A forming process and device for a wheel cover outer panel with normal flanging on a slope

Abstract

The application relates to the technical field of automobile part stamping forming, and discloses a forming process and device of a wheel cover outer plate with a normal flanging on an inclined surface, which comprises the following steps: obtaining a flat sheet; carrying out concave forming in a drawing die, butt-jointing the back of a left side car wheel cover outer plate and a right side car wheel cover outer plate, horizontally opening the door sill area profile of the left side car wheel cover outer plate and the door sill area profile of the right side car wheel cover outer plate to the outside to obtain a stretching process piece; cutting, punching, flanging and shaping, inwardly extruding and contracting the door sill area profile; cutting off the butt-jointing area waste, driving a flanging concave die to be attached to and supported in a first stroke interval of a lower die seat, and driving a flanging convex die to be stabbed into the flanging concave die along the normal direction in a second stroke interval. The application improves material flow and prevents cracking through concave forming, prevents interference between the flanging concave die and the flanging convex die through driving the flanging concave die and the flanging convex die in the stroke intervals in sequence, and guarantees the size precision of the normal flanging on the inclined surface.

Description

Technical Field

[0001] This invention relates to the field of automotive component stamping technology, specifically to a process and apparatus for forming a wheel arch outer panel with normal flanging holes on an inclined surface. Background Technology

[0002] The outer wheel arch panel is an important side frame component of the car body. It not only features a deep cavity profile with a large drop, but also typically requires normal flanges for assembly connections on its beveled edges. In traditional stamping processes, limitations in the drawing layout and stamping direction hinder material flow in the deep cavity area. Specifically, the draft angle at the door sill area is small, resulting in high frictional resistance. External flange material cannot flow smoothly into the deep cavity for replenishment, easily leading to excessive stretching and thinning of the material at the bottom of the cavity, or even cracking. Excess free material can also cause wrinkling defects due to compressive stress instability. Furthermore, traditional forming postures result in a lack of flat adhesion areas on the surface of the drawn parts. During automated transport, the vacuum chuck assembly cannot provide stable vertical lifting force, leading to a high rate of detachment during transport and a large absolute vertical clearance distance required to remove the parts from the mold. This increases transport time and reduces the cycle time of the stamping production line.

[0003] In processing normal flanging holes on inclined surfaces, traditional forming devices often employ synchronously moving wedge mechanisms. These mechanisms suffer from overlapping action sequences when driving the flanging die and punch, particularly during the demolding return phase. The synchronous retraction of the punch and die causes interference, resulting in friction between the punch and the edge of the normal flanging hole on the inclined surface. Because the edge of the hole lacks stable support during the retraction process, it is prone to deformation or tearing under stress, directly leading to loss of dimensional accuracy in the hole diameter and causing damage to the wheel arch outer panel, rendering it unusable. Therefore, this invention proposes a forming process and apparatus for wheel arch outer panels with normal flanging holes on inclined surfaces to address the shortcomings of existing technologies. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a forming process and apparatus for wheel cover outer panels with normal flanging holes on inclined surfaces. This solves the problems of stretching, thinning, cracking, and wrinkling in the deep cavity area during the stamping process of traditional car wheel cover outer panels, high drop rates during automated handling, and loss of hole diameter accuracy and part damage due to interference from demolding action when processing the normal flanging holes on the inclined surfaces.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a forming process for a wheel cover outer plate with normal flanges on an inclined surface, employing the following technical solution:

[0007] A process for forming a wheel cover outer plate with normal flanges on an inclined surface includes the following steps:

[0008] A blanking die is used to blank and punch the steel plate to obtain a flat sheet.

[0009] The flat sheet is placed into the drawing die for stretching and forming. The stamping direction is set to concave forming. The back of the left car wheel cover outer panel and the right car wheel cover outer panel are joined together. The wheel opening surfaces of the left and right car wheel cover outer panels are set to face outward. Wrinkle-removing ribs are set on the process supplement surface of the drawing die. The sill area profiles of the left and right car wheel cover outer panels are opened horizontally outward to obtain the stretching process part.

[0010] Remove the waste material from the stretching process, complete the stamping of some flange holes and side wall holes, and obtain the first process part. Remove the remaining edge waste material from the first process part, complete the stamping of the remaining flange holes and side wall holes, and obtain the second process part. Flang the second process part, and use the flanging forming die to squeeze and shrink the sill area that opens outwards inwards to obtain the third process part.

[0011] Remove the waste material from the docking area of ​​the third process part, separate the outer panel of the left car wheel cover from the outer panel of the right car wheel cover, and drive the lateral flanging die to the working position of the separated surface of the left car wheel cover and the surface of the right car wheel cover during the first stroke interval of the upper die pressing down. During the second stroke interval of the upper die pressing down, drive the flanging punch of the lower die to move along the normal direction of the inclined plane and insert into the flanging die to obtain the outer panel of the wheel cover.

[0012] By adopting the above technical solution, due to the concave molding and the layout of the left and right car wheel arch outer panels being connected to each other, the sill area profiles of the left and right car wheel arch outer panels are opened horizontally outward, and the flanging die and flanging punch are driven sequentially in the stroke interval. Therefore, the effect of improving the flow state of deep cavity material and reducing the demolding interference breakage rate is achieved.

[0013] The specific molding steps are explained below:

[0014] The process employs concave forming, connecting the back of the left and right wheel arch outer panels. The convex cavity of the drawing die is merged into a continuous, integral central area of ​​the convex die. The flat sheet material is uniformly extended along the surface of the integral convex die. Combined with wrinkle-absorbing ribs on the process supplement surface, the material's resistance to bending and anti-bending deformation is increased, improving material flow and preventing compressive stress instability and wrinkling of free material. The sill area profiles of the left and right wheel arch outer panels are horizontally opened outwards, increasing the draft angle of the deep cavity and reducing the frictional resistance of the sharp angles. This allows the external flange material to flow smoothly into the deep cavity area of ​​the sill for replenishment, preventing excessive stretching, thinning, and cracking of the material at the bottom of the deep cavity.

[0015] With sufficient material thickness allowance, the forming inserts set in the flanging forming mold will compress and shrink the outward-opening threshold area inward to restore it to the theoretical design shape, thus eliminating the risk of forming cracks in the deep cavity while maintaining the dimensional accuracy of the part.

[0016] During the first stroke of the upper die pressing down, the lateral flanging die is driven to the fitting position first, thus completing the rigid support of the separated left and right wheel arch outer panels in advance. During the second stroke of the upper die pressing down, the lower die's flanging punch is driven to move along the normal direction and insert into the flanging die. The timing difference of the step-by-step actions is used to separate the vertical pressing and supporting action from the inclined normal punching deformation action, preventing the edge of the inclined normal flanging from collapsing without support when under pressure.

[0017] Preferably, the connection between the back of the left wheel arch outer panel and the right wheel arch outer panel specifically includes:

[0018] The wheel arch surfaces of the left and right car wheel arches are arranged together on the central area of ​​a punch in the drawing die.

[0019] By adopting the above technical solution, the flat sheet is not pulled in multiple directions by the punch, and the central area of ​​the punch guides the flat sheet to extend evenly, thereby improving the uniformity of the material thickness distribution of the overall stretched part.

[0020] Preferably, within the range of the upper die holder rising and retracting, the piercing punch is pulled out and retracted downwards; after the piercing punch retracts, the piercing die retracts outwards.

[0021] By adopting the above technical solution, a reverse demolding anti-interference sequence is constructed. In the initial stage of the upper mold base lifting, the flipping punch loses the downward driving force and is pulled out first along the normal direction of the inclined plane, separating from the inner wall opening of the flipping hole in the normal direction of the inclined plane. After the flipping punch is completely withdrawn, the flipping die retracts to the outside to release the spatial constraint, eliminating the spatial locking problem caused by the simultaneous movement of the flipping punch and the flipping die, and avoiding the upward friction force generated by the simultaneous retraction acting on the edge of the flipping hole in the normal direction of the inclined plane, which would cause deformation.

