Sectional material group stretch-bending forming die and method based on stretching arm type stretch-bending machine tool

Abstract

According to the sectional material group stretch-bending forming die and method based on the stretching arm type stretch-bending machine tool, through the combination mode of different parts and the combination of basic technical parameters of stretch-bending machine tool machining, the overall stretch-bending forming die is designed and constructed, and the technological method for multi-project sectional material group stretch-bending forming is achieved for the first time. The forming limitation different from traditional single part forming is adopted, the machine tool forming limit is utilized, parts which cannot be formed through a stretch-bending machine are combined to form a long blank, and the stretch-bending forming technology is achieved. According to the method, the reasonable stretch-bending forming die and the reasonable technological blank length are designed, parts such as bending parts, Yao machine forming parts and manual forming parts which cannot be subjected to stretch-bending forming can be formed in a stretch-bending forming mode, the internal pressure stress of the parts is converted into the tensile stress, the mobility of materials in the part forming process is balanced, and the forming quality of the parts is improved. And part forming springback is effectively reduced.

Description

Technical Field

[0001] The present application belongs to the technical field of stretch-bending forming of profile products, and specifically relates to a profile group stretch-bending forming die and method based on a cantilever-type stretch-bending machine tool. Background Art

[0002] The fuselage of an aircraft is a typical cylindrical assembly structure. The most important parts of the cylindrical structure of the fuselage are the frame edge parts of the frame planes of each fuselage. Among the frame edge parts, the most common parts are the frame edge strips processed by profiles. The bending profiles are mostly theoretical profiles connected to the outer skin of the aircraft, so the product shape accuracy is high and the processing is difficult. Therefore, in the processing of such parts, the stretch bending forming method is often used; the advantage of stretch bending forming is that applying tension while bending can significantly reduce springback. When applying tension during bending, both the inner and outer areas are elongated, and they are shortened after unloading. The rebound trends of the inner and outer areas have a mutually offsetting effect, which can significantly reduce the springback amount and achieve high forming accuracy.

[0003] However, in the traditional stretch-bending processing, the two-dimensional drawings cannot fully express the appearance of the parts, the digital application is not comprehensive, the processing capacity of the production site equipment is insufficient, the aircraft products are multi-variety and small batch characteristics, etc. The stretch-bending forming molds are designed for a single product part, and a single part product is produced during production, resulting in low production efficiency. In addition, the production cost of a single stretch-bending forming mold is high and the utilization rate is low, which has long restricted production.

[0004] For product parts that are too small to be formed by stretch bending, such as press bending, machine forming, and manual forming, the deformation process during the forming process is completely through bending to cause the product parts to produce plastic deformation. This type of forming method will lead to excessive bending stress inside the product parts, large springback, and poor forming effect. Summary of the invention

[0005] Purpose of the invention: In order to solve the problems of low production efficiency of stretch-bending production of single product parts, high mold production cost, long-term production constraints and the inability to use stretch-bending to form small-sized product parts, the present invention provides a group stretch-bending method for profiles based on a cantilever stretch-bending machine.

[0006] In a first aspect, the present application provides a group bending forming die for a profile based on a cantilever type bending machine, the die comprising:

[0007] An upper die having an upper die working surface;

[0008] The lower die has a limiting surface, and the limiting surface is used to limit the displacement of the group of stretch-bending forming raw material bodies during the stretch-bending forming process; the lower die is fitted with the upper die, and the upper die working surface and the limiting surface together form a stretch-bending forming working surface;

[0009] Preferably, the upper die working surface is an arc surface, and the limiting surface is a plane.

[0010] Preferably, the upper die working surface is determined according to the appearance characteristics of a plurality of parts.

[0011] In a second aspect, the present application also provides a group stretch-bending forming method for profiles based on a cantilever stretch-bending machine, the method comprising:

[0012] Calculate the length of the rough material body formed by group stretch bending;

[0013] Through the cantilever type stretch bending machine, the stretch bending forming is performed based on the die to obtain a group of stretch bending bodies;

[0014] The group of stretch-bent bodies are cut to obtain a plurality of parts.

