Forming quality prediction method and forming quality prediction device

Abstract

To provide a molding quality prediction technology with an excellent prediction accuracy of molding quality.SOLUTION: A molding quality prediction method includes: second step S102 of performing flow analysis of a shell mesh; third step S103 of extracting a plurality of nodes along a primary weld formed in a meeting region of two resin flows based on a result of a flow analysis; fourth step S104 of dividing a molded product into a plurality of virtual divided layers in a resin thickness direction and deriving a temporal change in a flow velocity vector in a central layer in the resin thickness direction among the plurality of virtual divided layers for each of a plurality of extracted nodes; fifth step S105 of estimating a position of a flow tip portion of a weld interface formed in a cross section in the resin thickness direction when molding of the molded product is completed based on changes in the flow velocity vector over time; and sixth step S106 of estimating a line connecting the flow tip portion of the weld interface corresponding to the plurality of nodes as a secondary weld.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a technique for predicting molding quality. [Background technology]

[0002] Patent Document 1 below discloses this type of molding quality prediction technology. This molding quality prediction technology converts CAD data of the molded product shape into a shell mesh and performs flow analysis. It extracts multiple nodes around where primary welds occur, calculates the time integral of the resin velocity at each node as the internal weld movement amount, and predicts the molded product quality based on this internal weld movement amount. However, this technology has the problem that it is difficult to estimate the internal state of the molded product in the thickness direction, making it difficult to accurately predict the molded product quality.

[0003] Therefore, Patent Document 2 below discloses a technique for estimating the shape of the weld interface inside a molded product. This technique estimates the presence or absence of a weld interface fold and the curvature of the weld interface at the center in the thickness direction based on time-series data of the amount of resin movement at each node around the primary weld and the thickness of the flow layer in a shell mesh flow analysis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-74786 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-207440 Summary of the Invention [Problem to be solved by the invention]

[0005] This type of molding quality prediction technology requires accurate estimation of the position and shape of the protruding tip at the center of the weld interface. However, when using this technology, it is difficult to accurately estimate the position of the protruding tip at the weld interface. Furthermore, when estimating the curvature at the center of the weld interface in the thickness direction, the arc-shaped portion of the weld interface is targeted, and an extremely narrow range of the protruding tip at the center of the weld interface is approximated as part of the arc, making it difficult to evaluate a wide range of the weld interface.

[0006] The present invention has been made in view of the above-mentioned problems, and aims to provide a forming quality prediction technique that has excellent forming quality prediction accuracy. [Means for solving the problem]

[0007] One aspect of the present invention is A molding quality prediction method for predicting the quality of a molded product formed by resin injection molding, comprising: a flow analysis step of performing a flow analysis of a shell mesh based on the shape data of the molded product; a node extraction step of extracting a plurality of nodes along a primary weld formed in a meeting region of the two resin flows based on the flow analysis result in the flow analysis step; a flow velocity vector derivation step of dividing the molded product into a plurality of virtual divided layers in a resin thickness direction, and deriving a change over time in a flow velocity vector in a central layer in the resin thickness direction among the plurality of virtual divided layers for each of the plurality of nodes extracted in the node extraction step; a weld interface estimation step of estimating the position of a flow leading end of a weld interface formed on a cross section in the resin thickness direction at the completion of molding of the molded product based on the change over time of the flow velocity vector derived in the flow velocity vector derivation step; a secondary weld estimation step of estimating a line connecting the flow front ends of the weld interface estimated in the weld interface estimation step with those corresponding to the plurality of nodes as a secondary weld; The shape of the above weld interface is expressed as y=a×x 2 a quadratic curve approximation step of approximating the curve by a quadratic curve of +bx+c; a molding quality prediction step of predicting molding quality of the molded product based on the coefficient a of the quadratic curve approximated in the quadratic curve approximation step; A molding quality prediction method comprising: is located.

[0008] Another aspect of the present invention is A molding quality prediction device that predicts the quality of a molded product formed by resin injection molding, a flow analysis unit that performs a flow analysis of a shell mesh based on the shape data of the molded product; a node extraction unit that extracts a plurality of nodes along a primary weld formed in a meeting region of two resin flows based on the flow analysis results by the flow analysis unit; a flow velocity vector derivation unit that divides the molded product into a plurality of virtual divided layers in a resin thickness direction, and derives a change over time in a flow velocity vector in a central layer in the resin thickness direction among the plurality of virtual divided layers for each of the extracted nodes; a weld interface estimation unit that estimates the position of a flow leading edge of a weld interface that is formed on a cross section in the resin thickness direction at the completion of molding of the molded product based on the change over time of the flow velocity vector; a secondary weld estimation unit that estimates a line connecting the flow front ends of the weld interface corresponding to the plurality of nodes as a secondary weld; The shape of the above weld interface is expressed as y=a×x 2 a quadratic curve approximation part that approximates the curve by a quadratic curve of +bx+c; a molding quality prediction unit that predicts the molding quality of the molded product based on the coefficient a of the quadratic curve approximated by the quadratic curve approximation unit; A molding quality prediction device comprising: is located. [Effects of the Invention]

