JPH05245894A - Method for determining mold-cooling water flow rate in injection molding - Google Patents

Abstract

PURPOSE:To prevent the generation of defects by setting shape models of a molded product and cooling pipe models of a plurality of systems of a molding die for manufacturing the molded product in a manner of forming a positioning relation in the molding die and simulating the temperature distribution of shape models of the molded product using the cooling water flow rate as a parameter. CONSTITUTION:Simulation analysis is performed by using the set cooling water flow rate, and the temperature distribution of shape models 1a and 1b of a molded product is computed after the given time is passed. Then, a site P where said temperature distribution comes up to the maximum temperature and the temperature and the minimum temperature are found. The temperature difference between said maximum and minimum temperatures is computed and whether the difference value computed is within the allowable value or not is determined. In the case the difference is not within the allowable value, only the cooling water flow rate data of a system 25 of a cooling pipe 2 in the position closest to the site of maximum temperature out of the flow rate data used in the analysis is changed into the data in which the given flow rate only is increased. The processes are repeated until a value within the allowable value is obtained. Manufacturing can be started just after building up a molding line by said arrangement.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for determining a cooling water flow rate of a resin molding die.

[0002]

2. Description of the Related Art When a resin material in a molten state is injected into a molding die for molding, the molded product is deformed after being released from the mold. This occurs because the temperature distribution of the molded product is not uniform throughout and the temperature is partially high or low. When such a deformation defect occurs, conventionally, the molding engineer makes an adjustment such as setting the cooling water temperature of the cooling pipe of the system at a position close to a place where the deformation amount of the molded product is large, or It was dealt with by adjusting the flow rate of cooling water and adjusting the cooling time.

[0003]

By the way, according to the above countermeasure, it is necessary for the molding engineer with experience to perform the adjustment work, and the adjustment is performed only by the experience and intuition of the molding engineer. It is difficult to handle the adjustment work quantitatively, and it takes a considerable amount of time. Therefore, conventionally, it was necessary to spend a considerable amount of time for determining the cooling water flow rate before starting the production.

The present invention has been made to solve the above-mentioned conventional problems, and its object is to make the temperature distribution of the resin molded product uniform so that the deformation of the resin molded product falls within an allowable range. It is an object of the present invention to provide a method capable of determining the flow rate of cooling water for realization before starting the production of molded articles.

[0005]

Means for Solving the Problems As shown in FIGS. 1 and 2 corresponding to an embodiment, the method of the present invention includes shape models 1a and 1b of molded products and a plurality of systems 2 of molding dies for making the molded products.
An analysis for simulating the temperature distribution of the shape models 1a and 1b of the molded product after a predetermined time by setting the cooling pipe model 2 of 1 ... 28 to have a positional relationship in the molding die and using the cooling water flow rate as a parameter. A method for determining the cooling water flow rate to a molding die by using a method, wherein the above-mentioned simulation analysis is performed using the set cooling water flow rate, and the shape model 1a, 1b of the molded product after a predetermined time. The temperature distribution is calculated (ST6), and the maximum temperature P, its temperature Tmax and minimum temperature Tmin are calculated from the temperature distribution (ST7), and the temperature difference between the maximum temperature Tmax and the minimum temperature Tmin is calculated. It is determined whether or not the calculated difference value is less than or equal to the allowable value Tc (ST8). If the result of the determination is not less than the following, among the flow rate data used in the above-mentioned analysis (ST6), Maximum temperature Tma Only the cooling water flow rate data of the system 25 of the cooling pipe 2 at the position closest to the part where x becomes
Change to data increased by a predetermined flow rate Δv (ST9, ST5),
It is characterized in that these steps 〓, 〓 and 〓 are sequentially repeated until the judgment result in the above 〓 becomes equal to or less than the allowable value Tc.

[0006]

[Operation] The heat transfer between the mold and the cooling water is determined by the heat transfer coefficient, and the relationship can be expressed by Equation 1.

[0007]

[Equation 1]

Further, when the cooling water is turbulent, the heat transfer coefficient is expressed by equation (2).

[0009]

[Equation 2]

Therefore, if the speed of the cooling water, that is, the flow rate per unit time increases, the heat transfer increases and the cooling effect increases. Therefore, steps 〓, 〓 and 〓
By repeating the above, the difference between the maximum and minimum temperatures of the temperature distribution of the shape models 1a and 1b of the molded product becomes smaller.
Then, when the temperature difference becomes equal to or less than the allowable value Tc,
It is possible to obtain a cooling water flow rate in which the temperature distribution of the molded product is almost uniform throughout.

[0011]

First, the present invention is basically a CAE (Comp
uter Aided Engine-ering) system or the like, which is a method for determining the cooling water flow rate of a molding die, and an example thereof will be described below with reference to the drawings.

FIG. 1 is a flow chart showing the procedure of an embodiment of the method of the present invention. First, a shape model of a molded product and a cooling pipe model consisting of multiple systems are created to analyze the molded product temperature distribution after a predetermined time by the boundary element method or the difference method using the cooling water flow rate as a parameter (ST1 ). In this example, as shown in FIG. 2, the shape models 1a and 1b of the molded product and the cooling pipe model 2 including a plurality of systems 21 ... To do.

