Continuous drawing die for convex hull forming, convex hull drawing forming method and convex hull sheet metal part

Abstract

The invention provides a continuous drawing die for convex hull forming, a convex hull drawing forming method and a convex hull sheet metal part. The continuous drawing die for convex hull forming comprises an upper die base, a lower die base and a drawing punch assembly. A material belt pushing area is arranged on the lower die holder; the stretching punch assembly is arranged in the material belt pushing area; the stretching punch assembly comprises an expanding punch, a retracting punch and a top stretching punch which are arranged at intervals, the diameter of the retracting punch is smaller than that of the expanding punch, and the height of the top stretching punch is larger than the height of the expanding punch and the height of the retracting punch at the same time; an expansion matching part, a contraction matching part and a top extension matching part are respectively arranged on the upper die holder; the expanding punch is opposite to the expanding matching part in position; the gathering and shrinking punch is opposite to the gathering and shrinking matching part in position; and the top stretching punch is opposite to the top stretching matching part in position, so that a pre-forming area of a metal plate material strip can be stretched by the expanding punch, the retracting punch and the top stretching punch in sequence in the pushing process, and a convex hull with a large depth is stretched out.

Description

Technical Field

[0001] The present disclosure relates to the technical field of stretching dies, and in particular to a continuous stretching die for convex hull forming, a convex hull stretching forming method, and a convex hull sheet metal part. Background Art

[0002] In the process of forming sheet metal parts, the ductility of the sheet metal parts is usually used for stretching, thereby forming depressions or protrusions of various shapes, which are collectively referred to as convex hulls in the industry. In order to improve the efficiency of convex hull forming, some manufacturers have made further research and development.

[0003] For example, Chinese patent document CN215965737U discloses a tool for forming a bulge on the surface of a sheet metal part, including a lower limit plate and an upper limit plate; a workpiece fixing mechanism for fixing the sheet metal part is arranged between the lower limit plate and the upper limit plate; a detachable connecting fixing mechanism is symmetrically arranged on both sides of the workpiece fixing mechanism between the lower limit plate and the upper limit plate; and a bulge forming mechanism is arranged on the upper limit plate and passes through the workpiece fixing mechanism.

[0004] However, the design of the above-mentioned sheet metal surface convex hull forming tooling has the following problems:

[0005] Although the above-mentioned sheet metal surface bulge forming tooling can quickly form a bulge, when it is necessary to stretch a bulge with a narrow bottom and a large depth on the sheet metal, for example, a bulge with a bottom diameter of 4mm to 5mm and a depth of 5mm to 6mm, the depth of the bulge to be stretched is large, resulting in uneven distribution of bulge thickness, which can easily be punctured by the punch during stretching, making it easy to make it difficult to stretch a bulge with a large depth. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a continuous stretching die for convex hull forming with a large convex hull stretching depth, a convex hull stretching forming method and a convex hull sheet metal part.

[0007] The purpose of this disclosure is achieved through the following technical solutions:

[0008] A continuous stretching die for convex hump forming, comprising an upper die seat and a lower die seat, wherein the lower die seat is provided with a material strip pushing area, and the material strip pushing area is used to place and push the sheet metal material strip; the upper die seat is lifted and arranged above the material strip pushing area;

[0009] The continuous stretching die for convex hull forming also includes a stretching punch assembly;

[0010] The stretching punch assembly is arranged in the pushing area of ​​the material strip; the stretching punch assembly includes an expansion punch, a contraction punch and a top extension punch which are arranged in sequence and at intervals along the pushing direction of the sheet metal material strip, the diameter of the contraction punch is smaller than the diameter of the expansion punch, and the height of the top extension punch is simultaneously greater than the height of the expansion punch and the height of the contraction punch; an expansion fitting part, a contraction fitting part and a top extension fitting part are respectively arranged on the upper die seat; the expansion punch is opposite to the expansion fitting part and forms an expansion forming station; the contraction punch is opposite to the contraction fitting part and forms a contraction forming station; the top extension punch is opposite to the top extension fitting part and forms a top extension forming station; the expansion forming station, the contraction forming station and the top extension forming station are used to sequentially stretch the pre-forming area of ​​the sheet metal material strip to form a convex hump.

[0011] In one embodiment, the end of the expansion punch, the end of the contraction punch and the end of the extension punch are all spherical cap-shaped.

[0012] In one embodiment, the end curvature of the expansion punch, the end curvature of the contraction punch, and the end curvature of the extension punch increase sequentially.

[0013] In one of the embodiments, the stretching punch assembly also includes a flattening punch; in the pushing direction along the sheet metal strip, the flattening punch is located on the side of the extension punch away from the retraction punch; the upper die seat is also provided with a flattening matching portion; the flattening punch is positioned opposite to the flattening matching portion and forms a flattening forming station.

[0014] In one embodiment, the end of the flattening punch is in a frustoconical shape.

[0015] In one of the embodiments, a punching head and a positioning pin are provided at intervals on the lower die base; the punching head and the positioning pin are arranged in sequence along the pushing direction of the sheet metal strip and face the strip pushing area; along the pushing direction of the sheet metal strip, the positioning pin is located on the side of the expansion fitting portion away from the contraction fitting portion.

[0016] In one of the embodiments, the continuous stretching die for bulge forming also includes a slitting punch; the slitting punch is arranged on the upper die base; in the pushing direction along the sheet metal strip, the slitting punch is located on the side of the extending fitting part away from the shrinking fitting part, and the slitting punch is used to punch the part between the two groups of bulges.

[0017] In one of the embodiments, the continuous stretching die for bulge forming also includes a sheet edge bending assembly, which is arranged on the lower die base; in the pushing direction along the sheet metal strip, the sheet edge bending assembly is located on the side of the slitting punch away from the top extension mating portion.

[0018] A convex hull stretching method, performed using the continuous stretching die for convex hull forming described in any of the above embodiments;

[0019] The convex hull stretching forming method comprises the following steps:

[0020] Obtaining a sheet metal strip, and placing the sheet metal strip in the strip pushing area;

[0021] Pushing the pre-formed area of ​​the sheet metal strip to the expansion forming station so that the expansion punch stretches a bulge on the sheet metal strip;

[0022] Pushing the bulge to the shrinking and forming station so that the shrinking and fitting part squeezes and shrinks the stretch amount of the bulge periphery;

[0023] The bulge is pushed to the top stretching forming station so that the top stretching punch stretches the top of the bulge to obtain a convex bulge.

[0024] A convex sheet metal part is manufactured by the convex stretching forming method of the above embodiment.

