Dimensional variation factor analysis method, dimensional variation factor analysis device, dimensional variation factor analysis program, and method for manufacturing press-molded article

Abstract

In the present invention, press-molding analysis is used to identify which shape variation, of sites in a blank with shape variation, are factors in dimensional variation. The invention includes: acquiring the shape of a standard press-molded article; acquiring the shape of a standard shape variant blank press-molded article; and determining a deviation site and a first deviation quantity between the shape of the standard press-molded article and the shape of the standard shape variant blank press-molded article. Moreover, the invention includes: generating a plurality of deformed shape variant blank models, in each of which a part of a blank with shape variation has been altered to be flat; and acquiring, for each of the deformed shape variant blank models, the shape of a deformed shape variant blank press-molded article. Then, a deviation site and a second deviation quantity between the shape of the standard press-molded article and the shape of each of the deformed shape variant blank press-molded articles are determined. Subsequently, the first deviation quantity and the second deviation quantity are compared, thereby assessing which shape variation site in a blank with shape variation is serving as a principal factor of the deviation.

Description

Dimensional variation factor analysis method, dimensional variation factor analysis device, dimensional variation factor analysis program, and method for manufacturing press-molded product

[0001] The present invention relates to an analytical technique for evaluating factors of dimensional variation in a press-formed product relative to a target part shape. The press-formed product is formed by press-forming a blank with shape variation taken from a metal plate with shape variation. Specifically, the present invention relates to an analytical technique for evaluating which part of the blank with shape variation is the cause of the dimensional variation. The present invention also relates to a method for manufacturing a press-formed product equipped with the above analytical technique.

[0002] Here, in this specification, the shape variation of the blank refers to, for example, a wave shape in which unevenness is continuously formed along a predetermined direction on the surface of the blank. The application of the present invention is not limited to automobile parts. The present invention can be applied to all processes in which plate materials are press-formed. Furthermore, the material for press forming is not limited to steel. The material for press forming can also be iron alloys such as stainless steel, as well as non-ferrous and non-metallic materials.

[0003] Water-quenched cold-rolled steel sheets undergo volume expansion due to rapid cooling. Therefore, water-quenched cold-rolled steel sheets develop a wavy sheet shape. Thus, the metal sheets to be press-formed and the blanks cut from the metal sheets are not completely flat, and may have a wavy shape (shape variation). When a blank having such a wavy shape is pressed, the shape variation affects the dimensional variation of the press-formed product after pressing. A wavy blank is a blank with shape variation. This shape variation may cause the manufactured press-formed product to deviate from the target dimensional accuracy. In particular, when the cold-rolled steel sheet is a high-strength steel sheet of 1470 MPa or higher, the adverse effect of the shape variation on the dimensional accuracy of the press-formed product becomes significant.

[0004] Conventionally, an analysis method for predicting the effects of shape variation is disclosed, for example, in Patent Document 1. The analysis method described in Patent Document 1 uses press forming analysis to compare the shape of a press-formed product obtained by press-forming a flat blank with the shape of a press-formed product obtained by press-forming a corrugated blank. The deviation position and deviation amount between the two shapes are then determined. Furthermore, the press-formed product shape obtained by press-forming a flat blank is compared with the shape of a press-formed product obtained by press-forming a corrugated blank with the same amplitude as the corrugated blank but with a different period. The deviation position and deviation amount between the two shapes are then determined. Patent Document 1 also discloses that, for two types of deviation amounts, a region including a deviation position where a deviation amount exceeding a threshold occurs is identified as a region requiring countermeasures (a region where dimensional variation is a concern).

[0005] JP 2023-103926 A

[0006] In Patent Document 1, the shape of a press-formed product from a flat blank model is compared with the shape of a press-formed product from a corrugated blank model, and areas where deviations are large are identified as areas requiring countermeasures. These areas requiring countermeasures are areas where dimensional fluctuations are a concern. However, according to the inventor's investigation, the corrugation shapes of other areas may affect the deviations in areas where deviations are large. Therefore, even if only the shape of the areas requiring countermeasures identified in Patent Document 1 is improved, the effect of improving dimensional fluctuations may be limited.

[0007] The present invention has been made with a focus on the above points, and aims to identify, by using press forming analysis, which part of a blank with shape variation is the cause of the dimensional variation.

[0008] The inventors thought that if it were possible to identify the location of the waviness (shape variation) in a steel sheet (blank) that is the main cause of dimensional variation in the part shape after pressing, it would be possible to determine which part of the steel sheet should be subjected to intensive correction when correcting the shape of the steel sheet. From this perspective, the present invention was developed.

[0009] In order to solve the problem, one aspect of the present invention is an analytical method for identifying which portion of a blank is responsible for a dimensional variation factor relative to a target part shape of a press-formed product formed by press-forming a blank having shape variations taken from a metal plate having shape variations using a press die, the method including: a step of performing press-forming analysis in which a flat blank model having a flat shape is press-formed with a die model set based on the target part shape, and acquiring the shape of the press-formed product after mold release as a reference press-formed product shape; a reference shape variation blank model generation step of generating a reference shape variation blank model which is a model of a blank; a reference shape variation press-formed product shape acquisition step of performing press forming analysis using the reference shape variation blank model to perform press forming with the set die model and acquiring the press-formed product shape after demolding as the reference shape variation blank press-formed product shape; a first deviation amount acquisition step of comparing the reference press-formed product shape with the reference shape variation blank press-formed product shape to determine a deviation portion where the two shapes deviate and a first deviation amount which is the deviation amount; a deformed shape variation blank model generation step for generating a plurality of deformed shape variation blank models, which are models in which a part of a blank having a shape variation is changed to be flat, by changing the part to be changed to be flat; a deformed shape variation press-formed product shape acquisition step for performing a press-forming analysis using the deformed shape variation blank model to perform press-forming with the set die model, and acquiring the shape of the press-formed product after demolding as the deformed shape variation blank press-formed product shape for each of the plurality of deformed shape variation blank models; and a determination step of comparing the first deviation amount with the second deviation amount at the same portion of the press-formed product shape to determine which portion of the blank with the shape variation is the main cause of the shape variation that is the main cause of the deviation between the reference press-formed product shape and the reference shape variation blank press-formed product shape.

[0010] According to the present invention, it is possible to clarify which position of the blank is the main cause of the shape variation (wave shape) that causes the dimensional variation of a pressed part made using a blank with shape variation. As a result, it is possible to determine which position of the blank should be focused on for shape correction. This makes it possible to more effectively prevent a decrease in yield due to shape defects.

[0011] 1 is a diagram illustrating the processing of a dimensional variation factor analysis method according to an embodiment of the present invention. It is a conceptual diagram illustrating a dimensional variation factor analysis device according to an embodiment of the present invention. It is a diagram illustrating the shape of a reference variable shape blank with shape variation used in the examples. It is a diagram illustrating a press-formed product shape (target part shape) targeted in the examples. It is a conceptual diagram illustrating a wave shape that periodically changes at a predetermined pitch and amplitude, which is set (assigned) to a reference shape variation blank model in a first example. It is a diagram illustrating a reference shape variation press-formed product shape and the positions of portions A to E. It is a diagram illustrating the division of regions in the examples. It is a diagram illustrating a deformed shape variation blank model (deformed blank) in the examples. (a) is a diagram illustrating a deformed blank 1 in which regions other than region A are flattened. (b) is a diagram illustrating a deformed blank 2 in which regions other than region B are flattened. (c) is a diagram illustrating a deformed blank 3 in which regions other than region C are flattened. It is a diagram illustrating an improved shape variation blank model in a first example. It is a conceptual diagram illustrating a wave shape that periodically changes at a predetermined pitch and amplitude, which is set (assigned) to a reference shape variation blank model in a second example. It is a diagram illustrating an improved shape variation blank model in a second example. FIG. 10 is a conceptual diagram illustrating a waveform according to the shape variation of an actual blank, which is set (given) to a reference shape variation blank model in a third embodiment. FIG. 11 is a diagram illustrating an improved shape variation blank model in the case of deterioration in a third embodiment. FIG. 12 is a diagram illustrating an improved shape variation blank model in the case of improvement in a third embodiment. FIG. 13 is a conceptual diagram illustrating a waveform according to the shape variation of an actual blank, which is set (given) to a reference shape variation blank model in a fourth embodiment. FIG. 14 is a diagram illustrating an improved shape variation blank model in the case of improvement in a fourth embodiment.

[0012] An embodiment of the present invention will be described below with reference to the drawings. (Concept) This embodiment has been made, for example, based on the following concept. First, a reference variable shape blank model having a geometrically corrugated shape is generated based on a blank having shape variations. Then, press forming analysis is performed by CAE using this blank model. Also, a flat blank model of a flat blank is generated. Then, press forming analysis is performed by CAE using this blank model. Then, the shapes of the two press-formed products are compared, and locations (sites) with large deviations are identified as locations with a variation concern. Note that it is necessary to reduce the deviations in these locations with large deviations. Furthermore, the locations with a variation concern are locations with dimensional variations.

