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

Abstract

Press forming analysis is used to identify which part of a blank with shape variation is the cause of the dimensional variation due to shape variation. A reference press-formed product shape is acquired, and a reference shape-variant blank press-formed product shape is acquired. The deviation part and first deviation amount between the reference press-formed product shape and the reference shape-variant blank press-formed product shape are determined. Multiple deformed shape-variant blank models, which are models in which a portion of the blank with shape variation is flattened, are also generated, and the deformed shape-variant blank press-formed product shape is obtained for each deformed shape-variant blank model. The deviation part and second deviation amount between the reference press-formed product shape and each deformed shape-variant blank press-formed product shape are then determined. The first deviation amount and second deviation amount are then compared to determine which part of the blank with shape variation is the main cause of the deviation.

Description

[Technical Field]

[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] 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 is also applicable to iron alloys such as stainless steel, as well as non-ferrous materials and non-metallic materials. [Background technology]

[0003] When a cold-rolled steel sheet is water-quenched, its volume expands due to rapid cooling. As a result, the cold-rolled steel sheet becomes wavy. As such, the metal sheet to be press-formed and the blank cut from the metal sheet are not completely flat, and may have a wavy shape (shape variation). When a blank having this corrugated shape is pressed, the shape variation affects the dimensional variation of the press-formed product after pressing. A blank having a corrugated shape is a blank with shape variation. There is a concern that this shape variation may cause the manufactured press-formed product to deviate from the target dimensional accuracy. In particular, for cold-rolled steel sheets with high strengths of 1470 MPa or higher, the adverse effect of shape variation on the dimensional accuracy of the press-formed product becomes significant.

[0004] Conventionally, an analysis method for predicting the influence of shape variations is disclosed in, for example, 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 method then determines the position and amount of deviation between the two shapes. The method also compares 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 that has the same amplitude as the corrugated shape but a different period. The method then determines the position and amount of deviation between the two shapes. Patent Document 1 then 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 fluctuations are a concern). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-103926 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, the shape of a press-formed product made from a flat blank model is compared with the shape of a press-formed product made from a corrugated blank model, and areas where there is a large amount of deviation 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 wave shapes of other parts may affect the deviation of the part with a large deviation amount. Therefore, even if the shape of only the part requiring measures specified in Patent Document 1 is improved, the effect of improving the dimensional variation may be small.

[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. [Means for solving the problem]

[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 the 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; The dimensional variation factor analysis method includes a second deviation amount acquisition step of comparing the first deviation amount with the deformed shape variation blank press-formed product shape and determining the deviation area where the two shapes deviate and the second deviation amount, which is the deviation amount, for each of the multiple deformed shape variation blank models; and a determination step of comparing the first deviation amount with the second deviation amount at the same area of the press-formed product shape to determine which area 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. [Effects of the Invention]

[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, according to the present invention, it becomes possible to know which position of the blank should be focused on for shape correction. As a result, it becomes possible to more effectively prevent a decrease in yield due to shape defects. [Brief explanation of the drawings]

[0011] [Figure 1] 5A to 5C are diagrams illustrating the processing of a dimension variation factor analysis method according to an embodiment of the present invention. [Figure 2] 1 is a conceptual diagram illustrating a dimension variation factor analysis device according to an embodiment of the present invention. [Figure 3] FIG. 10 is a diagram illustrating the shape of a reference variable shape blank having a shape variation used in the examples. [Figure 4] FIG. 1 is a diagram showing a press-formed product shape (target part shape) targeted in an embodiment. [Figure 5] FIG. 3 is a conceptual diagram illustrating a waveform that changes periodically at a predetermined pitch and amplitude, which is set (given) to a reference shape variation blank model in the first embodiment. [Figure 6] FIG. 10 is a diagram showing the shape of a press-formed product with reference shape variation and the positions of portions A to E. [Figure 7] FIG. 10 is a diagram illustrating division of regions in an embodiment. [Figure 8] 1A and 1B are diagrams illustrating a deformed shape variation blank model (deformed blank) in an embodiment. (a) is a diagram illustrating a deformed blank 1 in which all areas except region A are flattened. (b) is a diagram illustrating a deformed blank 2 in which all areas except region B are flattened. (c) is a diagram illustrating a deformed blank 3 in which all areas except region C are flattened. [Figure 9] FIG. 2 is a diagram illustrating an improved shape variation blank model in the first embodiment. [Figure 10]FIG. 10 is a conceptual diagram illustrating a waveform that changes periodically at a predetermined pitch and amplitude, which is set (given) to a reference shape variation blank model in a second embodiment. [Figure 11] FIG. 10 is a diagram illustrating an improved shape variation blank model in the second embodiment. [Figure 12] FIG. 11 is a conceptual diagram illustrating a wave shape that follows the shape variation of an actual blank and is set (given) to a reference shape variation blank model in a third embodiment. [Figure 13] FIG. 11 is a diagram illustrating an improved shape variation blank model in the case of deterioration in the third embodiment. [Figure 14] FIG. 11 is a diagram illustrating an improved shape variation blank model in the case of improvement in the third embodiment. [Figure 15] FIG. 13 is a conceptual diagram illustrating a wave shape that follows the shape variation of an actual blank and is set (given) to a reference shape variation blank model in a fourth embodiment. [Figure 16] FIG. 13 is a diagram illustrating an improved shape variation blank model in the case of improvement in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (way of thinking) This embodiment is based on the following idea, for example. First, a reference variable shape blank model with a geometrically corrugated shape is generated based on a blank with shape variations. Then, press forming analysis is performed using CAE using this blank model. Also, a flat blank model of a flat blank is generated. Then, press forming analysis is performed using CAE using this blank model. Then, the shapes of the two press-formed products are compared, and areas (regions) with large deviations are identified as areas of concern regarding variation. Note that it is necessary to reduce the amount of deviation in these areas. Furthermore, areas of concern regarding variation are areas 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 that has shape variations only in each region and has 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 variable shape blank model with a flattened portion. That is, for each partially flattened variable shape blank model, the press-formed product shapes of both are compared, and the amount of deviation at the identified variation concern area is determined. Then, based on the amount of deviation 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] (composition) "First embodiment" In the manufacturing of the press-formed product according to this embodiment, a blank with a shape variation taken from a metal plate with a shape variation (unevenness) is used. In this embodiment, the blank is press-formed (press working) using a press die corresponding to the target shape of the press-formed product. This is assumed to be a case in which the press-formed product is manufactured. Press forming includes forming and draw forming. In this embodiment, the present invention provides a dimensional variation factor analysis method for identifying (evaluating) which part of a blank with shape variation is the cause of the dimensional variation of the press-molded product relative to the target part shape when the press-molded product is manufactured. Here, the shape variation of the metal plate and the blank refers to, for example, a shape variation in which unevenness is continuously formed along a predetermined direction. The blank is cut into a desired contour shape for press forming.

