Stamping method and stamping die for part with local variable cross section

Abstract

The invention relates to a local variable cross-section part stamping method and stamping die. The method comprises the following steps that S1, a pre-notch is formed, specifically, a pre-notch in a preset shape is cut in a material belt under the cooperation of a pre-notch male die and a pre-notch reverse pressing plate; s2, local flattening is conducted, on the basis of the pre-cut opening, thickness reduction flattening treatment is conducted on the target area, and a variable cross-section structure is formed; the flattening punch extrudes the target area of the material belt to complete flattening, so that the material in the flattening area is extruded and flows towards the direction of the pre-cut opening; and S3, blanking is conducted, blanking of the outline of the part is completed under the mutual cooperation of a blanking punch-die and a blanking reverse pressing plate, and for the variable cross-section structure, the blanking reverse pressing plate is provided with a local protrusion matched with the variable cross-section structure. Different from the prior art, high-precision integrated forming of the part with the flattening characteristic is achieved, the production efficiency is greatly improved, the machining takt is shortened, and the manufacturing cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of precision stamping processing of metal plates, and in particular to a stamping method and a stamping die for a part with a locally variable cross-section. Background Art

[0002] Traditional blanking processes utilize the gap between the punch and die to shear and fracture the material. This is suitable for parts of uniform thickness. However, for parts with variable cross-sections, the shear, lateral, and impact forces experienced by the punch and die cutting edges at different cross-sectional locations vary significantly during the blanking process. This can lead to excessive stress in localized areas of the mold, causing elastic or even plastic deformation, compromising mold precision and shortening mold life. Furthermore, the material's varying deformation resistance and flow rates across different cross-sectional areas lead to inconsistent shear surface quality, making dimensional accuracy difficult to guarantee.

[0003] More information related to the above technical solutions can be found in the following documents:

[0004] In the patent publication number CN102689149A, a continuous punching and forging precision forming process for automobile retaining frame parts is disclosed. The steel plate is clamped by feed rollers and fed into a multi-station punching and forging die. The workpiece is formed in four steps, namely the first step: punching the inner hole → the second step: flattening / extruding the protrusion → the third step: extruding the hole and forming the boss → the fourth step: punching the boss hole / punching the inner hole / blank to obtain the final workpiece.

[0005] In the process of implementing the present invention, the inventors found that the prior art has the following problems:

[0006] In the prior art, the fine blanking process and the flattening process are carried out in two separate devices. The fine blanking process is carried out after the flattening process, resulting in poor quality of the shear surface of the variable-section parts, low dimensional accuracy, and low production efficiency. Summary of the Invention

[0007] In view of the above problems, the present application provides a stamping method and stamping die for locally variable-section parts, which are used to solve the technical problems in the prior art that the fine stamping process and the flattening process are carried out by two separate devices, the fine stamping process is carried out after the flattening process, the shear surface quality of the variable-section parts is poor, the dimensional accuracy is low, and the production efficiency is low.

[0008] To achieve the above objectives, in a first aspect, the present application provides a method for stamping a part with a partially variable cross-section, comprising the following steps:

[0009] S1, pre-incision;

[0010] The blank holding force is provided by the blank holding ring push rod, the blank holding ring presses the material strip downward, the pre-cut punch moves downward under the action of the blanking force, and the pre-cut counter-pressure plate provides counter-pressure upward. At the same time, under the action of the pre-cut punch, the pre-cut counter-pressure plate moves downward, and the pre-cut punch and the pre-cut counter-pressure plate cooperate to cut a pre-cut of a preset shape on the material strip;

[0011] S2, local flattening, based on the pre-cut, the target area is thinned and flattened to form a variable cross-section structure;

[0012] The material strip moves downward along with the blank holder under the action of the blank holder force. The flattening punch cooperates with the blank holder to squeeze the target area of ​​the material strip to complete the flattening, so that the material in the flattening area is squeezed and flows toward the pre-cut direction.

[0013] S3, blanking;

[0014] The blanking force is provided by the blanking ring push rod, and the blanking ring presses the material strip downward. The blanking punch and die move downward under the action of the blanking force. The blanking counter-pressure plate provides counter-pressure upward. At the same time, under the action of the blanking punch and die, the blanking counter-pressure plate moves downward. The blanking punch and die and the blanking counter-pressure plate cooperate with each other to complete the blanking of the part's outer contour. For variable cross-section structures, the blanking counter-pressure plate is provided with a local protrusion that matches the variable cross-section structure.

[0015] Different from the existing technology, the above technical solution cuts the material strip through pre-cutting to form a cavity on the material strip, which can provide material flow space for the subsequent flattening process, avoid excessive accumulation of material in the flattening area, improve the forming quality, and ensure that there is enough overlapping material when blanking after the flattening process, without destroying the step distance and guidance of the material strip; by thinning and flattening the target area on the basis of the pre-cutting, a variable cross-section structure is formed, and the flattening punch acts on the pre-cutting area to squeeze the material in the flattening area and flow in the direction of the pre-cutting. The flattening thickness is precisely controlled, the material flows smoothly, and there are no defects such as collapse and tearing; the blanking convex and concave dies and the blanking back pressure plate cooperate with each other to complete the external flattening of the parts For blanking of variable-section contours, local raised counter-pressure plates are provided for variable-section areas to achieve uniform force in multiple areas. In this way, high-precision integrated forming of parts with flattening features is achieved. The flattening process requirements are introduced on the basis of traditional fine blanking process, and integrated high-precision forming of complex geometric shapes is achieved. The product contour is clear and the flatness of the flattened area is high, which meets the technical requirements of high-end equipment manufacturing for precision special-shaped stamping parts. The flattening and fine blanking processes are integrated into a composite forming process, and a process combination of first cutting, then flattening and finally blanking is adopted. The coordinated forming of the flattened structure and the fine blanking contour is achieved without adding additional processes, which greatly improves production efficiency, shortens processing time and reduces manufacturing costs.