[0009] In the molding quality prediction method of the above aspect, the flow analysis step performs a shell mesh flow analysis based on the shape data of the molded product. The node extraction step extracts multiple nodes along a primary weld formed at the meeting area of ​​two resin flows based on the flow analysis results from the flow analysis step. The flow velocity vector derivation step divides the molded product into multiple virtual division layers in the resin thickness direction, and derives a time-dependent change in the flow velocity vector in the central layer in the resin thickness direction among the multiple virtual division layers for each of the multiple nodes extracted in the node extraction step. The weld interface estimation step estimates the position of the flow front of the weld interface formed on the cross section in the resin thickness direction at the completion of molding of the molded product based on the time-dependent change in the flow velocity vector derived in the flow velocity vector derivation step. The secondary weld estimation step estimates a line connecting the flow fronts of the weld interface estimated in the weld interface estimation step that correspond to the multiple nodes as a secondary weld.

[0010] In the molding quality prediction device of the above aspect, a flow analysis unit executes processing corresponding to the flow analysis step. A node extraction unit executes processing corresponding to the node extraction step. A flow velocity vector derivation unit executes processing corresponding to the flow velocity vector derivation step. A weld interface estimation unit executes processing corresponding to the weld interface estimation step. A secondary weld estimation unit executes processing corresponding to the secondary weld estimation step.

[0011] According to the above-described aspects, the time-dependent change in the flow velocity vector in the central layer in the resin thickness direction among the multiple virtual divided layers is derived, and the position of the flow front of the weld interface is estimated based on this time-dependent change in the flow velocity vector, thereby improving the estimation accuracy. For example, this is more effective for accurately estimating the position of the flow front of the weld interface than estimating the shape of the weld interface based on the amount of resin movement in the resin flow direction and the flow layer thickness in the resin thickness direction. The position of the secondary weld can then be estimated from the position of the flow front of the weld interface. This makes it possible to visualize the positional relationship between the primary weld and the secondary weld, thereby enabling prediction of the molding quality of the molded product.

[0012] As described above, according to the above-described aspects, it is possible to provide a forming quality prediction technique that has excellent forming quality prediction accuracy. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a system configuration diagram of a molding quality prediction device according to a first embodiment. [Figure 2] 1A and 1B are diagrams for explaining primary welds and secondary welds that occur during the injection molding process of a molded product. [Figure 3] 1 is a flowchart showing a molding quality prediction method according to the first embodiment. [Figure 4] FIG. 4 is a diagram for explaining the first stage processing of the fourth step in FIG. 3; [Figure 5] FIG. 4 is a diagram for explaining the first stage processing of the fourth step in FIG. 3; [Figure 6] FIG. 4 is a diagram for explaining the second stage processing of the fourth step in FIG. 3; [Figure 7] FIG. 4 is a diagram for explaining the second stage processing of the fourth step in FIG. 3; [Figure 8] 4 is a diagram for explaining the processing of the fifth step and the sixth step in FIG. 3. [Figure 9] 4 is a diagram for explaining how a secondary weld is estimated by the processing in the fifth and sixth steps in FIG. 3. FIG. [Figure 10] FIG. 4 is a diagram for explaining the processing of the seventh step in FIG. 3; [Figure 11] 10A and 10B are diagrams for explaining the influence of the shape of the convex region of the weld interface on the orientation of talc contained in the resin. [Figure 12] FIG. 4 is a diagram showing text data of the prediction result in the eighth step in FIG. 3. [Figure 13] 5 is a diagram corresponding to FIG. 4 in the molding quality prediction method of the second embodiment. [Figure 14] 5 in the molding quality prediction method of the second embodiment. FIG. [Figure 15]7 is a diagram corresponding to FIG. 6 in the molding quality prediction method of the second embodiment. [Figure 16] 8 is a diagram corresponding to FIG. 7 in the molding quality prediction method of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Preferred embodiments of the above aspects are described below.

[0015] In the molding quality prediction method of the above aspect, it is preferable that the flow velocity vector is the second flow velocity vector obtained when the flow velocity vector in the resin flow direction is decomposed into a first flow velocity vector in the axial direction along which the primary weld extends and a second flow velocity vector in an orthogonal direction perpendicular to the axial direction.

[0016] According to this molding quality prediction method, by deriving the change in the second flow velocity vector over time in the flow velocity vector derivation step, it is possible to realistically reflect the actual change in the resin flow until the molding of the molded product is completed, thereby further improving the accuracy of estimating the position of the secondary weld in the secondary weld estimation step.

[0017] In the molding quality prediction method of the above aspect, the flow velocity vector is preferably a flow velocity vector in the resin flow direction.

