DEVICE AND METHOD OF COIL-LESS ELECTROMAGNETIC PULSE INCREMENTAL FORMING FOR METAL SHEET

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Chinese patent application No. CN202411430208.7, filed to China National Intellectual Property Administration (CNIPA) on Oct. 14, 2024, which is herein incorporated by reference in its entirety.

TECHNICAL FIELD

The disclosure relates to the field of material plastic forming technologies, and particularly to a device and a method of coil-less electromagnetic pulse incremental forming for a metal sheet.

BACKGROUND

Electromagnetic pulse forming technology has demonstrated significant advantages in material processing. The electromagnetic pulse forming technology can effectively increase forming limit of materials and is characterized by fast forming speed, high forming accuracy, precise control, and strong versatility of equipment. Additionally, during a process of the electromagnetic pulse forming technology, it does not produce pollution, thus it has been widely applied in various fields such as machinery, electronics, automotive industry, light industry and chemical industry, instrumentation, aerospace, and armaments, showing broad application prospects.

Traditional electromagnetic pulse forming processes are mainly targeted at high-conductivity materials such as aluminum sheets. A working principle is shown in FIG. 1: a power supply system is connected to coils, and a sheet to be formed is placed between the coils and a mold. When a pulse current passes through the coils, a first electromagnetic field is generated, which induces a current in the sheet to be formed, thereby forming a second electromagnetic field. A repulsive force between the first and second electromagnetic fields causes the sheet to be formed to deform. However, this method is less effective for ferromagnetic materials with low magnetic permeability. Therefore, the traditional electromagnetic pulse forming processes are mainly applied to high-conductivity materials such as aluminum and copper, while the forming of low-conductivity materials, such as steel and titanium alloys, or non-metallic materials cannot be achieved with the existing coil structure due to insufficient electromagnetic forming force.

In a design of the coils, discharge coils, as the key component that converts electrical energy into magnetic field energy, determine a magnetic field distribution and forming results of the workpiece. However, during the electromagnetic pulse forming processes, the coils are subject to effects of electromagnetic reaction force and current thermal effects, making them prone to damage and requiring the coils to have high strength and durability. Especially in a multi-turn coil structure, a high manufacturing cost of coils, a difficulty in ensuring dimensional stability and requirements for multiple discharges greatly limit the application of the electromagnetic pulse forming processes in mass production.

To overcome these limitations, a coil-less electromagnetic pulse forming process is proposed to replace the traditional discharge coils with an induction plate, effectively solving the problems of high cost and short lifespan of the discharge coils. In addition, by using a self-resistance heating forming of the sheet, low-conductivity materials can be directly processed. By selecting appropriate voltage and current to heat the sheet according to the process requirements, the resistance heat generated can locally soften the material, reduce the yield strength, and decrease the forming force. However, when forming large, complex, or repetitive structured workpieces, the coil-less electromagnetic pulse forming process requires a design of large and complex molds and induction plates, resulting in a long production cycle, high cost, and lack of flexibility, with high technical difficulty and expensive costs.

A sheet metal incremental forming technology is mainly used for processing large and complex sheet parts. By introducing a concept of layered manufacturing from a rapid prototyping technology, an overall forming of complex three-dimensional sheet metal parts is decomposed into a series of two-dimensional local plastic forming. Multiple small deformations accumulate to form a large deformation, thereby reducing a forming difficulty and an energy consumption. However, this process has problems with low forming accuracy and poor surface quality.

Based on the above technical problems, the disclosure provides a device and a method of coil-less electromagnetic pulse incremental forming for a metal sheet.

SUMMARY

The disclosure provides a device of coil-less electromagnetic pulse incremental forming for a metal sheet and a method thereof to solve the problems in the related art.

To achieve above purpose, the technical solutions of the disclosure are as follows.