[0016] As an embodiment of the present invention, in S1 pre-cutting, the pre-cutting punch is a punch with a preset shape;

[0017] The narrowest width of the punch of the preset shape is calculated based on the thickness of the material strip, the thickness of the material strip after flattening, the area of ​​the flattening area, and the outer contour of the flattening area. The narrowest width of the punch of the preset shape is greater than the distance required for the material to flow.

[0018] By presetting the narrowest width of the punch shape, the distance required for material flow is calculated. The distance required for material flow and the thickness of the material strip after flattening are used to obtain the distance between the pre-cut contour and the outer contour of the finished part, which is applied to the pre-cut punch.

[0019] In this way, generally speaking, the wider the preset shape punch is, the better the strength is and it is not easy to be damaged. However, it will also cut out more material strips and add more waste. It is necessary to calculate the narrowest width of a suitable preset shape punch. The narrowest area of ​​the preset shape punch needs to ensure a certain width to ensure subsequent processing. It cannot be made particularly narrow to save material. At the same time, it cannot be made particularly wide to add more waste. By making the narrowest width of the preset shape punch greater than the distance required for material flow, it is ensured that the material has sufficient flow space during the subsequent flattening process. The preset shape punch is a strip structure. In this application, it is Z-shaped. It is necessary to calculate the distance between the preset shape punch and the flattening area. By reasonably setting the pre-cut size, a free boundary is formed to allow the material in the subsequent flattening area to flow in a directional manner, avoiding forming defects such as fracturing and material tearing.

[0020] As an embodiment of the present invention, the narrowest width x2 of the punch of the preset shape is calculated by the thickness of the strip, the thickness of the strip after flattening, the area of ​​the flattening area, and the outer contour of the flattening area. The calculation formula is:

[0021]

[0022] Where A is the area of ​​the flattened forming area, t1 is the thickness of the strip, t2 is the thickness of the strip after flattening, and l is the outer contour of the flattened area.

[0023] In this way, the narrowest width of the preset shape punch is calculated through the thickness of the material strip, the thickness of the material strip after flattening, the area of ​​the flattening forming area, and the outer contour of the flattening area. A systematic incision size calculation method is established. In view of the influence of the flattening process on the plastic flow behavior of the material, a residual incision size design formula suitable for different plate thicknesses, material strengths and flattening ratios is proposed.

[0024] As an embodiment of the present invention, the step of calculating the distance required for material flow by presetting the narrowest width of the shape punch is that, during the flattening process, the flow distance is different for different shape contours, and the narrowest width of the preset shape punch is multiplied by the corresponding proportional coefficient to obtain the distance required for material flow.

[0025] In this way, during the flattening process, the flow distance is different for different contours and should be multiplied by the corresponding proportional coefficient to ensure sufficient flow space.

[0026] As an embodiment of the present invention, the distance x between the pre-cut profile and the outer contour of the finished part is obtained by the distance required for material flow and the thickness of the material strip after flattening. The calculation formula is:

[0027] x=t2+2.5-x1

[0028] Where x1 is the distance required for the material to flow.

[0029] In this way, the distance required for material flow and the thickness of the material strip after flattening are used to obtain the distance between the pre-cut contour and the outer contour of the finished part. The contour of the preset shape punch maintains a deviation from the final finished product contour. The inner contour size of the punch is consistent with the outer contour of the final part and expands outward. By reasonably setting the pre-cut size, a free boundary is formed, allowing the material in the subsequent flattening area to flow in a directional manner, avoiding forming defects such as fracturing and material tearing.

[0030] As an embodiment of the present invention, in the step of local flattening in S2, the target area is subjected to a thickness thinning and flattening process based on the pre-cut to form a variable cross-section structure,

[0031] When the flattening punch is a downward flattening punch, the material strip moves downward along with the blank holder under the action of the blank holder force, the flattening punch is fixed, and the blank holder continues to move downward to squeeze the material strip to complete the flattening;

[0032] When the flattening punch is an upper flattening punch, the material strip moves downward along with the blank holder under the action of the blank holder force. After the material strip contacts the die, the blank holder force fixes the material strip. The flattening punch moves downward under the action of the blanking force, squeezes the material strip, and completes the flattening.

[0033] In this way, the punch can be placed up or down according to the flattening direction, so that the material in the flattening area is squeezed and flows toward the pre-cut direction.

[0034] As an embodiment of the present invention, in the local flattening S2, the target area is subjected to thickness thinning and flattening treatment on the basis of the pre-cut to form a variable cross-section structure step, and uniform pressure is applied to the variable cross-section area by a flattening punch with a preset curved surface shape.

[0035] In this way, during the extrusion process, uniform pressure is applied to the variable cross-section area through the flattening punch with a preset curved surface shape. The edge of the flattening punch has corresponding chamfers and transitions to achieve a uniform transition, avoiding defects such as tearing of the part material. The preset curved surface shape is designed according to the target part, so that the variable cross-section area on the part is uniformly transitioned, avoiding sudden flattening of the part and defects such as material tearing.

