultaneously, a protective layer is applied to the surface of the bottom cover blank, avoiding the periphery of the foot pad forming area. This prevents the accumulation of chips generated during CNC machining between the protective film and the foot pad edge, fundamentally eliminating scratches on the outer surface of the foot pad area. Compared with traditional stamping processes that do not actively control the stress release direction, the leveling treatment of this invention makes the deformation direction of the bottom cover blank controllable in subsequent multi-process machining, significantly reducing the defect rate of ground clearance exceeding tolerance due to stress release. Compared with existing solutions where the protective film fully covers the foot pad area, this invention ensures that the protective layer only covers the surface and avoids the periphery of the foot pad, preventing chips from accumulating and entangled at the foot pad edge, completely eliminating the risk of scratches in this area. Furthermore, since this invention completes stress control and protective layout during the stamping stage, there is no need to add additional chip removal or inspection steps in subsequent CNC processes, simplifying the process flow, reducing manufacturing costs, and improving mass production efficiency. The synergistic effect of leveling treatment and protective layer avoidance layout allows for both processing accuracy and appearance quality to be achieved in the same method, resulting in a significant improvement in yield. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and not all embodiments. For those skilled in the art, other drawings obtained from these drawings without creative effort are all within the scope of protection of this application.

[0018] Figure 1 This is a flowchart of a bottom cover processing method provided in an embodiment of the present invention.

[0019] Figure 2 yes Figure 1 A flowchart of step S1.

[0020] Figure 3 yes Figure 1 A flowchart of step S3. Detailed Implementation

[0021] 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 and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] To make the description of this disclosure more detailed and complete, illustrative descriptions of embodiments and specific examples of the present invention are provided below; however, these are not the only forms of implementing or utilizing the specific embodiments of the present invention. The embodiments cover features of multiple specific embodiments and the methods, steps, and their order for constructing and operating these specific embodiments. However, other specific embodiments may also be used to achieve the same or equivalent functions and step sequences. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in sequences other than those illustrated or described herein.

[0024] In the description of the embodiments of the present invention, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The word "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more. Other quantifiers should be understood similarly. The preferred embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention. Furthermore, the embodiments and features in the embodiments of this application can be combined with each other without conflict.

[0025] like Figure 1 The flowchart described above illustrates a bottom cover processing method provided in an embodiment of the present invention, which includes the following steps.

[0026] S1: The aluminum alloy raw material is stamped into a bottom cover blank. During the stamping process, the bottom cover blank is leveled to adjust the stress release direction of the bottom cover blank.

[0027] Specifically, in this embodiment of the invention, aluminum alloy sheets or coils are selected as the raw material. The sheet material is then subjected to a series of processes, including shearing, cold forging of 3D templates, and installation of foot pads, using a stamping machine to obtain a bottom cover blank with a pre-defined outline, pre-punched screw holes, and forged foot pads. The leveling process specifically involves setting the stamping press tonnage and leveling parameters during the stamping process to release the stress on the bottom cover blank towards the outer surface. This counteracts the reverse deformation generated during subsequent CNC finishing and anodizing, thereby suppressing warping deformation of the bottom cover blank during subsequent processing. As a specific embodiment of the invention, a 260T stamping press tonnage can be used.

[0028] S2: The bottom cover blank is sent into the cleaning line to remove the adhering substances on the surface of the bottom cover blank.

[0029] Specifically, in this embodiment of the invention, the stamped bottom cover blank is fed into a fully automated cleaning line. The cleaning line has multiple cleaning tanks, which sequentially spray, soak, and ultrasonically clean the bottom cover blank to remove stamping oil, metal shavings, and other impurities adhering to the surface of the bottom cover blank during the stamping process, providing a clean workpiece surface for subsequent CNC precision machining. As a specific embodiment of the invention, a 13-tank fully automated cleaning line can be selected, with each tank having a size of 1000L~1200L.

[0030] S3: Cover the surface of the cleaned bottom cover blank with a protective layer, ensuring that the protective layer avoids the periphery of the foot pad forming area, and then clamp the bottom cover blank with the protective layer on a CNC machine tool to mill the machined surface with the target precision dimensions.

[0031] Specifically, in this embodiment of the invention, a protective layer (preferably a protective film) is applied to the surface of the cleaned bottom cover blank. During application, a gap is left between the edge of the protective layer and the peripheral edge of the foot pad forming area, and only probe points are retained on the protective layer. This ensures the protective layer avoids the periphery of the foot pad forming area, preventing chip accumulation during subsequent CNC machining between the protective film and the foot pad edge. As a specific embodiment of the invention, the distance between the edge of the protective layer and the peripheral edge of the foot pad forming area can be 0mm to +0.15mm, and four probe points can be set. Furthermore, the foot pad forming area is cold-forged using a foot pad forming die. The base material of the foot pad forming die can be ASP60 tool steel, and a PVD coating is vapor-deposited on the forming surface of the die to increase the wear resistance of the forming surface and suppress poor ring markings at the foot pad root after anodizing. Simultaneously, the bottom cover blank with the protective layer applied is positioned on a CNC machine tool using a fixture, and the CNC machine tool is started to perform precision milling on the bottom cover blank. CNC finishing includes a first CNC machining and a second CNC machining: In the first CNC machining, the cleaned bottom cover blank is positioned in the first fixture, and the CNC machine is started to perform roughing and finishing on the bottom cover blank, milling the first set of machined surfaces on the bottom cover blank; In the second CNC machining, the bottom cover workpiece after the first CNC machining is positioned in the second fixture, and the CNC machine is started to perform finishing on the bottom cover workpiece, milling the second set of machined surfaces on the bottom cover workpiece. During CNC finishing, a protective layer covers the surface of the bottom cover blank, protecting the appearance of the bottom cover. Since the protective layer avoids the foot pad forming area, chips cannot accumulate and entangle in this area, thus preventing scratches on the appearance of the foot pad area. In a specific embodiment of the present invention, the first fixture can be made of FR-4 material, and the second fixture can be made of AL7075 material. Both fixtures have a surface hardness of HV450~550 and are equipped with a wear-resistant coating (such as a hard anodized coating). A PET film can be laid on the positioning surface of the fixture. The bottom cover workpiece is precisely positioned by engaging the positioning pins on the fixture through the positioning holes on the PET film. The diameter tolerance of the positioning pins is +0.00 / -0.03mm. Furthermore, during CNC finishing, when milling the lettering on the surface of the bottom cover workpiece using a tool with a bottom cutting edge, the inclination angle of the bottom cutting edge can be selected as 2.5°~3.0°, and the bottom cutting edge is designed to not pass through the center to reduce cutting vibration and cutting residue, and prevent tool marks from forming in the lettering area.

