JP3023969B2 - Method for analyzing temperature of cooling / heating cycle structure and design apparatus for mold apparatus system - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for analyzing the temperature of a cooling / heating cycle structure and a designing apparatus for a mold apparatus system, and more particularly, to a cooling apparatus such as an injection molding mold. For a mold used under repeated cycles, the shape of the mold, the type of metal material used for the mold, the piping condition of the mold cooling pipe, the flow rate of the coolant, and the shape of the molded product are specified. The present invention relates to an analysis method and a design apparatus for optimally designing the configuration and operating conditions of the entire mold apparatus system, such as the mold cavity shapes to be performed, and the operating conditions of these molds and their cooling systems.

[Conventional technology]

In general, if the configuration and operating conditions of a cooling / heating cycle structure such as a mold apparatus system are not optimally designed, the molding efficiency is deteriorated, and the molded product is often defective. It is often difficult to predict such problems at the desk design stage, and it is also possible to try and improve the mold equipment system by trial and error. It is not advantageous in terms of efficiency.

From such a point, a method of obtaining an optimum design by using analysis by computer simulation has recently been used (JP-A-63-46511, JP-A-63-16563).
970, etc.). In these conventional techniques, a so-called stationary analysis method or an unsteady analysis method is used as an analysis method, and a difference method,
The finite element method or the boundary element method is used.

[Problems to be solved by the invention]

By the way, when designing a mold such as an injection mold used under repeated cyclic cooling / heating processes to optimize it in consideration of its thermal condition, the heat flux (unit time) In order to analyze the thermal cycle in which the amount of heat (cal) entering and exiting through a unit area (cm ² ) in (sec) and the mold temperature change every moment, an unsteady analysis method is required, and the calculation method is as follows. The boundary element method is extremely advantageous in that the three-dimensional analysis model can be easily created.

Nevertheless, a technique for performing an unsteady analysis using the boundary element method for the purpose of design as described above has not been put to practical use. The reason is that, in order to analyze the mold temperature, in addition to various conditions given as constants, it is necessary to know the heat flux that changes according to the set time by an integration operation over time. For example, at a certain set time n + 1 In order to know the mold temperature, (n + 1) for all the time points from the set times 0 to n
The point is that the integration operation must be performed twice. Therefore, when trying to analyze the cooling / heating cycle of the mold over a certain number of cycles or more, the above set time n
Is large, the required calculation amount is enormous, the calculation time is extremely long with a normal capacity computer, and the design process is significantly delayed.On the other hand, a large capacity computer is difficult to use in terms of cost. For that reason, practical application was hampered.

(Description of the present invention)

(Objects of the Invention) In view of the above problems, the present invention has maintained the advantage of performing an unsteady analysis by the boundary element method in designing a thermal cycle structure such as a mold apparatus system using computer simulation. It is an object of the present invention to provide a mold apparatus system design method and a design apparatus that are practical in terms of shortening the design process and reducing costs as they are.

(Structure of the first invention and the second invention) In the first invention, as shown in the flowchart of FIG. 1, the transient temperature analysis of the thermal cycle structure is performed by the boundary element method using the CAE / CAD / CAM system. This is a method of analyzing the temperature of the cooling / heating cycle structure to be performed. The configuration of the present invention includes:
(A) calculating a time change of a heat flux in a cooling cycle based on a three-dimensional analysis model of the cooling cycle structure;
(B) calculating the average value of the heat flux during a specific time of the cooling / heating cycle, (c) calculating the integral of the next cooling / heating cycle using the average value, and (d) determining the temperature change of the cooling / heating cycle structure. Each process is provided.

As shown in the block diagram of FIG. 2, the configuration of the second invention comprises a data input unit 1 for inputting data, and a mold and a cooling device for the die based on the shape data input by the data input unit. Modeling means 2 for creating a three-dimensional analysis model; and condition data input by the data input means 1 are added to the three-dimensional analysis model, and a cyclic temperature change of the mold is performed by the boundary element method according to the elapse of a set time. Calculating means 3 for sequentially performing an integration operation; and average heat flux calculating means for calculating an average value of heat fluxes at all times until the set time corresponding to the end of each cooling / heating cycle when the integration operation in said calculating means 3 is completed. 4 and the average value of the heat flux calculated by the average heat flux calculating means 4 are added to the calculating means 3 so as to perform the integration in the next cooling / heating cycle. Calculation step shortening means 5 for using the result of the integration calculation over all the times as a heat flux value substituted in one step, and required cooling heat by the calculation means 3, average heat flux calculation means 4, and calculation step shortening means 5. This is a design apparatus for a die apparatus system having output means 6 for outputting a result of an operation over the number of cycles so as to be compared with the shape data or output data.