[0013] Next, the reference variable shape blank model with a corrugated shape is divided into multiple regions. Then, for example, a blank model with shape variation only in each region and other portions flattened is designated as a variable shape blank model. Press forming analysis is performed using this variable shape blank model using CAE. Then, the press-formed product shape using the flat blank model is compared with the press-formed product shape using each partially flattened variable shape blank model. That is, for each partially flattened variable shape blank model, the press-formed product shapes of both are compared, and the deviation amount at the identified variation concern area is determined. Then, based on the deviation amount at the identified variation concern area for each partially flattened variable shape blank model, it is evaluated which region's variation shape (wave shape) affects which portion of the pressed part's dimensional variation difference. This will be explained in more detail below.

[0014] (Configuration) "First Embodiment" The manufacture of a press-formed product according to this embodiment uses a blank with shape variations taken from a metal plate with shape variations (unevenness). In this embodiment, the blank is press-formed (press working) using a press die corresponding to the target shape of the press-formed product. It is assumed that the press-formed product is manufactured in this manner. The press forming includes forming and draw forming. This embodiment is a dimensional variation factor analysis method for identifying (evaluating) which portion of the blank with shape variations is responsible for the dimensional variation of the press-formed product relative to the target part shape during the manufacture of the press-formed product. Here, the shape variations of the metal plate and the blank refer to, for example, shape variations in which continuous unevenness is formed along a predetermined direction. The blank is cut into the desired contour shape for press forming.

[0015] Examples of the target metal plate material include steel and aluminum alloy. However, the material is not limited thereto. The present invention is a technology suitable for high-strength steel plates with a tensile strength of 980 MPa or more, particularly ultra-high-strength steel plates with a tensile strength of 1470 MPa or more. When the tensile strength of the metal plate is high, the impact of shape variations of the metal plate and blank on dimensional accuracy is greater than when the tensile strength is low. As shown in FIG. 1 , the dimensional variation factor analysis method of this embodiment includes a reference press-formed product shape acquisition step S1, a reference shape variation blank model generation step S3, a reference shape variation press-formed product shape acquisition step S5, a first deviation amount acquisition step S7, a deformed shape variation blank model generation step S9, a deformed shape variation press-formed product shape acquisition step S11, a second deviation amount acquisition step S13, and a determination step S15.

[0016] <Reference Press-Formed Product Shape Acquisition Step S1> In the reference press-formed product shape acquisition step S1, a press-forming analysis is performed using a flat blank model with a flat shape, in which a die model set based on the target part shape is used for press-forming. Then, the shape of the press-formed product after demolding is acquired as the reference press-formed product shape. The set die model is set based on the molding surface shape of an actual die that press-forms the flat blank into the target part shape. For example, the set die model is a die model with a shape that follows the target part shape. However, a die model corrected for springback after demolding is preferred as the set die model.

[0017] In this specification, "press forming analysis" includes an analysis for obtaining the shape at the bottom dead center of press forming and an analysis for obtaining the shape after mold release, i.e., after springback. The flat blank model is a blank model that has been conventionally used in press forming analysis and has a flat shape without any irregularities. In other words, the flat blank model is a blank model in which the wave shape (shape variation) of the blank used in the target press forming is changed to a flat shape.

[0018] Press forming analysis is usually performed using CAE analysis such as the finite element method (FEM). That is, press forming analysis may be performed using a computer-assisted structural analysis, such as a known CAE analysis. Press forming includes form forming and draw forming, and the present invention can be applied to any of these press forming methods. The reference press-formed product shape after demolding determined by press forming analysis has a change amount due to demolding from the bottom dead center of the forming.

[0019] The amount of change is the value obtained by subtracting the height of the corresponding part of the shape at the bottom dead center of the press from the height of each part of the shape of the press-formed product after it is released from the mold and springs back after press forming in the press forming direction. Therefore, the amount of change is a value equivalent to the amount of springback in the press forming direction. If the height difference (amount of change) is + (plus), the shape after release will be more convex than the shape at the bottom dead center of the press. On the other hand, if the height difference (amount of change) is - (minus), the shape after release will be more concave than the shape at the bottom dead center of the press.

[0020] <Reference Shape Variation Blank Model Generation Step S3> The reference shape variation blank model generation step S3 is a step of generating a reference shape variation blank model, which is a model of a blank with shape variation. The reference shape variation blank model is a blank model having a waveform (shape variation) corresponding to the shape variation of an actual metal plate with shape variation. The reference shape variation blank model generation step S3 generates a reference shape variation blank model based on measurement data obtained by measuring the shape of an actual blank sampled from a predetermined position on a metal plate with shape variation. The shape measurement of the actual blank is performed using, for example, a three-dimensional shape measuring device using a laser rangefinder. The shape variation of the actual blank typically has an irregular uneven shape as shown in FIG. 12(b). In this embodiment, the shape variation (waveform) to be imparted to the blank model is determined using one of the following two generation methods.

[0021] [First Generation Method] In the first generation method, the shape of an actual blank is measured. From the measurement results, statistical processing such as average and median values ​​is performed on the pitch and amplitude of the waveform of the actual blank. A set pitch and set amplitude are determined through this processing. A waveform that periodically changes at the determined set pitch and set amplitude is then assigned as a shape variation. The waveform assigned by the first generation method is a waveform like that shown in FIG. 5. Note that the actual blank to be measured does not have to be the blank itself used for press working. The shape variation trends of metal plates manufactured using the same equipment will be similar. It is preferable that the metal plate to be measured is a metal plate manufactured under the same manufacturing conditions as the metal plate to be pressed. Note that the manufacturing conditions include heating conditions, plate thickness conditions, metal material, etc.

[0022] [Second Generation Method] In the second generation method, the shape of an actual blank taken from a target metal plate is measured. Based on the measurement results, a blank model having a corrugated shape that matches the shape of the actual blank is generated as a reference shape variation blank model. Instead of the target metal plate, another metal plate manufactured using the same equipment and under the same conditions may be used. In this case, the reference shape variation blank model is a blank model having the same shape variation as the actual blank and has an irregular concave-convex shape. The irregular concave-convex shape is, for example, as shown in FIG. 12(b).

[0023] <Reference Shape Variation Press-Formed Product Shape Acquisition Step S5> In the reference shape variation press-formed product shape acquisition step S5, a press forming analysis is performed using a reference shape variation blank model to perform press forming with a set die model. Then, the shape of the press-formed product after mold release is acquired as the reference shape variation blank press-formed product shape. As described above, the press forming analysis includes an analysis to acquire the shape at the bottom dead center during press forming and an analysis to acquire the shape after mold release, i.e., after springback.

[0024] <First Deviation Amount Acquisition Step S7> The first deviation amount acquisition step S7 compares the reference press-formed product shape with the reference-shape-varied blank press-formed product shape. The first deviation amount acquisition step S7 is a step of determining, from the comparison, deviation areas where the two shapes deviate and the deviation amounts as the first deviation amounts. For example, multiple regions are set for the shape of the press-formed product. Representative locations in each region are then set as the regions for which the deviation amounts are to be calculated. The regions may be set to represent regions where springback is likely to occur after demolding, for example. Furthermore, for example, data may be stored as pairs of deviation areas and first deviation amounts.

[0025] In this embodiment, the press-formed product shape at the bottom dead center of the press was used as the reference shape. The amount of change (springback amount) from the reference shape to each portion of the press-formed product shape after demolding was calculated. The difference in the amount of change between the two press-formed product shapes was calculated as the deviation amount. This also applies to the second deviation amount acquisition step S13 described below. That is, the first actual deviation amount is the value obtained by subtracting the amount of change in the reference press-formed product shape from the amount of change in the reference shape-varying blank press-formed product shape. The amount of change in the reference shape-varying blank press-formed product shape corresponds to the amount of change using an actual blank with shape variation. The amount of change in the reference press-formed product shape is the amount of change using a flat blank model. Therefore, if the first actual deviation amount is + (plus), the corresponding portion of the reference shape-varying blank press-formed product shape will have a convex shape compared to the reference press-formed product shape. Furthermore, if the first actual deviation amount is - (minus), the corresponding portion of the reference shape-varying blank press-formed product shape will have a concave shape compared to the reference press-formed product shape.

[0026] <Deformed Shape Variation Blank Model Generation Step S9> The deformed shape variation blank model generation step S9 is a step of generating a deformed shape variation blank model, which is a model in which a portion of the waveform of a reference shape variation blank having a waveform (shape variation) is changed to a flattened shape. The deformed shape variation blank model generation step S9 generates multiple types of deformed shape variation blank models by changing the portion to be flat. However, each deformed shape variation blank model has a waveform in at least a portion.