[0032] S4: The CNC-machined bottom cover workpiece is sent to the cleaning line to remove the residue on the surface of the bottom cover workpiece.

[0033] Specifically, in this embodiment of the invention, the protective layer on the surface of the bottom cover workpiece is removed, and the CNC-machined bottom cover workpiece is sent back to the fully automatic cleaning line to remove cutting residues (such as cutting fluid, aluminum chips, etc.) generated during CNC machining, providing a clean workpiece surface for subsequent sandblasting. As a specific embodiment of the invention, a 13-tank fully automatic cleaning line can be selected, with each tank having a size of 1000L~1200L.

[0034] S5: Place the bottom cover workpiece after the second cleaning in a sandblasting device and spray sand particles onto the outer surface of the bottom cover workpiece to roughen the outer surface.

[0035] Specifically, in this embodiment of the invention, the bottom cover workpiece after the second cleaning is placed in a sandblasting device, and sand particles are sprayed onto the outer surface through a sandblasting gun to obtain a uniform roughness on the outer surface of the bottom cover workpiece, so as to meet the adhesion requirements and appearance decoration requirements of the subsequent anodizing treatment. During the sandblasting process, the sandblasting pressure of the outer and inner surfaces can be adjusted separately as needed.

[0036] S6: The sandblasted bottom cover workpiece is mounted on the anodizing production line, the bottom cover workpiece is energized and placed in the electrolyte, and an anodized film is formed on the surface of the bottom cover workpiece.

[0037] Specifically, in this embodiment of the invention, the sandblasted bottom cover workpiece is mounted on a fixture on an anodizing production line, immersed in an electrolyte, and subjected to direct current, causing an electrochemical reaction on the surface of the bottom cover workpiece to generate an anodized film with high hardness and corrosion resistance. As a specific embodiment of the invention, a titanium alloy fixture can be used. The bottom cover workpiece is mounted on the fixture at an inclined angle (e.g., 10°~20° relative to the vertical direction of the fixture), and a protective plate is installed on the fixture to separate adjacent bottom cover workpieces, preventing contact damage during mounting and transport.

[0038] S7: Place the anodized bottom cover workpiece in a laser device and laser-etch an identification code onto the surface of the bottom cover workpiece.

[0039] Specifically, in this embodiment of the invention, the bottom cover workpiece after anodizing is placed in a laser marking device, and a QR code or other identification code is formed at a designated position on the surface of the bottom cover workpiece by laser beam, so as to realize product traceability and information management.

[0040] As an optional implementation, please refer to Figure 2 In step S1, the stamping process includes the following sub-steps: S11: Cut aluminum alloy raw materials to form an intermediate sheet with a predetermined shape, and punch screw hole pre-punch structure on the intermediate sheet.

[0041] Specifically, in this embodiment of the invention, aluminum alloy coils or sheets are fed into a blanking die, and an intermediate sheet with a predetermined outline is cut out through the blanking process. Simultaneously with the blanking, a pre-punched screw hole structure is punched at a predetermined position on the intermediate sheet. This pre-punched screw hole structure provides pre-positioning and material guidance for subsequent semi-shearing and punching processes, which helps improve the dimensional and positional accuracy of the final screw hole and reduces material deformation resistance during fine blanking. The blanking of the outline and the pre-punching of the screw hole are completed in the same stamping station, reducing process flow and secondary positioning errors.

[0042] S12: Peel off the original protective film from the surface of the intermediate sheet.

[0043] Specifically, in this embodiment of the invention, the aluminum alloy raw material is typically covered with an original protective film on its surface when it leaves the factory to prevent surface scratches during transportation and storage. After entering the stamping process, the cut intermediate sheet is sent to the demolding station, where the original protective film on the surface of the intermediate sheet is removed by mechanical peeling or air blowing. The purpose of removing the original protective film is to provide a clean metal surface for the subsequent cold forging process, and to prevent the original protective film from being pressed into the material surface during forging or from leaving residues under high temperature and high pressure, which would affect the forging quality and the subsequent anodizing surface effect.

[0044] S13: Place the intermediate sheet after peeling off the original protective film in a forging press, and cold forge a 3D spline structure on the intermediate sheet.