[0018] According to this molding quality prediction method, the process in the flow velocity vector derivation step can be simplified by deriving the change over time in the flow velocity vector in the resin flow direction in the flow velocity vector derivation step.

[0019] In the molding quality prediction method of the above aspect, the shape of the weld interface is expressed as y = a × x 2 It is preferable that the method has a quadratic curve approximation step of approximating the product by a quadratic curve of +bx+c, and a molding quality prediction step of predicting the molding quality of the molded product based on the coefficient a of the quadratic curve approximated in the quadratic curve approximation step.

[0020] According to this molding quality prediction method, in the quadratic curve approximation step, the shape of the weld interface, which is particularly relevant to the molding quality of the molded product, is approximated by a quadratic curve, making it possible to accurately estimate the molding quality of the molded product.

[0021] In the molding quality prediction device of the above-mentioned aspect, it is preferable that the flow velocity vector is the second flow velocity vector obtained when the flow velocity vector in the resin flow direction is decomposed into a first flow velocity vector in the axial direction along which the primary weld extends and a second flow velocity vector in an orthogonal direction perpendicular to the axial direction.

[0022] This molding quality prediction device allows the flow velocity vector derivation unit to derive the change in the second flow velocity vector over time, making it possible to realistically reflect the actual change in the resin flow until the molding of the molded product is completed, thereby further improving the accuracy of the secondary weld position estimation by the secondary weld estimation unit.

[0023] In the molding quality prediction device of the above aspect, the flow velocity vector is preferably a flow velocity vector in the direction of resin flow.

[0024] According to this molding quality prediction device, the flow velocity vector derivation unit derives the change over time in the flow velocity vector in the resin flow direction, thereby simplifying the processing by the flow velocity vector derivation unit.

[0025] The molding quality prediction device of the above aspect calculates the shape of the weld interface by y=a×x 2 It is preferable to provide a quadratic curve approximation unit that approximates the product by a quadratic curve of +bx+c, and a molding quality prediction unit that predicts the molding quality of the molded product based on the coefficient a of the quadratic curve approximated by the quadratic curve approximation unit.

[0026] According to this molding quality prediction device, the quadratic curve approximation section uses a quadratic curve to approximate the shape of the weld interface, which is particularly relevant to the molding quality of the molded product, making it possible to accurately estimate the molding quality of the molded product.

[0027] A specific example of the molding quality prediction technique of this embodiment will be described below with reference to the drawings.

[0028] (Embodiment 1) As shown in Fig. 1, the molding quality prediction device 100 of the first embodiment is a device for predicting the quality of a molded product (hereinafter referred to as "molded product W") formed by resin injection molding. The molding quality prediction device 100 is preferably configured as a desktop or notebook personal computer (PC) having a monitor (display means), keyboard (input means), mouse (selection means), CPU, ROM, RAM, etc. Furthermore, the molding quality prediction device 100 is preferably connected to an external device via a communication network so as to be able to transmit and receive data.

[0029] As shown in Figure 2, during the injection molding process of molded product W, a primary weld L1 is formed on the surface of meeting area 1 where two resin flows, one at high pressure and one at low pressure, meet and collide. Then, when molding of molded product W is completed and the resin is in a hardened state, a secondary weld L2 is formed inside the resin. At this time, a weld interface 3 is formed on the cross section of molded product W in the resin thickness direction Y, and the line passing through the flow front end (protruding front end) 4 of this weld interface 3 becomes the secondary weld L2.

[0030] Returning to FIG. 1, the molding quality prediction device 100 includes a data processing unit 101, a storage unit 102, an input unit 103, and an output unit 104.

[0031] The memory unit 102 stores shape data D of the molded product W created by the designer, and also temporarily stores data generated by the processing of the data processing unit 101. CAD data is typically used as the shape data D. Various parameters used in the flow analysis described below are input from the input unit 103. The processing results of the data processing unit 101 are output from the output unit 104. Note that the output unit 104 can typically be a printer that outputs data by printing, a monitor that outputs data by display, a speaker that outputs data by voice, or the like.

[0032] The data processing unit 101 further includes a flow analysis unit 110, a node extraction unit 120, a flow velocity vector derivation unit 130, a weld interface estimation unit 140, a quadratic weld estimation unit 150, a quadratic curve approximation unit 160, and a molding quality prediction unit 170.

[0033] The flow analysis unit 110 has a function of performing a flow analysis of a shell mesh based on the shape data D of the molded product W. At this time, the process of converting the shape data D into a shell mesh and the flow analysis are performed using a commercially available CAE software program.

[0034] The node extraction unit 120 has a function of extracting multiple nodes along the primary weld L1 formed on the resin surface based on the flow analysis results obtained by the flow analysis unit 110. For ease of explanation, this embodiment illustrates an example in which three nodes n1, n2, and n3 (see FIG. 4) are extracted.