A device of coil-less electromagnetic pulse incremental forming for a metal sheet includes a lathe, a three-axis moving frame, a sheet clamping table, a mold, a discharging component, a power supply system, and a control cabinet. A worktable is disposed on a top of the lathe. The three-axis moving frame is disposed on a top of the worktable, and an induction block is disposed on the three-axis moving frame. The sheet clamping table is disposed on the top of the worktable and is located below the three-axis moving frame, a sheet to be formed is clamped on the sheet clamping table, and the sheet to be formed is correspondingly arranged with the induction block. The mold is mounted on a top surface of the worktable, the mold is located below the sheet to be formed and correspondingly arranged with the induction block. The discharging component includes first discharging contactors and second discharging contactors, the first discharging contactors are disposed on the three-axis moving frame, and the second discharging contactors are disposed on the sheet clamping table. The first discharging contactors and the second discharging contactors are correspondingly arranged with the sheet to be formed. The power supply system is electrically connected to the first discharging contactors or the second discharging contactors. The control cabinet is signal-connected to both the three-axis moving frame and the power supply system, and the control cabinet is electrically connected to an input module. The first discharging contactors or the second discharging contactors are connected to the power supply system through conductors, and a circuit breaker is disposed on the conductor between

• • each second discharging contact and the power supply system.

In an embodiment, the three-axis moving frame includes an X-axis linear motor, a Y-axis linear motor, and a Z-axis telescopic rod. Two sides of the worktable are fixedly connected to two fixing frames, respectively. The X-axis linear motor is fixed at top ends of the two fixing frames, the Y-axis linear motor is disposed on a horizontal line of the X-axis linear motor, the Z-axis telescopic rod is disposed on a horizontal line of the Y-axis linear motor, and the induction block is disposed on the Z-axis telescopic rod.

In an embodiment, the top surface of the worktable is fixedly connected to a busbar, and the busbar is electrically connected to the power supply system. The first discharging contactors and the second discharging contactors are all electrically connected to the busbar through the conductors.

In an embodiment, a top end of the induction block is fixedly connected to an insulating block, a buffer spring is fixedly connected on the insulating block, and the buffer spring is fixed at an end of the Z-axis telescopic rod.

In an embodiment, the first discharging contactors include conformal contactors, and the conformal contactors are fixed on the insulating block. The conformal contactors are in contact with the sheet to be formed, the conformal contactor is electrically connected to the busbar through the conductors and is capable of being deformed in accordance with the sheet to be formed.

In an embodiment, the second discharging contactors include multiple sets of pneumatic contactors, and the multiple sets of pneumatic contactors are circumferentially arranged on the sheet clamping table. The multiple sets of pneumatic contactors are in contact with the sheet to be formed and are connected to the busbars through the conductors.

In an embodiment, a positioning fixture is mounted on the top surface of the worktable, and the mold is removably connected to the positioning fixture.

In an embodiment, the power supply system includes a direct current (DC) power source, an energy storage capacitor, a voltage dividing resistor (also referred to as divider resistor), and a control switch. The DC power source is configured to charge the energy storage capacitor, the voltage dividing resistor is configured to control a charging voltage of the energy storage capacitor, and the energy storage capacitor is electrically connected to the busbars.

A method of coil-less electromagnetic pulse incremental forming for the metal sheet using the device mention above includes the steps as follows.

• • S1: the mold is fixed on the top surface of the worktable, then the sheet to be formed is clamped on the sheet clamping table, and the induction block is clamped on the three-axis moving frame.
  • S2: a sheet shape is imported into the control cabinet through the input module, and a processing route of the sheet to be formed is preset through the control cabinet.
  • S3: whether the power supply system is connected to the first discharging contactors or the second discharging contactors is determined. In response to the power supply system being connected to the first discharging contactors, S4 and S6 are proceeded. In response to the power supply system being connected to the second discharging contactors, S5 and S6 are proceeded.
  • S4: the control cabinet controls the three-axis moving frame to drive the induction block to move at a preset position. The device is charged through the power supply system, when a charging voltage reaches a forming voltage, the power supply system is disconnected, then a charging circuit is broken and the discharging circuit is connected. The first discharging contactors discharge to form an instantaneous current, followed by generating a local current and a strong magnetic field on the sheet to be formed through the instantaneous current, and simultaneously generating an induction current and an induction electromagnetic field on the induction block through the instantaneous current. The sheet to be formed is shaped under an action of a magnetic field force, followed by adjusting a processing position of the three-axis moving frame again and repeating the S4 to achieve an incremental forming of the sheet to be formed.
  • S5: the control cabinet controls the three-axis moving frame to drive the induction block to move at a preset position. The device is charged through the power supply system, when a charging voltage reaches a forming voltage, the power supply system is disconnected, then the charging circuit is broken and the discharging circuit is connected. The circuit breakers on the second discharging contactors respectively corresponding to the processing position are turned off, then the second discharging contactor discharges to form an instantaneous current, followed by generating a local current and a strong magnetic field on the sheet to be formed through the instantaneous current, and simultaneously generating an induction current and an induction electromagnetic field on the induction block through the instantaneous current. The sheet to be formed is shaped under the action of the magnetic field force, followed by turning on the circuit breakers, adjusting the processing position of the three-axis moving frame again and repeating the S5 to achieve the incremental forming of the sheet to be formed.
  • S6: a formed sheet and the mold are removed to replace another mold and another sheet to be formed, and a next processing is proceeded.