[0022] Preferably, the molding process uses a mold with an upper pressure plate, a stop drive wedge and a first transmission wedge;

[0023] Within the first stroke range of the upper die holder pressing down, the working positions of the drive-side flipping die reaching the surfaces of the left and right wheel arch outer panels after bonding and separation specifically include:

[0024] The upper mold base begins to descend from its highest point, and the upper pressure plate contacts the separated left and right car wheel cover outer panels and stops relative movement.

[0025] During the first stroke interval of the upper die holder continuing to descend, the pause drive wedge drives the first transmission wedge to slide horizontally, and the first transmission wedge pushes the flipping die to slide along the normal of the inclined plane to the working position;

[0026] The first stroke range is 8mm to 12mm.

[0027] By adopting the above technical solution, the inclined surface of the stop drive wedge cooperates with the sliding of the transmission wedge to generate an absolute displacement of 8mm to 12mm in the upper die holder. The vertical linear displacement of the upper die holder is converted into the horizontal thrust of the transmission wedge, and the transmission is realized within the set stroke, so that the flipping die fits against the support surface.

[0028] Preferably, when the driving-side flanging die reaches the working position where the outer surface of the left and right wheel arches of the car are joined and separated:

[0029] The vertical straight segment of the first stop guide plate, which is fixedly mounted on the stop drive wedge on the upper mold base, slides and fits relative to the vertical straight segment of the second stop guide plate, which is fixedly mounted on the outside of the first transmission wedge.

[0030] By adopting the above technical solution, when the upper die holder continues to move downward and generates displacement in the second stroke interval, the vertical straight segments of the two sets of stopping guide plates fit together, applying geometric locking constraints to the transmission wedge, ensuring that the turning die does not deviate laterally or shift when subjected to normal impact force in the future.

[0031] Preferably, the mold also has a drive wedge and a lower mold second conduction wedge;

[0032] During the second stroke interval of the upper die holder continuing to press down, the flipping punch driving the lower die moves along the normal direction of the inclined plane and inserts into the flipping die body, including:

[0033] As the upper die holder continues to descend within the second stroke range, the drive wedge drives the lower die's second transmission wedge to slide horizontally. The lower die's second transmission wedge converts the horizontal thrust into the thrust of the ejector punch moving along the inclined plane in the normal direction.

[0034] The distance between the end point of the downward displacement in the second travel interval and the highest point is 18mm to 22mm.

[0035] By adopting the above technical solution, after the flanging die is supported and locked, the drive wedge moves downward and contacts the lower die guide wedge. The lower die guide wedge converts the horizontal thrust into a normal pushing force, driving the flanging punch to penetrate the metal and complete the machining. This mechanical structure eliminates the timing overlap between the supporting and punching actions, ensuring that the formed hole diameter tolerance meets design requirements.

[0036] Preferably, the first batch of independent wedge mechanisms arranged on the edge of the sidewall of the workpiece in the stretching process are used to complete part of the sidewall hole punching;

[0037] The remaining sidewall holes are punched using a second batch of independent wedge mechanisms arranged on the edge of the sidewall of the first workpiece.

[0038] By adopting the above technical solution, the sidewall punching process, which is relatively numerous or located in close proximity, is distributed to different stamping batches, thus avoiding interference in the internal space of the mold caused by arranging too many wedge mechanisms in a single stamping process.

[0039] Preferably, after obtaining the stretching process part, a six-axis industrial robot end effector equipped with a vacuum suction cup assembly is used to transport the stretching process part;

[0040] The vacuum suction cup assembly adheres to the flat back, and the spatial angle between the force-bearing surface of the vacuum suction cup assembly and the absolute horizontal plane is within 5°.

[0041] By adopting the above technical solution, the concave molding process creates a flat back surface for the stretched workpiece, which facilitates the adhesion of the vacuum suction cup assembly. By controlling the spatial angle within 5°, the vacuum suction force generated by the vacuum suction cup assembly is completely converted into a vertical lifting force that resists absolute gravity, thereby enhancing the adsorption stability and preventing the stretched workpiece from falling off during transportation. In addition, the overall concave contour reduces the absolute Z-axis vertical avoidance displacement distance required for the stretched workpiece to move out of the mold area, shortening the transfer time and improving the equipment cycle time.

[0042] Preferably, the sill area profile of the left wheel arch outer panel and the sill area profile of the right wheel arch outer panel are opened outward horizontally to 10° to 20°.

[0043] By adopting the above technical solution, for the tensile characteristics of thin sheet materials with a thickness of 0.50mm to 1.00mm, opening by 10° to 20° can appropriately expand the forming space to compensate for the material elongation, thereby reducing the forming friction resistance while ensuring a smooth and defect-free outer surface structure.

[0044] Secondly, the present invention provides a wheel cover outer plate forming device with normal flip-holes on an inclined surface, which adopts the following technical solution:

[0045] A wheel cover outer plate forming device with normal flanges on an inclined surface, comprising:

[0046] The upper module includes an upper mold base, a drive wedge, a stop drive wedge, a first stop guide plate, and a nitrogen cylinder. The first stop guide plate is fixedly installed on the stop drive wedge. Both the drive wedge and the stop drive wedge are fixedly connected to the lower surface of the upper mold base. The nitrogen cylinder is fixed on the upper mold base and the output end of the nitrogen cylinder is set downward.

[0047] The side-feeding assembly includes an upper pressure plate with an internal cavity support structure, a flanging die, a first transmission wedge, a second stopping guide plate, and a flanging die return spring and a first transmission wedge return spring. The upper pressure plate receives the output pressure of the nitrogen cylinder. The flanging die and the first transmission wedge are movably mounted on the inner guide seat of the upper pressure plate. The second stopping guide plate is fixedly mounted on the outer side of the first transmission wedge and slides in cooperation with the first stopping guide plate.

[0048] The normal stamping assembly includes a lower die base, a piercing punch, a second guide wedge, a lower support punch for supporting the bottom of the workpiece to be pierced, a piercing punch return spring, and a second guide wedge return spring. The piercing punch and the second guide wedge are slidably disposed on the lower die base.

[0049] The stop drive wedge cooperates with the first transmission wedge to drive the movement of the flipping die; the drive wedge cooperates with the second transmission wedge to drive the flipping punch to insert into the flipping die after the flipping die is in place.

[0050] By adopting the above technical solution, the mechanical layout structure in which the upper module, the side feeding group and the normal stamping group cooperate with each other is used to break down the vertical downward pressing force into multiple steps of horizontal thrust by utilizing the spatial linkage geometric relationship between the transmission components. Therefore, the effect of sequentially executing the support and punching actions and preventing demolding damage is achieved.

[0051] The specific motion breakdown steps of the wheel cover outer panel forming device are explained below:

[0052] During the clamping stage: the upper die base moves downward, causing the upper pressure plate to contact the workpiece to be turned over. The nitrogen cylinder is compressed and contracts to provide a stable surface clamping force for the upper pressure plate, preventing the workpiece to be turned over from moving during the punching process.

[0053] Lateral support stage: The upper mold base continues to descend and push the stop drive wedge to contact the transmission wedge of the lateral feed group. The transmission wedge of the lateral feed group slides horizontally and pushes the flipping die. After the flipping die reaches the fitting position, the stop guide plate of the upper mold group slides to the outside of the stop guide plate of the lateral feed group and fits against each other, locking the transmission wedge of the lateral feed group in the working position and forming rigid support for the edge of the hole.