[0035] The flow velocity vector derivation unit 130 divides the molded product W into multiple virtual divided layers ("virtual divided layers S" described below) in the resin thickness direction Y, and has the function of deriving the change over time in the flow velocity vector ("flow velocity vector V" described below) in the central layer ("central layer Sa" described below) of the multiple virtual divided layers S in the resin thickness direction Y for each of the three extracted nodes n1, n2, and n3.

[0036] The weld interface estimation unit 140 has the function of estimating the position of the flow front end 4 of the weld interface 3 formed on the cross section in the resin thickness direction Y when the molding of the molded product W is completed, based on the change over time of the flow velocity vector V.

[0037] The secondary weld estimation unit 150 has a function of estimating as a secondary weld L2 a line connecting the flow fronts 4 of the weld interface 3 that correspond to three nodes n1, n2, and n3. In this case, the secondary weld L2 is a line that passes through the flow front 4 corresponding to the first node n1, the flow front 4 corresponding to the second node n2, and the flow front 4 corresponding to the third node n3.

[0038] The quadratic curve approximation part 160 approximates the shape of the convex region 3a on the tip side of the weld interface 3 by y=a×x 2 +bx+c, where a is a coefficient that represents the degree of opening of the parabola, b is a coefficient that represents the slope of the tangent at the y-intercept, and c is a coefficient that represents the y-intercept.

[0039] The molding quality prediction unit 170 has a function of predicting the molding quality of the molded product W based on the coefficient a of the quadratic curve approximated by the quadratic curve approximation unit 160.

[0040] Next, the molding quality prediction method of the first embodiment will be described with reference to Figures 3 to 11. This molding quality prediction method is for predicting the quality of a molded product W formed by injection molding of a resin.

[0041] 3, the molding quality prediction method of the first embodiment is achieved by sequentially executing steps from the first step S101 to the eighth step S108. One or more steps may be added to these steps as needed, or multiple steps may be combined. Furthermore, the order of the steps may be changed as needed.

[0042] 3 is a data creation step for creating shape data D of the molded product W. This first step S101 is executed by the designer of the molded product W. The created shape data D is stored in the storage unit 102 in FIG.

[0043] The second step S102 in Fig. 3 is a flow analysis step in which a flow analysis of a shell mesh is performed based on the shape data D of the molded product W. The flow analysis is performed by converting the shape data D into a shell mesh. This second step S102 is executed by a commercially available CAE software program installed in the flow analysis unit 110 in Fig. 1.

[0044] The third step S103 in Fig. 3 is a node extraction step for extracting multiple nodes along the primary weld formed on the resin surface based on the flow analysis results in the second step S102. This third step S103 is executed by the node extraction unit 120 in Fig. 1.

[0045] As shown in Figure 4, in this third step S103, a flow analysis model represented by a shell mesh having three nodes n1, n2, and n3 is exemplified. This flow analysis model simulates the molding process in which resin injected from two gate positions (not shown) flows so as to meet with each other, then cools and hardens, and finally becomes a molded product W. According to this flow analysis model, the position where the two resin flows meet is defined as a primary weld L1, and the position and shape of this primary weld L1 are identified. Therefore, the three nodes n1, n2, and n3 on the primary weld L1 can be extracted.

[0046] Note that Figure 4 illustrates an example in which all three nodes n1, n2, and n3 are located on the weld line L1. However, the three nodes n1, n2, and n3 may be located along the primary weld L1, and at least one of these three nodes n1, n2, and n3 may be located slightly off the weld line L1. For example, nodes may be selected by predetermining the distance from the weld line L1. The number and positions of the nodes can be selected by the user.

[0047] 3 is a flow velocity vector derivation step for deriving a change over time in the flow velocity vector in the central layer in the resin thickness direction Y of the molded product W. This fourth step S104 is executed by the flow velocity vector derivation unit 130 in FIG.

[0048] As shown in Fig. 5, in this fourth step S104, first, the molded product W is divided into multiple virtual divided layers S in the resin thickness direction Y. Then, for each of the three nodes n1, n2, and n3 extracted in the third step S103, the change over time in the flow velocity vector V in the central layer Sa of the multiple virtual divided layers S in the resin thickness direction Y is derived. In this case, the central layer Sa is defined as the layer that passes through the virtual center line A in the resin thickness direction Y. Furthermore, the flow velocity vector in the resin flow direction X is used as the flow velocity vector V.

[0049] In this fourth step S104, the flow velocity vector V of the central layer Sa is derived based on the flow velocity vector V of each virtual divided layer S. First, the flow velocity vector V of the virtual divided layer S on the surface side among the multiple virtual divided layers S is derived. Then, the flow velocity vectors V of the virtual divided layers S are sequentially derived from the surface side toward the central layer Sa. As a result, it becomes possible to derive the flow velocity vector V of the central layer Sa.