[0045] Specifically, in this embodiment of the invention, the intermediate sheet after the original protective film is peeled off is placed on the worktable of a forging press. Local forging pressure is applied to a predetermined area of ​​the intermediate sheet using a forging die, causing the material to plastically flow within the die cavity, thus cold-forging a 3D spline structure onto the intermediate sheet. This 3D spline structure is used as a positioning reference in subsequent CNC machining and as a mating structure during product assembly. Compared to machining, cold forging has advantages such as high material utilization and work hardening that improves structural strength. Simultaneously, the internal grains of the material are refined during cold forging, which is beneficial for improving the dimensional stability and surface quality of the 3D spline structure.

[0046] S14: The intermediate sheet forming the 3D spline structure is placed in a forging press, and the foot pad structure is cold forged on the intermediate sheet.

[0047] Specifically, in this embodiment of the invention, the intermediate sheet forming the 3D spline structure is transferred to the foot pad forging station and placed in a forging press. Local forging pressure is applied to the foot pad forming area of ​​the intermediate sheet through the foot pad forming die, causing the material to plastically flow within the die cavity, thus cold-forging the foot pad structure onto the intermediate sheet. The foot pad structure is used for subsequent assembly with the foot pad. Compared to machining, cold forging avoids cutting the material's fiber structure, maintaining the continuity of the material structure and improving the strength and fatigue resistance of the foot pad structure. As a specific embodiment of the invention, the base material of the foot pad forming die can be ASP60 tool steel, and a PVD coating is vapor-deposited on the forming surface of the die to increase the wear resistance of the forming surface and suppress poor foot pad root markings caused by die wear during long-term production.

[0048] S15: The intermediate sheet forming the foot pad structure is placed in a stamping machine, and an elliptical hole, a center hole for the foot pad, and a screw hole are punched on the intermediate sheet.

[0049] Specifically, in this embodiment of the invention, the intermediate sheet forming the foot pad structure is transferred to the punching station and placed in a punching machine. Elliptical holes, a center hole for the foot pad, and screw holes are punched at predetermined positions on the intermediate sheet using a punching die. The punching process separates the material to be removed from the intermediate sheet in one step through punching, offering advantages in processing efficiency and cost compared to subsequent CNC milling. The elliptical holes are used for positioning and hot riveting during product assembly, the center hole for foot pad installation positioning, and the screw holes for threaded connections during subsequent assembly.

[0050] S16: Place the intermediate sheet with punched holes in a stamping machine, perform half-shearing on the intermediate sheet and punch screw holes to obtain the bottom cover blank.

[0051] Specifically, in this embodiment of the invention, the intermediate sheet after punching holes is transferred to the semi-shearing and fine-blanking station and placed in a stamping press. The intermediate sheet is semi-sheared in a predetermined area using a semi-shearing die, causing partial separation of the material without breakage, forming a semi-sheared structure with a specific shape and depth. Simultaneously, fine-blanking is performed at the pre-punched screw hole location to obtain screw holes with the required final dimensions and shape accuracy. The semi-shearing process is used to form structural features such as snap-fits and positioning grooves required for product assembly. Fine-blanking the screw holes further refines the hole walls based on the pre-punched structure, eliminating pre-punching burrs and ensuring hole diameter accuracy. Through the stamping forming sub-steps S11 to S16 described above, a bottom cover blank with a preset outer contour, 3D spline structure, foot pad structure, elliptical holes, foot pad center holes, and screw holes is obtained, providing a precise blank foundation for subsequent CNC precision machining. These sub-steps are completed sequentially in a continuous stamping die, reducing the handling and secondary positioning of the workpiece between processes, which helps ensure the relative positional accuracy between various features.

[0052] As an optional implementation, in step S1, when the bottom cover blank is leveled, the punch press tonnage and leveling parameters are set so that the stress of the bottom cover blank is released in the direction of the outer surface, so as to counteract the reverse deformation generated in subsequent S3 and S6.

[0053] Specifically, in this embodiment of the invention, during the stamping process of the bottom cover blank, after the aluminum alloy material undergoes processes such as blanking, bending, and cold forging, the internal grains experience slippage and dislocations, resulting in an uneven distribution of residual stress. This residual stress is gradually released during subsequent CNC finishing (S3) and anodizing (S6) processes due to the removal of material layer by layer and the effect of heating, causing the bottom cover blank to warp inwards towards the cavity, thereby affecting the flatness of the finished product and the height above the ground after assembly.

[0054] To address the aforementioned issues, this invention adds a leveling step to the stamping process. Specifically, the stamped bottom cover blank is fed into a leveling device (such as a precision leveler or a punch press with leveling function). The punch press tonnage and leveling parameters (including leveling roller gap, reduction amount, and feed speed) are set, and a reverse bending force is applied to the bottom cover blank. Through this leveling process, a plastic deformation layer opposite to the direction of residual stress is generated on the surface of the bottom cover blank, thereby actively controlling the stress release direction. This causes the residual stress of the bottom cover blank to be released towards the outer surface, resulting in a slightly arched state of the bottom cover blank towards the outer surface. The curvature of this slightly arched state is precisely controlled within a preset range to counteract the reverse deformation towards the inner cavity caused by material removal and heat treatment in subsequent steps S3 and S6.