[0025] Compared with the prior art, the present invention has at least the following advantages:

[0026] 1) Since the expansion punch, the contraction punch and the top extension punch are arranged in sequence and at intervals in the material strip pushing area along the pushing direction of the sheet metal strip, and the upper die seat is provided with an expansion fitting portion arranged opposite to the expansion punch, a contraction fitting portion arranged opposite to the contraction punch, and the top extension fitting portion arranged opposite to the position of the top extension punch, and since the upper die seat is raised and lowered above the material strip pushing area, the diameter of the contraction punch is smaller than the diameter of the expansion punch, when the sheet metal strip is placed on the material strip pushing area, the expansion forming station can stretch and expand the pre-forming area of ​​the sheet metal strip and push it forward along with the sheet metal strip. Because the height of the extending punch is greater than the height of the expanding punch and the height of the contracting punch, the pre-forming area of ​​the sheet metal strip will be gathered by the contraction forming station and further stretched by the extending station in turn, and finally a convex bulge with a greater stretching depth will be formed on the pre-forming area of ​​the sheet metal strip.

[0027] 2) Compared with the sheet metal surface bulge forming tooling in the prior art, when the pre-forming area of ​​the sheet metal strip is pushed to the expansion forming station, the pre-forming area of ​​the sheet metal strip will be stretched and enlarged by the expansion punch to form a bulge; when the bulge is pushed to the contraction forming station, since the diameter of the contraction punch is smaller than the diameter of the expansion punch, the stretching amount of the periphery of the bulge will be squeezed toward the top of the bulge by the contraction fitting part, so that the periphery of the bulge shrinks, that is, the bottom diameter of the bulge shrinks within the range of 4mm to 5mm, and the thickness of the periphery of the bulge can be made consistent. At the same time, as the stretching amount of the bulge periphery gathers toward the top of the bulge, the material thickness of the bulge top will increase, so that the bulge top has stronger ductility; afterwards, the bulge is pushed to the top stretching forming station. Since the height of the top stretching punch is greater than the height of the expansion punch and the height of the contraction punch, the thickness of the bulge top will be reduced and tend to be consistent with the thickness of the bulge periphery after further stretching by the top stretching punch, and finally a bulge with a depth of 5mm to 6mm is formed. The above-mentioned bulge thickness is more evenly distributed as a whole, and it is less likely to be punctured by the punch during stretching. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 is a cross-sectional view of a continuous stretching die according to an embodiment of the present disclosure;

[0030] Figure 2 for Figure 1 A partial enlarged view shown in the middle A;

[0031] Figure 3 for Figure 1 A schematic structural diagram of a sheet metal strip stretched by a continuous stretching die shown;

[0032] Figure 4 for Figure 1 A partial enlarged view shown at B in the middle;

[0033] Figure 5 A flow chart of a convex hull stretching method according to another embodiment of the present disclosure;

[0034] Figure 6 A partial cross-sectional view of a continuous stretching die according to another embodiment of the present disclosure;

[0035] Figure 7 for Figure 1 A physical picture of the continuous stretching die shown;

[0036] Figure 8 for Figure 3 A physical picture of the stretched sheet metal strip of the continuous stretching die shown.

[0037] Reference numerals: 100, continuous stretching die; 110, upper die seat; 1110, expansion fitting portion; 1120, contraction fitting portion; 1130, extension fitting portion; 1140, leveling fitting portion; 1150, pre-folding die; 1160, bending die; 120, lower die seat; 1210, material strip pushing area; 1221, punching head; 1222, positioning pin; 1223, slitting punch; 1230, sheet metal edge bending assembly; 1231, pre-folding punch; 1232, bending punch; 130, stretching punch assembly; 1310, expansion punch Head; 1320, retraction punch; 1330, extension punch; 1340, leveling punch; 200, sheet metal strip; 21a, new bulge; 21b, old bulge; 220, convex bump; 230, positioning hole; 240, convex sheet metal part; 24a, hollow area; 24b, gap; 2510, first stripping block; 2511, first buffer gasket; 2520, first expansion slot; 2530, first air duct; 2610, second stripping block; 2611, second buffer gasket; 2620, second expansion slot; 2630, second air duct. DETAILED DESCRIPTION

[0038] In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present disclosure are given in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thoroughly and comprehensively understood.

[0039] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present disclosure. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0041] In order to better understand the technical solutions and beneficial effects of the present invention, the present invention is further described in detail below in conjunction with specific embodiments:

[0042] like Figure 1 and Figure 2 As shown, a continuous stretching die 100 for convex hump forming in one embodiment comprises an upper die seat 110, a lower die seat 120 and a stretching punch assembly 130; a material strip pushing area 1210 is provided on the lower die seat 120, and the material strip pushing area 1210 is used to place and push the sheet metal material strip 200; the upper die seat 110 is lifted and arranged above the material strip pushing area 1210; the stretching punch assembly 130 is arranged in the material strip pushing area 1210; the stretching punch assembly 130 comprises an expansion punch 1310, a contraction punch 1320 and an extension punch 1330 which are sequentially arranged at intervals along the pushing direction of the sheet metal material strip 200, the diameter of the contraction punch 1320 is smaller than the diameter of the expansion punch 1310, and the extension punch 1330 is The height of 330 is greater than the height of the expansion punch 1310 and the height of the contraction punch 1320; the expansion fitting part 1110, the contraction fitting part 1120 and the extension fitting part 1130 are respectively arranged on the upper die base 110; the expansion punch 1310 is opposite to the expansion fitting part 1110, and forms an expansion forming station; the contraction punch 1320 is opposite to the contraction fitting part 1120, and forms a contraction forming station; the extension punch 1330 is opposite to the extension fitting part 1130, and forms an extension forming station; the expansion forming station, the contraction forming station and the extension forming station are used to sequentially stretch the pre-forming area of ​​the sheet metal strip 200 to form a bulge 220.

[0043] It can be understood that since the expansion punch 1310, the contraction punch 1320 and the extension punch 1330 are arranged in sequence and at intervals in the material strip pushing area 1210 along the pushing direction of the sheet metal strip 200, and the upper die base 110 is provided with an expansion matching portion 1110 arranged opposite to the expansion punch 1310, a contraction matching portion 1120 arranged opposite to the contraction punch 1320, and the extension matching portion 1130 positioned opposite to the extension punch 1330, and because the upper die base 110 is raised and lowered above the material strip pushing area 1210, the diameter of the contraction punch 1320 is smaller than the diameter of the expansion punch 1310, when the sheet metal strip 200 is placed on the material strip pushing area 1210, the expansion forming station can stretch and expand the pre-forming area of ​​the sheet metal strip 200 and push it forward along with the sheet metal strip 200. Because the height of the extending punch 1330 is greater than the height of the expansion punch 1310 and the height of the contraction punch 1320, the pre-forming area of ​​the sheet metal strip 200 will be gathered by the contraction forming station and further stretched by the extending station in turn, and finally a bulge 220 with a greater stretching depth will be formed on the pre-forming area of ​​the sheet metal strip 200.

