Forming device and method for improving the drawing forming limit of ferromagnetic sheet materials

Abstract

The present invention provides a forming device and method for improving the drawing forming limit of ferromagnetic sheet materials, which includes an upper template, a lower template, a punch, a punch fixing plate, a spring, a blank holder, a die, a guide bushing, a guide pillar, a limiting member, a displacement sensor and a current controller; the punch is fixed at the middle position of the upper template through the punch fixing plate, a limiting member is arranged on each side of the upper template, the blank holder is connected to the upper template by means of the limiting member and can move up and down with the upper template, grooves for placing the spring are formed on both the punch fixing plate and the blank holder, the die is fixed at the middle position of the lower template through countersunk head bolts, and a blank is placed on the upper surface of the die. By increasing the friction force between the sheet material and the punch during the drawing process, the present invention reduces the maximum tensile stress suffered by the sheet material at the intersection of the straight wall area and the bottom fillet area, thereby reducing the thinning rate of the sheet material at the dangerous part, reducing the cracking risk at this place, and improving the forming limit of the sheet material.

Description

Technical Field

[0001] The present invention relates to the technical field of plastic material processing, and particularly relates to a forming device and method for improving the drawing forming limit of ferromagnetic sheet materials. Background Art

[0002] Sheet metal drawing forming is a plastic processing method that utilizes the plasticity of metal materials and uses a drawing die to form the sheet material to be processed into parts. Compared with machining methods, the efficiency and material utilization rate of drawing forming have been significantly improved, so it has been widely used in the military, aerospace, civilian, and medical fields.

[0003] During the thin sheet drawing process, fracture is one of the main failure forms. During the drawing process of straight-wall forming parts, the sheet material in the straight-wall area is subjected to tensile stress. Generally speaking, the tensile stress is the largest at the intersection of the straight-wall area and the bottom fillet area, and the thickness of the sheet material at this part is the thinnest, that is, the sheet material at this part is most likely to crack, which is the cracking risk area during the drawing forming process. How to suppress the cracking of straight-wall forming parts during the drawing forming process and improve the forming limit of metal sheet materials has become a technical problem that needs to be solved by technical personnel in this technical field.

[0004] In recent years, research has shown that providing a radial force to the formed part of the sheet material during the drawing process and increasing the beneficial friction between the punch and the sheet material can reduce the tensile stress on the sheet material in the straight-wall area, reduce the cracking risk, and improve the forming limit of the sheet material. However, the current method of applying radial force is mainly hydraulic loading, which leads to a complex structure of the drawing die and low drawing efficiency. Therefore, how to invent a device that can provide a stable additional force without reducing the drawing efficiency is an urgent problem to be solved. Summary of the Invention

[0005] In order to solve the above deficiencies of the prior art, the present invention proposes a stretching device and method for improving the drawing forming limit of ferromagnetic sheet materials, which adds an electro-permanent magnet technology on the basis of the existing drawing process. By increasing the friction between the sheet material and the punch during the drawing process, the maximum tensile stress on the sheet material at the intersection of the straight-wall area and the bottom fillet area is reduced, thereby reducing the thinning rate of the sheet material at the dangerous part, reducing the cracking risk at this part, and improving the forming limit of the sheet material.

[0006] Specifically, the present invention provides a device for improving the drawing forming limit of ferromagnetic sheet materials, which includes an upper template, a lower template, a punch, a punch fixing plate, a spring, a blank holder, a die, a guide bushing, a guide post, a limiting member, a displacement sensor, and a current controller;

[0007] The punch is fixed at the middle position of the upper template through the punch fixing plate. A limiting member is arranged on each side of the upper template. The blank holder is connected to the upper template by means of the limiting member and can move up and down with the upper template. Grooves for placing springs are formed on both the punch fixing plate and the blank holder. The die is fixed at the middle position of the lower template through countersunk head bolts, and a blank is placed on the upper surface of the die.

[0008] The upper template is connected with the guide bushing by interference fit. The lower template is connected with the guide post by interference fit. The guide bushing and the guide post cooperate with each other, and the upper template and the lower template are positioned by means of the guide bushing and the guide post.

[0009] The limiting member limits the blank holder after the blank holder contacts the sheet material. The spring is compressed as the distance between the punch fixing plate and the blank holder decreases during the drawing process, providing a blank holding force for the blank holder.

