An incremental forming device and method based on magnetorheological elastomer auxiliary support

Abstract

The present invention discloses an incremental forming device and method based on magnetorheological elastomer auxiliary support, comprising a forming tool head, a clamping plate, a magnetorheological elastomer support, a magnetic field generating unit and its controller, and a detachable base mold. The base mold houses the magnetorheological elastomer support, and after the plate is clamped, it is tightly attached to the surface of the magnetorheological elastomer support. The base mold is provided with multiple cylindrical slots around its periphery for accommodating the magnetic field generating unit for exerting an effect on the magnetorheological elastomer. Under the control of the controller, the magnetic field generating unit changes the magnetic field and thereby changes the shear modulus of the magnetorheological elastomer support, thereby supporting the bottom surface of the formed plate. The present invention proposes a method for improving the forming accuracy of incrementally formed workpieces using a magnetorheological elastomer support. Specifically, the magnetorheological elastomer exerts a supporting force on the bottom of the plate, thereby reducing the rebound and associated deformation of the formed part and improving the forming performance of the part.

Description

Technical Field

[0001] The present invention belongs to the technical field of incremental forming auxiliary processing, and in particular relates to an incremental forming device and method based on magnetorheological elastomer auxiliary support. Background Art

[0002] The sheet metal incremental forming process is based on the layered manufacturing concept of rapid prototyping technology. The target part is formed by controlling the movement of the tool head along contour layers in three-dimensional space. It can be divided into positive forming and negative forming, depending on whether there is mold support at the bottom. In traditional negative forming, the back of the sheet metal is suspended in the air, and the sheet metal is formed unconstrained solely by the extrusion between the tool head and the sheet metal. Due to the strain concentration caused by excessive local stress, the sheet metal is prone to defects such as instability, springback, and extended deformation, which seriously affect the forming limit, precision, and surface quality.

[0003] Existing methods for assisting support in incremental forming mainly include hydraulically assisted support forming, vacuum assisted support forming, and the installation of follow-up supports and multi-point support devices under the sheet metal. Although the above-mentioned assisting support methods can effectively improve the forming performance of parts, they have certain limitations in forming complex surfaces with variable curvature due to the high requirements for external device assembly, the partial lack of rigid concave and convex support, and the inability to strictly control the sealing effect within the forming cavity. In addition, the existing bottom support devices often have poor support system flexibility and can only assist in forming specific sizes, shapes, and specific materials. Therefore, there is currently a lack of an assisting support method for incremental forming that is highly flexible, applicable to a wide range of processing, and easy to operate. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention proposes an incremental forming device and method based on magnetorheological elastomer auxiliary support.

[0005] The present invention is achieved through the following technical solutions:

[0006] A progressive forming device based on magnetorheological elastomer auxiliary support, comprising a forming tool head 1, a clamping plate 3, a magnetorheological elastic support body 2, a magnetic field generating unit 5 and its controller, and a detachable base mold 6. The forming tool head 1 is located above a plate, and the clamping plate 3 is located at the edge position above the plate, for fixing the plate on the base mold 6. The base mold 6 accommodates the magnetorheological elastic support body 2 inside, and the plate is tightly attached to the surface of the magnetorheological elastic support body 2 after clamping; a plurality of cylindrical slots are provided around the base mold 6 to place the magnetic field generating unit 5 for acting on the magnetorheological elastomer 2. The magnetic field generating unit 5 changes the magnetic field under the control of the controller and thereby changes the shear modulus of the magnetorheological elastic support body 2 to support the bottom surface of the formed plate.

[0007] The incremental forming device based on magnetorheological elastomer auxiliary support, the magnetic field generating unit (5) includes four electromagnet pairs: a first electromagnet (7) and a second electromagnet (10), a third electromagnet (14) and a fourth electromagnet (11), a fifth electromagnet (8) and a sixth electromagnet (13), and a seventh electromagnet (9) and an eighth electromagnet (12). Each pair of electromagnets generates a magnetic field of a certain magnitude when energized.

[0008] The progressive forming device based on magnetorheological elastomer auxiliary support, the base mold is a square structure, two cylindrical empty slots are set on each side, and a total of eight cylindrical empty slots are set for placing the four electromagnet pairs. The two electromagnets in each electromagnet pair are respectively set on two opposite sides of the base mold, and the positions of the two electromagnets correspond.

