Punching device and punching method with controllable forming force and blank holding force

Abstract

The present invention provides a punching device and a punching method with controllable forming force and blanking force, which include a punch, a punching die, an upper die base, a lower die base, a guide post, a guide sleeve, a magnetic upper die pressing plate, a magnetic lower die punching plate, a fixed attracted plate, a punch, a discharge spring, a positioning pin and a magnetic pad. The guide post is sequentially connected to the magnetic lower die punching plate, the fixed attracted plate and the magnetic upper die pressing plate. The lower die base is connected to the fixed attracted plate by means of a positioning pin. The magnetic upper die pressing plate is placed on the fixed attracted plate by means of a discharge spring. The punch is fixedly connected to the lower die punching plate. During operation, the magnetic induction intensity of the soft magnet is controlled by a coil, thereby controlling the magnetic attraction force and controlling the forming force and the blanking force. The punching device of the present invention does not require power and transmission devices, has a simple structure, high reliability, low noise and is pollution-free. During the punching process, the magnetic force generated by the hard magnet can be used to provide the forming force, and the blanking force can be precisely adjusted during the blanking process.

Description

Technical Field

[0001] The present invention relates to the fields of electric-controlled permanent magnet technology and punching technology, and in particular to a punching device and a punching method with controllable forming force and blank holding force. Background Art

[0002] Depending on the deformation properties of the sheet metal, stamping processes can be divided into separation processes and bulk forming processes. Punching, as one of the primary separation processes, typically involves a punch or die contacting the sheet metal at a certain speed, separating the sheet metal, and thereby producing a hole of the desired shape and size. With the rapid advancement of industrial technology, production equipment is gradually becoming smaller and more precise. Compared to drilling, punched holes have high surface quality and are scratch-free, leading to their widespread application in thin sheet metal forming. Punching equipment is gradually developing towards larger bright bands, higher punching accuracy, and a burr-free design, meeting the precision forming requirements of modern industrial technology.

[0003] During the actual punching process, sheet metal deformation behavior is complex, involving highly nonlinear factors such as elasticity, plasticity, and fracture. Consequently, research on the punching process is somewhat constrained. The localized and transient nature of the fracture deformation zone also complicates research and process optimization. Consequently, engineers are eager to explore new punching methods and optimize the punching process.

[0004] Currently, the publicly available punching equipment uses hydraulic equipment to provide the blanking force and forming force. The equipment is large in size, complex in structure, and difficult to disassemble and repair, making it difficult to meet the requirements of miniaturization and precision. Summary of the Invention

[0005] In order to solve the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a punching device and a punching method with controllable forming force and blank holding force, which uses permanent magnetic force as the blank holding force and forming force to punch thin plates. The punching accuracy is high, the equipment is lighter, the cost is lower, the operation is convenient and the transportation is convenient.

[0006] Specifically, the present invention provides a punching device with controllable forming force and blank holding force based on electromagnetic permanent control technology, which includes a punch, a punching die, an upper die base, a lower die base, a guide column, a guide sleeve, a magnetic upper die pressing plate, a magnetic lower die punching plate, a fixed attracted plate, a punch, a discharge spring, a positioning pin and a magnetic pad, wherein the guide column is sequentially connected to the magnetic lower die punching plate, the fixed attracted plate and the magnetic upper die pressing plate, the lower die base is connected to the fixed attracted plate by means of the positioning pin, the magnetic upper die pressing plate is placed on the fixed attracted plate by means of the discharge spring, and the punch is fixedly connected to the lower die punching plate;

[0007] The upper die base and the lower die base are respectively provided with guide post holes, and the upper die base and the lower die base are fixedly connected with the guide posts by means of the guide post holes to form a punching device frame;

[0008] The magnetic lower die punching plate is connected to the punch, the magnetic upper die pressing plate is connected to the punching die, and the fixed sucked plate is provided with a through hole for the punch to pass through;

[0009] The magnetic pad includes a magnetic upper die pressing plate magnetic pad and a magnetic lower die punching plate magnetic pad. The fixed attracted plate is placed between the magnetic upper die pressing plate magnetic pad and the magnetic lower die punching plate magnetic pad. After being magnetized by the power controller, it can provide a blanking force and a punching force respectively.