[0015] Preferably, the stretch-bending forming is performed by a cantilever-type stretch-bending machine based on a mold to obtain a group of stretch-bent bodies, including:

[0016] Placing the group of stretch-bent raw materials on the upper die working surface, and limiting the displacement of the group of stretch-bent raw materials by the limiting surface;

[0017] The grouped stretch-bend forming rough material body is stretch-bent by means of a cantilevered stretch-bend machine tool to obtain a grouped stretch-bend body.

[0018] Preferably, the calculating of the length of the group-bending forming rough material body comprises:

[0019] The forming working surface is expanded in the direction of the end tangent to obtain the expanded surface of the overall forming working surface, and its length dimension is recorded as L z , then the length of the raw material body L m The degree calculation method is shown in formula (1):

[0020] L m =L z +2(J+L 1 +L 2 ) (1)

[0021] L z —The length dimension of the unfolded surface of the overall working profile;

[0022] J—Clamping size of the bending machine jaws;

[0023] L 1 —Dimensions from the jaws of the bending machine to the end of the bending die;

[0024] L 2 —Dimension from the edge of the part to the end of the drawing and bending die.

[0025] Preferably, the calculating of the length of the group-bending forming rough material body comprises:

[0026] The product digital model bending surface is extracted, and then unfolded in the end tangent direction to obtain the unfolded length dimension of each product bending surface, which is recorded as L zi , then the length of the raw material body L m The degree calculation method is shown in formula (2):

[0027]

[0028] L zi —The unfolded length dimension of the curved surface of each product, i is 1, 2, 3…;

[0029] n—the number of products contained in the group of stretch-bending bodies;

[0030] ΔL 1 —The length of the transition extension profile between two products.

[0031] Preferably, the method further comprises:

[0032] The combined structural form is determined according to all the external features of the parts that make up the group of stretch-bent parts.

[0033] This application has the following technical effects:

[0034] 1. The present invention can use stretch-bending to form parts that cannot be formed by stretch-bending, such as press-bending, machine-formed parts, and manual forming, by designing a reasonable stretch-bending forming die and process blank length, thereby converting the internal compressive stress of the parts into tensile stress, balancing the fluidity of the material during the part forming process, and effectively reducing the part forming springback, so that the product parts have a precise appearance after forming and the product parts have high forming quality.

[0035] 2. A group stretch-bending forming die is designed. The parts processed by this group stretch-bending forming method are extremely efficient. Multiple product parts can be processed on demand at one time, which reduces the number of tooling installations and the number of product parts clamping. The production cost is low and higher batch production economic benefits can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of the group stretch-bending forming product parts and the stretch-bending die;

[0037] Figure 2 It is a schematic diagram of a group of stretch-bent forming bodies and the development of their bending profiles;

[0038] Figure 3 It is a schematic diagram of the calculation of the rough material size of the group stretch-bending forming body;

[0039] Figure 4 It is a schematic diagram of calculating the area division of the centroid position in the width direction of the edge strip surface of the profile section;

[0040] Wherein: 1. lower die of the stretch-bending die; 2. upper die of the stretch-bending die; 3. product part (1); 4. product part (2); 5. product part (3); 6. grouped stretch-bending formed body; 7. unfolded surface of the bending surface of the grouped stretch-bending formed body. DETAILED DESCRIPTION

[0041] The present invention discloses a method for group bending and forming of profiles based on a cantilever type bending machine. Through different parts combination methods and combined with basic technical parameters of bending machine processing, an integral bending and forming die is designed and constructed to realize the process method of group bending and forming of multiple profiles for the first time. Different from the limitations of traditional single part forming, the present invention utilizes the forming limit of the machine tool to combine parts that cannot be formed by a bending machine to form a longer rough material to realize the bending and forming process. This method can form parts that cannot be formed by bending, such as press bending, Yagao machine forming parts, manual forming, etc. by designing a reasonable bending and forming die and process blank length, and convert the internal compressive stress of the parts into tensile stress, balance the fluidity of the material during the forming process of the parts, and effectively reduce the forming rebound of the parts. The parts processed by this method of group bending and forming of profiles have extremely high processing efficiency, and multiple parts can be processed as needed at one time, with low production cost, and can achieve higher batch production economic benefits.