[0044] It can be understood that compared with the sheet metal surface bulge 220 forming tooling in the prior art, when the pre-forming area of ​​the sheet metal strip 200 is pushed to the expansion forming station, the pre-forming area of ​​the sheet metal strip 200 will be stretched and enlarged by the expansion punch 1310, thereby forming a bulge 210; when the bulge 210 is pushed to the shrinking forming station, since the diameter of the shrinking punch 1320 is smaller than the diameter of the expansion punch 1310, the stretching amount of the periphery of the bulge 210 will be squeezed toward the top of the bulge 210 by the shrinking fitting part 1120, so that the periphery of the bulge 210 shrinks, that is, the bottom diameter of the bulge 210 shrinks within the range of 4mm to 5mm, and the periphery thickness of the bulge 210 can be made consistent. At the same time, as the stretching amount of the periphery of the bulge 210 gathers toward the top of the bulge 210, the material thickness of the top of the bulge 210 will increase, so that the top of the bulge 210 has stronger ductility; afterwards, the bulge 210 is pushed to the top extension forming station. Since the height of the top extension punch 1330 is greater than the height of the expansion punch 1310 and the height of the contraction punch 1320, the top of the bulge 210 will be further stretched by the top extension punch 1330. The thickness of the top of the bulge 210 will be reduced and tend to be consistent with the thickness of the periphery of the bulge 210, and finally a convex bulge 220 with a depth of 5mm to 6mm is formed. The thickness of the above-mentioned convex bulge 220 is more evenly distributed as a whole, and it is less likely to be punctured by the punch during stretching.

[0045] Combination Figure 2 As shown, in one embodiment, the end of the expansion punch 1310, the end of the contraction punch 1320, and the end of the top extension punch 1330 are all in a spherical crown shape. It can be understood that because the end of the expansion punch 1310, the end of the contraction punch 1320, and the end of the top extension punch 1330 are all in a spherical crown shape, when the end of the expansion punch 1310, the end of the contraction punch 1320, and the end of the top extension punch 1330 contact the pre-formed area of ​​the sheet metal strip 200, the contact surface therebetween is a spherical crown surface, and the force of the pre-formed area of ​​the sheet metal strip 200 can be dispersed along the spherical crown surface, thereby preventing the sheet metal strip 200 from being pulled apart due to excessive pressure on a part of the sheet metal strip 200.

[0046] Combination Figure 2 As shown, in one embodiment, the end curvature of the expansion punch 1310, the end curvature of the contraction punch 1320, and the end curvature of the top extension punch 1330 increase in sequence. It can be understood that because the end curvature of the expansion punch 1310, the end curvature of the contraction punch 1320, and the end curvature of the top extension punch 1330 increase in sequence, the end of the expansion punch 1310, the end of the contraction punch 1320, and the end of the top extension punch 1330 gradually become smooth, so that the end of the expansion punch 1310, the end of the contraction punch 1320, and the end of the top extension punch 1330 successively smoothly stamp the preformed area on the sheet metal strip 200, and finally extend and stretch the convex 220.

[0047] Combination Figure 2 As shown, in one embodiment, the end diameter of the expansion punch 1310, the end diameter of the contraction punch 1320, and the end diameter of the top extension punch 1330 are reduced in sequence. It can be understood that because the end diameters of the expansion punch 1310, the end diameters of the contraction punch 1320, and the end diameters of the top extension punch 1330 are reduced in sequence, after the preformed area on the sheet metal strip 200 is stamped by the expansion punch 1310, the contraction punch 1320, and the top extension punch 1330 in sequence, the top of the bulge 210 can be gradually stamped and stretched to form the convex bulge 220.

[0048] Combination Figure 2As shown, in one embodiment, the stretching punch assembly 130 also includes a flattening punch 1340; in the pushing direction along the sheet metal strip 200, the flattening punch 1340 is located on the side of the extension punch 1330 away from the retraction punch 1320; the upper die base 110 is also provided with a flattening mating portion 1140; the flattening punch 1340 is positioned opposite to the flattening mating portion 1140, and forms a flattening and forming station. It can be understood that because the end of the bulge 220 is relatively smooth and prone to rebound, the end of the bulge 220 is very easy to deform during subsequent processing. By setting the flattening punch 1340 on the side of the top extension punch 1330 away from the retraction punch 1320, the flattening punch 1340 and the leveling mating part 1140 are relatively positioned to form a flattening and forming station. When the bulge 220 is pushed to the flattening and forming station, the top of the bulge 220 will be squeezed flat by the flattening punch 1340, which can effectively reduce the rebound phenomenon of the bulge 220, thereby being more conducive to subsequent processing.

[0049] Combination Figure 2 As shown, in one embodiment, the end of the flattening punch 1340 is in a truncated cone shape. It can be understood that, since the end of the flattening punch 1340 is in a truncated cone shape, when the flattening punch 1340 lifts the top of the convex hump 220, the flattening punch 1340 can cooperate with the flattening matching portion 1140 to squeeze the convex hump 220, so that the convex hump 220 finally presents a truncated cone shape, and the truncated cone shape has higher structural stability, which is more convenient for subsequent processing.

[0050] Combination Figure 1 As shown, in one of the embodiments, a punching head 1221 and a positioning pin 1222 are provided at intervals on the lower die base 120; the punching head 1221 and the positioning pin 1222 are arranged in sequence along the pushing direction of the sheet metal strip 200 and face the strip pushing area 1210; along the pushing direction of the sheet metal strip 200, the positioning pin 1222 is located on the side of the expansion fitting portion 1110 away from the contraction fitting portion 1120. It can be understood that since the punching head 1221 and the positioning pin 1222 are arranged in sequence along the pushing direction of the sheet metal strip 200, the positioning pin 1222 is located on the side of the expansion fitting portion 1110 away from the contraction fitting portion 1120. Before the sheet metal strip 200 enters the expansion forming station, the sheet metal strip 200 will be punched with positioning holes 230 in sequence by the punching head 1221. At the same time, as the sheet metal strip 200 is pushed forward, the positioning pin 1222 can be inserted into the corresponding positioning hole 230 in sequence, so that the sheet metal strip 200 is positioned by the positioning pin 1222, thereby avoiding the displacement of the sheet metal strip 200 during the stretching process of subsequent stations.