[0036] To achieve the above-mentioned purpose, in a second aspect, the inventor provides a stamping die for a part with a partially variable cross-section, which is used to perform the stamping method for a part with a partially variable cross-section as described in any one of the above-mentioned methods, comprising an upper template, an upper pad, an upper fixing plate, a lower fixing plate, a lower pad, a lower template, a blank holder, a blank holder seat, a pre-cut punch, a pre-cut counter-pressure plate, a flattening punch, a die, a blanking punch and a blanking counter-pressure plate;

[0037] The upper template, the upper pad, and the upper fixing plate are arranged from top to bottom in a vertical direction;

[0038] The concave mold, the lower fixing plate, the lower pad, and the lower template are arranged from top to bottom in a vertical direction;

[0039] The blank holder seat is sleeved on the outside of the blank holder ring and connected to the blank holder ring, the pre-cut punch is relatively arranged above the pre-cut back pressure plate, the bottom shape of the pre-cut punch is a preset shape, the flattening punch is arranged behind the pre-cut punch and the pre-cut back pressure plate in the production direction, the blanking convex and concave dies and the blanking back pressure plate are arranged behind the flattening punch in the production direction, and the blanking convex and concave dies are relatively arranged above the blanking back pressure plate.

[0040] Different from the existing technology, the local variable cross-section part stamping die of the technical solution of this application realizes high-precision integrated forming of parts with flattening features, introduces flattening process requirements on the basis of traditional fine stamping process, and realizes integrated high-precision forming of complex geometric morphology. The product contour is clear and the flattened area has high flatness, which meets the technical requirements of high-end equipment manufacturing for precision special-shaped stamping parts; the flattening and fine stamping processes are integrated into a composite forming process, and a process combination method of first cutting, then flattening and finally blanking is adopted. Combined with the collaborative working mechanism of pre-cut punch, flattening punch, blanking convex and concave die and fine stamping die, the collaborative forming of flattened structure and fine stamping contour is realized without adding additional processes, which greatly improves production efficiency, shortens processing cycle and reduces manufacturing cost.

[0041] As an embodiment of the present invention, the shape of the contact surface of the flattening punch is a preset curved surface shape.

[0042] In this way, uniform pressure is applied to the variable cross-section area through a flattening punch with a preset curved surface shape. The edge of the flattening punch has corresponding chamfers and transitions to achieve a uniform transition and avoid defects such as tearing of part materials. The preset curved surface shape is designed according to the target part so that the variable cross-section area on the part has a uniform transition and avoids sudden flattening of the part and defects such as material tearing.

[0043] As an embodiment of the present invention, the top of the blanking back pressure plate is provided with a local protrusion that matches the variable cross-section structure.

[0044] In this way, a local raised back pressure plate is provided for the variable cross-section area to achieve uniform force in multiple areas. The shape of the local raised portion matches the variable cross-section structure, and the variable cross-section structure after flattening is supported, so that the semi-processed parts can fit on the back pressure plate. In the real-time blanking and punching process, the semi-processed parts can be stable and the punching force can be uniform.

[0045] The above-mentioned records related to the content of the invention are only an overview of the technical solution of this application. In order to enable ordinary technicians in this field to understand the technical solution of this application more clearly, and then implement it according to the text of the specification and the contents recorded in the drawings, and to make the above-mentioned purposes and other purposes, features and advantages of this application easier to understand, the following is an explanation in combination with the specific implementation methods and drawings of this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, characteristics and effects of the specific embodiments of this application and other related contents, and are not to be considered as limiting this application.

[0047] In the drawings of the specification:

[0048] Figure 1 This is a logic diagram of a method for stamping a part with a partially variable cross-section according to an embodiment of the present application;

[0049] Figure 2 This is a schematic structural diagram of a stamping die for a part with a partially variable cross-section according to an embodiment of the present application;

[0050] Figure 3 This is a schematic structural diagram of a pre-cut punch and a pre-cut back pressure plate according to an embodiment of the present application;

[0051] Figure 4 A top view of a pre-cut punch and a material strip according to an embodiment of the present application;

[0052] Figure 5 A schematic diagram of the pre-cut shape and the flattened area according to an embodiment of the present application;

[0053] Figure 6 A schematic diagram of the distance x required for material flow according to one embodiment of the present application;

[0054] Figure 7 This is a schematic diagram of the flow of locally flattened materials according to one embodiment of the present application;

[0055] Figure 8 This is a schematic structural diagram of a flattening punch according to an embodiment of the present application;

[0056] Figure 9 This is a schematic structural diagram of a blanking male and female die and a blanking counter-pressure plate according to an embodiment of the present application;

[0057] Figure 10 This is a structural schematic diagram of another cross-sectional angle of the blanking male and female dies and the blanking back pressure plate of one embodiment of the present application.

[0058] The reference numerals in the above drawings are described as follows:

[0059] x, the distance between the pre-cut contour and the outer contour of the finished part;

[0060] 1. Upper template, 2. Upper pad, 3. Upper fixed plate, 4. Lower fixed plate, 5. Lower pad, 6. Lower template, 7. Blank holder, 8. Blank holder seat, 9. Pre-cut counter-pressure plate, 10. Pre-cut punch, 11. Flattening punch, 12. Blanking convex and concave dies, 13. Blanking counter-pressure plate, 14. Local protrusion, 15. Material strip, 16. Concave die, 17. Flattening area, 18. Target part. DETAILED DESCRIPTION

[0061] In order to explain in detail the possible application scenarios, technical principles, specific solutions that can be implemented, and the purpose and effects of this application, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of this application and are therefore only examples and are not intended to limit the scope of protection of this application.