[0027] In the deformed shape variation blank model generation step S9 of this embodiment, the reference shape variation blank 3 is divided into a plurality of regions. FIG. 7 shows an example in which the reference shape variation blank 3 is divided into three regions A, B, and C along the longitudinal direction. Note that regions do not have to be set over the entire surface of the reference shape variation blank 3. There may be surfaces on which no regions are set. Then, for each region, a blank model in which the portions other than the target region of the reference shape variation blank model are flattened is generated as the deformed shape variation blank model 5 (see FIG. 8). In other words, based on the reference shape variation blank 3, each deformed shape variation blank model 5 is generated by leaving only the waveform (shape variation) present in the target region and flattening the other portions.

[0028] In this embodiment, the blank is divided into multiple regions arranged along the longitudinal direction of the blank (the rolling direction of the metal plate) as shown in FIG. 7 . The division may be performed along the width direction of the blank, or the regions may be set in a grid pattern. The sizes of the regions do not need to be equal. In this embodiment, deviation locations where the first deviation amount is equal to or greater than a predetermined amount are identified as variation concern locations from the data on the "deviation location and first deviation amount" obtained in the first deviation amount acquisition step S7. The regions may then be set so that each of the above regions includes a respective variation concern location. For example, the variation concern location and its surrounding area may be set as each region, or when dividing the blank in the longitudinal direction, the blank may be divided so that each section includes one or more variation concern locations.

[0029] <Deformed-shape-varying press-formed product shape acquisition step S11> In the deformed-shape-varying press-formed product shape acquisition step S11, a press forming analysis is performed using the deformed-shape-varying blank model 5 to perform press forming with the set die model. This is a processing step in which the shape of the press-formed product after mold release is acquired as the deformed-shape-varying blank press-formed product shape. In the deformed-shape-varying press-formed product shape acquisition step S11, a process is performed to acquire the deformed-shape-varying blank press-formed product shape for each of the multiple deformed-shape-varying blank models 5. As described above, the press forming analysis includes an analysis to acquire the shape at the bottom dead center during press forming and an analysis to acquire the shape after mold release, i.e., after springback.

[0030] <Second deviation amount acquisition step S13> The second deviation amount acquisition step S13 compares the reference press-formed product shape with each deformed-shape-varying blank press-formed product shape. The second deviation amount acquisition step S13 is a step of determining the deviation portion where the two shapes deviate and the second deviation amount, which is the amount of deviation. The second deviation amount acquisition step S13 determines the deviation portion and the second deviation amount for each of the multiple deformed-shape-varying blank models 5. The method for determining the second deviation amount is the same as the method for determining it in the first deviation amount acquisition step S7.

[0031] <Determination Step S15> In determination step S15, the first deviation amount and the second deviation amount are compared for the same portion of each press-formed product shape. Based on this comparison, it is determined which portion of the blank with shape variation is the main cause of the deviation between the reference press-formed product shape and the reference shape-varying blank press-formed product shape. The determination of the main cause of the deviation is performed, for example, as follows. In determination step S15 of this embodiment, for the same portion, a deformed shape-varying blank model 5 having one or more second deviation amounts relatively close to the first deviation amount is identified. Then, a region having a wavy shape in the identified deformed shape-varying blank model 5 is determined to be the main cause of the shape variation for the same portion. This is performed, for example, for each location where the first deviation amount is equal to or greater than a predetermined amount. The second deviation amount relatively close to the first deviation amount is not limited to one. Further, the determination step S15 may be performed only on the portions where the first deviation is equal to or greater than a predetermined amount, among the portions where the customer has strict requirements. The determination step S15 of this embodiment includes, for example, a dimensional variation portion specifying step and a factor portion determining step S15B.

[0032] [Dimensional Variation Location Identifying Step S15A] In the dimensional variation location identifying step S15A, deviation locations where the absolute value of the first deviation amount is equal to or greater than a preset deviation threshold are identified from the deviation locations obtained in the first deviation amount obtaining step S7 and the first deviation amount. The identified deviation locations are identified as dimensional variation locations.

[0033] [Causal Location Determination Step S15B] For each dimensional variation location determined in the dimensional variation location identification step S15A, the second deviation amount and the first deviation amount for each deformed shape variation blank model 5 for the same location as the dimensional variation location are compared. Then, one or more deformed shape variation blank models 5 having a second deviation amount relatively close to the first deviation amount are identified. Furthermore, a region having a corrugated shape in the identified deformed shape variation blank model 5 is determined to be the shape variation location that is the main cause of the target dimensional variation location. Here, it is not necessary to identify all dimensional variation locations as improvement locations. Of the identified dimensional variation locations, only those locations requiring high dimensional accuracy may be selected as improvement locations. Then, for only the selected dimensional variation locations, correction processing can be performed on the blank based on the determination result of which portion of the blank's corrugated shape (shape variation) is the cause.

[0034] (Method for manufacturing a press-formed product) The method for manufacturing a press-formed product of this embodiment is a method for manufacturing a press-formed product having a target part shape by press-forming a blank taken from a metal plate having shape variations using a press die. Prior to press forming, a portion of the blank determined to be the main cause of deviation in determination step S15 of the dimensional variation factor analysis method of this embodiment is subjected to intensive shape correction. Shape correction is a process for intensively flattening the shape variations of the portion of the blank determined to be the main cause of deviation. The blank is then press-formed into the target part shape. This makes it possible to more efficiently reduce dimensional variations and manufacture a press-formed product having the target part shape.

[0035] Second Embodiment (Dimensional Variation Factor Analysis Device 11) The dimensional variation factor analysis method described in the first embodiment can be realized by causing a computer such as a PC (personal computer) to execute a preset program. An example of such a device, a dimensional variation factor analysis device 11, will be described in this embodiment. As shown in FIG. 2 , the dimensional variation factor analysis device 11 of this embodiment is configured by a computer such as a PC (personal computer), and has a display device 12, an input device 13, a storage device 14, a working data memory 15, and a processing unit 20. The display device 12, the input device 13, the storage device 14, and the working data memory 15 are connected to the processing unit 20, and their respective functions are executed in response to commands from the processing unit 20.

[0036] <Display device 12> The display device 12 is used to display analysis results, etc., and is composed of a liquid crystal monitor, etc. <Input device 13> The input device 13 is used to give display instructions for blanks, press-formed products, etc., and to input conditions from the operator, and is composed of a keyboard, mouse, etc. <Storage device 14> The storage device 14 is used to store various files such as shape files 30 for blanks and press-formed products, and is composed of a hard disk, etc. <Working data memory 15> The working data memory 15 is used to temporarily store data used by the calculation processing unit 20 and for calculations, and is composed of a RAM (Random Access Memory), etc.

[0037] <<Calculation Processing Unit 20>> As shown in FIG. 2 , the calculation processing unit 20 includes a reference press-formed product shape acquisition unit 21, a reference shape variation blank model generation unit 22, a reference shape variation press-formed product shape acquisition unit 23, a first deviation amount acquisition unit 24, a deformed shape variation blank model generation unit 25, a deformed shape variation press-formed product shape acquisition unit 26, a second deviation amount acquisition unit 27, and a determination unit 28. The calculation processing unit 20 includes a CPU (Central Processing Unit) such as a PC, and a storage unit in which a predetermined program for processing the functions of each unit is stored. Each of the above units functions when the CPU executes the predetermined program. The functions of each of the above units in the calculation processing unit 20 are described below.

[0038] <Reference press-formed product shape acquisition unit 21> The reference press-formed product shape acquisition unit 21 executes the reference press-formed product shape acquisition step S1 described in the first embodiment. The reference press-formed product shape acquisition unit 21 performs press-forming analysis using a flat blank model with a flat shape, in which press-forming is performed with a die model set based on the target part shape. Then, a process is performed to acquire the shape of the press-formed product after demolding as the reference press-formed product shape.

[0039] <Reference Shape Variation Blank Model Generation Unit 22> The reference shape variation blank model generation unit 22 executes the reference shape variation blank model generation step S3 described in the first embodiment. The reference shape variation blank model generation unit 22 performs press forming analysis using a flat blank model with a flat shape, in which press forming is performed with a die model set based on the target part shape. Then, it executes a process to acquire the shape of the press-formed product after demolding as the reference press-formed product shape. The reference shape variation blank model generation unit 22, for example, calculates the pitch and amplitude from measurements of the shape of an actual blank sampled from a metal plate with shape variation. A blank model having a waveform that periodically changes with the calculated pitch and amplitude is generated as the reference shape variation blank model. Furthermore, the reference shape variation blank model generation unit 22 acquires, for example, measurement results of the shape of an actual blank sampled from a metal plate with shape variation. Based on the measurement results, a blank model having a waveform that conforms to the shape of the actual blank is generated as the reference shape variation blank model.

