JP2010228247A - Simulation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simulation system capable of grasping the occurrence of deformation with high precision. <P>SOLUTION: The simulation system comprises: conducting a flow analysis (S4 to S8) of a molten resin injected into a predetermined article shape under a predetermined molding condition; calculating an actually existing mass Mi of each element Ei of the filled molten resin based on the result of the flow analysis (S7); calculating a necessary mass NMi of the molten resin of each element Ei (S10); calculating an ideal mass IMi of the molten resin of each element Ei (S11); and determining a molding defect of each element Ei based on a deformation index DIi calculated by dividing deviation between the actually existing mass Mi and the necessary mass NMi of the elements Ei by the ideal mass IMi (S13). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a simulation system. Specifically, the present invention relates to a simulation system that predicts molding defects of resin products manufactured by injection molding.

  Resin products such as automobile bumpers and garnishes are formed by preparing a mold having a product-shaped cavity and injection-molding a thermoplastic resin into the mold. More specifically, in this injection molding, first, a movable mold is clamped to a fixed mold, and a product-shaped cavity is formed between the movable mold and the fixed mold. Next, the molten resin is injected at a predetermined injection pressure by an injection device, and the molten resin is filled into the cavity. In addition, a holding pressure is applied when filling the molten resin. Thereafter, the molten resin is cooled while pressure is applied, then the mold is opened and the molded product is taken out.

  In such injection molding, in order to produce a high-quality molded product, the molding conditions such as the shape of the mold and the total amount of molten resin injected into the mold, flow rate, temperature, and pressure are appropriately set. There is a need. When the mold shape and molding conditions are not appropriate, unevenness (hereinafter referred to as “deformation”) occurs on the surface of the molded product.

  In recent years, therefore, a simulation system has been developed for verifying the occurrence of such deformation in advance (see Patent Document 1). More specifically, in the simulation system disclosed in Patent Document 1, the degree of deformation that occurs in a molded product is predicted by CAE analysis, and molding conditions are re-established until the degree of deformation falls within a predetermined value. Repeat the setting and redesign of the mold with the CAD system. By predicting the occurrence of deformation by such a simulation system before actually manufacturing the mold, it is possible to reduce the cost and time required to manufacture the mold.

JP-A-10-138310

  By the way, in patent document 1, the unevenness | corrugation amount from the reference surface of a molded article is defined as a degree of deformation, and furthermore, the degree of deformation is defined as a wall thickness value, a pressure integral value, an inflow temperature, a pressurizing time, and the like. Calculation is based on the results obtained from the CAE analysis. However, the degree of deformation calculated by the simulation in this way is not capable of accurately reproducing the actual deformation, and therefore, it is desired that the degree of deformation can be predicted with higher accuracy.

  An object of this invention is to provide the simulation system which can grasp | ascertain generation | occurrence | production of a molding defect with high precision.

  The present invention provides a simulation system (for example, a simulation system 1 described later) that simulates a process of manufacturing a resin product by injection molding and predicts the occurrence of molding defects in the resin product. This simulation system includes a flow analysis execution means (for example, a calculation device 3 described later and steps S4 to S8 described later) that performs flow analysis of a molten resin injected under a predetermined molding condition for a predetermined product shape. Execution means), and based on the result of the flow analysis, an actual mass calculation means for calculating an actual mass (Mi) for each element (Ei) of the filled molten resin (for example, an arithmetic device 3 described later, and Based on the result of the flow analysis and means for executing step S7 described later), and necessary mass calculating means for calculating the required mass (NMi) of the molten resin of each element (for example, arithmetic device 3 described later, and And means for calculating an ideal mass (IMi) of the molten resin of each element (for example, arithmetic unit 3 described later, and step described later). 11) and an index (DIi) calculated by dividing a deviation between the actual mass and the required mass of each element by the ideal mass, and determining a molding defect for each element. Defective molding determination means (for example, a calculation device 3 described later and a means related to execution of step S13 described later).

  According to this invention, the flow analysis of the molten resin injected under predetermined molding conditions is performed, and based on the result of the flow analysis, the actual mass of each element of the filled molten resin and the melting of each element Calculate the required mass of the resin. In addition, the ideal mass of the molten resin for each element is calculated, and an index is calculated by dividing the deviation between the actual mass of each element and the required mass by the ideal mass, and molding defects for each element are calculated based on this index. judge. Thus, by determining the molding failure of each element based on the index focusing on the amount of molten resin in each element, it is possible to grasp the occurrence of molding failure with high accuracy. In addition, by performing such a simulation and determining the shape and molding conditions of the mold so that molding defects do not occur, the time and cost required to create the mold can be reduced while improving the quality of the product. Can do.