[0050] As shown in Figure 4, for example, it is estimated that the flow portion 2 corresponding to the first node n1 flows over time in the resin flow direction X according to the flow velocity vector V and reaches the first position P1 during the flow process. The same is true for the remaining second node n2 and third node n3. At this time, the line (shown by the dashed line) passing through the flow portion 2 at the first position P1 corresponding to the first node n1, the flow portion 2 at the first position P1 corresponding to the second node n2, and the flow portion 2 at the first position P1 corresponding to the third node n3 becomes the internal weld L1' formed in the central layer Sa during the flow process.

[0051] As shown in Figures 6 and 7, the multiple flow portions 2 on the internal weld L1' continue to flow over time in the resin flow direction X according to the flow velocity vector V. For example, it is estimated that the flow portion 2 corresponding to the first node n1 flows over time in the resin flow direction X according to the flow velocity vector V from the first position P1, and reaches the second position P2, which is the final position at the completion of molding. The same is true for the remaining second node n2 and third node n3. At this time, the flow portion 2 at the second position P2 becomes the flow front 4 of the weld interface 3.

[0052] 5 and 7 illustrate a case where the number of virtual dividing layers S, i.e., the number of divisions in the resin thickness direction Y, is 20, and the layer width of each virtual dividing layer S in the resin thickness direction Y is the same. However, the number of virtual dividing layers S and the layer width of each virtual dividing layer S in the resin thickness direction Y are not limited to these, and can be changed appropriately as needed.

[0053] Furthermore, Figure 6 illustrates an example in which the flow section 2 reaches the final position in two steps, passing through the first position P1 and then reaching the second position P2, but the flow section 2 may also reach the final position in three or more steps.

[0054] Furthermore, in the fourth step S104, the resin flow direction X at the initial position of the flow portion 2 (the position corresponding to the primary weld L1) and the resin flow direction X2 at the first position P1 of the flow portion 2 may be the same as each other or may be different from each other.

[0055] 3 is a weld interface estimation step that estimates the position of the flow front end 4 of the weld interface 3 that will be formed on the cross section of the resin in the thickness direction Y upon completion of molding of the molded product W, based on the change over time in the flow velocity vector V derived in the fourth step S104. This fifth step S105 is executed by the weld interface estimation unit 140 in FIG.

[0056] The sixth step S106 in Fig. 3 is a secondary weld estimation step in which a line connecting the flow fronts 4 of the weld interface 3 estimated in the fifth step S105 corresponding to the three nodes n1, n2, and n3 is estimated as a secondary weld L2 (see Figs. 2 and 6). This sixth step S106 is executed by the secondary weld estimation unit 150 in Fig. 1.

[0057] As shown in FIGS. 8 and 9, according to the sixth step S106, it is possible to estimate the position of the secondary weld L2 that is ultimately formed from the primary weld L1.

[0058] As shown in FIG. 10, the seventh step S107 in FIG. 3 determines the shape of the convex region 3a on the tip side of the weld interface 3 by y=a×x 2 This is a quadratic curve approximation step in which the weld interface 3 is approximated by a quadratic curve of +bx+c. The convex region 3a is a region of the weld interface 3 that corresponds to the selected region Sb (10 layers of the virtual divided layer S on the central side) on the resin thickness direction Y side. The quadratic curve is obtained when the position in the resin flow direction X is the x-coordinate and the position in the resin thickness direction Y is the y-coordinate. This seventh step S107 is executed by the quadratic curve approximation unit 160 in FIG. 1.

[0059] In this seventh step S107, it is preferable that the selected region Sb be set appropriately by the user in accordance with the shape of the weld interface 3. For example, since the shape of the weld interface 3 is easily disturbed on both ends in the resin thickness direction Y, the selected region S can be set to select a convex region 3a that is highly correlated to be approximated by a quadratic curve, omitting the shape on both ends.

[0060] 10 illustrates an example in which the number of virtual divided layers S in the selected region Sb is 10. However, the number of virtual divided layers S in the selected region Sb is not limited to this and can be changed appropriately as needed.

[0061] An eighth step S108 in Fig. 3 is a molding quality prediction step for predicting the molding quality of the molded product W based on the coefficient a of the approximate quadratic curve in the seventh step S107. This eighth step S108 is executed by the molding quality prediction unit 170 in Fig. 1.

[0062] Incidentally, talc is added as a functional agent to the resin used in the injection molding of the molded product W. It is known that the shape of the convex region 3a of the weld interface 3 affects the orientation of the talc. Here, Figure 11(a) shows the orientation of the talc T when the degree of opening of the convex region 3a of the weld interface 3 is relatively large. Figure 11(b) shows the orientation of the talc T when the degree of opening of the convex region 3a of the weld interface 3 is relatively small.

[0063] 11(a), when the degree of opening of the convex regions 3a is relatively large, the talc T is oriented along the resin thickness direction Y in the peripheral region 4a of the flow front 4, which is the resin meeting region. This makes it easier for the amount of shrinkage in the resin thickness direction Y to differ between the peripheral region 4a of the flow front 4 and the general region, which can result in large surface distortion being formed on the surface of the molded product W.

