Sheet metal member forming method

Abstract

To easily modify a processed shape in a press work.SOLUTION: A sheet metal member molding method pressing a sheet metal member to be a prescribed target shape comprises: a first step which presses a first surface of the sheet metal member and a second surface connected to the first surface with a prescribed angle after molding; and a second step which changes modification degree where the second surface is modified in a direction crossing the second surface by pressing so that dissociation is decreased from the target shape of a processing shape of the first surface when a processing shape crossing the first surface on the first surface is dissociated from the target shape by more than a prescribed degree.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to techniques for forming sheet metal members. [Background technology]

[0002] It is known that when a sheet metal member is pressed into a desired shape, the pressed member may not assume the intended shape. In particular, as described in Patent Document 1, when a pressed surface formed by a lower die and an upper die and a surface adjacent to this surface are formed, the desired shape may not be obtained. This is due to a variety of reasons, such as changes in shape caused by so-called springback due to residual stresses generated by press forming. Therefore, even when performing FEM analysis in advance, it is sometimes difficult to ensure that the shape after press forming matches the design value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-136794 Summary of the Invention [Problem to be solved by the invention]

[0004] For this reason, in practice, dies are modified after press forming. However, if partial buildup or cutting is performed to modify the die, the modified shape will appear in the formed sheet metal part. For this reason, modifying the die for the surfaces that determine the product's external shape (hereinafter, these surfaces may be referred to as "design surfaces") requires a great deal of effort. While die shapes are designed using techniques such as FEM analysis to obtain the desired shape as much as possible, such analysis is difficult to fully reflect the actual conditions, such as differences in material properties, differences in the size of the press-formed surface, and differences in drawing depth, making it difficult to create a die that obtains the desired formed shape based on preliminary analysis alone. [Means for solving the problem]

[0005] The present disclosure can be realized in the following forms or application examples.

[0006] (1) One embodiment of the present disclosure is a sheet metal member forming method. This sheet metal member forming method includes: Using a mold A sheet metal member forming method for press-forming a sheet metal member into a predetermined target shape, comprising: a first step of press-forming a first surface of the sheet metal member and a second surface that is connected to the first surface at a predetermined angle after forming; and a second step of, when a processed shape of the first surface in a direction intersecting the first surface deviates from the target shape by a predetermined amount or more, changing the degree to which the second surface is deformed by the press-forming in a direction intersecting the second surface to a side that reduces the deviation of the processed shape of the first surface from the target shape. The first step includes processing to form a plurality of beads on the second surface, and the change in the second step is a change in height of at least one of the plurality of beads, and includes a step of modifying the shape of the mold so as to change the height. This way, the second side Bead formed on Degree of press processing As its height By changing the value of the parameter, deviation of the shape of the first surface from the target shape can be reduced. (2) In this configuration, the first step ,before The change in the second step is a change to increase the height of the bead when the deviation of the shape on the first surface from the target shape is such that the protrusion amount on the first surface in a direction intersecting the first surface is insufficient from the target shape. In this way, if the protrusion amount on the first surface is insufficient, it can be corrected to increase it. (3) In this configuration, the first step ,before The modification in the second step is a modification to reduce the height of the bead when the deviation of the shape on the first surface from the target shape is such that the protrusion amount on the first surface in a direction intersecting the first surface is excessive compared to the target shape. In this way, if the protrusion amount on the first surface is excessive, it can be corrected to reduce it. (4) In the above configurations (1) to (3), the beads formed in the first step may be a plurality of beads arranged along the ridge formed by the first surface and the second surface. In this way, by changing the height of each bead, the effect can be increased by the number of beads. (5) In the above configurations (1) to (4), at least one of the plurality of beads may have its height increased or decreased. This allows for fine adjustment of the effect on the shape of the first surface of changing the processing height of the bead on the second surface.