[0010] The magnetic pad includes a plurality of magnetic pole units, and the magnetic poles of adjacent magnetic pole units are in opposite directions; each group of magnetic pole units includes eight hard magnets, one soft magnet, two conductive magnets and two magnetic coils, the top and bottom of the soft magnets are in contact with the conductive magnets respectively, the side of the soft magnets is wrapped by the magnetic coils, the side of the conductive magnets is in contact with the hard magnets, and the tops of the conductive magnets of adjacent magnetic pole units are in contact with each other;

[0011] When powered on and magnetized, the electromagnetic and hard magnetic circuits of the magnetic pad are superimposed on each other, and the coil magnetizes the soft magnet so that the pole directions of the soft magnet and the hard magnet are consistent. The magnetic lines of force of the two magnetic fields start from the N pole, pass through the air domain and the fixed attracted plate, and then return to the S pole to form a closed magnetic circuit. During this process, the fixed attracted plate is magnetized and generates a corresponding magnetic attraction. Under the action of the magnetic attraction generated by the magnetic pad, the fixed attracted plate moves upward and fits into the magnetic pad;

[0012] When the power is turned off and demagnetized, the electromagnetic field of the magnetic pad and the magnetic circuit of the hard magnet repel and cancel each other out. The coil magnetizes the soft magnet and makes the magnetic poles of the soft magnet and the hard magnet opposite to each other. The magnetic lines of force of the two magnetic fields start from the N pole, pass through the hard magnet, reach the adjacent magnetic pole unit, and then return to the S pole to form a closed magnetic circuit. The magnetic circuit does not pass through the fixed attracted plate, and no magnetic attraction is generated. The magnetic pad is separated from the fixed attracted plate.

[0013] During operation, the magnetic induction intensity of the soft magnet is controlled by the coil, thereby controlling the magnetic attraction force, and controlling the forming force and the blank holding force. The magnetic attraction force of the attracted plate is calculated according to the following formula:

[0014]

[0015] Where F is the magnetic attraction of the magnetic pad to the attracted plate, in N; μ0 is the magnetic permeability of vacuum; B r1 is the remanence of hard magnets, unit is T; B r2 is the remanence of the soft magnet, in T; k2 is the frequency of the magnetic flux lines of the soft magnet; d2 is the thickness of the soft magnet, in mm; a is the effective length of the magnetic pad, in mm; b is the effective width of the magnetic pad, in mm.

[0016] Preferably, the magnetic lower die punching plate is provided with a circular groove, and the circular groove is connected to a plurality of punches via a plurality of countersunk bolts.

[0017] Preferably, the magnetic upper die pressing plate is provided with a stepped hole, and the stepped hole is used to install a variety of punching dies to take out the material after the punching is completed. The through hole opened by the fixed suction plate is a cylindrical through hole.

[0018] Preferably, the fixed sucked plate is provided with a groove for placing the thin plate material.

[0019] Preferably, the magnetic pad is embedded in the magnetic upper die pressing plate and the magnetic lower die punching plate and connected through epoxy resin, a non-magnetic material; the magnetic pad is fixedly bonded to the magnetic template through epoxy resin.

[0020] Preferably, the permanent magnetic force generated after magnetization between the magnetic upper die pressing plate and the fixed attracted plate is used as the edge holding force; the permanent magnetic force generated after magnetization between the magnetic lower die punching plate and the fixed attracted plate is used as the punching force.

[0021] Preferably, an upper magnetic pad and a lower magnetic pad are provided on the upper surface and the lower surface of the fixed attracted plate respectively.

[0022] Preferably, the punching force and the blank holding force provided by the magnetic pad can be adjusted in stages according to the number of magnetic pole unit groups or can be adjusted steplessly by adjusting the magnetic coil current according to the power controller.

[0023] Preferably, the hard magnet is a neodymium iron boron hard magnet, the magnetic conductor is a pure iron magnetic conductor, and the soft magnet is an aluminum nickel cobalt soft magnet.

[0024] Preferably, in another aspect, the present invention provides a method for punching according to the punching device with controllable forming force and blank holding force based on electromagnetic permanent control technology, which comprises the following steps:

[0025] S1. When the punching device is in operation, the punching frame composed of the upper die base, the lower die base and the guide pillar is stationary. The sheet material is placed in the groove of the fixed suction plate. The power controller magnetizes the magnetic pad of the magnetic upper die pressing plate. The magnetic upper die pressing plate attracts the fixed suction plate to fit it, completing the pressing step. Under the action of gravity, the fixed suction plate is supported by the positioning pins.

