JPH10278085A - Apparatus and method for predicting temperature history in injection molding process - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To divide the surface of a mold without dividing the inside of the mold into minute elements, predict the temperature history of the molded product and the mold during the molding process, and shorten the calculation time. Let it. SOLUTION: In step 1, dimensions, material properties, boundary conditions, and molding conditions of a mold, a molded product, and a cooling pipe are inputted. In the stage 2, based on the input information, each of the subsequent stages 3, 4, 6
Create requirements for use in. In step 3, the average heat flux of one cycle that escapes from the surface of the molded product to the mold is calculated. Stage 4
Then, the temperature and the heat flow rate are calculated for each element. In step 5, the worst part of the way of transmitting the heat of the temperature from the molded article to the cooling pipe is selected as a representative point, and the distance and the equivalent heat transfer coefficient are calculated so that the relation of the representative point becomes equivalent to the one-dimensional model. I do. Step 6 calculates the cyclic temperature history of the molded article and the mold, and Step 7 analyzes the equivalent one-dimensional model.
Outputs the result calculated by.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process simulation for an injection molding method, and more particularly to a method for predicting a temperature history of a molded product and a mold, and predicts a cooling cycle, a time required for the cycle to be stabilized, and the like. The present invention relates to an apparatus and a method for performing the method.

[0002]

2. Description of the Related Art As a method for predicting the temperature of a molded article and a mold using an injection molding method, the inside of the mold and the molded article is divided into minute elements, and the finite element method, the difference method, and the finite volume method are used. A simultaneous linear equation is created from the balance of heat, then the initial temperature of each part is given as the initial condition, and the temperature, ambient temperature and heat transfer coefficient, or heat flow rate is given to the surface of each part as the boundary condition. The method of unraveling the temperature distribution of molded products and molds every moment has been adopted. However, in this method, the size of the system of linear equations to be solved is large because it is divided into many elements. Therefore, there is a problem that much calculation time is required. In addition, the inside of the molded product and the mold must be divided into elements in advance, and there is a problem that efficiency is low.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to eliminate the above two drawbacks. The present invention provides a molding process by dividing the surface of the mold into elements without dividing the inside of the mold into minute elements. An object of the present invention is to provide an apparatus and method for predicting a temperature history in an injection molding process, which can predict a temperature history of a molded article and a mold in the apparatus and shorten a calculation time.

[0004]

In order to solve such a problem, for example, a temperature history predicting apparatus in an injection molding process of the present invention has the following configuration. That is, in a device that predicts the temperature history of the molded product and the mold in the injection molding process by numerical analysis, the molded product part is divided into minute elements,
By applying the finite element method, difference method, finite volume method, boundary element method, and other numerical calculation methods to solve the transient heat conduction problem, the average of one cycle that escapes from the molded product to the mold surface in the mold can be calculated. A first means for calculating the amount of heat for each element, and a mold part divided into minute elements, and each element on the mold cavity surface is formed as a boundary condition from the molded product of each element calculated by the first calculation means. The average amount of heat escaping to the mold per cycle, the coolant temperature and the heat transfer coefficient between the coolant and the mold on the surface of the cooling pipe, and the outside air temperature and the temperature between the outside air and the mold on the mold surface in contact with the outside air. Given the heat transfer coefficient, the boundary element method, finite element method, finite volume method,
A second calculating means for calculating a mold temperature and a heat flow velocity by solving a steady heat conduction problem by applying a numerical calculation method such as a difference method, and input boundary conditions and the second calculating means Based on the temperature distribution and heat flow velocity obtained in the above, the equivalent distance and equivalent heat transfer coefficient obtained by replacing the distance from the cavity surface to the cooling pipe and the heat transfer coefficient between the coolant and the cooling pipe by a one-dimensional model Using the third calculating means to calculate and the equivalent distance and the equivalent heat transfer coefficient obtained by the third calculating means, the molded product and the mold from the cavity surface to the cooling pipe are one-dimensional microelements in the thickness direction. Calculate the temperature history of the molded product and mold during the injection molding process by repeatedly solving the transient heat conduction problem by numerical calculation using the finite element method, the difference method, and the finite volume method. 4 calculation means.

[0005]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows the flow of processing in the embodiment, which will be described in detail. In FIG. 1, reference numeral 1 denotes an input unit for inputting dimensions of a pattern of a mold, a molded product, and a cooling pipe as shown in FIGS. 2 and 3, and material properties as shown in FIG. It is composed of a part for inputting data, a part for inputting boundary condition data as shown in FIG. 5, and a part for inputting molding condition data as shown in FIG. These inputs are selected from a database stored in advance, but may be input by key. That is, any input method may be used.