The beneficial effects of the disclosure are as follows.

• • 1. The disclosure combines coil-less electromagnetic pulse forming and incremental forming processes, which can directly and efficiently form large and complex parts made of low-conductivity materials.
  • 2. The disclosure adopts an idea of layered and zoned forming. It can complete the forming of complex parts with a simple structure of the induction block, and it also improves the strength and lifespan of the induction block.

The mold of the disclosure is simple and easy to install, facilitating manufacturing and reducing production costs. By simply replacing different molds, different workpieces can be processed, thus the application scope of the disclosure is extensive.

During a forming process of the disclosure, an energized area can be controlled by the opening and closing of the circuit breakers, enabling local energization and avoiding a need to energize an entire sheet to be formed each time. This significantly reduces energy loss and makes production more sustainable.

BRIEF DESCRIPTION OF DRAWINGS

In order to more clearly illustrate the embodiments of the disclosure or the technical solutions in the related art, a brief introduction will be given to the attached drawings required for the embodiments. It is apparent that the attached drawings described below are only some embodiments of the disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative labor.

FIG. 1 illustrates a principal diagram of traditional electromagnetic pulse forming.

FIG. 2 illustrates a structural schematic diagram of a worktable in the disclosure.

FIG. 3. illustrates a schematic diagram of a device of coil-less electromagnetic pulse incremental forming with first discharging contactors in the disclosure.

FIG. 4 illustrates a schematic diagram of another device of coil-less electromagnetic pulse incremental forming with second discharging contactors in the disclosure.

FIG. 5 illustrates an overall structural schematic diagram of the another device of coil-less electromagnetic pulse incremental forming with the second discharging contactors in the disclosure.

Description of reference signs:

• • 1. mold; 2. sheet to be formed; 3. lathe; 4. control cabinet; 5. power supply system; 6. worktable; 7. three-axis moving frame; 8. buffer spring; 9. insulating block; 10. induction block; 11. pneumatic contactor; 12. conductor; 13. circuit breaker; 14. busbar; 15. positioning fixture; 16. conformal contactor; 17. fixing frame; 18. sheet clamping table; 5-1. DC power source; 5-2. energy storage capacitor; 5-3. voltage dividing resistor; 5-4. control switch; 7-1. X-axis linear motor; 7-2. Y-axis linear motor; 7-3. Z-axis telescopic rod; 111. first discharging contactor; 112. second discharging contactor.

DETAILED DESCRIPTION OF EMBODIMENTS

The disclosure will provide a clear and complete description of the technical solution in the embodiments of the disclosure, in conjunction with the attached drawings. Apparently, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary skilled persons in the art without creative labor are within the scope of protection of the present invention.

In order to make the above objectives, features, and advantages of the disclosure clearer and more understandable, the following will provide further detailed explanations of the disclosure in conjunction with the attached drawings and specific embodiments.