[0010] The magnitude of the required blank holding force is calculated according to the following formula:

[0011]

[0012]

[0013]

[0014] In the formula, Q is the blank holding force, with the unit of N; U θ is the deformation energy released by the circumferential elongation stress of the blank, with the unit of J; U ω is the deformation force required for bending when the blank is unstable and wrinkled, with the unit of J; R0 is the initial radius of the blank, with the unit of mm; k μ is the blank holding force coefficient; y m is the wrinkling height, with the unit of mm; t is the thickness of the blank, with the unit of mm; is the central angle corresponding to a single wave; R ω is the radius of the outer edge of the flange, with the unit of mm; r0 is the radius at the entrance of the die, with the unit of mm; is the central angle corresponding to any arc segment in a single wave; is related to related function; ρ is the radial coordinate, with the unit of mm; σ θ is the circumferential stress, with the unit of MPa; n is the hardening index; B is the strength coefficient, with the unit of MPa; ε is the strain;

[0015] The punch includes a punch body, a magnetic component, and a control component. Grooves are formed on the straight wall surfaces of the punch body, and a magnetic component is arranged in the grooves. The magnetic component includes a plurality of permanent magnets, a plurality of magnetic conductors, a plurality of reversible magnets, and a plurality of coils. The inner side of the reversible magnet abuts against the bottom surface of the groove, and the outer side of the reversible magnet abuts against the magnetic conductor. The permanent magnets are arranged around the magnetic conductor, and the coils are wound around the side walls of the reversible magnets. The coils on adjacent reversible magnets are wound in opposite directions and the coils are connected end to end. The coils in the same groove are formed by winding a single wire. The source of the wire is connected to the current controller to form a closed circuit.

[0016] One side of the inner side and the outer side of the reversible magnet is the N pole, and the other side is the S pole. The magnetic pole directions of two adjacent reversible magnets in the same groove are opposite. One end of the top and the bottom of the permanent magnet is the N pole, and the other end is the S pole. The contact ends of the multiple permanent magnets in contact with the same magnetic conductor have the same polarity. One permanent magnet is shared between two adjacent magnetic conductors.

[0017] The magnetic component has two different working states. In the first working state, the magnetic circuit formed by the permanent magnet and the reversible magnet passes through the sheet material. In the second working state, the permanent magnet and the reversible magnet form a magnetic circuit inside the punch. The magnetic attraction force is controlled by the current and the shape of the permanent magnet:

[0018] The magnetic field intensity at a certain position with different permanent magnet shapes is calculated according to the following formula:

[0019]

[0020] In the formula, B r is the remanence of the neodymium iron boron permanent magnet, with the unit of T; x is the distance between the position to be calculated and the center point of the permanent magnet, with the unit of m; L, W, and H are the length, width, and height of the permanent magnet respectively.

[0021] The control component includes a displacement sensor, a host computer, and a current controller that are electrically connected in sequence. The displacement sensor is used to detect the displacement change of the punch and send the punch displacement change signal to the host computer. The host computer sends a control signal to the current controller according to the punch displacement change. The current controller controls the working state of the magnetic component by controlling the direction of the current applied and controls the magnetic force of the magnetic component by adjusting the magnitude of the current applied to the coils. The coils in different grooves are connected in parallel, and multiple current controllers can respectively regulate the working states of the magnetic components in different grooves.

[0022] Preferably, a wire hole is formed on the punch body, and the wire passes through the wire hole to connect the coil with the current controller.

[0023] Preferably, a threaded hole is formed in the groove, a threaded through-hole identical to that in the groove is formed between the magnetic conductor and the permanent magnet, the magnetic conductor and the permanent magnet are connected together by a set screw and fixed to the punch body, and the remaining space in the groove is filled with epoxy resin.

[0024] Preferably, the punch body and the magnetic conductor are made of steel, the permanent magnet is made of hard magnetic material, the reversible magnet is made of soft magnetic material, and the coil is a copper coil.

[0025] Preferably, the input end of the current controller is connected to an external power supply.

[0026] Preferably, the upper template, the punch fixing plate, the lower template and the die are all provided with cylindrical pin holes, and the upper template and the punch fixing plate as well as the lower template and the die are positioned by cylindrical pins.

[0027] Preferably, the upper template and the punch fixing plate are provided with through-holes for the limiting member to pass through, and the blank holder has corresponding threaded holes.