[0042] See also Figure 1-Figure 4 , a group stretch-bending forming method for profiles based on a cantilevered stretch-bending machine is provided, including a stretch-bending die and a group stretch-bending forming rough material body, wherein the stretch-bending die includes an upper die and a lower die, and the upper die working surface and the lower die together constitute the stretch-bending forming working surface. The upper die working surface should be 5mm higher than the maximum size of the rough material body, the stretch-bending die working surface is designed in combination, the length of the group stretch-bending forming rough material body is calculated, and the group stretch-bending forming rough material body is stretched and bent by a cantilevered stretch-bending machine to obtain a group stretch-bending body, and then the group stretch-bending body is cut to obtain the final part. The specific method is as follows:

[0043] Step 1: Determine the combined structural form according to all the external features of the grouped stretch-bending formed parts;

[0044] Step 2: Design the group bending die;

[0045] Step 3: Calculate the length of the rough material body formed by group stretch bending;

[0046] Step 4: stretch bending;

[0047] Step 5: cutting the grouped bent bodies.

[0048] The product combination structure determined in step 1 is a group structure established in the CATIA environment by combining the product models of the required processing parts. The specific process is as follows:

[0049] 2-1 The selected grouped stretch-bending bodies are all of the same brand, state, and specification profiles. Assemble the product digital models required for the grouped stretch-bending bodies in the CATIA environment. When assembling the grouped stretch-bending bodies, try to arrange the product digital models into a symmetrical structure to facilitate the subsequent manufacturing of the stretch-bending molds and installation on the stretch-bending machine to accurately distribute the forming load of the parts. Mark the boundary lines of each end of the product digital model, recorded as a, b, c, d, e, f... Take the end a of part 1 of the product digital model as the design end reference of the stretch-bending die, extract the bending surface of the grouped stretch-bending body on the product digital model 1, and perform an extrapolated extension ΔL at the b boundary. 1 , get the transition extension profile, constrain the end c of the product model 2 to be consistent and tangent to the extrapolated extension edge line. Then extrapolate and extend ΔL on the boundary d of the product model 2 2 The transition extension profile is obtained again, and the end c of the product digital model 3 is constrained to coincide and be tangent to the external extension edge line to obtain the forming working profile.

[0050] 2-2 Draw a straight line between the two edges a and f of the obtained integral forming working surface, which is the plane chord length n of the forming working surface; the chord height of the forming working surface is recorded as m;

[0051] The bending die structure determined in step 2 is based on the plane chord length n of the overall forming work surface obtained in step 1 and the chord height m on the overall forming work surface, and is designed in combination with the requirements of the mold design specification. The specific process is as follows:

[0052] 3-1 The plane chord length n of the forming working surface is used as the reference value of the design length L of the bending die. The digital model of each section of the product and the transition extension profile of each connecting section are extracted and combined to obtain the overall forming working profile, which is designed as the bending die working surface. In the mold design, in order to prevent the swing arm from swinging too much during the bending forming process, a dead bend is formed in the actual product, resulting in a deviation in the shape of the part; the two ends of the overall working surface are extended by L 1 , leaving margin for the actual part forming. The mold design length dimension L should not exceed the limit forming distance between the two jaws of the bending machine. To prevent the length of the stretch-bending forming raw material from being too large, the friction between the stretch-bending die increased, the plastic forming resistance in the middle part of the stretch-bending forming raw material too large, and the material flowability reduced, resulting in poor forming performance and large springback in the middle part of the stretch-bending forming raw material; the plane chord height line m of the forming working surface should not exceed the limit size of the stretch-bending machine tooling table to prevent the stretch-bending forming raw material from being deformed too much during the forming process, the overall curvature deformation, and deviation from the overall theoretical size.