[0040] <Reference Shape Variation Press-Formed Product Shape Acquisition Unit 23> The reference shape variation press-formed product shape acquisition unit 23 executes the reference shape variation press-formed product shape acquisition step S5 described in the first embodiment. The reference shape variation press-formed product shape acquisition unit 23 executes a process to generate a reference shape variation blank model, which is a model of a blank with shape variation. The reference shape variation press-formed product shape acquisition unit 23 uses the reference shape variation blank model to perform press forming analysis of press forming using the above-set die model. Then, it executes a process to acquire the shape of the press-formed product after demolding as the reference shape variation blank press-formed product shape.

[0041] <First deviation amount acquisition unit 24> The first deviation amount acquisition unit 24 executes the first deviation amount acquisition step S7 described in the first embodiment. The first deviation amount acquisition unit 24 compares the reference press-formed product shape with the reference-shape-variant blank press-formed product shape. The first deviation amount acquisition unit 24 then executes a process to determine the deviation portion where the two shapes deviate and the first deviation amount, which is the amount of deviation. In this embodiment, the first deviation amount is the difference between the springback amount of a predetermined portion of the reference press-formed product shape and the springback amount of the same portion of the reference press-formed product shape in the reference-shape-variant blank press-formed product shape.

[0042] <Deformed Shape Variation Blank Model Generation Unit 25> The deformed shape variation blank model generation unit 25 executes the deformed shape variation blank model generation step S9 described in the first embodiment. The deformed shape variation blank model generation unit 25 executes a process of generating multiple deformed shape variation blank models 5, which are models in which a portion of a blank having shape variation has been changed to be flat, by changing the portion to be flat. The deformed shape variation blank model generation unit 25, for example, divides the blank having shape variation into multiple regions. Then, for each region, a blank model in which a portion other than the target region of the reference shape variation blank model has been changed to be flat is generated as the deformed shape variation blank model 5.

[0043] <Deformed-shape-variable press-formed product shape acquisition unit 26> The deformed-shape-variable press-formed product shape acquisition unit 26 executes the deformed-shape-variable press-formed product shape acquisition step S11 described in the first embodiment. The deformed-shape-variable press-formed product shape acquisition unit 26 performs press-forming analysis of press-forming with the set die model using the deformed-shape-variable blank model 5. Then, a process of acquiring the shape of the press-formed product after demolding as the deformed-shape-variable blank press-formed product shape is performed for each of the multiple deformed-shape-variable blank models 5.

[0044] <Second Deviation Amount Acquisition Unit 27> The second deviation amount acquisition unit 27 executes the second deviation amount acquisition step S13 described in the first embodiment. The second deviation amount acquisition unit 27 compares the reference press-formed product shape with each deformed-shape-varied blank press-formed product shape. Then, the second deviation amount acquisition unit 27 executes a process to determine the deviation portion between the two shapes and the second deviation amount, which is the deviation amount. This process is executed for each of the multiple deformed-shape-varied blank models 5. In this embodiment, the second deviation amount is the difference between the springback amount of a predetermined portion in the reference press-formed product shape and the springback amount of a portion in the deformed-shape-varied blank press-formed product shape that is the same as the predetermined portion in the reference press-formed product shape.

[0045] <Determination Unit 28> The determination unit 28 executes the second deviation amount acquisition step S13 described in the first embodiment. The determination unit 28 compares the first deviation amount and the second deviation amount at the same portion of the press-formed product shape. This comparison determines which portion of the blank with shape variation is the main cause of the deviation between the reference press-formed product shape and the reference shape-varied blank press-formed product shape. For example, the determination unit 28 determines a region of a wave shape in the deformed shape variation blank model 5 that has one or more second deviation amounts relatively close to the first deviation amount for the same portion as the main cause of the shape variation for the same portion. Two or more second deviation amounts relatively close to the first deviation amount may be acquired. The determination unit 28 of this embodiment includes a dimensional variation location identification unit and a factor location determination unit 28B.

[0046] [Dimensional Variation Location Identification Unit 28A] The dimensional variation location identification unit 28A performs processing to identify, as a dimensional variation location, a deviation location where the absolute value of the first deviation amount is equal to or greater than a preset deviation threshold, based on the deviation location and the first deviation amount obtained by the first deviation amount acquisition unit 24. [Causal Location Determination Unit 28B] For each identified dimensional variation location, the causal location determination unit 28B compares the second deviation amount and the first deviation amount for each of the deformed shape variation blank models 5 for the same location as the dimensional variation location. Then, the causal location determination unit 28B determines a region having a wave shape in the deformed shape variation blank model 5 that has one or more second deviation amounts relatively close to the first deviation amount as a shape variation location that is the main cause of the dimensional variation location of the target dimensional variation location.

[0047] (Dimensional Variation Factor Analysis Program) As described above, each unit of the arithmetic processing unit 20 in the dimensional variation factor analysis device 11 of this embodiment is realized by the CPU executing a predetermined program. Therefore, the dimensional variation factor analysis program according to the present invention can be specified to cause a computer to function as a reference press-formed product shape acquisition unit 21, a reference shape variation blank model generation unit 22, a reference shape variation press-formed product shape acquisition unit 23, a first deviation amount acquisition unit 24, a deformed shape variation blank model generation unit 25, a deformed shape variation press-formed product shape acquisition unit 26, a second deviation amount acquisition unit 27, and a determination unit 28.

[0048] (Operations and Others) For example, consider a case where multiple press-formed products are stacked and joined to assemble into vehicle body members. In such a case, if there is a large deviation in the shape of the press-formed products, joining the press-formed products to each other becomes difficult. This impact is particularly significant when the deviation is large, especially in flange portions. In such a case, countermeasures may be required. The flange portion is often used as a joining location. In this embodiment, a portion that is expected to be significantly affected by shape variations in the blank, i.e., a portion that is expected to have a large deviation, is identified as a dimensional variation location. Here, the deviation at the dimensional variation location may not be the main cause of the dimensional variation in the blank, where the position of the corrugation (shape variation) corresponding to the dimensional variation location is not the main cause of the dimensional variation. In other words, the dimensional variation location may not be a location requiring countermeasures. In some cases, flattening the corrugation of a portion of the actual blank that corresponds to the dimensional variation location may increase the deviation at the dimensional variation location.

[0049] Therefore, in this embodiment, multiple deformed shape variation blank models 5 are used, each limiting the waveform region, to determine which region's waveform affects the deviation at the target dimensional variation location. This makes it possible to more accurately determine the portion requiring countermeasures for each dimensional variation location. Then, for the dimensional variation location requiring improvement, the shape variation of the blank portion requiring countermeasures that is the cause of the dimensional variation location is improved. This makes it possible to more effectively reduce dimensional variation. For example, countermeasures can be taken by concentrating and flattening the blank waves, which are the main cause.

[0050] An example confirming the operation and effect of this embodiment will be described. "First Example" In this example, consider the case where a blank 1 having the shape variation shown in FIG. 3 is press-formed to produce a press-formed product shape 2 having the shape shown in FIG. 4. Here, draw forming was used as the press forming. A die model was set based on the die used in the press forming. The shape of the blank 1 is as shown in FIG. 3. The actual blank is the shape of a blank taken from a metal plate having a shape variation. The metal plate is a cold-rolled steel plate with a material strength of 1470 MPa and a thickness of 1.2 mm. This cold-rolled steel plate undergoes non-uniform volume expansion due to rapid cooling during water quenching, resulting in a wavy shape of the steel plate. This wavy shape is an irregular, uneven shape (see FIG. 12).

[0051] Here, the corrugation of the steel sheet due to the volume expansion causes dimensional fluctuations after pressing. Normal dimensional fluctuations occur when stress is released at the bottom dead center of the press, known as springback. However, with ultra-high strength steel sheets of 1470 MPa, dimensional fluctuations also occur due to the corrugation of the steel sheet. First, in the reference press-formed product shape acquisition step S1, a flat blank model was used and press-forming analysis was performed using the set die model. Then, the press-formed product shape 2 after demolding was acquired as the reference press-formed product shape. As described above, the press-forming analysis involves a CAE press-forming analysis and a subsequent springback analysis due to demolding. Then, the part shape after springback is acquired. The flat blank model has the same external shape as the blank, but with flat surfaces.

[0052] Furthermore, in the reference shape variation blank model generation step S3, in this example, a reference shape variation blank model that geometrically simulates an actual waviness shape was generated based on the first generation method described above. Specifically, in this example, the waviness shape of an actual steel sheet was measured, and the average values ​​of the pitch and amplitude of the irregularities were obtained. Median values ​​may be used instead of the average values. Then, a periodically changing wave shape with the obtained pitch and amplitude, as shown in FIG. 5, was imparted to a blank, thereby generating a reference shape variation blank model. The measurement position was the X-X cross section in FIG. 3, and the irregularities at that position were measured.

