JP4032755B2 - Molding simulation method, molding simulation apparatus, molding simulation program, and computer-readable recording medium recording the molding simulation program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a molding simulation method, a molding simulation apparatus, a molding simulation program, and a computer-readable recording medium in which the molding simulation program is recorded.
[0002]
[Prior art]
A technique for producing a molded product having a required shape by filling a molten material into a mold, such as casting / die casting using cast iron / aluminum or resin injection molding, is widely used.
[0003]
Explaining by taking die casting as an example, the occurrence of defects includes poor entrainment of air or the like, poor hot water, poor sink marks, and the like. A particularly serious defect is a entanglement defect based on a entanglement defect. For example, when forming a molded product having a thin and complicated shape, it is necessary to shorten the filling time in order to improve the surroundings of the molten material into the mold. However, when the filling time of the molten material in the mold is shortened, turbulent flow is generated, and a gas such as air is entrained in the mold, so that entrainment defects are likely to occur.
[0004]
In order to eliminate this defect, it is necessary to optimize the shape of the molded product, the molding method (runner, gate, overflow), injection conditions (low speed, switching timing, high speed, etc.), and mold temperature control.
[0005]
However, molded products manufactured by the molten material filling and molding method are usually three-dimensionally complicated and thin, and the flow of molten material and solidification are extremely complex and short-term phenomena, which are quite unclear. It is not possible, and therefore finding the proper conditions is not easy. It is not easy to systematically analyze the entrainment defects experimentally, and the current situation is that trial and error are repeated.
[0006]
By the way, with the recent improvement in computer computing power, the scope of application of molding simulation on a computer with respect to the behavior of a molten material when the molten material is filled in a mold is expanding. Molding simulation aims to deepen understanding of the flow of molten material and solidification behavior, and is expected as a useful means for searching for suitable molding conditions.
[0007]
As a molding simulation method, in addition to flow analysis of the molten material, flow analysis is also performed for the gas in the cavity region in the mold, and analysis taking into account the pressure of the gas in the entrainment defect will generate entrainment defects to some extent Can be predicted. However, it is not practical to perform analysis on the two-phase flow of the molten material and the gas by using an actually complicated mold, which requires a great amount of calculation time. In addition, even if the calculation capability is improved in the future and the analysis can be performed promptly, it is beneficial to simply perform the calculation in the analysis and shorten the analysis time.
[0008]
As a conventional molding simulation method, a hot water flow simulation method in consideration of a solidification phenomenon, and a method for predicting a defect occurrence position such as a hot water failure with a defective filling portion is disclosed in Japanese Patent Laid-Open No. 2001-271734. . This is a method of analyzing the behavior of voids generated by bubbles entrained in the molten material when the molten material is filled in the mold, using an electronic computer, and based on the past experience and knowledge of the operator Japanese Patent Laid-Open No. 5-337999 discloses a method of selecting a minute space in which occurrence of a defect occurs, generating trace particles in the minute space every predetermined time, and tracing the generated trace particles to predict the occurrence position of entrainment defects. It is disclosed in the gazette. Further, a method for calculating a portion where the molten material joins in the mold and estimating that a entanglement defect occurs in the joining portion is disclosed in a casting (Otsuka et al., Vol. 60 (1988), No. 12). .
[0009]
As a general method, there is a method of visualizing the simulation result of the flow of the molten material and visually checking the flow pattern to estimate the entrainment portion.
[0010]
[Problems to be solved by the invention]
However, the method disclosed in Japanese Patent Application Laid-Open No. 2001-271734 cannot predict the occurrence of entrainment defects not related to the solidification phenomenon. The accuracy changes greatly and does not go out of trial and error, and the method of Otsuka et al. Cannot cope with the size of the entrainment defect and the movement after the occurrence, and the method of checking visually is in the case of a complicated shape. However, there is an inconvenience that accurate determination cannot be made and it is difficult to predict the size and movement of the defect.
[0011]
Therefore, in the present invention, a molding simulation method and a molding simulation apparatus that can accurately estimate the entrainment defects that occur when filling the mold of the molten material without depending on the operator's experience, a molding simulation program that realizes them on a computer, and It is an object to be solved to provide a computer-readable recording medium in which the program is recorded.
[0012]
[Means for Solving the Problems]
As a result of intensive studies by the present inventors for the purpose of solving the above problems, in the conventional molding simulation method, entrainment defects generated during the analysis disappear during the subsequent analysis of the flow of the molten material, and finally It was found that it was not reflected in the results of the analysis. As a result, it has been found that the occurrence of entrainment defects cannot be accurately predicted in the analysis of the flow of the molten material. As described above, in order to prevent the entrainment defects generated during the analysis from disappearing, the flow of the gas in the cavity region in the mold is also analyzed and the gas pressure in the entrainment defects is also taken into account. For example, it can be realized to some extent. However, analysis of the two-phase flow of the molten material and the gas using an actually complex mold requires a lot of calculation time and is not practical. In addition, it is beneficial to perform the calculation in the analysis simply even if the calculation capability is improved in the future and the analysis can be performed promptly.