[0007] (6) A second aspect of the present disclosure is a molded part that has been press-formed into a predetermined target shape. The sheet metal member has a first surface formed by the press-formed process and a second surface that is connected to the first surface at a predetermined angle. The second surface has a plurality of beads that are arranged along a ridge formed by the first surface and the second surface, and some of the beads have a different height than the other beads. By changing the height of some of the beads formed on the second surface, a molded part having a first surface that approximates a desired shape can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an explanatory diagram schematically illustrating the configuration of a press-forming apparatus for carrying out a press-forming method according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing an example of a press-molded product. [Figure 3] A process diagram showing the press working process. [Figure 4] FIG. 10 is an explanatory diagram showing the state before press working of the second surface begins. [Figure 5] FIG. 10 is an explanatory diagram showing a state in which the intermediate formed product is fixed during press working of the second surface. [Figure 6] FIG. 10 is an explanatory diagram showing the press working of the second surface. [Figure 7] FIG. 2 is an explanatory diagram showing an end surface obtained by cutting the second surface along a plane parallel to the ridge line between the first surface and the second surface. [Figure 8] FIG. 10 is an explanatory diagram illustrating the correlation between the face length of the second surface and the bulge of the first surface. [Figure 9] FIG. 10 is an explanatory diagram showing the relationship between the number of beads of different heights in press working and the face length. [Figure 10] FIG. 2 is a perspective view of a molded part according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] A. Sheet metal part forming method: (A1) Overview of press forming: An embodiment of the press forming method of the present disclosure will be described. Fig. 1 is a schematic diagram of a press forming apparatus 10 in which this forming method is carried out. This press forming apparatus 10 includes a main body 25 placed on a floor surface FL, a lower die fixing device (bolster) 28 attached to the main body 25, a slider 40 that moves up and down, and a balancer 20 that supports the slider 40 so that it can move up and down. A lower die 50 and an upper die 60 that press-form a sheet metal member WK are fixed to the lower die fixing device 28 and the slider 40, respectively. The configurations of the lower die 50 and the upper die 60 will be described in detail later.

[0010] FIG. 2 schematically illustrates the shape of a molded product formed by this press-forming apparatus 10. The molded product PR is formed by pressing a sheet metal member WK using the press-forming apparatus 10 and includes a first surface SF1 and a second surface SF2 that forms an angle of approximately 100 degrees with the first surface SF1. The first surface SF1 has a recess in the center, and its overall shape is formed into an outwardly bulging shape as indicated by the symbol UP in the figure. The second surface SF2 has multiple beads BD1-BD7 that are convex toward the outside of the molded product PR along a direction parallel to the ridge line RL between the first surface SF1 and the second surface SF2. In this example, seven beads of the same shape are arranged, but the number of beads BD1-BD7 may be one or more and do not necessarily have to be the same shape. The beads may also have various shapes. For example, they may be polygonal (e.g., rectangular, triangular), oval, semicircular, etc. Furthermore, beads of the same shape in plan view but with different heights (protrusion amounts) may be mixed. The heights of the beads BD1 to BD7 will be explained in detail later. In this embodiment, the first surface SF1 of the molded product PR forms part of the appearance of the final product, whereas the second surface SF2 faces other parts and does not form part of the appearance of the product. Of course, the relationship between the first surface SF1 and the second surface SF2 of the molded product PR and the appearance of the final product is arbitrary.

[0011] In Fig. 2, the reference numeral 80 denotes a three-dimensional shape measuring instrument that uses laser light. This three-dimensional shape measuring instrument 80 scans an object with laser light and accurately measures its three-dimensional shape. As will be described later, in this embodiment, a sheet metal member WK is formed once using the press forming apparatus 10 to form a formed product PR, and then the shape of the formed product PR is measured to determine any deviation from the target shape, and the mold is corrected.

[0012] 3 is a process diagram showing the steps of such press working. After the lower die 50 and upper die 60 are set in the press forming apparatus 10, press working is started by first placing the sheet metal member WK in the press forming apparatus 10 (process T100). Next, the control panel 70 of the press forming apparatus 10 is operated to move the slider 40, and the sheet metal member WK is pressed by the lower die 50 and the upper die 60 (process T110).

[0013] In the press working of this embodiment, the sheet metal member WK is pressed to form the first surface SF1 and the second surface SF2 at a predetermined angle relative to the first surface SF1, both of which are achieved by lowering the slider 40. This process will be described with reference to FIGS. 4 to 6.