[0051] Combination Figure 1 and Figure 3 As shown, in one embodiment, the continuous stretching die 100 for convex bulge forming further includes a slitting punch 1223; the slitting punch 1223 is arranged on the upper die seat 110; in the pushing direction along the sheet metal strip 200, the slitting punch 1223 is located on the side of the top extension fitting portion 1130 away from the shrinking fitting portion 1120, and the slitting punch 1223 is used to punch out the portion between the two groups of convex bulges 220. It can be understood that since the slitting punch 1223 is arranged on the side of the top extension fitting portion 1130 away from the shrinking fitting portion 1120, the portion between the two groups of convex bulges 220 on the sheet metal strip 200 can be punched out by the slitting punch 1223 and a hollow area 24a can be formed, so that it is more convenient to separate each group of convex bulges 220 to obtain a convex bulge sheet metal part 240 later.

[0052] Combination Figure 1 and Figure 4 As shown, in one embodiment, the continuous stretching die 100 for convex hull forming further includes a sheet edge bending assembly 1230, which is arranged on the lower die seat 120; in the pushing direction along the sheet metal strip 200, the sheet edge bending assembly 1230 is located on the side of the slitting punch 1223 away from the top extension matching portion 1130. It can be understood that by arranging the sheet edge bending assembly 1230 on the side of the slitting punch 1223 away from the top extension matching portion 1130, the edge of the hollow area 24a punched out by the slitting punch 1223 can be bent by the sheet edge bending assembly 1230, which not only makes it easier to adapt and install the convex hull sheet metal part 240, but also prevents workers from being scratched when taking and placing the convex hull sheet metal part 240.

[0053] Combination Figure 4As shown, in one embodiment, the sheet metal edge bending assembly 1230 includes a pre-folding punch 1231 and a bending punch 1232 which are arranged in sequence and at intervals along the pushing direction of the sheet metal strip 200; a pre-folding die 1150 and a bending die 1160 are respectively arranged on the upper die base 110; the pre-folding punch 1231 is positioned opposite to the pre-folding die 1150 and forms a pre-folding station; the bending punch 1232 is positioned opposite to the bending die 1160 and forms a bending station. It can be understood that since the pre-folding punch 1231 and the pre-folding die 1150 are positioned relative to each other to form a pre-folding station, the bending punch 1232 and the bending die 1160 are positioned relative to each other to form a bending station, and the pre-folding punch 1231 and the bending punch 1232 are arranged in sequence along the pushing direction of the sheet metal strip 200, when the sheet edge bending assembly 1230 processes the sheet metal strip 200, the edge of the hollow area 24a of the sheet metal strip 200 will first be stamped by the pre-folding punch 1231 and bent downward; thereafter, the edge of the hollow area 24a of the sheet metal strip 200 will be stamped by the bending punch 1232 to form a bend. Bending the edge of the hollow area 24a of the sheet metal strip 200 by two-step stamping can make the bending transition smoother, and can be more convenient for subsequent picking and assembly.

[0054] Combination Figure 1 and Figure 7 As shown, the present disclosure also provides a stretching forming device, including the continuous stretching die 100 for convex bulge forming of any of the above embodiments. It can be understood that by applying the continuous stretching die 100 for convex bulge forming of the present disclosure in the stretching forming device, when the pre-forming area of ​​the sheet metal strip 200 is pushed to the expansion forming station, the pre-forming area of ​​the sheet metal strip 200 will be stretched and enlarged by the expansion punch 1310, thereby forming a bulge 210; when the bulge 210 is pushed to the shrinking forming station, the stretching amount of the periphery of the bulge 210 will be squeezed by the shrinking fitting part 1120 to gather toward the top of the bulge 210, so that the periphery of the bulge 210 shrinks, that is, the bottom diameter of the bulge 210 shrinks within the range of 4mm to 5mm, and the periphery thickness of the bulge 210 can be made consistent. At the same time, as the stretching amount of the periphery of the bulge 210 gathers toward the top of the bulge 210, the material thickness of the top of the bulge 210 will increase, so that the top of the bulge 210 has stronger ductility; after that, the bulge 210 is pushed to the top stretching forming station, and the top of the bulge 210 is further stretched by the top stretching punch 1330, and the thickness of the top of the bulge 210 will be reduced and tend to be consistent with the thickness of the periphery of the bulge 210, and finally a convex bulge 220 with a depth of 5mm to 6mm is formed. The thickness of the above-mentioned convex bulge 220 is more evenly distributed as a whole, and it is less likely to be punctured by the punch during stretching.

[0055] Combination Figure 3 and Figure 5 As shown, the present disclosure also provides a method for stretching and forming a convex hull 220, which is performed by using the continuous stretching die 100 for convex hull forming of any of the above embodiments;

[0056] The stretching method of the convex hump 220 comprises the following steps:

[0057] S100 , obtaining a sheet metal strip 200 , and placing the sheet metal strip 200 in the strip pushing area 1210 .

[0058] In this embodiment, the sheet metal strip 200 is a strip-shaped metal sheet with a thickness of less than 6 mm, which can be rolled into a coil for easier storage and use. By placing the sheet metal strip 200 in the strip pushing area 1210, the sheet metal strip 200 can be pushed forward in an orderly manner along the strip pushing area 1210.

[0059] S200 , pushing the pre-forming area of ​​the sheet metal strip 200 to the expansion forming station, so that the expansion punch 1310 stretches a bulge 210 on the sheet metal strip 200 .

[0060] In this embodiment, by pushing the preforming area of ​​the sheet metal strip 200 to the expansion forming station, the expansion punch 1310 can move toward the preforming area of ​​the sheet metal strip 200 to stretch and expand the preforming area of ​​the sheet metal strip 200, thereby forming the bulge 210 in the preforming area of ​​the sheet metal strip 200.

[0061] S300 , pushing the bulge 210 to the shrinkage molding station so that the shrinkage fitting portion 1120 squeezes and shrinks the stretch amount of the periphery of the bulge 210 .

[0062] In this embodiment, by pushing the bulge 210 to the shrinking molding station, the shrinking matching part 1120 squeezes and shrinks the stretch amount of the bulge 210 periphery, so that the stretch amount of the bulge 210 periphery is gathered toward the top of the bulge 210, and then the periphery of the bulge 210 is shrunk, that is, the bottom diameter of the bulge 210 is shrunk within the range of 4mm to 5mm, and the thickness of the bulge 210 periphery is made uniform. At the same time, as the stretch amount of the bulge 210 periphery is gathered toward the top of the bulge 210, the material thickness of the top of the bulge 210 is increased, so that the top of the bulge 210 has stronger ductility.