[0055] The essence of the aforementioned leveling process is to reorient the stress distribution of the bottom cover blank by applying controlled plastic deformation in advance. After the leveling process, the residual stress inside the bottom cover blank is in a controlled pre-release state. In steps S3 and S6, as the bottom cover blank material is removed layer by layer by milling and heated, the residual stress is gradually released in a preset direction, and the slight arching of the bottom cover blank towards the outer surface decreases and tends to become straight. In other words, the leveling process causes the bottom cover blank to arch slightly towards the outer surface in advance. This slight arching is sufficient to offset the reverse deformation caused by stress release during subsequent processing, thereby ensuring that the finished bottom cover maintains the target flatness and ground clearance dimensions after processing in steps S3 and S6.

[0056] In a specific embodiment of the present invention, a 260T punch press can be selected, and the leveling parameters can be set to -1.0 / 0.8 (i.e., the upper leveling roller pressure is 1.0mm and the lower leveling roller pressure is 0.8mm). This parameter combination allows the stress of the bottom cover blank to be released in the direction of the outer surface by an arching amount of about 0.2mm~0.7mm, which precisely compensates for the reverse deformation generated during the subsequent CNC and anodizing processes. This significantly improves the flatness of the finished bottom cover and the pass rate of the assembly height dimension, while eliminating the need for additional straightening processes, which is beneficial for controlling manufacturing costs.

[0057] As an optional implementation, in step S1, when the protective layer is applied, a gap is left between the edge of the protective layer and the peripheral edge of the foot pad forming area, and only the probe position is retained on the protective layer.

[0058] Specifically, in this embodiment of the invention, the surface of the aluminum alloy raw material is usually covered with an original protective film. However, this original protective film may be damaged or wrinkled during the stamping process due to the pressure of the mold. Therefore, after the stamping is completed, the original protective film needs to be peeled off and a new protective layer needs to be applied. The protective layer is applied by attaching the protective layer (preferably a PET protective film) to the surface area of ​​the bottom cover blank. During the attachment process, a gap is left between the edge of the protective layer and the peripheral edge of the foot pad forming area, so that the peripheral side of the foot pad forming area is exposed outside the protective layer, and the protective layer avoids the peripheral side of the foot pad forming area.

[0059] Meanwhile, only the probe points are retained on the protective layer. These probe points are the locations where the probe contacts and inspects the workpiece before CNC machining. Only these locations are covered by the protective layer, while the rest (especially the periphery of the foot pad forming area) remains completely exposed. In this way, the protective layer covers the surface of the bottom cover blank, protecting its appearance. Since the periphery of the foot pad forming area is uncovered, chips generated during CNC machining cannot accumulate there. The chips are naturally discharged by gravity or the washing action of the cutting fluid, preventing chip entanglement and thus avoiding scratches on the foot pad area's appearance. Retaining the probe points with the protective layer ensures that the CNC probe contacts the protective layer surface, not the metal surface, preventing scratches on the bottom cover blank surface.

[0060] In a specific embodiment of the present invention, the gap between the edge of the protective layer and the peripheral edge of the foot pad forming area can be selected from 0mm to +0.15mm. When the gap is 0mm, the edge of the protective layer and the peripheral edge of the foot pad forming area are just touching but not overlapping, and chips still cannot accumulate in the gap between them; when the gap is +0.15mm, the protective layer is further away from the foot pad forming area, providing more space for chip discharge. The probe points can be set to four, located in the four corner areas of the bottom cover blank surface, to comprehensively reflect the clamping posture and positional offset of the bottom cover blank on the CNC machine tool.

[0061] By applying the aforementioned protective layer, the protective function of the layer on the bottom cover surface is preserved, while the risk of scratches caused by chip accumulation in the foot pad molding area is fundamentally eliminated. Compared to existing solutions that fully cover the foot pad area with a protective film, this invention eliminates the need for additional chip removal or full appearance inspection after CNC machining, simplifying the process and reducing labor costs.

[0062] As an optional implementation, in step S1, the foot pad forming area is cold forged using a foot pad forming die. The base material of the foot pad forming die is ASP60 tool steel, and a PVD coating is vapor-deposited on the forming surface of the foot pad forming die.

[0063] Specifically, in this embodiment of the invention, the foot pad structure is formed by cold forging, and its forming quality directly depends on the performance of the foot pad forming die. Conventional foot pad forming dies are mostly made of die steels such as SKD11 and Cr12MoV, which have limited hardness and wear resistance. In mass production, as the number of stamping cycles increases, the die forming surface gradually wears down, and the surface finish decreases, resulting in micro-scratches or uneven material flow in the root area of ​​the cold-forged foot pad. In the subsequent anodizing process (S6), due to the difference in the growth rate of the anodized film at the micro-scratches, the originally invisible micro-defects are magnified, forming visible circular marks at the root of the foot pad.

[0064] To address the aforementioned issues, the substrate material of the foot pad forming die in this invention is ASP60 powder high-speed tool steel. ASP60 possesses high hardness, high wear resistance, and excellent tempering stability. Its wear resistance is significantly superior to conventional die steel, maintaining the shape accuracy and surface finish of the forming surface during long-term stamping production and mitigating the surface quality deterioration of the foot pad root caused by die wear. Simultaneously, a PVD coating (preferably titanium nitride-based or aluminum-titanium-based composite coating) is vapor-deposited onto the forming surface of the foot pad forming die. The PVD coating exhibits high hardness, a low coefficient of friction, and excellent anti-adhesion properties, further reducing the coefficient of friction between the aluminum alloy material and the die forming surface during cold forging. This allows for smoother material flow during forging and reduces surface defects at the foot pad root caused by material adhesion or scratching.