[0013]
Based on this knowledge, the present inventors locate the shape of the mold used for molding the molten material on the coordinate system, and create an element for dividing the space of the coordinate system into a plurality of minute elements, For each of the cavity elements, a pre-processing step comprising: defining a mold element when located in the mold area of the mold; and defining an element as a cavity element when located in the cavity area of the mold; A filling analysis step for performing a filling analysis of the molten material, and each of the cavity elements not filled with the material is newly surrounded by the mold element and / or the cavity element filled with the material A closed region detecting step for detecting the closed region and associating information on the amount of gas confined in the closed region with the closed region; When the region is filled with the molten material and disappears, the gas amount information associated with the closed region disappeared is associated with the point on the coordinate where the closed region disappeared, and in the filling analysis step the molten material The present invention has invented a molding simulation method comprising an analysis step having a virtual winding point setting step for setting a virtual winding point that moves according to a flow velocity.
[0014]
In other words, once the entrapment defect that has occurred in the cavity element is detected as a closed region surrounded by the mold element, etc., and the amount of gas contained therein is associated with the closed region, the size of the entrainment defect that occurs The amount of gas confined in the closed region that affects the pressure can be maintained during the analysis. When the closed region finally disappears due to the filling of the molten material, a virtual entrainment point having the amount of gas trapped inside the closed region as information is set as the point where the closed region disappears, and the flow of the molten material Move with. By analyzing as described above, it is possible to accurately analyze the position of the entrainment defect that occurs when there is a gas entrained in the closed region or the virtual entrainment point remaining after the final molten material filling analysis. The size of the entrainment defect can be estimated from the amount of gas associated with the closed region or the virtual entrainment point.
[0015]
In the closed region detection step, a region where the closed region is newly divided into two or more is newly detected again as the closed region, and as the gas amount information associated with the newly detected closed region, Preferably, the method includes a step of dividing the gas amount information associated with the closed region before the division according to the newly detected volume of the closed region (Claim 2). By considering that the closed region once detected is divided again after that, it is possible to obtain a more realistic analysis result.
[0016]
Moreover, it is preferable to have the analysis result display process which displays the said virtual entrainment point with the said gas amount information matched with the said analysis process (Claim 3). By displaying the virtual entrainment point together with the associated gas amount information, the simulation result can be easily understood by the operator, and more appropriate molding conditions and the like can be set.
[0017]
Furthermore, the molding simulation apparatus of the present invention that solves the above problems can be an apparatus that realizes each step of the above-described molding simulation method (claims 4 to 6).
[0018]
Specifically, the shape of the mold used for molding the melted material is positioned on the coordinate system, element creation means for dividing the space of the coordinate system into a plurality of microelements, and each of the microelements, A preprocessing means having a mold element when located in the mold area and an element defining means defining a cavity element when located in the cavity area of the mold; and for each of the cavity elements, For each of the filling analysis means for performing a filling analysis and the cavity element not filled with the material, a closed region newly surrounded by the mold element and / or the cavity element filled with the material is detected; Closed area detection means that associates information on the amount of gas trapped in the closed area with the closed area, and the closed area is filled with molten material and disappears In this case, the gas amount information associated with the closed region disappears in correspondence with the point on the coordinate where the closed region disappears, and a virtual entrainment point that moves according to the molten material flow velocity is set in the filling analysis means. A molding simulation apparatus comprising: an analysis means having a virtual entrainment point setting means for performing the above-mentioned (claim 4).
[0019]
Then, the closed region detection means newly detects a region where the closed region is newly divided into two or more again as the closed region, and as the gas amount information associated with the newly detected closed region, It is preferable to include means for dividing the gas amount information associated with the closed region before the division according to the newly detected volume of the closed region.
[0020]
Moreover, it is preferable to have an analysis result display means for displaying the virtual entrainment point together with the associated gas amount information.
[0021]
Furthermore, the molding simulation program of the present invention that solves the above-described problems can be a program that implements each step of the above-described molding simulation method on a computer (claims 7 to 9). Moreover, it can be set as the computer-readable recording medium which recorded those programs (Claim 10).
[0022]
Specifically, the shape of the mold used for molding the melted material is positioned on the coordinate system, element creation means for dividing the space of the coordinate system into a plurality of microelements, and each of the microelements, A preprocessing means having a mold element when located in the mold area and an element defining means defining a cavity element when located in the cavity area of the mold; and for each of the cavity elements, For each of the filling analysis means for performing a filling analysis and the cavity element not filled with the material, a closed region newly surrounded by the mold element and / or the cavity element filled with the material is detected; Closed area detection means that associates information on the amount of gas trapped in the closed area with the closed area, and the closed area is filled with molten material and disappears In this case, the gas amount information associated with the closed region disappears in correspondence with the point on the coordinate where the closed region disappears, and a virtual entrainment point that moves according to the molten material flow velocity is set in the filling analysis means. A molding simulation program characterized by causing a computer to function as a molding simulation unit having an imaginary entrainment point setting unit that performs the analysis.