[0053] Next, in step S5, press forming analysis was performed using a die model set using the generated reference shape variation blank model. Then, the press-formed product shape 2 after demolding was acquired as the reference shape variation blank press-formed product shape 4. The reference shape variation blank press-formed product shape 4 is shown in FIG. 6. Next, the deviation amount between the reference press-formed product shape and the reference shape variation blank press-formed product shape 2 was calculated as the first deviation amount. The calculated positions were five locations A to E shown in FIG. 6 as representative positions. The calculated first deviation amounts were 2.5 mm at location A, -1.2 mm at location B, -0.7 mm at location C, 1.8 mm at location D, and -0.7 mm at location E. Note that in this example, the deviation amounts are calculated such that the deviation on the upper side of the press (upper side of the paper) relative to the reference press-formed product shape is positive, and the deviation on the lower side of the press (lower side of the paper) relative to the reference press-formed product shape is negative.

[0054] Next, in the deformed shape variation blank model generation step S9, in this embodiment, the reference shape variation blank model was divided into three regions A, B, and C along the longitudinal direction as shown in FIG. 7 . Then, as shown in FIG. 8 , three deformed shape variation blank models 5 were generated in which each region had a corrugated shape and the other regions were flattened. The three deformed shape variation blank models 5 are also referred to as deformed blank 1, deformed blank 2, and deformed blank 3, respectively. Deformed blank 1 is a blank model with a corrugated shape only in region A on the left end, as shown in FIG. 8( a). Deformed blank 2 is a blank model with a corrugated shape only in region B at the center, as shown in FIG. 8( b). Deformed blank 3 is a blank model with a corrugated shape only in region C on the right end, as shown in FIG. 8( c).

[0055] Next, in the deformed-shape-varying press-formed product shape acquisition step S11, press forming analysis was performed using the set die model for each of the three deformed-shape-varying blank models 5. Then, the press-formed product shapes after demolding were acquired as the deformed-shape-varying blank press-formed product shapes. Next, for each of the three deformed-shape-varying blank models 5, the deviation between the reference press-formed product shape and the deformed-shape-varying blank press-formed product shape was calculated as the second deviation amount. The calculated positions were the same five positions A to E as above. The calculated second deviation amounts were as follows: for deformed blank 1, 2.1 mm at position A, -1.1 mm at position B, -0.5 mm at position C, -0.2 mm at position D, and -0.1 mm at position E. For deformed blank 2, the deviations were 0.4 mm at position A, 0.3 mm at position B, -0.1 mm at position C, -0.3 mm at position D, and -0.1 mm at position E. In the deformed blank 3, the deformation was 0.1 mm at the site A, −0.3 mm at the site B, −0.1 mm at the site C, 2.3 mm at the site D, and −0.5 mm at the site E.

[0056] The results of the above deviation amounts are shown in Table 1. Here, the ALL column shows the first deviation amount from the reference shape variation press-formed product shape. Furthermore, the columns for deformed blanks 1 to 3 show the second deviation amount. The same applies below.

[0057]

[0058] Next, the factors behind the dimensional fluctuations in regions A to E (which position of the wave in blank 1 is the main factor) were evaluated. As can be seen from Table 1, the results for deformed blank 1 show that for regions A and B, the main factor is the wave shape of the blank corresponding to A and B. In other words, the results show that the wave-shaped region and the fluctuation position are the same.

[0059] In contrast, it can be seen that the cause of region C is not the wave position of deformed blank 2, which corresponds to region C, but the wave position of deformed blank 1. This is because the press-formed product has a curved shape. Furthermore, when the waves in deformed blank 1 flatten at the bottom dead center of the press during stress release due to springback attempt to return to their wave form, twists occur at positions A and B (the dimensional variation at A is negative, and B is positive). At the same time, it is presumed that position C is shifting toward the top of the page. This result shows that the position of the dimensional variation does not necessarily coincide with the wave position of the blank. One of the features of the present invention is to discover this phenomenon. Furthermore, it can be seen that the main cause of regions D and E is the waves at positions corresponding to the dimensional variation in deformed blank 3. From the above results, for example, if the dimensional variation at target dimensional variation locations A, B, and C is a problem in product production, it can be presumed that flattening the waves in deformed blank 1 (region A) is sufficient.

[0060] Next, we confirmed whether the estimation was correct. A blank was generated by flattening only the region A, which had a wavy shape in the deformed blank 1, compared to the reference shape variation blank 1. This blank is the improved shape variation blank 6, as shown in Figure 9. Then, using the improved shape variation blank 6, press molding analysis was performed using the set mold model. As a result, the press-formed product shape after demolding was obtained as the improved shape variation blank press-formed product shape. Then, for regions A to E, the deviation between the reference press-formed product shape and the improved shape variation blank press-formed product shape was calculated as the second deviation amount. The calculated second deviation amounts were -0.4 mm for region A, 0.6 mm for region B, -0.3 mm for region C, 1.7 mm for region D, and -0.3 mm for region E. The results are shown in Table 2.

[0061]

[0062] As can be seen from Table 2, by flattening the shape variation (wave shape) of the area A that was the cause, it was confirmed that not only the corresponding areas A and B but also area C could be improved.

[0063] Second Example Next, a second example will be described. The second example is similar to the first example, but the wavelength of the waveform given to the reference shape variation blank model generated in the reference shape variation blank model generation step S3 is reversed from that of the first example, as shown in FIG. 10(b). The waveform was measured at the X-X cross section position. Other than that, the same processing as in the first example was performed. The results are shown in Table 3.

[0064]

[0065] As can be seen from Tables 2 and 3, the fluctuation trends are similar to those in Example 1. However, because the wavelengths are reversed, the signs of the deviations are reversed. Furthermore, Table 3 shows that for regions A and B, the results for deformed blank 1 indicate that the main cause is the blank waves corresponding to A and B, and the wave and fluctuation positions are the same. On the other hand, for region C, it can be seen that the cause is the wave position of deformed blank 1, not deformed blank 2, which is the blank wave position corresponding to region C. This is because, since this is a curved part, twists occur at positions A and B (the dimensional fluctuation of A is positive, and B is negative) when the wave of deformed blank 1, which is flattened at the bottom dead center of the press during stress release due to springback, attempts to return to its wave form. At the same time, it can be seen that position C fluctuates toward the top of the page. This indicates that the fluctuations in the regions do not necessarily coincide with the wave position of the blank. It can also be seen that for regions D and E, the main cause is the waves at the positions corresponding to points.

[0066] Next, we confirmed whether the estimation was correct. For the reference shape variation blank 1, an improved shape variation blank 6 was generated by flattening only region A, which had a wavy shape in the deformed blank 1, as shown in FIG. 11 . Then, press molding analysis was performed using the improved shape variation blank 6 with the set mold model. As a result, the press-formed product shape after demolding was obtained as the improved shape variation blank press-formed product shape. The deviation between the reference press-formed product shape and the improved shape variation blank press-formed product shape for regions A to E was calculated as the second deviation amount. The calculated second deviation amounts were 0.4 mm for region A, −0.6 mm for region B, 0.3 mm for region C, −1.7 mm for region D, and 0.3 mm for region E. The results are shown in Table 4. From these results, for example, if the dimensional variations in regions A, B, and C are problematic in product production, flattening the wavy portion of the deformed blank 1 (region A) is sufficient, and the expected results were obtained.

[0067]

[0068] In actual production, the shape is corrected using a leveler or the like. However, the results of this example show that priority should be given to correcting the shape of the waves in the deformed blank 1 (area A), that is, both sides of the steel sheet, rather than the center. In this example, areas A and C are flattened, which is thought to be a good result in suppressing fluctuations in the part. This is because area B, i.e., the center of the steel sheet, has little effect on dimensional fluctuations.

[0069] [Third Example] In this example, as in the first example, the blank shown in FIG. 3 is pressed to form the press-formed product shape 2 shown in FIG. 4. Here, form forming is used as the press forming. A die model is set based on the die used in the press forming. The dimensional variation factor analysis method is performed in the same manner as in the first example, so details are omitted. However, in this example, the processing in step S3 for generating a reference shape variation blank model is different.

[0070] In the reference shape variation blank model generation step S3 of this example, a reference shape variation blank model was generated by applying an actual wave shape based on the second generation method described above. Specifically, in this example, the wave shape of an actual steel sheet was measured, and a wave shape based on the measured actual wave shape, such as that shown in FIG. 12(b), was applied to the blank to generate the reference shape variation blank model. The deviation between the reference press-formed product shape and the reference shape variation blank press-formed product shape was then calculated as the first deviation amount. The locations for which this deviation amount was calculated were five representative positions, A to E, as shown in FIG. 6 .