[0026] S2. After the pressing is completed, the power controller magnetizes the magnetic pad of the magnetic lower die punching plate, and the magnetic lower die punching plate attracts and fixes the attracted plate to fit, and the punch connected to the magnetic lower die punching plate moves upward, cooperating with the punching die connected to the magnetic upper die pressing plate to complete the blanking. After punching, the thin plate material is separated into sheets with circular holes and blanks with circular or other shaped contours, and the blanks are taken out from the stepped through holes of the magnetic upper die pressing plate;

[0027] S3. After the punching is completed, the power controller demagnetizes the magnetic pad of the magnetic lower die punching plate. Under the action of gravity, the magnetic lower die punching plate descends to the upper surface of the lower die base. The punch connected to the magnetic lower die punching plate is located below the punched sheet.

[0028] S4. After the magnetic pad of the magnetic lower die punching plate is demagnetized, the power controller demagnetizes the magnetic pad of the magnetic upper die pressing plate. The unloading spring offsets the gravity of the magnetic upper die pressing plate. Under the action of the elastic force, the magnetic upper die pressing plate moves upward and separates from the fixed attracted plate, unloading the edge holding force. At this time, the sheet with holes can be taken out from the groove of the fixed attracted plate.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The punching device of the present invention does not require power and transmission devices, has a simple structure, high reliability, low noise and no pollution. During the punching process, the magnetic force generated by the hard magnet can be used to provide the forming force, and the blanking force can be accurately adjusted during the blanking process.

[0031] (2) Permanent magnetic force is used as the blanking force and forming force to punch thin plates. The punching accuracy is high, the equipment is lighter, the cost is lower, the operation is convenient and the transportation is convenient.

[0032] (3) When the device of the present invention is in operation, the magnetic upper die pressing plate moves downward to provide the required edge clamping force for the thin plate material, and then the magnetic lower die punching plate moves upward to drive the punch to punch, and the punched material is taken out through the through hole on the magnetic upper die pressing plate. After the punching is completed, the magnetic lower die punching plate moves downward to the lower die seat position, and the magnetic upper die pressing plate moves upward to the upper die seat position to unload the edge clamping force and take out the thin plate parts with holes. At this time, the punching and unloading steps are completed, and at the same time, the punching device returns to its initial state and waits for the next punching. The entire punching step is flexible and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the front view of the present invention;

[0034] Figure 2 A schematic diagram of the magnetic pole unit structure of the present invention;

[0035] Figure 3 Schematic diagram of the working magnetic pole of the AlNiCo hard magnet of the present invention.

[0036] Figure 4 This is a schematic diagram of the magnetization principle of the magnetic pad of the present invention.

[0037] Figure 5 This is a diagram showing the demagnetization principle of the magnetic pad of the present invention.

[0038] 1-upper die base, 2-punching die, 3-fixing bolt, 4-magnetic upper die pressing plate magnetic pad, 5-guide sleeve, 6-magnetic upper die pressing plate, 7-fixed suction plate, 8-unloading spring, 9-punch, 10-magnetic lower die punching plate magnetic pad, 11-locating pin, 12-magnetic lower die punching plate, 13-guide column, 14-lower die base;

[0039] 15-NdFeB hard magnet, 16-pure iron magnetic conductor, 17-AlNiCo soft magnet, 18-magnetic coil;

[0040] 19-punch hole, 20-magnetic pole unit, 21-magnetic lower die punching plate body, 22-unloading spring hole, 23-guide sleeve hole. DETAILED DESCRIPTION

