Electromagnetic heating incremental forming method and device for sheet metal

Abstract

The present invention relates to a method and device for electromagnetic heating incremental forming of sheet metal, and belongs to the technical field of thermoplastic forming processing of sheet metal. The key point of the forming method and device is: using a changing current to generate a changing magnetic field, when the magnetic field passes through the sheet metal, eddy currents are formed inside the sheet metal, which promotes the heat and softening of the sheet metal, so that the metal sheet metal that is difficult to plastically form at room temperature can be smoothly deformed into a desired shape. The heating method heats up quickly, is easy to control, heats evenly, has simple equipment, and is low in cost. It solves the problem of complex equipment structure and difficult control in laser heating incremental forming and overall electric heating incremental forming of sheet metal, and also solves the problem of electric sparks burning the sheet metal due to instantaneous contact in local electric heating. At the same time, the method is safe to operate and the processing is green and environmentally friendly.

Description

Technical Field

[0001] The invention discloses a plate material electromagnetic heating incremental forming method and device, belonging to the technical field of advanced plate material plastic forming processing. Background Art

[0002] Sheet metal parts are widely used in the industrial field. Among the traditional sheet metal forming processes, stamping technology plays an important role. It has important characteristics such as high efficiency, low cost, and suitability for mass production. However, in recent years, with the rapid development of science and technology and the continuous improvement of customers' personalized needs, traditional stamping technology requires the design and manufacture of molds before it can be put into production, which results in a long production cycle and high cost. As a result, traditional stamping technology can no longer meet the needs of small batches, multiple varieties and personalized customization.

[0003] In order to adapt to the flexible market, many sheet metal dieless forming technologies have emerged, among which sheet metal incremental forming technology has received the most extensive attention and research. Incremental forming of sheet metal can make fuller use of the forming potential of materials, so this technology can be used to form sheet metal parts with greater deformation and more complex shapes. American scholar P.Roux first touched on the idea of ​​sheet metal incremental forming in his patent in 1960. In 1994, Japanese scholar Shigeo Matsubara proposed the real sheet metal CNC incremental forming technology (ISF), which introduced the idea of ​​"layered manufacturing" in rapid prototyping technology into the field of plastic processing, discretized the complex three-dimensional model of sheet metal parts in a certain direction, and generated CNC machining trajectories on each equal layer after decomposition. According to the pre-compiled CNC code, the CNC incremental forming machine tool controls the forming tool head to move along the machining trajectory to form the parts point by point, thereby obtaining the target product.

[0004] At present, the research on incremental forming is mainly focused on room temperature conditions. Although the forming performance of incremental forming materials at room temperature is significantly better than that of ordinary forming, for some materials with poor plasticity, such as titanium alloys, it is still impossible to meet the requirements when forming deeper parts. Usually, the plasticity of these materials can be greatly improved under heating conditions, so the incremental forming process under heating conditions can form such materials. Some foreign scholars have studied the local heating incremental forming of sheet metal, mainly focusing on local laser heating and stir friction heating. However, laser heating is not easy to promote because the equipment required is relatively complex, which greatly increases the processing cost. Stir friction heating requires the forming tool to rotate at high speed, which not only damages the surface quality of the formed parts, but also makes it difficult to increase the forming temperature of the sheet metal. Some foreign scholars have also studied the overall electric heating incremental forming of the sheet metal. Although the sheet metal can be evenly heated during the forming process, the high temperature is easy to affect the forming device, so a cooling system needs to be added, which greatly increases the complexity and manufacturing cost of the forming device, and the energy consumption of this heating method is relatively large. Domestic scholar Fan Guoqiang proposed a method for local electric heating progressive forming of sheet metal, which uses a forming tool head, sheet metal, pressure head, corresponding circuits and power supply to form a loop, so that Joule heat is generated at the contact point between the sheet metal and the forming tool head to perform forming. However, this type of heating method is prone to produce electric sparks at the moment when the forming tool head contacts the sheet metal, which in turn causes burns to the sheet metal. As far as current research is concerned, the thermal progressive forming method is still in the exploratory stage, and no one has come up with a more suitable heating method for use in the thermal progressive forming process. The purpose of the present invention is to find a process with low cost, simple equipment structure, easy operation and green and environmentally friendly processing for the processing of small batches of personalized products made of difficult-to-form materials, so as to better meet the development needs of modern industry. Summary of the invention

[0005] The purpose of the present invention is to address the existing problems in the thermal progressive forming of sheet metal, and to propose a sheet metal electromagnetic heating progressive forming method and device that has a wide range of applications, is easy to operate, low cost, simple structure, and is environmentally friendly to process. This technology can form high-precision complex parts and metal sheets that are difficult to plastically form at room temperature.

