A method for predicting mesh draft force

Abstract

The present application relates to a method for pre-judgment of a mesh demoulding force. Based on the use of an existing demoulding force calculation formula, a finite element analysis model is used to simulate and calculate the demoulding angle of each mesh (each element), and then the demoulding force of each element is calculated. The calculated demoulding angle is used to determine whether the element belongs to the upper mold or the lower mold. The demoulding forces of the elements of the upper and lower molds are added together to obtain a demoulding force obtained according to the finite element model. This method is convenient for predicting whether there is a demoulding problem in the actual demoulding process during the design process. For example, when the workpiece is demoulded, it does not move with the upper mold and remains in the lower mold. In this way, this problem can be avoided in the design stage.

Description

Technical Field

[0001] The present application belongs to the field of mold technology, and in particular relates to a method for pre-judgment of a mesh draft force. Background Art

[0002] In the field of mold manufacturing, demoulding problems are more likely to occur during the actual demoulding process, such as the demoulding problem that the workpiece does not move with the upper mold during demoulding and remains in the lower mold. This demoulding defect may be caused by inappropriate demoulding force. In the prior art, there is a lack of a better method for calculating the mesh demoulding force. Summary of the invention

[0003] The technical problem to be solved by the present invention is: to solve the above-mentioned demoulding defects in the prior art, thereby providing a method for pre-judging the mesh demoulding force.

[0004] The technical solution adopted by the present invention to solve its technical problem is:

[0005] A method for pre-judging mesh draft force comprises the following steps:

[0006] S1, the upper die and the lower die of the workpiece are divided into a number of corresponding elements by using a grid, a three-dimensional model of the workpiece is drawn according to the 3D modeling software, and a finite element analysis model is established;

[0007] S2, according to the finite element analysis model, the draft angle between each element and the draft direction is calculated by the formula, and then the draft force is calculated;

[0008] S3, separate the upper die and the lower die;

[0009] S4, accumulating the draft forces of the elements belonging to the upper die or the lower die to obtain an upper die draft force and a lower die draft force based on a finite element analysis model for actual reference;

[0010] S5, a theoretical draft force based on the finite element model is obtained.

[0011] Preferably, the method for pre-judgment of the grid draft force of the present invention further comprises the step of pre-judging the feasibility of the mold design based on the theoretical draft force.

[0012] Preferably, the mesh draft force pre-judgment method of the present invention selects a draft angle within the range of 3 to 15 degrees to calculate the draft force.

[0013] Preferably, the method for pre-judging the mesh draft force of the present invention further comprises calculating the magnitude and difference of the draft force of the upper die or the lower die for reference in the design process.

[0014] Preferably, the mesh draft force pre-judgment method of the present invention is formulated as follows:

[0015] F t =μ*F b *cosθ-F b *sinθ

[0016] =F b *(μ*cosθ-sinθ); F b =α*A

[0017] Among them, F t is the draft force; F b is the clamping force; A is the surface area of ​​the workpiece; μ is the friction coefficient; α is a fixed parameter; θ is the draft angle.

[0018] Preferably, the method for pre-judgment of the grid draft force of the present invention, in step S2, further comprises obtaining the draft angle θ and the surface area A of the workpiece.

[0019] Preferably, in the method for pre-judgment of the mesh draft force of the present invention, in step S2, each mesh in the finite element model is regarded as a plane composed of two space vectors, and a vector N1 identical to the draft direction and a normal vector N2 of the mesh in space are determined according to the actual situation in production, and the surface area S of each mesh and the draft angle θ of each mesh are obtained through mathematical calculation formulas for space vectors.

[0020] Preferably, the mesh draft force pre-judgment method of the present invention,

[0021] In step S3, the upper die and the lower die to which the grid belongs are separated according to the calculated positive and negative draft angles.

[0022] The beneficial effects of the present invention are:

[0023] A demoulding force based on the finite element model can be obtained, which is convenient for estimating whether there will be demoulding problems in the actual demoulding process during the design process, so that this problem can be avoided in the design stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The technical solution of the present application is further described below in conjunction with the accompanying drawings and embodiments.

[0025] Figure 1 is a flowchart of the steps of the method for pre-judgment of mesh draft force according to an embodiment of the present application;

[0026] Figure 2 Schematic diagram of the force balance relationship in the draft direction of an embodiment of the present application;

[0027] Figure 3 It is a schematic diagram of the relationship between each grid in the finite element model of the embodiment of the present application being converted into two space vectors. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0029] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present application. In addition, the terms "first", "second", etc. are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the invention, unless otherwise specified, "multiple" means two or more.