[0041] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0042] The present invention provides a punching device with controllable forming force and blank holding force, such as Figure 1 As shown, it includes an upper die base 1, a lower die base 14, a punching die 2, a discharge spring 8, a punch 9, a magnetic lower die punching plate magnetic pad 10, and a positioning pin 11. The upper die base 1 and the lower die base 14 are respectively provided with a guide column 13. The upper die base 1 is fixedly connected to the lower die base 14 through the guide column 13, the punching die 2 is connected to the magnetic upper die pressing plate 6 through the fixing bolt 3, the punch 9 is connected to the magnetic lower die punching plate 12 through the fixing bolt 3, the magnetic upper die pressing plate 6 is connected to the fixed attracted plate 7 through the discharge spring 8, the positioning pin 11 passes through the magnetic lower die punching plate 12, connects the magnetic lower die punching plate 12 and the lower die base 14, and fixes the fixed attracted plate 7. The magnetic lower die punching plate 12 and the magnetic upper die pressing plate 6 are respectively connected to the fixed attracted plate by the magnetic force provided by the magnetic upper die pressing plate magnetic pad 4 and the magnetic lower die punching plate magnetic pad 10. The guide pillars 13 are respectively connected to the magnetic lower die punching plate 12, the magnetic upper die pressing plate 6 and the fixed sucked plate 7 through the guide sleeves 5.

[0043] The magnetic lower die punching plate 12 includes a magnetic lower die punching plate magnetic pad 10 and a magnetic lower die punching plate body 21 with a punch hole 19, a discharge spring hole 22 and a guide sleeve hole 23. The magnetic upper die pressing plate magnetic pad 4 and the magnetic lower die punching plate magnetic pad 10 both include multiple magnetic pole units 20 with opposite magnetic pole directions. The magnetic pole unit 20 includes a neodymium iron boron hard magnet 15, a pure iron magnet 16, an aluminum nickel cobalt soft magnet 17 and a magnetic coil 18.

[0044] When powered on and magnetized, the electromagnetic and permanent magnetic circuits of the magnetic pad are superimposed on each other, and the coil magnetizes the soft magnet, making the pole directions of the soft magnet and the hard magnet consistent. The magnetic lines of force of the two magnetic fields start from the N pole, pass through the air domain and the fixed attracted plate, and then return to the S pole to form a closed magnetic circuit. In this process, the fixed attracted plate is magnetized and generates corresponding magnetic attraction. Under the action of the magnetic attraction generated by the magnetic pad, the fixed attracted plate moves upward and fits into the magnetic pad;

[0045] When the power is turned off and demagnetized, the electromagnetic and permanent magnetic circuits of the magnetic pad repel and cancel each other out. The coil magnetizes the soft magnet and makes the magnetic pole directions of the soft magnet and the hard magnet opposite. The magnetic lines of force of the two magnetic fields start from the N pole, pass through the hard magnet, reach the adjacent magnetic pole unit, and then return to the S pole to form a closed magnetic circuit. The magnetic circuit does not pass through the fixed attracted plate, no magnetic attraction is generated, and the magnetic pad is separated from the fixed attracted plate.

[0046] During operation, the coil controls the magnetic induction intensity of the soft magnet, thereby controlling the magnetic attraction force, and thus the forming force and blank holding force. The coil current is directly applied through the power controller, whose input voltage is 380V and the output current can be adjusted steplessly within ±40A. The coil current and magnetic attraction exhibit a clear nonlinear relationship. The control current must be determined based on the required magnetic attraction force and the hysteresis curve of the soft magnet. The magnetic pad can be charged and demagnetized within 20 milliseconds of power on to achieve energy saving. The demagnetization current is constant at 20A, at which time the magnetic pad leakage can be ignored and no magnetism is shown to the outside.

[0047] The magnetic attraction force is calculated according to the following formula:

[0048]

[0049] Where F is the magnetic attraction of the magnetic pad to the attracted plate, in N; μ0 is the magnetic permeability of vacuum; B r1 is the remanence of hard magnets, unit is T; B r2 is the remanence of the soft magnet, in T; k2 is the frequency of the magnetic flux lines of the soft magnet; d2 is the thickness of the soft magnet, in mm; a is the effective length of the magnetic pad, in mm; b is the effective width of the magnetic pad, in mm.

[0050] The above formula is obtained by integrating the magnetic field strength on the attracted plate.