[0065] Through the synergistic effect of the ASP60 tool steel substrate and the PVD coating, on the one hand, the substrate provides sufficient toughness support to prevent the mold from cracking or plastic deformation under high-frequency impact; on the other hand, the PVD coating provides excellent surface protection and friction reduction and lubrication effects, significantly improving the wear resistance and demolding performance of the foot pad forming die.

[0066] As an optional implementation, please refer to Figure 3In step S3, the CNC finishing process includes the following sub-steps.

[0067] S31: Place the cleaned bottom cover blank in the first fixture for positioning, start the CNC machine to perform the first CNC machining on the bottom cover blank, and mill the first set of machining surfaces on the bottom cover blank.

[0068] Specifically, in this embodiment of the invention, the cleaned bottom cover blank is placed on the worktable of a CNC machine tool, and the bottom cover blank is positioned and clamped by a first fixture. The first fixture is designed according to the preset shape and positioning reference of the bottom cover blank, and provides limits for the bottom cover blank in the X, Y, and Z directions to ensure that the bottom cover blank is fixed in position during processing. The CNC machine tool is started, and the bottom cover blank is subjected to the first CNC machining according to the preset machining program. The rotating milling cutter is used to perform rough machining and partial finishing on the inner surface and foot pad structure of the bottom cover blank, milling out the first set of machining surfaces. The first CNC machining mainly undertakes the rough machining task with a high material removal rate, removing the machining allowance reserved after stamping, and initially shaping the inner cavity structure, foot pad mounting surface, and screw hole finishing features of the bottom cover blank. As a specific embodiment of the present invention, the first fixture can be made of FR-4 (glass fiber reinforced epoxy resin). The hardness of the FR-4 matrix is ​​approximately HV100~150. Its moderate hardness ensures that it will not cause indentations or scratches on the surface of the aluminum alloy bottom cover blank during clamping, while also possessing good dimensional stability and insulation properties. The working surface of the first fixture is provided with a wear-resistant coating, the hardness of which is HV450~550, to improve the durability of the fixture and prevent a decrease in positioning accuracy due to wear during long-term use. During the first CNC machining, the protective layer still covers the surface area of ​​the bottom cover blank, protecting the outer surface of the bottom cover and preventing the large amount of chips generated during rough machining from scratching the outer surface.

[0069] S32: Position the bottom cover workpiece after the first CNC machining in the second fixture, start the CNC machine to perform the second CNC machining on the bottom cover workpiece, and mill the second set of machining surfaces on the bottom cover workpiece.

[0070] Specifically, in this embodiment of the invention, the bottom cover workpiece after the first CNC machining is transferred to the CNC machine tool's worktable, and the bottom cover workpiece is repositioned and clamped using a second fixture. Since the first CNC machining has created a precise positioning reference surface on the bottom cover workpiece, the second CNC machining uses this reference surface as the positioning basis to ensure coordinate consistency between the two machining operations. The CNC machine tool is started, and the bottom cover workpiece is subjected to the second CNC machining according to the preset machining program. A rotating milling cutter is used to perform finishing machining on the appearance surface and precision structural areas of the bottom cover workpiece, milling out the second set of machined surfaces. The second CNC machining mainly undertakes the finishing task with high precision dimensions and high appearance surface quality requirements, milling out the final contour, lettering marking areas, and assembly mating surfaces of the bottom cover workpiece's appearance surface. The second CNC machining requires higher dimensional accuracy and surface finish. The cutting parameters (such as feed rate, spindle speed, and depth of cut) are more refined than those of the first CNC machining. At the same time, tool wear needs to be controlled to ensure that the appearance surface of the bottom cover workpiece meets the dimensional tolerances and surface roughness requirements of the design drawings.

[0071] In a specific embodiment of the present invention, the second fixture can be made of AL7075 (high-strength aluminum alloy), which has high strength and hardness, providing stable clamping force for precision machining. The surface hardness of the second fixture can be HV450~550 and it is equipped with a wear-resistant coating (such as a hard anodized coating) to improve the fixture's durability and wear resistance, ensuring that the positioning accuracy does not decrease during long-term use. Through the division of labor and cooperation of the above two CNC machining operations, both material removal efficiency and the dimensional accuracy and surface quality of the final product are guaranteed. The first CNC machining prioritizes efficiency to quickly remove most of the excess material, while the second CNC machining prioritizes accuracy to finely trim key dimensions and appearance surfaces. The two machining operations work together to complete all milling tasks of the bottom cover workpiece.

[0072] This invention divides CNC finishing into two stages: a first CNC machining stage and a second CNC machining stage. Each stage uses its own suitable fixture for positioning, avoiding clamping deformation caused by accumulated machining stress during a single clamping. This is particularly suitable for ultra-thin bottom cover workpieces with a thickness of 0.8mm-0.85mm. Furthermore, the re-clamping between the two machining stages allows for correction of the workpiece's posture, further ensuring the dimensional accuracy of the finished product.

[0073] As an optional implementation, in step S31, the first fixture is made of FR-4 material, and in step S32, the second fixture is made of AL7075 material. The surface hardness of the first fixture and the second fixture is HV450~550, and a wear-resistant coating is provided on the surface of the first fixture and the second fixture.

[0074] Specifically, in this embodiment of the invention, CNC finishing includes two stages: a first CNC machining and a second CNC machining. In each stage, fixtures of different materials are used to position and clamp the workpiece.