[0064] 11(b), when the degree of opening of the convex region 3a is relatively small, the amount of talc T oriented along the resin thickness direction Y in the peripheral region 4a of the flow front 4 is small. Therefore, it is difficult to generate a difference in the amount of shrinkage in the resin thickness direction Y between the peripheral region 4a of the flow front 4 and the general portion, and as a result, only small surface distortions are formed on the surface of the molded product W.

[0065] 12, in an eighth step S108, an evaluation formula E=k1×a+k2 is used to calculate the quality evaluation score E of the molded product W. By calculating the quality evaluation score E, the quality of the molded product W can be quantified.

[0066] Here, a in the evaluation formula is the coefficient of the quadratic curve, and k1 and k2 are both correction coefficients (>0). The coefficient a is a parameter that indicates the degree of divergence of the quadratic curve, and the larger the value, the smaller the degree of divergence of the quadratic curve. A linear formula is used as the evaluation formula. Therefore, the smaller the degree of divergence of the quadratic curve, the larger the coefficient a and the higher the quality evaluation score E.

[0067] The prediction result in the eighth step S108 is output as output data by the output unit 104. As this output data, for example, text data TD in which the quality evaluation score E and the evaluation result are stored in a database can be used.

[0068] 12 illustrates an example in which the text data TD indicates that the evaluation result is "good" when the quality evaluation score E is equal to or greater than the reference value of 3, and that the evaluation result is "poor" when the quality evaluation score E is below the reference value of 3. In this case, the evaluation results for parts number "T-A001" and "T-A003" are "good," and the evaluation result for part number "T-A002" is "poor." According to the text data TD, by displaying both the quality evaluation score E and the evaluation results, the user can grasp the quality of the molded product W at a glance.

[0069] According to the above-described first embodiment, the following effects can be obtained.

[0070] In the molding quality prediction device 100 of embodiment 1, the flow analysis unit 110 executes the processing of the second step S102, which is a flow analysis step. The node extraction unit 120 executes the processing of the third step S103, which is a node extraction step. The flow velocity vector derivation unit 130 executes the processing of the fourth step S104, which is a flow velocity vector derivation step. The weld interface estimation unit 140 executes the processing of the fifth step S105, which is a weld interface estimation step. The secondary weld estimation unit 150 executes the processing of the sixth step S106, which is a secondary weld estimation step.

[0071] In the above process, the change over time of the flow velocity vector V in the central layer Sa of the multiple virtual divided layers S in the resin thickness direction Y is derived, and the position of the flow front 4 of the weld interface 3 is estimated based on this change over time of the flow velocity vector V, thereby improving the estimation accuracy. For example, this is more effective for accurately estimating the position of the flow front 4 of the weld interface 3 than estimating the shape of the weld interface 3 based on the amount of resin movement in the resin flow direction X and the flow layer thickness in the resin thickness direction Y. The position of the secondary weld L2 can then be estimated from the position of the flow front 4 of the weld interface 3. This makes it possible to visualize the positional relationship between the primary weld L1 and the secondary weld L2, thereby enabling prediction of the molding quality of the molded product W.

[0072] As described above, according to the first embodiment, it is possible to provide a forming quality prediction technique that has excellent forming quality prediction accuracy.

[0073] According to the first embodiment, the flow velocity vector derivation unit 130 derives the change over time of the flow velocity vector V in the resin flow direction X in the fourth step S104, thereby simplifying the processing in the fourth step S104.

[0074] According to the first embodiment, in the seventh step S107, the quadratic curve approximation unit 160 approximates the shape of the weld interface 3, which is particularly relevant to the molding quality of the molded product W, with a quadratic curve, thereby making it possible to accurately estimate the molding quality of the molded product W. Approximating with a quadratic curve makes it possible to evaluate a wider range of the weld interface 3 than when estimating the curvature of the flow front 4 of the weld interface 3.

[0075] Hereinafter, other embodiments related to the above-described embodiment 1 will be described with reference to the drawings. In the other embodiments, the same elements as those in embodiment 1 are denoted by the same reference numerals, and the description of the same elements will be omitted.

[0076] (Embodiment 2) In the second embodiment, the same molding quality prediction device 100 (see FIG. 1) as in the first embodiment is used. However, in the second embodiment, the details of the flow velocity vector derivation step (processing corresponding to the fourth step S104 in FIG. 3) executed by the flow velocity vector derivation unit 130 are different from those in the first embodiment. The other configurations and methods are the same as those in the first embodiment.

[0077] The flow velocity vector derivation step executed by the flow velocity vector derivation unit 130 in the second embodiment will be described with reference to FIGS.