(Operations and Effects of the First and Second Inventions) Next, the operations and effects of the first and second inventions will be described based on the flowchart of FIG. 1 and the block diagram of FIG.

First, shape data defining the shape and structure of a cooling / heating cycle structure, for example, a mold and its cooling device, is input to the computer by the data input means 1. Examples of such shape data include data on the shape of the molding surface and the outer surface of the mold, the inner and outer diameters of the cooling pipe, and the piping path.

Next, the modeling means 2 creates a three-dimensional analysis model of the mold and its cooling device based on the shape data. This three-dimensional analysis model is called a boundary model, a surface model, etc. peculiar to the boundary element method.
Compared to the model created by the difference method or the finite element method,
Its creation is remarkably easy.

On the other hand, condition data defining the cooling / heating cycle of the mold is also input to the computer by the data input means 1. Such condition data includes the thermal conductivity and specific heat of the mold constituent material,
The injection temperature and specific heat of the molding material, the cooling time of the mold, the flow rate of the cooling liquid, and the like can be given.

Thus, the condition data input to the computer is added to the three-dimensional analysis model, and the calculation means 3 performs an integration operation. In this integration operation, the condition data given as the initial condition is applied to a predetermined heat conduction equation according to the boundary element method, and the change of the heat flux with the elapse of the set time and the change of the mold temperature based on the change over time. It is to be calculated.

However, the above calculation is performed only in the first cooling / heating cycle. That is, when the set time corresponding to the end of the first cooling / heating cycle is reached, the average heat flux calculating means 4
Calculates the average value of the heat flux at all times up to that time (hereinafter referred to as “average heat flux”), and then adds this average heat flux to the calculation means 3 by the calculation step shortening means 5.

This average heat flux substitutes in one step for the value of the heat flux as a result of the integration operation over the entire time of the first cooling and heating cycle, which is to be the basis of the integration operation in the second cooling and heating cycle. is there. Thus, for example, as shown in FIG.
If there are n set times in the first cooling and heating cycle, the required amount of calculation at the set time n + 1 in the second cooling and heating cycle is normally over all of the set times 0 to n (n
Where +1) cumulative integration operations are required, only one integration operation using the average heat flux is required. In addition, the average heat flux is given as the average value of the heat flux at all times up to that time, and thus sufficiently approximates the actual heat flux value.

Since the above-described calculation step shortening process by the average heat flux calculation means 4 and the calculation step shortening means 5 is performed at the end of each cooling / heating cycle, the time-dependent integration calculation particularly over many cooling / heating cycles is performed. When performing the analysis, the effect of shortening the calculation step and thus the effect of shortening the calculation time are extremely great while maintaining the reliability of the analysis result.

In this way, the calculation over the required number of cooling cycles is performed by the calculation means 3, the average heat flux calculation means 4, and the calculation step shortening means 5, and the temperature change of the mold is calculated. This calculation result is output as numerical data, graphic data, and the like by the output means 6, but since the non-stationary analysis is performed,
It is possible to output various data such as data indicating a temporal change in temperature at an arbitrary portion of the mold and data indicating a temperature distribution of the entire mold at an arbitrary set time. Therefore, the cooling / heating cycle of the mold can be analyzed in many aspects and effectively.

Then, based on these output data, the initially input shape data and condition data are evaluated and corrected, and the optimal design of the mold apparatus system is performed.

In view of the above, according to the first and second aspects of the present invention, in designing a mold apparatus system using computer simulation, the normal capacity is maintained while maintaining the advantage of performing the unsteady analysis by the boundary element method. The computer can sufficiently reduce the design process.

(Description of Other Inventions of First and Second Inventions) The "cooling / heating cycle structure" of the first invention refers to a fixed structure with cyclic cooling / heating changes, and an injection molding die is an example. However, the present invention is not limited to this.

In the first and second aspects of the invention, the type of data input means is not limited, and data can be input by any means such as an input keyboard, a flat figure reading device, and a three-dimensional figure recognition device.

The condition data may be input to the computer after the creation of the three-dimensional analysis model by the modeling means 2, or may be input to the computer before the creation of the three-dimensional analysis model (for example, simultaneously with or before the input of the shape data). Until it is added to the three-dimensional analysis model, it may be stored in a computer in a readable state.