[0023]
Then, the closed region detection means newly detects a region where the closed region is newly divided into two or more again as the closed region, and as the gas amount information associated with the newly detected closed region, It is preferable to include means for dividing the gas amount information associated with the closed region before the division according to the newly detected volume of the closed region.
[0024]
Moreover, it is preferable to have an analysis result display means for displaying the virtual entrainment point together with the associated gas amount information (claim 9).
[0025]
DETAILED DESCRIPTION OF THE INVENTION
[Molding simulation method]
The present molding simulation method includes a pretreatment process, an analysis process, and other processes as required. The pre-processing step includes an element creating step and an element defining step, creating model data of the mold, and preparing for analysis of filling the molten material into the mold. The analysis process has a filling analysis step, a closed region detection step, and a virtual entrainment point setting step for the model data of the created mold. The present molding simulation method can be applied to casting such as die casting, plastic injection molding, and the like for simulation.
[0026]
(Pretreatment process)
<Element creation step>
The element creation step is a step in which the mold that is the object of the present molding simulation method is positioned on the coordinate system, and the space on the coordinate system is divided into a plurality of minute elements composed of polyhedrons. That is, this is a step of subdividing the space on the coordinate system into microelements for analysis.
[0027]
An appropriate coordinate system can be selected. In this space on the coordinate system, microelements are formed with a size as required. As a method of dividing into minute elements, a method of dividing with orthogonal hexahedron minute elements as employed in the finite difference method, and the shape of the elements relatively freely according to the casting mold model data as in the finite element method. There are methods that can be changed. The finite difference method is advantageous in that it can be easily divided into small elements and the analysis is mathematically simple.
[0028]
In addition, it is not necessary to define minute elements in the entire coordinate system space, and a necessary part (a part necessary in an analysis step described later such as a cavity region into which a molten material is injected and a mold region in contact with the cavity region) is provided. It is sufficient to define within a range that includes the minimum.
[0029]
The accuracy of analysis can be improved if the size of the minute element to be created is as small as possible, but more analysis time is required. Therefore, the size of the minute element can be appropriately determined from the required accuracy, the fundamental limitation of simulation, the analysis time, and the like. Note that the size of the microelements does not have to be the same for all portions, and the size can be changed depending on the analysis site. For example, it is preferable to improve the analysis accuracy by locally setting the size of the microelement small in the thin part of the molded product.
[0030]
By the way, in order to position the mold on the coordinate system, the shape of the mold needs to be converted into numerical data such as a CAD data type. The method for converting the shape of the mold into numerical data is not particularly limited. For example, the shape of the mold may be designed by CAD from the beginning, or the shape of the prototype may be digitized by some method such as a three-dimensional scanner. . Here, when the numerical value data of the type is created by CAD, it is necessary to read the type data created by CAD or the like and extract the outer shape data of the type. A known method can be used for the method. Further, the CAD data may be used as it is in this method.
[0031]
<Element definition step>
In the element definition step, each microelement defined in the element creation step is defined as a mold element when positioned in the mold area of the mold, and defined as a cavity element when positioned in the cavity area of the mold. It is a step to do. That is, it is a step of defining the attributes of each minute element for an analysis process described later and constructing the shape of the mold on the coordinate system with the minute elements.
[0032]
Note that this step is a step that is performed after the minute elements are defined in the above-described element creation step. However, this step is not necessarily performed after all the minute elements are defined, and each time one or more minute elements are defined. It is also possible to repeat this step and then perform the element creation step again.
[0033]
Here, the “mold area” of the mold is an area where the mold itself is formed, and the molten material does not flow. The “cavity area” of the mold is the flow of the molten material, and finally a molded product is formed. It means each area that is a part.
[0034]
Specifically, a method for defining each microelement as a mold element and a cavity element is not particularly limited, and a known method can be adopted. An example will be described below with reference to the drawings. FIG. 1 shows an enlarged view of the shape of the mold and a part of the microelements. For convenience of description and explanation, the drawings show the molds and microelements in two dimensions. The following explanation is also based on the two-dimensional figures, but the essence is not different from the three-dimensional one.
[0035]
As shown in FIG. 1, orthogonal coordinates are adopted as coordinates, and a square microelement 20 (the shape is not limited to a square in particular) on the coordinate system.・ Cubes and other polyhedrons of arbitrary shape can be exemplified as element shapes, and so on. In addition, the boundary line of the model model data is positioned on the coordinates.
[0036]
In FIG. 1, when the position of the center of gravity 21 of each microelement 20 exists in the mold area (shaded portion), the microelement 20 is defined as a mold element (hereinafter referred to as “M element”). When present in the cavity region, the minute element is defined as a cavity element (hereinafter referred to as “C element”). FIG. 2 shows a state in which each microelement 20 is defined as an M element and a C element. In FIG. 2, the center of gravity 21 existing in the mold region is represented by a white circle, and the center of gravity 21 present in the cavity region is represented by a black circle. The handling of the microelements 20 that do not correspond to either the mold region or the cavity region is not particularly limited, but it is preferable that the microelements 20 be defined so as not to be a computational load.