[0078] 13 and 14, the time-dependent change in the flow velocity vector in the central layer Sa in the resin thickness direction Y among the multiple virtual divided layers S is derived for each of the three nodes n1, n2, and n3. The flow velocity vector V in the resin flow direction X is decomposed into a first flow velocity vector Va and a second flow velocity vector Vb, and the second flow velocity vector Vb is used as the flow velocity vector. Here, the first flow velocity vector Va is the flow velocity vector in the axial direction along which the primary weld L1 extends. In contrast, the second flow velocity vector Vb is the flow velocity vector in the orthogonal direction X1, which is perpendicular to the axial direction along which the primary weld L1 extends.

[0079] In the flow velocity vector derivation step, the second flow velocity vector Vb of the central layer Sa is derived based on the second flow velocity vector Vb of each virtual divided layer S. First, the second flow velocity vector Vb of the virtual divided layer S on the surface side among the multiple virtual divided layers S is derived. Then, the second flow velocity vectors Vb of the virtual divided layers S are sequentially derived from the surface side toward the central layer Sa. As a result, it becomes possible to derive the second flow velocity vector Vb of the central layer Sa.

[0080] 13, for example, it is estimated that the flow portion 2 corresponding to the first node n1 flows over time in the orthogonal direction X1 according to the second flow velocity vector Vb and reaches the first position P1 during the flow process. The same is true for the remaining second node n2 and third node n3. At this time, the line (shown by the dashed line) passing through the flow portion 2 at the first position P1 corresponding to the first node n1, the flow portion 2 at the first position P1 corresponding to the second node n2, and the flow portion 2 at the first position P1 corresponding to the third node n3 becomes the internal weld L1' formed in the central layer Sa during the flow process.

[0081] At this time, since the second flow velocity vector Vb in the perpendicular direction X1 is used instead of the flow velocity vector V in the resin flow direction X, this internal weld L1' is formed at a different position from the internal weld L1' in embodiment 1 (see Figure 4).

[0082] 15 and 16, the multiple flow portions 2 on the internal weld L1' continue to flow over time in the orthogonal direction X1 according to the second flow velocity vector Vb. For example, it is estimated that the flow portion 2 corresponding to the first node n1 flows over time in the orthogonal direction X1 according to the second flow velocity vector Vb from the first position P1 to reach the second position P2, which is the final position at the completion of molding. The same applies to the remaining second node n2 and third node n3.

[0083] 14 and 16 illustrate a case where the number of virtual dividing layers S, i.e., the number of divisions in the resin thickness direction Y, is 20, and the layer width of each virtual dividing layer S in the resin thickness direction Y is the same. However, the number of virtual dividing layers S and the layer width of each virtual dividing layer S in the resin thickness direction Y are not limited to this, and can be changed appropriately as needed.

[0084] Furthermore, Figure 15 illustrates an example in which the flow section 2 reaches the final position in two steps, passing through the first position P1 and then reaching the second position P2, but the flow section 2 may also reach the final position in three or more steps.

[0085] Furthermore, in the flow velocity vector derivation step, the orthogonal direction X1 at the initial position of the flow section 2 (the position corresponding to the primary weld L1) and the orthogonal direction X1 at the first position P1 of the flow section 2 may be the same as each other or may be different from each other.

[0086] Although not specifically shown, in the second embodiment, the shape of the convex region 3a of the weld interface 3 is expressed as y=a×x 2 In the quadratic curve approximation step of approximating with a quadratic curve of +bx+c, the position in the orthogonal direction X1 is set as the x coordinate, and the position in the resin thickness direction Y is set as the y coordinate.

[0087] According to the second embodiment described above, by deriving the change over time of the second flow velocity vector Vb in the flow velocity vector derivation step (fourth step S104), it becomes possible to perform a simulation that realistically reflects the actual change in the resin flow up to the completion of molding of the molded product W. This further improves the accuracy of estimating the position of the secondary weld L2 in the secondary weld estimation step (sixth step S106). In addition, the same effects as those of the first embodiment are achieved.

[0088] The present invention is not limited to the above-described embodiment, and various applications and modifications are possible without departing from the scope of the present invention. For example, the following embodiments can be implemented by applying the above-described embodiment.

[0089] In the above-described embodiment, an example is given of a case in which both a process for estimating the position of the secondary weld L2 (hereinafter referred to as the "first process") and a process for approximating the shape of the weld interface 3 with a quadratic curve (hereinafter referred to as the "second process") are performed, but instead, only one of the first process and the second process may be performed.

[0090] In view of the above-described embodiments and various modifications, the present invention can adopt the following aspect 1.

[0091] (Aspect 1) A program for predicting the quality of a molded product formed by resin injection molding, a flow analysis process for performing a flow analysis of a shell mesh based on the shape data of the molded product; a node extraction process for extracting a plurality of nodes along a primary weld formed in a meeting region of the two resin flows based on the flow analysis results of the flow analysis process; a flow velocity vector derivation process that divides the molded product into a plurality of virtual divided layers in a resin thickness direction, and derives a change over time in a flow velocity vector in a central layer in the resin thickness direction among the plurality of virtual divided layers for each of the plurality of nodes extracted by the node extraction process; a weld interface estimation process for estimating the position of the flow leading edge of the weld interface formed on the cross section in the resin thickness direction at the completion of molding of the molded product based on the change over time of the flow velocity vector derived in the flow velocity vector derivation process; a secondary weld estimation process for estimating a line connecting the flow front ends of the weld interface estimated in the weld interface estimation process to those corresponding to the plurality of nodes as a secondary weld; A program that causes a computer to execute the following.