[0063] S400 , pushing the bulge 210 to the jacking forming station so that the jacking punch 1330 stretches the top of the bulge 210 to obtain a convex bump 220 .

[0064] In this embodiment, by pushing the bulge 210 to the top stretching forming station, the top stretching punch 1330 stretches the top of the bulge 210, and the thickness of the top of the bulge 210 will be reduced and tend to be consistent with the thickness of the periphery of the bulge 210, eventually forming a bulge 220 with a depth of 5mm to 6mm.

[0065] It can be understood that when the sheet metal strip 200 is placed on the strip pushing area 1210, the expansion forming station can stretch and expand the pre-forming area of ​​the sheet metal strip 200, and as the sheet metal strip 200 is pushed forward, the pre-forming area of ​​the sheet metal strip 200 will be gathered by the shrinking forming station and further stretched by the jacking station in turn, and finally a convex bulge 220 with a larger stretching depth can be formed on the pre-forming area of ​​the sheet metal strip 200. The overall thickness distribution of the convex bulge 220 is more uniform, and it is less likely to be punctured by a punch during stretching.

[0066] However, when the sheet metal strip 200 is a stainless steel strip, since the stainless steel strip has poorer ductility than metal strips such as copper strips and aluminum strips, when the expansion punch 1310 stretches the pre-forming area of ​​the sheet metal strip 200, a large tensile force will be generated between the pre-forming area and the surrounding strip area. The tensile force will hinder the stamping process of the expansion punch 1310, and will eventually cause the bulge 210 to form slowly.

[0067] Combination Figure 1 , Figure 3 and Figure 8 As shown, in order to reduce the magnitude of the tensile force, thereby forming the bulge 210 on the stainless steel strip more quickly, in one embodiment, step S200, pushing the pre-forming area of ​​the sheet metal strip 200 to the expansion forming station, so that the expansion punch 1310 stretches the bulge 210 on the sheet metal strip 200, also includes:

[0068] Step A: punching the positions of the two end edges of the pre-forming area so that gaps 24b are formed between the two end edges of the pre-forming area and the surrounding material strip area.

[0069] It can be understood that by punching the positions of the two end edges of the preforming area, gaps 24b are formed between the two end edges of the preforming area and the surrounding material strip area, that is, the two end edges of the preforming area are separated from the surrounding material strip area. When the expansion punch 1310 is stretching the preforming area of ​​the sheet metal strip 200, since the two end edges of the preforming area are separated from the surrounding material strip area, the tensile force between the preforming area and the surrounding material strip area is reduced, that is, the resistance of the tensile force to the expansion punch 1310 is reduced, and finally the efficiency of the forming of the bulge 210 is accelerated.

[0070] Usually, after the edges at both ends of the preforming area are separated from the surrounding material strip areas respectively, that is, the two ends of the preforming area are in an active state, if the action distance of the expansion punch 1310 is too close to the end of the preforming area, it is easy to cause the end of the preforming area to be lifted due to the stretching action of the expansion punch 1310, thereby failing to achieve the effect of forming the bulge 210; if the action distance of the expansion punch 1310 is too far from the end of the preforming area, that is, the forming position of the bulge 210 is close to the center of the preforming area, the tensile force of the bulge 210 during the forming process will increase, thereby affecting the forming efficiency of the bulge 210.

[0071] In order to make the expansion punch 1310 act accurately on the predetermined position of the pre-forming area, and improve the forming effect of the bulge 210 while reducing the tensile force, in one embodiment, step S200, pushing the pre-forming area of ​​the sheet metal strip 200 to the expansion forming station so that the expansion punch 1310 stretches the bulge 210 on the sheet metal strip 200, specifically includes the following steps:

[0072] S210, pushing the sheet metal strip 200 forward along the strip pushing area 1210;

[0073] S220, when the preforming area of ​​the sheet metal strip 200 is located at the expansion forming station, respectively obtaining the two gap patterns;

[0074] S230, obtaining the horizontal coordinate of the center of the preforming area according to the two gap graphics;

[0075] S240, calculating the difference between the central horizontal coordinate of the preforming area and the horizontal coordinate of the projection of the expansion punch 1310, so as to obtain the horizontal distance difference of the bulge 210; wherein the horizontal coordinate of the projection of the expansion punch 1310 is the horizontal coordinate of the projection position of the end of the expansion punch 1310 on the preforming area of ​​the sheet metal strip 200;

[0076] S250, detecting whether the lateral distance difference of the bulge 210 is greater than a preset lateral distance difference;

[0077] S260, when the lateral forming distance difference of the bulge 210 is greater than the preset lateral forming distance difference, the sheet metal strip 200 is pushed in the reverse direction along the strip pushing area 1210 to reduce the distance between the expansion punch 1310 and the center position of the preforming area of ​​the sheet metal strip 200;

[0078] S270, pushing the expansion punch 1310 to move toward the forming area of ​​the sheet metal strip 200 to stretch out the bulge 210.

[0079] In this embodiment, the gap pattern is a pattern of a gap 24b formed between the end edge of the preforming area and the surrounding material strip area. By respectively obtaining two of the gap patterns, the center position of the preforming area can be obtained through the positions of the two gap patterns, that is, the horizontal coordinate of the center of the preforming area can be obtained. Because the lateral distance difference of the bulge 210 is obtained based on the difference between the horizontal coordinate of the center of the preforming area and the horizontal coordinate of the projection of the expansion punch 1310, the deviation of the expansion punch 1310 from the center of the preforming area can be reflected by the lateral distance difference of the bulge 210. Because the preset lateral distance difference is the difference between the horizontal coordinate of the projection position of the end of the expansion punch 1310 on the preforming area of ​​the sheet metal strip 200 and the horizontal coordinate of the center of the preforming area when the expansion punch 1310 can just form the bulge 210 in the preforming area without warping, the distance between the expansion punch 1310 and the center of the preforming area can be detected by comparing the size of the lateral distance difference of the bulge 210 and the preset lateral distance difference. Among them, the direction of the sheet metal strip 200 moving forward along the strip push zone 1210 is the direction from the expansion forming station to the contraction forming station.