The integration operation by the operation means 3 is performed according to an appropriate equation governing the unsteady heat conduction phenomenon. Examples of such equations include, but are not limited to, those described in the embodiments described below, but are not limited thereto, and are used for performing a temporal integration calculation of a cyclic temperature change as the set time elapses. Any suitable equation of can be used.

The calculation result output from the output means 6 is stored in a computer in advance, in addition to a method of simply evaluating the calculation result and correcting shape data and condition data, and a desirable standard such as a temperature change and a temperature distribution of a mold. The calculation result may be evaluated in comparison with a standard by an evaluation means provided in the computer, and the initial shape data and condition data may be automatically corrected from the result.
Further, the three-dimensional analysis model and the condition data added to the three-dimensional analysis model may be automatically reconfigured based on the shape data and the condition data thus corrected, and the integration operation may be performed again. . In this case, each time the above process is repeated, the evaluation means determines whether or not the optimum design has been reached in comparison with the standard. It is also possible to fully automate the process leading to the optimal design of the mold apparatus system. In this case, the merit of shortening the process is particularly great.

〔Example〕

Next, an embodiment of the first invention and the second invention of the present application will be described. The present embodiment is directed to an injection molding die for a box-shaped molded product including a fixed die 7 and a movable die 8 as shown in FIG.
Cooling pipes 9, indicated by alternate long and short dash lines, inside the two molds 7, 8, respectively.
This is performed to determine the optimum coolant flow rate of each cooling pipe 9 and 10 when 10 is arranged.

Then, the design device of the present embodiment, as shown in FIG.
Main computer 11, graphic computer 12,
It comprises a model display device 13 and an output display device 14.

The main computer 11 includes the data input means 1, the arithmetic means 3, the average heat flux calculating means 4, and the arithmetic step shortening means 5 shown in FIG. 2, and the graphic computer 12 includes the modeling means 2 The three-dimensional analysis model can be displayed on the model display device 13, and the output display device 14 corresponds to the output means 6.

The specific contents of this embodiment will be described with reference to FIG. 6. First, the following condition data (1) to (5) are input to the condition data input circuit 15 of the data input means 1.

Molding conditions (Cooling time, Molding time, Resin temperature, Atmospheric temperature, Coolant temperature / flow rate) Resin thermal characteristics data (Heat conductivity, Density, Specific heat, Solidification temperature, Flow stop temperature, Latent heat) Die thermal characteristics data (Heat (Conductivity, density, specific heat) Coolant heat / flow characteristic data (thermal conductivity, density, specific heat, viscosity) These condition data are stored in the condition data memory 16.

Next, data of the three-dimensional shape of the fixed mold 7, the movable mold 8, and their cooling pipes 9 and 10 is input to the shape data input circuit 17 of the data input means 1, and these data are stored in the shape data memory 18. Will be saved.

Next, by reading the shape data stored in the shape data memory 18, the model creation circuit 19 of the modeling means 2 is read.
Creates a three-dimensional analysis model as shown in FIG. 7 and displays it on the model display device 13, and inputs this three-dimensional analysis model to the integration operation circuit 21 by the model input circuit 20 of the operation means 3.

On the other hand, the condition data stored in the condition data memory 16 is also read by the condition data adding circuit 22 and added to the integral operation circuit 21.

Here, when the integration operation circuit 21 performs an operation from the three-dimensional analysis model and the condition data added thereto as an initial condition, the following heat conduction equation is used.

In the equation (1), T is temperature, t is time, ρ is density, Cp
Is specific heat, λ is thermal conductivity, and ▽ ² is Laplacian.

By giving an appropriate initial condition and boundary condition to the above equation (1) and using a time-dependent basic solution to obtain an integral equation at time n and displaying it in a matrix, the following equation (2) is obtained.

(2) In the formula, S is the set time, H is the temperature matrix, G is the heat flux matrix, Q is heat flux, 〒 ₀ is the initial temperature, B is the initial temperature matrix.

Based on the change of the heat flux according to the above equation (2), the integration operation circuit 21 performs an operation to obtain a cyclic change of the mold temperature with the lapse of the set time.

By the way, according to the equation (2), it is necessary to accumulatively perform the integral operation to obtain the mold temperature at each set time. Therefore, especially when the value of the set time becomes larger than a certain value, the integral operation is performed. Requires a large amount of calculation. Therefore, the following calculation step shortening process is performed.