As shown in FIGS. 1-5, a device of coil-less electromagnetic pulse incremental forming for a metal sheet includes a lathe 3, a three-axis moving frame 7, a sheet clamping table 18, a mold 1, a discharging component, a power supply system 5, and a control cabinet 4. A worktable 6 is disposed on a top of the lathe 3. The three-axis moving frame 7 is disposed on a top of the worktable 6, and an induction block 10 is disposed on the three-axis moving frame 7. The sheet clamping table 18 is disposed on the top of the worktable 6 and is located below the three-axis moving frame 7, a sheet to be formed 2 is clamped on the sheet clamping table 18, and the sheet to be formed 2 is correspondingly arranged with the induction block 10. The mold 1 is mounted on a top surface of the worktable 6, the mold 1 is located below the sheet to be formed 2 and correspondingly arranged with the induction block 10. The discharging component includes first discharging contactors 111 or second discharging contactors 112. As shown in FIGS. 1-3, the discharging component only includes the first discharging contactors 111, and as shown in FIGS. 1-2 and 4-5, the discharging component only includes the second discharging contactors 112. In a specific embodiment, the discharging component includes both the first discharging contactors 111 and the second discharging contactors 112, which is not shown in the drawings. The first discharging contactors 111 are disposed on the three-axis moving frame 7, and the second discharging contactors 112 are disposed on the sheet clamping table 18. The first discharging contactors 111 and the second discharging contactors 112 are correspondingly arranged with the sheet to be formed 2. The power supply system 5 is electrically connected to the first discharging contactors 111 or the second discharging contactors 112. The control cabinet 4 is signal-connected to both the three-axis moving frame 7 and the power supply system 5, and the control cabinet 4 is electrically connected to an input module. The first discharging contactors 111 or the second discharging contactors 112 are connected to the power supply system 5 through conductors 12, and a circuit breaker 13 is disposed on the conductor 12 between each second discharging contactor 112 and the power supply system 5.

The mold 1 is a concave or convex mold.

In an embodiment, the three-axis moving frame 7 includes an X-axis linear motor 7-1, a Y-axis linear motor 7-1, and a Z-axis telescopic rod 7-3. Two sides of the worktable 6 are fixedly connected to two fixing frames 17, respectively. The X-axis linear motor 7-1 is fixed at top ends of the two fixing frames 17, the Y-axis linear motor 7-2 is disposed on a horizontal line of the X-axis linear motor 7-1, the Z-axis telescopic rod 7-3 is disposed on a horizontal line of the Y-axis linear motor 7-2, and the induction block 10 is disposed on the Z-axis telescopic rod 7-3.

In an embodiment, the top surface of the worktable 6 is fixedly connected to busbar 14, and the busbar 14 is electrically connected to the power supply system 5. The first discharging contactors 111 and the second discharging contactors 112 are all electrically connected to the busbar 14 through the conductors 12.

A movement along a three-axes is achieved through the X-axis linear motor 7-1, Y-axis linear motor 7-2, and Z-axis telescopic rod 7-3, which is used to move the induction block 10 disposed on the top of Z-axis telescopic rod 7-3. The combination of the X-axis linear motor 7-1, Y-axis linear motor 7-2, and Z-axis telescopic rod 7-3 enhances the flexibility of the device.

In an embodiment, a top end of the induction block 10 is fixedly connected to an insulating block 9, a buffer spring 8 is fixedly connected on the insulating block 9, and the buffer spring 8 is fixed at an end of the Z-axis telescopic rod.

The induction block 10 is made of high-conductivity material, which is used to generate an induced current and an induced magnetic field, and to produce a magnetic force to deform the sheet to be formed 2. The insulating block 9 is an epoxy block made of epoxy resin, connecting the induction block 10 and the Z-axis telescopic rod, and is used to isolate the induced current. The buffer spring 8 is used to reduce the vibration caused by an electromagnetic force and maintain a stability of the Z-axis telescopic rod.

In an embodiment, the first discharging contactors 111 include conformal contactors 16, and the conformal contactors 16 are fixed on the insulating block 9. The conformal contactors 16 are in contactor with the sheet to be formed 2, the conformal contactors 16 are electrically connected to the busbar 14 through the conductors 12 and is capable of being deformed in accordance with the sheet to be formed 2.

Materials of the conformal contactors 16 include: conductive rubber, conductive sponge, conductive foam, and conductive coating.

In an embodiment, the second discharging contactors 112 include multiple sets of pneumatic contactors 11, and the multiple sets of pneumatic contactors 11 are circumferentially arranged on the sheet clamping table 18. The multiple sets of pneumatic contactors 11 are in contactor with the sheet to be formed 2 and are connected to the busbar 14 through the conductors 12.

In an embodiment, a positioning fixture 15 is mounted on the top surface of the worktable 6, and the mold 1 is removably connected to the positioning fixture 15. The positioning fixture 15 utilizes either a pneumatic fixture or an electric fixture, thereby enabling automatic clamping of molds 1 of different sizes and enhancing the applicability of the device.