When the initial data of the cooling water flow rate and the cooling time t seconds are input (ST2, ST3) after the above-mentioned analysis model creation is completed, the first cooling analysis is performed based on these input data. Shape model 1 of the molded product
Is calculated (ST6), and from the temperature distribution of the molded product obtained by this cooling analysis, the maximum temperature portion P and its temperature Tmax and the minimum temperature portion Q temperature Tmin are obtained (ST7).

Next, the maximum and minimum temperature difference (Tmax-Tmi
n) is calculated, and it is determined whether or not this calculation result is less than or equal to the allowable value Tc (ST8). If not, the system of the cooling pipe closest to the part where the maximum temperature of the molded product temperature distribution is reached. Obtain the data obtained by increasing the cooling water flow rate data by Δv (ST9). For example, in FIG. 2, when the temperature of the part P of the shape model 1b of the molded product reaches the maximum temperature Tmax, correction is performed by adding Δv to the cooling water flow rate data of the cooling pipe system 25, and thereafter, Return to step ST4.
It should be noted that Δv is a value that has been input and stored in advance in this analysis system.

Regarding the cooling analysis after this, that is, the second and subsequent analyzes, first, each system 21 ...
Of the cooling water flow rate data of No. 8, only the flow rate data of the system that was calculated in step ST9, for example system 25, is changed to the data after the previous calculation (ST5), and then the cooling analysis and the calculation of the temperature difference are performed. When the temperature difference after this calculation is not less than the allowable value Tc, the process proceeds to step ST9, and steps ST5 to ST9 are sequentially repeated again. Then, in the judgment step ST8, the judgment result is the allowable value Tc.
When the following occurs, the cooling water flow rate data of each system 21 ... 28 of the cooling pipe 2 is collected, and the flow rate data is displayed on a screen such as a CRT or printed out (ST10). ).

By the above procedure, the cooling water flow rate that can make the temperature distribution of the molded product substantially uniform over the whole can be determined for each system 21 ... 22 of the cooling pipe 2. Then, the pressure or valve opening of the pump connected to the cooling pipe of each system is adjusted so that the obtained cooling water flow rate is obtained.
This adjustment may be performed by an operator while looking at the flow meter, or if there is an automatically adjustable device, the cooling water flow rate may be set in that device. Here, since the allowable value Tc of the judgment step ST8 is different due to the difference in the shape and size of the molded product to be produced, the type of resin, etc., no particular numerical value is shown in this example, but the allowable value Tc is, for example, Even if there is variation in the temperature distribution of the product, the temperature range where the molded product does not deform,
Based on various conditions such as the shape and size of the molded product, the type of resin to be injected, its temperature, and the cooling time, it may be obtained in advance by calculation and the calculated value may be adopted.

[0017]

As described above, according to the method of the present invention, the cooling water flow rate that can make the temperature distribution of the molded product uniform, that is, prevent the defective deformation of the molded product from occurring is determined by the cooling analysis simulation. Since it is possible to do so, the work such as determining the flow rate of the cooling water by dummy molding which has been conventionally performed is unnecessary, and it becomes possible to start the production immediately after the molding line is constructed. Moreover, the cooling water flow rate can be easily determined even by an experienced molding engineer.

[Brief description of drawings]

FIG. 1 is a flow chart showing the procedure of an embodiment of the method of the present invention.

FIG. 2 is a diagram showing an example of a shape model of a molded product and a cooling pipe model used in the embodiment.

[Explanation of symbols]

 1a, 1b ・ ・ ・ ・ Shape model of molded product 2 ・ ・ ・ ・ ・ ・ Cooling pipe model 21 ・ ・ 28 ・ ・ ・ ・ System of cooling pipe

Claims (1)

[Claims] 1. A shape model of a molded product and a plurality of cooling pipe models of a molding mold for forming the molded product are set to have a positional relationship in the molding mold, and a cooling water flow rate is used as a parameter for a predetermined time. A method of determining the cooling water flow rate to the molding die by using an analysis method for simulating the temperature distribution of the shape model of the molded product afterwards, in which the above simulation analysis is performed using the set cooling water flow rate. Calculate the temperature distribution of the shape model of the above molded product after a predetermined time,
Next, from the temperature distribution, find the maximum temperature, its temperature and minimum temperature, and calculate the temperature difference between the maximum temperature and the minimum temperature to determine whether this difference calculation value is below the allowable value. However, if the judgment result is not below,
Of the flow rate data used in the above-mentioned analysis, only the cooling water flow rate data of the cooling pipe of the system closest to the part where the maximum temperature is reached is changed to the data increased by a predetermined flow rate. A method for determining the mold cooling water flow rate in injection molding, characterized in that the steps 〓, 〓 and 〓 are sequentially repeated until the judgment result in the above 〓 becomes less than the allowable value.