[0028] Preferably, the permanent magnet and the reversible magnet are both of cuboid structure, and the cross-sectional shape of the magnetic conductor is rectangular or fan-shaped corresponding to different punch shapes.

[0029] Preferably, the displacement sensor is installed on the side wall of the punch body.

[0030] On the other hand, the present invention also provides a forming method based on the above forming device, specifically including the following steps:

[0031] S1. When the slider of the press drives the upper template and the punch to move downward, the blank holder synchronously moves downward with the upper template under the action of gravity and the spring. When the blank holder contacts the sheet blank, the position of the blank holder is locked. As the slider of the press continues to move downward, the spring compresses, and the blank holding force of the blank holder on the sheet material gradually increases.

[0032] S2. As the slider of the press moves downward, the punch contacts the sheet material, and the drawing forming of the sheet blank begins. When the displacement sensor detects that the drawing height exceeds the sum of the radii of the punch and die fillets, a short-time pulsed current is passed through the coil by the current controller, and the magnetic assembly is in the magnetized state to generate a magnetic suction force on the sheet material, increasing the frictional force between the sheet material and the punch.

[0033] S3. In the magnetized state of the magnetic assembly, the punch continues to move downward until a formed part meeting the requirements is obtained, and the forming process ends. A short-time reverse pulsed current is passed through the coil to make the magnetic assembly change to the demagnetized state and no longer generate a magnetic suction force on the sheet material.

[0034] S4. The slider of the press drives the punch to move upward. During the slow release process of the spring, the blank holder still applies a certain blank holding force to the formed part, separating the formed part from the punch. As the slider of the press continues to rise, the blank holder rises together until it returns to its original position, and the formed part is taken out, ending the deep drawing process.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) The magnetic components of the present invention are all placed in the grooves of the punch body, making the overall device structure compact and occupying a small area. At the same time, the outer side surface of the magnetic conductor is flush with the side surface of the punch body, and is filled with epoxy resin, maintaining the surface flatness of the punch, reducing the deformation amount of the punch, and enhancing the overall stiffness of the punch.

[0037] (2) The present invention increases the friction force between the sheet metal and the punch through the magnetic suction force generated by the magnetic components, reduces the maximum tensile stress received by the sheet metal at the intersection of the straight wall area and the bottom fillet area of the straight wall type formed part, reduces the risk of cracking, improves the forming limit of the sheet metal, and optimizes the overall performance of the formed part.

[0038] (3) The present invention controls the generation and elimination of the magnetic suction force of the magnetic components on the blank by passing a short - time pulsed current through the coil, and the operation is simple. And the power - on time is short, generating less heat, having the characteristics of energy conservation and environmental protection, and being more in line with green industrial production.

[0039] (4) The present invention can control the magnitude of the magnetic suction force received by the sheet metal by controlling the magnitude of the current through the current controller, and further control the magnitude of the friction force between the sheet metal and the punch, and can control different coils separately to ensure the control accuracy.

[0040] (5) The present invention has a wide application range and acts on ferromagnetic sheet metals, and can be applied in a variety of industrial scenarios. Description of the Drawings

[0041] Figure 1 is the overall structural schematic diagram of the forming device for improving the deep - drawing forming limit of ferromagnetic sheet metals of the present invention;

[0042] Figure 2 is the full - sectional view of the punch of the present invention;

[0043] Figure 3 is the state diagram of the sheet metal when receiving the magnetic suction force of the present invention;

[0044] Figure 4 is the state diagram of the sheet metal when not receiving the magnetic suction force of the present invention;

[0045] Figure 5 is the control schematic block diagram of the present invention;

[0046] Figure 6This is a simplified structural diagram of the punch body of the present invention.

[0047] Explanation of reference numerals in the drawings: 1 - upper template; 2 - limiting member; 3 - punch fixing plate; 4 - spring; 5 - guide bushing; 6 - punch; 7 - blank holder; 8 - blank; 9 - die; 10 - countersunk head bolt; 11 - cylindrical pin; 12 - guide post; 13 - lower template; 14 - displacement sensor; 15 - host computer; 16 - current controller; 601 - punch body; 602 - epoxy resin; 603 - permanent magnet; 604 - magnetic conductor; 605 - set screw; 606 - reversible magnet; 607 - coil; 608 - first wire hole; 609 - second wire hole; 610 - threaded hole. Detailed implementation manners

[0048] Hereinafter, the implementation manners of the present invention will be described with reference to the drawings.