[0030] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0031] The technical solution of the present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0032] Example

[0033] This embodiment provides a method for pre-judging mesh draft force, such as Figure 1 As shown, the following steps are included:

[0034] S1, the upper die and the lower die of the workpiece are divided into a number of corresponding elements by using a grid, a three-dimensional model of the workpiece is drawn according to the 3D modeling software, and a finite element analysis model is established;

[0035] S2, according to the finite element analysis model, the draft angle between each element and the draft direction is calculated by the formula, and then the draft force is calculated;

[0036] Assumption: Each grid of the workpiece is subjected to draft force, clamping force (positive force) and friction force during demolding;

[0037] There will be an angle between the direction of the draft force and the casting, called the draft angle, assumed to be θ.

[0038] according to Figure 2 The force balance relationship in the draft direction shown can be obtained

[0039] F f *cosθ=F b *sinθ+F t

[0040] get

[0041] F t =F f *cosθ-F b *sinθ

[0042] F f =μ*F b F b =α*A(surface area of ​​workpiece)

[0043] Where μ - friction coefficient (constant, the value is different for each production unit)

[0044] α - parameter (constant, value varies for each production unit)

[0045] F t =μ*F b *cosθ-F b *sinθ

[0046] =F b *(μ*cosθ-sinθ).

[0047] By finding the draft angle θ and the surface area A of the workpiece, the draft force can be obtained.

[0048] Similarly, the workpiece is divided into each grid, and the draft force based on the finite element model is solved by calculating the grid.

[0049] Each grid in the finite element model is regarded as a plane composed of two space vectors. According to the actual situation in production, a vector N1 with the same draft direction and a normal vector N2 of the grid in space can be determined (such as Figure 3 shown),

[0050] Through mathematical calculation formulas about space vectors, we can obtain the area A of each mesh and the angle between each mesh and the draft direction, that is, the draft angle θ.

[0051] Substitute into the above formula

[0052] F t =μ*F b *cosθ-Fb *sinθ

[0053] =F b *(μ*cosθ-sinθ).

[0054] S3, according to the calculated draft angle, the upper die and the lower die to which the grid belongs are separated;

[0055] S4, accumulating the draft forces of the elements belonging to the upper die or the lower die to obtain an upper die draft force and a lower die draft force based on a finite element analysis model for reference by CAD engineers;

[0056] Since the requirements of each part are different, the selected effective draft angles are also very different. If too many faces exceed the effective angle, CAD engineers are required to modify the structure or faces of the part to reduce the probability of demolding problems caused by the part itself.

[0057] S5, a theoretical draft force based on the finite element model is obtained.

[0058] Preferably, the method for pre-judgment of the grid draft force of this embodiment further includes the step of pre-judgment of the feasibility of the mold design based on the theoretical draft force.

[0059] Preferably, the mesh draft force pre-judgment method of this embodiment selects a draft angle within the range of 3 to 15 degrees to calculate the draft force.

[0060] Preferably, the method for pre-judging the mesh draft force of this embodiment further includes calculating the magnitude and difference of the draft force of the upper die or the lower die for reference in the design process.

[0061] The mesh draft force pre-judgment method of this embodiment can achieve the following effects:

[0062] 1. Provide a draft force based on a finite element model during the design phase to roughly determine whether the design is feasible and whether there is room for change.

[0063] 2. When faced with complex surfaces, it can describe the complex surface angles more accurately than CAD, and improve the accuracy of the calculation of the draft force of the complex surface.

[0064] Based on the above ideal embodiments of this application, the relevant staff can make various changes and modifications without departing from the technical concept of this application through the above description. The technical scope of this application is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for pre-judging mesh draft force, characterized in that: The following steps are involved: S1, the upper die and the lower die of the workpiece are divided into a number of corresponding elements by using a grid, a three-dimensional model of the workpiece is drawn according to the 3D modeling software, and a finite element analysis model is established; S2, according to the finite element analysis model, the draft angle between each element and the draft direction is calculated by the formula, and then the draft force is calculated; Each grid in the finite element model is regarded as a plane composed of two space vectors. According to the actual situation in production, a vector N1 with the same draft direction and a normal vector N2 of the grid in space are determined. Through the mathematical calculation formula about the space vector, the surface area A of each grid and the draft angle θ of each grid are obtained. Substitute the draft force into the formula: F t =F b *(μ*cosθ-sinθ);F b =α*A Among them, F t is the draft force; F b is the clamping force; A is the surface area of ​​the workpiece; μ is the friction coefficient; α is a fixed parameter; θ is the draft angle; S3, separating the upper die and the lower die, including: separating the upper die and the lower die to which the grid belongs according to the calculated positive and negative draft angles; S4, accumulating the draft forces of the elements belonging to the upper die or the lower die to obtain an upper die draft force and a lower die draft force based on a finite element analysis model for actual reference; S5, a theoretical draft force based on the finite element model is obtained; The method also includes the following steps: based on the theoretical draft force, pre-judgment of the feasibility of the mold design is made, draft angles within the range of 3 to 15 degrees are selected to calculate the draft force, and the magnitude and difference of the draft force of the upper mold or the lower mold are calculated for reference in the design process.

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