COMPUTER-IMPLEMENTED METHOD FOR SIMULATING A FILLING PROCESS OF A MOLD CAVITY

Abstract

Described herein is a computer-implemented method for simulating a filling process of a mold cavity in an injection molding process using a plastic material, the method including: i) discretizing at least a part of the mold cavity into a plurality of cells; ii) defining a cavity injection point; iii) determining a surface normal direction perpendicular to the nearest cavity sur-face for each cell; iv) determining a cell coordinate system for each cell, defined by a first principal direction parallel to a flow direction, a third principal direction parallel to the normal direction, and a second principal direction perpendicular to the first and third principal directions; and v) determining the flow direction of a mold flow for each cell.

Claims

1. A computer-implemented method for simulating a filling process of a mold cavity in an injection molding process using a plastic material, the method comprising: i) discretizing at least a part of the mold cavity into a plurality of cells; ii) defining a cavity injection point; iii) determining a surface normal direction perpendicular to the nearest cavity surface for each cell; iv) determining a cell coordinate system for each cell, defined by a first principal direction parallel to a flow direction, a third principal direction parallel to the normal direction, and a second principal direction perpendicular to the first and third principal directions; and v) determining the flow direction of a mold flow for each cell.

2. The method according to claim 1, wherein, if the plastic material is a fiber-reinforced plastic material, the method further comprises: vi) determining fiber orientation of the fiber-reinforced plastic material.

3. The method according to claim 2, wherein step vi) comprises: vi.1) providing a database, the database containing information on fiber orientation for the fiber-reinforced plastic material for at least one dummy element.

4. The method according to claim 3, wherein the information contained in the database comprises one or both of simulated data or empirically retrieved data on fiber orientation.

5. The method according to claim 3, wherein step vi) further comprises: vi.2) retrieving information on fiber orientation for each cell from the database by using a cell position of the cell and determining fiber orientation for the cell in the cell coordinate system.

6. The method according to claim 5, wherein step vi.2) is performed by using similarity considerations between the mold cavity and the dummy element.

7. The method according to claim 6, wherein the similarity considerations are based on the assumption that, by using similar definitions of coordinate systems for the cell of the mold cavity and for the dummy element, the fiber orientation in the mold cavity is identical to the fiber orientation in the dummy element for identical relative positions within the mold cavity and the dummy element respectively.

8. The method according to claim 1, wherein the method further comprises determining neighboring cells for each individual cell of the plurality of cells.

9. The method according to claim 8, wherein the method further comprises determining a cell-filling sequence using information on the neighboring cells.

10. The method according to claim 9, wherein the method comprises a recursive determination of an inflow of a molten mass of the plastic material from neighboring cells for each individual cell.

11. The method according to claim 10, wherein the method comprises recursively solving a continuity equation for each individual cell by considering inflow from neighboring cells and outflow into neighboring cells.

12. The method according to claim 3, wherein the database contains information on fiber orientation for a plurality of fiber-reinforced plastic materials.

13. The method according to claim 1, wherein the method further comprises determining a wall thickness information for each of the cells of the plurality of cells.

14. The method according to claim 1, wherein performing at least steps i) to v) of the method takes a processing time T, wherein 0 s<T≤300 s.

15. The method according to claim 1, wherein the method further comprises: vii) outputting at least one visualization, wherein the visualization is output via at least one interface or port.

16. A method for verifying a design of an object, the method comprising: I. providing CAD data of the object; II. transforming the CAD data of the object into CAD data of a corresponding mold cavity for injection molding the object; III. choosing at least one plastic material and at least one injection point; IV. simulating a filling process of the mold cavity by using the method according to any one of the preceding claims; and V. evaluating a simulation result provided by step IV.

17. The method according to claim 16, wherein the simulation result evaluated in step V. is at least one visualization output via at least one interface or port.

18. A computer system comprising at least one processor configured to perform the computer implemented method for simulating a filling process according to claim 1.

19. A computer program comprising instructions which, when the program is executed by a computer or computer system, cause the computer or computer system to carry out the method according to claim 1.