[0051] Among them, the magnetic field intensities corresponding to the magnetization vectors of the hard magnet in the Z direction are:

[0052]

[0053] The magnetic field intensity corresponding to the magnetization vector of the soft magnetic body in the Z direction is:

[0054] H z3 =M2 cosk2y(1-e -k2d2 )e-k2h

[0055] Wherein, M1 is the initial magnetization intensity of the hard magnet, in A / m; k1 is the frequency of the magnetic flux lines of the hard magnet; d1 is the thickness of the hard magnet, in mm; h is the air gap between the magnetic pad and the attracted plate, in mm; x is the horizontal axis coordinate; y is the vertical axis coordinate; H Z1 is the magnetization intensity component in the horizontal axis direction, with the unit being A / m; H Z2 is the magnetization intensity component in the longitudinal direction, in A / m; H Z3 is the magnetic field intensity corresponding to the magnetization vector of the soft magnet in the Z direction. M2 is the initial magnetization intensity of the soft magnet, in A / m; k2 is the frequency of the magnetic flux lines of the soft magnet; d2 is the thickness of the soft magnet;

[0056] According to the magnetic field strength corresponding to the magnetization vectors of the hard magnet and the soft magnet in the Z direction, the magnetic induction intensity inside the attracted plate is obtained as follows:

[0057] B Z1 =2μ0h Z1

[0058] B z2 =2μ0h z2

[0059] B Z3 =2μ0h z3

[0060] Then calculate the total magnetic induction intensity inside the attracted plate:

[0061] B0=B Z1 +B Z2 +B Z3

[0062] According to the magnetic field formula and virtual displacement method, the calculation formula of the magnetic attraction force of the attracted plate is obtained and integrated:

[0063]

[0064] Example 1

[0065] In this embodiment, only two magnetic pads are provided, namely the magnetic upper die pressing plate magnetic pad 4 and the magnetic lower die punching plate magnetic pad 10 .

[0066] In this embodiment, when the punching device is in operation, the punching frame composed of the upper die base 1, the lower die base 14 and the guide pillar 13 is stationary, the sheet material is placed in the groove of the fixed attracted plate 7, the power controller magnetizes the magnetic upper die pressing plate magnetic pad 4 of the magnetic upper die pressing plate 6, the magnetic upper die pressing plate 6 attracts the fixed attracted plate 7 to fit tightly, completing the pressing step, under the action of gravity, the fixed attracted plate 7 is supported by the positioning pin 11. Figure 1After the pressing step is completed, the power controller magnetizes the magnetic lower die punching plate magnetic pad 10 of the magnetic lower die punching plate 12, and the magnetic lower die punching plate 12 attracts and fixes the attracted plate 7 to fit tightly. The punch 9 connected to the magnetic lower die punching plate 12 moves upward, and cooperates with the punching die 3 connected to the magnetic upper die pressing plate 6 to complete the blanking. After punching, the thin plate material is separated into plates with circular holes and blanks with circular or other shaped contours. The blanks can be taken out from the stepped through holes processed by the magnetic upper die pressing plate 6. After the blanking is completed, the power controller demagnetizes the magnetic lower die punching plate magnetic pad 10 of the magnetic lower die punching plate 12. Under the action of gravity, the magnetic lower die punching plate 12 descends to the upper surface of the lower die base 14. At this time, the punch 9 connected to the magnetic lower die punching plate 12 is located below the plate after the punching is completed. There is no restriction on the horizontal position of the plate, which is convenient for the next unloading operation. After the magnetic lower die punching plate magnetic pad 10 of the magnetic lower die punching plate 12 is demagnetized, the power controller demagnetizes the magnetic pad of the magnetic upper die pressing plate 6, and the unloading spring 8 offsets the gravity of the magnetic upper die pressing plate 6. Under the action of the elastic force, the magnetic upper die pressing plate 6 moves upward and separates from the fixed attracted plate 7, unloading the clamping force. At this time, the sheet material with holes can be taken out from the groove of the fixed attracted plate 7. At this point, the feeding, punching and material removal steps of the thin plate material have been completed and explained. The punching device also returns to the initial state after punching, which is convenient for the next punching operation.

[0067] Example 2

[0068] In this embodiment, in addition to the magnetic pad 4 of the upper magnetic die pressing plate and the magnetic pad 10 of the lower magnetic die punching plate, an upper magnetic pad and a lower magnetic pad are also provided on the fixed attracted plate 7 .

