An automatic high-pressure die-casting gate design method based on computer simulation

Abstract

The present invention proposes an automatic high-pressure die-casting gate design method based on computer simulation, comprising: obtaining a two-dimensional projection of a three-dimensional model, including: projecting the three-dimensional grid corresponding to the casting onto six planes in a Cartesian coordinate system with the positive and negative directions of the x, y, and z axes as normal vectors; gate parametric design, including: automatically defining the location for placing the gate on the three-dimensional grid corresponding to the casting; gate design optimization, including: generating a parametric gate using a discrete optimization algorithm based on die-casting simulation, including: first randomly generating a series of gate designs, and then using the above-generated gate designs for die-casting simulation calculations; generating a new design using an optimization algorithm based on the final air entrainment corresponding to different designs calculated by simulation to reduce the air entrainment; and after performing a series of iterations, selecting the design with the smallest air entrainment as the final design.

Description

Technical Field

[0001] The present invention relates to the technical field of casting technology, in particular to an automatic high-pressure die-casting gate design method based on computer simulation. Background Art

[0002] In high-pressure die casting, molten metal flows into the mold through the gate. Gate design directly affects air entrapment and defect formation during the die-casting filling process, thus determining the final quality of the casting. In traditional process design, gate design is manually performed by engineers. In practice, due to the complex geometry of the casting, the quality of gate design depends largely on the engineers' prior experience. For some new castings, multiple design iterations combined with experiments are required to reach a final solution, which increases the company's labor costs. Summary of the Invention

[0003] The object of the present invention is to solve at least one of the technical drawbacks.

[0004] To this end, the purpose of the present invention is to propose an automatic high-pressure die-casting gate design method based on computer simulation to solve the problems mentioned in the background technology and overcome the shortcomings of the existing technology.

[0005] To achieve the above objectives, an embodiment of the present invention provides an automatic high-pressure die-casting gate design method based on computer simulation, comprising the following steps:

[0006] Step S1, obtaining a two-dimensional projection of the three-dimensional model, including: projecting the three-dimensional mesh corresponding to the casting onto six planes in a Cartesian coordinate system with the positive and negative directions of the x, y, and z axes as normal vectors;

[0007] Step S2, parametric gate design, includes: automatically defining the location of the gate on the 3D mesh corresponding to the casting, wherein the gate design is performed on a 2D projection plane, and the designed gate is projected back to the 3D model and numerically simulated;

[0008] Step S3, gate design optimization, includes: generating a parameterized gate using a discrete optimization algorithm based on die-casting simulation, including: first randomly generating a series of gate designs, and then using the generated gate designs in the die-casting simulation calculation; based on the final air entrainment volume corresponding to different designs calculated by simulation, using the optimization algorithm to generate new designs to reduce the air entrainment volume; after performing a series of iterations, selecting the design with the smallest air entrainment volume as the final design.

[0009] Preferably, any of the above schemes is that, in step S1, for the positive x direction, all three-dimensional structured grid units that have no adjacent units in the negative x direction are extracted, and the coordinate value of the unit on the x-axis is assigned to the corresponding pixel on the yz plane; eventually, a two-dimensional image on the yz plane is formed, and each pixel point of the image is assigned the coordinate value of the x-axis corresponding to the pixel point.

[0010] Preferably, in step S2, a gate parameterization method based on a unit circle is adopted, including: first, a unit circle is used to fill the feasible domain on the two-dimensional projection plane; then the unit circles are sorted according to their positions on the two-dimensional projection plane; during the design process, multiple unit circles are selected as the starting positions of the gate, and several subsequent circles along the gate direction starting from the multiple starting points will be automatically selected; the selected unit circles that intersect with each other are merged into ellipses with equivalent areas and equivalent centers of gravity; the center line of the major axis of the finally generated ellipse will be selected as the gate.

[0011] Preferably, according to any of the above solutions, the gate is represented by a number of a starting unit circle.