[0009] In the incremental forming device based on magnetorheological elastomer auxiliary support, each electromagnet includes a coil 15, a pole 16, and a pole head 17. After a DC power supply is connected to the electromagnet, the energized coil 15 can generate a magnetic field of a certain size. Under the action of the external coil 15, the ferromagnetic metal atoms inside the pole 16 are rearranged in a certain order to generate magnetism, forming a magnetic field between the two pole heads 17 of each pair of electromagnets.

[0010] The incremental forming device based on the auxiliary support of magnetorheological elastomer can form a controllable high-intensity magnetic field in the air gap between the two poles 17 of each pair of electromagnets by controlling the current passing through the coil 15.

[0011] In the incremental forming device based on magnetorheological elastomer auxiliary support, the controller controls the change of the induced current by predicting the forming quality of the metal sheet under different support forces based on simulation results, establishing the relationship between the processing depth Z and the support force under the optimal forming quality of the magnetorheological elastomer auxiliary support incremental forming, and then, through the relationship between the support force F generated by the change in the elastic body stiffness and the induced current I, the relationship between the processing depth Z and the induced current I can be obtained:

[0012]

[0013] F=kI+m,(k>0);

[0014]

[0015] An incremental forming method based on a magnetorheological elastomer auxiliary support, based on any of the aforementioned incremental forming devices based on a magnetorheological elastomer auxiliary support, comprises the following steps:

[0016] (1) Energize the electromagnetic coil of the magnetic field generating unit and clamp the plate with the clamping plate and the base mold;

[0017] (2) programming the machining trajectory of the target part to be machined, and inputting the forming trajectory into the external controller of the magnetic field generating unit structure;

[0018] (3) Turn on the forming tool head control switch, and control the forming tool head to process layer by layer along the preset trajectory through the program. Under the support of the magnetorheological elastomer at the bottom, the three-dimensional curved surface forming of the same sheet material with multiple changes in overall and local convex and concave angles can be achieved.

[0019] (4) As the processing depth increases, the controller controls the magnitude of the induced current of the magnetic field coil according to the change of the program trajectory parameter Z value, and then changes the support force of the magnetorheological elastomer on the sheet metal by adjusting the magnetic field size, ultimately achieving the required larger angle forming limit and forming the required complex curved surface part;

[0020] According to the method, the force exerted by the tool head and the bottom support on the sheet material is always consistent, and the extrusion state of the sheet material is constant.

[0021] According to the method, each time the tool head descends one level in processing, the magnetic field coil changes the magnitude of the induced current accordingly, thereby correspondingly reducing the support force of the magnetorheological elastomer on the sheet material, ensuring that the sheet material does not fail or rupture due to excessive stress concentration caused by uneven force within the forming limit.

[0022] The present invention achieves the following beneficial effects: A method for improving the forming accuracy of incrementally formed workpieces using a magnetorheological elastic support body is proposed. Specifically, the magnetorheological elastic body applies a supporting force to the bottom of the sheet, thereby reducing springback and associated deformation of the formed part and improving its forming performance. Furthermore, by varying the magnetic field and controlling the elasticity of the magnetorheological elastic body, a safe range of supporting force is maintained, ensuring smooth forming of deep parts and effectively expanding the formability range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the auxiliary support device for magnetorheological elastomer;

[0024] Figure 2 Schematic diagram of the magnetic field generating unit structure;

[0025] Figure 3 Schematic diagram of the pole structure;

[0026] Figure 4 、 5 Schematic diagram of the forming process;

[0027] Figure 6 It is a schematic diagram of the frustum parts;

[0028] Figure 7 Schematic diagram of the control points of the frustum trajectory;

[0029] The reference numerals in the figure are as follows: 1. forming tool head, 2. magnetorheological elastic support body, 3. clamping pressure plate, 4. pole structure, 5. magnetic field generating unit, 6. base mold, 7. first electromagnet, 8. fifth electromagnet, 9. seventh electromagnet, 10. second electromagnet, 11. fourth electromagnet, 12. eighth electromagnet, 13. sixth electromagnet, 14. third electromagnet, 15. induction coil, 16. pole, 17. pole head, 18. sheet material, 19. frustum part, 20 frustum trajectory control point. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to specific embodiments.