[0015] Examples of the target metal sheet material include steel and aluminum alloy. However, the material is not limited to these. The present invention is a technology suitable for high-strength steel sheets with a tensile strength of 980 MPa or more, particularly ultra-high-strength steel sheets with a tensile strength of 1470 MPa or more. When the tensile strength of a metal sheet is high, the influence of shape variations of the metal sheet or blank on dimensional accuracy is greater than when the tensile strength is low. As shown in Figure 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 judgment step S15.

[0016] <Step S1: Obtaining the standard press-molded product shape> 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 press-forming is performed with a die model set based on the target part shape, and 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 the actual die that press-forms the flat blank into the target part shape. For example, the set die model is a die model that follows the target part shape. However, a die model that is corrected for springback after demolding is preferable 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 demolding, i.e., after springback. The flat blank model is a blank model that has been generally used in press forming analysis and has a flat shape without any irregularities. That is, the flat blank model is a model of a blank that has been used in the target press forming by changing the wave shape (shape variation) of the blank into 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 structural analysis using a computer, 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 shape of the reference press-molded product after demolding, which is determined by press molding analysis, has a change amount due to demolding from the bottom dead center of molding.

[0019] The amount of change is the value obtained by subtracting the height of each part of the press-formed product shape after it is released from the mold and springs back in the press-forming direction from the height of the corresponding part of the shape at the bottom dead center of the press. 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 generating step S3 is a step of generating a reference shape variation blank model, which is a model of a blank having a shape variation. The reference shape variation blank model is a blank model having a wave shape (shape variation) corresponding to the shape variation of an actual metal plate having shape variation. In the reference shape variation blank model generation step S3, a reference shape variation blank model is generated based on measurement data obtained by measuring the shape of an actual blank sampled from a predetermined position on a metal plate having shape variation. The shape of the actual blank is measured using a three-dimensional shape measuring device using, for example, a laser rangefinder. The actual blank usually has irregular irregular shapes as shown in FIG. 12(b). In this embodiment, the shape variation (wave shape) to be imparted to the blank model is determined by one of the following two generation methods.

[0021] [First generation method] In the first generation method, the shape of the 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. This processing determines the set pitch and set amplitude. Then, a waveform that periodically changes at the determined set pitch and set amplitude is given as the shape variation. The waveform imparted by the first generation method is as shown in FIG. The actual blank to be measured does not have to be the blank itself to be used in press working. Metal sheets manufactured using the same equipment tend to exhibit similar shape variations. It is preferable that the metal sheet to be measured be manufactured under the same manufacturing conditions as the metal sheet to be pressed. 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 produced in 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 uneven shape, such as that shown in Figure 12(b).

[0023] <Step S5: Obtaining the press-molded product shape with reference shape variation> In the reference shape variation press-formed product shape acquisition step S5, a press forming analysis is performed using the reference shape variation blank model to perform press forming with the set die model, and the shape of the press-formed product after demolding is acquired as the reference shape variation blank press-formed product shape. As described above, the 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.

[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-varying blank press-formed product shape. The first deviation amount acquisition step S7 is a step of determining, from the comparison, deviation portions where the two shapes deviate and the deviation amounts as first deviation amounts. For example, a plurality of regions are set for the shape of the press-formed product. Then, a representative portion of each region is set as the portion for which the deviation amount is to be calculated. The region may be set as a representative region where springback is likely to occur after demolding. Also, for example, it is advisable to store data by pairing the deviation portion and the first deviation amount.

[0025] In this embodiment, the shape of the press-formed product at the bottom dead center of forming was used as the reference shape. The amount of change (springback amount) from the reference shape at each part of the shape of the press-formed product after demolding was calculated. The difference in the amount of change between the two press-formed product shapes was calculated as the deviation amount. The same applies to the second deviation amount acquisition step S13 described below. That is, the first actual deviation amount is a value obtained by subtracting the amount of change in the reference press-formed product shape from the amount of change in the reference shape variation blank press-formed product shape. The amount of change in the reference shape variation 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, when the first actual deviation amount is + (plus), the corresponding portion of the reference shape variation blank press-formed product shape will have a convex shape compared to the reference press-formed product shape. On the other hand, when the first actual deviation amount is - (minus), the corresponding portion of the reference shape variation 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 be flat. The deformed shape variation blank model generation step S9 generates a plurality of 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 some 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 changed to be flat is generated as a deformed shape variation blank model 5 (see FIG. 8). That is, 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 a plurality of 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. Furthermore, the sizes of the regions do not need to be equal. Furthermore, in this embodiment, from the data of "deviation location and first deviation amount" obtained in the first deviation amount acquisition step S7, deviation locations where the first deviation amount is a deviation amount equal to or greater than a predetermined amount are obtained as variation concern locations. Then, each of the above regions may be set so as to include a respective variation concern location. For example, a 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] <Deformation shape variation press-molded product shape acquisition step S11> The deformed-shape-varying press-formed product shape acquisition step S11 performs press-forming analysis using the deformed-shape-varying blank model 5 and the set die model. The deformed-shape-varying blank press-formed product shape acquisition step S11 is a processing step for acquiring the deformed-shape-varying blank press-formed product shape after mold release. The deformed-shape-varying blank press-formed product shape acquisition step S11 executes processing for acquiring 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 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.