[0012] Preferably, in any of the above solutions, in step S3,

[0013] 1) Randomly generate m gate designs S_0 = {x_1, ..., x_m}, where each design x_i is a gate generated from n randomly selected starting positions in N unit circles;

[0014] 2) Select the design x_optimal that minimizes the amount of entrained air through die-casting simulation;

[0015] 3) For t from 1 to T, execute:

[0016] 3-1) Create a sample set {(x_1, y_1), …, (x_m, y_m)}, where x∈S_(t-1), y_i=sign[α_t-f(x_i)];

[0017] 3-2) Initialize the set S_t to empty;

[0018] 3-3) Divide the design space corresponding to the sample into two categories based on the threshold α_t, where y≥0 or y<0;

[0019] 3-4) Sampling is performed in the region y≥0, and the collected samples are classified into the set S_t;

[0020] 3-5) Calculate the objective function value corresponding to the samples in the set S_t and update x_optimal

[0021] 4) Output x_optimal, where x_optimal is the optimal gate design output by the optimization process.

[0022] Preferably, any of the above solutions is selected based on the objective function value corresponding to the sample in each iteration and the air entrainment calculated by simulation.

[0023] The computer simulation-based automatic high-pressure die-casting gate design method of the embodiment of the present invention provides a new parameterized method for high-pressure die-casting gate design, and combines die-casting simulation based on a lattice Boltzmann solver and a discrete optimization algorithm to realize the automated design and optimization of the gate. The die-casting simulation solver based on the lattice Boltzmann of the present invention can accurately predict the generation of air entrainment during the filling process, thereby providing a basis for quality judgment for automated gate design. The lattice Boltzmann solution requires the original casting geometry model to be discretized into a three-dimensional hexahedral grid. The present invention can automatically define the location where the gate can be placed on the three-dimensional grid corresponding to the casting, and then generate a parameterized gate through a discrete optimization algorithm based on die-casting simulation. Compared with manual gate design, the automation of gate design is realized. It has been verified that on the test casting, compared with the gate randomly generated within the feasible domain, the gate generated by the optimization algorithm can reduce the amount of air entrainment by at least 20% according to the corresponding die-casting simulation results.

[0024] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0026] Figure 1 Flowchart of an automatic high-pressure die-casting gate design method based on computer simulation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but are not to be construed as limiting the present invention.

[0028] like Figure 1 As shown, the automatic high-pressure die-casting gate design method based on computer simulation according to an embodiment of the present invention includes the following steps:

[0029] Step S1, obtaining a two-dimensional projection of the three-dimensional model, includes: projecting the three-dimensional mesh corresponding to the casting onto six planes in a Cartesian coordinate system with the positive and negative directions of the x, y, and z axes as normal vectors.

[0030] First, the casting's 3D mesh is projected onto six Cartesian planes with normal vectors in the positive and negative directions of the x, y, and z axes. Taking the positive x direction as an example, all 3D structured mesh cells that have no adjacent cells in the negative x direction are extracted, and the x-axis coordinate value of each cell is assigned to the corresponding pixel on the yz plane. This ultimately creates a 2D image on the yz plane, with each pixel in the image assigned the corresponding x-axis coordinate value.

[0031] Step S2, parametric gate design, includes: automatically defining the location of the gate on the three-dimensional grid corresponding to the casting, wherein the gate design is performed on a two-dimensional projection plane, and the designed gate is projected back to the three-dimensional model and numerically simulated.

[0032] Specifically, the difficulty of gate design lies in the uncertainty of gate location and number. In an embodiment of the present invention, this step adopts a gate parameterization method based on a unit circle, including: first, the unit circle is used to fill the feasible domain on the two-dimensional projection plane; then the unit circles are sorted according to their positions on the two-dimensional projection plane. During the design process, several unit circles will be selected as the starting positions of the gate, and then several subsequent circles starting from these starting points along the gate direction will be automatically selected. The selected unit circles that intersect with each other will be merged into ellipses with equivalent areas and equivalent centers of gravity. The center line of the major axis of the ellipse finally generated will be selected as the gate.