[0075] In the first CNC machining stage, the first fixture is made of resin, specifically FR-4. FR-4 is a glass fiber reinforced epoxy resin composite material, possessing excellent dimensional stability and machinability. Its coefficient of linear expansion is similar to that of aluminum alloy, maintaining stable positioning accuracy under varying CNC machining ambient temperatures, and is less prone to loosening or positioning misalignment due to thermal expansion and contraction. Simultaneously, FR-4 material has good insulation and vibration damping properties, effectively absorbing cutting vibrations during the roughing stage and reducing their impact on the positioning accuracy of the bottom cover blank. Furthermore, FR-4 material has moderate hardness (after treatment, its surface hardness can reach HV450~550), preventing indentations or scratches on the aluminum alloy bottom cover blank surface, making it suitable for roughing scenarios in the first CNC machining stage where material removal is the primary focus.

[0076] In the second CNC machining stage, the second fixture is made of aluminum alloy, specifically AL7075. AL7075 is a high-strength aluminum alloy that, after solution aging treatment, possesses high strength and hardness (surface hardness HV450~550), providing stable and sufficient clamping force for finishing. Since the second CNC machining stage involves high-precision milling of the surface and precision structures, the requirements for workpiece positioning rigidity and clamping stability are higher. The high strength of AL7075 ensures that the fixture does not undergo elastic deformation under the cutting forces of finishing, thus guaranteeing the final dimensional accuracy of the bottom cover workpiece. Simultaneously, the coefficient of thermal expansion of AL7075 is highly compatible with that of the bottom cover workpiece (aluminum alloy), resulting in strong consistency in thermal deformation caused by temperature rise during machining, avoiding positioning errors caused by differences in thermal expansion between the fixture and the workpiece.

[0077] Both the first and second fixtures are coated with a wear-resistant coating (preferably a hard anodized coating). This wear-resistant coating significantly improves the surface hardness and wear resistance of the fixtures (surface hardness HV450~550), effectively resisting frictional wear caused by workpiece clamping and unclamping during long-term use. This allows the fixtures to maintain stable positioning accuracy and clamping force in mass production, reducing dimensional drift and quality fluctuations caused by fixture wear. Simultaneously, the hard anodized coating has self-lubricating properties, reducing friction during workpiece clamping and unclamping, which helps improve loading and unloading efficiency and reduces the risk of workpiece surface scratches.

[0078] This invention employs a two-part approach: the first fixture is made of FR-4 material, and the second fixture is made of AL7075 material. This provides tailored clamping solutions for the different needs of roughing and finishing processes. Roughing prioritizes vibration damping and protection, while finishing prioritizes rigidity and stability. Both fixtures have a surface hardness of HV450~550 and are coated with a wear-resistant coating. This approach balances the requirements of maintaining positioning accuracy, protecting the workpiece surface, and extending the fixture's lifespan. It is particularly suitable for high-precision batch processing of ultra-thin aluminum alloy bottom covers with a thickness of 0.8mm~0.85mm.

[0079] As an optional implementation, in steps S31 and S32, a PET film is laid on the positioning surface of the first or second clamp, and the bottom cover workpiece is positioned on the PET film by the positioning holes on the PET film cooperating with the positioning pins on the first or second clamp.

[0080] Specifically, in this embodiment of the invention, the bottom cover workpiece is positioned using a PET film in both the first and second CNC machining processes. The PET film is a sheet of polyethylene terephthalate (PET), which possesses excellent dimensional stability, tensile strength, and surface flatness. The PET film is laid on the positioning surface of the first or second fixture, covering the positioning surface of the fixture and serving as an intermediate medium layer between the bottom cover workpiece and the metal surface of the fixture.

[0081] The PET film has positioning holes, and the first or second clamp has positioning pins that mate with these holes. When the PET film is laid on the positioning surface of the clamp, the positioning holes on the PET film engage with the positioning pins, achieving precise positioning of the PET film on the clamp. Subsequently, the bottom cover workpiece is placed on the PET film, and its own positioning holes or positioning references also mate with the positioning pins on the clamp, thus achieving precise positioning of the bottom cover workpiece on the PET film.

[0082] A PET film separates the bottom cover workpiece from the metal surface of the fixture. This PET film provides a uniform and flexible support surface, absorbing minor flatness errors in the bottom surface of the workpiece. This ensures more even stress distribution under clamping force, preventing localized stress concentration or deformation caused by rigid contact with the fixture's positioning surfaces. Simultaneously, the PET film has a certain coefficient of friction, aiding in the clamping force to secure the workpiece and preventing micro-vibration displacement during CNC machining. Furthermore, as a sacrificial layer, the PET film absorbs cutting vibrations during CNC machining, reducing vibration transmission to the workpiece and improving surface finish. After machining, the bottom cover workpiece is removed from the PET film, which can be replaced with a new film for the next batch, ensuring consistent positioning accuracy in each machining operation.

[0083] In a specific embodiment of the present invention, multiple positioning holes can be provided on the PET film, each positioning hole cooperating with a corresponding positioning pin on the fixture. The diameter tolerance of the positioning pin can be +0.00 / -0.03mm, and the hole diameter of the PET film positioning hole can be designed accordingly to fit the size (e.g., Φ2.20±0.1mm or Φ8.20±0.1mm) to ensure the positioning accuracy of the PET film on the fixture. After the positioning pin on the fixture passes through the positioning hole of the PET film, it further cooperates with the positioning hole on the bottom cover workpiece to achieve sequential positioning of the bottom cover workpiece, PET film, and fixture. The above scheme prevents the bottom cover workpiece from directly contacting the metal surface of the fixture, effectively avoiding damage such as indentations and scratches caused by small protrusions or impurities on the positioning surface of the fixture, which is beneficial to improving the appearance quality of the finished product. At the same time, the PET film is inexpensive and easy to replace, making it suitable for the high-frequency clamping requirements in mass production.