  According to the simulation system of the present invention, it is possible to grasp the occurrence of molding defects with high accuracy by determining molding defects of each element based on an index focusing on the amount of molten resin in each element. In addition, by performing such a simulation and determining the shape and molding conditions of the mold so that molding defects do not occur, the time and cost required to create the mold can be reduced while improving the quality of the product. Can do.

1 is a block diagram showing a schematic configuration of a simulation system according to an embodiment of the present invention. It is a figure which shows the specific example of the metal mold | die shape data which concerns on the said embodiment. It is a figure which shows the specific procedure which manufactures a resin product by actual injection molding. It is a flowchart which shows the procedure which determines the shaping | molding defect of a molded article by the injection molding simulation which concerns on the said embodiment. It is a figure which shows the triangular element which concerns on the said embodiment. It is a figure which shows the structure of the PVT curve which concerns on the said embodiment. It is a figure which shows the result of the injection molding simulation which concerns on the said embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of a simulation system 1 according to the present embodiment.

  The simulation system 1 includes an input device 2 through which an operator inputs various data and commands, an arithmetic device 3 that executes various arithmetic processes, and a display device 6 that displays an image. As will be described in detail below, the simulation system 1 simulates the process of manufacturing a resin product by injection molding with the hardware configuration, and predicts the occurrence of molding defects in the resin product.

  The input device 2 includes hardware such as a keyboard and a mouse that can be operated by an operator. Data and commands input by operating the input device 2 are input to the arithmetic device 3.

  The display device 6 is configured by hardware such as a CRT or a liquid crystal display capable of displaying an image. On the display unit of the display device 6, for example, an image output from the arithmetic device 3 such as an image related to a result of an injection molding simulation described later is displayed.

  The arithmetic device 3 includes a storage device 4 composed of a RAM, a ROM, a hard disk, and the like, and a central arithmetic device that executes various programs based on data stored in the storage device 4 and data input from the input device 2 (CPU) 5 is included.

  The storage device 4 of the arithmetic device 3 stores various data referred to in the execution of simulation such as mold shape data, resin characteristic data, and molding condition data, in addition to a system program related to execution of an injection molding simulation described later. Has been.

Mold shape data refers to the three-dimensional shape data of a mold used for injection molding, and is designed or modified by a CAD system.
FIG. 2 is a diagram showing a specific example of mold shape data. In the present embodiment, a case where a bumper B of a vehicle as shown in FIG. 2 is manufactured by injection molding will be described as an example.
As shown in FIG. 2, in the mold shape data, in addition to the three-dimensional shape data related to the thickness and shape of the molded product, information on the positions of the plurality of gates G1, G2, G3, G4 from which the molten resin is injected, Information on the positions of the plurality of runners R1, R2, R3 is included.

  Returning to FIG. 1, the molding condition data includes data relating to the state of the molten resin and the mold when performing injection molding. The detailed configuration of the molding condition data will be described in detail later.

  The resin characteristic data refers to data relating to the characteristics of the resin used for injection molding. More specifically, the resin characteristic data includes the resin pressure, specific volume, and temperature in addition to data on the physical properties of the resin such as specific heat, thermal conductivity, solidification temperature, Young's modulus, and Poisson's ratio of the resin. Data relating to the associated PVT curve (see FIG. 6 below) is included.

FIG. 3 is a diagram showing a specific procedure for manufacturing a resin product by actual injection molding.
As shown in FIG. 3, the injection molding is mainly composed of three steps: (a) a filling step, (b) a pressure holding / cooling step, and (c) a mold drawing step.

  In the filling step, the movable mold 91 is clamped to the fixed mold 92, and the cavity C is formed between the movable mold 91 and the fixed mold 92. Furthermore, the molten resin is filled into the cavity C under predetermined molding conditions by an injection device (not shown). Here, when the molten resin is filled, a predetermined pressure is applied to the molten resin in the cavity C.

In the pressure holding / cooling step, the molten resin is cooled while pressure is applied to the molten resin in the cavity C. As a result, the molten resin gradually cures and contracts.
In the mold drawing step, after the molten resin is cured, the mold is opened and the molded product in the mold is taken out.

  In the injection molding procedure as described above, the cause of the occurrence of deformation in the molded product is considered to be mainly due to the insufficient amount of the molten resin. In other words, in the filling step, as described above, in view of the fact that the molten resin shrinks in the subsequent pressure-holding / cooling step, the molten resin is filled in a larger amount than the volume of the cavity C by filling the molten resin while holding the pressure. Fill with resin. However, if the amount of molten resin to be filled here is less than the required amount, the molded product shrinks more than the originally required thickness, resulting in deformation. Therefore, as will be described in detail below, in the injection molding simulation of the present invention, a molding defect is determined by paying particular attention to the amount of molten resin filled in a virtually set mold.