[0054] Normal stamping stage: The upper die holder moves to the area near the bottom dead center and the driving wedge contacts the transmission wedge of the normal stamping group. The transmission wedge of the normal stamping group converts the horizontal sliding force into the normal pushing force. The pushing and pushing punch penetrates the workpiece to be turned and enters the interior of the turning die to complete the plastic deformation shearing of the hole opening.

[0055] Reverse retraction stage: The upper die holder rises, the drive wedge disengages first from the transmission wedge of the normal stamping group, and the flanging punch retracts to its initial position and exits the hole under the pull of the flanging punch return spring; after the flanging punch is completely pulled out, the stop guide plate of the upper die group and the stop drive wedge disengage from the transmission wedge of the lateral feeding group, and the flanging die retracts outward under the pull of the flanging die return spring, releasing the spatial constraint on the edge of the hole of the workpiece to be flanged; finally, the nitrogen cylinder extends to release the blanking force, completing a safe punching cycle without demolding interference. The sequential demolding of the fully mechanical structure ensures the operational safety of the forming device and the roundness of the hole diameter of the inclined normal flanging.

[0056] The above solution achieves the following beneficial technical effects:

[0057] This invention sets the stamping direction to concave forming, aligning the back of the left and right wheel arch outer panels. The sill area profiles of both the left and right wheel arch outer panels are horizontally opened outwards, increasing the draft angle of the deep cavity and reducing forming friction resistance. This allows external flange material to flow smoothly into the deep cavity area for replenishment, preventing thinning and cracking of the material at the bottom of the cavity. Combined with wrinkle-absorbing ribs on the process replenishment surface of the drawing die, this prevents compressive stress instability and wrinkling of the free material, improving the yield rate of the wheel arch outer panels.

[0058] This invention drives the flanging die to a working position that fits the outer surfaces of the left and right wheel arches during the first stroke of the upper die holder's downward press. During the second stroke of the upper die holder's continued downward press, the flanging punch moves along the inclined plane normal direction to insert into the flanging die, separating the surface support action from the inclined plane punching deformation action. During the upper die holder's upward retraction phase, the flanging punch is pulled out and retracted first. After the flanging punch retracts, the flanging die retracts outward. This eliminates spatial interference caused by the overlapping actions of the flanging punch and the flanging die, and avoids the frictional force generated during the retraction phase acting on the edge of the inclined plane normal flanging hole, thus ensuring the dimensional accuracy of the inclined plane normal flanging hole.

[0059] This invention employs concave molding to create a flat back surface on the stretched workpiece. This is combined with a six-axis industrial robot end effector equipped with a vacuum suction cup assembly to transport the stretched workpiece. The spatial angle between the force-bearing surface of the vacuum suction cup assembly and the absolute horizontal plane is controlled within 5°, ensuring that the vacuum suction force generated by the vacuum suction cup assembly is completely converted into a vertical lifting force that resists absolute gravity. This improves mechanical adsorption stability, prevents the stretched workpiece from falling off during transport, and reduces the vertical clearance distance required for the stretched workpiece to move out of the mold area, shortening the transport and transfer time and increasing the cycle time of the stamping equipment. Attached Figure Description

[0060] Figure 1 This is a perspective view of the mold structure for the perforated area of ​​the outer plate of the wheel cover according to the present invention;

[0061] Figure 2 This is a schematic diagram of the dynamic displacement timing history curve of the pause wedge driven mold structure of the present invention;

[0062] Figure 3 This is a schematic diagram comparing the effective adhesion flat area and included angle of the vacuum suction cup of the present invention;

[0063] Figure 4 This is a schematic diagram comparing the Z-axis vertical avoidance travel distance with the highest stable transmission cycle time of the present invention;

[0064] Figure 5 This is a schematic diagram comparing the material flow limit in the threshold cavity region with the surface defects of the stamped part according to the present invention.

[0065] The components are as follows: 1. Upper die base; 2. Drive wedge; 3. Stop drive wedge; 4. First stop guide plate; 5. Nitrogen cylinder; 6. Upper pressure plate; 7. Flanging die; 8. First transmission wedge; 9. Second stop guide plate; 10. Part to be ferruled; 11. Lower die base; 12. Flanging punch; 13. Second transmission wedge; 14. Lower support punch; 15. Flanging die return spring; 16. First transmission wedge return spring; 17. Flanging punch return spring; 18. Second transmission wedge return spring. Detailed Implementation

[0066] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] Basic description of the mold structure of this invention:

[0068] The core mold structure of this invention mainly includes a blanking and stretching layout structure and a stopping wedge mechanism for realizing the normal flipping of the inclined surface. In the stretching forming mold layout, the mold cavity adopts a concave forming and back-to-back docking design, that is, the inner surface of the product wheel cover faces the mold punch, and the wheel opening surfaces of the left and right wheel cover outer plates face outward, forming a butterfly-shaped cross stretching shape. Wrinkle-removing ribs are provided on the process supplement surface of the two side plates. This layout structure merges two conventional punches that were originally close together into a whole punch center area, and the stretching surface of the threshold area opens outward at a 15° angle relative to the theoretical surface of the product to increase the draft angle.

[0069] In the process of trimming, punching, separating, and turning holes, combined with the attached... Figure 1 As shown, the structure mainly consists of an upper die assembly, a side feeding assembly, and a normal stamping assembly. The upper die assembly includes an upper die base 1, a drive wedge 2, a stop drive wedge 3, a first stop guide plate 4, and a nitrogen cylinder 5. The first stop guide plate 4 is fixedly installed on the stop drive wedge 3. Both the drive wedge 2 and the stop drive wedge 3 are fixedly connected to the lower surface of the upper die base 1. The nitrogen cylinder 5 is fixed on the upper die base 1 and its output end presses downward against the upper pressure plate 6 of the side feeding assembly.

[0070] The side feeding assembly mainly includes an upper pressure plate 6, a flanging die 7, a first guide wedge 8, a second resting guide plate 9, and a flanging die return spring 15 and a first guide wedge return spring 16. The upper pressure plate 6 is a support structure with an inner cavity. The flanging die 7 and the first guide wedge 8 are movably mounted on the inner guide seat of the upper pressure plate 6. The second resting guide plate 9 is fixedly mounted on the outer side of the first guide wedge 8. The flanging die return spring 15 is connected between the flanging die 7 and the support wall of the upper pressure plate 6. The first guide wedge return spring 16 is connected between the first guide wedge 8 and its sliding base.

[0071] The normal stamping assembly mainly includes a lower die base 11, a piercing punch 12, a second guide wedge 13, a lower support punch 14, and a flange punch return spring 17 and a second guide wedge return spring 18. The lower support punch 14 is fixed on the lower die base 11 to support the bottom of the workpiece 10 to be pierced. The piercing punch 12 and the second guide wedge 13 are slidably disposed on the lower die base 11. The flange punch return spring 17 is fixedly connected to the piercing punch 12. The second guide wedge return spring 18 is fixedly connected behind the second guide wedge 13.

[0072] The working principle of this core mold structure is as follows: when the upper mold base 1 begins to descend from its highest point, the upper pressure plate 6 first contacts the workpiece 10 to be turned on the lower supporting punch 14. Subsequently, the upper pressure plate 6 stops moving relative to the workpiece, and the nitrogen cylinder 5 is compressed to provide pressure force. During the first ten millimeters of the descent of the upper mold base 1, the stop drive wedge 3 begins to work and uses its inclined surface to drive the first guide wedge 8 to slide horizontally to the left. The first guide wedge 8 further pushes the turning die 7 to slide downward and to the right along the normal direction of the inclined surface to reach the working position that is close to the surface of the part. At this time, the vertical straight line segment of the first stop guide plate 4 slides relative to the vertical straight line segment of the second stop guide plate 9. The upper die holder 1 is geometrically locked to prevent lateral displacement as the upper die continues to move downward. After the upper die holder 1 contacts the workpiece 10 to be holed from the pressure plate, it continues to descend within the subsequent stroke range of 10 mm to 20 mm from the bottom dead center. The inclined surface of the drive wedge 2 starts to work and drives the second drive wedge 13 of the lower die to slide horizontally to the right. The second drive wedge 13 then converts the horizontal thrust into the thrust of the hole punch 12 in the normal direction of the inclined surface to push it upward and to the left. The hole punch 12 inserts into the workpiece 10 to be holed and enters the cavity of the hole punch 7, completing the inclined surface normal hole-making work of the workpiece 10 to be holed. At this time, the upper die holder 1 reaches the bottom dead center.