[0053] 3-2 The maximum design dimension of the width B of the bending die should not exceed the distance between the swing arm of the bending machine and the rear top plate of the bending machine. At the same time, the minimum width dimension B of the bending die should ensure that the installation dimension on the bending machine is 300mm≤B. When the bending body is assembled symmetrically as described in step 1, the product digital model should be arranged as a symmetrical structure as much as possible to facilitate the subsequent bending die manufacturing and installation on the bending machine to accurately distribute the forming load of the parts. If it is an asymmetric combined bending body structure, it is necessary to calculate the center line of the bending die according to the asymmetric bending die installation method to install the bending die.

[0054] Step 3: Calculate the length of the group bending raw material. There are two ways to calculate the length of the group bending raw material, the specific methods are as follows:

[0055] 4-1 One calculation method is to first unfold the integral forming working surface obtained in step 2 in the direction of the end tangent to obtain the unfolded surface of the integral forming working surface, and its length dimension is recorded as L z , then the length dimension L of the group bending body raw material m The degree calculation method is shown in formula (1).

[0056] L m =L z +2(J+L 1 +L 2 ) (1)

[0057] L z —The length dimension of the unfolded surface of the overall working profile;

[0058] J—Clamping size of the bending machine jaws;

[0059] L 1 —Dimensions from the jaws of the bending machine to the end of the bending die;

[0060] L 2 —Dimension from the edge of the part to the end of the drawing and bending die.

[0061] 4-2 Another calculation method is to extract the product digital model bending surface, and then unfold it in the direction of the end tangent line, and obtain the unfolded length dimension of each product bending surface, which is recorded as L zi , then the length dimension L of the group bending body raw material mThe degree calculation method is shown in formula (2).

[0062]

[0063] L zi —The unfolded length dimension of the curved surface of each product, i is 1, 2, 3…;

[0064] n—the number of products contained in the group of stretch-bending bodies;

[0065] ΔL 1 — Transition extension profile length between two products;

[0066] The meanings of other symbols are the same as those in formula (1).

[0067] Step 3: stretch bending and forming. The specific process is as follows:

[0068] 5-1 saw and cut the raw material of the grouped stretch-bending forming body according to the length size of step 3, remove the edge burrs, and prevent stress concentration from causing breakage during the stretch-bending forming process; obtain the raw material of the grouped stretch-bending forming body.

[0069] 5-2 Install the group bending die designed in step 2 onto the working platform of the bending machine, align the mounting holes of the group bending die with the die mounting columns of the working platform of the bending machine, lay the die flat until it is stable, and adjust the centerline height of the forming surface of the group bending die to be consistent with the centerline height of the jaws of the bending machine.

[0070] 5-3 Clamp the group bending forming body and lubricate it. Replace the chuck that matches the selected profile specifications, and insert the group bending forming body into the chuck at both ends, with a length of J, and then tighten it. Apply lubricating oil on the working surface of the group bending die.

[0071] 5-4 Perform the stretching and bending operation. The first stretching and bending is performed in the newly quenched state. The loading method is "stretching-bending-supplementing stretching". After bending and forming, appropriate stretching is performed. The secondary stretching and bending is used for products with a large degree of deformation and a cross-sectional thickness greater than 3mm and a width greater than 40mm. The annealed profile rough material is used for the first stretching and bending. The rough material is pre-stretched and then bent according to the "stretching-bending" loading method. After the film is applied to the rough material, it is removed and quenched. In the new quenched state, the second stretching and bending is performed according to the "bending-stretching" loading method. At this time, the pre-stretched and bent parts are bent first, and tension is applied after the mold is applied.

[0072] 5-5 After the stretch-bending is completed, the product shape marking line is marked on the group stretch-bending formed body after the stretch-bending is formed according to the product shape line shown on the group stretch-bending die.

[0073] Step 5 is to cut the grouped stretch-bent bodies according to the product shape marking lines on the grouped stretch-bent formed bodies obtained in step 4, so as to obtain a single product object whose shape meets the requirements of the product digital model.