[0080] Specifically, when the lateral forming distance difference of the bulge 210 is greater than the preset lateral forming distance difference, it means that the distance between the expansion punch 1310 and the center position of the pre-forming area of ​​the sheet metal strip 200 is too large, that is, the expansion punch 1310 is too close to the gap 24b. At this time, if the expansion punch 1310 stretches the pre-forming area, it is easy to cause the end of the pre-forming area to warp due to the stretching action of the expansion punch 1310. By pushing the sheet metal strip 200 to move in the opposite direction along the strip pushing area 1210, the distance between the expansion punch 1310 and the center position of the pre-forming area of ​​the sheet metal strip 200 can be reduced, that is, the distance between the expansion punch 1310 and the gap 24b is increased, thereby reducing the occurrence of the end of the pre-forming area warping due to the stretching action of the expansion punch 1310.

[0081] In another embodiment, step S250, detecting whether the lateral distance difference of the bulge 210 is greater than a preset lateral distance difference, further includes the following steps:

[0082] Step B: When the lateral distance difference of the bulge 210 is smaller than the preset lateral distance difference, the sheet metal strip 200 is pushed forward along the strip pushing area 1210 to increase the distance between the expansion punch 1310 and the center position of the pre-forming area of ​​the sheet metal strip 200.

[0083] In this embodiment, when the lateral distance difference of the bulge 210 is less than the preset lateral distance difference, it means that the distance between the expansion punch 1310 and the center position of the pre-forming area of ​​the sheet metal strip 200 is too small, that is, the distance between the expansion punch 1310 and the gap 24b is too large. At this time, if the expansion punch 1310 stretches the pre-forming area, the position where the expansion punch 1310 is stretched will be pulled by the surrounding material strips, resulting in a slowdown in the efficiency of the bulge 210 forming. By pushing the sheet metal strip 200, the expansion punch 1310 is pushed out of the pre-forming area. 00 continues to move along the material strip pushing area 1210, which can increase the distance between the expansion punch 1310 and the center position of the pre-forming area of ​​the sheet metal material strip 200, that is, reduce the distance between the expansion punch 1310 and the gap 24b. The position where the expansion punch 1310 is stretched by the gap 24b will be pulled by the surrounding material strip, thereby reducing the tensile force between the position where the expansion punch 1310 is stretched and the surrounding material strip, further improving the forming efficiency of the bulge 210.

[0084] In another embodiment, step S250, detecting whether the lateral distance difference of the bulge 210 is greater than a preset lateral distance difference, further includes the following steps:

[0085] Step C: When the lateral distance difference of the bulge 210 is equal to the preset lateral distance difference, execute step S270.

[0086] In this embodiment, when the lateral distance difference of the bulge 210 is equal to the preset lateral distance difference, the projected position of the end of the expansion punch 1310 on the pre-forming area of ​​the sheet metal strip 200 is just located at the predetermined pull rope position, and the expansion punch 1310 can just form the bulge 210 in the pre-forming area without warping.

[0087] Combination Figure 6 and Figure 7As shown, usually, when the upper die base 110 moves downward and closes the mold with the lower die base 120, the sheet metal strip 200 will be affected by the expansion punch 1310 and the contraction punch 1320 at the same time, that is, the expansion punch 1310 will stretch the sheet metal strip 200 to form a new bulge 21a, and the contraction punch 1320 will further stretch the sheet metal strip 200 to form an old bulge 21b. When the stretching force is too large, the new bulge 21a and the expansion fitting part 1110, and the old bulge 21b and the contraction fitting part 1120 are easily embedded in each other, so that the sheet metal strip 200 is stuck on the upper die base 110 after the mold is opened, which ultimately affects the continuous pushing of the sheet metal strip 200.

[0088] In order to solve the above problem, in one embodiment, please refer to Figure 6 A first stripping block 2510 is provided between the expansion fitting portion 1110 and the contraction fitting portion 1120; a first telescopic groove 2520 is opened on the upper mold base 110, and the first stripping block 2510 is slidably set in the first telescopic groove 2520 and elastically connected to the bottom of the first telescopic groove 2520. It can be understood that since the first stripping block 2510 is slidably arranged in the first telescopic groove 2520, when the upper mold base 110 and the lower mold base 120 are molded, the first stripping block 2510 will be pressed on the sheet metal strip 200, thereby sliding to the bottom of the first telescopic groove 2520, so that an elastic force is formed between the first stripping block 2510 and the bottom of the first telescopic groove 2520. When the upper mold base 110 and the lower mold base 120 are opened, the first stripping block 2510 can push the sheet metal strip 200 to fall off the upper mold base 110 under the action of the elastic force, thereby reducing the occurrence of the sheet metal strip 200 being stuck on the upper mold base 110 and improving the pushing efficiency of the sheet metal strip 200.

[0089] Usually, after the upper mold base 110 and the lower mold base 120 are opened, the elastic force between the first stripping block 2510 and the bottom of the first telescopic groove 2520 will be released instantly. When the impact force of the first stripping block 2510 on the sheet metal strip 200 is too large, it is easy to punch out dents on the sheet metal strip 200. The dents will reduce the surface flatness of the sheet metal strip 200 and reduce the consistency and aesthetics of the subsequently formed bulge 220.

[0090] Combination Figure 6As shown, in order to solve the above problem, in one embodiment, the first stripping block 2510 is provided with a first buffer pad 2511 on the side facing the lower die base 120. It can be understood that since the first buffer pad 2511 is provided on the side of the first stripping block 2510 facing the lower die base 120, when the upper die base 110 and the lower die base 120 are opened, the first stripping block 2510 acts on the sheet metal strip 200 through the first buffer pad 2511, thereby buffering the impact force of the first stripping block 2510 on the sheet metal strip 200, thereby reducing the occurrence of dents on the sheet metal strip 200. In another embodiment, the first buffer pad 2511 is an air cushion, and the air cushion is provided with an exhaust hole on the side facing the lower die base 120. When the first buffer pad 2511 contacts the sheet metal strip 200, the gas in the air cushion is discharged from the exhaust hole, further assisting in pushing the sheet metal strip 200 to fall off. When the first buffer pad 2511 is not under pressure, the gas will not be discharged from the exhaust hole. Specifically, a one-way exhaust valve is provided at the exhaust hole.

[0091] Combination Figure 6 As shown, in one embodiment, in order to improve the stripping efficiency of the sheet metal strip 200 and the upper die seat 110, a first air channel 2530 is provided on the upper die seat 110, and the first air channel 2530 is provided between the expansion fitting portion 1110 and the shrinking fitting portion 1120, and the outlet end of the first air channel 2530 faces the lower die seat 120. It can be understood that by providing the first air channel 2530 on the upper die seat 110, because the outlet end of the first air channel 2530 faces the lower die seat 120, when the upper die seat 110 and the lower die seat 120 are opened, gas can be introduced into the first air channel 2530, so that the gas can be discharged through the outlet end of the first air channel 2530 and blown to the position of the sheet metal strip 200 located between the expansion fitting portion 1110 and the shrinking fitting portion 1120, so that the sheet metal strip 200 can be blown off from the upper die seat 110 quickly.