[0062] References to "embodiments" herein mean that the specific features, structures, or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the word "embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or relevance to other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the various technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution.

[0063] Unless otherwise defined, the technical terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms herein is only for describing specific embodiments and is not intended to limit this application.

[0064] In the description of this application, the term "and / or" is used to describe a logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and both A and B exist. In addition, the character " / " in this document generally indicates that the objects before and after are in a logical "or" relationship.

[0065] In this application, terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual quantity, priority or sequence relationship between these entities or operations.

[0066] Without further limitations, in this application, the words "include", "comprise", "have" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those defined elements, but also other elements not explicitly listed, or elements inherent to such process, method or product.

[0067] Consistent with the understanding in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceed" are understood to exclude the number itself; expressions such as "above," "below," and "within" are understood to include the number itself. Furthermore, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this manner, such as "multiple groups," "multiple times," etc., unless otherwise specifically defined.

[0068] In the prior art, the fine blanking process and the flattening process are carried out in two separate devices. The fine blanking process is carried out after the flattening process, resulting in poor quality of the shear surface of the variable-section parts, low dimensional accuracy, and low production efficiency.

[0069] In view of this, the embodiment of the present application provides a method and stamping die for stamping parts with local variable cross-sections, comprising the following steps: S1, pre-cutting, wherein the pre-cutting punch 10 cooperates with the pre-cutting back pressure plate 9 to cut a pre-cut of a preset shape into the material strip 15; S2, local flattening, wherein, based on the pre-cutting, the target area is subjected to a thickness thinning and flattening process to form a variable cross-section structure, so that the material in the flattened area 17 is squeezed and flows toward the pre-cutting; S3, blanking, wherein the blanking punch and concave die 12 cooperates with the blanking back pressure plate 13 to complete the blanking of the part's outer contour. For the variable cross-section structure, the blanking back pressure plate 13 is provided with a local protrusion 14 that matches the variable cross-section structure. The flattening and fine blanking processes are integrated into a composite forming process, and a process combination of first cutting, then flattening, and finally blanking is adopted. This achieves the coordinated forming of the flattened structure and the fine blanking contour without adding additional steps, greatly improving production efficiency, shortening processing time, and reducing manufacturing costs.

[0070] According to some embodiments of this application, please refer to Figures 1 to 10 This embodiment relates to a method for stamping a part with a local variable cross-section, comprising the following steps:

[0071] S1, pre-incision;

[0072] The blank holding force is provided by the top rod of the blank holding ring 7, and the blank holding ring 7 presses the material strip 15 downward. The pre-cut punch 10 moves downward under the action of the blanking force. At the same time, the pre-cut counter-pressure plate 9 provides counter-pressure upward. Under the action of the pre-cut punch 10, the pre-cut counter-pressure plate 9 moves downward. The pre-cut punch 10 and the pre-cut counter-pressure plate 9 cooperate to cut a pre-cut of a preset shape on the material strip 15.

[0073] S2, local flattening, based on the pre-cut, the target area is thinned and flattened to form a variable cross-section structure;

[0074] The material strip 15 moves downward along with the blank holder 7 under the action of the blank holder force, and the flattening punch 11 cooperates with the blank holder 7 to squeeze the target area of ​​the material strip 15 to complete the flattening, so that the material in the flattening area 17 is squeezed and flows toward the pre-cut direction;

[0075] S3, blanking;

[0076] The blanking force is provided by the push rod of the blanking ring 7, and the blanking ring 7 presses the material strip 15 downward. The blanking punch and die 12 moves downward under the action of the blanking force. The blanking back pressure plate 13 provides upward back pressure. At the same time, under the action of the blanking punch and die 12, the blanking back pressure plate 13 moves downward. The blanking punch and die 12 and the blanking back pressure plate 13 cooperate with each other to complete the blanking of the part's outer contour. For the variable cross-section structure, the blanking back pressure plate 13 is provided with a local protrusion 14 that cooperates with the variable cross-section structure.

[0077] In this embodiment, blanking is accomplished by a progressive die structure, and the process is divided into three steps: pre-cutting, flattening, and precision blanking.

[0078] In the pre-cutting step, the blanking force is provided by the top rod of the blank holder 7, and the blank holder 7 presses the material strip 15 downward to prevent the material from sliding sideways or wrinkling, fixing the material strip. The pre-cut punch 10 moves downward under the action of the blanking force, and the pre-cut counter-pressure plate 9 provides counter-pressure upward. At the same time, under the action of the pre-cut punch 10, the pre-cut counter-pressure plate 9 moves downward. The pre-cut punch 10 cuts a cavity in the material strip 15 to provide material flow space for the subsequent flattening process, avoid excessive accumulation of material in the flattening area, improve the forming quality, and ensure that there is enough overlapping material when blanking after the flattening process, while not damaging the pitch and guide of the material strip. The pre-cut blanking structure adopts a conventional fine blanking process structure to avoid edge tearing and improve the quality of the subsequent flattening process.