[0049] As Figures 1 to 6 shown, on the one hand, the present invention provides a forming device for improving the drawing forming limit of ferromagnetic sheet materials, including an upper template 1, a punch fixing plate 3, a guide bushing 5, a punch 6, a blank holder 7, a die 9, a guide post 12 and a lower template 13. The blank holder 7 is connected to the upper template 1 through a limiting member 2 and can move up and down together with the upper template 1. The limiting member 2 can be a limiting screw or a limiting bolt. The guide bushing 5 is fixed on the upper template 1 by interference fit, the guide post 12 is fixed to the lower template 13 by interference fit, and the guide post 12 and the guide bushing 5 are in clearance fit for guiding the upper template 1 and the lower template 13 during the drawing process. The die 9 is fixed to the lower template through a countersunk head bolt 10, and the two are positioned by a cylindrical pin 11. The punch 6 is fixed to the upper template 1 through a punch fixing plate 3. The punch fixing plate 3 is connected to the upper template 1 by bolts and positioned by cylindrical pins. The spring 4 is placed in the groove between the punch fixing plate 3 and the blank holder 7, and the blank holding force is provided by the compression of the spring 4 during the drawing process.

[0050] The magnitude of the blank holding force is calculated according to the following formula:

[0051]

[0052]

[0053]

[0054] In the formula, Q is the blank holding force, and the unit is N; U θ is the deformation energy released by the circumferential elongation stress of the blank, and the unit is J; U ω is the deformation force required for the blank to bend when it buckles and wrinkles, and the unit is J; R0 is the initial radius of the blank, and the unit is mm; k μ is the blank holding force coefficient; y mis the wrinkling height, with the unit of mm; t is the slab thickness, with the unit of mm; is the central angle corresponding to a single wave; R ω is the radius of the flange outer edge, with the unit of mm; r0 is the radius at the entrance of the female die, with the unit of mm; is the central angle corresponding to any arc segment in a single wave; is related to a related function; ρ is the radial coordinate, with the unit of mm; σ θ is the circumferential stress, with the unit of MPa; n is the hardening index; B is the strength coefficient, with the unit of MPa; ε is the strain.

[0055] such as Figure 2 and Figure 6 As shown in

[0056] a groove is provided on the punch body 601, and the magnetic component is placed in the groove. The magnetic component includes a permanent magnet 603, a magnetic conductor 604, a reversible magnet 606, and a coil 607. In this embodiment, the reversible magnet 606 is made of a soft magnetic material. Based on the fact that soft magnetic materials are easily magnetized, the angle of the magnetic pole can be rotated under different current intensities, thus showing different magnetisms and magnetic forces.

[0057] such as Figure 5 As shown in

[0058] The displacement sensor 14 is installed outside the punch body 601 and is electrically connected to the host computer 15 and the current controller 16 in sequence. The coil 607 is connected to the current controller through a wire. The coils in the same groove are connected in series, and the coils in different grooves are connected in parallel, so that the current controller 16 can separately control the working state of the magnetic component in a certain groove.

[0059] The magnetic attraction force is provided by a permanent magnet instead of an electromagnet. By passing a short - time pulsed current through the coil, the pole direction of the reversible magnet can be changed, and then the external magnetic field state of the permanent magnet can be changed, thus determining whether the sheet metal is subjected to the magnetic attraction force. When the magnetic attraction force does not need to change, there is no need to continuously supply current, so there is no problem of losing magnetism when the power is cut off, which is safe and reliable and does not continuously generate heat.

[0060] Both the current and the shape of the permanent magnet can precisely control the magnetic attraction force. The magnetic attraction force is controlled by the current and the shape of the permanent magnet as follows:

[0061] The magnetic field intensity at a certain position of different permanent magnet shapes is calculated according to the following formula:

[0062]

[0063] In the formula, B r is the remanence of the neodymium - iron - boron permanent magnet, with the unit of T; x is the distance between the position to be calculated and the center point of the permanent magnet, with the unit of m; L, W, and H are the length, width, and height of the permanent magnet respectively.

[0064] The working principles of the magnetic component and the control component are further described below:

[0065] Working principle of the magnetic component:

[0066] In the present invention, the permanent magnet 603 has stable magnetism and is basically not affected by the external magnetic field; the pole direction of the reversible permanent magnet 606 is easily changed under the influence of the external magnetic field.