[0071] In this example, the first deviation amounts were 2.6 mm at portion A, -2.0 mm at portion B, -0.1 mm at portion C, 1.9 mm at portion D, and -2.3 mm at portion E. Note that the deviation values ​​in this example are calculated by taking the variation on the upper side of the press (upper side of the paper) relative to the standard press-formed product shape as a positive value and the variation on the lower side of the press (lower side of the paper) as a negative value. The second deviation amounts calculated in this example were as follows: For deformed blank 1, the deviations were 2.9 mm at portion A, -2.6 mm at portion B, 0.1 mm at portion C, 0.1 mm at portion D, and 1.3 mm at portion E. For deformed blank 2, the deviations were -0.2 mm at portion A, 0.1 mm at portion B, 0.2 mm at portion C, 1.0 mm at portion D, and -1.3 mm at portion E. In the deformed blank 3, the deviation was −0.1 mm at the portion A, 0.5 mm at the portion B, −0.3 mm at the portion C, 0.8 mm at the portion D, and −2.3 mm at the portion E. Table 5 shows the results of the deviation amounts.

[0072]

[0073] As can be seen from Table 5, the results of the deformed blank 1 show that the main cause of the portions A and B is the wave shape of the blank corresponding to A and B. In other words, the wave portion and the fluctuation position are the same results.

[0074] In contrast, it can be seen that the wave position of deformed blank 2, rather than deformed blank 3, which is the wave position of the blank corresponding to region D, is a major factor in region D. In this example, it is a curved part. Therefore, when the waves of deformed blank 2 are released from stress during springback, the flattened portion at the bottom dead center of the press attempts to return to its wave form. This is presumably because this affects the twist at region D. This also shows that the fluctuations in the target dimensional fluctuation region do not necessarily coincide with the wave position of the blank. Table 5 also shows that the target dimensional fluctuation region E can be improved by flattening the wave position of deformed blank 3. Furthermore, it can be seen that flattening the wave position of deformed blank 1 causes a deviation in the opposite direction of the fluctuation in region E, actually worsening the condition.

[0075] From these results, for example, if the dimensional variation of the target dimensional variation locations A and B is a problem in product production, it is estimated that the wave (region A) of the deformed blank 1 portion of the reference shape variation blank 3 can be flattened. To confirm this, an improved shape variation blank 6 was generated by flattening the wave (region A) of the deformed blank 1 portion of the reference shape variation blank 3, as shown in Figure 13. Then, press molding analysis was performed using the improved shape variation blank 6 with the set mold model. The shape of the press-formed product after demolding was then obtained as the improved shape variation blank press-formed product shape. The deviation between the reference press-formed product shape and the improved shape variation blank press-formed product shape for regions A to E was calculated as the second deviation. The calculated second deviations were -0.2 mm for region A, 0.2 mm for region B, 0.4 mm for region C, 1.5 mm for region D, and -3.6 mm for region E. The results are shown in Table 6.

[0076]

[0077] As can be seen from Table 6, improvements were obtained as expected for parts A and B. Furthermore, deterioration was observed as expected for part E. Furthermore, if, for example, the dimensional variations of parts D and E, which are the target dimensional variations, and especially the dimensional variations of part E, are problematic for product production, it can be seen from Table 5 that the waves in the deformed blank 3 can be flattened.

[0078] The results of verifying whether this idea was correct are shown in Figure 14 and Table 7. For this, an improved shape variation blank 6 was generated by flattening the waves in the deformed blank 3 portion of the reference shape variation blank 3, and press molding analysis was performed using the improved shape variation blank 6 with the set mold model. The shape of the press-formed product after demolding was then obtained as the improved shape variation blank press-formed product shape. The deviation between the reference press-formed product shape and the improved shape variation blank press-formed product shape for portions A to E was calculated as the second deviation amount. The calculated second deviation amounts were 2.9 mm for portion A, -2.2 mm for portion B, 0.2 mm for portion C, 0.3 mm for portion D, and 0.4 mm for portion E. The results are shown in Table 7.

[0079]

[0080] As can be seen from Table 7, the dimensional variation of portions D and E was improved as expected. In actual production, the shape is corrected using a leveler or the like. However, the results of this example show that it is better to prioritize the shape correction of the deformed blank portion, that is, both sides of the steel plate, rather than the center. In this example, regions A and C are flattened, which is thought to be a good result in suppressing variation in the part.

[0081] "Fourth Example" Next, a fourth example will be described. The fourth example is similar to the processing of the third example. However, draw forming is used as the press forming. In addition, in the reference shape variation blank model generation step S3 of this example, an actual wave shape was imparted to generate a reference shape variation blank model based on the second generation method described above. Specifically, in this example, the wave shape of an actual steel sheet was measured. Then, a wave shape based on the measured actual wave shape, such as that shown in Figure 15(b), was imparted to a blank to generate a reference shape variation blank model. The deviation amount between the reference press-formed product shape and the reference shape variation blank press-formed product shape was calculated as the first deviation amount. The calculated locations were five representative positions, A to E, shown in Figure 6. The other processing steps are the same as those of the third example and are therefore omitted. The calculated deviation amounts are shown in Table 8.

[0082]

[0083] As can be seen from Table 8, for the regions B to E, the results of Deformed Blank 1, Deformed Blank 2, and Deformed Blank 3 show that the waves in the blanks corresponding to the regions B to E are the main causes, respectively. In other words, the results show that the waves and the fluctuation positions are the same.

[0084] In contrast, it can be seen that the wave position of deformed blank 1, which is the wave position of the blank corresponding to region A, is not the only factor that determines region A's wave position, but also the wave position of deformed blank 3. This is because it is a curved part, and it is presumed that the twist that occurs when the wave of deformed blank 3, which is flattened at the bottom dead center of the press when stress is released during springback, tries to return to its wave form, affects the twist at position A on the stretch flange side of the tip of the part. This also shows that the fluctuation of the target dimensional fluctuation location does not necessarily coincide with the wave position of the blank.

[0085] From the results in Table 8, it can be seen that, for example, if the dimensional fluctuations at the target dimensional fluctuation locations D and E are problematic for product production, it is sufficient to flatten the waves at the deformed blank 3. We confirmed whether this idea was correct. An improved shape-varied blank 6 was generated by flattening the waves at the deformed blank 3 for the reference shape-varied blank 3. Then, press molding analysis was performed using the improved shape-varied blank 6 as shown in Figure 16 with the set mold model. The shape of the press-formed product after demolding was then acquired as the improved shape-varied blank press-formed product shape. The deviation between the reference press-formed product shape and the press-formed product shape using the improved shape-varied blank 6 was calculated as the second deviation for portions A to E. The calculated second deviations were 1.6 mm for portion A, -1.6 mm for portion B, 0.8 mm for portion C, 0.8 mm for portion D, and -0.5 mm for portion E. The results are shown in Table 9.

[0086]

[0087] As can be seen from Table 9, the dimensional variation of areas D and E improved as expected. However, the variation of area C worsened. In actual production, the shape is corrected using a leveler or the like. However, the results of this example show that priority should be given to correcting the shape of the wavy portion of the deformed blank 3 (area C), that is, both sides of the steel sheet, rather than the center. In this example, areas A and C are flattened, which is thought to be a good result in suppressing the variation of the part.

