JP2007313533A - Method for making shape correction data of press die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for making shape correction data of a press die, which method can obtain an optimum estimated shape of the press die by automatic calculation. <P>SOLUTION: When the process for forming a plate model by a die model is analyzed on a computer using the elasto-plasticity finite element method, the die model is made (step S100 to step S102), and forming simulation is carried out using the die model (step S103), and the spring-back shape of the plate model is calculated (step S104), and the deforming stress for causing the deformation corresponding to the difference between the spring-back shape and the shape of a product model is calculated (step S108), and corrected product shape data are calculated using the deforming stress, and the die model is corrected based on the corrected product shape data (step S113). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for creating press mold correction shape data for correcting spring back.

  When a plate material is press-molded using a molding die, a molded part taken out from the molding die after press molding is elastically deformed (springback) by releasing residual stress generated during press molding. For this reason, the molded part has a shape different from that of the molding die, and it is impossible to mold a molded part having the correct shape with a molding die created in the same shape as the part drawing. For this reason, in order to mold a molded part having the same shape as the design drawing, it is necessary to weave the shape in consideration of the spring back amount into the molding die.

  As a method of creating a molding die into a shape incorporating the springback amount, for example, based on the measurement data of the springback amount of similar parts in the past or the quantitative data of springback obtained by experiments etc. The method of creating the prospective shape is taken.

  In the above-described conventional method (a method for creating a molding die into a shape incorporating a springback amount), a probable die shape is created from the shape of the springback simulation, and a springback is performed using a die model of this shape. When the simulation is performed, the product model shape is not always correct.

  For this reason, when the shape after the spring back of the plate model does not match the product shape as compared with the regular product shape, it is necessary to correct the data of the mold model. In this correction, a difference in deviation between the shape of the plate model after the spring back and the shape of the product model is obtained, and the correction amount of the mold model is obtained based on this value.

  However, in the case of a pressed part (molded part) with a combination of warpage, twisting, opening, etc., if a spring back simulation is performed using a mold model with an expected mold shape based on experience values, the shape of the product model The error may be large. In this case, it is necessary to create a mold expected shape from the shape difference between the shape of the plate model after springback and the shape of the product model, but it is necessary to correct complex deformation such as twisting, warping, and opening. It is difficult to obtain the amount, and if this operation is performed manually, a difference in judgment or mistakes by humans occurs, and it is difficult to obtain a correct correction amount.

  The present invention solves the above-described problems, and an object of the present invention is to provide a method for creating press die correction shape data that can obtain an optimum die expected shape by automatic calculation.

  In order to achieve the above-mentioned object, the press die correction shape data creation method according to the present invention is a process of analyzing on a computer using an elastoplastic finite element method in the process of forming a plate material model by a die model. Then, create a mold model, perform molding simulation using the mold model, find the spring back shape of the plate model, and the deformation stress that causes the deformation amount of the shape difference between this spring back shape and the product model shape Is obtained by molding simulation, and the mold model is corrected using this deformation stress.

  Therefore, it is possible to eliminate the work of creating the mold expected shape from the shape difference, which is a conventional technique, and the work by human judgment, and it is possible to eliminate the difference in human judgment and mistakes. In addition, because the expected value of the mold is determined based on the deformation stress that causes the difference from the product model shape due to the springback, even in the case of a pressed part with a combination of warpage, twisting, opening, etc. The optimal mold expected shape (the optimal correction amount of the mold model) can be obtained.

  In addition, the method for creating the press die correction shape data according to the present invention is the above-described method for creating the press die correction shape data according to the present invention, and the method for correcting the die model is created based on the part shape. Surface data creation process to create surface data of the mold model, mesh data conversion process to convert the surface data of the mold model in this surface data creation process to mesh data, and mesh data conversion in this mesh data conversion process A molding simulation process for performing a molding simulation using a flat plate model using the mold model thus formed, a springback simulation process for performing a springback simulation based on the result of the molding simulation in the molding simulation process, and the spring Bag A check process that checks whether the result of the springback simulation in the simulation process matches the product model shape, and a plate material used for the springback simulation when it is determined that the check process does not match For the mesh data of the model, the mesh data of the plate material model from which the stress was removed in the first stress relief process using the first stress relief process that removes the stress in the springback state and the mold model of the product model shape. Molding simulation process after stress removal that performs molding simulation to the bottom dead center, and a stress value output process that outputs a stress value on each mesh of the plate model in the bottom dead center state of the molding simulation result in the molding simulation process, Molding process in the molding simulation process A second stress removal process for removing the stress in the sheet model in the state of bottom dead center and outputting the stress, and each mesh on the sheet model from which the stress has been removed in the second stress removal process, A mapping process that maps the stress value of the corresponding mesh in the plate model output in the value output process, and a spring forward that performs a Spong Forward simulation by reversing the stress value on each mesh of the plate model obtained in this mapping process ± A correction mold model shape creation process for obtaining corrected part shape data based on the simulation process, a plate material model spring-forwarded in the spring forward simulation process, and creating a corrected mold model shape based on the corrected part shape data, and a check process When it is judged that the Le, have an external output step of outputting the surface data corrected to outside, it is obtained so as to form a closed loop back to surface data generating step from the modified die Creating Model Structure step.