[0079] In the flattening step, the target area is thinned and flattened on the basis of the pre-cut to form a variable cross-section structure. The variable cross-section is actually flattening. From the perspective of the part cross-section, the original thickness of 5mm is changed to 3mm, which is a variable cross-section. The flattening punch with a preset curved surface shape applies uniform pressure to the variable cross-section area, so that the material in the flattened area is squeezed and flows toward the pre-cut direction. The flattened shape is consistent, the thickness is precisely controlled, the material flows smoothly, and there are no defects such as collapse and tearing.

[0080] During the blanking step, the two-cavity parts in the present method for stamping partially variable cross-section parts adopt an offset blanking method to distribute the blanking load. The blanking force is provided by the ejector rod of the blank holder 7, which presses the material strip 15 downward to prevent lateral slippage or wrinkling of the material and fix the material strip. Under the action of the blanking punch and die 12, the blanking counter-pressure plate 13 moves downward. The blanking punch and die 12 and the blanking counter-pressure plate 13 cooperate to complete the blanking of the part's outer contour, completing the fine blanking of the part's final outer contour. For variable cross-section structures, the blanking back pressure plate 13 is provided with a local protrusion 14 that cooperates with the variable cross-section structure to achieve uniform force in multiple areas. The local protrusion 14 on the blanking back pressure plate 13 supports the variable cross-section structure in the vertical direction; in addition, for different thickness areas, the die 16 is designed with different blanking gaps to achieve gap control and regional adaptive adjustment. The blanking gaps of different thickness areas of variable cross-section parts are different. The blanking gap refers to the gap between the blanking convex and concave dies 12 and the die 16. The blanking gap is support in the horizontal direction.

[0081] In this embodiment, the material strip 15 is cut by pre-cutting to form a cavity on the material strip 15, which can provide material flow space for the subsequent flattening process, avoid excessive accumulation of material in the flattening area 17, improve the forming quality, and ensure that there is sufficient overlapping material when blanking after the flattening process, while not damaging the pitch and guide of the material strip 15; by thinning and flattening the target area on the basis of the pre-cut, a variable cross-section structure is formed, and the flattening punch 11 acts on the pre-cut area to squeeze the material in the flattening area 17 and flow in the direction of the pre-cut. The flattening thickness is accurately controlled, the material flows smoothly, and defects such as collapse and tearing do not occur; the blanking convex and concave dies 12 and the blanking back pressure plate 13 cooperate with each other to complete the blanking of the part contour, and a local protrusion 14 back pressure plate is provided for the variable cross-section area to achieve uniform force in multiple areas;

[0082] In this way, high-precision integrated forming of parts with flattening features is achieved. The flattening process requirements are introduced on the basis of the traditional fine blanking process, and integrated high-precision forming of complex geometric shapes is achieved. The product contour is clear and the flattened area has high flatness, which meets the technical requirements of high-end equipment manufacturing for precision special-shaped stamping parts; the flattening and fine blanking processes are integrated into a composite forming process, and a process combination method of first cutting, then flattening and finally blanking is adopted. The coordinated forming of the flattened structure and the fine blanking contour is achieved without adding additional processes, which greatly improves production efficiency, shortens processing time and reduces manufacturing costs.

[0083] According to some embodiments of the present application, optionally, Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 、 Figure 7 As shown, in the S1 pre-cut, the pre-cut punch 10 is a punch with a preset shape;

[0084] The narrowest width of the punch of the preset shape is calculated based on the thickness of the material strip 15, the thickness of the material strip 15 after flattening, the area of ​​the flattening region, and the outer contour of the flattening region 17. The narrowest width of the punch of the preset shape is greater than the distance required for the material to flow.

[0085] By presetting the narrowest width of the punch, the distance required for material flow is calculated. By the distance required for material flow and the thickness of the material strip 15 after flattening, the distance between the pre-cut contour and the outer contour of the finished part is obtained (such as Figure 6 The distance indicated by x in the figure is applied to the pre-cut punch 10.

[0086] In this way, generally speaking, the wider the preset shape punch is, the better its strength is and it is not easy to be damaged. However, it will also cut out more material strips 15 and increase more waste. It is necessary to calculate the narrowest width of a suitable preset shape punch. The narrowest area of ​​the preset shape punch needs to ensure a certain width to ensure subsequent processing. It cannot be made particularly narrow to save material. At the same time, it cannot be made particularly wide to increase more waste. By making the narrowest width of the preset shape punch greater than the distance required for material flow, it is ensured that the material has sufficient flow space during the subsequent flattening process. In this application, the preset shape punch is a strip structure with a Z-shaped cross-section, so it is necessary to calculate the distance between the preset shape punch and the flattening area 17, and form a free boundary by reasonably setting the pre-cut size, so that the material in the subsequent flattening area 17 can flow in a directional manner to avoid forming defects such as fracturing and material tearing.

[0087] According to some embodiments of the present application, optionally, Figure 6 As shown, the narrowest width x2 of the preset shape punch is calculated by the thickness of the material strip 15, the thickness of the material strip 15 after flattening, the area A of the flattening forming area, and the outer contour of the flattening area 17. The calculation formula is:

[0088]

[0089] Wherein, A is the area of ​​the flattened forming region, t1 is the thickness of the material strip 15 , t2 is the thickness of the material strip 15 after flattening, and l is the outer contour of the flattened region 17 .