[0088] (Others) The present disclosure may also have the following configurations.(1) Disclosure 1 is an analysis method for identifying which portion of a blank's shape variation is a factor in a dimensional variation of a press-formed product formed by press-forming a blank having shape variation taken from a metal plate having shape variation using a press die, the method including: a reference press-formed product shape acquisition step for performing press-forming analysis using a flat blank model having a flat shape to perform press-forming with a die model set based on the target part shape, and acquiring the press-formed product shape after demolding as a reference press-formed product shape; a reference shape variation blank model generation step for generating a reference shape variation blank model that is a model of the blank having shape variation; a reference shape variation press-formed product shape acquisition step for performing press-forming analysis using the reference shape variation blank model to perform press-forming with the set die model, and acquiring the press-formed product shape after demolding as a reference shape variation blank press-formed product shape; a first deviation amount acquisition step for comparing the reference press-formed product shape and the reference shape variation blank press-formed product shape, and determining a deviation portion where the two shapes deviate and a first deviation amount that is the deviation amount; a deformed shape variation blank model generation step of generating a plurality of deformed shape variation blank models, which are models in which a portion of the blank with shape variation is changed to be flat, by changing the portion to be changed to be flat; a deformed shape variation press-formed product shape acquisition step of performing a press forming analysis using the deformed shape variation blank model to perform press forming with the set die model, and acquiring the press-formed product shape after demolding as the deformed shape variation blank press-formed product shape for each of the plurality of deformed shape variation blank models; a second deviation amount acquisition step of comparing the reference press-formed product shape with the deformed shape variation blank press-formed product shape, and determining the deviation portion where the two shapes deviate and the second deviation amount, which is the deviation amount, for each of the plurality of deformed shape variation blank models; a determining step of determining which portion of the blank having the shape variation is the main cause of the deviation between the reference press-formed product shape and the reference shape-varying blank press-formed product shape by comparing the first deviation amount with the second deviation amount at the same portion of the press-formed product shape.(2) Disclosure 2 discloses that the determining step determines a region in the same part having a wavy shape in the deformed shape variation blank model having a second deviation amount relatively close to the first deviation amount as a region of the shape variation that is the main cause of the shape variation for the same part. (3) Disclosure 3 discloses that the deformed shape variation blank model generating step divides the blank having shape variation into a plurality of regions, and generates, for each region, a blank model in which a portion other than the target region of the reference shape variation blank model is changed to be flat, as the deformed shape variation blank model. (4) Disclosure 4 discloses that the determining step identifies, from the deviation portion and the first deviation amount obtained in the first deviation amount obtaining step, a deviation portion where the absolute value of the first deviation amount is equal to or greater than a predetermined deviation threshold as a dimensional variation portion, compares, for each identified dimensional variation portion, a second deviation amount for each of the deformed shape variation blank models for the same portion as the dimensional variation portion with the first deviation amount, and determines, as the shape variation portion that is the main cause of the dimensional variation portion of the target dimensional variation portion, a region having a wave shape in the deformed shape variation blank model that has a second deviation amount that is relatively close to the first deviation amount. (5) Disclosure 5 discloses that the reference shape variation blank model generating step determines a pitch and an amplitude based on measured values ​​obtained by measuring the shape of an actual blank taken from a metal plate having shape variation, and generates, as the reference shape variation blank model, a blank model having a wave shape that periodically changes with the determined pitch and amplitude. (6) Disclosure 6 describes a method for generating a blank model having a waveform corresponding to the shape of the actual blank, the method comprising: measuring a shape of an actual blank sampled from a metal plate having shape variation; and generating a blank model having a waveform corresponding to the shape of the actual blank as the reference shape variation blank model based on the measurement results. (7) Disclosure 7 describes a method for generating a blank model having a waveform corresponding to the shape of the actual blank based on the measurement results. The first deviation amount acquisition step acquires, as the first deviation amount, a difference between a springback amount of a predetermined portion in the reference press-formed product shape and a springback amount of a predetermined portion in the reference shape variation blank press-formed product shape that is the same as the predetermined portion in the reference press-formed product shape. The second deviation amount acquisition step acquires, as the second deviation amount, a difference between a springback amount of a predetermined portion in the reference press-formed product shape and a springback amount of a predetermined portion in the deformed shape variation blank press-formed product shape that is the same as the predetermined portion in the reference press-formed product shape.(8) Disclosure 8 is an analysis device that identifies which part of the blank's shape variation is the cause of a dimensional variation in a press-formed product formed by press-forming a blank with shape variation taken from a metal plate with shape variation using a press die, the analysis device comprising: a reference press-formed product shape acquisition unit that performs press-forming analysis using a flat blank model with a flat shape to perform press-forming with a die model set based on the target part shape, and acquires the press-formed product shape after demolding as a reference press-formed product shape; a reference shape variation blank model generation unit that generates a reference shape variation blank model that is a model of the blank with shape variation; a reference shape variation press-formed product shape acquisition unit that performs press-forming analysis using the reference shape variation blank model to perform press-forming with the set die model, and acquires the press-formed product shape after demolding as a reference shape variation blank press-formed product shape; a first deviation amount acquisition unit that compares the reference press-formed product shape with the reference shape variation blank press-formed product shape, and determines a deviation portion where both shapes deviate and a first deviation amount that is the deviation amount; a deformed shape variation blank model generation unit that generates a plurality of deformed shape variation blank models, which are models in which a portion of the blank with shape variation is changed to be flat, by changing the portion to be changed to be flat; a deformed shape variation press-formed product shape acquisition unit that performs a process for each of the plurality of deformed shape variation blank models, using the deformed shape variation blank model to perform press forming analysis for press forming with the set die model, and acquiring the shape of the press-formed product after demolding as the deformed shape variation blank press-formed product shape; a second deviation amount acquisition unit that compares the reference press-formed product shape with the deformed shape variation blank press-formed product shape, and obtains the deviation portion where both shapes deviate and the second deviation amount, which is the deviation amount, for each of the plurality of deformed shape variation blank models; and a determination unit that determines which portion of the blank having the shape variation is the main cause of the deviation between the reference press-formed product shape and the reference shape-varying blank press-formed product shape by comparing the first deviation amount with the second deviation amount at the same portion of the press-formed product shape.(9) Disclosure 9 describes a method for determining whether a region in the same part having a wavy shape in the deformed shape variation blank model having a second deviation amount relatively close to the first deviation amount is a region of the shape variation that is a main cause of the shape variation in the same part. (10) Disclosure 10 describes a method for generating a deformed shape variation blank model in which the blank having a shape variation is divided into a plurality of regions, and a blank model in which a portion other than the target region of the reference shape variation blank model is changed to be flat for each region is generated as the deformed shape variation blank model. (11) Disclosure 11 describes the determination unit including: a dimension variation location identification unit that, from the deviation location and the first deviation amount obtained in the first deviation amount acquisition step, identifies a deviation location where the absolute value of the first deviation amount is equal to or greater than a predetermined deviation threshold as a dimension variation location; and a factor location determination unit that, for each identified dimension variation location, compares a second deviation amount for each of the deformed shape variation blank models for the same location as the dimension variation location with the first deviation amount, and determines a region having a wave shape in the deformed shape variation blank model having a second deviation amount relatively close to the first deviation amount as a shape variation location that is a main cause of the dimension variation location of the target dimension variation location. (12) Disclosure 12 describes the reference shape variation blank model generation unit that obtains a pitch and an amplitude from measured values ​​obtained by measuring the shape of an actual blank sampled from a metal plate having shape variation, and generates a blank model having a wave shape that periodically changes with the obtained pitch and amplitude as the reference shape variation blank model. (13) Disclosure 13 discloses that the reference shape variation blank model generation unit acquires measurement results of the shape of an actual blank taken from a metal plate having shape variation, and generates, based on the measurement results, a blank model having a wave shape that conforms to the shape of the actual blank as the reference shape variation blank model.(14) Disclosure 14 relates to a dimensional variation factor analysis program that causes a computer to function as the dimensional variation factor analysis device of the present disclosure, wherein the first deviation amount acquisition unit acquires, as the first deviation amount, a difference between an amount of springback of a predetermined portion in the reference press-formed product shape and an amount of springback of an identical portion of the reference press-formed product shape in the reference shape-variation blank press-formed product shape, and the second deviation amount acquisition unit acquires, as the second deviation amount, a difference between an amount of springback of a predetermined portion in the reference press-formed product shape and an amount of springback of an identical portion of the reference press-formed product shape in the deformed shape-variation blank press-formed product shape. (16) Disclosure 16 is a manufacturing method for a press-formed product, in which a blank taken from a metal plate having shape variations is press-formed using a press die to produce a press-formed product having a target part shape, the manufacturing method for a press-formed product comprising the dimensional variation factor analysis method disclosed herein, and performing shape correction on a portion of the blank that has been determined to be the main cause of deviation in the determination step before press forming.

[0089] The entire contents of Japanese Patent Application No. 2024-105059 (filed June 28, 2024), from which this application claims priority, are incorporated herein by reference. While the present invention has been described with reference to a limited number of embodiments, the scope of the invention is not limited thereto, and modifications of each embodiment based on the above disclosure will be obvious to those skilled in the art.