In an embodiment, the power supply system 5 includes a DC power source 5-1, an energy storage capacitor 5-2, a voltage dividing resistor 5-3, and a control switch 5-4. The DC power source 5-1 is configured to charge the energy storage capacitor 5-2, the voltage dividing resistor 5-3 is configured to control a charging voltage of the energy storage capacitor 5-2, and the energy storage capacitor 5-2 is electrically connected to the busbar 14.

A method of coil-less electromagnetic pulse incremental forming for the metal sheet using the device mentioned above include steps as follows.

• • S1: the mold 1 is fixed on the top surface of the worktable 6 through the positioning fixture, then the sheet to be formed 2 is clamped on the sheet clamping table 18. The pneumatic contactors 11 are used to secure the sheet to be formed 2 on the sheet clamping table 18, and the induction block 10 is clamped on the insulating block 9 at a bottom of the Z-axis telescopic rod.
  • S2: a sheet shape is imported into the control cabinet 4 through the input module, and a processing route of the sheet to be formed 2 is preset through the control cabinet 4.
  • S3: whether the power supply system 5 is connected to the first discharging contactors 111 or the second discharging contactors 112 is determined. In response to the power supply system 5 being connected to the first discharging contactors 111, S4 and S6 are proceeded. In response to the power supply system 5 being connected to the second discharging contactors 112, S5 and S6 are proceeded.
  • S4: the control cabinet 4 controls the X-axis linear motor 7-1, the Y-axis linear motor 7-2, and the Z-axis telescopic rod 7-3 to drive the induction block 10 to move at a preset position. After program retrieval, coordinates of the induction block 10 and the pneumatic contactor 11 are compared. The respectively corresponding circuit breakers 13 are closed to form an electrical circuit among the busbar 14, conductors 12, the circuit breakers 13, the pneumatic contactors 11, and the sheet to be formed 2. The control cabinet 4 controls the connection between the direct current (DC) power source and the energy storage capacitor. Once a charging voltage reaches a forming voltage, the charging circuit is disconnected. Subsequently, the circuit breakers 13 corresponding to the pneumatic contactors 11 at a respective position is opened, and an instantaneous current passes through the busbar 14 and the pneumatic contactors 11, thereby generating a local current and a strong magnetic field on the sheet to be formed 2. At the same time, an induction current and an induction electromagnetic field are generated on the induction block 10. The sheet to be formed 2 is shaped under the action of the magnetic field force, the discharge switch is then opened. Afterwards, the device is moved to the next processing position using the X-axis linear motor 7-1, Y-axis linear motor 7-2, and Z-axis telescopic rod 7-3. This process is repeated until the sheet to be formed 2 is completely shaped, achieving the incremental forming of the sheet to be formed 2.
  • S5: the control cabinet 4 controls the three-axis moving frame 7 to drive the induction block 10 to move at a preset position. The device is charged through the power supply system 5, when a charging voltage reaches a forming voltage, the power supply system 5 is disconnected, then a charging circuit is broken and the discharging circuit is connected. The circuit breakers 13 on second discharging contactors 112 respectively corresponding to the processing position are turned off, then the second discharging contactors 112 10 discharges to form an instantaneous current, followed by generating a local current and a strong magnetic field on the sheet to be formed 2 through the instantaneous current, and simultaneously generating an induction current and an induction electromagnetic field on the induction block through the instantaneous current. The sheet to be formed 2 is shaped under the action of the magnetic field force, followed by turning on the circuit breakers 13, adjusting a processing position of the three-axis moving frame 7 again and repeating the S5 to achieve a incremental forming of the sheet to be formed 2.
  • S6: a formed sheet and the mold 1 are removed to replace another mold and another sheet to be formed 2, and a next processing is proceeded.

In the description of the disclosure, it should be understood that the terms “longitudinal”, “transverse”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside” and other directional or positional relationships indicated are based on the directional or positional relationships shown in the attached drawings, only for the convenience of describing the disclosure, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the disclosure.

The above embodiments are only a description of the specific embodiments of the disclosure and do not limit the scope of the disclosure. Without departing from the design spirit of the disclosure, various modifications and improvements made by those skilled in the art to the technical solution of the disclosure should fall within the scope of protection determined by the claims of the disclosure.