[0067] As Figure 4 shown, it is the working state of the magnetic component in the initial state. When the current controller 16 passes a short - time pulsed current into the coil 607, the coil 607 generates an instantaneous electromagnetic field, which can change the pole direction of the reversible magnet 606. When its pole direction changes to Figure 3 shown, the permanent magnet 603 forms a closed magnetic circuit by itself, and the adjacent reversible magnets 606 form a closed magnetic circuit. Both magnetic circuits pass through the sheet metal, and the sheet metal is subjected to the magnetic attraction force. The magnitude of the magnetic attraction force can be adjusted by the magnitude of the current passing through the coil. When the magnetic attraction force is not needed, the current controller 16 passes a short - time reverse pulsed current into the coil 607, and the coil 607 generates an instantaneous reverse electromagnetic field. The pole direction of the reversible magnet 606 changes to Figure 4 shown. At this time, the permanent magnet 603 and the reversible magnet 606 form a closed magnetic circuit inside the punch 6, and the magnetic lines of force no longer pass through the sheet metal, so the sheet metal is no longer subjected to the magnetic attraction force. The current in the coil only exists when changing the working state of the magnetic component and does not need to be continuously energized, so there is no danger of overheating of the coil.

[0068] Working principle of the control component:

[0069] As shown Figure 5 The displacement sensor 14 is arranged on the right side of the punch body 601. The displacement of the punch can be obtained at any time through the displacement sensor, and the forming height of the slab 8 can be known according to the displacement.

[0070] When the deep drawing process starts, the displacement sensor 14 continuously transmits the displacement condition of the punch to the host computer 15. In the embodiment, the host computer 15 can be a computer or an industrial control computer. Program parameters are built in the host computer 15, and the forming height of the slab is continuously analyzed. When the forming height reaches the specified threshold, the host computer 15 sends an instruction to the current controller 16, and the current controller passes a corresponding current into the coil 607 to make the magnetic component generate a corresponding magnetic field. The host computer 15 continues to receive the signals transmitted by the displacement sensor 14. When the punch 6 reaches the specified forming height, the host computer 15 sends an instruction to the current controller 16 again, and the current controller 16 passes a reverse pulse current into the coil 607 to change the working state of the magnetic component, so that the sheet material is no longer subjected to magnetic suction force.

[0071] On the other hand, the present invention also provides a forming method based on the above-mentioned forming device for improving the deep drawing forming limit of ferromagnetic sheet materials, which specifically includes the following steps:

[0072] S1. The slider of the press drives the upper template 1 and the punch 6 to move downward. The blank holder 7 moves downward synchronously with the upper template 1 under the action of gravity and the spring 4. When the blank holder 7 contacts the slab 8, the position of the blank holder 7 no longer changes. As the slider of the press continues to move downward, the spring 4 is gradually compressed, and the blank holding force of the blank holder 7 on the sheet material gradually increases.

[0073] S2. The slider of the press continues to move downward, and the punch 6 contacts the slab 8, and starts to deep draw the slab. Due to the existence of the fillets of the punch and die, the magnetic suction force provided by the magnetic component does not work in the initial stage. When the displacement sensor 14 detects that the drawing height exceeds the sum of the fillet radii of the punch and die, a short-time pulse current is passed into the coil 607 through the current controller 16, and the magnetic component is in a magnetized state, generating a magnetic suction force on the sheet material and increasing the friction force between the sheet material and the punch.

[0074] S3. Under the magnetized state of the magnetic component, the punch 6 continues to move downward until a formed part that meets the requirements is obtained, and the forming process ends. At this time, a short-time reverse pulse current is passed into the coil 607, and the magnetic poles of the reversible magnet 606 change, so that the working state of the magnetic component changes to a demagnetized state and no longer generates a magnetic suction force on the sheet material.

[0075] S4. The press slider drives the punch 6 to move upward. Since the spring 4 will not release suddenly, the blank holder 7 still applies a certain blank holding force to the formed part, separating the formed part from the punch. As the press slider continues to rise, the blank holder 7 rises together until it resets. The formed part is taken out, and the drawing process ends.

[0076] Embodiment 1

[0077] In this embodiment, the numbers of the magnetic conductor 604, the set screw 605, the reversible magnet 606, and the coil 607 are all 8, and the number of the permanent magnet 602 is 28. It should be noted that the numbers of the permanent magnet 603, the magnetic conductor 604, the set screw 605, the reversible magnet 606, and the coil 607 are not limited to 8 or 28. In the specific use process, the specific numbers are adjusted according to the size of the punch body 601.