Reference numeral 2 denotes an automatic element creation unit, which is based on the shape pattern, shape, and the like input by the input unit 1; The requirements used in the analysis 6 in the model are created. An example is shown in FIGS.

FIG. 7 shows the element division in the plate thickness direction and the boundary conditions at both ends used in the analysis of only the molded part. FIG. 8 shows an example in which the area around the analysis site (surface) in FIG. 2 is divided into elements, and FIG. 9 shows an example in which the area around the analysis site (surface) in FIG. 3 is divided into elements. Although only two pattern examples are shown here, other shapes can be handled in the same manner if a shape pattern is prepared. Although the shape is shown in two dimensions here, in the case of a three-dimensional shape, the model of analysis 3 using only the mold becomes three-dimensional (the mold surface is divided by two-dimensional elements), and the two-dimensional model is used. It is substantially the same as the case of the dimensional shape.

The analysis 3 of only the molded part includes material property data, boundary condition data, molding condition data input by the input unit 1 and elements created by the automatic element creation unit 2 (see FIG. 7).
Calculate the temperature of the molded part from resin filling to mold release, the amount of heat escaping from the molded product surface to the mold by numerical calculation using the finite element method, and from the calculated molded product surface By calculating the time integral of the amount of heat escaping to the mold and dividing by the cycle time, the average heat flux per cycle escaping from the surface of the molded article to the mold is calculated.

The analysis 4 of only the mold includes the material property data, the boundary condition data, and the molding condition data input through the input unit 1.
The one-cycle average heat flow escaping from the surface of the molded product to the die calculated in the analysis 3 of only the molded component is added as the boundary condition of the mold surface of the molded product, and the element created by the automatic element creation unit 2 (FIG. Using FIG. 9), the temperature and the heat flow rate are calculated for each element. At this time, steady heat conduction analysis is performed using boundary elements as an analysis method.

The one-dimensional modeling unit 5 performs an analysis 4 of only the mold.
From the temperature and heat flow rate of each element calculated in the above, the worst part of the way of transmitting the heat from the molded article to the cooling pipe is selected as a representative point (see FIGS. 11 and 12).
A distance (equivalent distance) and an equivalent heat transfer coefficient such that the relation between the representative points becomes equivalent to the one-dimensional model shown in FIG. 13 are calculated (FIGS. 14 and 15).

In the case of the shape shown in FIG. 2, the representative point is the point S shown in FIG. 11, and the equivalent distance,
An equivalent heat transfer coefficient is calculated. In the case of the shape shown in FIG. 3, the representative points are S1 and S2, and the equivalent distance and the equivalent heat transfer coefficient are calculated by the equations shown in FIG.

The analysis 6 in the equivalent one-dimensional model uses the material property data, boundary condition data, and molding condition data input by the input unit 1 and cyclically performs molding of a molded product and a mold according to the procedure shown in FIG. Calculate temperature history.

First, in step S1, a cycle heat conduction analysis in the injection molding process is performed, and in the next step S2, initial conditions are set. Specifically, the mold temperature at the start of the cycle is set to the initial mold temperature, and the temperature of the molten resin to be filled to the initial temperature of the molded product is set.

Next, in step S3, a non-presentation heat conduction analysis in a state where the resin is present in the mold or the like is performed, and in step S4
Perform non-heat conduction analysis of the cormorant with the mold open. And
Proceeding to step S5, it is determined whether or not the difference between the gathering mold temperature in the previous cycle and the final mold temperature obtained in the current cycle is within a preset range. If not, the process proceeds to step S6 to update the initial condition, and the process from step S3 onward is repeated as one cycle.

In the above processing, the molded product and the mold are modeled only in half of the plate thickness of the molded product and the portion from the mold surface to the cooling pipe of the molded product. As shown in FIG. Use the one divided by.

The output unit 7 outputs a result calculated by the analysis 6 in the equivalent one-dimensional model, and displays items as shown in FIG. 18 and 19 show examples of this display.

FIG. 20 shows a shot required for stabilizing the molding temperature at the same time as determining whether or not a molded product can be taken out under the current molding conditions before molding by using the molding conditions set in the injection molding machine as an input using this method. It is a block diagram of a device which calculates and displays a number (time). In this equipment, the time from the start of injection to the start of mold release is the time when there is resin in the mold, and the time from the start of opening the mold to take out the molded product until the start of the next injection is the intermediate (mold opening) time, based on the conditions set in the injection molding machine. By performing the remaining data input (shape pattern selection & dimension input, material selection, refrigerant selection, refrigerant temperature input, outside air temperature input, etc.) required for this method, the molded product removal temperature at the time of mold release, The result of determination as to whether removal is possible is displayed, and the number of shots (time) until the temperature of the molded article at the time of removal is stabilized is displayed. The determination as to whether the molded article can be taken out at the time of mold release is made by determining whether the temperature at which the molded article is taken out at the time of mold release is equal to or lower than the judgment temperature using the heat deformation temperature, the solidification temperature, and the like obtained from the material data as the judgment values.