[0084] As an optional implementation, in step S3, the letter markings on the surface of the bottom cover workpiece are milled using a tool with a bottom cutting edge. The cutting edge angle of the bottom cutting edge is 2.5°~3.0°, and a clearance structure is provided at the center of the bottom cutting edge.

[0085] Specifically, in this embodiment of the invention, the surface of the bottom cover workpiece needs to be milled to form font markings (such as product model, logo, etc.). The milling of these font markings is performed using an end mill or engraving tool with a bottom cutting edge. The tool rotates around its central axis, and the bottom cutting edge cuts and shapes the surface of the bottom cover workpiece. Conventional tools typically have a bottom cutting edge that passes through the tool center (i.e., an over-center structure) with a small inclination angle to enhance tool rigidity. However, when machining font markings, especially letters with V-shaped intersecting strokes such as "M," "N," and "W," the tool needs to frequently perform small-radius turning and retraction movements. When the bottom cutting edge passes through the center and the inclination angle is too small, the cutting speed near the center of the bottom cutting edge is extremely low, significantly reducing the cutting ability in this area and easily causing cutting residue at the V-shaped intersection. Simultaneously, the over-center structure causes the central area of ​​the bottom cutting edge to experience squeezing friction with the workpiece surface during machining, exacerbating tool wear. The worn bottom cutting edge cannot effectively cut the material, resulting in discontinuous tool marks at the edges of the font strokes, affecting the appearance quality of the font markings.

[0086] To address the aforementioned issues, this invention provides a recessed structure at the center of the bottom cutting edge. This recessed structure is formed by material removal in the central area of ​​the bottom cutting edge, preventing the cutting edge from extending to the central axis of the tool. The central area of ​​the tool has no cutting function. This structure avoids ineffective cutting and squeezing friction caused by excessively low linear velocity in the central area of ​​the bottom cutting edge. Simultaneously, the inclination angle of the bottom cutting edge is set to 2.5°~3.0°, meaning the bottom cutting edge is inclined at 2.5°~3.0° relative to a plane perpendicular to the tool axis. This inclination angle creates a bevel cutting effect when the bottom cutting edge enters the workpiece, reducing cutting resistance, improving chip removal smoothness, distributing cutting force more evenly on the bottom cutting edge, and reducing chatter and residual cutting force.

[0087] With the aforementioned clearance structure at the center of the bottom edge and the cooperation of the blade inclination angle of 2.5°~3.0°, the tool cuts smoothly and removes chips easily when milling letter markings. The bottom edge is less likely to produce burrs and vibration marks when entering and exiting, effectively avoiding poor tool marks in the letter marking area (especially at the intersection of the letters V).

[0088] As an optional implementation, in step S6, the bottom cover workpiece is hung on the titanium alloy hanger at an inclined angle, and a protective plate is installed on the hanger to separate adjacent bottom cover workpieces.

[0089] Specifically, in this embodiment of the invention, the anodizing process involves using the sandblasted bottom cover workpiece as the anode, placing it in an acidic electrolyte and applying direct current to it, thereby growing an anodic oxide film with a porous structure in situ on the surface of the bottom cover workpiece. This anodic oxide film significantly improves the surface hardness, wear resistance, and corrosion resistance of the bottom cover workpiece, while the porous structure provides an adhesion basis for subsequent dyeing or sealing treatments. During the anodizing process, the bottom cover workpiece needs to be mounted on a fixture and immersed in the electrolyte; the fixture serves both as a conductor and a load-bearing element.

[0090] The mounting brackets are made of titanium alloy. Titanium alloy has excellent corrosion resistance and does not corrode or dissolve in the acidic electrolytes used in anodizing (usually sulfuric acid or oxalic acid systems), preventing the bracket material itself from corroding and contaminating the electrolyte. Simultaneously, titanium alloy has good electrical conductivity, ensuring that current is evenly conducted to the surface of the workpiece under the bracket, guaranteeing the uniformity of the anodized film growth. Furthermore, titanium alloy has good mechanical strength and creep resistance, making it less prone to deformation during long-term use, ensuring the dimensional stability and service life of the mounting brackets.

[0091] When the bottom cover workpiece is mounted on the hanger, it is tilted at an angle relative to the vertical direction of the hanger (preferably 10°-20°). The purpose of this tilted mounting is that a large number of bubbles are generated in the electrolyte during the anodizing process. If the bottom cover workpiece is mounted vertically, the bubbles easily adhere to the surface of the workpiece, resulting in insufficient contact between local areas and the electrolyte, which in turn causes uneven thickness of the anodized film or bubble marks. By mounting the bottom cover workpiece at an angle, the bubbles slide upward along the tilted surface under the action of buoyancy and quickly detach from the surface of the workpiece, effectively avoiding bubble adhesion and ensuring the uniformity of the growth and the consistency of the appearance of the anodized film.