[0092] Usually, after the gas is discharged from the outlet end of the first air duct 2530, the gas will disperse and flow toward the new bulge 21a and the old bulge 21b respectively. Since the old bulge 21b is formed after the new bulge 21a shrinks, the bottom diameter of the new bulge 21a is larger than the bottom diameter of the old bulge 21b, that is, the contact area between the new bulge 21a and the gas is larger than the contact area between the old bulge 21b and the wind. Under the action of the same compressed gas, the new bulge 21a is subjected to a greater thrust, that is, the sheet metal strip 200 is easily offset backward under the action of the gas, which can easily lead to deviation in the stretching position of the next stretching process, affecting the normal forming process of the sheet metal strip 200.

[0093] To solve the above problem, in one embodiment, the distance between the outlet end of the first air channel 2530 and the expansion fitting portion 1110 is greater than the distance between the outlet end of the first air channel 2530 and the contraction fitting portion 1120. It can be understood that since the distance between the outlet end of the first air channel 2530 and the expansion fitting portion 1110 is greater than the distance between the outlet end of the first air channel 2530 and the contraction fitting portion 1120, that is, the outlet end of the first air channel 2530 is closer to the contraction fitting portion 1120, the thrust of the gas discharged from the outlet end of the first air channel 2530 on the old bulge 21b is enhanced, so that the sheet metal strip 200 is evenly stressed, the situation of backward deviation is reduced, and the accuracy of the subsequent stretching position is improved.

[0094] Combination Figure 6 As shown, in one embodiment, the ratio of the distance H between the outlet end of the first air channel 2530 and the shrinking fitting part 1120 to the distance L between the outlet end of the first air channel 2530 and the expansion fitting part 1110 is 0.618, that is, H:L=0.618. It can be understood that when the ratio of the distance between the outlet end of the first air channel 2530 and the expansion fitting part 1110 to the distance between the outlet end of the first air channel 2530 and the shrinking fitting part 1120 is 0.618, the thrust of the gas on the new bulge 21a and the thrust of the gas on the old bulge 21b tend to be consistent, that is, the force on the sheet metal strip 200 is more balanced, and the accuracy of the subsequent stretching position is further improved.

[0095] Similarly, in order to solve the problem of the sheet metal strip 200 being stuck in the retraction fitting part 1120 and the extension fitting part 1130, in one embodiment, a second stripping block 2610 is provided between the retraction fitting part 1120 and the extension fitting part 1130; a second telescopic groove 2620 is opened on the upper mold base 110, and the second stripping block 2610 is slidably set in the second telescopic groove 2620 and elastically connected to the bottom of the second telescopic groove 2620.

[0096] In one embodiment, a second buffer pad 2611 is provided on the side of the second stripping block 2610 facing the lower die base 120. In another embodiment, the second buffer pad 2611 is an air cushion, and an air outlet is provided on the side facing the lower die base 120.

[0097] In one embodiment, a second air channel 2630 is opened on the upper mold base 110 , and the second air channel 2630 is arranged between the retractable fitting portion 1120 and the protruding fitting portion 1130 , and an air outlet end of the second air channel 2630 faces the lower mold base 120 .

[0098] In one embodiment, the ratio of the distance G between the outlet end of the second air duct 2630 and the extending fitting portion 1130 to the distance F between the outlet end of the second air duct 2630 and the contracting fitting portion 1120 is 0.5, that is, G:F=0.5.

[0099] Typically, when the gas discharged from the outlet end of the first air duct 2530 and the gas discharged from the outlet end of the second air duct 2630 are the same compressed gas, since the surface area of ​​the new bulge 21a at the expansion fitting portion 1110 is much larger than the surface area of ​​the convex bump 220 at the extension fitting portion 1130, the thrust of the gas applied to the new bulge 21a at the expansion fitting portion 1110 will be much greater than the thrust of the gas applied to the convex bump 220 at the extension fitting portion 1130, which will aggravate the backward displacement of the sheet metal strip 200.

[0100] To solve the above problem, the pressure P2 of the gas discharged from the outlet of the second gas channel 2630 is greater than the pressure P1 of the gas discharged from the outlet of the first gas channel 2530, that is, the thrust of the convex bulge 220 at the top extension matching portion 1130 is increased, so that the force on the sheet metal strip 200 is more balanced, so as to improve the accuracy of the subsequent stretching position. Specifically, P2: P1 = 1.5.

[0101] In one of the embodiments, the first stripping block 2510 and the second stripping block 2610 are symmetrically arranged on both sides of the expansion fitting portion 1110, so that the sheet metal strip 200 can be subjected to more uniform force at two symmetrical positions of the expansion fitting portion 1110, thereby shortening the stripping time.

[0102] The present disclosure also provides a convex sheet metal part 240, which is formed by using a continuous stretching die 100 for convex forming including any of the above-mentioned embodiments. It can be understood that by applying the continuous stretching die 100 for convex forming of the present disclosure to the forming process of the convex sheet metal part 240, when the pre-forming area of ​​the sheet metal strip 200 is pushed to the expansion forming station, the pre-forming area of ​​the sheet metal strip 200 will be stretched and enlarged by the expansion punch 1310 to form a bulge 210; when the bulge 210 is pushed to the shrinking forming station, the stretching amount of the periphery of the bulge 210 will be squeezed toward the bulge 210 by the shrinking fitting part 1120. 0 is gathered at the top, so that the thickness of the periphery of the bulge 210 tends to be consistent, so that the top of the bulge 210 has stronger ductility; the bulge 210 is pushed to the top stretching forming station, and the top of the bulge 210 is further stretched by the top stretching punch 1330, and the thickness of the top of the bulge 210 will be reduced and tend to be consistent with the thickness of the periphery of the bulge 210, so that the overall thickness distribution of the bulge 220 on the convex sheet metal part 240 is more uniform, and it is less likely to be punctured by the punch during stretching.