[0014] As shown in Fig. 4, one lower die 50 is attached to the lower die fixture 28, while an upper die 60 attached to the slider 40 is provided with a pressure pad (hereinafter referred to as PAD) 61 and an upper curved blade 62. In the figure, the sheet metal member WK has already been formed into an intermediate molded product MP by an upper die having a shape similar to that of PAD 61, and the first surface SF1 of the molded product PR has already been formed. In this state, PAD 61 is lowered, and the intermediate molded product MP is fixed between the lower die 50 and PAD 61.

[0015] This state is shown in Figure 5. Next, the upper curved blade 62 is lowered, and the intermediate molded product MP is pressed down by the upper curved blade 62 to form the second surface SF2 of the molded product PR. This state is shown in Figure 6. Once the above-mentioned press working is completed, the slider 40 automatically rises, and the upper curved blade 62 and PAD 61 are released from the molded product PR. In this way, the molded product PR shown in Figure 2 is obtained.

[0016] Next, the molded product PR is removed (step T120), and the three-dimensional shape of the molded product PR is measured using the three-dimensional shape measuring instrument 80 (step T130). The three-dimensional shape is measured, but here, attention is particularly focused on the bulge UP of the first surface SF1. This bulge UP corresponds to the processed shape of the first surface SF1 in the direction intersecting the first surface SF1. Next, the separation ΔUp between the bulge UP of the first surface SF1 and a predetermined target shape Tup of the bulge is calculated using the following equation (1) (step 135). In the following equation, the processed shape UP and the target shape Tup are treated as the protrusion amount of the most bulged point of the designed first surface SF1, that is, as a scalar quantity. ΔUp = ┃UP - Tup┃ … (1) Then, it is determined whether or not this dissociation ΔUp is greater than a predetermined threshold value Thu (step T140).

[0017] If the determination result is ΔUp>Thu, a die correction process is performed to correct the die (step T200). This process corrects the degree to which the second surface SF2 is deformed in a direction intersecting the second surface SF2 due to press working, and in this embodiment, it corrects the height of the bead. The specific content of this process will be described later. Once the die correction is complete, the process returns to step T100, and the above-mentioned steps T100 to T140 are repeated, starting with the placement of the sheet metal member WK. On the other hand, if the determination result in step T140 is not ΔUp>Thu, it is determined that die correction is not necessary, and mass production processing is performed (step T250). In mass production processing, the required number of sheet metal members WK are press worked to produce the required number of molded products PR.

[0018] (A2) Correction of processed shape: The mold correction shown as step T200 in Figure 3 will now be described. This mold correction is performed to correct the shape of the first surface SF1 of the molded product PR in a direction intersecting the first surface SF1. The principle behind this correction will first be described. A plurality of beads BD1 to BD7 are provided on the second surface SF2, which is connected to the first surface SF1 at a predetermined angle. By correcting the height of at least some of these beads BD1 to BD7, it is possible to adjust the amount of bulge UP of the first surface SF1. This is based on the following finding.

[0019] The reason why the shape of the formed product PR, especially the bulge of the first surface SF1, deviates from the target shape is largely due to deformation caused by springback that occurs when the mold is separated after forming. This springback occurs because press working of the second surface SF2 causes uneven stress distribution on the second surface SF2 that is connected to the first surface SF1. In other words, by forming beads BD1 to BD7 on the second surface SF2, the sheet metal is stretched in the direction along the ridge line RL of the second surface SF2, and this stretch remains as stress.

[0020] Fig. 7 is a cross-sectional view taken along line VII-VII in Fig. 2. As shown in the figure, when beads BD1 to BD7 with a height D are formed on the second surface SF2, the metal plate having a length L along the ridge line RL is substantially extended to a length LL. This length LL will be referred to as the face length LL hereinafter. The face length LL is given by the following equation (2). LL=L+2n·D …(2) Here, n is the number of beads to be formed, and D is the height of each bead. Note that the bead height D may be determined as the depth of the molded product PR by turning it upside down. This process causes the second surface SF2 to shrink in the direction of the ridge line RL, which also affects the bulge UP of the first surface SF1, which connects to the second surface SF2 at a predetermined angle. While the shape of the mold is designed in advance using FEM analysis or other methods to ensure that the shape of the molded product PR matches the target shape, the extent of shape deviation due to springback caused by residual stress on adjacent surfaces often becomes apparent only after press working. Conventionally, this has been addressed by adjusting the shapes of the lower mold 50 and upper mold 60, which process the first surface SF1, by padding or grinding.