[0090] In this way, the narrowest width of the preset shape punch is calculated through the thickness of the material strip 15, the thickness of the material strip 15 after flattening, the area of ​​the flattening area, and the outer contour of the flattening area 17. A systematic incision size calculation method is established. In view of the influence of the flattening process on the plastic flow behavior of the material, a residual incision size design formula suitable for different plate thicknesses, material strengths and flattening ratios is proposed.

[0091] According to some embodiments of the present application, optionally, Figure 5 As shown, the steps for calculating the distance required for material flow by the narrowest width of the preset shape punch are as follows: during the flattening process, the flow distance is different for different shape contours, and the narrowest width of the preset shape punch is multiplied by the corresponding proportional coefficient to obtain the distance required for material flow.

[0092] In this embodiment, the pre-cut punch 10 (preset shape punch) is a strip-shaped structure with a Z-shaped cross-section;

[0093] Therefore, during the flattening process, the flow distance varies for different contours and should be multiplied by the corresponding proportional coefficient to ensure sufficient flow space. The specific proportional coefficients are shown in the following table:

[0094] Convex <![CDATA[x1=(0.9~1)x2]]> straight line <![CDATA[x1=(0.96~1.005)x2]]> Concave type <![CDATA[x1=(1~1.1)x2]]>

[0095] The x2 in the table above is the narrowest width x2 of the preset shape punch that appears in the above formula, which gives the distance x1 required for material flow.

[0096] According to some embodiments of the present application, optionally, the distance x (e.g., the distance x) between the pre-cut profile and the outer contour of the finished part can be obtained by the distance required for the material to flow and the thickness of the strip 15 after flattening. Figure 6 The distance indicated by x in the figure is calculated as follows:

[0097] x=t2+2.5-x1

[0098] Where x1 is the distance required for the material to flow.

[0099] In this embodiment, a systematic method for calculating the cutout size is established. In view of the influence of the flattening process on the plastic flow behavior of the material, a residual cutout size design formula applicable to different plate thicknesses, material strengths and flattening ratios is proposed.

[0100] Thus, the distance between the pre-cut contour and the outer contour of the finished part is obtained by the distance required for the material to flow and the thickness of the strip 15 after flattening. Figure 6 The distance indicated by x in the middle), the outline of the preset shape punch maintains a deviation from the outline of the final finished product, the inner contour size of the punch is consistent with the outer contour of the final part, and expands outward. By reasonably setting the pre-cut size, a free boundary is formed, so that the material in the subsequent flattening area 17 flows in a directional manner, avoiding forming defects such as fracturing and material tearing.

[0101] According to some embodiments of the present application, optionally, in the step of locally flattening in S2, the target area is subjected to a thickness reduction and flattening process based on the pre-cut to form a variable cross-section structure,

[0102] When the flattening punch 11 is a bottom-mounted flattening punch 11, the material strip 15 moves downward along with the blank holder 7 under the action of the blank holder force, the flattening punch 11 is fixed, and the blank holder 7 continues to move downward to squeeze the material strip 15 to complete the flattening;

[0103] When the flattening punch 11 is an upper flattening punch 11, the material strip 15 moves downward along with the blanking ring 7 under the action of the blanking force. After the material strip 15 contacts the die 16, the blanking force fixes the material strip 15. The flattening punch 11 moves downward under the action of the blanking force, squeezes the material strip 15, and completes the flattening.

[0104] like Figure 8 As shown, in this embodiment, the flattening punch 11 is a lower flattening punch 11, and both the lower flattening punch 11 and the upper flattening punch 11 are within the protection scope of this embodiment.

[0105] In this way, the punch can be placed upward or downward according to the flattening direction, so that the material in the flattening area 17 is squeezed and flows in the direction of the pre-cut.

[0106] According to some embodiments of the present application, optionally, in the local flattening S2, the target area is subjected to thickness thinning and flattening treatment based on the pre-cut to form a variable cross-section structure, and in the step of forming a variable cross-section structure, a flattening punch 11 with a preset curved surface shape is used to apply uniform pressure to the variable cross-section area.

[0107] In this way, during the extrusion process, uniform pressure is applied to the variable cross-section area through the flattening punch 11 with a preset curved surface shape. The edge of the flattening punch 11 has corresponding chamfers and transitions to achieve a uniform transition and avoid defects such as tearing of the part material. The preset curved surface shape is designed according to the target part 18, so that the variable cross-section area on the part is uniformly transitioned, avoiding sudden flattening of the part and defects such as material tearing.

[0108] The key technical points in this embodiment are: pre-cut design for the variable cross-section area, the pre-cut is a central opening structure, which can effectively alleviate the problem of uneven flow of materials during flattening; the pre-cut position before flattening is optimized to control the distance x between the pre-cut contour and the boundary of the final finished product. The distance x is a key parameter to ensure the deformation accuracy of the material after flattening and the clarity of the final contour.

[0109] The process of this application is highly versatile and has a wide range of adaptability. The flattening fine blanking process proposed in this application is not only suitable for the processing of a single type of parts, but can also be expanded to be applied to the manufacture of fine blanking parts made of multiple materials, multiple plate thicknesses and multiple complex structures.