[0078] Install the whole device according to Figure 1 、 Figure 2 and Figure 5 shown. Before the short-time pulse current is applied, the magnetic field state is as shown in Figure 4 shown. At this time, the magnetic component does not show magnetic force externally, and the sheet metal is not affected by the magnetic attraction force. Then, a short-time pulse current is applied to the coil by using the current controller to generate an instantaneous magnetic field, changing the pole direction of the reversible magnet, as shown in Figure 3 shown. At this time, the magnetic component shows magnetic force externally, and the sheet metal is affected by the magnetic force. At this time, the friction force between the sheet metal and the punch increases. When the punch continues to move downward to a specified depth, the current controller applies a reverse short-time pulse current to the coil, and the coil generates an instantaneous magnetic field again, changing the pole direction of the reversible magnet again. At this time, the magnetic field state is as shown in Figure 4 shown. The workpiece is no longer affected by the magnetic force. The punch is separated from the formed part, the punch resets, and the drawing ends.

[0079] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A forming device for improving the drawing forming limit of ferromagnetic sheet materials, characterized in that: It includes an upper template, a lower template, a punch, a punch fixing plate, a spring, a blank holder, a die, a guide bushing, a guide pillar, a limiting member, a displacement sensor and a current controller; The punch is fixed at the middle position of the upper template through the punch fixing plate. A limiting member is arranged on each side of the upper template. The blank holder is connected to the upper template by means of the limiting member and can move up and down with the upper template. Grooves for placing springs are provided on both the punch fixing plate and the blank holder. The die is fixed at the middle position of the lower template by countersunk head bolts, and a sheet blank is placed on the upper surface of the die; The upper template is connected with the guide bushing by interference fit, and the lower template is connected with the guide pillar by interference fit. The guide bushing and the guide pillar cooperate with each other, and the upper template and the lower template are positioned by means of the guide bushing and the guide pillar; The limiting member limits the blank holder after the blank holder contacts the sheet material. The spring is compressed as the distance between the punch fixing plate and the blank holder decreases during the drawing process, providing a blank holding force for the blank holder; The magnitude of the required blank holding force is calculated according to the following formula: Wherein, Q is the blank holding force, with the unit of N; U θ is the deformation energy released by the circumferential elongation stress of the slab, with the unit of J; U ω is the deformation force required for bending when the slab buckles and wrinkles, with the unit of J; R0 is the initial radius of the slab, with the unit of mm; k μ is the blank holding force coefficient; y m is the wrinkling height, with the unit of mm; t is the thickness of the slab, with the unit of mm; is the central angle corresponding to a single wave; R ω is the radius of the outer edge of the flange, with the unit of mm; r0 is the radius at the entrance of the die, with the unit of mm; is the central angle corresponding to any arc segment in a single wave; is related to the function; ρ is the radial coordinate, with the unit of mm; σ θ is the circumferential stress, with the unit of MPa; n is the hardening index; B is the strength coefficient, with the unit of MPa; ε is the strain; The punch includes a punch body, a magnetic component and a control component. Grooves are provided on the straight wall surface of the punch body, and a magnetic component is arranged in the grooves; the magnetic component includes a plurality of permanent magnets, a plurality of magnetic conductors, a plurality of reversible magnets and a plurality of coils. The inner side of the reversible magnet abuts against the bottom surface of the groove, and the outer side of the reversible magnet abuts against the magnetic conductor; the permanent magnets are arranged around the magnetic conductor, and the coils are wound around the side wall of the reversible magnet; the coils on adjacent reversible magnets are wound in opposite directions and the coils are connected end to end, and the coils in the same groove are formed by winding a single wire; the source of the wire is connected to the current controller belonging to it to form a closed loop; One side of the inner side and the outer side of the reversible magnet is an N pole, and the other side is an S pole. The magnetic pole directions of adjacent two reversible magnets in the same groove are opposite. One end of the top and the bottom of the permanent magnet is an N pole, and the other end is an S pole. The contact ends of the plurality of permanent magnets contacting the same magnetic conductor have the same polarity; a single permanent magnet is shared between adjacent two magnetic conductors; The magnetic component includes two different working states. In the first working state, the magnetic circuit formed by the permanent magnet and the reversible magnet passes through the sheet material. In the second working state, the permanent magnet and the reversible magnet form a magnetic circuit inside the punch; the magnetic suction force is controlled by the current and the shape of the permanent magnet: The magnetic field intensity at a certain position of different permanent magnet shapes is calculated according to the following formula: where B r is the remanence of the NdFeB permanent magnet, with the unit of T; x is the distance between the position to be determined and the center point of the permanent magnet, with the unit of m; L, W, and H are the length, width, and height of the permanent magnet, respectively; The control component includes a displacement sensor, a host computer and a current controller which are electrically connected in sequence. The displacement sensor is used to detect the change of the punch displacement; The current controller controls the working state of the magnetic component by controlling the direction of the current passed through and controls the magnetic force of the magnetic component by adjusting the magnitude of the current passed through the coil; the coils in different grooves are connected in parallel, and a plurality of current controllers can respectively control the working states of the magnetic components in different grooves.