That is, when the corresponding set time is reached at the end of the first cooling / heating cycle, the set time determination circuit of the average heat flux calculating means 4
23 detects this and activates the average heat flux calculation circuit 24. Then, the average heat flux calculation circuit 24 calculates the average heat flux, that is, the average value of the heat fluxes at all times up to that time, and passes the average heat flux value through the average heat flux addition circuit 25 of the calculation step shortening means 5. Is added to the integration operation circuit 21. Further, the initial value changing circuit 26 is operated, and the integration calculating circuit is operated.
In the integral operation of the second cooling / heating cycle in 21, the integral operation from the set time 0 based on the original initial condition is replaced with a one-step operation using the average heat flux.

Thereafter, such an operation step shortening process is performed at the end of each cooling / heating cycle.

The progress of the integration calculation with the progress of the set time is always checked by the calculation end determination circuit 27, and when the set time set as the end time of the analysis is reached, the integration calculation is stopped and the output means 6 The analysis data in a desired data format is output to the data output device 29 via the data output circuit 28.

FIG. 8 shows an analysis result of a change in the mold temperature over time of the fixed mold 7 and the movable mold 8 in the present embodiment. The dotted line is a calculated value, and the solid line is an experiment in which a thermocouple was attached to a mold prototype and measured. Indicates a value. As shown in the figure, the calculated values show a good correspondence with the actually measured values. From the results shown in FIG. 8, it has been found that the movable mold 8 is always in a higher temperature range than the fixed mold 7, and it is necessary to enhance the cooling of the movable mold 8. The design of the operating conditions was modified to increase the coolant flow rate.

FIGS. 9 (a) and 9 (b) are analysis results showing the distribution of the surface temperature of the movable mold 8 in the fifth and eighteenth cooling / heating cycles by isothermal lines, respectively. According to these figures, it is recognized that the surface temperature of the movable die 8 is particularly high at the upper protruding corner 30, and the piping design of the cooling pipe 10 is modified so that the corner 30 can be effectively cooled. did.

Note that the calculation time required for the analysis up to the eighteenth cooling / heating cycle in the present example was about 1/30 as compared with the case where the same analysis was performed without the calculation step shortening process.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining the first invention of the present application, and FIG.
FIG. 3 is a block diagram showing a claim corresponding to the second invention of the present application, FIG. 3 is a diagram for explaining a calculation step shortening process, FIG. 4 is a perspective view showing a mold to be analyzed in the embodiment and its cooling system, FIG. FIG. 6 is a system configuration diagram of the second invention of the present application, FIG. 6 is a block diagram of the embodiment, FIG. 7 is a diagram showing a three-dimensional analysis model created in the embodiment, and FIG. FIGS. 9 (a) and 9 (b) are diagrams showing analysis data of the surface temperature distribution of the movable mold in the fifth and eighteenth cooling / heating cycles, respectively. DESCRIPTION OF SYMBOLS 1 ... Data input means 2 ... Modeling means 3 ... Calculation means 4 ... Average heat flux calculation means 5 ... Calculation step shortening means 6 ... Output means 7 ... Fixed type 8 ... Movable type 9 ... Cooling Pipe 10 …… Cooling pipe

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-229464 (JP, A) JP-A-3-285737 (JP, A) Applied mechanical engineering vol. 28. No. 9, p120-127, Kenichi Takahari, "Plastic injection molding simulation" (58) Fields investigated (Int. Cl. ⁷ , DB name) G06F 17/50 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. A method for analyzing the temperature of a thermal cycle structure using a boundary element method to perform an unsteady temperature analysis of the thermal cycle structure using a CAE / CAD / CAM system, comprising a three-dimensional analysis model of the thermal cycle structure. Calculate the time change of the heat flux in the cooling cycle based on the above, calculate the average value of the heat flux during a specific time of the cooling cycle, calculate the integral with respect to the next cooling cycle using the average value, A method for analyzing a temperature of a thermal cycle structure, comprising: determining a temperature change of the thermal cycle structure. 2. Data input means for inputting data; modeling means for creating a three-dimensional analysis model of a mold and a cooling device thereof based on shape data input by the data input means; Calculating means for adding the condition data input by the above to the three-dimensional analysis model, and sequentially calculating the cyclic temperature change of the mold by the boundary element method as the set time elapses; Mean heat flux calculating means for calculating the average value of the heat flux at all times up to the set time at the end of each cooling / heating cycle, and the average value of the heat flux calculated by the mean heat flux calculating means Is added to the calculation means, and in the integration calculation in the next cooling / heating cycle, the result of the integration calculation over all time until then is substituted in one step. Calculating step shortening means to be used as a heat flux value; and outputting the result of the calculation over the required number of cooling and heating cycles by the calculating means, average heat flux calculating means and calculating step shortening means to the shape data or output data. And an output means for performing the following operations.