Hereinafter, the injection molding simulation of this embodiment will be described in detail.
FIG. 4 is a flowchart showing a procedure for determining a molding defect of a molded product by injection molding simulation.

In step S1, the mold shape data is read from the storage device,
In step S2, resin characteristic data is read from the storage device.

  In step S3, molding condition data is set. As the molding condition data, data stored in a storage device is used, or data input by an input device is used. Specifically, in this molding condition data, in addition to the injection temperature, injection flow rate, and injection pressure of the molten resin when injecting the molten resin into the cavity, the mold temperature, the pressure holding profile, etc. will be described later. Contains data necessary for flow analysis.

  Next, in steps S4 to S8, flow analysis of the molten resin injected into the virtually set mold is executed based on the input mold shape data, resin characteristic data, and molding condition data. In this flow analysis, the behavior and state change of the molten resin in the above-described filling process and pressure holding / cooling process are analyzed in time series. The output of the flow analysis includes, for example, the mass distribution, pressure distribution, and temperature distribution of the molten resin in the mold. Hereinafter, specific steps will be described.

In step S4, injection of molten resin is started under the molding conditions set in the above steps.
In step S5, it is determined whether or not the pressure of the molten resin in all the regions in the mold exceeds a predetermined threshold value. This threshold value is a threshold value set to determine whether or not the molten resin is filled in the mold with sufficient pressure. More specifically, for example, it is set according to the plate pressure and shape within a range of about 20 to 30 MPa. If this determination is YES, it is determined that the filling of the molten resin is completed, and the process proceeds to step S6. If this determination is NO, it is determined that the molten resin is flowing in the mold, and the injection of the molten resin is continued.

In step S6, the process of ending injection of the molten resin in response to the determination that the filling of the molten resin is completed in step S5, and further starting the cooling of the molten resin in the mold, and changing the state of the molten resin Is analyzed.
Specifically, the molten resin in the mold is divided into a plurality of triangular elements Ei (i = 1, 2,...) As shown in FIG. 5, and the state of the molten resin for each element Ei (resin temperature Ti, The time change of the resin mass Mi and the resin pressure Pi) is analyzed.

  In step S7, the resin temperature Ti and the resin mass Mi at the time when the pressure Pi becomes “0” are recorded for each element Ei. The time when the pressure Pi becomes “0” is set as a solidification time ti. In addition, the resin mass Mi at the solidification time ti is hereinafter referred to as an actual mass Mi.

  In step S8, whether or not the pressure Pi of all the elements Ei (i = 1, 2,...) Has become “0”, that is, the recording of the resin temperature Ti, the actual mass Mi, and the solidification time ti for all the elements Ei is completed. It is determined whether or not. If this determination is YES, the process proceeds to step S9, and if NO, the process proceeds to step S7.

In step S9, the element volume Vi of each element Ei, the specific volume SVi at the temperature Ti of each element Ei, and the normal temperature (for example, 25 ° C.), that is, the specific volume SV0i after solidification of the molten resin are calculated.
Specifically, as shown in FIG. 5, the element volume Vi of each element Ei is calculated by multiplying the surface area Si of each triangular element Ei by the thickness Wi.
Further, the specific volume SVi at the temperature Ti and the specific volume SV0i after solidification are calculated based on a PVT curve associating the pressure, specific volume, and temperature of the molten resin as shown in FIG.

In step S10, the required resin mass NMi of the molten resin of each element Ei is calculated. This required resin mass NMi is a physical quantity indicating the mass of the element Ei when the element Ei is filled with the molten resin in the state at the time ti. As shown in the following formula (1), the element volume Vi is expressed as a specific volume SVi. Calculated by dividing.
Necessary mass NMi = element volume Vi / specific volume SVi (1)

In step S11, the ideal resin mass IMi after solidification of the molten resin of each element Ei is calculated. This ideal resin mass IMi is a physical quantity indicating the mass of the resin of the element Ei after solidification of the molten resin. As shown in the following formula (2), the element volume Vi is expressed by a specific volume SV0i after solidification of the molten resin. Calculated by dividing.
Ideal resin mass IMi = element volume Vi / specific volume SV0i (2)

In step S12, as shown in the following formula (3), a value obtained by subtracting the required resin mass NMi from the actual resin mass Mi is divided by the ideal resin mass IMi, thereby indicating the degree of deformation in each element Ei. The foam index DIi is calculated.
Deformation index DIi = (real resin mass Mi−required resin mass NMi)
/ Ideal resin mass IMi (3)

  In the above formula (3), the numerator of the deformation index DIi indicates the excess or deficiency of the filled resin as a result of injection molding. Therefore, when the actual resin mass Mi is insufficient with respect to the required resin mass NMi, the deform index DIi becomes a negative value. For this reason, the larger the degree of deformation, the smaller the deformation index DIi. Further, the division index DIi can be defined as a dimensionless index indicating the degree of excess or deficiency of the resin of each element by dividing by the ideal resin mass IMi indicating the theoretical value of the resin amount after solidification.