[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 second deviation amount is obtained in the same manner as in the first deviation amount obtaining step S7.

[0031] <Determination Step S15> In the determination step S15, the first deviation amount and the second deviation amount at the same portion of each press-formed product shape are compared, and based on the 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 press-formed product shape of the blank with shape variation. The main cause of the deviation is determined, for example, as follows. In the determination step S15 of this embodiment, a deformed shape variation blank model 5 having one or more second deviation amounts relatively close to the first deviation amount is identified for the same part. Then, a region having a wave shape in the identified deformed shape variation blank model 5 is determined to be a shape variation portion that is the main cause for the same part. 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. Furthermore, the adjustment may be performed only on the parts where the first deviation amount is equal to or greater than a predetermined amount, among the parts where strict requirements are imposed by the customer. The determining step S15 of this embodiment includes, for example, a dimension variation location specifying step and a factor location determining step S15B.

[0032] [Dimensional variation location identification step S15A] The dimension variation location identifying step S15A is a step of identifying a deviation location where the absolute value of the first deviation amount is equal to or greater than a preset deviation threshold value from the deviation location obtained in the first deviation amount obtaining step S7 and the first deviation amount, and identifying the identified deviation location as a dimension variation location.

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

[0034] (Method of manufacturing press-molded products) 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, the blank portion determined to be the main cause of deviation in the determination step S15 of the dimensional variation factor analysis method of this embodiment is subjected to intensive shape correction. The shape correction is a process of intensively flattening the shape variation of the blank portion determined to be the main cause of deviation. The blank is then press formed into the desired part shape. This makes it possible to more efficiently reduce dimensional variations and manufacture press-formed products 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 an apparatus, a dimensional variation factor analysis apparatus 11, will be described in this embodiment. As shown in FIG. 2, the dimension 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 an arithmetic processing unit 20. The display device 12, input device 13, storage device 14 and working data memory 15 are connected to a processing unit 20, and each function is executed in response to a command from the processing unit 20.

[0036] ≪Display device 12≫ The display device 12 is used to display the analysis results and is configured with a liquid crystal monitor or the like. <Input Device 13> The input device 13 is used for displaying instructions for blanks, press-molded products, etc., and for inputting conditions by 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 the shape file 30 of the blank and press-molded product, and is configured with a hard disk or the like. <Working Data Memory 15> The working data memory 15 is used for temporary storage of data used in the arithmetic processing unit 20 and for calculations, and is composed of RAM (Random Access Memory) and the like.

[0037] <Arithmetic processing unit 20> 2, the arithmetic 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 arithmetic processing unit 20 includes a CPU (Central Processing Unit) such as a PC, and a storage unit in which predetermined programs for processing the functions of each unit are stored. Each of the above units functions when the CPU executes the predetermined programs. The functions of the above-mentioned components in the arithmetic processing unit 20 will be explained below.

[0038] <Standard press-molded 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, and then performs processing 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 generating unit 22 executes the reference shape variation blank model generating 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, and then executes processing to obtain 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 determines the pitch and amplitude from measurements of the shape of an actual blank taken from a metal plate with shape variation, for example, and generates a blank model having a wave shape that periodically changes with the determined pitch and amplitude as a reference shape variation blank model. Furthermore, the reference shape variation blank model generation unit 22 acquires measurement results, for example, by measuring the shape of an actual blank taken from a metal plate having shape variation, and generates a blank model having a waveform conforming to the shape of the actual blank as the reference shape variation blank model based on the measurement results.

[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 of generating 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 performs press forming analysis using the reference shape variation blank model to perform press forming with the set die model, and then executes processing to acquire the shape of the press-formed product after mold release as the reference shape variation blank press-formed product shape.

[0041] <First deviation amount acquisition unit 24> The first deviation amount acquiring section 24 executes the first deviation amount acquiring 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-varying blank press-formed product shape, and executes a process of determining deviation portions 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 specified portion in the standard press-formed product shape and the springback amount of the same portion as the specified portion in the standard press-formed product shape in the standard shape variation blank press-formed product shape.

[0042] <Deformed shape variation blank model generation unit 25> The deformed shape variation blank model generating unit 25 executes the deformed shape variation blank model generating step S9 described in the first embodiment. The deformed shape variation blank model generation unit 25 executes a process of generating a plurality of deformed shape variation blank models 5, which are models in which a part of a blank with a shape variation is changed to be flat, by changing the part to be flat. The deformed shape variation blank model generation unit 25, for example, divides the blank having a shape variation into a plurality of regions, and generates, for each region, a blank model in which the 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 5.

[0043] <Deformation shape variation 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-varying press-formed product shape acquisition unit 26 performs press-forming analysis of press-forming with the set die model using the deformed-shape-varying blank model 5. Then, a process of acquiring the shape of the press-formed product after demolding as the deformed-shape-varying blank press-formed product shape is performed for each of the plurality of deformed-shape-varying 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-varying blank press-formed product shape. Then, it executes a process to obtain the deviation portion where the two shapes deviate and the second deviation amount, which is the deviation amount. This process is executed for each of the multiple deformed-shape-varying blank models 5. In this embodiment, the second deviation amount is the difference between the springback amount of a specified portion in the standard press-formed product shape and the springback amount of the same portion as the specified portion in the standard press-formed product shape in the deformed shape variation blank press-formed product shape.

[0045] <Judgment section 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 with the second deviation amount at the same portion of the press-formed product shape. Through this comparison, a process is executed to determine 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. The determination unit 28 determines, for example, a region having a wavy shape in the deformed shape variation blank model 5 having one or more second deviation amounts relatively close to the first deviation amount for the same part as the shape variation part that is the main cause for the same part. 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 dimension variation location specifying unit and a factor location determining unit 28B.