20. (canceled)

Description

SHORT DESCRIPTION OF THE FIGURES

[0195] Further optional features and embodiments will be disclosed in more detail in the subsequent description of embodiments, preferably in conjunction with the dependent claims. Therein, the respective optional features may be realized in an isolated fashion as well as in any arbitrary feasible combination, as the skilled person will realize. The scope of the invention is not restricted by the preferred embodiments. The embodiments are schematically depicted in the Figures. Therein, identical reference numbers in these Figures refer to identical or functionally comparable elements.

[0196] In the Figures:

[0197] FIG. 1 shows an embodiment of CAD data of an object and a corresponding embodiment of a mold cavity for injection molding the object in a perspective view;

[0198] FIG. 2 shows a section view of part of the embodiment of CAD data of the object and the corresponding embodiment of the mold cavity as illustrated in FIG. 1;

[0199] FIGS. 3 and 4 show different embodiments of mold cavities in a perspective view;

[0200] FIG. 5 shows an embodiment of a database in a perspective view;

[0201] FIG. 6 shows an embodiment of a computer system in a perspective view;

[0202] FIGS. 7A and 7B show flow charts of different embodiments of a simulation method;

[0203] FIG. 8 shows a flow chart of an embodiment of a verification method;

[0204] FIG. 9 shows a section view of an embodiment of a mold cavity in an injection molding process using a plastic material;

[0205] FIG. 10 shows a part of an embodiment of a discretized mold cavity in an injection molding process using a plastic material in a top plane view; and

[0206] FIG. 11 shows a filling process of an embodiment of a mold cavity in an injection molding process using a plastic material in a perspective view.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0207] In FIG. 1 an embodiment of CAD data of an object 110 and a corresponding embodiment of a mold cavity 112 for injection molding the object is illustrated in a perspective view. For illustrational purposes a die 113 having a void in the shape of the mold cavity 112 is partly illustrated. A cavity injection point 114 may be defined on the mold cavity 112. FIG. 2 shows a section view of part of the mold cavity 112 as illustrated in FIG. 1. The mold cavity 112 may be discretized into a plurality of cells 116. Each cell 116 may comprise a cell coordinate system. The cell coordinate system may be defined by a first principal direction 118 parallel to a flow direction 120, as exemplarily illustrated in FIG. 1. Further, the cell coordinate system may be defined by a third principal direction 122 parallel to a surface normal direction 124, as exemplarily illustrated in FIG. 2, wherein the surface normal direction 124 may be oriented in a perpendicular fashion to the nearest cavity surface 125. Lastly, the cell coordinate system may be defined by a second principal direction 126 perpendicular to the first principal direction 118 and the third principal direction 122.

[0208] In the FIGS. 3 and 4 different embodiments of mold cavities 112 are illustrated with cavity injection points 114. In particular, each mold cavity 112 may be discretized into a plurality of cells 116.

[0209] In FIG. 5 an embodiment of a database 128 is illustrated. The database 128 comprises information on a fiber orientation for a fiber-reinforced plastic material for at least one dummy element 130. Specifically, as illustrated in FIG. 5, the database 128 may comprise information on the fiber orientation for the fiber-reinforced plastic material for more than one, for example three dummy elements 130. In particular, the information contained in the database 128 may comprise one or both of simulated data or empirically retrieved data on fiber orientation, specifically for a fiber-reinforced plastic material for the dummy elements 130.

[0210] FIG. 6 illustrates an embodiment of a computer system 132 and a perspective view. The computer system 132 comprises at least one processor 134 configured for performing a computer-implemented method for simulating a filling process, e.g. a simulation method 136. Flow charts of different embodiments of the computer-implemented method 136 for simulating a filling process, in particular of the simulation method 136, are illustrated in FIGS. 7A and 7B. The computer system 132 may comprise a data storage 138, for example for storing the database 128. Further, the computer system 132 may comprise at least one interface 140. The interface 140 may be configured for receiving information relating to a shape of the mold cavity 112. Additionally or alternatively, the interface 140 may be configured for outputting information related to a simulation result, such as a visualization 142.