[0092] According to the above-mentioned first aspect, it is possible to provide a program with excellent prediction accuracy of molding quality. [Explanation of symbols]

[0093] 3 Weld Interface 4 Flow tip 100 Molding quality prediction device 110 Flow Analysis Department 120 Node Extraction Unit 130 Flow velocity vector derivation section 140 Weld interface estimation section 150 Secondary Weld Estimation Section 160 Quadratic curve approximation part 170 Molding Quality Prediction Department D Shape data L1 Primary Weld L2 Secondary Weld n1, n2, n3 nodes S Virtual division layer Sa central layer V: Flow velocity vector in the direction of resin flow Va First velocity vector Vb Second velocity vector W molded product X Resin flow direction X1: Orthogonal to the axial direction of the primary weld Y Resin thickness direction S102 2nd step (flow analysis step) S103 Third step (node ​​extraction step) S104 4th step (flow velocity vector derivation step) S105 5th step (weld interface estimation step) S106 6th step (secondary weld estimation step) S107 7th step (quadratic curve approximation step) S108 8th step (molding quality prediction step)

Claims

1. A molding quality prediction method for predicting the quality of a molded product formed by resin injection molding, comprising: a flow analysis step of performing a flow analysis of a shell mesh based on the shape data of the molded product; a node extraction step of extracting a plurality of nodes along a primary weld formed in a meeting region of the two resin flows based on the flow analysis result in the flow analysis step; a flow velocity vector derivation step of dividing the molded product into a plurality of virtual divided layers in a resin thickness direction, and deriving a change over time in a flow velocity vector in a central layer in the resin thickness direction among the plurality of virtual divided layers for each of the plurality of nodes extracted in the node extraction step; a weld interface estimation step of estimating the position of a flow leading end of a weld interface formed on a cross section in the resin thickness direction at the completion of molding of the molded product based on the change over time of the flow velocity vector derived in the flow velocity vector derivation step; a secondary weld estimation step of estimating a line connecting the flow front ends of the weld interface estimated in the weld interface estimation step with those corresponding to the plurality of nodes as a secondary weld; a quadratic curve approximation step of approximating the shape of the weld interface with a quadratic curve y=a×x 2 +bx+c; a molding quality prediction step of predicting molding quality of the molded product based on the coefficient a of the quadratic curve approximated in the quadratic curve approximation step; A molding quality prediction method comprising:

2. 2. The molding quality prediction method according to claim 1, wherein the flow velocity vector is the second flow velocity vector obtained by decomposing a flow velocity vector in the resin flow direction into a first flow velocity vector in the axial direction along which the primary weld extends and a second flow velocity vector in an orthogonal direction perpendicular to the axial direction.

3. The molding quality prediction method according to claim 1 , wherein the flow velocity vector is a flow velocity vector in a resin flow direction.

4. A molding quality prediction device that predicts the quality of a molded product formed by resin injection molding, a flow analysis unit that performs a flow analysis of a shell mesh based on the shape data of the molded product; a node extraction unit that extracts a plurality of nodes along a primary weld formed in a meeting region of two resin flows based on a flow analysis result by the flow analysis unit; a flow velocity vector derivation unit that divides the molded product into a plurality of virtual divided layers in a resin thickness direction, and derives a change over time in a flow velocity vector in a central layer in the resin thickness direction among the plurality of virtual divided layers for each of the extracted nodes; a weld interface estimation unit that estimates the position of a flow leading edge of a weld interface that is formed on a cross section in the resin thickness direction at the completion of molding of the molded product based on the change over time of the flow velocity vector; a secondary weld estimation unit that estimates a line connecting the flow front ends of the weld interface corresponding to the plurality of nodes as a secondary weld; a quadratic curve approximation section that approximates the shape of the weld interface with a quadratic curve of y=a×x 2 +bx+c; a molding quality prediction unit that predicts the molding quality of the molded product based on the coefficient a of the quadratic curve approximated by the quadratic curve approximation unit; A molding quality prediction device comprising:

5. 5. The molding quality prediction device according to claim 4, wherein the flow velocity vector is the second flow velocity vector obtained by decomposing a flow velocity vector in the resin flow direction into a first flow velocity vector in the axial direction in which the primary weld extends and a second flow velocity vector in an orthogonal direction perpendicular to the axial direction.

6. 5. The molding quality prediction device according to claim 4, wherein the flow velocity vector is a flow velocity vector in a resin flow direction.

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