[0073] After the stamping process is completed, the upper die holder 1 gradually rises, and the drive wedge 2 disengages from the second guide wedge 13 first. Under the elastic force of the second guide wedge return spring 18, the second guide wedge 13 retracts to the left to its initial position. After the flanging punch 12 loses its support, it retracts to the lower right to its initial position under the elastic force of the flanging punch return spring 17 and is completely pulled out from the workpiece 10 to be flanged. As the upper die holder 1 continues to rise, the inclined surface of the stopping drive wedge 3 begins to disengage from the first guide wedge 8. The first guide wedge 8 retracts from the first guide wedge return spring 16. Under the action of force, it retracts to the right to the initial position. Under the action of the spring force of the flange die retraction spring 15, the piercing die 7 retracts to the upper left to the initial position and completely releases the wrapping constraint on the edge of the part. During this reverse sequence of anti-interference demolding, the upper pressure plate 6 is always stably pressed against the part to be pierced 10 under the continuous extension pressure of the nitrogen cylinder 5 to prevent the part from deforming. Finally, the upper die holder 1 continues to rise to the highest point, and the upper pressure plate 6 disengages from the part to be pierced 10, completing the entire single safe and interference-free stamping cycle.

[0074] Examples 1-3:

[0075] Example 1:

[0076] This embodiment provides a forming process and apparatus for a wheel cover outer plate with normal flange holes on an inclined surface, including the following steps:

[0077] The unfolded dimensions of the sheet metal are calculated based on the surface unfolded dimensions of the left and right car wheel arch outer panels in the drawn state. The cold-rolled low-carbon deep-drawing steel sheet with a thickness of 0.70mm is blanked and punched using a blanking die to obtain a flat sheet.

[0078] The flat sheet is placed into a drawing die for stretching and forming. The stretching and forming stamping direction is set to concave forming. The left and right wheel arch outer panels are positioned with their backs together. The wheel opening surfaces of both the left and right wheel arch outer panels face outwards, forming a butterfly-shaped cross-stretching pattern. The wheel arch surfaces of both the left and right wheel arch outer panels are arranged as a whole on the punch part of the drawing die. Wrinkle-removing ribs are set on the process supplementary surfaces of the drawing die corresponding to the outer edges of the left and right wheel arch outer panels. In the process supplementary surface design of the drawing die, the sill area profiles of the left and right wheel arch outer panels are opened horizontally outwards by 15° to obtain the stretched part.

[0079] Cut off excess edge waste around the perimeter of the drawn part, use a vertical punch to complete the punching of the forward flange hole of part of the drawn part, and use the first batch of independent wedge mechanisms arranged on the side wall edge of the drawn part to complete the punching of the side wall hole of part of the drawn part, thus obtaining the first part of the process.

[0080] Remove the remaining edge waste around the perimeter of the first workpiece while keeping the waste in the back joint area between the left and right car wheel arch outer panels unbroken. Complete the stamping of the remaining forward flange holes of the first workpiece. Use a second batch of independent wedge mechanisms arranged on the side wall edge of the first workpiece to complete the stamping of the remaining side wall holes of the first workpiece, and obtain the second workpiece.

[0081] The front and side flanging of the wheel arch of the second process part is completed by using a flanging and shaping mold with a lower pressure plate. The sill area of ​​the second process part, which is opened 15° outward, is squeezed and shrunken inward to restore the theoretical design shape by the shaping insert set in the flanging and shaping mold. The local flange surface of the second process part is shaped and corrected to obtain the third process part.

[0082] Remove the waste material from the back joint area of ​​the third process part, and completely cut and separate the left and right car wheel cover outer panels into two independent parts. After separation, process the remaining punching holes on the side walls of the left and right car wheel cover outer panels. Use a stopping wedge drive mold structure to complete the normal flanging process on the inclined surfaces of the left and right car wheel cover outer panels. During the normal flanging process, the upper mold base 1 descends from the highest point, and the upper pressure plate 6 contacts the left and right car wheel cover outer panels separated from the third process part. After the relative motion stops, the upper mold base 1 continues to descend within the first 10mm of its stroke. During this 10mm stroke, the stop drive wedge 3 works and drives the first transmission wedge 8 to push the piercing die 7 to the lateral contact working position. After the upper mold base 1 contacts and separates from the left and right car wheel cover outer panels from the upper pressure plate 6, it continues to descend within the stroke range of 10mm to 20mm. The drive wedge 2 works and drives the second transmission wedge 13 to push the piercing punch 12 to move upward along the slope normal direction and insert into the piercing die 7, completing the normal piercing action on the slope of the left car wheel cover outer panel and the normal piercing action on the slope of the right car wheel cover outer panel.

[0083] Example 2:

[0084] This embodiment provides a forming process and apparatus for a wheel cover outer plate with normal flange holes on an inclined surface, including the following steps:

[0085] The unfolded dimensions of the sheet metal are calculated based on the surface unfolded dimensions of the left and right car wheel arch outer panels in the drawn state. The cold-rolled low-carbon stamping steel sheet with a thickness of 0.70mm is blanked and punched using a blanking die to obtain a flat sheet.

[0086] The flat sheet is placed into a drawing die for stretching and forming. The stretching and forming stamping direction is set to concave forming. The left and right wheel arch outer panels are aligned back-to-back. The wheel opening surfaces of both the left and right wheel arch outer panels face outwards, forming a butterfly-shaped cross-stretching pattern. The wheel arch surfaces of both the left and right wheel arch outer panels are arranged as a whole on the punch part of the drawing die. Wrinkle-removing ribs are set on the process supplementary surfaces of the drawing die corresponding to the outer edges of the left and right wheel arch outer panels. In the process supplementary surface design of the drawing die, the sill area profiles of the left and right wheel arch outer panels are opened horizontally outwards by 10° to obtain the stretched part.

[0087] Cut off excess edge waste around the perimeter of the drawn part, use a vertical punch to complete the punching of the forward flange hole of part of the drawn part, and use the first batch of independent wedge mechanisms arranged on the side wall edge of the drawn part to complete the punching of the side wall hole of part of the drawn part, thus obtaining the first part of the process.

[0088] Remove the remaining edge waste around the perimeter of the first workpiece while keeping the waste in the back joint area between the left and right car wheel arch outer panels unbroken. Complete the stamping of the remaining forward flange holes of the first workpiece. Use a second batch of independent wedge mechanisms arranged on the side wall edge of the first workpiece to complete the stamping of the remaining side wall holes of the first workpiece, and obtain the second workpiece.

[0089] The front and side flanging of the wheel arch of the second process part is completed by using a flanging and shaping mold with a lower pressure plate. The sill area of ​​the second process part, which is opened 10° outward, is squeezed and shrunken inward to restore the theoretical design shape by the shaping insert set in the flanging and shaping mold. The local flange surface of the second process part is shaped and corrected to obtain the third process part.