[0090] DESCRIPTION OF SYMBOLS 11 Dimensional variation factor analysis device 12 Display device 13 Input device 14 Storage device 15 Working data memory 20 Arithmetic processing unit 21 Reference press-formed product shape acquisition unit 22 Reference shape variation blank model generation unit 23 Reference shape variation press-formed product shape acquisition unit 24 First deviation amount acquisition unit 25 Deformed shape variation blank model generation unit 26 Deformed shape variation press-formed product shape acquisition unit 27 Second deviation amount acquisition unit 28 Determination unit 28A Dimensional variation location identification unit 28B Factor location determination unit S1 Reference press-formed product shape acquisition step S3 Reference shape variation blank model generation step S5 Reference shape variation press-formed product shape acquisition step S7 First deviation amount acquisition step S9 Deformed shape variation blank model generation step S11 Deformed shape variation press-formed product shape acquisition step S13 Second deviation amount acquisition step S15 Determination step S15A Dimensional variation location identification step S15B Causal location determination step

Claims

1. An analytical method for identifying which portion of a blank's shape variation is responsible for dimensional variation relative to a target part shape of a press-formed part formed by press-forming a blank with shape variation taken from a metal plate with shape variation using a press die, the method comprising: a reference press-formed part shape acquisition step of performing press-forming analysis using a flat blank model with a flat shape to press-form with a die model set based on the target part shape, and acquiring the press-formed part shape after demolding as a reference press-formed part shape; a reference shape variation blank model generation step of generating a reference shape variation blank model that is a model of the blank with shape variation; a reference shape variation press-formed part shape acquisition step of performing press-forming analysis using the reference shape variation blank model to press-form with the set die model, and acquiring the press-formed part shape after demolding as a reference shape variation blank press-formed part shape; a first deviation amount acquisition step of comparing the reference press-formed part shape and the reference shape variation blank press-formed part shape to determine the deviation portion where both shapes deviate and a first deviation amount that is the deviation amount; a deformed shape variation blank model generation step of generating a plurality of deformed shape variation blank models, which are models in which a portion of the blank with shape variation is changed to be flat, by changing the portion to be changed to be flat; a deformed shape variation press-formed product shape acquisition step of performing a press forming analysis using the deformed shape variation blank model to perform press forming with the set die model, and acquiring the press-formed product shape after demolding as the deformed shape variation blank press-formed product shape for each of the plurality of deformed shape variation blank models; a second deviation amount acquisition step of comparing the reference press-formed product shape with the deformed shape variation blank press-formed product shape, and determining the deviation portion where the two shapes deviate and the second deviation amount, which is the deviation amount, for each of the plurality of deformed shape variation blank models; a determining step of determining which portion of the blank having the shape variation is the main cause of the deviation between the reference press-formed product shape and the reference shape-varying blank press-formed product shape by comparing the first deviation amount with the second deviation amount at the same portion of the press-formed product shape.

2. A dimensional variation factor analysis method according to claim 1, wherein the determination step determines an area in the same part that has a wavy shape in the deformed shape variation blank model and that has a second deviation amount that is relatively close to the first deviation amount as the shape variation area that is the main cause for the same part.

3. A dimensional variation factor analysis method according to claim 1 or claim 2, wherein the deformed shape variation blank model generation step divides the blank having shape variation into a plurality of regions, and for each region, generates a blank model in which the portions other than the target region of the reference shape variation blank model are changed to be flat as the deformed shape variation blank model.

4. A method for analyzing the causes of dimensional variation according to any one of claims 1 to 3, wherein the determination step identifies, from the deviation portion and the first deviation amount obtained in the first deviation amount acquisition step, deviation portions where the absolute value of the first deviation amount is equal to or greater than a preset deviation threshold as dimensional variation portions, compares, for each identified dimensional variation portion, the second deviation amount for each of the deformed shape variation blank models for the same portion as the dimensional variation portion with the first deviation amount, and determines, as the shape variation portion that is the main cause of the dimensional variation portion in question, an area having a wave shape in the deformed shape variation blank model that has a second deviation amount that is relatively close to the first deviation amount.

5. A dimensional variation factor analysis method according to any one of claims 1 to 4, wherein the reference shape variation blank model generation step determines pitch and amplitude based on measurements of the shape of an actual blank taken from a metal plate with shape variation, and generates a blank model having a wave shape that changes periodically with the determined pitch and amplitude as the reference shape variation blank model.

6. A dimensional variation factor analysis method according to any one of claims 1 to 4, wherein the reference shape variation blank model generation step measures the shape of an actual blank taken from a metal plate having shape variation, and generates, based on the measurement results, a blank model having a wave shape that conforms to the shape of the actual blank as the reference shape variation blank model.

7. A method for analyzing factors of dimensional variation as claimed in any one of claims 1 to 6, wherein the first deviation amount acquisition step acquires as the first deviation amount the difference between the amount of springback of a predetermined portion in the reference press-formed product shape and the amount of springback of a portion in the reference shape-variation blank press-formed product shape that is the same as the predetermined portion of the reference press-formed product shape, and the second deviation amount acquisition step acquires as the second deviation amount the difference between the amount of springback of a predetermined portion in the reference press-formed product shape and the amount of springback of a portion in the deformed shape-variation blank press-formed product shape that is the same as the predetermined portion of the reference press-formed product shape.

8. An analysis device that identifies which part of the blank's shape variation is the cause of dimensional variation relative to a target part shape of a press-formed part formed by press-forming a blank with shape variation taken from a metal plate with shape variation using a press die, the device comprising: a reference press-formed part shape acquisition unit that performs press-forming analysis using a flat blank model with a flat shape to perform press-forming with a die model set based on the target part shape, and acquires the press-formed part shape after demolding as a reference press-formed part shape; a reference shape variation blank model generation unit that generates a reference shape variation blank model that is a model of the blank with shape variation; a reference shape variation press-formed part shape acquisition unit that performs press-forming analysis using the reference shape variation blank model to perform press-forming with the set die model, and acquires the press-formed part shape after demolding as a reference shape variation blank press-formed part shape; a first deviation amount acquisition unit that compares the reference press-formed part shape with the reference shape variation blank press-formed part shape, and determines the deviation part where both shapes deviate and a first deviation amount that is the deviation amount; a deformed shape variation blank model generation unit that generates a plurality of deformed shape variation blank models, which are models in which a portion of the blank with shape variation is changed to be flat, by changing the portion to be changed to be flat; a deformed shape variation press-formed product shape acquisition unit that performs a process for each of the plurality of deformed shape variation blank models, using the deformed shape variation blank model to perform press forming analysis for press forming with the set die model, and acquiring the shape of the press-formed product after demolding as the deformed shape variation blank press-formed product shape; a second deviation amount acquisition unit that compares the reference press-formed product shape with the deformed shape variation blank press-formed product shape, and obtains the deviation portion where both shapes deviate and the second deviation amount, which is the deviation amount, for each of the plurality of deformed shape variation blank models; and a determination unit that determines which portion of the blank having the shape variation is the main cause of the deviation between the reference press-formed product shape and the reference shape-varying blank press-formed product shape by comparing the first deviation amount with the second deviation amount at the same portion of the press-formed product shape.

9. The dimensional variation factor analysis device according to claim 8, wherein the determination unit determines that an area in the same part having a wavy shape in the deformed shape variation blank model having a second deviation amount that is relatively close to the first deviation amount is the main cause of shape variation for the same part.

10. A dimensional variation factor analysis device as described in claim 8 or claim 9, wherein the deformed shape variation blank model generation unit divides the blank having shape variation into a plurality of regions, and for each region, generates a blank model in which the portions other than the target region of the reference shape variation blank model are changed to be flat as the deformed shape variation blank model.

11. The dimensional variation factor analysis device according to any one of claims 8 to 10, wherein the determination unit comprises: a dimensional variation part identification unit that, from the deviation part and the first deviation amount obtained in the first deviation amount acquisition step, identifies a deviation part where the absolute value of the first deviation amount is equal to or greater than a preset deviation threshold as a dimensional variation part; and a factor part determination unit that, for each identified dimensional variation part, compares the second deviation amount for each of the deformed shape variation blank models for the same part as the dimensional variation part with the first deviation amount, and determines that a region having a wavy shape in the deformed shape variation blank model that has a second deviation amount relatively close to the first deviation amount is the shape variation part that is the main cause of the dimensional variation part in question.

12. A dimension variation factor analysis device according to any one of claims 8 to 11, wherein the reference shape variation blank model generation unit determines pitch and amplitude from measurements obtained by measuring the shape of an actual blank taken from a metal plate with shape variation, and generates a blank model having a wave shape that changes periodically with the determined pitch and amplitude as the reference shape variation blank model.

13. A dimensional variation factor analysis device according to any one of claims 8 to 12, wherein the reference shape variation blank model generation unit acquires measurement results of the shape of an actual blank taken from a metal plate having shape variation, and generates, based on the measurement results, a blank model having a wave shape that conforms to the shape of the actual blank as the reference shape variation blank model.

14. A dimensional variation factor analysis device according to any one of claims 8 to 13, wherein the first deviation amount acquisition unit acquires as the first deviation amount the difference between the amount of springback of a specified portion in the reference press-formed product shape and the amount of springback of a portion in the reference shape-variation blank press-formed product shape that is the same as the specified portion of the reference press-formed product shape, and the second deviation amount acquisition unit acquires as the second deviation amount the difference between the amount of springback of a specified portion in the reference press-formed product shape and the amount of springback of a portion in the deformed shape-variation blank press-formed product shape that is the same as the specified portion of the reference press-formed product shape.

15. A dimensional variation factor analysis program that causes a computer to function as the dimensional variation factor analysis device according to any one of claims 8 to 14.

16. A method for manufacturing a press-formed product, in which a blank taken from a metal plate having shape variations is press-formed using a press die to produce a press-formed product having a target part shape, the method comprising the dimensional variation factor analysis method set forth in any one of claims 1 to 7, and performing shape correction on the portion of the blank that has been determined to be the main cause of deviation in the determination step before press forming.

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