[0046] [Dimensional variation location identification unit 28A] The dimension variation location identifying unit 28A performs a process of identifying, from the deviation location and the first deviation amount obtained by the first deviation amount acquisition unit 24, a deviation location where the absolute value of the first deviation amount is equal to or greater than a preset deviation threshold, as a dimension variation location. [Factor site determination unit 28B] For each identified dimensional variation location, the factor location determination unit 28B compares the second deviation amount and the first deviation amount for the same location as the dimensional variation location for each of the deformed shape variation blank models 5. Then, it determines that an area having a wavy shape in the deformed shape variation blank model 5 that has one or more second deviation amounts that are relatively close to the first deviation amount is the shape variation location that is the main cause 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 dimension variation factor analysis device 11 of this embodiment is realized by the CPU executing a predetermined program. Therefore, the dimensional variation factor analysis program of the present invention can be specified as causing 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 judgment unit 28.

[0048] (Operation etc.) For example, consider the case where multiple press-formed parts are stacked and joined together to assemble members of a vehicle body. In such cases, if there is a large deviation in the shapes of the press-formed parts, it becomes difficult to join the press-formed parts together. This effect is particularly significant when the deviation is large in flanges, etc. In such cases, countermeasures may be required. Flanges are often used as joining points. In this embodiment, a portion that is expected to be significantly affected by the shape variation of the blank, that is, a portion that is expected to have a large deviation, is identified as a dimensional variation portion. Here, the deviation at the dimensional variation location may not be the main cause of the dimensional variation in the blank having shape variation, because the position of the corrugated shape (shape variation) corresponding to the dimensional variation location is not necessarily the location requiring countermeasures. In some cases, it is expected that flattening the corrugated shape at the location corresponding to the dimensional variation location in the actual blank will increase the deviation at the dimensional variation location.

[0049] Therefore, in this embodiment, a plurality of deformed shape fluctuation blank models 5 with limited waveform regions are used to determine which region of the waveform affects the deviation at the target dimensional fluctuation location. This makes it possible to more accurately determine the areas requiring countermeasures for each dimensionally varied portion. Then, for the dimensional variation areas that require improvement, we improve the shape variation of the blank areas that are the cause of the dimensional variation areas. This makes it possible to more effectively reduce the dimensional variation. For example, this can be done by concentrating and flattening the waves in the blank, which are the main cause of the variation. [Example]

[0050] An example for confirming the action and effect of this embodiment will be described. "First Example" In this example, we 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 shown in Fig. 4. In this example, 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 blank 1 is as shown in Figure 3. The actual blank is a blank taken from a metal plate with a variable shape. 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 Figure 12).

[0051] Here, the corrugated shape of the steel sheet caused by the volume expansion mentioned above causes dimensional fluctuations after pressing.Normally, dimensional fluctuations occur when stress is released at the bottom dead center of the press, a process known as springback, but with ultra-high strength steel sheet of 1470 MPa, dimensional fluctuations also occur due to the corrugation of the steel sheet, which is a distinctive feature. First, in step S1 of acquiring the reference press-formed product shape, 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 described above, but has a flat surface.

[0052] In addition, in the reference shape variation blank model generation step S3, in this embodiment, 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 embodiment, 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 waviness shape with the obtained pitch and amplitude, as shown in FIG. 5, was imparted to a blank, and a reference shape variation blank model was generated. The measurement position was the XX cross section in FIG. 3, and the unevenness at that position was 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 obtained as reference shape variation blank press-formed product shape 4. The reference shape variation blank press-formed product shape 4 is shown in Figure 6. Next, the deviation between the reference press-formed product shape and the reference shape variation blank press-formed product shape 2 was determined as a first deviation amount. The deviation amount was determined at five representative locations, A to E shown in FIG. The first deviations obtained were 2.5 mm at site A, −1.2 mm at site B, −0.7 mm at site C, 1.8 mm at site D, and −0.7 mm at site E. In this example, the deviation values are calculated by taking the variation on the upper side of the press (upper side of the paper) as positive and the variation on the lower side of the press (lower side of the paper) as negative relative to the standard press-molded product shape.

[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 only each region had a corrugated shape and the other parts 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. The deformed blank 1 is a blank model having a wave shape only in region A on the left end side, as shown in FIG. 8(a). The deformed blank 2 is a blank model with a wave shape only in the central region B, as shown in Figure 8(b). The deformed blank 3 is a blank model having a wave shape only in region C on the right end side, as shown in FIG. 8(c).

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

[0056] Table 1 shows the results of the above deviations. Here, the column for ALL displays the first deviation amount from the reference shape variation press-formed product shape, and the columns for deformed blanks 1 to 3 display the second deviation amount, and so on.

[0057] [Table 1]

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

[0059] In contrast, it can be seen that the cause of region C is not the wave position of deformed blank 2, which is the wave position of the blank corresponding to region C, but the wave position of deformed blank 1. This is because the press-formed product shape is a curved part. When the waves in deformed blank 1 are flattened at the bottom dead center of the press during stress release due to springback, twists occur at positions A and B (the dimensional variation at A is negative, and B is positive) as they attempt to return to their wave form. At the same time, it is estimated that this indicates that position C has shifted toward the top of the paper. 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 the deformation in parts D and E is the waves at the positions corresponding to the dimensional fluctuations in the deformed blank 3. From the above results, it can be estimated that if the dimensional fluctuations at the target dimensional fluctuation locations A, B, and C are a problem in terms of product production, the waves in the deformed blank 1 (region A) should be flattened.

[0060] Next, we checked whether the assumption was correct. A blank was generated by flattening only the region A that 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 this improved shape variation blank 6, press forming analysis was performed with the set die model. As a result, the shape of the press-formed product after demolding was obtained as the shape of the improved shape variation blank press-formed product. Then, for the portions A to E, the deviation between the reference press-formed product shape and the improved shape variation blank press-formed product shape was determined as a second deviation. The second deviation amounts obtained were -0.4 mm at site A, 0.6 mm at site B, -0.3 mm at site C, 1.7 mm at site D, and -0.3 mm at site E. The results are shown in Table 2.