[0069] When the four magnetic pads of the punching device are simultaneously involved in punching, the thin plate material is placed in the groove of the fixed attracted plate 7. The power controller magnetizes the magnetic upper die pressing plate magnetic pad 4 of the magnetic upper die pressing plate 6 and the upper magnetic pad of the fixed attracted plate 7 at the same time. The magnetic upper die pressing plate 6 and the fixed attracted plate 7 are tightly fitted to each other to complete the pressing step. Under the action of gravity, the fixed attracted plate 7 is supported by the positioning pin 11. Figure 1As shown, after the pressing step is completed, the power controller magnetizes the magnetic lower die punching plate magnetic pad 10 of the magnetic lower die punching plate 12 and the upper magnetic pad of the fixed attracted plate. The magnetic lower die punching plate 12 and the fixed attracted plate 7 attract each other and fit tightly together. The punch 9 connected to the magnetic lower die punching plate 12 moves upward and cooperates with the punching die 3 connected to the magnetic upper die pressing plate 6 to complete the blanking. After punching, the thin plate material is separated into a sheet with a circular hole and a blank with a circular or other shape contour. The blank can be taken out from the stepped through hole processed by the magnetic upper die pressing plate 6. After the blanking is completed, the power controller demagnetizes the magnetic lower die punching plate magnetic pad 10 of the magnetic lower die punching plate 12 and the lower magnetic pad of the fixed attracted plate 7. Under the action of gravity, the magnetic lower die punching plate 12 descends to the upper surface of the lower die base 14. At this time, the punch 9 connected to the magnetic lower die punching plate 12 is located below the sheet after the punching is completed. There is no restriction on the horizontal position of the sheet, which is convenient for the next unloading operation. After the magnetic lower die punching plate magnetic pad 10 of the magnetic lower die punching plate 12 is demagnetized, the power controller demagnetizes the magnetic pad of the magnetic upper die pressing plate 6 and the upper magnetic pad of the fixed attracted plate 7. The unloading spring 8 offsets the gravity of the magnetic upper die pressing plate 6. Under the action of the elastic force, the magnetic upper die pressing plate 6 moves upward and separates from the fixed attracted plate 7, unloading the blanking force. At this time, the sheet with holes can be taken out from the groove of the fixed attracted plate 7. Compared with the double magnetic pad punching in Example 1, the forming force generated by the four magnetic pad device is much greater than that of the double magnetic pad punching device. The punching force and the blanking force can be adjusted over a wide range directly by the number of magnetic pole units of the magnetic pad, and can also be adjusted by adjusting the excitation current.

[0070] like Figure 2 and Figure 4 As shown, the magnetic pad includes a NdFeB hard magnet 15, a pure iron magnetic conductor 16, an AlNiCo soft magnet 17, and a magnetic coil 18. The hard magnet is a permanent magnet, while the soft magnet is a reversible magnet. The AlNiCo soft magnet 17 is in contact with the magnetic conductor 16 at its top and bottom, and its sides are wrapped by the magnetic coil. The sides of the magnetic conductor 16 are in contact with the NdFeB hard magnet 15, and the tops of the two magnetic pads are in contact with each other to reduce magnetic flux leakage. When magnetizing, a positive current is passed through the magnetic coil 18, and the magnetic pole direction of the aluminum nickel cobalt soft magnet 17 is the same as the magnetic pole direction of the upper neodymium iron boron hard magnet 15. The magnetic lines of force pass through the upper air domain to reach the adjacent magnetic pole unit, while the magnetic pole direction of the aluminum nickel cobalt soft magnet 17 is opposite to the magnetic pole direction of the lower neodymium iron boron hard magnet 15. The magnetic lines of force directly pass through the lower neodymium iron boron hard magnet 15 to reach the adjacent magnetic pole unit. As a whole, the upper side of the magnetic pad exhibits magnetic force, and the lower side has no magnetic force.

[0071] like Figures 2 to 5As shown, when demagnetization occurs, a reverse current is passed through the magnetic coil 18, and the magnetic pole direction of the AlNiCo soft magnet 17 is opposite to that of the upper NdFeB hard magnet 15. The magnetic lines of force pass through the upper NdFeB hard magnet 15 to reach the adjacent magnetic pole unit, while the magnetic pole direction of the AlNiCo soft magnet 17 is the same as that of the lower NdFeB hard magnet 15. The magnetic lines of force pass through the lower air space to reach the adjacent magnetic pole unit. As a whole, the lower side of the magnetic pad exhibits magnetic force, and the upper side has no magnetic force.