[0211] The computer-implemented method 136 for simulating a filling process of a mold cavity 112 in an injection molding process using a plastic material, specifically the simulation method 136, comprises the following steps, which may specifically be performed in the given order. Still, a different order may also be possible. It may be possible to perform two or more of the method steps fully or partially simultaneously. It may further be possible to perform one, more than one or even all of the method steps once or repeatedly. The method may comprise additional method steps which are not listed herein. The method steps of the simulation method 136 are the following: [0212] step i) (denoted with reference number 144) discretizing at least a part of the mold cavity 112 into a plurality of cells 116; [0213] step ii) (denoted with reference number 146) defining a cavity injection point 114; [0214] step iii) (denoted with reference number 148) determining a surface normal direction 124 perpendicular to the nearest cavity surface 125 for each cell 116; [0215] step iv) (denoted with reference number 150) determining a cell coordinate system for each cell 116, defined by [0216] a first principal direction 118 parallel to a flow direction 120, [0217] a third principal direction 122 parallel to the normal direction 124, and [0218] a second principal direction 126 perpendicular to the first 118 and third 122 principal directions; and [0219] step v) (denoted with reference number 152) determining the flow direction 120 of a mold flow for each cell 116.

[0220] Further, the simulation method 136, in case the plastic material is a fiber-reinforced plastic material, may comprise step vi) (denoted with reference number 154) comprising determining fiber orientation of the fiber-reinforced plastic material.

[0221] As illustrated in FIG. 7B, an embodiment of the simulation method 136 may additionally comprise a branching point 156. The branching point 156 may indicate a condition query, such as deciding between a first branch 158 and a second branch 160. For example, the condition query may make use of information on the plastic material, such as information on whether the plastic material is a fiber-reinforced plastic material or not. The first branch 158 may indicate the plastic material to be or to comprise a fiber-reinforced plastic material, thus the first branch may lead to step vi) 154. The second branch 160 may indicate the plastic material not to comprise a fiber-reinforced plastic material.

[0222] Step vi) 154 may specifically comprise substep vi.1) (denoted with reference number 162) providing a database 128, the database 128 containing information on fiber orientation for the fiber-reinforced plastic material for at least one dummy element 130. Step vi) 154 may further comprise substep vi.2) (denoted with reference number 164) retrieving information on fiber orientation for each cell 116 from the database 128 by using a cell position of the cell 116 and determining fiber orientation for the cell 116 in the cell coordinate system.

[0223] In particular, substep vi1) 164 may be performed by using similarity considerations between the mold cavity 112 and the dummy element 130. Specifically, substep vi.2) 164 may be performed by using similarity considerations between a shape of the mold cavity 112 and a shape of the dummy element 130.

[0224] The simulation method 136, may further comprise step step vii) (denoted with reference number 166) outputting at least one visualization 142, wherein the visualization 142 may be selected from the group consisting of: a fiber orientation, specifically a direction of fiber orientation; a degree of fiber orientation, specifically a degree of fiber orientation in at least one principal direction; a filling state, specifically a filling state after a predetermined amount of time; a pressure state, specifically a pressure state after a predetermined amount of time; a shear rate distribution, specifically a shear rate distribution state after a predetermined amount of time; a mass accumulations state; a flow path length state; a shrinkage state.

[0225] In particular, step vii) 166 may be performed after performing step vi). Alternatively, in case the plastic material does not comprise a fiber-reinforced plastic material, step vi) 154 of the simulation method 136 may be skipped. Thus, as an example, step vii) 166 may be performed directly after performing step v) 152, as illustrated in FIG. 7B by the second branch 160 directly leading to step vii) 166 of the simulation method 136.

[0226] Specifically, performing the simulation method 136 may take a processing time T, e.g. a run time. As an example, in table 1 a run time comparison for performing a filling simulation of three different mold cavities 112 may be illustrated. In particular, the run time T.sub.state_of_the_art necessary for performing the filling simulation by using an injection molding process simulation method as known to the skilled person, such as by using FEM simulations, may be compared to the run time T.sub.sim necessary for performing the simulation method 136 as proposed herein. Specifically, the run time comparison illustrated in table 1 may show the run times T.sub.state_of_the_art in the second column and T.sub.sim in the third column of the table 1. The run times may be compared for three different mold cavities 112, in particular for the three different embodiments of the mold cavity 112 as illustrated in FIG. 1, FIG. 3 and FIG. 4. The mesh size being used for performing the filling simulations may be 2.0 mm for all three mold cavities 112. In the fourth column of the table 1 a performance gain may be listed, wherein the performance gain may indicate the absolute number of times the simulation method 136 may be performed within the run time T.sub.State_of_the_art necessary for once performing the filling simulation by using an injection molding process simulation method as known to the skilled person.