[0110] The present embodiment also relates to a stamping die for a part with a partially variable cross-section, which is used to perform any of the above-mentioned stamping methods for a part with a partially variable cross-section, comprising an upper template 1, an upper backing plate 2, an upper fixing plate 3, a lower fixing plate 4, a lower backing plate 5, a lower template 6, a blank holder 7, a blank holder seat 8, a pre-cut punch 10, a pre-cut counter-pressure plate 9, a flattening punch 11, a die 16, a blanking punch and die 12, and a blanking counter-pressure plate 13;

[0111] The upper template 1, the upper pad 2, and the upper fixing plate 3 are arranged from top to bottom in the vertical direction;

[0112] The die 16, the lower fixing plate 4, the lower pad 5, and the lower template 6 are arranged from top to bottom in the vertical direction;

[0113] The blank holder seat 8 is sleeved on the outside of the blank holder 7 and connected to the blank holder 7. The pre-cut punch 10 is relatively arranged above the pre-cut back pressure plate 9. The bottom shape of the pre-cut punch 10 is a preset shape. The flattening punch 11 is arranged behind the pre-cut punch 10 and the pre-cut back pressure plate 9 in the production direction. The blanking convex and concave dies 12 and the blanking back pressure plate 13 are arranged behind the flattening punch 11 in the production direction. The blanking convex and concave dies 12 are relatively arranged above the blanking back pressure plate 13.

[0114] In this embodiment, the upper template 1, the upper pad 2, and the upper fixed plate 3 are in the upper half of the stamping die, the die 16, the lower fixed plate 4, the lower pad 5, and the lower template 6 are in the lower half of the stamping die, and the upper part of the upper template 1 and the lower part of the lower template 6 are transition plates. The upper and lower tables of the machine tool are equipped with oil cylinders that provide counter pressure and blank holding force, but their size is limited. If the mold is too large, the ejector rod will exceed the range of the oil cylinder. The transition plate is required, which is equivalent to slightly expanding the ejection surface of the oil cylinder that provides counter pressure and blank holding force. Its principle and structure are conventional technical means.

[0115] The blank holder 7, the blank holder seat 8, the pre-cut punch 10, the pre-cut counter-pressure plate 9, the flattening punch 11, the blanking punch and concave die 12 and the blanking counter-pressure plate 13 are between the upper fixed plate 3 and the lower fixed plate 4;

[0116] In this embodiment, a die 16 is also included, and the material strip 15 is located between the pressure ring 7 and the die 16; a pre-cut punch 10 and a pre-cut back pressure plate 9, a flattening punch 11, a blanking punch and a concave-convex die 12 and a blanking back pressure plate 13 are arranged in sequence along the production direction, and the pre-cut punch 10 and the pre-cut back pressure plate 9 pre-cut the material strip 15, cutting a cavity, that is, a through hole, on the material strip 15; the flattening punch 11 flattens the target area, and makes the material flow in the direction of the pre-cut; the pre-cut punch 10 and the pre-cut back pressure plate 9 realize fine blanking; its specific stamping structure and principle are conventional technical means, which will not be repeated here.

[0117] In this embodiment, the male and female dies refer to a die structure that has both male and female dies. The blanking die is a male and female die, and the pre-cut is only a male die.

[0118] The stamping die for locally variable cross-section parts of the present application realizes high-precision integrated forming of parts with flattening features. It introduces the flattening process requirements on the basis of the traditional fine stamping process, and realizes integrated high-precision forming of complex geometric shapes. The product contour is clear and the flattened area 17 has high flatness, which meets the technical requirements of high-end equipment manufacturing for precision special-shaped stamping parts. The flattening and fine stamping processes are integrated into a composite forming process, and a process combination method of first cutting, then flattening and finally blanking is adopted. The collaborative working mechanism of the pre-cut punch 10, the flattening punch 11, the blanking convex and concave die 12 and the fine stamping die is combined to realize the collaborative forming of the flattened structure and the fine stamping contour without adding additional processes, which greatly improves production efficiency, shortens processing time and reduces manufacturing costs.

[0119] According to some embodiments of the present application, optionally, the shape of the contact surface of the flattening punch 11 is a preset curved surface shape.

[0120] In this way, uniform pressure is applied to the variable cross-section area by the flattening punch 11 with a preset curved surface shape. The edge of the flattening punch 11 has corresponding chamfers and transitions to achieve a uniform transition and avoid defects such as tearing of the part material. The preset curved surface shape is designed according to the target part 18 so that the variable cross-section area on the part is uniformly transitioned to avoid sudden flattening of the part and defects such as material tearing.

[0121] According to some embodiments of the present application, optionally, Figure 9 As shown, the top of the blanking counter-pressure plate 13 is provided with a local protrusion 14 that matches the variable cross-section structure.

[0122] like Figure 10 As shown in the schematic diagram of the blanking step, Figure 10 For cross-sectional views at different angles, Figure 10 In the figure, there is a hole in the middle of the part, the punching hole is facing upward, and the target part 18 is punched out;

[0123] In this way, a local protrusion 14 back pressure plate is provided for the variable cross-section area to achieve uniform force in multiple areas. The shape of the local protrusion 14 is matched with the variable cross-section structure to support the flattened variable cross-section structure, so that the semi-processed parts can fit on the back pressure plate, and in the real-time blanking and punching process, the semi-processed parts can be stable and the punching force can be uniform.

[0124] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of the present invention. Therefore, based on the innovative concept of the present invention, changes and modifications to the embodiments described herein, or equivalent structural or equivalent process transformations made using the contents of the present invention's specification and drawings, and direct or indirect application of the above technical solutions to other related technical fields, are all included in the scope of patent protection of the present invention.