[0092] A protective plate is installed on the hanger, positioned between adjacent bottom cover workpieces. The protective plate serves to prevent relative shaking or swaying of adjacent bottom cover workpieces during loading, transport, and immersion in the electrolyte. If adjacent workpieces come into direct contact, abnormal current density or chemical residue at the contact point can cause contact burns or corrosion, resulting in poor appearance. The protective plate separates adjacent bottom cover workpieces, preventing direct contact during the anodizing process. In a specific embodiment of this invention, the protective plate can be made of acid and alkali resistant insulating materials (such as polypropylene, polytetrafluoroethylene, etc.) and fixedly installed on the crossbeam or frame of the hanger. The width and position of the protective plate are designed according to the size of the bottom cover workpieces and the loading spacing to effectively separate adjacent workpieces.

[0093] Through the synergistic effect of the titanium alloy hanger, the tilt angle of the bottom cover workpiece, and the protective plate separating adjacent workpieces, the bottom cover workpiece and the electrolyte are fully and evenly contacted during the anodizing process, preventing uneven appearance caused by bubble adhesion. At the same time, damage caused by mutual contact between workpieces during transportation is avoided, effectively improving the yield of the finished product after anodizing.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The above embodiments merely illustrate preferred implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for processing a bottom cover, characterized in that, include: S1. The aluminum alloy raw material is stamped into a bottom cover blank. During the stamping process, the bottom cover blank is leveled to adjust the stress release direction of the bottom cover blank. S2. The bottom cover blank is fed into the cleaning line to remove the adhering substances on the surface of the bottom cover blank. S3. Cover the surface of the cleaned bottom cover blank with a protective layer, ensuring that the protective layer avoids the periphery of the foot pad forming area, and clamp the bottom cover blank with the protective layer on a CNC machine tool to mill the machining surface with the target precision dimensions. S4. The CNC-machined bottom cover workpiece is sent into the cleaning line to remove the residue on the surface of the bottom cover workpiece. S5. Place the bottom cover workpiece after the second cleaning in a sandblasting device and spray sand particles onto the outer surface of the bottom cover workpiece to roughen the outer surface. S6. The sandblasted bottom cover workpiece is mounted on the anodizing production line. The bottom cover workpiece is energized and placed in the electrolyte to form an anodized film on the surface of the bottom cover workpiece. S7. Place the anodized bottom cover workpiece in a laser device and laser-etch an identification code onto the surface of the bottom cover workpiece.

2. The bottom cover processing method according to claim 1, characterized in that, S1 includes: S11. Cut aluminum alloy raw materials to form an intermediate sheet with a predetermined shape, and punch screw hole pre-punching structure on the intermediate sheet; S12. Peel off the original protective film from the surface of the intermediate sheet; S13. Place the intermediate sheet after peeling off the original protective film in a forging press, and cold forge a 3D spline structure on the intermediate sheet; S14. The intermediate sheet forming the 3D spline structure is placed in a forging press, and the foot pad structure is cold forged on the intermediate sheet. S15. Place the intermediate sheet forming the foot pad structure in a stamping machine, and punch an elliptical hole, a center hole for the foot pad, and a screw hole on the intermediate sheet. S16. Place the intermediate sheet with punched holes in a stamping machine, perform half-shearing on the intermediate sheet and punch screw holes to obtain the bottom cover blank.

3. The bottom cover processing method according to claim 1, characterized in that, When the bottom cover blank is leveled in S1, the punch press tonnage and leveling parameters are set so that the stress of the bottom cover blank is released in the direction of the outer surface, so as to counteract the reverse deformation generated in subsequent S3 and S6.

4. The bottom cover processing method according to claim 1, characterized in that, When the protective layer is applied in S1, a gap is left between the edge of the protective layer and the peripheral edge of the foot pad forming area, and only the probe position is retained on the protective layer.

5. The bottom cover processing method according to claim 2, characterized in that, The foot pad forming area in S1 is cold forged by a foot pad forming die. The base material of the foot pad forming die is ASP60 tool steel, and a coating is vapor-deposited on the forming surface of the foot pad forming die.

6. The bottom cover processing method according to claim 1, characterized in that, S3 includes: S31. Place the cleaned bottom cover blank in the first fixture for positioning, start the CNC machine to perform the first CNC machining on the bottom cover blank, and mill the first set of machining surfaces on the bottom cover blank; S32. Position the bottom cover workpiece after the first CNC machining in the second fixture, start the CNC machine to perform the second CNC machining on the bottom cover workpiece, and mill the second set of machining surfaces on the bottom cover workpiece.

7. The bottom cover processing method according to claim 6, characterized in that, The first clamp in S31 is made of resin, and the second clamp in S32 is made of aluminum alloy. The surface hardness of the first clamp and the second clamp is HV450~550, and a wear-resistant coating is provided on the surface of the first clamp and the second clamp.

8. The bottom cover processing method according to claim 6, characterized in that, In S31 and S32, a PET film is laid on the positioning surface of the first clamp or the second clamp, and the bottom cover workpiece is positioned on the PET film by the positioning holes on the PET film cooperating with the positioning pins on the first clamp or the second clamp.

9. The bottom cover processing method according to claim 1, characterized in that, In step S3, a cutting tool with a bottom edge is used to mill the letter markings on the surface of the bottom cover workpiece. The bottom edge has a cutting inclination angle of 2.5° to 3.0° and a clearance structure is provided at the center of the bottom edge.

10. The bottom cover processing method according to claim 1, characterized in that, In step S6, the bottom cover workpiece is hung on a titanium alloy hanger at an inclined angle, and a protective plate is installed on the hanger to separate adjacent bottom cover workpieces.

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