[0072] During operation, the magnetic induction intensity of the AlNiCo magnet is controlled by the coil, thereby controlling the magnetic attraction force and thus controlling the forming force and the blank holding force.

[0073] Contact area S of magnetic pad g The working current and punching gap play a decisive role in the magnitude of the magnetic attraction force. In order to ensure the adjustability of the blanking force in actual operation, the magnetic pad is reasonably designed to ensure a constant punching gap. g It is mainly determined by the magnetic field generated by AlNiCo magnets and NdFeB magnets. The magnetic induction intensity of NdFeB hard magnets generally does not change, so the magnetic induction intensity of AlNiCo magnets has a great influence on B g The size plays a decisive role.

[0074] When the magnetization is powered on, ignoring the magnetic circuit leakage, the magnetic attraction of the magnetic pad to the attracted plate is related to the magnitude of the magnetic induction intensity vector in the Z direction. The magnetic field intensities corresponding to the magnetization vector of the hard magnet in the Z direction are:

[0075]

[0076] The remanence of the magnet can be precisely controlled by adjusting the coil current according to the AlNiCo hysteresis curve, and the magnetic attraction can be calculated according to the following formula:

[0077]

[0078] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A punching device with controllable forming force and blank holding force, characterized in that: It includes a punch, a punching die, an upper die base, a lower die base, a guide column, a guide sleeve, a magnetic upper die pressing plate, a magnetic lower die punching plate, a fixed attracted plate, a punch, a discharge spring, a positioning pin and a magnetic pad. The guide column is sequentially connected to the magnetic lower die punching plate, the fixed attracted plate and the magnetic upper die pressing plate. The lower die base is connected to the fixed attracted plate by means of the positioning pin. The magnetic upper die pressing plate is placed on the fixed attracted plate by means of the discharge spring. The punch is fixedly connected to the lower die punching plate. The upper die base and the lower die base are respectively provided with guide post holes, and the upper die base and the lower die base are fixedly connected with the guide posts by means of the guide post holes to form a punching device frame; The magnetic lower die punching plate is connected to the punch, the magnetic upper die pressing plate is connected to the punching die, and the fixed sucked plate is provided with a through hole for the punch to pass through; The magnetic pad includes a magnetic upper die pressing plate magnetic pad and a magnetic lower die punching plate magnetic pad. The fixed attracted plate is placed between the magnetic upper die pressing plate magnetic pad and the magnetic lower die punching plate magnetic pad. After being magnetized by a power controller, it can provide a blanking force and a punching force respectively. The magnetic pad includes a plurality of magnetic pole units, and the magnetic poles of adjacent magnetic pole units are in opposite directions; each group of magnetic pole units includes eight hard magnets, one soft magnet, two conductive magnets and two magnetic coils, the top and bottom of the soft magnets are in contact with the conductive magnets respectively, the side of the soft magnets is wrapped by the magnetic coils, the side of the conductive magnets is in contact with the hard magnets, and the tops of the conductive magnets of adjacent magnetic pole units are in contact with each other; When powered on and magnetized, the electromagnetic and hard magnetic circuits of the magnetic pad are superimposed on each other, and the coil magnetizes the soft magnet so that the pole directions of the soft magnet and the hard magnet are consistent. The magnetic lines of force of the two magnetic fields start from the N pole, pass through the air domain and the fixed attracted plate, and then return to the S pole to form a closed magnetic circuit. During this process, the fixed attracted plate is magnetized and generates a corresponding magnetic attraction. Under the action of the magnetic attraction generated by the magnetic pad, the fixed attracted plate moves upward and fits into the magnetic pad; When the power is turned off and demagnetized, the electromagnetic field of the magnetic pad and the magnetic circuit of the hard magnet repel and cancel each other out. The coil magnetizes the soft magnet and makes the magnetic poles of the soft magnet and the hard magnet opposite to each other. The magnetic lines of force of the two magnetic fields start from the N pole, pass through the hard magnet, reach the adjacent magnetic pole unit, and then return to the S pole to form a closed magnetic circuit. The magnetic circuit does not pass through the fixed attracted plate, and no magnetic attraction is generated. The magnetic pad is separated from the fixed attracted plate. During operation, the magnetic induction intensity of the soft magnet is controlled by the coil, thereby controlling the magnetic attraction force, and controlling the forming force and the blank holding force. The magnitude of the magnetic attraction force is calculated according to the following formula: Where F is the magnetic attraction of the magnetic pad to the attracted plate, in N; μ0 is the magnetic permeability of vacuum; B r1 is the remanence of hard magnets, unit is T; B r2 is the remanence of the soft magnet, in T; k2 is the frequency of the magnetic flux lines of the soft magnet; d2 is the thickness of the soft magnet, in mm; a is the effective length of the magnetic pad, in mm; b is the effective width of the magnetic pad, in mm.