  Therefore, there is no need for human judgment, and a closed loop of shape change and simulation can be configured, and an optimum mold expected shape can be obtained by automatic calculation.

  According to the method for creating press die correction shape data according to the present invention, it is possible to eliminate the work of creating the expected shape of the die from the shape difference which is a conventional technique and the work by human judgment, and human judgment. Difference and errors can be eliminated, and even in the case of press parts that are combined with warpage, twisting, opening, etc., there is no need for human judgment and the optimal mold shape (easily the optimal mold) can be easily obtained. Model correction amount).

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of a support system used for carrying out the method for creating press die correction shape data according to the present invention, FIG. 2 is a block diagram depicting the configuration of the CPU of FIG. 1, and FIG. The flowchart which shows the operation | movement in the preparation method of the press die correction shape data based on invention, FIG. 4 is explanatory drawing of the operation | movement order in the preparation method of the press die correction shape data.

  The press die correction shape data creation method according to the present invention creates correction shape data of a molding die for molding a molded part accompanied by plastic deformation such as a press part of any equipment. Using the mold data having the molded part of this shape, the model data of the flat plate is molded and simulated, and the resulting shape data of the molded part (shape data in the springback state) and the regular part data This is a method for obtaining a corrected shape from the difference.

  At this time, the material used for the molded part is particularly effective when the material has a large amount of spring back, such as a high-strength steel plate or aluminum plate. However, the material of the molded part is not limited to the above.

  Here, the springback characteristic means that the metal material that has been subjected to the forming process returns to its original shape. For example, when a plate-shaped blank is pressed, a part bent at a predetermined angle returns the processed product to an angle shallower than the angle when the mold is released. In particular, a high strength steel material, an aluminum plate, and the like have a large amount of springback (amount of deformation due to springback characteristics).

  As shown in FIG. 1, a support system used to implement a method for creating press die correction shape data according to the present invention includes a CPU (arithmetic unit) 11 having a predetermined arithmetic processing capability, and a predetermined storage capacity. A computer 1 having a hard disk 12 is used.

  The computer 1 is a computer such as a workstation, a server computer, or a personal computer.

  The computer 1 includes a CPU 11, a hard disk 12, a RAM 13 that temporarily stores predetermined data to be processed, a keyboard (input device) 14 for an operator to input predetermined data, It has equipment equipped with a general computer, such as a display (output device) 15 for displaying processing results and the like to an operator.

  Accordingly, although not shown, a ROM for storing a program frequently used in the computer 1, a drive for reading predetermined data from another storage medium (for example, CD-ROM) (for example, a CD-ROM drive), etc. It also has.

  The computer 1 may be connected to a three-dimensional shape measuring machine or another computer that creates an FEM model as will be described later.

  As shown in FIG. 2, the CPU 11 of the computer 1 includes a mold model creation means 11a, a surface data creation means 11b, a mesh data conversion means 11c, a molding simulation means 11d, a springback simulation means 11e, Check means 11f, first stress relief means 11g, molding simulation means 11h after stress relief, stress value output means 11i, second stress relief means 11j, mapping means 11k, spring forward simulation means ( (Elastic recovery amount calculating means) 11l, modified mold model shape creating means 11m, and external output processing means 11n.

  Then, a surface data creation process by the surface data creation means 11b, a mesh data conversion process by the mesh data conversion means 11c, a molding simulation process by the molding simulation means 11d, a springback simulation process by the springback simulation means 11e, and a check means 11f, a stress removing step by the first stress removing means 11g, a forming simulation step by the forming simulation means 11h after the stress removal, a stress value outputting step by the stress value outputting means 11i, and a second stress removing Stress removal step by means 11j, mapping step by mapping means 11k, and spring forward simulation by spring forward simulation means 11l A step, and the modified die Creating Model Structure step by modifying mold model shape creating means 11m, it is possible to form a closed loop by returning from the modified die Creating Model Structure step surface data creation step.