[0074] In other embodiments of the present application, a group bending forming method based on a cantilever bending machine is provided, wherein the group bending forming body is established in a CATIA environment, the bending die includes an upper die and a lower die, the upper die working surface and the lower die together form a bending forming working surface, and the working surface is extracted according to the synthetic bending profile of the group bending forming body. And the length of the group bending forming rough body is calculated, and the forming method includes the following steps:

[0075] Step 1: Determine the combined structural form according to the bending profile features of the parts of the grouped stretch-bending formed products;

[0076] Step 1-1: The selected grouped stretch-bending bodies are all of the same brand, state, and specification profiles. Assemble the product digital models required for the grouped stretch-bending bodies in the CATIA environment. When assembling the grouped stretch-bending bodies, try to arrange the product digital models into a symmetrical structure to facilitate the subsequent manufacturing of the stretch-bending dies and installation on the stretch-bending machine to accurately distribute the forming load of the parts. Mark the boundary lines of each end of the product digital model as a, b, c, d, e, and f. Use the end a of part 1 of product digital model 1 as the design end reference for the stretch-bending die, extract the bending surface of the grouped stretch-bending body on the product digital model 1, and perform an extrapolated extension ΔL at the b boundary. 1 = 80mm, and the transition extension profile is obtained. The end c of the product model 2 is constrained to coincide and be tangent to the extrapolated extension edge line. Then, the extrapolated extension ΔL is performed on the boundary d of the product model 2. 2 = 80mm to obtain the transition extension surface again, and constrain the product digital model 3 end c to match and tangent to the external extension edge line to obtain the forming working surface.

[0077] Step 1-2: Draw a straight line between the two edges a and f of the obtained integral forming working surface, which is the plane chord length n of the curved surface of the forming working surface; the chord height of the forming working surface is recorded as m;

[0078] Step 2: Design the group bending die;

[0079] Step 2-1: The plane chord length n of the forming working surface is used as the reference value of the design length L of the bending die. The digital model of each section of the product and the transition extension profile of each connecting section are extracted and combined to obtain the overall forming working profile, which is designed as the bending die working surface. In the mold design, in order to prevent the swing arm from swinging too much during the bending forming process, a dead bend is formed in the actual product, resulting in a deviation in the shape of the part; the two ends of the overall working surface are extended by L 1 = 100mm, leaving margin for actual part forming. The mold design length L should not exceed the limit forming distance between the two jaws of the bending machine. To prevent the length of the stretch-bending raw material from being too long, the friction between it and the stretch-bending die will increase, the plastic forming resistance of the middle part of the stretch-bending raw material will be too large, and the material flow performance will be reduced, resulting in poor forming performance and large springback in the middle of the stretch-bending raw material. The plane chord height m of the forming working surface should not exceed the limit size of the stretch-bending machine tooling table to prevent the stretch-bending raw material from being deformed too much during the forming process, the overall curvature will be deformed, and the overall theoretical size will be deviated.

[0080] Step 2-2: The maximum design dimension of the width B of the bending die should not exceed the distance between the swing arm of the bending machine and the rear top plate of the bending machine. At the same time, the minimum width B of the bending die should ensure that the installation dimension on the bending machine is 300mm≤B. When the bending body is assembled symmetrically as described in step 1, the product digital model should be arranged as a symmetrical structure as much as possible, so as to facilitate the subsequent bending die manufacturing and installation on the bending machine to accurately distribute the forming load of the parts. If it is an asymmetric combined bending body structure, it is necessary to calculate the center line of the bending die according to the asymmetric bending die installation method to install the bending die.

[0081] Step 3: Calculate the length of the rough material body to be formed by group stretch bending;

[0082] Step 3-1: One calculation method is to first unfold the integral forming working surface obtained in step 2 in the direction of the end tangent to obtain the unfolded surface of the integral forming working surface, and its length dimension is recorded as L z , then the length dimension L of the group bending body raw material m The degree calculation method is shown in formula (1).