[0037]
(Analysis process)
<Filling analysis step>
The filling analysis step is a step of performing a filling analysis of the molten material for each of the C elements. That is, it is a step of analyzing the physical behavior of the injected molten material in the mold, and the physical behavior of the molten material for every minute time is analyzed for each minute element.
[0038]
There is no particular limitation on the basic method for analyzing the filling of molten metal. For example, known techniques and conventional techniques such as VOF (Volume of Fluid), SOLA, FAN, and improved methods thereof are applied. be able to.
[0039]
<Closed region detection step>
The closed region detection step is a step applied to the C element not filled with the material in the above-described filling analysis step (hereinafter referred to as “unfilled C element”). Specifically, a region composed of a C element filled with a material (hereinafter referred to as “filled C element”) and / or an unfilled C element surrounded by an M element is detected as a closed region. It should be noted that “unfilled C element” includes C elements that are partially filled with material but not completely filled, and “filled element” means a C element that is completely filled with material. You can also.
[0040]
An example of a method of detecting unfilled C elements completely surrounded by filled C elements and / or M elements in this step is as follows. For all unfilled C elements, the surrounding small elements from the unfilled C elements The search is sequentially performed until the filling C element or the M element is reached, and when the search is completed, a micro element other than “C element and M element” (for example, a vent hole for venting the gas in the mold) , A boundary with a microelement that is neither a C element nor an M element, or a coordinate space that is not divided into microelements, and so on. It can be determined that this is an area. When it is determined that a certain region of unfilled C elements is a closed region, the amount of gas in the closed region is obtained from the volume of the closed region and the pressure of the gas in the cavity region. The obtained gas amount is associated with the closed region as gas amount information. The gas pressure in the cavity region can be determined in consideration of the outflow amount of gas from the vent hole or the like.
[0041]
Further, when the closed region once detected is newly divided into two or more, the gas amount information associated with the closed region before the division is newly determined according to the volume of the newly detected closed region. It is preferable to have a step of allocating.
[0042]
This step may be performed with the same frequency as the above-described filling analysis step, or may be performed with a lower frequency than the filling analysis step.
[0043]
<Virtual entrainment point setting step>
The virtual entrainment point setting step is a step applied to each closed region detected in the closed region detection step. Specifically, when the closed region is completely filled with the molten material and disappears in the filling analysis step, a virtual entrainment point is set at a position on the coordinates where the closed region disappears. The set virtual entrainment point moves in the cavity according to the flow of the molten material in the above-described filling analysis step. That is, it moves according to the flow of the molten material calculated in the filling analysis step at the site where the virtual entrainment point is located. The calculation of the movement of the virtual entrainment point may be determined in consideration of the buoyancy in the molten material in addition to following the flow of the molten material. Further, the gas amount information associated with the closed region before disappearing is associated with the virtual entrainment point.
[0044]
When this analysis step is completed, it is determined that a defect having a size corresponding to the gas amount information associated with the virtual entrainment point exists at the position of the existing entrainment point.
[0045]
(Other processes)
In addition, the simulation method can have a solidification analysis step for simulating the solidification process of the molten material in the cavity in the mold in the analysis process. The solidification analysis step can be included in the analysis process described above. In addition, it is also possible to perform defect prediction analysis (shrinkage nest prediction, runner and bath boundary prediction, etc.), DC sleeve flow analysis, core gas generation analysis, residual stress analysis, and the like.
[0046]
By performing these analyzes together, not only the analysis of air entrainment, but overall, shrinkage nest, aim, mold temperature distribution, hot water boundary, hot water wrinkle, blister, residual strain, cracking, durability (static, Fatigue, impact), property prediction, and the like can be performed accurately and efficiently.
[0047]
Furthermore, examples of other steps that can be included in the method of the present embodiment include a step of outputting an analysis result and a step of displaying the analysis result.
[0048]
As the process of outputting the analysis result, for example, it can be output / saved in a file format that can be read by a unique format or other general-purpose CAD, or can be output to the process of outputting the above-described analysis result. is there.
[0049]
The step of displaying the analysis result is a step of visualizing the analysis result in the molding simulation method of the present embodiment. Visualization makes it easier to understand the analysis results.
[0050]
When the analysis result is output (visualized), the analysis result of the air entrainment analyzed in the analysis process (information on the size of the entrapment defect according to the gas amount information associated with the position of the virtual entrainment point) is also output (Visualization) is preferable.
[0051]
[Molding simulation equipment]
The molding simulation apparatus of the present invention will be described in detail below based on the embodiments. The molding simulation apparatus according to the present embodiment includes preprocessing means and analysis means. In addition, the molding simulation apparatus of the present embodiment can include other means as necessary. All of the means of the present embodiment can be realized as logic on a computer, and is preferably realized as logic on a computer.
[0052]
The preprocessing means has element creation means and element definition means, and is a means for preparing for the filling analysis of the molten material into the mold. The analysis means includes a filling analysis means, a closed region detection means, and a virtual entrainment point setting means.