  The mold model creating means 11a has a function of creating a mold model based on the part shape.

  The surface data creation unit 11b has a function of creating surface data of the mold model created by the mold model creation unit 11a.

  The mesh data conversion unit 11c has a function of converting the surface data of the mold model into mesh data.

  The forming simulation means 11d has a function of performing a forming simulation using a flat plate material model by an elastic-plastic finite element method using the mesh data of the mold model described above.

  The springback simulation unit 11e has a function of performing a springback simulation based on the result of the molding simulation by the molding simulation unit 11d.

  The check means 11f has a function of checking whether or not the result of the springback simulation by the springback simulation means 11e matches the product model shape.

  The first stress removing unit 11g has a function of removing stress in a spring-back state with respect to mesh data of the plate material model used for the spring-back simulation when it is determined that the check unit 11f does not match.

  The forming simulation 11h after the stress removal has a function of performing a forming simulation of the mesh data of the plate material model from which the stress is removed by the first stress removing means 11g to the bottom dead center, using a die model having a product model shape.

  The stress value output means 11i has a function of outputting a stress value on each mesh of the bottom dead center plate model as a result of the forming simulation in the forming simulation means 11h.

  The second stress removing means 11j has a function of removing and outputting the stress in the plate material model in the state of bottom dead center from the plate material model formed by the forming simulation 11d.

  The mapping unit 11k has a function of mapping the stress value of the corresponding mesh in the plate model output by the stress value output unit 11i to each mesh on the plate model from which the stress is removed by the second stress removing unit 11j.

  The spring forward simulation unit 11l has a function of performing a spring forward simulation by inverting the stress value on each mesh of the plate material model obtained by the mapping unit 11k by ± (that is, multiplying the stress value by k = −1.0).

  The corrected mold model shape creation means 11m has a function of obtaining corrected part shape data based on the plate material model spring-forwarded by the spring forward simulation means 11l and creating a corrected mold model shape based on the corrected part shape data.

  The external output processing unit 11n has a function of outputting the corrected surface data of the mold model to the outside.

  Next, the operation of the method of the present invention will be described based on the flowchart shown in FIG. 3 and the explanatory diagram of the operation sequence shown in FIG.

  The method of the present invention creates a mold model based on a part shape in the process of analyzing on a computer using an elastoplastic finite element method in the process of forming a sheet material model by a mold model (surface of this mold model). Creating data and converting the surface data into mesh data), creating surface data of the mold model and converting the surface data into mesh data (steps from step S100 to step S102), Mold simulation is performed using the mold model to obtain the spring back shape of the plate material model, the deformation stress that causes the deformation amount of the shape difference between this spring back shape and the product model shape is obtained by molding simulation, and this deformation stress is calculated. Use this to find the corrected part shape data. Fixed mold model shape based can be roughly distinguished as the step of creating a (steps leading from step S103 to step S113).

  That is, when the process is started, the CPU 11 of the computer 1 first creates a mold model based on the part shape (a mold model creating step by the mold model creating means 11a) (step S100).

  Next, surface data of the mold model is created (surface data creation step by the surface data creation means 11b) (step S101).

  Next, the surface data of the mold model is converted into mesh data (mesh data conversion step by the mesh data conversion means 11c) (step S102).

  Next, a molding simulation is performed using a flat plate model using the mold model in step S102 (a molding simulation step by the molding simulation means 11d) (step S103).

  Next, a springback amount is calculated based on the stress distribution acting in the plate thickness direction of the plate material model through this forming simulation, that is, a springback simulation is performed (a springback simulation step by the springback simulation means 11e) (step S104).

  Next, it is checked whether or not the shape of the plate material model after the spring back in the spring back simulation in step S104 is consistent with the final product model shape (checking step by the checking means 11f) (step S105).

  If it is determined in step S105 that the shape after the spring back of the plate model matches the product shape (within the allowable range), the surface data of the mold model created in step S101 is used for NC processing, for example. Is output to the controller of the NC processing machine (external output process by the external output processing means 11o) (step S106), and this routine is terminated.