[0083] L m =L z +2(J+L 1 +L 2 ) (1)

[0084] L z —The length dimension of the unfolded surface of the overall working profile;

[0085] J—Clamping size of the bending machine jaws;

[0086] L 1 —Dimensions from the jaws of the bending machine to the end of the bending die;

[0087] L 2 —Dimension from the edge of the part to the end of the drawing and bending die.

[0088] Step 3-2: Another calculation method is to extract the product digital model bending surface, and then unfold it in the direction of the end tangent, and obtain the unfolded length dimension of each product bending surface as L zi , then the length dimension L of the group bending body raw material mThe degree calculation method is shown in formula (2).

[0089]

[0090] L zi —The developed length dimension of the curved surface of each product part, i is 1, 2…;

[0091] n—the number of products contained in the group of stretch-bending bodies;

[0092] ΔL 1 — Transition extension profile length between two product parts;

[0093] The meanings of other symbols are the same as those in formula (1).

[0094] Step 4: stretch bending;

[0095] Step 4-1: sawing and cutting the grouped stretch-bending forming body raw material according to the length size of step 3, removing edge burrs, and preventing stress concentration from causing fracture during the stretch-bending forming process; obtaining the grouped stretch-bending forming body raw material.

[0096] Step 4-2: Install the group bending die designed in step 2 on the working platform of the bending machine, align the mounting hole of the group bending die with the die mounting column of the working platform of the bending machine, lay it flat until the bending die is stable, and adjust the center line height of the forming surface of the group bending die to be consistent with the center line height of the jaws of the bending machine.

[0097] Step 4-3: Clamp the group bending forming body and lubricate it. Replace the chuck that matches the selected profile specifications, and insert the group bending forming body into the chuck at both ends, with a length of J, and then tighten it. Apply lubricating oil on the working surface of the group bending die.

[0098] Step 4-4: Perform the stretching and bending operation. The first stretching and bending is performed in the newly quenched state. According to the loading method of "stretching-bending-supplementing", pre-stretching is performed by about 0.7% to 1%. After stretching and bending, appropriate supplementary stretching is performed. The secondary stretching and bending is used for products with a large degree of deformation, a cross-sectional thickness greater than 3mm, and a width greater than 40mm. During the first stretching and bending, annealed profile rough material is used. According to the loading method of "stretching-bending", pre-stretching is performed by about 1%, and then bending. After the rough material is filmed, it is removed and quenched. In the newly quenched state, the second stretching and bending is performed according to the loading method of "bending-stretching". At this time, the pre-stretched and bent parts are bent first, and tension is applied after the mold is attached. Tension is applied after the mold is attached.

[0099] Step 4-5: After the stretch-bending is completed, the product part outline marking line is marked on the group stretch-bending formed body after the stretch-bending is completed according to the product part outline line shown on the group stretch-bending die.

[0100] Step 5: Cut the grouped bending bodies.

[0101] Cutting is performed according to the product part outline markings drawn on the grouped stretch-bending forming body to obtain a plurality of single product parts whose bending outlines conform to the product digital model.

[0102] like Figure 1-4 As shown, a group bending forming method based on a cantilever type bending machine tool profile, the aircraft frame profile parts product provided by the embodiment shown is as follows Figure 1 The curved shape of the product parts shown in product parts (1) 3, product parts (2) 4, and product parts (3) 5 is the shape of the right side skin of the aircraft, and the shape is hyperbolic; the material is 7050-O-XC111-27, and the material thickness δ=2mm, which is a typical aircraft frame edge part.

[0103] Step 1: Determine the combined structural form according to the bending profile features of the parts of the grouped stretch-bending formed products;

[0104] Step 1-1: Assemble the product digital models required for the group of stretch-bending bodies in the CATIA environment. When assembling the group of stretch-bending bodies, arrange the product digital models into a symmetrical structure to facilitate the subsequent manufacturing of the stretch-bending die and installation on the stretch-bending machine to accurately distribute the forming load of the parts. Mark the boundary lines of each end of the product digital model as a, b, c, d, e, and f. Use the end a of part 1 of product digital model 1 as the end reference for the design of the stretch-bending die, extract the bending surface of the group of stretch-bending bodies on the product digital model 1, and perform an extrapolation extension ΔL at the b boundary. 1 = 80mm, and the transition extension profile is obtained. The end c of the product model 2 is constrained to coincide and be tangent to the extrapolated extension edge line. Then, the extrapolated extension ΔL is performed on the boundary d of the product model 2. 2 = 80mm to obtain the transition extension surface again, and constrain the product digital model 3 end c to match and tangent to the external extension edge line to obtain the forming working surface.