[0090] Remove the waste material from the back joint area of ​​the third process part, and completely cut and separate the left and right car wheel cover outer panels into two independent parts. After separation, process the remaining punching holes on the side walls of the left and right car wheel cover outer panels. Use a stopping wedge drive mold structure to complete the normal flanging process on the inclined surfaces of the left and right car wheel cover outer panels. During the normal flanging process, the upper mold base 1 descends from the highest point, and the upper pressure plate 6 contacts the left and right car wheel cover outer panels separated from the third process part. 6. Stop the relative motion. During the first 8mm of the downward stroke of the upper mold base 1, the stop drive wedge 3 works and drives the first transmission wedge 8 to push the flipping die 7 to the lateral contact working position. After the upper mold base 1 contacts and separates from the left and right car wheel cover outer plates, it continues to descend within the stroke range of 8mm to 18mm. The drive wedge 2 works and drives the second transmission wedge 13 to push the flipping punch 12 to move upward along the slope normal and insert into the flipping die 7, completing the normal flipping action on the slope of the left car wheel cover outer plate and the normal flipping action on the slope of the right car wheel cover outer plate.

[0091] Example 3:

[0092] This embodiment provides a forming process and apparatus for a wheel cover outer plate with normal flange holes on an inclined surface, including the following steps:

[0093] The unfolded dimensions of the sheet metal are calculated based on the surface unfolded dimensions of the left and right car wheel arch outer panels in the drawn state. The cold-rolled low-carbon deep-drawing steel sheet with a thickness of 0.70mm is blanked and punched using a blanking die to obtain a flat sheet.

[0094] The flat sheet is placed into a drawing die for stretching and forming. The stretching and forming stamping direction is set to concave forming. The left and right wheel arch outer panels are aligned back-to-back. The wheel opening surfaces of both the left and right wheel arch outer panels face outwards, forming a butterfly-shaped cross-stretching pattern. The wheel arch surfaces of both the left and right wheel arch outer panels are arranged as a whole on the punch part of the drawing die. Wrinkle-removing ribs are set on the process supplementary surfaces of the drawing die corresponding to the outer edges of the left and right wheel arch outer panels. In the process supplementary surface design of the drawing die, the sill area profiles of the left and right wheel arch outer panels are opened horizontally outwards by 20° to obtain the stretched part.

[0095] Cut off excess edge waste around the perimeter of the drawn part, use a vertical punch to complete the punching of the forward flange hole of part of the drawn part, and use the first batch of independent wedge mechanisms arranged on the side wall edge of the drawn part to complete the punching of the side wall hole of part of the drawn part, thus obtaining the first part of the process.

[0096] Remove the remaining edge waste around the perimeter of the first workpiece while keeping the waste in the back joint area between the left and right car wheel arch outer panels unbroken. Complete the stamping of the remaining forward flange holes of the first workpiece. Use a second batch of independent wedge mechanisms arranged on the side wall edge of the first workpiece to complete the stamping of the remaining side wall holes of the first workpiece, and obtain the second workpiece.

[0097] The front and side flanging of the wheel arch of the second process part is completed by using a flanging and shaping mold with a lower pressure plate. The sill area of ​​the second process part, which is opened 20° outward, is squeezed and shrunken inward to restore the theoretical design shape by the shaping insert set in the flanging and shaping mold. The local flange surface of the second process part is shaped and corrected to obtain the third process part.

[0098] Remove the waste material from the back joint area of ​​the third process part, and completely cut and separate the left and right car wheel cover outer panels into two independent parts. After separation, process the remaining punching holes on the side walls of the left and right car wheel cover outer panels. Use a stopping wedge drive mold structure to complete the normal flanging process on the inclined surfaces of the left and right car wheel cover outer panels. During the normal flanging process, the upper mold base 1 descends from the highest point, and the upper pressure plate 6 contacts the left and right car wheel cover outer panels separated from the third process part. The relative motion stops, and the upper die holder 1 continues to descend within the first 12mm of its stroke. During this 12mm stroke, the stop drive wedge 3 works and drives the first transmission wedge 8 to push the piercing die 7 to the lateral contact working position. After the upper die holder 1 contacts and separates from the left and right car wheel cover outer plates of the upper pressure plate 6, it continues to descend within the stroke range of 12mm to 22mm. The drive wedge 2 works and drives the second transmission wedge 13 to push the piercing punch 12 to move upward along the slope normal direction and insert into the piercing die 7, completing the normal piercing action on the slope of the left car wheel cover outer plate and the normal piercing action on the slope of the right car wheel cover outer plate.

[0099] Comparative Examples 1-4:

[0100] Comparative Example 1:

[0101] Compared with Example 1, the difference is that the stretching process sets the stretching forming stamping direction to be convex forming and is a conventional stretching arrangement. The outer panels of the left and right car wheel arches are joined on the wheel arch side, and the rest are the same.

[0102] Comparative Example 2:

[0103] Compared to Example 1, the difference lies in that the stretching process sets the stretching forming stamping direction to convex forming, and wrinkle-reducing ribs are not provided on the process supplementary surface of the drawing die. All other aspects are the same.

[0104] Comparative Example 3:

[0105] Compared with Example 1, the difference lies in the design of the process supplementary surface in the stretching process. The horizontal outward opening angle of the sill area of ​​the left car wheel arch outer panel and the sill area of ​​the right car wheel arch outer panel is set to 0°, that is, it does not expand outward. All other aspects are the same.

[0106] Comparative Example 4:

[0107] Compared with Example 1, the difference is that in the trimming side punching separation flipping process, a traditional synchronous wedge mechanism is used, without setting the first stop guide plate 4, the second stop guide plate 9 and the stop drive wedge 3, so there is no timing stroke difference. The flipping punch 12 and the flipping die 7 move and retract at the same time, and the rest are the same.

[0108] Test Examples 1-4:

[0109] Test Example 1: Kinematic Timing and Feasibility Test of Anti-Demolding Interference for a Stopping Wedge Driven Mold Structure

[0110] High-precision linear displacement sensors are installed on the corresponding motion axes of the upper die base 1, the upper pressure plate 6, the piercing die 7, and the piercing punch 12, and the high-precision linear displacement sensors are connected to a multi-channel dynamic data acquisition instrument.

[0111] Adjust the automated multi-station mechanical press to slow test mode, set the downward speed of the upper die holder 1 for a single stamping cycle to 50mm / s, and run it once under no-load to confirm that the high-precision linear displacement sensor signal transmission is normal.

[0112] The third workpiece is placed on the lower support punch 14, and the automated multi-station mechanical press is started to perform a single trimming, side punching, separation, and flipping process.

[0113] Record the absolute vertical displacement data of the upper die holder 1, the vertical displacement data of the upper pressure plate 6, the lateral displacement data of the piercing die 7 along the slope normal direction, and the upward displacement data of the piercing punch 12 along the slope normal direction during the complete stamping cycle from the time the upper die holder 1 descends from its highest point to the time the upper die holder 1 retracts to its highest point. Save the test data at a sampling rate of 20ms.

[0114] Table 1. Dynamic displacement timing test data of key components of the pause wedge drive mold structure

[0115] time Total absolute displacement of the upper mold base during downward movement (mm) Absolute displacement of the upper pressure plate (mm) Lateral travel of the piercing die (mm) Normal stroke of the piercing punch (mm) 240 12.14 12.14 0.02 0.01 420 20.95 20.95 0.03 0.02 640 31.87 20.95 10.04 0.01 860 42.76 20.95 10.05 12.06 1080 31.84 20.95 10.04 0.08 1220 21.03 20.95 0.11 0.02 1440 10.22 10.22 0.04 0.01

[0116] Conclusions and Analysis:

[0117] According to Table 1 and Figure 2 According to the data, within the range of 240ms to 420ms, the upper die holder 1 and the upper pressure plate 6 move downward synchronously. At 420ms, the upper pressure plate 6 contacts the separated left and right car wheel cover outer plates and stops moving. At this time, the displacement of the upper pressure plate 6 is stable at 20.95mm. Neither the piercing die 7 nor the piercing punch 12 has undergone any substantial displacement.