[0053]
(Pretreatment means)
<Element creation means>
The element creating means is a means for positioning the mold to be analyzed by the forming simulation means on the coordinate system and dividing the space on the coordinate system into a plurality of microelements made of a polyhedron. That is, it is a means for subdividing the space on the coordinate system into small elements for analysis. Note that the description of this means is almost the same as that in the element creation step in the above-described molding simulation method, and therefore the above description is replaced with the description of this means.
[0054]
<Element definition means>
The element definition means defines each of the microelements defined in the element creation means as a mold element when positioned in the mold area of the mold, and as a cavity element when positioned in the cavity area of the mold. It is means to do. That is, the attribute of each microelement is defined for the analysis means described later, and the shape of the mold is constructed with the microelement on the coordinate system. Note that the description of this means is almost the same as that in the element definition step in the above-described molding simulation method, and therefore the above description is replaced with the description of this means.
[0055]
(Analysis means)
<Filling analysis means>
The filling analysis means is means for performing a filling analysis of the molten material for each of the C elements. That is, it is a means for analyzing the physical behavior of the injected molten material in the mold, and analyzes the physical behavior of the molten material for each minute time for each minute element. Note that the description of this means is almost the same as that in the filling analysis step in the above-described molding simulation method, and therefore the above description is replaced with the description of this means.
[0056]
<Closed area detection means>
The closed region detection means is a means applied to the C element not filled with the material in the above-described filling analysis means (hereinafter referred to as “unfilled C element”). Specifically, it is means for detecting a region composed of a C element filled with a material (hereinafter referred to as “filled C element”) and / or an unfilled C element surrounded by an M element as a closed region. Note that the description of this means is almost the same as that in the closed region detection step in the above-described molding simulation method, and therefore the above description is replaced with the description of this means.
[0057]
<Virtual entrainment point setting means>
The virtual entrainment point setting unit is a unit that is applied to each closed region detected by the closed region detection unit. Specifically, when the closed region is completely filled with the molten material and disappears by the analysis of the filling analysis unit, a virtual entrainment point is set at a position on the coordinates where the closed region disappears. Note that the description of this means is almost the same as that in the virtual entrainment point setting step in the above-described molding simulation method, and therefore the above description is replaced with the description of this means.
[0058]
(Other means)
As other means that can be included in the apparatus of this embodiment, as described in the simulation method described above, solidification analysis means for simulating the solidification process of the molten material in the cavity in the mold, and outputting the analysis result Examples of such means include means for displaying and analysis results. Note that the description of these means is almost the same as that in the above-described molding simulation method, and therefore, the above description will be replaced with the description of these means.
[0059]
[Molding simulation program]
The present molding simulation program is a logic that makes it possible to realize each means of the above-described molding simulation apparatus on a computer to be used, and is created in a format that can be executed on the computer. Further, this program may be recorded on a recording medium such as a CD-ROM. Since each component of the molding simulation program is substantially the same as the description of each component of the molding simulation method and apparatus described above, the above description is replaced with the description of the component.
[0060]
【Example】
Example 1
In the present embodiment, the molding simulation method of the present invention will be described in more detail based on a molding simulation method in die casting for analyzing the flow and solidification of a molten metal as a molten material. In this method, a casting mold as a mold is created by CAD, and a molding simulation is performed using model data of the casting mold.
[0061]
As shown in FIG. 3, this method is roughly divided into a preprocessing step S1 and an analysis step S2.
[0062]
(1) Pretreatment step S1
An orthogonal coordinate system having three axes of x, y, and z was adopted as the coordinate system. The mold model data of the casting mold is created as CAD data (mold model data creation S11).
[0063]
In order to simplify the description, a two-dimensional description represented by x and y is shown in FIG. The following description in two dimensions can be simply extended to three dimensions. First, the model model data D is arranged on a two-dimensional coordinate system. Then, the coordinate system is divided into minute elements in the x and y axis directions (element creation step S12). An element in which the position of the center of gravity of the minute element is located in the casting mold of the mold model data D is defined as an M element, and an element located in the cavity is defined as a C element (element definition step S13). In this casting mold, a gate G into which molten metal is injected is arranged at the lower right of the drawing, and a vent hole V for discharging air in the cavity region is arranged at the upper left.
[0064]
(2) Analysis step S2
(1) The analysis step S2 includes a filling analysis step S21, a solidification analysis step S22, a closed region detection step S23, and a virtual entrainment point setting step S24.
[0065]
The filling analysis step 21 analyzes the molten metal flow using a method called the SOLA-VOF method in the finite difference method, and the solidification analysis step S22 performs solidification analysis by the unsteady heat conduction calculation method. In the filling analysis step S21, the filling ratio of the molten metal is sequentially calculated for the C element at predetermined time intervals. Here, the C element is roughly divided into a filled C element filled with 100% molten metal and an unfilled C element with a molten metal filling amount of less than 100%. Note that. In this filling analysis step S21, the calculation is performed without considering the back pressure in the cavity region.