  When it is determined in step S105 that the shape of the plate model after the spring back does not match the product shape (out of the allowable range) (when the comparison result in step S105 is NG), the following method is used. Modify the mold model.

  With respect to the mesh data of the plate material model used in the springback simulation in step S104, the stress is removed in the springback state (stress removal step by the first stress removal means 11g) (step S107).

  Next, using the mold model of the product model shape, the forming simulation of the mesh data of the plate material model in which the stress is removed in step S107 is performed to the bottom dead center (the forming simulation process by the forming simulation means 11h after the stress is removed) (step S108). As a result, deformation of the shape difference between the springback shape and the product shape is given to the mesh data of the plate material model, and the same amount of deformation stress as the starting force of the springback is given to the plate material model.

  Next, the stress value on each mesh of the bottom dead center plate model as a result of the forming simulation in step S108 is output (stress value output step by the stress value output means 11i) (step S109).

  On the other hand, the stress in the plate material model is removed in the state of the bottom dead center of the plate material model formed and simulated in step S103 (stress removal step by the second stress removal means 11j) (step S110).

  Next, the stress of the corresponding mesh in the plate model created in step S109 is mapped to each mesh on the plate model output in step S110 (mapping step by the mapping unit 11k) (step S111).

  Since the plate material model used in step S109 and step S110 are both mesh data of the plate material model formed and simulated in step S103, each contact point and mesh element all correspond one-to-one. Can be mapped on a one-to-one basis.

  Next, the stress value on each mesh of the plate material model obtained in step S111 is inverted ± (ie, the stress value is multiplied by k = −1.0), and a spring forward simulation is performed (spring by the spring forward simulation means 11l). Forward simulation step) (step S112).

  In this spring forward simulation, the residual stress distribution acting in the plate thickness direction of the plate model calculated by the spring back simulation is reversed ±, and the spring forward when the inverted residual stress distribution is acting on the plate model ( This is a process for calculating the amount of elastic recovery.

  That is, this spring forward simulation reverses the residual stress distribution acting on the plate material of the plate material model 21 calculated by the spring back simulation (see FIG. 6). That is, the residual stress value in the plate material model 21 is inverted ± (that is, the stress value is multiplied by k = −1.0). This is a process of calculating the amount of spring forward (elastic recovery) when the inverted stress distribution acts on the plate material model 21. FIG. 7 is a diagram illustrating the shape 20-1 after the spring back of the molded part 20 and the shape 20-2 after the spring forward.

  Since the spring back is generated by repulsion of the residual stress acting in the plate thickness direction of the plate material, when the residual stress in the plate thickness direction acting on the plate material model 21 is reversed, a shape that is spring-forwarded (elastically recovered) inward is obtained. It will be.

  Next, corrected part shape data is obtained based on the plate material model spring-forwarded in step S112, and a corrected mold model shape is created based on the corrected part shape data (corrected mold model shape by the corrected mold model shape creating means 11m). Creation step) (step S113).

  Next, the above result is returned to step S101. By repeating this closed loop, the shape of the springback amount of the plate material model can be made as close as possible to the product model shape, and the optimum shape of the mold surface data can be output.

  If it is determined in step S105 that the shape after the spring back of the plate model matches the product shape (within the allowable range), the modified surface data of the mold model is used for NC processing, for example. The data is output as data to the controller of the NC processing machine (external output process by the external output processing means 11o) (step S106), and this routine is terminated.

  According to the embodiment of the present invention, in the process of forming a plate material model by a mold model, a mold model based on the part shape is created in the process of analyzing on a computer using the elastoplastic finite element method, Surface data of the mold model is created, the surface data is converted into mesh data (steps S100 to S102), and a molding simulation is performed using the mold model (step S103), and the spring back shape of the plate material model is obtained. (Step S104), a deformation stress that causes a deformation amount of the shape difference between the springback shape and the product model shape is obtained by molding simulation (Step S108), and corrected part shape data is obtained using the deformation stress, and this correction is performed. Modified the mold model based on the part shape data. S113) by conventional work and of creating a mold estimated shape from the shape difference is a technique, it is possible to eliminate the work by judgment of the person, the difference or the human judgment can be eliminated mistakes. In addition, because the expected value of the mold is determined based on the deformation stress that causes the difference from the product model shape due to the springback, even in the case of a pressed part with a combination of warpage, twisting, opening, etc. The optimal mold expected shape (the optimal correction amount of the mold model) can be obtained.