2. The forming device for improving the drawing forming limit of ferromagnetic sheet materials according to claim 1, characterized in that: A wire hole is provided on the punch body, and a wire passes through the wire hole to connect the coil with the current controller.

3. The forming device for improving the drawing forming limit of ferromagnetic sheet materials according to claim 2, characterized in that: A threaded hole is formed in the groove. A threaded through-hole identical to that in the groove is formed between the magnetic conductor and the permanent magnet. The magnetic conductor and the permanent magnet are connected together by a set screw and fixed to the punch body. The remaining space in the groove is filled with epoxy resin.

4. The forming device for improving the drawing forming limit of ferromagnetic sheet materials according to claim 1, characterized in that: The punch body and the magnetic conductor are made of steel. The permanent magnet is made of a hard magnetic material. The reversible magnet is made of a soft magnetic material. The coil is a copper coil.

5. The forming device for improving the drawing forming limit of ferromagnetic sheet materials according to claim 1, characterized in that: The input end of the current controller is connected to an external power supply.

6. The forming device for improving the drawing forming limit of ferromagnetic sheet materials according to claim 1, characterized in that: The upper template, the punch fixing plate, the lower template, and the die are all provided with cylindrical pin holes. The upper template and the punch fixing plate, as well as the lower template and the die, are positioned by cylindrical pins.

7. The forming device for improving the drawing forming limit of ferromagnetic sheet materials according to claim 6, characterized in that: The upper template and the punch fixing plate are provided with through-holes through which the limiting member passes. The blank holder has corresponding threaded holes.

8. The forming device for improving the drawing forming limit of ferromagnetic sheet materials according to claim 1, characterized in that: Both the permanent magnet and the reversible magnet are in a cuboid structure. The cross-sectional shape of the magnetic conductor is rectangular or fan-shaped.

9. The forming device for improving the drawing forming limit of ferromagnetic sheet materials according to claim 1, characterized in that: The displacement sensor is installed on the side wall of the punch body.

10. A forming method of a forming device for improving the drawing forming limit of a ferromagnetic sheet according to claim 1, characterized in that: Specifically, it includes the following steps: S1. When the slider of the press drives the upper template and the punch to move downward, the blank holder moves downward synchronously with the upper template under the action of gravity and the spring. When the blank holder contacts the sheet blank, the position of the blank holder is locked. As the slider of the press continues to move downward, the spring compresses, and the blank holding force of the blank holder on the sheet material gradually increases. S2. As the slider of the press moves downward, the punch contacts the sheet material, and the drawing forming of the sheet blank begins. When the displacement sensor detects that the drawing height exceeds the sum of the radii of the punch and die fillets, a short-time pulsed current is passed through the coil by the current controller, and the magnetic assembly is in a magnetized state to generate a magnetic suction force on the sheet material, increasing the friction force between the sheet material and the punch. S3. In the magnetized state of the magnetic assembly, the punch continues to move downward until a formed part that meets the requirements is obtained, and the forming process ends. A short-time reverse pulsed current is passed through the coil to make the magnetic assembly change to a demagnetized state and no longer generate a magnetic suction force on the sheet material. S4. The slider of the press drives the punch to move upward. During the slow release of the spring, the blank holder still has a certain blank holding force on the formed part, causing the formed part to separate from the punch. As the slider of the press continues to rise, the blank holder rises together until it returns to its original position, and the formed part is taken out to end the drawing.

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