[0061] [Table 2]

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

[0063] "Second Example" Next, a second embodiment will be described. The second embodiment is similar to the first embodiment, 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 embodiment, as shown in Figure 10(b). The waveform is measured at the XX cross section position. Other processes were performed in the same manner as in the first embodiment. The results are shown in Table 3.

[0064] [Table 3]

[0065] As can be seen from Tables 2 and 3, the tendency of the fluctuations is the same as in Example 1. However, since the wavelengths are reversed, the signs of the deviation amounts are reversed. Furthermore, from Table 3, it can be seen that for parts A and B, the results of deformation blank 1 show that the main cause is the wave of the blank corresponding to A and B, and the wave and the deformation position are the same results. On the other hand, it can be seen that the cause of part C is not the wave position of deformed blank 2, which is the wave position of the blank corresponding to part C, but the wave position of deformed blank 1. This is because it is a curved part, and when the waves of deformed blank 1 are released from stress during springback and the part that was flattened at the bottom dead center of the press tries to return to its wave form, twists occur at positions A and B (the dimensional variation of A is positive, and B is negative). At the same time, it shows that position C has fluctuated toward the top of the page. In other words, this shows that the variation in the part does not necessarily coincide with the wave position of the blank. It can also be seen that the main cause of the damage to parts D and E is the waves at the positions corresponding to the points.

[0066] Next, we checked whether the assumption was correct. As shown in Figure 11, an improved shape variation blank 6 was generated by flattening only the region A where a wavy shape existed in the deformed blank 1, compared to the reference shape variation blank 1. Then, press forming analysis was performed using the set die model using this improved shape variation blank 6. As a result, the shape of the press-formed product after demolding was obtained as the shape of the improved shape variation blank press-formed product. Then, for the portions A to E, the deviation between the reference press-formed product shape and the improved shape variation blank press-formed product shape was determined as a second deviation. The second deviation amounts obtained were 0.4 mm at site A, −0.6 mm at site B, 0.3 mm at site C, −1.7 mm at site D, and 0.3 mm at site E. The results are shown in Table 4. From these results, for example, if the dimensional variations in parts A, B, and C are a problem in terms of product production, it is sufficient to flatten the waves in the deformed blank 1 part (area A), and the expected results were obtained.

[0067] [Table 4]

[0068] In actual production, the shape is corrected using a leveler or similar tool. However, the results of this example show that priority should be given to correcting the waves in the deformed blank 1 (area A), that is, the shape on 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, 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 a 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 was performed in the same manner as in the first embodiment, so details are omitted. However, in this embodiment, the processing of the reference shape variation blank model generation step S3 is different.

[0070] In the reference shape variation blank model generating step S3 of this embodiment, an actual corrugation shape was imparted to generate a reference shape variation blank model based on the second generation method described above. Specifically, in this embodiment, the corrugation shape of an actual steel sheet was measured, and a corrugation shape based on the measured actual corrugation shape as shown in Fig. 12(b) was imparted 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 determined as a first deviation amount, and the deviation amount was determined at five representative positions, A to E, shown in FIG.

[0071] In this example, the first deviation amounts obtained 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. In this example, the deviation values are calculated by taking the variation on the upper side of the press (upper side of the paper) as positive and the variation on the lower side of the press (lower side of the paper) as negative relative to the standard press-molded product shape. In this embodiment, the second deviation amount obtained was as follows: For deformed blank 1, the values were 2.9 mm at site A, −2.6 mm at site B, 0.1 mm at site C, 0.1 mm at site D, and 1.3 mm at site E. For deformed blank 2, the deformations were −0.2 mm at site A, 0.1 mm at site B, 0.2 mm at site C, 1.0 mm at site D, and −1.3 mm at site E. For deformation blank 3, the deformations were −0.1 mm at site A, 0.5 mm at site B, −0.3 mm at site C, 0.8 mm at site D, and −2.3 mm at site E. Table 5 shows the results of the above deviations.

[0072] [Table 5]

[0073] As can be seen from Table 5, for parts A and B, the results of deformation blank 1 show that the main factor is the wave shape of the blank corresponding to A and B. That is, the wave part 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 portion D, is a major factor in portion D. In this example, it is a curved part. For this reason, 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. It is presumed that this affects the twist at position D. This also shows that the fluctuations in the target dimensional fluctuation area do not necessarily coincide with the wave position of the blank. It can be seen from Table 5 that the target dimensional variation location 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 deviation in the opposite direction of the variation at location E, which actually worsens the situation.

[0075] From these results, for example, if the dimensional fluctuations at the target dimensional fluctuation points A and B are a problem in terms of product production, it is estimated that the waves in the deformed blank 1 (area A) can be flattened relative to the reference shape fluctuation blank 3. To confirm this, an improved shape variation blank 6 was created by flattening the waves (area A) in the deformed blank 1 of the reference shape variation blank 3, as shown in Figure 13. Then, press forming analysis was performed using the set die model using this improved shape variation blank 6. The shape of the press-formed product after demolding was then obtained as the shape of the improved shape variation blank press-formed product. Then, for the portions A to E, the deviation between the reference press-formed product shape and the improved shape variation blank press-formed product shape was determined as a second deviation. The second deviation amounts obtained were -0.2 mm at site A, 0.2 mm at site B, 0.4 mm at site C, 1.5 mm at site D, and -3.6 mm at site E. The results are shown in Table 6.

[0076] [Table 6]

[0077] As can be seen from Table 6, site A and site B showed improvement as expected, while site E showed deterioration as expected. Furthermore, for example, if the dimensional fluctuations of the target dimensional fluctuation areas, parts D and E, especially the dimensional fluctuation of part E, are problematic in terms of product production, it can be seen from Table 5 that the waves in the deformed blank 3 part should be flattened.