[0031] like Figure 1-7 As shown, a progressive forming device based on magnetorheological elastomer auxiliary support includes a forming tool head 1, a clamping pressure plate 3, a magnetorheological elastic support body 2, a magnetic field generating unit 5 and its controller, and a detachable base mold 6. The forming tool head 1 is located above the plate, and the clamping pressure plate 3 is located at the edge position above the plate, which is used to fix the plate on the base mold 6. The base mold 6 is provided with eight cylindrical slots to place the magnetic field generating unit 5 for acting on the magnetorheological elastomer 2. The magnetic field generating unit changes the magnetic field under the control of the controller and thereby changes the shear modulus of the magnetorheological elastic support body 2 to support the bottom surface of the formed plate.

[0032] Furthermore, the magnetic field generating unit 5 includes four pairs of electromagnets: a first electromagnet 7 and a second electromagnet 10, a third electromagnet 14 and a fourth electromagnet 11, a fifth electromagnet 8 and a sixth electromagnet 13, and a seventh electromagnet 9 and an eighth electromagnet 12. A magnetic field of a certain magnitude will be generated between each pair of electromagnets after power is applied. Each electromagnet includes a coil 15, a pole 16, and a pole head 17. After a DC power supply is applied to the electromagnet, the energized coil 15 can generate a magnetic field of a certain magnitude. Under the action of the external coil 15, the ferromagnetic metal atoms inside the pole 16 are rearranged in a certain order to generate magnetism, forming a magnetic field between the two pole heads 17 of each pair of electromagnets.

[0033] Furthermore, by controlling the current flowing through the coil 15, a controllable high-intensity magnetic field can be formed in the air gap between the two poles 17 of each pair of electromagnets. This magnetic field can then be controlled to vary the shear modulus of the magnetorheological elastic support 2, thereby achieving different support effects.

[0034] A progressive forming method based on magnetorheological elastomer auxiliary support, based on the above-mentioned progressive forming device based on magnetorheological elastomer auxiliary support, specifically includes the following steps: (1) fixing the magnetic field generating unit structure 5 on the base mold device 6 by bolt connection, energizing the electromagnetic coil of the magnetic field structure, and clamping the plate 18 with the clamping pressure plate 3 and the base mold 6.

[0035] (2) The machining trajectory of the target frustum part 19 is programmed, and after programming, the forming trajectory points 20 and the induced current change formula are input into the external controller of the magnetic field generating unit 5.

[0036] Furthermore, the specific calculation method of the induced current change formula is as follows:

[0037] The compression test of the magnetorheological elastomer sample was carried out using a universal testing machine to obtain the relationship between stress σ and strain ε. The Mooney Rivlin metal rubber constitutive equation was used to The test results were coupled to determine the material constants C10 and C01. The material parameters were then input into the hyperelastic material module in the Abaqus simulation software, and the incremental forming process of the sample was simulated using simulation. The simulation results predicted the forming quality of the metal sheet under different support forces, and established a relationship between the processing depth Z and the support force for optimal forming quality in magnetorheological elastomer-assisted incremental forming. Furthermore, the relationship between the processing depth Z and the induced current I can be derived from the relationship between the support force F generated by the change in the elastic body's stiffness and the induced current I:

[0038]

[0039] F=kI+m,(k>0);

[0040]

[0041] (3) Turn on the control switch of the forming tool head 1. Under the support of the magnetorheological elastomer 2 at the bottom, the forming tool head 1 is controlled by the program to roll the sheet material 18 layer by layer along the preset truncated cone track 20. Figure 4 、 5 shown.

[0042] (4) As the processing depth of the tool head 1 increases, the external controller controls the magnitude of the induced current of the magnetic field coil 15 according to the change of the coordinate parameter Z value of the program trajectory point 20, and then reduces the supporting force of the magnetorheological elastomer 2 on the sheet material layer by layer by adjusting the magnetic field size, so that the force exerted by the tool head 1 and the bottom magnetorheological elastic support body 2 on the sheet material is always consistent, ensuring that the extrusion state of the sheet material is constant, and finally achieving the complete processing and forming of the frustum part 19.

[0043] Furthermore, the specific changes of the supporting force F are as follows:

[0044] As shown by the frustum trajectory control point 7, the depth values ​​of the path point layers from top to bottom are Z1 = 0.1mm, Z2 = 0.2mm, Z3 = 0.3mm, Z4 = 0.4mm, etc. Substituting the processing depth value of each layer into the above formula, it can be seen that the induced current I of coil 15 during processing of each layer is automatically calculated by the external controller as I1, I2, I3, I4, etc., and the supporting force of magnetorheological elastomer 2 on sheet 18 during processing of each layer is F1, F2, F3, F4, etc. Furthermore, the magnetic field generating unit structure 5 automatically calculates and controls the magnitude of the induced current according to the input trajectory processing program, ensuring that sheet 18 does not fail or crack due to excessive stress concentration caused by uneven force within the forming limit.