The present invention may be applied to a system constituted by a plurality of devices or to an apparatus constituted by a single device.

Another object of the present invention is to provide a system or an apparatus with a storage medium in which a program code of software for realizing the functions of the above-described embodiments is recorded, and to provide a computer (or CPU) of the system or the apparatus.
And MPU) read and execute the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

According to this embodiment as described above,
Since it is not necessary to divide the inside of the mold into elements, the processing of element division is easy. Since there are no variables to be solved inside the mold, the matrix is small, and therefore the calculation time is short. Also, since the element division is simple, the element can be automatically divided by patterning the shape, and there is no need to perform the element division in advance.

[0026]

As described above, according to the present invention, the temperature history of a molded product and a mold during the molding process is obtained by dividing the surface of the mold into elements without dividing the inside of the mold into minute elements. Can be predicted, and the calculation time can be reduced.

[0027]

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an outline of an operation process of an apparatus according to an embodiment.

FIG. 2 is a diagram showing an example of a shape pattern of a mold, a molded product, and a cooling pipe.

FIG. 3 is a view showing another example of a shape pattern of a mold, a molded product, and a cooling pipe.

FIG. 4 is a diagram showing a resin physical property database in the embodiment.

FIG. 5 is a diagram showing boundary condition data in the embodiment.

FIG. 6 is a diagram showing molding condition data in the embodiment.

FIG. 7 is a diagram showing an example of element division when only a molded part is analyzed in the embodiment.

FIG. 8 is a diagram showing an example of element division when analyzing only the mold part with respect to the shape example of FIG. 2;

9 is a diagram showing an example of element division when analyzing only the mold part with respect to the shape example of FIG. 3;

FIG. 10 is a diagram showing an example of element division of an equivalent one-dimensional model.

11 is a diagram showing an example of extraction of a representative point of a portion where heat conduction is poor in the shape example of FIG. 2;

12 is a diagram illustrating an example of extraction of a representative point of a portion where heat conduction is poor in the shape example of FIG. 3;

FIG. 13 is a diagram showing a one-dimensional model of a molded product and a mold (from the mold surface to the cooling pipe).

FIG. 14 is a diagram showing a calculation formula of an equivalent distance and an equivalent heat transfer coefficient.

FIG. 15 is a diagram showing a formula for calculating an equivalent distance and an equivalent heat transfer coefficient.

FIG. 16 is a flowchart showing a procedure of a cyclic analysis of the injection molding process.

FIG. 17 is a diagram showing output items in the embodiment.

FIG. 18 is a diagram showing an example of a result display (temperature changes of a molded product and a mold surface at the time of mold release until cycle stabilization).

FIG. 19 is a diagram showing an example of a result display (temperature distribution of resin and mold at the time of mold release during stable molding cycle).

FIG. 20 is a configuration diagram of a determination device that can remove a molded product at the time of mold release using the method of the present embodiment.

Claims (5)