  In step S13, a molding defect is determined for each element Ei based on the deformation index DIi. More specifically, the deformation index DIi is compared with a predetermined determination threshold value TH. When the deformation index DIi is smaller than the determination threshold value TH, the deformation has occurred in the element Ei, that is, there is a molding defect. It is determined that it has occurred.

  Here, when a molding defect is determined, that is, when there is an element for which the deform index is determined to be smaller than the determination threshold value TH, basically, the deform index for all elements exceeds the determination threshold value TH. Until then, the correction of the molding condition data and the mold shape data and the execution of the above steps S1 to S13 are repeated.

FIG. 7 is a diagram showing the results of the injection molding simulation as described above.
The vertical axis represents the deformation index of each element calculated from the simulation results, and the horizontal axis represents the actual deformation amount of each element.

As shown in this figure, there is a clear correlation between the deformation index calculated by simulation and the actual deformation amount. That is, the amount of deformation increases as the deformation index decreases. Therefore, the effectiveness of determining the occurrence of deformation using the deformation index was confirmed.
In addition, the determination threshold TH for the above-described deformation index is set so that the actual deformation amount becomes smaller than a desired value after deriving the correlation between the deformation index and the actual deformation amount as described above. Is done.

  According to this embodiment, the flow analysis of the molten resin injected under predetermined molding conditions is performed, and based on the result of the flow analysis, elements of the molten resin filled in a virtually set mold The actual resin mass Mi for each Ei and the required resin mass NMi of the molten resin of each element Ei are calculated. Furthermore, the ideal resin mass IMi of the molten resin of each element Ei is calculated, and the deformation index DIi is calculated by dividing the deviation between the actual resin mass Mi of each element Ei and the required resin mass NMi by the ideal resin mass IMi. Then, a molding defect for each element Ei is determined based on the deformation index DIi. Thus, by determining the molding failure of each element Ei based on the deformation index DIi focusing on the amount of molten resin in each element Ei, it is possible to grasp the occurrence of molding failure with high accuracy. In addition, by performing such a simulation and determining the shape and molding conditions of the mold so that molding defects do not occur, the time and cost required to create the mold can be reduced while improving the quality of the product. Can do.

  As described above, the simulation system according to the present embodiment prepares basic molding condition data and mold shape data, executes the injection molding simulation in steps S1 to S13, and performs molding condition data and mold shape data. By repeating this correction several times, it is possible to finally determine molding conditions and mold shapes free from molding defects. In other words, the simulation system of the present embodiment can determine molding conditions and mold shapes that are free from molding defects without performing trial manufacture of actual molds and trial manufacture of products using the prototype molds. However, by using the simulation system of this embodiment in combination with an actual mold and trial manufacture of a product, there are cases where the molding conditions and mold shape without molding defects can be determined more efficiently.

  In this case, it is preferable that the injection molding simulation is executed once and the mold and product prototype results are reflected when the molding condition data and the mold shape data are corrected based on the determination result. More specifically, first, a mold is prototyped based on the determination result of the injection molding simulation, and a product is prototyped using this mold. Then, the plate thickness of each element in the prototype is measured, and the molding condition data and the mold shape data are corrected based on the measured values. By reflecting the actual prototype information in the data correction as described above, it is possible to determine molding conditions and mold shapes that are more efficient, that is, without molding defects in a short time.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements and the like within a scope that can achieve the object of the present invention are included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... Simulation system 2 ... Input device 3 ... Arithmetic device 4 ... Memory | storage device 5 ... Central processing unit 6 ... Display apparatus

Claims (1)

A simulation system that simulates the process of manufacturing a resin product by injection molding and predicts the occurrence of molding defects in the resin product,
A flow analysis execution means for performing a flow analysis of a molten resin injected under a predetermined molding condition for a predetermined product shape;
Based on the result of the flow analysis, an actual mass calculating means for calculating an actual mass for each element of the filled molten resin;
Based on the result of the flow analysis, required mass calculating means for calculating the required mass of the molten resin of each element;
Ideal mass calculating means for calculating the ideal mass of the molten resin of each element;
A molding defect determining means for determining a molding defect for each element based on an index calculated by dividing a deviation between the actual mass and the necessary mass of each element by the ideal mass. A simulation system.

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