[0045] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. An incremental forming device based on magnetorheological elastomer auxiliary support, characterized in that: The invention comprises a forming tool head (1), a clamping plate (3), a magnetorheological elastic support body (2), a magnetic field generating unit (5) and its controller, and a detachable base mold (6), wherein the forming tool head (1) is located above the plate, the clamping plate (3) is located at the edge position above the plate, and is used to fix the plate on the base mold (6), the base mold (6) accommodates the magnetorheological elastic support body (2) inside, and the plate is tightly attached to the surface of the magnetorheological elastic support body (2) after being clamped; the periphery of the base mold (6) is provided with There are a plurality of cylindrical slots for placing a magnetic field generating unit (5) for generating an effect on the magnetorheological elastic support body (2). The magnetic field generating unit (5) changes the magnetic field under the control of the controller and thus changes the shear modulus of the magnetorheological elastic support body (2) to play a supporting role on the bottom surface of the formed plate; the magnetic field generating unit (5) includes four electromagnet pairs: a first electromagnet (7) and a second electromagnet (10), a third electromagnet (14) and a fourth electromagnet (11), a fifth electromagnet (8) and a sixth electromagnet (13), and a seventh electromagnet (14). (9) and the eighth electromagnet (12), each pair of electromagnets will generate a magnetic field of a certain size after being energized; each electromagnet includes a coil (15), a pole (16), and a pole head (17). After the electromagnet is connected to a DC power supply, the energized coil (15) can generate a magnetic field of a certain size. Under the action of the external coil (15), the ferromagnetic metal atoms inside the pole (16) are rearranged in a certain order to generate magnetism, forming a magnetic field between the two pole heads (17) of each pair of electromagnets; by controlling the current passing through the coil (15), a controllable high-intensity magnetic field can be formed in the air gap between the two pole heads (17) of each pair of electromagnets; the method for the controller to control the change of the induced current is: based on the simulation results, the forming quality of the metal sheet under different supporting forces is predicted, and the relationship between the processing depth Z and the supporting force under the optimal forming quality of the magnetorheological elastomer assisted support progressive forming is established, and then the relationship between the processing depth Z and the induced current I can be obtained through the relationship between the supporting force F generated by the change of the elastic body stiffness and the induced current I: .

2. The incremental forming device based on magnetorheological elastomer auxiliary support according to claim 1 is characterized in that: The base mold is a square structure with two cylindrical slots on each side, and a total of eight cylindrical slots for placing the four electromagnet pairs. The two electromagnets in each electromagnet pair are respectively arranged on two opposite sides of the base mold, and the positions of the two electromagnets correspond to each other.

3. An incremental forming method based on magnetorheological elastomer auxiliary support, based on the incremental forming device based on magnetorheological elastomer auxiliary support according to any one of claims 1-2, characterized in that: The following steps are involved: (1) Energize the electromagnetic coil of the magnetic field generating unit and clamp the plate with the clamping plate and the base mold; (2) Programming the machining trajectory of the target part to be machined and inputting the machining trajectory into the external controller of the magnetic field generating unit structure; (3) Turn on the forming tool head control switch, and control the forming tool head to process layer by layer along the processing trajectory through the program. Under the support of the magnetorheological elastomer at the bottom, the same sheet material can be formed into a three-dimensional curved surface with multiple changes in overall and local concave and convex angles; (4) The controller controls the magnitude of the induced current of the magnetic field coil according to the change of the program processing depth Z value, and then changes the support force of the magnetorheological elastomer on the sheet metal by adjusting the magnetic field size, and finally reaches the required larger angle forming limit to form the required complex curved surface part.

4. The method according to claim 3, characterized in that The force exerted by the tool head and the bottom support on the sheet metal is always consistent, and the sheet metal extrusion state is constant.

5. The method according to claim 3, characterized in that Every time the tool head descends a level, the magnetic field coil changes the magnitude of the induced current accordingly, thereby reducing the support force of the magnetorheological elastomer on the sheet metal, ensuring that the sheet metal does not fail or rupture due to excessive stress concentration caused by uneven force within the forming limit.

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