[0078] The results of confirming whether this idea is correct are shown in Figure 14 and Table 7. This involves generating an improved shape variation blank 6 by flattening the waves in the deformed blank 3 portion of the reference shape variation blank 3, and then performing press forming analysis with the set die model using this improved shape variation blank 6. The shape of the press-formed product after demolding was then obtained as the shape of the improved shape variation blank press-formed product. Then, for the portions A to E, the deviation between the reference press-formed product shape and the improved shape variation blank press-formed product shape was determined as a second deviation. The second deviation amounts obtained were 2.9 mm at site A, −2.2 mm at site B, 0.2 mm at site C, 0.3 mm at site D, and 0.4 mm at site E. The results are shown in Table 7.

[0079] [Table 7]

[0080] As can be seen from Table 7, the dimensional variations of parts D and E showed the expected improvement results. 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, since areas A and C are flattened, it is thought that this will have a positive effect on suppressing the variation of the part.

[0081] "Fourth Example" Next, a fourth embodiment will be described. The fourth embodiment is similar to the third embodiment, except that draw forming is used as the press working. In the reference shape variation blank model generating step S3 of this embodiment, an actual wave shape was imparted to generate the reference shape variation blank model based on the second generation method described above. Specifically, in this embodiment, 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 FIG. 15(b), was imparted 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 determined as a first deviation amount, and the deviation amount was determined at five representative positions, A to E, shown in FIG. The other processing steps are omitted since they are the same as those in the third embodiment. The deviation amounts obtained are shown in Table 8.

[0082] [Table 8]

[0083] As can be seen from Table 8, for parts B to E, the results of Deformed Blank 1, Deformed Blank 2, and Deformed Blank 3 show that the main cause is the wave of the blank corresponding to parts B to E, respectively. In other words, the wave and the fluctuation position are the same results.

[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 fluctuations in the target dimensional fluctuation locations do not necessarily coincide with the wave position of the blank.

[0085] From the results of Table 8, it can be seen that, for example, if the dimensional fluctuations at the target dimensional fluctuation locations D and E are a problem in terms of product production, the waves at the deformed blank 3 portion should be flattened. I checked to see if that was correct. 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. Then, press forming analysis was performed with the set die model using the improved shape variation blank 6 as shown in Figure 16. After that, the shape of the press-formed product after demolding was obtained as the shape of the improved shape variation blank press-formed product. Then, for the portions A to E, the deviation between the standard press-formed product shape and the press-formed product shape obtained using the improved shape variation blank 6 was determined as a second deviation. The second deviation amounts obtained were 1.6 mm at site A, −1.6 mm at site B, 0.8 mm at site C, 0.8 mm at site D, and −0.5 mm at site E. The results are shown in Table 9.

[0086] [Table 9]

[0087] As can be seen from Table 9, the dimensional fluctuations at sites D and E improved as expected, but at site C they 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 wave portion (area C) of the deformed blank 3, that is, the shape on 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.