  In addition, the method for correcting the mold model is configured as a closed loop that returns from the above-described corrected mold model shape creation process to the surface data creation process. A closed loop can be formed, and an optimum mold expected shape can be obtained by automatic calculation.

  In the above description of the embodiment of the present invention, it has been described that the residual stress value in the plate model is reversed ± (ie, the stress value is multiplied by k = −1.0) for the sake of convenience during the spring forward. In the present invention. Since the calculation is repeatedly performed using the spring forward method, the value multiplied by the residual stress value in the plate model need not be limited to -1.0 at the time of the spring forward calculation. By using a coefficient in the range of 0> k ≧ −1.0, the convergence value can be obtained by repeated calculation.

  The present invention can eliminate the work of creating the mold expected shape from the shape difference that is a conventional technique, the work by human judgment, can eliminate the difference of human judgment and mistakes, Even in the case of pressed parts with a combination of warping, twisting, opening, etc., there is no need for human judgment, and it is possible to easily find the optimal mold expected shape (optimal mold model correction amount). Therefore, it is useful as a method of creating press mold correction shape data for correcting spring back.

It is a block diagram which shows the structure of the assistance system used for enforcing the production method of the press die correction shape data which concerns on this invention. It is a block diagram which shows the structure of CPU of FIG. It is a flowchart which shows operation | movement in the production method of the press die correction shape data which concerns on this invention. It is explanatory drawing of the operation | movement order in the production method of the press die correction shape data. It is a perspective view of a molded part. It is explanatory drawing explaining the process in which the stress distribution which acts on the plate | board thickness direction of a board | plate material model is reversed. It is a figure which illustrates the shape after the springback of a molded part, and the shape after a spring forward.

Explanation of symbols

1 Computer 11 CPU (Calculation unit)
11a Mold model creation means,
11b Surface data creation means 11c Mesh data conversion means 11d Molding simulation means 11e Springback simulation means 11f Check means 11g First stress removal means 11h Molding simulation means after stress removal 11i Stress value output means 11j Second stress removal means 11k Mapping means 11l Spring forward simulation means 11m Mold shape data correction means for re-correction 11n External output processing means 12 Hard disk 13 RAM
14 Keyboard (input device)
15 Display (output device)

Claims (2)

  In the process of forming a plate material model with a mold model, the mold model is created in the process of analyzing on a computer using an elastoplastic finite element method, and a molding simulation is performed using the mold model. The spring back shape of the model was obtained, the deformation stress that caused the deformation amount of the shape difference between the spring back shape and the product model shape was obtained by molding simulation, and the mold model was corrected using this deformation stress. A method for creating press die correction shape data. The method of modifying the mold model is as follows:
Surface data creation process to create the surface data of the mold model created based on the part shape,
A mesh data conversion step of converting the surface data of the mold model in the surface data creation step into mesh data;
A molding simulation process for performing a molding simulation using a flat plate material model using the mold model converted into the mesh data in the mesh data conversion process,
A molding simulation process for performing a molding simulation using a flat plate model using the mold model,
A springback simulation process for performing a springback simulation based on the result of the molding simulation in this molding simulation process;
A check process for checking whether or not the result of the springback simulation in this springback simulation process and the product model shape match,
A first stress removing step of removing stress in a spring-backed state for mesh data of the plate material model used in the spring-back simulation when it is determined that they are not matched in the checking step;
Using the mold model of the product model shape, a molding simulation process after stress removal that performs a molding simulation of the mesh data of the plate material model subjected to stress removal in the first stress relief process to the bottom dead center;
A stress value output step for outputting a stress value on each mesh of the plate model in the bottom dead center state of the molding simulation result in the molding simulation step;
A second stress removal step of removing and outputting the stress in the plate material model in a state of bottom dead center in the plate material model formed and simulated in the forming simulation step;
A mapping step of mapping the stress value of the corresponding mesh in the plate model output in the stress value output step to each mesh on the plate model from which the stress has been removed in the second stress removal step;
A spring forward simulation step of performing a spanning forward simulation by reversing the stress value on each mesh of the plate model obtained in this mapping step;
A corrected mold model shape creating step for obtaining corrected part shape data based on the plate material model spring-forwarded in the spring forward simulation process, and creating a corrected mold model shape based on the corrected part shape data;
An external output step of outputting the modified surface data of the mold model to the outside when it is determined that the check step is consistent;
2. The method for creating press die correction shape data according to claim 1, wherein a closed loop returning from the correction die model shape creation step to the surface data creation step is configured.

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