Claims

1. A method for stamping a part with a locally variable cross-section, characterized in that: The following steps are involved: S1, pre-incision; The blank holding force is provided by the blank holding ring push rod, the blank holding ring presses the material strip downward, the pre-cut punch moves downward under the action of the blanking force, and the pre-cut counter-pressure plate provides counter-pressure upward. At the same time, under the action of the pre-cut punch, the pre-cut counter-pressure plate moves downward, and the pre-cut punch and the pre-cut counter-pressure plate cooperate to cut a pre-cut of a preset shape on the material strip; S2, local flattening, based on the pre-cut, the target area is thinned and flattened to form a variable cross-section structure; The material strip moves downward along with the blank holder under the action of the blank holder force. The flattening punch cooperates with the blank holder to squeeze the target area of ​​the material strip to complete the flattening, so that the material in the flattening area is squeezed and flows toward the pre-cut direction. S3, blanking; The blanking force is provided by the blanking ring push rod, and the blanking ring presses the material strip downward. The blanking punch and die move downward under the action of the blanking force. The blanking counter-pressure plate provides counter-pressure upward. At the same time, under the action of the blanking punch and die, the blanking counter-pressure plate moves downward. The blanking punch and die and the blanking counter-pressure plate cooperate with each other to complete the blanking of the part's outer contour. For variable cross-section structures, the blanking counter-pressure plate is provided with a local protrusion that matches the variable cross-section structure.

2. The method for stamping a part with a partially variable cross-section according to claim 1, characterized in that: In S1 pre-cutting, the pre-cutting punch is a punch with a preset shape; The narrowest width of the punch of the preset shape is calculated based on the thickness of the material strip, the thickness of the material strip after flattening, the area of ​​the flattening area, and the outer contour of the flattening area. The narrowest width of the punch of the preset shape is greater than the distance required for the material to flow. By presetting the narrowest width of the punch shape, the distance required for material flow is calculated. The distance required for material flow and the thickness of the material strip after flattening are used to obtain the distance between the pre-cut contour and the outer contour of the finished part, which is applied to the pre-cut punch.

3. The method for stamping a part with a partially variable cross-section according to claim 2, wherein: The narrowest width x2 of the preset shape punch is calculated by the strip thickness, the strip thickness after flattening, the area of ​​the flattening area, and the outer contour of the flattening area. The calculation formula is: Where A is the area of ​​the flattened forming area, t1 is the thickness of the strip, t2 is the thickness of the strip after flattening, and l is the outer contour of the flattened area.

4. The method for stamping a part with a partially variable cross-section according to claim 3, characterized in that: The steps for calculating the distance required for material flow by using the narrowest width of the preset shape punch are as follows: during the flattening process, the flow distance is different for different shape contours, and the narrowest width of the preset shape punch is multiplied by the corresponding proportional coefficient to obtain the distance required for material flow.

5. The method for stamping a part with a partially variable cross-section according to claim 4, characterized in that: The distance x between the pre-cut profile and the outer contour of the finished part is obtained by the distance required for material flow and the thickness of the material strip after flattening. The calculation formula is: x=t2+2.5-x1 Where x1 is the distance required for the material to flow.

6. The method for stamping a part with a partially variable cross-section according to claim 1, characterized in that: In the S2 local flattening, based on the pre-cut, the target area is thinned and flattened to form a variable cross-section structure. When the flattening punch is a downward flattening punch, the material strip moves downward along with the blank holder under the action of the blank holder force, the flattening punch is fixed, and the blank holder continues to move downward to squeeze the material strip to complete the flattening; When the flattening punch is an upper flattening punch, the material strip moves downward along with the blank holder under the action of the blank holder force. After the material strip contacts the die, the blank holder force fixes the material strip. The flattening punch moves downward under the action of the blanking force, squeezes the material strip, and completes the flattening.

7. The method for stamping a part with a partially variable cross-section according to claim 6, wherein: In the local flattening S2, based on the pre-cut, the target area is subjected to thickness thinning and flattening treatment to form a variable cross-section structure. In the step, a flattening punch with a preset curved surface shape is used to apply uniform pressure to the variable cross-section area.

8. A stamping die for a part with a partially variable cross-section, characterized in that: Used to perform the stamping method of a part with a locally variable cross-section according to any one of claims 1 to 7, comprising an upper template, an upper pad, an upper fixing plate, a lower fixing plate, a lower pad, a lower template, a blank holder, a blank holder seat, a pre-cut punch, a pre-cut counter-pressure plate, a flattening punch, a die, a blanking punch and a blanking counter-pressure plate; The upper template, the upper pad, and the upper fixing plate are arranged from top to bottom in a vertical direction; The concave mold, the lower fixing plate, the lower pad, and the lower template are arranged from top to bottom in a vertical direction; The blank holder seat is sleeved on the outside of the blank holder ring and connected to the blank holder ring, the pre-cut punch is relatively arranged above the pre-cut back pressure plate, the bottom shape of the pre-cut punch is a preset shape, the flattening punch is arranged behind the pre-cut punch and the pre-cut back pressure plate in the production direction, the blanking convex and concave dies and the blanking back pressure plate are arranged behind the flattening punch in the production direction, and the blanking convex and concave dies are relatively arranged above the blanking back pressure plate.

9. The stamping die for partially variable cross-section parts according to claim 8, characterized in that: The shape of the contact surface of the flattening punch is a preset curved surface shape.

10. The stamping die for partially variable cross-section parts according to claim 9, characterized in that: The top of the blanking counter-pressure plate is provided with a local protrusion that matches the variable cross-section structure.

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