[0006] A sheet material electromagnetic heating incremental forming method comprises the following steps:

[0007] (1) Use CAM software to generate the machining trajectory of the required parts, and then export the NC code required by the CNC machining machine through post-processing;

[0008] (2) The forming fixture clamps the sheet during the forming process and moves synchronously with the forming tool head in the vertical direction;

[0009] (3) The forming tool head processes the sheet material layer by layer along the forming trajectory, and finally the sheet material is transformed into the desired part shape;

[0010] The feature is that it also includes the following process:

[0011] The coil under the sheet is energized, generating an induced magnetic field in the area surrounded by the coil. When the magnetic field passes through the metal sheet, eddy currents are generated in the sheet area, causing it to soften due to heat generated by the eddy current effect, thereby achieving progressive forming of the sheet.

[0012] The sheet metal electromagnetic heating incremental forming method can form parts with complex shapes and high precision requirements.

[0013] The sheet material electromagnetic heating incremental forming method can form metal sheets that are difficult to plastically form at room temperature.

[0014] A plate material electromagnetic heating progressive forming device comprises: a power source, an upper pressing plate, a plate material, a support, a forming tool head, a fastening bolt, a lower supporting plate, a coil, a pad and a bottom plate.

[0015] The power supply needs to generate a high-frequency current that varies with time during the forming process.

[0016] If the sheet material has magnetic conductivity, no coating treatment is required. For sheet material without magnetic conductivity, high temperature resistant coating treatment is required to make it magnetically conductive.

[0017] The support is a separate support, which is assembled from a plurality of small support blocks, and a certain gap is left between each small block, so that when forming, no closed induction current can be generated.

[0018] The coil is tightly wound around the periphery of the forming device to form a plurality of closed loops.

[0019] The pad is made of non-magnetic material and is fixed between the bottom plate and the support, so that the components at the lower end will not be affected by the eddy current effect to generate heat, thereby affecting the performance of other components.

[0020] Due to the adoption of the above forming method and device, the sheet metal electromagnetic heating incremental forming method and device have the following advantages:

[0021] (1) This forming method has fast heating speed, convenient control, easy operation and low cost. It solves the problems of high equipment and control requirements, high cost and complex operation in laser heating incremental forming and sheet metal integral electric heating incremental forming;

[0022] (2) This forming method uses the principle of electromagnetic induction to soften the metal sheet in the forming area by eddy current effect, thereby enabling it to be formed smoothly. This solves the problem of electric sparks burning the sheet metal in the contact area due to the moment of contact between the forming tool head and the sheet metal during local electric heating incremental forming;

[0023] (3) Reduce the amount of springback during the forming process and improve the precision of the formed parts;

[0024] (4) It can be well applied to the positive forming process of incremental forming to obtain parts with complex shapes;

[0025] (5) Metals that are difficult to plastically deform at room temperature can be smoothly formed into a desired shape by using this forming method and device;

[0026] (6) The forming method and device achieve uniform heating of the sheet forming area and also realize the green and environmentally friendly modern processing concept. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Shown is a schematic diagram of electromagnetic heating progressive positive forming processing of sheet metal.

[0028] Figure 2 Shown is a schematic diagram of the progressive reverse forming process of sheet metal by electromagnetic heating.