[0066]
In the closed region detection step S23, as shown in FIG. 4, an unfilled C element is arbitrarily selected from the C elements (S231). Then, adjacent microelements are sequentially searched starting from the selected unfilled C element.
[0067]
Next, an identification code that can identify the selected unfilled C element is given (S232). The adjacent microelements are detected for the unfilled C element with the identification code (S233). If the adjacent microelement is further an unfilled C element (S236), the adjacent unfilled C element is detected. Is also given the same identification code as the previous unfilled C element (S237). As a result, the unfilled C element finally given the same reference sign represents a continuous region of unfilled C elements, and the gas can freely move in that region.
[0068]
If the adjacent minute element is an unfilled C element, the search is continued for the adjacent minute element in the same manner for the adjacent unfilled C element (S233). When the adjacent microelement is an unfilled C element that has already been searched, or is an M element, a filled C element, or a microelement other than “C element and M element”, the search for further adjacent microelements is as follows. Instead, the type is recorded (S238). If all the adjacent minute elements are searched and there are no more unfilled C elements, a search is made as to whether there are any other unfilled unfilled C elements to which no identification code is added (S234). ) If there are unfilled unfilled C elements, a new unfilled C element is selected from the unfilled C elements (S231), and another identification code is attached to the unfilled C elements (S232). Similarly, the process of searching for adjacent minute elements is repeated.
[0069]
When the search is completed for all the unfilled C elements (S234), if the microelements adjacent to the unfilled C elements with the same identification code are only one of the filled C elements and the M elements, the same It is determined that the region composed of the unfilled C elements with the identification code attached is a closed region (S235). When it is first determined that the region is a closed region, the sum of the volumes of all unfilled C elements to which the sign is attached is obtained, and the gas pressure in the cavity region at that time is multiplied to obtain the gas amount information. Corresponding to an unfilled C element having an identification code (S235). As for the closed region to which the gas amount information is already associated, the gas amount information is not updated except when the closed region is divided as described later.
[0070]
On the other hand, when there is an unfilled C element that is adjacent to a microelement other than “C element and M element” among the unfilled C elements to which the same code is attached, the same identification code is assigned. It is determined that the area composed of unfilled C elements is not a closed area.
[0071]
In this embodiment, the cavity region is almost completely surrounded by the casting mold other than the vent hole. Therefore, the minute elements other than “C element and M element” mean the vent hole V portion.
[0072]
In the virtual entrainment point setting step S24, the unfilled C element in the closed region detected in the closed region detecting step S23 disappears when the unfilled C element disappears as a filled C element by the analysis in the further filling analysis step S21. This is a step of setting the virtual entrainment point associated with the associated gas amount information to the site where the closed region has disappeared. This virtual entrainment point moves in the cavity region according to the flow of the molten metal in the filling analysis step S21.
[0073]
The analysis step S2 will be specifically described below. When the molten metal is injected from the gate G into the cavity region in the casting mold shown in FIG. 5, the analysis proceeds in the filling analysis step S21, and after some time from the start of injection, from the gate G portion of the unfilled C element C. Some in the cavity region becomes the filled C element C ′ (FIG. 6). The closed region detection step S23 in this case will be described.
[0074]
Among all the unfilled C elements C, an arbitrary unfilled C element (for example, unfilled C element C1) is selected (S231), and an identification code is attached to the unfilled C element C1. When the adjacent small elements are searched for the selected unfilled C element C1 (S233), two elements in the y-axis direction are M elements, the x-axis downward direction is an unfilled C element C2, and the x-axis upward direction is a vent hole V. is there. No further search is performed for the microelements corresponding to the M element and the vent hole V, but for the unfilled C element C2 in the lower direction of the x-axis, further adjacent microelements are searched, and all the adjacent microelements are found. Search is performed until the element is other than the unfilled C element (S236 to 238).
[0075]
When the adjacent minute element is an unfilled C element, the same identification code is attached to the unfilled C element (S237). In the case of FIG. 6, all the unfilled C elements are continuous, and all are assigned the same identification code. In FIG. 6, since the unfilled C element C1 is adjacent to the vent hole V, it is determined that these unfilled C elements are not in the closed region (S235).
[0076]
As the analysis proceeds, the tip of the filled C element reaches C2 ′ (FIG. 7). In this case, since the area searched in order from the unfilled C element C1 is in contact with the vent hole V as in the case of FIG. 6, it is not a closed area, but the area including the unfilled C element C3 is filled with the M element. Since it is completely surrounded by the C element C ′, it is determined to be a closed region. If this closed region is detected for the first time at the time of FIG. 7, the amount of air in the closed region at this time is associated with this closed region as gas amount information. The amount of air can be calculated from the size of the closed region (44 minute elements in FIG. 7) and the pressure in the closed region (calculated from the amount of air in the cavity region and the amount discharged from the vent hole V). Multiply by
[0077]
As the analysis proceeds further and the closed region detected at the time of FIG. 7 is split into two as shown in FIG. 8, for each closed region at a rate according to the size of the split region, Distribute the gas information associated with the previous one. In FIG. 8, the closed area in the upper direction of the drawing is for 13 microelements, and the closed area in the lower direction is for 5 microelements, and the gas amount information previously associated is distributed at a ratio of 13: 5. To do.