[0033] It's important to note that because the feasible region for gate generation in a two-dimensional plane isn't necessarily a continuous convex space, two unit circles with adjacent numbers don't necessarily intersect. Furthermore, gates derived from the starting unit circle may intersect and merge into a single gate. Therefore, the number of starting circles doesn't necessarily equate to the number of gates. Determining the optimal number and locations of gates depends on the optimization algorithm in the subsequent step S3.

[0034] Step S3, gate design optimization, includes: generating a parameterized gate through a discrete optimization algorithm based on die-casting simulation. In an embodiment of the present invention, the gate is represented by the number of the starting unit circle. Determining the position and number of the gate is converted into a discrete optimization problem of determining the number of the gate starting unit circle. In this step, a classification-based genetic optimization algorithm is adopted. In the specific optimization process, the optimization algorithm will first randomly generate some gate designs, and then these gate designs will be used for die-casting simulation calculations. According to the final air entrainment corresponding to different designs calculated by simulation, the optimization algorithm will generate a new design to reduce the air entrainment. After a certain number of iterations, the algorithm will select the design with the smallest corresponding air entrainment as the final design.

[0035] enter:

[0036] 1) 3D mesh for die casting simulation and its projection in a specified direction (one of x+, x-, y+, y-, z+, z-);

[0037] 2) N unit circles and their numbers used to cover the feasible region;

[0038] 3) The number n of the starting unit circles;

[0039] 4) The number of samples k in each iteration;

[0040] 5) T thresholds α_1>...>α_T for the classification algorithm;

[0041] 6) The total air volume calculated by simulation is used as the objective function f(x);

[0042] optimization:

[0043] 1) Randomly generate m gate designs S_0 = {x_1, ..., x_m}, where each design x_i is a gate generated from n randomly selected starting positions in N unit circles;

[0044] 2) Select the design x_optimal that minimizes the amount of entrained air through die-casting simulation;

[0045] 3) For t from 1 to T, execute:

[0046] 3-1) Create a sample set {(x_1, y_1), …, (x_m, y_m)}, where x∈S_(t-1), y_i=sign[α_t-f(x_i)];

[0047] 3-2) Initialize the set S_t to empty;

[0048] 3-3) Divide the design space corresponding to the sample into two categories (y≥0 or y<0) based on the threshold α_t;

[0049] The classification algorithm used in step 3-3) may be a randomized coordinate reduction method, and the region y≥0 is the corresponding region of interest;

[0050] 3-4) Sampling is performed in the region y ≥ 0, and the collected samples are classified into the set S_t; since we are not interested in the region y < 0, no sampling is performed;

[0051] 3-5) Calculate the objective function value corresponding to the samples in the set S_t and update x_optimal;

[0052] 4) Output x_optimal, where x_optimal is the optimal gate design output by the optimization process.

[0053] In the embodiment of the present invention, the selection of the threshold α is determined by the objective function value corresponding to the sample in each iteration and the entrained air volume calculated by simulation.

[0054] The computer simulation-based automatic high-pressure die-casting gate design method of the embodiment of the present invention provides a new parameterized method for high-pressure die-casting gate design, and combines die-casting simulation based on a lattice Boltzmann solver and a discrete optimization algorithm to realize the automated design and optimization of the gate. The die-casting simulation solver based on the lattice Boltzmann of the present invention can accurately predict the generation of air entrainment during the filling process, thereby providing a basis for quality judgment for automated gate design. The lattice Boltzmann solution requires the original casting geometry model to be discretized into a three-dimensional hexahedral grid. The present invention can automatically define the location where the gate can be placed on the three-dimensional grid corresponding to the casting, and then generate a parameterized gate through a discrete optimization algorithm based on die-casting simulation. Compared with manual gate design, the automation of gate design is realized. It has been verified that on the test casting, compared with the gate randomly generated within the feasible domain, the gate generated by the optimization algorithm can reduce the amount of air entrainment by at least 20% according to the corresponding die-casting simulation results.