2. The punching device with controllable forming force and blank holding force according to claim 1, characterized in that: The magnetic lower die punching plate is provided with a circular groove, and the circular groove is connected to a plurality of punches through a plurality of countersunk bolts.

3. The punching device with controllable forming force and blank holding force according to claim 1, characterized in that: The magnetic upper die pressing plate is provided with a stepped hole, and the stepped hole is used to install a variety of punching dies to take out the material after the punching is completed. The through hole opened by the fixed suction plate is a cylindrical through hole.

4. The punching device with controllable forming force and blank holding force according to claim 1, characterized in that: The fixed sucked plate is provided with a groove for placing the thin plate material.

5. The punching device with controllable forming force and blank holding force according to claim 1, characterized in that: The magnetic pad is embedded in the magnetic upper die pressing plate and the magnetic lower die punching plate and connected by epoxy resin.

6. The punching device with controllable forming force and blank holding force according to claim 1, characterized in that: The permanent magnetic force generated after magnetization between the magnetic upper mold pressing plate and the fixed attracted plate serves as the blank holding force; The permanent magnetic force generated after magnetization between the magnetic lower die punching plate and the fixed attracted plate serves as the punching force.

7. The punching device with controllable forming force and blank holding force according to claim 1, characterized in that: An upper magnetic pad and a lower magnetic pad are respectively provided on the upper surface and the lower surface of the fixed attracted plate.

8. The punching device with controllable forming force and blank holding force according to claim 1, characterized in that: The punching force and the blank holding force provided by the magnetic pad can be adjusted in stages according to the number of magnetic pole unit groups or can be adjusted steplessly by adjusting the magnetic coil current by a power controller.

9. The punching device with controllable forming force and blank holding force according to claim 1, characterized in that: The hard magnet is a neodymium iron boron hard magnet, the magnetic conductor is a pure iron magnetic conductor, and the soft magnet is an aluminum nickel cobalt soft magnet.

10. A method for punching using the punching device with controllable forming force and blank holding force according to claim 1, characterized in that: It includes the following steps: S1. When the punching device is in operation, the punching frame composed of the upper die base, the lower die base and the guide pillar is stationary. The sheet material is placed in the groove of the fixed suction plate. The power controller magnetizes the magnetic pad of the magnetic upper die pressing plate. The magnetic upper die pressing plate attracts the fixed suction plate to fit it, completing the pressing step. Under the action of gravity, the fixed suction plate is supported by the positioning pins. S2. After the pressing is completed, the power controller magnetizes the magnetic pad of the magnetic lower die punching plate, and the magnetic lower die punching plate attracts and fixes the attracted plate to fit, and the punch connected to the magnetic lower die punching plate moves upward, cooperating with the punching die connected to the magnetic upper die pressing plate to complete the blanking. After punching, the thin plate material is separated into sheet materials with holes and blanks with circular or other shapes, and the blanks are taken out from the stepped through holes of the magnetic upper die pressing plate; S3. After the punching is completed, the power controller demagnetizes the magnetic pad of the magnetic lower die punching plate. Under the action of gravity, the magnetic lower die punching plate descends to the upper surface of the lower die base. The punch connected to the magnetic lower die punching plate is located below the punched sheet. S4. After the magnetic pad of the magnetic lower die punching plate is demagnetized, the power controller demagnetizes the magnetic pad of the magnetic upper die pressing plate. The unloading spring offsets the gravity of the magnetic upper die pressing plate. Under the action of the elastic force, the magnetic upper die pressing plate moves upward and separates from the fixed attracted plate, unloading the edge holding force. At this time, the sheet with holes can be taken out from the groove of the fixed attracted plate.

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