[0029] The numbers in the figure are: 1 power supply, 2 upper pressing plate, 3 sheet material, 4 support, 5 forming tool head, 6 fastening bolts, 7 lower supporting plate, 8 coil, 9 pad, 10 bottom plate. DETAILED DESCRIPTION

[0030] Attached Figure 1 and attached Figure 2 They are schematic diagrams of electromagnetic heating progressive positive forming and reverse forming processing of sheet metal. The forming tool head is clamped on the spindle of the CNC machine tool so that the forming tool head processes the sheet metal layer by layer along the designed forming trajectory to complete the process from local deformation to overall deformation. The electromagnetic heating device mainly includes a power supply and a coil. The coil is tightly wound around the periphery of the forming frame to form multiple closed loops. The power supply provides a high-frequency current that changes with time. When the current passes through the coil, a changing magnetic field is generated in the middle area of ​​the closed loop formed by the coil. When the magnetic field passes through the forming sheet metal, due to the principle of electromagnetic induction, an eddy current effect is generated on the sheet metal, causing the temperature of the sheet metal to rise and soften. The lower end of the support is made of magnetically insulating material to prevent the eddy current effect from affecting other components.

[0031] because Figure 2 The electromagnetic heating progressive reverse forming of the sheet metal shown can only form simple parts, with a simple structure and the basic principle is similar to that of positive forming, so it will not be elaborated here. Figure 1 The incremental positive forming of the sheet metal by electromagnetic heating is described in detail.

[0032] First, the machining trajectory of the formed parts is designed through CAM software, and its post-processing module is used to generate NC codes that can be recognized by CNC machine tools.

[0033] The forming device is installed on the processing table of the CNC machine tool and fixed by a clamp, and the forming tool 5 head is installed on the main shaft of the machine tool.

[0034] The various components of the support 4 are respectively installed on the corresponding positions of the backing plate 9 to form the designed part shape.

[0035] The backing plate 9 is made of magnetically insulating material and is fixed on the bottom plate 10 of the forming device to isolate the magnetic field and prevent the eddy current effect from affecting the performance of other components.

[0036] The coil 8 is tightly wound around the periphery of the forming device to form a plurality of closed loops, with both ends extending out to be connected to a power source respectively. The power source provides a high-frequency current that changes with time, so that a constantly changing magnetic field is generated in the middle area of ​​the closed loop.

[0037] If the sheet material 4 has magnetic conductivity, it can be clamped between the upper pressing plate 2 and the lower supporting plate 7 by the fastening bolts 6 without any treatment. If the sheet material 4 does not have magnetic conductivity, it needs to be treated with a high-temperature resistant coating on the surface to make it magnetic before clamping.

[0038] The NC code is imported into the CNC machine tool to drive the forming tool head 5 to process the sheet material layer by layer along the designed forming trajectory. During the processing, the upper pressing plate 2 and the lower supporting plate 7 are synchronized with the vertical movement of the forming tool head.

[0039] After the processing is completed, the forming tool head is lifted to a safe position, the machine tool stops, the power supply 1 is turned off, and when the sheet material 4 cools to room temperature, the sheet material is removed to obtain a formed part.

Claims

1. A sheet metal electromagnetic heating incremental forming device, characterized in that: The electromagnetic heating progressive forming device for sheet metal comprises: a power supply, a forming frame, an upper pressing plate, a sheet metal, a support, a forming tool head, a fastening bolt, a lower supporting plate, a coil, a pad and a bottom plate; the forming frame is fixedly connected to the bottom plate, the coil is wound around the periphery of the forming frame to form a plurality of closed loops, and the two ends are respectively connected to the power supply, the power supply provides a high-frequency current that changes with time, when the current passes through the coil, a changing magnetic field is generated in the middle area of ​​the closed loop formed by the coil, the sheet metal is located above the coil, when the magnetic field passes through the forming sheet metal, an eddy current effect is generated on the entire forming area of ​​the sheet metal, so that the temperature of the sheet metal is increased and softened; the pad is made of magnetic-insulating material and fixed between the bottom plate and the support; the lower end of the support is made of magnetic-insulating material, and the various components of the support are respectively installed on the pad to form the designed part shape; the support is a separate type, assembled from many small pieces, and there is a gap between each small piece; the sheet metal is clamped between the upper pressing plate and the lower supporting plate by fastening bolts, and during processing, the upper pressing plate and the lower supporting plate move synchronously with the forming tool head in the vertical direction.

2. According to the sheet metal electromagnetic heating incremental forming device of claim 1, it is characterized in that: Magnetic sheets do not need to be coated, but non-magnetic sheets need to be coated to make them magnetic.

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