[0055] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0056] Those skilled in the art will readily understand that the present invention encompasses any combination of the components described in the Summary and Detailed Description of the Invention and the accompanying drawings. Due to space limitations and for the sake of clarity, not all of the various solutions resulting from these combinations are described. Any modifications, equivalent substitutions, and improvements within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

[0057] Although the embodiments of the present invention have been shown and described above, it should be understood that the above embodiments are illustrative and are not to be construed as limiting the present invention. Those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments without departing from the principles and intent of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An automatic high-pressure die-casting gate design method based on computer simulation, characterized in that: The steps include: Step S1, obtaining a two-dimensional projection of the three-dimensional model, including: projecting the three-dimensional mesh corresponding to the casting onto six planes in a Cartesian coordinate system with the positive and negative directions of the x, y, and z axes as normal vectors; Step S2, gate parametric design, includes: automatically defining the location of the gate on the three-dimensional grid corresponding to the casting, wherein the gate design is performed on a two-dimensional projection plane, and the designed gate is projected back onto the three-dimensional model and numerically simulated; in step S2, a gate parameterization method based on a unit circle is adopted, including: first, the unit circle is used to fill the feasible domain on the two-dimensional projection plane; then the unit circles are sorted according to their positions on the two-dimensional projection plane; during the design process, multiple unit circles are selected as the starting points of the gate, and several subsequent circles starting from the multiple starting points along the gate direction are automatically selected; the selected unit circles that intersect with each other are merged into ellipses with equivalent areas and equivalent centers of gravity; and the centerline of the major axis of the finally generated ellipse is selected as the gate; Step S3, gate design optimization, includes: generating a parameterized gate using a discrete optimization algorithm based on die-casting simulation, including: first randomly generating a series of gate designs, and then using the generated gate designs in the die-casting simulation calculation; based on the final air entrainment volume corresponding to different designs calculated by simulation, using the optimization algorithm to generate new designs to reduce the air entrainment volume; after performing a series of iterations, selecting the design with the smallest air entrainment volume as the final design.

2. The automatic high-pressure die-casting gate design method based on computer simulation according to claim 1, characterized in that: In step S1, for the positive x direction, all three-dimensional structured grid units that have no adjacent units in the negative x direction are extracted, and the coordinate value of the unit on the x-axis is assigned to the corresponding pixel on the yz plane; eventually, a two-dimensional image on the yz plane is formed, and each pixel point of the image is assigned the coordinate value of the x-axis corresponding to the pixel point.

3. The automatic high-pressure die-casting gate design method based on computer simulation according to claim 1, characterized in that: The gate is represented by the number of the starting unit circle.

4. The automatic high-pressure die-casting gate design method based on computer simulation according to claim 1, characterized in that: In step S3, 1) Randomly generate m gate designs S_0 = {x_1, ..., x_m}, where each design x_i is a gate generated from n randomly selected starting positions in N unit circles; 2) Select the design x_optimal that minimizes the amount of entrained air through die-casting simulation; 3) For t from 1 to T, execute: 3-1) Create a sample set {(x_1, y_1), …, (x_m, y_m)}, where x∈S_(t-1), y_i=sign[α_t-f(x_i)]; 3-2) Initialize the set S_t to empty; 3-3) Divide the design space corresponding to the sample into two categories based on the threshold α_t, where y≥0 or y<0; 3-4) Sampling is performed in the region y≥0, and the collected samples are classified into the set S_t; 3-5) Calculate the objective function value corresponding to the samples in the set S_t and update x_optimal 4) Output x_optimal, where x_optimal is the optimal gate design output by the optimization process.

5. The automatic high-pressure die-casting gate design method based on computer simulation according to claim 4, characterized in that: The selection of the threshold α is determined by the objective function value corresponding to the sample in each iteration and the air entrainment volume calculated by simulation.

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