[0118] Between 420ms and 640ms, the upper die holder 1 continues to move downward, generating a stroke displacement of approximately 11mm. The stop drive wedge 3 then engages, driving the flanging die 7 to complete a 10.04mm lateral displacement to fit against the surfaces of the left and right wheel arch outer panels. During this period, the displacement of the flanging punch 12 remains within the limit system noise range of less than 0.02mm, and no actual stamping action occurs.

[0119] Between 640ms and 860ms, the upper die holder 1 continues to press down to the bottom dead center. The piercing die 7 is kept locked with a displacement of 10.05mm due to the geometric constraints of the straight segments of the first stop guide plate 4 and the second stop guide plate 9. The drive wedge 2 on the upper die holder 1 intervenes and pushes the piercing punch 12 to complete a normal stroke displacement of 12.06mm. The piercing punch 12 inserts into the piercing die 7 to complete the piercing process. Between 860ms and 1220ms during the stamping return stroke, as the upper die holder 1 is raised vertically upward, the piercing punch 12 loses its driving thrust and first retracts to the initial position of 0.08mm at 1080ms. The piercing die 7 then retracts to the initial position of 0.11mm at 1220ms. Throughout the demolding process, the upper pressure plate 6 maintains a displacement of 20.95mm, continuously applying a stable clamping force to the separated left and right car wheel arch outer panels.

[0120] The pause wedge-driven mold structure achieves displacement timing distribution of a purely mechanical structure by dividing the vertical downward linear motion into orthogonal displacement outputs at fixed displacement nodes. Test data verifies that before the piercing punch 12 pierces the outer plates of the left and right car wheel covers, the piercing die 7 has already completed rigid back support. After the punching is completed, the system strictly follows the anti-interference reverse demolding sequence of the piercing punch 12 being pulled out first, followed by the piercing die 7 releasing spatial constraints, and finally the upper pressure plate 6 releasing the outer plates of the left and right car wheel covers. The physical timing is completely consistent with the spatial linkage geometry design of the mold, proving that the transmission structure combining the first pause guide plate 4, the second pause guide plate 9, and the pause drive wedge 3 eliminates the risk of spatial interference and edge tearing during the piercing demolding process in the inclined plane normal direction.

[0121] Test Example 2: Comparison Test of Material Transfer Stability and Production Cycle Time in Automated Production Lines

[0122] On an automated multi-station mechanical press production line with the same configuration, the forming molds corresponding to Example 1, Example 2, Example 3 and Comparative Example 1 were installed respectively, and the same vacuum suction cup group was configured for the end effector of the six-axis industrial robot.

[0123] The actual spatial posture of the stretching parts corresponding to Examples 1, 2, 3 and Comparative Example 1 in the mold was scanned using a 3D laser scanner. The effective flat area that the end effector vacuum chuck can adhere to on the stretching parts was calculated, and the spatial angle between the force-bearing surface of the end effector vacuum chuck and the absolute horizontal plane was measured.

[0124] Record the minimum Z-axis vertical clearance distance required for a six-axis industrial robot end effector to grasp and lift a workpiece in a stretching process, safely cross the mold interference boundary, and enter the next workstation.

[0125] An automated multi-station mechanical press was set to run continuously for 1000 stamping cycles. The number of failures in Example 1, Example 2, Example 3 and Comparative Example 1, where the stretching workpiece fell off the end effector during material transfer was recorded and the drop rate was calculated. The highest stable transmission cycle time of the production line was tested without triggering the dynamic off-center load alarm.

[0126] Table 2. Comparison Test Data of Material Transfer Stability and Production Cycle Time in Automated Production Lines

[0127] Test group <![CDATA[Effective attachment flat area of vacuum suction cup (cm 2 )]]> Angle (°) between the suction cup's force-bearing surface and the absolute horizontal plane. Z-axis vertical avoidance travel distance (mm) Shedding rate after 1000 cycles (%) Maximum stable transmission cycle time (strokes / min) Example 1 2451.3 4.3 153.2 0.0 14.6 Example 2 2423.8 4.7 157.6 0.1 14.2 Example 3 2478.1 3.8 148.9 0.0 14.9 Comparative Example 1 842.6 67.9 415.4 4.6 7.8

[0128] Conclusions and Analysis:

[0129] According to Table 2, Figure 3 and Figure 4 The data from Comparative Example 1, using conventional convex molding, shows a significant bulge above the mold on both the left and right sides of the car wheel arch. This prevents the flat back of the vacuum suction cup from contacting the lower mold, causing the suction cup in Comparative Example 1 to only adhere to the side wall. The angle between the suction cup's force-bearing surface and the absolute horizontal plane reaches 67.9°, and the effective flat area for adhesion is only 842.6 cm². 2 Due to the excessively large included angle, the suction force generated by the vacuum suction cup has a small component in the direction perpendicular to the anti-gravity direction, which makes the stretched parts extremely susceptible to deflection due to the gravitational torque during high-speed handling, resulting in a high drop rate of 4.6% in 1000 cycles. At the same time, the punch of Comparative Example 1 protrudes upwards by a large distance, and the end effector of the six-axis industrial robot must be raised by 415.4 mm to safely cross the mold boundary. The excessively long vertical avoidance stroke distance of the Z-axis consumes handling time, resulting in the maximum stable transmission cycle being limited to 7.8 strokes / min.

[0130] Examples 1, 2, and 3 employ a recessed layout scheme, where the outer panels of the left and right car wheel arches are joined together with their backs facing upwards. This fully exposes the wide, flat back, originally hidden at the bottom, to the six-axis industrial robot end effector. The effective flat area for the vacuum suction cups in Examples 1, 2, and 3 is increased to 2400 cm². 2 In summary, the angle between the suction cup's force-bearing surface and the absolute horizontal plane is controlled within 5°. The near-horizontal adsorption posture transforms the vacuum suction force generated by the vacuum suction cup into a vertical lifting force that resists the gravity of the workpiece during the stretching process, thereby improving the mechanical gripping stiffness under dynamic handling and reducing the drop rate to below 0.1%.

[0131] Because the cavity is concave downwards, the entire drawn part after forming is below the horizontal line. The six-axis industrial robot end effector only needs to complete a vertical avoidance distance of about 150mm on the Z-axis to move the drawn part horizontally out of the mold area. The reduction in vertical lifting displacement shortens the energy consumption and time cost of the robot arm's motion cycle, which increases the maximum stable transmission cycle to more than 14.2 strokes / min. This verifies that setting the drawing forming stamping direction to a concave forming combined with a back-to-back docking butterfly-shaped cross drawing form can eliminate the bottleneck of handling interference and transmission mechanical instability in automated high-speed stamping production lines.

[0132] Test Example 3: Comparison Test of Material Flow Limit in the Deep Cavity Region of the Threshold with Surface Defects in Stamped Parts

[0133] A circular strain grid with a diameter of 2.0 mm is printed on the surface of a cold-rolled low-carbon deep-drawing steel sheet with an original thickness of 0.70 mm. A blanking die is used to complete the blanking and punching process to obtain a flat sheet.

[0134] Using the molding processes and molds corresponding to Examples 1, 2, 3, Comparative Example 2, and Comparative Example 3, a flat sheet with a printed circular strain grid is continuously stamped. Each group continuously produces 500 pieces, and the third process piece is obtained after the stretching process, the trimming and punching process one, the trimming and punching process two, and the flanging and shaping process.

[0135] An ultrasonic thickness gauge was used to perform multi-point gridded thickness measurements on the bottom of the deep cavity in the threshold area of ​​the third process component. The minimum measured thickness value was recorded, and the maximum thinning rate of the threshold area was calculated by combining it with the original thickness of 0.70 mm.