[0078]
As the analysis further progresses, some of the detected closed regions may disappear as shown in FIG. This is because the back pressure is not considered in the filling analysis step S21. Here, if the filling analysis step S21 is performed in consideration of the back pressure, the size of the closed region is only gradually reduced as the molten metal is filled. There are cases where the area cannot be fully expressed. Moreover, calculation time increases by taking back pressure into consideration. When the closed area disappears, a virtual entrainment point setting step S24 sets a virtual entrainment point at a site where the closed area disappears. This virtual entrainment point moves according to the flow of the molten metal in the above-described filling analysis step S21.
[0079]
(3) Analysis result display process (not shown)
Finally, after the filling analysis step S21 and the solidification analysis step S22 are completed, the simulation result is visualized. In addition to visualizing the state of filling the molten metal into the cavity region, the predicted position of the air entrainment defect is displayed for the finally manufactured molded product. It is predicted that the air entrainment defect occurs at a point where the virtual entrainment point finally moves, in addition to the portion where the air is actually entrained to form a cavity (closed region) in the molded product. The size of the entrainment defect is predicted by the size of the gas amount information associated with the finally remaining virtual entrainment point or the closed region.
[0080]
The casting simulation method of the present embodiment can predict the entrainment defects with high accuracy that could not be performed conventionally, and can obtain more practical casting simulation results in a practical time.
[0081]
(Example 2)
A method for optimizing casting conditions using the molding simulation method of the present invention will be described below. This optimization method is shown in FIG. First, an initial product shape, a plan, and injection conditions as initial conditions are provisionally determined (S91).
[0082]
The hot water flow in the sleeve is analyzed under the conditions determined in S91 (S93). For the hot water flow analysis, the method of the first embodiment described above can be used as it is. As a result of the analysis, if the number and size of the entrainment defects are not within an acceptable range, the injection conditions in the sleeve are optimized (S92). As a method for optimizing the injection conditions, the injection speed is reduced to suppress the occurrence of entrainment defects, or the injection is performed at a low speed until the inside of the sleeve is filled with molten metal, and then the injection conditions are increased in two stages. To do. Further, it is preferable to increase the injection speed as much as possible within a range in which entrainment defects are acceptable.
[0083]
After optimizing the injection conditions in the sleeve, the product shape and plan are optimized. First, the molten metal flow of the product is calculated (S96). For this calculation, the method of Example 1 can be applied as it is. As a result, it is determined whether entrainment defects and other defects are acceptable (S97, S98). If the defect is unacceptable, the product shape and plan are optimized (S95). As a method of optimizing the product shape and method, the hot water flow is improved by changing the product shape or changing the gate position, vent hole position, vacuum condition, etc. at the place where the entrainment defect occurs. In addition, the mold temperature control, the molten metal temperature, the metal base material, etc. can be changed and optimized as necessary.
[0084]
Since the molding simulation method of the present invention can predict entrainment defects with high accuracy and simplicity, the casting conditions can be optimized in a very short time without actually creating a casting mold and performing an experiment. Is possible. As a result, lead time can be shortened, quality can be improved, and costs can be reduced.
[0085]
【The invention's effect】
As described above, according to the molding simulation method of the present invention, the entrainment of gas existing in the cavity region of the mold can be generated by expressing the entrainment of gas in the molten material as a closed region or a virtual entrainment point. It becomes possible to estimate with high accuracy. As a result, further improvement in accuracy in molding simulation can be achieved.
[0086]
Similarly, according to the molding simulation apparatus and the molding simulation program of the present invention, further improvement in accuracy in molding simulation can be achieved.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a method for defining microelements.
FIG. 2 is a diagram showing an example of a method for defining microelements.
FIG. 3 is a flowchart of a casting simulation method according to the first embodiment.
FIG. 4 is a flowchart of a closed region detecting step of the casting simulation method according to the first embodiment.
5 is a schematic view showing a state of a casting mold in Example 1. FIG.
6 is a schematic view showing a state of filling a molten metal into a casting mold in Example 1 and generation of a closed region due to filling. FIG.
7 is a schematic view showing a state of filling a molten metal into a casting mold in Example 1 and generation of a closed region due to filling. FIG.
FIG. 8 is a schematic view showing a state of filling a molten metal into a casting mold in Example 1 and generation of a closed region accompanying filling.
FIG. 9 is a schematic view showing a state of filling a molten metal into a casting mold in Example 1 and generation of a closed region due to filling.
FIG. 10 is a flowchart of the optimization method according to the second embodiment.