[0105] Step 1-2: Draw a straight line between the two edges a and f of the obtained integral forming working surface, which is the plane chord length n of the curved surface of the forming working surface; the chord height of the forming working surface is recorded as m;

[0106] Step 2: Design the group bending die;

[0107] Step 2-1: The plane chord length n of the forming working surface is used as the reference value of the design length L of the bending die. The digital model of each section of the product and the transition extension profile of each connecting section are extracted and combined to obtain the overall forming working profile, which is designed as the bending die working surface. In the mold design, in order to prevent the swing arm from swinging too much during the bending forming process, a dead bend is formed in the actual product, resulting in a deviation in the shape of the part; the two ends of the overall working surface are extended by L 1= 100mm, leaving margin for actual part forming. The mold design length L should not exceed the limit forming distance between the two jaws of the bending machine. To prevent the length of the stretch-bending raw material from being too long, the friction between it and the stretch-bending die will increase, the plastic forming resistance of the middle part of the stretch-bending raw material will be too large, and the material flow performance will be reduced, resulting in poor forming performance and large springback in the middle of the stretch-bending raw material. The plane chord height m of the forming working surface should not exceed the limit size of the stretch-bending machine tooling table to prevent the stretch-bending raw material from being deformed too much during the forming process, the overall curvature will be deformed, and the overall theoretical size will be deviated.

[0108] Step 2-2: The maximum design dimension of the width B of the bending die should not exceed the distance between the swing arm of the bending machine and the rear top plate of the bending machine. At the same time, the minimum width B of the bending die should ensure that the installation dimension on the bending machine is 300mm≤B. When the bending body is assembled symmetrically as described in step 1, the product digital model should be arranged as a symmetrical structure as much as possible, so as to facilitate the subsequent bending die manufacturing and installation on the bending machine to accurately distribute the forming load of the parts. If it is an asymmetric combined bending body structure, it is necessary to calculate the center line of the bending die according to the asymmetric bending die installation method to install the bending die.

[0109] Step 3: Calculate the length of the rough material body to be formed by group stretch bending;

[0110] Step 3-1: One calculation method is to first unfold the integral forming working surface obtained in step 2 in the direction of the end tangent to obtain the unfolded surface of the integral forming working surface, and its length dimension is recorded as L z =2032mm, then the length dimension L of the raw material of the group bending body m The degree calculation method is shown in formula (1).

[0111] L m =L z +2(J+L 1 +L 2 )=2032mm+2(80+100+100)mm=2592mm (1)

[0112] Step 3-2: Another calculation method is to extract the product digital model bending surface, and then unfold it in the direction of the end tangent, and obtain the unfolded length dimension of each product bending surface as L zi , then the length dimension L of the group bending body raw material m The degree calculation method is shown in formula (2).

[0113]

[0114] Step 4: stretch bending;

[0115] Step 4-1: sawing and cutting the grouped stretch-bending forming body raw material according to the length size of step 3, removing edge burrs, and preventing stress concentration from causing fracture during the stretch-bending forming process; obtaining the grouped stretch-bending forming body raw material.

[0116] Step 4-2: Install the group bending die designed in step 2 on the working platform of the bending machine, align the mounting hole of the group bending die with the die mounting column of the working platform of the bending machine, lay it flat until the bending die is stable, and adjust the center line height of the forming surface of the group bending die to be consistent with the center line height of the jaws of the bending machine.