[0136] Macroscopic surface quality inspection was performed on 500 third-process parts in each group. The number of scrap parts with material stacking and wrinkling defects in the edge area of ​​the wheel arch flange was counted and the wrinkling scrap rate in the edge area of ​​the wheel arch flange was calculated. The number of scrap parts with macroscopic penetrating cracks and surface micro-neck cracks in the threshold area was counted and the deep cavity tensile crack scrap rate was calculated.

[0137] Table 3. Comparison of test data on material flow limit and surface defects of stamped parts in the deep cavity region of the threshold.

[0138] Test group Maximum thinning rate (%) in the threshold area Wrinkling scrap rate in the edge area of ​​wheel arch flange (%) Deep cavity tensile fracture scrap rate (%) Example 1 19.34 0.2 0.0 Example 2 22.87 0.4 0.6 Example 3 18.12 0.8 0.2 Comparative Example 2 31.45 14.6 18.2 Comparative Example 3 28.79 1.2 15.4

[0139] Conclusions and Analysis:

[0140] According to Table 3 and Figure 5According to the data, the wrinkling scrap rate of the flange edge area of ​​Comparative Example 2 was 14.6%, the deep cavity tear scrap rate was 18.2%, and the maximum thinning rate of the threshold area was 31.45%. Comparative Example 2 adopted a punch forming scheme and did not set wrinkle-absorbing ribs on the process supplement surface of the drawing die. During the stretching process, the sheet metal was stretched by two independent punches. The material supplement in the narrow joint area in the middle was insufficient, and the stress concentration directly caused the maximum thinning rate of the threshold area of ​​Comparative Example 2 to far exceed the safe forming limit of low carbon deep drawing steel sheet, resulting in tensile cracking. At the same time, due to the lack of tensile stress constraint, the free material at the outer edge under compressive stress instability directly caused wrinkling.

[0141] Examples 1, 2, and 3 employ a concave-formed butterfly-shaped cross-stretching configuration, merging two independent convex mold cavities into a continuous and wide overall convex mold central area. The sheet metal is no longer stretched separately but extends uniformly along the overall convex mold surface with extremely high consistency. Combined with wrinkle-absorbing ribs set on the corresponding process supplementary surface, the resistance of the material to bending and anti-bending deformation is greatly increased, and the stretched sheet metal is tightened. The wrinkling scrap rate of the wheel arch flange edge area in Examples 1, 2, and 3 is suppressed to below 0.8%, and the material flow state is improved.

[0142] The maximum thinning rate of the threshold area in Comparative Example 3 was 28.79%, and the deep cavity tear scrap rate was 15.4%. In the process supplement surface design of the drawing die in Comparative Example 3, the threshold area profile was not opened horizontally outward, resulting in a small draft angle in the local part of the deep cavity forming area. The small draft angle significantly increased the local friction coefficient and the sharp angle resistance of material flow during the forming process. The material of the external flange could not flow into the deep cavity for supplementation, and the material at the bottom of the deep cavity was overstretched.

[0143] In Examples 1, 2, and 3, the threshold area profile was opened horizontally outward by 15°, 10°, and 20° respectively in the process supplementary surface design of the drawing die. This temporarily increased the draft angle of the deep cavity, reduced the resistance of the sharp angle of the profile, and promoted the smooth flow of material into the deep cavity area of ​​the threshold. The maximum thinning rate of the threshold area in Examples 1, 2, and 3 was controlled within a safe range of less than 23%, and the highest scrap rate of deep cavity tearing was only 0.6%. Subsequently, the outwardly opened threshold area profile was squeezed and shrunken inward to restore the theoretical design shape by the forming insert set in the flanging and forming die. This eliminated the forming cracking risk in the deep cavity area while ensuring the dimensional accuracy of the final part.

[0144] Test Example 4: Comparison Test of Dimensional Accuracy of Beveled Normal Flanging and Demolding Breakage Rate

[0145] The forming dies corresponding to Examples 1, 2, 3 and Comparative Example 4 were installed on a multi-station mechanical press of the same tonnage, and the stamping cycle was set to 15 strokes / min.

[0146] Cold-rolled low-carbon deep-drawing steel sheet with a thickness of 0.70mm is fed into the press, and each group continuously performs 10,000 stamping cycles of trimming, side punching, separation, and flipping processes.

[0147] Record the number of mechanical overload and mold jamming alarm failures caused by the inability of the left and right car wheel cover outer panels to detach smoothly from the mold during 10,000 stamping cycles, and convert them into the failure rate per 10,000 pieces.

[0148] From the finished left and right car wheel arch panels produced continuously from Examples 1, 2, 3, and Comparative Example 4, an index was generated using a pseudo-random number generator, and 200 pieces from each were randomly selected as measurement samples.

[0149] The extracted measurement samples are fixed on a special inspection fixture. A coordinate measuring machine is used to perform an 8-point circumferential three-dimensional coordinate scan on the inner wall of the normal flange hole on the inclined surface of the outer panel of the left and right car wheel arches. The measured hole diameter value and the roundness deviation value are output. The number of samples with hole diameters within the design tolerance zone is counted to calculate the hole diameter tolerance compliance rate. The number of samples with roundness deviation values ​​exceeding 0.1 mm is counted to calculate the hole roundness deviation rate.

[0150] An industrial stereomicroscope with a magnification of 50x was used to observe the morphology of the normal flange edge of the extracted measurement sample along the cross section. The number of samples with macroscopic physical damage such as matrix fracture, edge tearing or flange unevenness was recorded, and the flange edge tearing and flange damage rate was calculated.

[0151] Table 4. Comparison Test Data of Dimensional Accuracy and Demolding Breakage Rate of Beveled Normal Hole Surface

[0152] Test group Bore diameter tolerance compliance rate (%) Orifice roundness deviation rate (%) Flanging edge tearing and breakage rate (%) Number of mold jamming alarm failures (times / 10,000 pieces) Example 1 98.6 1.1 0.5 0 Example 2 97.8 1.4 0.8 1 Example 3 98.9 0.9 0.4 0 Comparative Example 4 82.3 14.7 18.9 37

[0153] Conclusions and Analysis:

[0154] According to the data in Table 4, the tearing and flanging damage rate of the flanging edge corresponding to Comparative Example 4 is as high as 18.9%, the roundness deviation rate of the hole reaches 14.7%, the hole diameter tolerance compliance rate drops to 82.3%, and the number of mold jamming alarm failures is as high as 37 times per 10,000 pieces. Comparative Example 4 adopts a traditional simultaneous moving inclined wedge mechanism, and does not set the first stop guide plate 4, the second stop guide plate 9 and the stop drive wedge 3 in the punching separation flanging process on the trimming side. The flanging punch 12 and the flanging die 7 move simultaneously in the punching and return strokes. When the upper die holder 1 begins to rise after the blanking is completed, the normal flanging holes on the inclined surfaces of the left and right car wheel cover outer plates are completely nested between the flanging punch 12 and the flanging die 7, resulting in spatial interference. The simultaneous retraction causes the flanging punch 12 to be unable to exit first in the normal direction at the leading edge of the vertical lift. The upward vertical pulling force of the upper die holder 1 directly acts on the inner wall opening of the normal flanging hole on the inclined surface. The opening is subjected to the non-axial frictional force and upward pulling force of the metal forming punch, resulting in irreversible plastic deformation and physical fracture. The hole diameter and roundness deviate. The spatial interference ultimately leads to the equipment frequently triggering mechanical overload and die jamming alarms.

[0155] Examples 1, 2, and 3 employ a pause wedge-driven mold structure to complete the normal flanging process on the inclined surfaces of the left and right car wheel arch outer panels. Utilizing the displacement-time step distribution mechanism of the pause wedge mechanism, during the return demolding stage, the pause wedge-driven mold structure achieves reverse anti-interference sequence control through an internal return spring.