[0103] Compared with the prior art, the present invention has at least the following advantages:

[0104] 1) Since the expansion punch 1310, the contraction punch 1320 and the extension punch 1330 are arranged in sequence and at intervals in the material strip pushing area 1210 along the pushing direction of the sheet metal strip 200, and the upper die base 110 is provided with an expansion fitting portion 1110 arranged opposite to the expansion punch 1310, a contraction fitting portion 1120 arranged opposite to the contraction punch 1320, and the extension fitting portion 1130 positioned opposite to the extension punch 1330, and since the upper die base 110 is raised and lowered above the material strip pushing area 1210, the diameter of the contraction punch 1320 is smaller than the diameter of the expansion punch 1310, when the sheet metal strip 200 is placed on the material strip pushing area 1210, the expansion forming station can stretch and expand the pre-forming area of ​​the sheet metal strip 200 and push it forward along with the sheet metal strip 200. Because the height of the extending punch 1330 is greater than the height of the expansion punch 1310 and the height of the contraction punch 1320, the pre-forming area of ​​the sheet metal strip 200 will be gathered by the contraction forming station and further stretched by the extending station in turn, and finally a bulge 220 with a greater stretching depth will be formed on the pre-forming area of ​​the sheet metal strip 200.

[0105] 2) Compared with the sheet metal surface bulge 220 forming tooling in the prior art, when the pre-forming area of ​​the sheet metal strip 200 is pushed to the expansion forming station, the pre-forming area of ​​the sheet metal strip 200 will be stretched and enlarged by the expansion punch 1310 to form a bulge 210; when the bulge 210 is pushed to the shrinking forming station, since the diameter of the shrinking punch 1320 is smaller than the diameter of the expansion punch 1310, the stretching amount of the periphery of the bulge 210 will be squeezed toward the top of the bulge 210 by the shrinking fitting part 1120, so that the periphery of the bulge 210 shrinks, that is, the bottom diameter of the bulge 210 shrinks within the range of 4mm to 5mm, and the periphery thickness of the bulge 210 can be made consistent. At the same time, as the stretching amount of the periphery of the bulge 210 gathers toward the top of the bulge 210, the material thickness of the top of the bulge 210 will increase, so that the top of the bulge 210 has stronger ductility; afterwards, the bulge 210 is pushed to the top extension forming station. Since the height of the top extension punch 1330 is greater than the height of the expansion punch 1310 and the height of the contraction punch 1320, the top of the bulge 210 will be further stretched by the top extension punch 1330. The thickness of the top of the bulge 210 will be reduced and tend to be consistent with the thickness of the periphery of the bulge 210, and finally a convex bulge 220 with a depth of 5mm to 6mm is formed. The thickness of the above-mentioned convex bulge 220 is more evenly distributed as a whole, and it is less likely to be punctured by the punch during stretching.

[0106] The above-mentioned embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the patent of the present disclosure shall be subject to the attached claims.

Claims

1. A continuous stretching die for convex hump forming, comprising an upper die seat and a lower die seat, wherein the lower die seat is provided with a material strip pushing area, and the material strip pushing area is used to place and push the sheet metal material strip; the upper die seat is lifted and arranged above the material strip pushing area; It is characterized in that The continuous stretching die for convex hull forming also includes a stretching punch assembly; The stretching punch assembly is arranged in the pushing area of ​​the material strip; the stretching punch assembly includes an expansion punch, a contraction punch and a top extension punch which are arranged in sequence and at intervals along the pushing direction of the sheet metal material strip, the diameter of the contraction punch is smaller than the diameter of the expansion punch, and the height of the top extension punch is simultaneously greater than the height of the expansion punch and the height of the contraction punch; an expansion fitting part, a contraction fitting part and a top extension fitting part are respectively arranged on the upper die seat; the expansion punch is opposite to the expansion fitting part and forms an expansion forming station; the contraction punch is opposite to the contraction fitting part and forms a contraction forming station; the top extension punch is opposite to the top extension fitting part and forms a top extension forming station; the expansion forming station, the contraction forming station and the top extension forming station are used to sequentially stretch the pre-forming area of ​​the sheet metal material strip to form a convex hump.

2. The continuous stretching die for convex hull forming according to claim 1, characterized in that: The end of the expansion punch, the end of the contraction punch and the end of the extension punch are all spherical cap-shaped.

3. The continuous stretching die for convex hull forming according to claim 2, characterized in that: The end curvature of the expansion punch, the end curvature of the contraction punch, and the end curvature of the extension punch increase in sequence.

4. The continuous stretching die for convex hull forming according to claim 1, characterized in that: The stretching punch assembly also includes a flattening punch; in the pushing direction along the sheet metal strip, the flattening punch is located on the side of the extension punch away from the retraction punch; the upper die seat is also provided with a flattening matching part; the flattening punch is opposite to the flattening matching part and forms a flattening forming station.

5. The continuous stretching die for convex hull forming according to claim 4, characterized in that: The end of the leveling punch is in a frustum-shaped form.

6. The continuous stretching die for convex hull forming according to claim 1, characterized in that: Punching heads and positioning pins are also provided at intervals on the lower die base; the punching heads and the positioning pins are arranged in sequence along the pushing direction of the sheet metal strip and face the strip pushing area; along the pushing direction of the sheet metal strip, the positioning pins are located on the side of the expansion fitting portion away from the contraction fitting portion.

7. The continuous stretching die for convex hull forming according to claim 1, characterized in that: The continuous stretching die for bulge forming also includes a slitting punch; the slitting punch is arranged on the upper die seat; in the pushing direction along the sheet metal strip, the slitting punch is located on the side of the extending fitting part away from the shrinking fitting part, and the slitting punch is used to punch the part between the two groups of bulges.

8. The continuous stretching die for convex hull forming according to claim 7, characterized in that: The continuous stretching die for bulge forming also includes a sheet edge bending assembly, which is arranged on the lower die base; in the pushing direction along the sheet metal strip, the sheet edge bending assembly is located on the side of the slitting punch away from the top extension fitting portion.

9. A convex hull stretching forming method, characterized in that: The method is performed by using the continuous stretching die for convex hull forming according to any one of claims 1 to 8; The convex hull stretching forming method comprises the following steps: Obtaining a sheet metal strip, and placing the sheet metal strip in the strip pushing area; Pushing the pre-formed area of ​​the sheet metal strip to the expansion forming station so that the expansion punch stretches a bulge on the sheet metal strip; Pushing the bulge to the shrinking and forming station so that the shrinking and fitting part squeezes and shrinks the stretch amount of the bulge periphery; The bulge is pushed to the top stretching forming station so that the top stretching punch stretches the top of the bulge to obtain a convex bulge.

10. A convex sheet metal part, characterized in that: The convex hull stretching molding method according to claim 9 is used to make the convex hull.

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