[0021] In contrast, in this embodiment, the bulge of the first surface SF1 is corrected by adjusting the longitudinal tensile stress remaining due to the formation of a bead on the second surface SF2, which is connected to the first surface SF1 at a predetermined angle. This residual stress increases or decreases depending on the face length LL along the ridge line RL of the second surface SF2. Therefore, whether the bulge UP of the first surface SF1 is excessive or insufficient with respect to the target shape Tup is determined (T210). If the bulge is insufficient, the bead height D is increased to lengthen the face length LL (T220). If the bulge is excessive, the bead height D is decreased to shorten the face length LL (T230). When the height D of the beads BD1 to BD7 is changed, the face length LL is adjusted according to Equation (2). Note that the process of increasing the bead height D includes not only increasing the height D of an existing bead but also forming one or more new beads on the second surface SF2. The new beads may be provided on the second surface SF2 where no beads exist, or may be provided between existing beads, or may be provided on the existing beads themselves.

[0022] FIG. 8 is a graph showing the relationship between the face length LL and the bulge UP of the first surface SF1, represented by a solid line JL. Because this relationship is influenced by the shape of the formed product PR, the shape and thickness of the sheet metal member WK, and even the material, the diagram is merely illustrative, but a certain positive proportional relationship is observed between the two. If the bulge UP of the first surface SF1 is insufficient relative to the target bulge Tup based on the measured three-dimensional shape of the formed product PR, the height D of the beads BD1-BD7 can be increased to lengthen the face length LL. If the bulge UP of the first surface SF1 is excessive relative to the target bulge Tup, the height D of the beads BD1-BD7 can be decreased to shorten the face length LL.

[0023] (A3) Action and effect: According to the press working method of the embodiment described above, the following advantages can be obtained. [1] Deviation from the target shape that occurs in the shape of the first surface SF1 due to press processing can be corrected by changing the height D of the beads BD1 to BD7 provided on a surface different from the first surface SF1, in this case the second surface SF2 that is connected to the first surface SF1 at a predetermined angle. [2] The correction is made by changing the height D of the beads BD1 to BD7 on the second surface SF2, which is a surface different from the first surface SF1, so there is no problem with the first surface SF1 being affected by mold corrections, for example, the transfer of welding marks from the build-up. [3] When modifying the mold to change the shape, the transfer of welding marks or the like does not occur on the first surface SF1, so the effort and cost required for modifying the mold can be reduced. [4] If the first surface SF1 is a so-called design surface that constitutes the appearance of the product, even if the shape of the design surface is modified, the appearance quality will not be reduced. [5] The degree of shape modification of the first surface SF1 can be adjusted by the height D of the beads BD1 to BD7 on the second surface SF2, so a unified approach to shape modification of the first surface SF1 is possible, there is less need to rely on the intuition of the mold engineer, and highly reproducible modifications are possible. [6] If a predetermined number of beads are provided on the molded product PR from the beginning, the same approach can be used whether the first surface SF1 is larger or smaller than the target shape.

[0024] The stamping method of the embodiment has been described above, but the bulge UP of the first surface SF1 can also be corrected by changing the height D of some of the beads rather than uniformly changing the height D of all of the beads BD1 to BD7. For example, as shown in Fig. 9, it is possible to change the height D of only beads BD4 and BD5 out of the seven beads BD1 to BD7 from the designed height D1 to a different height D2. If the number of beads changed to height D2 out of a total of n beads is m, the face length LL can be calculated by the following formula (3): LL=L+2{m·D2+(nm)·D1} …(3) In this way, the face length LL can be changed by changing the number of beads whose height D is changed, and as a result, the bulge UP of the first surface SF1 can be adjusted. This approach is particularly effective when the bulge on the first surface SF1 is biased toward the ridge line RL. The case where the face length LL is changed by changing the number of beads whose height D is changed is shown by the dashed line BL in Figure 8.