[0156] In the initial stage of lifting the upper mold base 1, the upper pressure plate 6 remains pressed, and the flipping punch 12 is pulled out and retracted first along the normal direction of the inclined plane, completely separating from the hole wall; then the stop drive wedge 3 retracts, causing the flipping die 7 to retract outward to release the spatial constraint; finally, the upper pressure plate 6 is released. In Examples 1, 2 and 3, the flipping punch 12 and the flipping die 7 do not have any non-axial scraping or pulling with the hole wall, the hole diameter tolerance compliance rate is maintained above 97%, the hole roundness deviation rate and the flipping edge tearing and flanging damage rate are both stable below 1.5%, and the number of mold jamming alarm failures is reduced to a low level of 0 to 1, eliminating the hole tearing and precision loss problems of the wheel cover outer plate with normal flipping holes during the demolding process.

Claims

1. A forming process for a wheel cover outer plate with normal flanges on an inclined surface, characterized in that, Includes the following steps: A blanking die is used to blank and punch the steel plate to obtain a flat sheet. The flat sheet is placed into a drawing die for stretching and forming. The stamping direction is set to concave forming. The back of the left car wheel cover outer panel and the right car wheel cover outer panel are joined together. The wheel opening surfaces of the left car wheel cover outer panel and the right car wheel cover outer panel are both set to face outward. Wrinkle-removing ribs are set on the process supplement surface of the drawing die. The sill area profiles of the left car wheel cover outer panel and the sill area profiles of the right car wheel cover outer panel are opened horizontally outward to obtain the stretched part. Remove the waste material from the stretching process part, complete the stamping of part of the flange hole and side wall hole, and obtain the first process part. Remove the remaining edge waste material of the first process part, complete the stamping of the remaining flange hole and side wall hole, and obtain the second process part. Flang the second process part, and squeeze and shrink the sill area profile that opens outward through the flanging forming die to obtain the third process part. Remove the waste material from the docking area of ​​the third process part, separate the left car wheel cover outer plate from the right car wheel cover outer plate, and drive the lateral flanging die (7) to the working position of the left car wheel cover outer plate surface and the right car wheel cover outer plate surface after the separation during the first stroke interval of the upper die base (1) pressing down. During the second stroke interval of the upper die base (1) pressing down, drive the flanging punch (12) of the lower die to move along the slope normal direction and insert into the flanging die (7) to obtain the wheel cover outer plate.

2. The forming process of a wheel cover outer plate with normal flanges on an inclined surface according to claim 1, characterized in that, The specific steps of aligning the left wheel arch outer panel with the back of the right wheel arch outer panel include: The wheel arch surface of the left car wheel cover outer panel and the wheel arch surface of the right car wheel cover outer panel are integrally arranged on the central area of ​​a punch of the drawing die.

3. The forming process of a wheel cover outer plate with normal flanges on an inclined surface according to claim 1, characterized in that, Within the range of the upper die holder (1) rising and retracting, the piercing punch (12) is pulled out and retracted downwards; after the piercing punch (12) retracts, the piercing die (7) retracts outwards.

4. The forming process of a wheel cover outer plate with normal flanges on an inclined surface according to claim 1, characterized in that, The molding process uses a mold with an upper pressure plate (6), a stop drive wedge (3) and a first conduction wedge (8); The specific working positions of the lateral flanging die (7) reaching the surface of the left and right car wheel arch outer panels after bonding and separation within the first stroke range of the upper die holder (1) pressing down include: The upper mold base (1) descends from the highest point, and the upper pressure plate (6) contacts the separated left car wheel cover outer plate and the right car wheel cover outer plate and stops relative movement; During the first stroke interval as the upper die holder (1) continues to descend, the pause drive wedge (3) drives the first transmission wedge (8) to slide horizontally, and the first transmission wedge (8) pushes the piercing die (7) to slide along the slope normal to the working position; The first travel range is 8mm to 12mm.

5. The forming process of a wheel cover outer plate with normal flanges on an inclined surface according to claim 4, characterized in that, When the driving-side flanging die (7) reaches the working position of the left and right car wheel arch outer panel surfaces after bonding and separation: The vertical straight segment of the first stop guide plate (4) fixedly mounted on the stop drive wedge (3) on the upper mold base (1) slides and fits relative to the vertical straight segment of the second stop guide plate (9) fixedly mounted on the outside of the first transmission wedge (8).

6. The forming process of a wheel cover outer plate with normal flange holes on an inclined surface according to claim 4, characterized in that, The mold also has a drive wedge (2) and a lower mold second conduction wedge (13); During the second stroke interval of the upper die holder (1) continuing to press down, the piercing punch (12) driving the lower die moves along the normal direction of the inclined plane and inserts into the piercing die (7), specifically including: As the upper die holder (1) continues to descend within the second stroke range, the driving wedge (2) drives the lower die second transmission wedge (13) to slide horizontally. The lower die second transmission wedge (13) converts the horizontal thrust into a thrust that pushes the flipping punch (12) to move along the slope normal. The distance between the end point of the downward displacement in the second travel interval and the highest point is 18mm to 22mm.

7. The forming process of a wheel cover outer plate with normal flanges on an inclined surface according to claim 1, characterized in that, The first batch of independent wedge mechanisms arranged on the edge of the sidewall of the workpiece in the stretching process are used to complete part of the sidewall hole stamping; The remaining sidewall holes are punched using a second batch of independent wedge mechanisms arranged on the edge of the sidewall of the first workpiece.

8. The forming process of a wheel cover outer plate with normal flanges on an inclined surface according to claim 1, characterized in that, After obtaining the stretched workpiece, a six-axis industrial robot end effector equipped with a vacuum suction cup assembly is used to transport the stretched workpiece. The vacuum suction cup assembly adheres to the flat back, and the spatial angle between the force-bearing surface of the vacuum suction cup assembly and the absolute horizontal plane is within 5°.

9. The forming process of a wheel cover outer plate with normal flanges on an inclined surface according to claim 1, characterized in that, The sill area profile of the left wheel arch outer panel and the sill area profile of the right wheel arch outer panel are opened horizontally outward to 10° to 20°.

10. A forming apparatus for implementing the forming process of a wheel cover outer plate with normal flanges on an inclined surface as described in any one of claims 1-9, characterized in that, include: The upper module includes an upper mold base (1), a drive wedge (2), a stop drive wedge (3), a first stop guide plate (4), and a nitrogen cylinder (5). The first stop guide plate (4) is fixedly installed on the stop drive wedge (3). The drive wedge (2) and the stop drive wedge (3) are both fixedly connected to the lower surface of the upper mold base (1). The nitrogen cylinder (5) is fixed on the upper mold base (1), and the output end of the nitrogen cylinder (5) is set downward. The side-feeding assembly includes an upper pressure plate (6) with an inner cavity support structure, a piercing die (7), a first transmission wedge (8), a second stop guide plate (9), a piercing die return spring (15), and a first transmission wedge return spring (16). The upper pressure plate (6) receives the output pressure of the nitrogen cylinder (5). The piercing die (7) and the first transmission wedge (8) are movably mounted on the inner guide seat of the upper pressure plate (6). The second stop guide plate (9) is fixedly mounted on the outer side of the first transmission wedge (8) and slides in cooperation with the first stop guide plate (4). The normal stamping assembly includes a lower die base (11), a piercing punch (12), a second guide wedge (13), a lower support punch (14) for supporting the bottom of the workpiece (10) to be pierced, a piercing punch return spring (17), and a second guide wedge return spring (18). The piercing punch (12) and the second guide wedge (13) are slidably disposed on the lower die base (11). The pause drive wedge (3) cooperates with the first conduction wedge (8) to drive the flipping die (7) to move; the drive wedge (2) cooperates with the second conduction wedge (13) to drive the flipping punch (12) to insert into the flipping die (7) after the flipping die (7) is in contact.

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