TABLE-US-00001 TABLE 1 Comparison of run times of FEM simulations (T.sub.State.sub.—.sub.of.sub.—.sub.the.sub.—.sub.art) vs. simulations according to the present invention (T.sub.sim), for various objects. performance mold cavity T.sub.State.sub.—.sub.of.sub.—.sub.the.sub.—.sub.art T.sub.sim gain “P11 Plaque”  78 min 15 s 312 x (illustrated in FIG. 1) “Eiffel tower test part” 160 min 27 s 355 x (illustrated in FIG. 3) “ECU Housing” 130 min 20 s 390 x (illustrated in FIG. 4)

[0227] In FIG. 8 a flow chart of an embodiment of a method for verifying a design of an object 110, specifically of a verification method 168, is shown. The verification method 168 comprises the following steps, which may specifically be performed in the given order. Still, a different order may also be possible. It may be possible to perform two or more of the method steps fully or partially simultaneously. It may further be possible to perform one, more than one or even all of the method steps once or repeatedly. The method may comprise additional method steps which are not listed herein. The method steps of the verification method 168 are the following: [0228] step I. (denoted with reference number 170) providing CAD data of the object 110; [0229] step II. (denoted with reference number 172) transforming the CAD data of the object 110 into CAD data of a corresponding mold cavity 112 for injection molding the object 110; [0230] step III. (denoted with reference number 174) choosing at least one plastic material and at least one injection point 114; [0231] step IV. (denoted with reference number 176) simulating a filling process of the mold cavity 112 by using the simulation method 136; and [0232] step V. (denoted with reference number 178) evaluating a simulation result provided by step IV 176.

[0233] In particular, the simulation result evaluated in step V. may be at least one visualization 142 output via at least one interface 140, as for example illustrated in FIG. 6.

[0234] In FIG. 9 a section view of an embodiment of a mold cavity 112 in an injection molding process using a plastic material is illustrated. In particular, FIG. 9 may show a visual derivation of formula (1), e.g. of a physical equation, as described above, specifying a link between a velocity v of a flow front 180 of a molten mass of the plastic material and a thickness h, a viscosity η of the molten mass of the plastic material, a filling pressure p.sub.1, an ambient pressure p.sub.0 and a distance I from the flow front 180 to a cavity injection point 114.

[0235] In FIG. 10 a part of an embodiment of a discretized mold cavity 112 in an injection molding process using a plastic material is illustrated. In particular, FIG. 10 may show a topological approach of the filling process, specifically of a molten mass of the plastic material filling the mold cavity 112 starting at a cavity injection point 114 and spreading from one cell 116, specifically from a starting cell 182, to its neighboring cells 184 as indicated by arrows within FIG. 9.

[0236] In FIG. 11 a filling process of an embodiment of a mold cavity 112 in an injection molding process using a plastic material is illustrated in a perspective view. In particular, four fill stages of the mold cavity 112 in the injection molding process are shown, wherein the fill stages advance from left to right, as indicated by an x-axis at the bottom of FIG. 11 indicating an advance of time t. In particular, a flow front 180 may advance within the mold cavity 112 according to a mix of a topological approach and a physical approach.

LIST OF REFERENCE NUMBERS

[0237] 110 object [0238] 112 mold cavity [0239] 113 die [0240] 114 cavity injection point [0241] 116 cell [0242] 118 first principal direction [0243] 120 flow direction [0244] 122 third principal direction [0245] 124 normal direction [0246] 125 cavity surface [0247] 126 second principal direction [0248] 128 database [0249] 130 dummy element [0250] 132 computer system [0251] 134 processor [0252] 136 simulation method [0253] 138 data storage [0254] 140 interface [0255] 142 visualization [0256] 144 step i) [0257] 146 step ii) [0258] 148 step iii) [0259] 150 step iv) [0260] 152 step v) [0261] 154 step vi) [0262] 156 branching point [0263] 158 first branch [0264] 160 second branch [0265] 162 step vi.1) [0266] 164 step vi.2) [0267] 166 step vii) [0268] 168 verification method [0269] 170 step I. [0270] 172 step II. [0271] 174 step III. [0272] 176 step IV. [0273] 178 step V. [0274] 180 flow front [0275] 182 starting cell [0276] 184 neighboring cell

REFERENCES

[0277] EP 2 612 266 B1