[0088] (others) The present disclosure may also have the following configuration. (1) Disclosure 1 is an analysis method for identifying which part of a blank is responsible for a dimensional variation factor relative to a target part shape when a blank having a shape variation is formed by press-molding a blank having a shape variation taken from a metal plate having a shape variation using a press die, a reference press-molded product shape acquisition step of performing press-molding analysis using a flat blank model having a flat shape and a die model set based on a target part shape, and acquiring the press-molded product shape after demolding as a reference press-molded product shape; a reference shape variation blank model generation step of generating a reference shape variation blank model which is a model of the blank having the shape variation; A reference shape variation press-molded product shape acquisition step in which press molding analysis is performed using the reference shape variation blank model and the press-molded product shape after mold release is acquired as the reference shape variation blank press-molded product shape; a first deviation amount acquisition step of comparing the reference press-formed product shape with the reference-shape-varied blank press-formed product shape to determine 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 part of the blank having the shape variation is changed to be flat, by changing the part to be changed to be flat; A deformed shape variation press-molded product shape acquisition step in which a press molding analysis is performed using the deformed shape variation blank model to perform press molding with the set die model, and a process of acquiring the press-molded product shape after demolding as a deformed shape variation blank press-molded product shape is performed for each model of the deformed shape variation blank model; 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 a deviation portion where the two shapes deviate and a second deviation amount, which is the deviation amount, for each of the multiple 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 variation blank press-formed product shape by comparing the first deviation amount and the second deviation amount at the same portion of the press-formed product shape; A method for analyzing the causes of dimensional variation. (2) In Disclosure 2, the determination step determines 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 as the shape variation area that is the main cause for the same part. (3) Disclosure 3 states that 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 as the deformed shape variation blank model by changing the portions other than the target region of the reference shape variation blank model to be flat. (4) Disclosure 4 states that the above determination step is identifying, 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 preset deviation threshold value, as a dimensional variation portion; For each identified dimensional variation location, the second deviation amount and the first deviation amount for each of the deformed shape variation blank models for the same portion as the dimensional variation location are compared, and the area having a wavy shape in the deformed shape variation blank model that has a second deviation amount that is relatively close to the first deviation amount is determined to be the shape variation location that is the main cause of the dimensional variation location in question. (5) Disclosure 5 states that the reference shape variation blank model generation step determines the 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) Disclosure 6 states that the reference shape variation blank model generation step measures the shape of an actual blank taken from a metal plate having shape variation, and based on the measurement results, generates a blank model having a wave shape that conforms to the shape of the actual blank as the reference shape variation blank model. (7) Disclosure 7 discloses that the first deviation amount acquisition step The difference between the springback amount of a predetermined portion in the reference press-formed product shape and the springback amount of the same portion as the predetermined portion in the reference press-formed product shape in the reference shape variation blank press-formed product shape is acquired as the first deviation amount, The second deviation amount acquisition step includes: The difference between the springback amount of a specified portion in the reference press-formed product shape and the springback amount of the same portion as the specified portion in the reference press-formed product shape in the deformed shape variation blank press-formed product shape is obtained as the second deviation amount. (8) Disclosure 8 is an analysis device that identifies which part of a blank is the cause of a dimensional variation in a target part shape of a press-formed product formed by press-forming a blank having a shape variation taken from a metal plate having a shape variation using a press die, and the cause of the dimensional variation is the shape variation of the blank, a reference press-formed product shape acquisition unit that performs press-forming analysis using a flat blank model having a flat shape and a die model set based on a target part shape, and acquires the shape of the press-formed product 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 having the shape variation; A reference shape variation press-molded product shape acquisition unit that performs press molding analysis using the reference shape variation blank model and the set die model to acquire the press-molded product shape after mold release as the reference shape variation blank press-molded product shape; a first deviation amount acquisition unit that compares the reference press-formed product shape with the reference-shape-varied blank press-formed product shape and determines 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 unit that generates a plurality of deformed shape variation blank models, which are models in which a part of the blank having the shape variation is changed to be flat, by changing the part to be changed to be flat; A deformed shape variation press-molded product shape acquisition unit that performs a process of performing press molding analysis using the deformed shape variation blank model to press-molde with the set die model and acquiring the press-molded product shape after demolding as a deformed shape variation blank press-molded product shape for each model of the deformed shape variation blank model; a second deviation amount acquisition unit that compares the reference press-formed product shape with the deformed-shape-varying blank press-formed product shape, and obtains a deviation portion where the two shapes deviate and a second deviation amount, which is the deviation amount, for each of the plurality of deformed-shape-varying blank models; 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-varied 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; A dimension variation factor analysis device equipped with the device. (9) Disclosure 9 states that the determination unit determines an area in the same part that has a wavy shape in the deformed shape variation blank model having 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. (10) Disclosure 10 discloses that the deformed shape variation blank model generation unit divides the blank having a shape variation into a plurality of regions, and for each region, generates a blank model as the deformed shape variation blank model by changing the portion of the reference shape variation blank model other than the target region to be flat. (11) Disclosure 11 is that the determination unit a dimension variation location identifying unit that identifies, from the deviation location obtained in the first deviation amount acquisition step and the first deviation amount, a deviation location where the absolute value of the first deviation amount is equal to or greater than a preset deviation threshold, as a dimension variation location; a factor location determination unit that compares the second deviation amount and the first deviation amount for each of the deformed shape variation blank models for the same portion as the dimensional variation location for each of the identified dimensional variation locations, and determines a region having a wave shape in the deformed shape variation blank model that has the second deviation amount relatively close to the first deviation amount as the shape variation location that is the main cause of the dimensional variation location of the target; Equipped with. (12) Disclosure 12 discloses that the reference shape variation blank model generation unit determines the pitch and amplitude from measurements obtained by measuring the shape of an actual blank taken from a metal plate having 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) 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 is the first deviation amount acquisition unit, The difference between the springback amount of a predetermined portion in the reference press-formed product shape and the springback amount of the same portion as the predetermined portion in the reference press-formed product shape in the reference shape variation blank press-formed product shape is acquired as the first deviation amount, The second deviation amount acquisition unit The difference between the springback amount of a specified portion in the reference press-formed product shape and the springback amount of the same portion as the specified portion in the reference press-formed product shape in the deformed shape variation blank press-formed product shape is obtained as the second deviation amount. (15) Disclosure 15 causes a computer to function as the dimensional variation factor analysis device of the present disclosure, Dimensional variation factor analysis program. (16) Disclosure 16 is a method for manufacturing a press-molded product, in which a blank taken from a metal plate having a shape variation is press-molded using a press die to manufacture a press-molded product having a target part shape, The present disclosure provides a method for analyzing factors behind dimensional variation, Before press forming, shape correction is performed on the portion of the blank that has been determined to be the main cause of the deviation in the determination step. Manufacturing method for press-molded products.

[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 application has described a limited number of embodiments, the scope of the invention is not limited thereto, and modifications of each embodiment based on the above disclosure would be obvious to one skilled in the art. [Explanation of symbols]

[0090] 11. Dimensional variation factor analysis device 12 Display device 13 Input Devices 14 Storage device 15 Working data memory 20 Processing unit 21 Standard press-molded product shape acquisition unit 22 Reference shape variation blank model generation unit 23 Reference shape variation press-molded product shape acquisition unit 24 First deviation amount acquisition part 25 Deformation shape variation blank model generation unit 26 Deformation shape fluctuation press-molded product shape acquisition unit 27 Second deviation amount acquisition part 28 Judgment section 28A Dimensional variation location identification section 28B Factor location determination unit S1 Step for obtaining the standard press-molded product shape S3: Reference shape variation blank model generation step S5 Step for obtaining the shape of press-molded products by changing the reference shape S7 First deviation amount acquisition step S9 Deformation shape variation blank model generation step S11 Deformation shape variation press-molded product shape acquisition step S13 Second deviation acquisition step S15 Judgment step S15A Dimensional variation location identification step S15B Factor location determination step

Claims

1. An analysis 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 variation, the blank being taken from a metal plate having shape variation, using a press die, the method comprising: a reference press-molded product shape acquisition step of performing press-molding analysis using a flat blank model having a flat shape and a die model set based on a target part shape, and acquiring the press-molded product shape after demolding as a reference press-molded product shape; a reference shape variation blank model generation step of generating a reference shape variation blank model which is a model of the blank having the shape variation; A reference shape variation press-molded product shape acquisition step in which press molding analysis is performed using the reference shape variation blank model and the press-molded product shape after mold release is acquired as the reference shape variation blank press-molded product shape; a first deviation amount acquisition step of comparing the reference press-formed product shape with the reference-shape-varied blank press-formed product shape to determine 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 part of the blank having the shape variation is changed to be flat, by changing the part to be changed to be flat; A deformed shape variation press-molded product shape acquisition step in which a press molding analysis is performed using the deformed shape variation blank model to perform press molding with the set die model, and a process of acquiring the press-molded product shape after demolding as a deformed shape variation blank press-molded product shape is performed for each model of the deformed shape variation blank model; 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 a deviation portion where the two shapes deviate and a second deviation amount, which is the deviation amount, for each model 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-varied blank press-formed product shape by comparing the first deviation amount and the second deviation amount at the same portion of the press-formed product shape; A method for analyzing the causes of dimensional variation.