[Claims] An apparatus for predicting the temperature history of a molded product and a mold in an injection molding process by numerical analysis, wherein a molded product part is divided into minute elements, and a finite element method, a difference method, a finite volume method, and a boundary element method are used. A first means for calculating, for each element, an average heat quantity per cycle that escapes from a molded product to a mold surface in a mold by solving a transient heat conduction problem by applying a numerical calculation method such as The mold part is divided into microelements, and as one of the boundary conditions, the amount of heat of one cycle, which is calculated by the first calculating means and escapes from the molded product of each element to the die, is calculated for each element on the mold cavity surface. On the surface, the refrigerant temperature, the heat transfer coefficient between the refrigerant and the mold,
The mold surface in contact with the outside air is given the outside air temperature and the heat transfer coefficient between the outside air and the mold, and the boundary element method, finite element method, finite volume method, finite difference method and other numerical calculation methods are applied, and the steady heat is applied. By solving the conduction problem, a second calculating means for calculating the temperature and heat flow rate of the mold, and based on the input boundary conditions and the temperature distribution and heat flow rate obtained by the second calculating means, Third calculating means for calculating an equivalent distance and an equivalent heat transfer coefficient obtained by replacing the distance from the mold surface to the cooling pipe and the heat transfer coefficient between the refrigerant and the cooling pipe by a one-dimensional model; and the third calculation Using the equivalent distance and equivalent heat transfer coefficient obtained by the means, the mold from the molded product and the mold surface to the cooling pipe is divided into one-dimensional microelements in the thickness direction, and the finite element method or difference method, finite volume method By solving the unsteady heat conduction problem repeatedly by numerical calculation using Temperature history prediction apparatus in an injection molding process, characterized in that it comprises a fourth calculation means for calculating the temperature history of the molded article and the mold during the molding process the process exits. 2. The apparatus according to claim 1, wherein the shape to be analyzed is modeled for each part using the element-divided shape registered in the shape database, and the analysis is performed for each part. A temperature history predicting apparatus in an injection molding process, comprising: means for predicting a temperature distribution of a molded article, a cycle time, and a time required for stabilizing a cycle. 3. The apparatus according to claim 2 is used to give material property data such as shape, thermal conductivity, specific heat, density, heat deformation temperature, and solidification temperature, and to obtain a mold based on molding conditions set in a molding machine. Means for calculating and displaying the temperature of the molded product at the time of taking out, using the internal cooling time and the mold opening time required to remove the molded product as input data, and determining the maximum value of the calculated temperature, heat deformation temperature, solidification temperature, etc. A temperature history predicting apparatus in an injection molding process, comprising means for comparing values and determining whether a molded product can be taken out at the time of mold release. 4. A method for predicting the temperature history of a molded product and a mold in an injection molding process by numerical analysis, wherein a molded product part is divided into minute elements, and a finite element method, a difference method, a finite volume method, and a boundary element method are used. A first calculation step of calculating, for each element, a one-cycle average amount of heat that escapes from a molded product to a mold surface in a mold by solving a transient heat conduction problem by applying a numerical calculation method such as The mold part is divided into minute elements, and as one of the boundary conditions, the average amount of heat of one cycle that escapes from the molded product of each element to the mold, which is calculated in the first calculation step, for each element on the mold cavity surface is determined by a cooling pipe. The surface of the refrigerant temperature and heat transfer coefficient between the refrigerant and the mold,
The mold surface in contact with the outside air is given the outside air temperature and the heat transfer coefficient between the outside air and the mold, and the boundary element method, finite element method, finite volume method, finite difference method and other numerical calculation methods are applied, and the steady heat is applied. By solving the conduction problem, a second calculation step of calculating the temperature and heat flow rate of the mold, and based on the input boundary conditions and the temperature distribution and heat flow rate obtained by the second calculation means, A third calculation step of calculating an equivalent distance and an equivalent heat transfer coefficient obtained by replacing the distance from the mold surface to the cooling pipe and the heat transfer coefficient between the refrigerant and the cooling pipe by a one-dimensional model; and the third calculation. Using the equivalent distance and equivalent heat transfer coefficient obtained in the process, the mold from the molded product and the mold surface to the cooling pipe is divided into one-dimensional microelements in the plate thickness direction, and the finite element method, the difference method, and the finite volume method By solving the unsteady heat conduction problem repeatedly by numerical calculation using The fourth temperature history prediction method in an injection molding process, characterized in that it comprises a calculation step of calculating the temperature history of the molded article and the mold during the molding process the process exits. 5. A storage medium storing a program code which is read and executed by a computer to function as an apparatus for predicting the temperature history of a molded product and a mold in an injection molding process by numerical analysis. By dividing the element into elements and applying a numerical calculation method such as the finite element method, the difference method, the finite volume method, and the boundary element method, the transient heat conduction problem is solved, and the molded product is transferred to the mold surface in the mold. A first means for calculating the amount of heat escaped per cycle for each element; and a mold part divided into minute elements, and each element calculated by the first calculation means for each element of the mold cavity surface as a boundary condition. The average amount of heat per cycle escaping from the molded product of the element to the mold, the temperature of the refrigerant and the heat transfer coefficient between the refrigerant and the mold on the surface of the cooling pipe,
The mold surface in contact with the outside air is given the outside air temperature and the heat transfer coefficient between the outside air and the mold, and the boundary element method, finite element method, finite volume method, finite difference method and other numerical calculation methods are applied, and the steady heat is applied. By solving the conduction problem, a second calculating means for calculating the temperature and heat flow rate of the mold, and based on the input boundary conditions and the temperature distribution and heat flow rate obtained by the second calculating means, Third calculating means for calculating an equivalent distance and an equivalent heat transfer coefficient obtained by replacing the distance from the mold surface to the cooling pipe and the heat transfer coefficient between the refrigerant and the cooling pipe by a one-dimensional model; and the third calculation Using the equivalent distance and equivalent heat transfer coefficient obtained by the means, the mold from the molded product and the mold surface to the cooling pipe is divided into one-dimensional microelements in the thickness direction, and the finite element method or difference method, finite volume method By solving the unsteady heat conduction problem repeatedly by numerical calculation using Moldings and fourth storage medium storing program codes to function as a calculation means for calculating the temperature history of a mold during the molding process the process exits.