[Explanation of symbols]
D ... Type model data
C, C1, C2, C3 ... Unfilled cavity element (unfilled C element)
C ′, C2 ′... Filled cavity element (filled C element)
M ... type element (M element)
G ... Gate
V ... Benthole

Claims (10)

An element creating step for positioning a shape of a mold used for molding a molten material on a coordinate system and dividing a space of the coordinate system into a plurality of microelements;
For each of the microelements, an element defining step for defining a mold element when positioned in the mold area of the mold and a cavity element when positioned in the cavity area of the mold;
A pretreatment process with
A filling analysis step for performing a filling analysis of the molten material for each of the cavity elements;
For each of the cavity elements not filled with the material, a closed area newly detected by the mold element and / or the cavity element filled with the material is detected, and the gas trapped in the closed area is detected. A closed region detecting step for associating information of the amount with the closed region;
When the closed region is filled with molten material and disappears, the gas amount information associated with the disappeared closed region is associated with a point on the coordinate where the closed region disappeared, and the filling analysis step A virtual entrainment point setting step for setting a virtual entrainment point that moves according to the molten material flow speed in
And an analysis step having a molding simulation method. The closed region detecting step includes
A new region that is newly divided into two or more of the closed region is again detected as the closed region;
As the gas amount information associated with the newly detected closed region, the gas amount information associated with the closed region before being divided is divided according to the newly detected volume of the closed region. The molding simulation method according to claim 1 including a step. The molding simulation method according to claim 1, further comprising an analysis result display step of displaying the virtual entrainment point together with the associated gas amount information after the analysis step. An element creating means for positioning a shape of a mold used for molding a molten material on a coordinate system, and dividing a space of the coordinate system into a plurality of minute elements;
For each of the microelements, an element defining means for defining a mold element when positioned in the mold area of the mold and a cavity element when positioned in the cavity area of the mold;
Pre-processing means having
Filling analysis means for performing filling analysis of the molten material for each of the cavity elements;
For each of the cavity elements not filled with the material, the closed area newly detected by the mold element and / or the cavity element filled with the material is detected and the gas trapped in the closed area is detected. Closed region detecting means for associating information on the amount with the closed region;
When the closed region is filled with molten material and disappears, the gas amount information associated with the disappeared closed region is associated with the point on the coordinate where the closed region disappeared, and the filling analysis means A virtual entrainment point setting means for setting a virtual entrainment point that moves according to the molten material flow speed in
And a molding simulation apparatus characterized by comprising: The closed region detecting means includes
A new region that is newly divided into two or more of the closed region is again detected as the closed region;
As the gas amount information associated with the newly detected closed region, the gas amount information associated with the closed region before being divided is divided according to the volume of the newly detected closed region. The molding simulation apparatus according to claim 4, comprising means. Furthermore, the shaping | molding simulation apparatus of Claim 4 or 5 which has an analysis result display means which displays the said virtual entrainment point with the said gas amount information matched. An element creating means for positioning a shape of a mold used for molding a molten material on a coordinate system, and dividing a space of the coordinate system into a plurality of minute elements;
For each of the microelements, an element defining means for defining a mold element when positioned in the mold area of the mold and a cavity element when positioned in the cavity area of the mold;
Pre-processing means having
Filling analysis means for performing filling analysis of the molten material for each of the cavity elements;
For each of the cavity elements not filled with the material, the closed area newly detected by the mold element and / or the cavity element filled with the material is detected and the gas trapped in the closed area is detected. Closed region detecting means for associating information on the amount with the closed region;
When the closed region is filled with molten material and disappears, the gas amount information associated with the disappeared closed region is associated with the point on the coordinate where the closed region disappeared, and the filling analysis means A virtual entrainment point setting means for setting a virtual entrainment point that moves according to the molten material flow speed in
A molding simulation program for causing a computer to function as a molding simulation means having an analysis means. The closed region detecting means includes
A new region that is newly divided into two or more of the closed region is again detected as the closed region;
As the gas amount information associated with the newly detected closed region, the gas amount information associated with the closed region before being divided is divided according to the volume of the newly detected closed region. The molding simulation program according to claim 7 including means. Furthermore, the shaping | molding simulation program of Claim 7 or 8 which has an analysis result display means which displays the said virtual entrainment point with the said gas amount information matched. An element creating means for positioning a shape of a mold used for molding a molten material on a coordinate system, and dividing a space of the coordinate system into a plurality of minute elements;
For each of the microelements, an element defining means for defining a mold element when positioned in the mold area of the mold and a cavity element when positioned in the cavity area of the mold;
Pre-processing means having
Filling analysis means for performing filling analysis of the molten material for each of the cavity elements;
For each of the cavity elements not filled with the material, the closed area newly detected by the mold element and / or the cavity element filled with the material is detected and the gas trapped in the closed area is detected. Closed region detecting means for associating information on the amount with the closed region;
When the closed region is filled with molten material and disappears, the gas amount information associated with the disappeared closed region is associated with the point on the coordinate where the closed region disappeared, and the filling analysis means A virtual entrainment point setting means for setting a virtual entrainment point that moves according to the molten material flow speed in
And a computer-readable recording medium on which a molding simulation program is recorded, wherein the computer functions as a molding simulation means.

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