2. The determining step determines a region in the same portion 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 shape variation portion that is a main cause of the shape variation for the same portion. The method for analyzing factors of dimensional variation according to claim 1 .

3. The deformed shape variation blank model generation step divides the blank having a shape variation into a plurality of regions, and for each region, generates 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. The method for analyzing factors of dimensional variation according to claim 1 .

4. The above determination step is identifying, 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 preset deviation threshold value as a dimensional variation portion; For each identified dimensional variation location, the second deviation amount and the first deviation amount for each of the deformed shape variation blank models for the same portion as the dimensional variation location are compared, and a region having a wavy shape in the deformed shape variation blank model having the second deviation amount relatively close to the first deviation amount is determined to be the shape variation portion that is the main cause of the target dimensional variation location. The method for analyzing factors of dimensional variation according to claim 3.

5. The reference shape variation blank model generation step calculates a pitch and an amplitude based on measurements obtained by measuring the shape of an actual blank sampled from a metal plate having a shape variation, and generates a blank model having a wave shape that periodically changes with the calculated pitch and amplitude as the reference shape variation blank model. The method for analyzing factors of dimensional variation according to claim 1 .

6. The reference shape variation blank model generation step measures the shape of an actual blank sampled from a metal plate having a shape variation, and generates a blank model having a wave shape conforming to the shape of the actual blank based on the measurement result as the reference shape variation blank model. The method for analyzing factors of dimensional variation according to claim 1 .

7. The first deviation amount acquisition step includes: The difference between the springback amount of a predetermined portion in the reference press-formed product shape and the springback amount of the same portion as the predetermined portion in the reference press-formed product shape in the reference shape variation blank press-formed product shape is acquired as the first deviation amount, The second deviation amount acquisition step includes: The difference between the springback amount of a predetermined portion in the reference press-formed product shape and the springback amount of the same portion as the predetermined portion in the reference press-formed product shape in the deformed shape variation blank press-formed product shape is acquired as the second deviation amount. The method for analyzing factors of dimensional variation according to claim 1 .

8. An analysis device 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 variation, the blank being taken from a metal plate having 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 having a flat shape and a die model set based on a target part shape, and acquires the shape of the press-formed product 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 having the shape variation; A reference shape variation press-molded product shape acquisition unit that performs press molding analysis using the reference shape variation blank model and the set die model to acquire the press-molded product shape after mold release as the reference shape variation blank press-molded product shape; a first deviation amount acquisition unit that compares the reference press-formed product shape with the reference-shape-varied blank press-formed product shape, and determines 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 unit that generates a plurality of deformed shape variation blank models, which are models in which a part of the blank having the shape variation is changed to be flat, by changing the part to be changed to be flat; A deformed shape variation press-molded product shape acquisition unit that performs a process of performing press molding analysis using the deformed shape variation blank model to press-molde with the set die model and acquiring the press-molded product shape after demolding as a deformed shape variation blank press-molded product shape for each model of the deformed shape variation blank model; 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 a deviation portion where the two shapes deviate and a second deviation amount, which is the deviation amount, for each of the multiple deformed-shape-variation blank models; 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-varied blank press-formed product shape by comparing the first deviation amount and the second deviation amount at the same portion of the press-formed product shape; A dimension variation factor analysis device equipped with the device.

9. The determination unit determines a region in the same portion 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 shape variation portion that is a main cause of the shape variation for the same portion. The dimensional variation factor analysis device according to claim 8.

10. The deformed shape variation blank model generation unit divides the blank having a shape variation into a plurality of regions, and for each region, generates 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. The dimensional variation factor analysis device according to claim 8.

11. The determination unit a dimension variation location identifying unit that identifies, from the deviation location obtained in the first deviation amount acquisition step and the first deviation amount, a deviation location where the absolute value of the first deviation amount is equal to or greater than a preset deviation threshold, as a dimension variation location; a factor location determination unit that compares the second deviation amount and the first deviation amount for each of the deformed shape variation blank models for the same portion as the dimensional variation location for each of the identified dimensional variation locations, and determines an area having a wave shape in the deformed shape variation blank model that has the second deviation amount relatively close to the first deviation amount as the shape variation location that is the main cause of the dimensional variation location of interest; The dimensional variation factor analysis device according to claim 10, comprising:

12. The reference shape variation blank model generation unit obtains a pitch and an amplitude from measurements obtained by measuring the shape of an actual blank sampled from a metal plate having a 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. The dimensional variation factor analysis device according to claim 8.

13. The reference shape variation blank model generation unit acquires a measurement result of measuring the shape of an actual blank taken from a metal plate having a shape variation, and generates a blank model having a wave shape that conforms to the shape of the actual blank based on the measurement result as the reference shape variation blank model. The dimensional variation factor analysis device according to claim 8.

14. The first deviation amount acquisition unit The difference between the springback amount of a predetermined portion in the reference press-formed product shape and the springback amount of the same portion as the predetermined portion in the reference press-formed product shape in the reference shape variation blank press-formed product shape is acquired as the first deviation amount, The second deviation amount acquisition unit The difference between the springback amount of a predetermined portion in the reference press-formed product shape and the springback amount of the same portion as the predetermined portion in the reference press-formed product shape in the deformed shape variation blank press-formed product shape is acquired as the second deviation amount. The dimensional variation factor analysis device according to claim 8.

15. A computer is caused to function as the dimension variation factor analysis device according to any one of claims 8 to 14. Dimensional variation factor analysis program.

16. A method for manufacturing a press-formed product by press-forming a blank taken from a metal plate having a shape variation using a press die to manufacture a press-formed product having a target part shape, The method for analyzing the causes of dimensional fluctuations according to any one of claims 1 to 7 is provided, Before press forming, shape correction is performed on the portion of the blank that has been determined to be the main cause of the deviation in the determination step. Manufacturing method for press-molded products.

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