[0025] B. Embodiment as a molded part: Another embodiment of the present disclosure is a press-molded part. As shown in FIG. 10 , this molded part is a molded part PRR that has been press-formed into a predetermined target shape. The molded part includes a first surface SF1 formed by press-forming and a second surface SF2 that is connected to the first surface SF1 at a predetermined angle. The second surface SF2 has a plurality of recessed beads BD (seven in this example) that are provided along a ridge line RL formed by the first surface SF1 and the second surface SF2. This molded part PRR is characterized in that two beads BD4 and BD5, which are part of the plurality of beads BD1-BD7, have a different height compared to the other beads. Of course, the total number of beads, the number of beads with different heights, and the beads selected as the beads with different heights are all optional.

[0026] Among the multiple beads formed on the second surface SF2, beads with different heights are provided to correct the shape of the first surface SF1 if it deviates from the target shape. This eliminates the need to change the heights of all of the beads in the formed part PRR to correct the shape of the first surface SF1, particularly its bulge UP, by changing only the heights of some of the beads. This reduces the effort required for shape correction. Furthermore, changing the shape of the first surface SF1 does not require modifying the mold used to press-form the first surface SF1. Therefore, the formed part PRR does not have welding or cutting marks transferred and remaining on the first surface SF1 due to mold modification. In the example shown in FIG. 10, the press-formed heights of the two beads BD4 and BD5 are increased. However, if the bulge UP of the first surface SF1 is larger than the target shape, the press-formed height of the beads can be reduced. Furthermore, even if the bulge of the first surface SF1 is a negative bulge, that is, if a recessed shape is the target shape, the height of the bead formed by press working can be changed in the same way.

[0027] In the above explanation, the bulge UP corresponding to the processed shape and the target shape Tup are treated as scalar quantities, but they may also be treated as a collection of protrusion amounts of multiple points, or as a vector including the direction of protrusion.

[0028] In each of the above embodiments, some of the configurations realized by hardware may be replaced with software. At least a portion of the configurations realized by software may also be realized by a discrete circuit configuration. Furthermore, when some or all of the functions of the present disclosure are realized by software, the software (computer program) may be provided in a form stored on a computer-readable recording medium. The term "computer-readable recording medium" is not limited to portable recording media such as floppy disks and CD-ROMs, but also includes internal storage devices within a computer, such as various RAMs and ROMs, and external storage devices fixed to a computer, such as a hard disk. In other words, the term "computer-readable recording medium" has a broad meaning, including any recording medium on which data packets can be fixed, not just temporarily.

[0029] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0030] 10... Press forming device, 25... Main body, 28... Lower die fixture, 40... Slider, 50... Lower die, 60... Upper die, 61... PAD, 62... Upper curved blade, 70... Control panel, 80... Three-dimensional shape measuring device, BD1 to BD7... Bead, SF1... First surface, SF2... Second surface

Claims

1. A sheet metal member forming method for press-forming a sheet metal member into a predetermined target shape using a die, comprising: a first step of press-forming a first surface of the sheet metal member and a second surface that is connected to the first surface at a predetermined angle after forming; a second step of changing the degree to which the second surface is deformed by the press working in the direction intersecting the second surface to a side that reduces the deviation of the processed shape of the first surface from the target shape when the processed shape of the first surface in the direction intersecting the first surface deviates from the target shape by a predetermined amount or more; Equipped with the first step includes forming a plurality of beads on the second surface; The change in the second step is a change in the height of at least one of the plurality of beads, and the sheet metal member forming method includes a step of modifying the shape of the mold in response to the change in height.

2. The change in the second step is a change to increase the height of the at least one bead when the separation of the processed shape on the first surface from the target shape is such that the amount of protrusion on the first surface in a direction intersecting the first surface is insufficient from the target shape. The sheet metal member forming method according to claim 1.

3. The change in the second step is a change to reduce the height of the at least one bead when the separation of the processed shape on the first surface from the target shape is such that the amount of protrusion on the first surface in a direction intersecting the first surface is excessive compared to the target shape. The sheet metal member forming method according to claim 1.

4. The plurality of beads formed in the first step are provided along a ridge line formed by the first surface and the second surface. The sheet metal member forming method according to any one of claims 1 to 3.

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