[0117] Step 4-3: Clamp the group bending forming body and lubricate it. Replace the chuck that matches the selected profile specifications, and insert the group bending forming body into the chuck at both ends, with a length of J, and then tighten it. Apply lubricating oil on the working surface of the group bending die.

[0118] Step 4-4: Perform the stretching and bending operation. The first stretching and bending is performed in the newly quenched state. According to the loading method of "stretching-bending-supplementing", pre-stretching is performed by about 0.7% to 1%. After stretching and bending, appropriate supplementary stretching is performed. The secondary stretching and bending is used for products with a large degree of deformation, a cross-sectional thickness greater than 3mm, and a width greater than 40mm. During the first stretching and bending, annealed profile rough material is used. According to the loading method of "stretching-bending", pre-stretching is performed by about 1%, and then bending. After the rough material is filmed, it is removed and quenched. In the newly quenched state, the second stretching and bending is performed according to the loading method of "bending-stretching". At this time, the pre-stretched and bent parts are bent first, and tension is applied after the mold is attached. Tension is applied after the mold is attached.

[0119] Step 4-5: After the stretch-bending is completed, the product part outline marking line is marked on the group stretch-bending formed body after the stretch-bending is completed according to the product part outline line shown on the group stretch-bending die.

[0120] Step 5: Cut the grouped bending bodies.

[0121] Cutting is performed according to the product part outline markings drawn on the grouped stretch-bending forming body to obtain a plurality of single product parts whose bending outlines conform to the product digital model.

Claims

1. A group bending forming die for profiles based on a cantilever type bending machine, characterized in that: The mold comprises: An upper die having an upper die working surface; The lower die has a limiting surface, which is used to limit the displacement of the grouped stretch-bending raw material body during the stretch-bending forming process; the lower die is fitted with the upper die, and the upper die working surface and the limiting surface together form the stretch-bending forming working surface.

2. The mold according to claim 1, characterized in that: The upper die working surface is an arc surface, and the limiting surface is a plane.

3. The mold according to claim 2, characterized in that: The upper die working surface is determined according to the appearance characteristics of multiple parts.

4. A group stretch bending forming method based on a cantilever type stretch bending machine, characterized in that: The method comprises: Calculate the length of the rough material body formed by group stretch bending; Through the cantilever type stretch bending machine, the stretch bending forming is performed based on the die to obtain a group of stretch-bent bodies; The group of stretch-bent bodies are cut to obtain a plurality of parts.

5. The method according to claim 4, characterized in that The method of forming a group of stretch-bent bodies by stretch-bending the body through a cantilever-type stretch-bending machine based on a mold comprises: Placing the group of stretch-bent raw materials on the upper die working surface, and limiting the displacement of the group of stretch-bent raw materials by the limiting surface; The grouped stretch-bending raw material bodies are stretch-bent by means of a cantilevered stretch-bending machine to obtain grouped stretch-bent bodies.

6. The method according to claim 4, characterized in that The method of calculating the length of the group-bending rough material body comprises: The forming working surface is expanded in the direction of the end tangent to obtain the expanded surface of the overall forming working surface, and its length dimension is recorded as L z , then the length of the raw material body L m The degree calculation method is shown in formula (1): L m =L z +2(J+L1+L2) (1) L z —The length dimension of the unfolded surface of the overall working profile; J—Clamping size of the bending machine jaws; L1—The size from the jaws of the bending machine to the end of the bending die; L2 - The dimension from the edge of the part to the end of the bending die.

7. The method according to claim 4, characterized in that The method of calculating the length of the group-bending rough material body comprises: The product digital model bending surface is extracted, and then unfolded in the end tangent direction to obtain the unfolded length dimension of each product bending surface, which is recorded as L zi , then the length of the raw material body L m The degree calculation method is shown in formula (2): L zi —The unfolded length dimension of the curved surface of each product, i is 1, 2, 3…; n—the number of products contained in the group of stretch-bending bodies; ΔL1—Transition extension surface length between two products.

8. The method according to claim 4, characterized in that The method further comprises: The combined structural form is determined according to all the external features of the parts that constitute the group of stretch-bending parts.

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