JP3071241B2 - Appearance defect prediction method for injection molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for predicting a defective appearance of an injection-molded product applied to a mold design technique, an injection molding method, and the like.

[0002]

2. Description of the Related Art Conventionally, as a method for predicting an appearance defect in an injection molded product, resin data, mold shape data, and molding condition data are input to a filling analysis module, and analysis processing of the filling analysis module is performed. By executing the method, the pressure, temperature, shear rate, and viscosity of the resin are obtained every moment, and the position of the weld line and the short shot are predicted based on the calculation results. The result of the prediction is output as a graphic by a graphic terminal.

[0003]

Problems to be Solved by the Invention Incidentally, in the injection molding process, the occurrence of appearance defects greatly affects the quality of a molded product. Therefore, a technique for predicting the appearance defects is now indispensable. . However, the conventional filling analysis can only predict the weld line position and the quality of the short shot as described above, and various appearance defects such as burn, flow mark, silver, mela, sink mark, sled, burr, etc. Cannot be predicted.

The present invention has been made in view of such a problem, and an object of the present invention is to provide a method capable of predicting burn in the above-mentioned poor appearance.

[0005]

Means for Solving the Problems According to claim 1 and claim 2
The corresponding inventions are referred to as Invention 1 and Invention 2 , respectively, and means for achieving the above objects are described below for each invention .

According to the method for predicting the appearance defect of an injection-molded article according to the first aspect of the present invention, at an arbitrary time during the process of forming the injection-molded article, the Navier-Stokes is used on the basis of resin data, mold shape data and molding condition data. Sto
By calculating the flow field using the equations of motion, continuity equation and energy equation of (kes), the temperature at a predetermined position is calculated to form an injection molded product at an arbitrary time, and at an arbitrary time from the calculation result, When the cumulative temperature obtained by integrating the temperature at a predetermined distance from a predetermined position in the distance direction is equal to or more than a predetermined value, it is characterized by determining that burns occur at an arbitrary time.

The method for predicting the appearance defect of an injection-molded article according to the second aspect of the present invention is based on resin data, mold shape data and molding condition data at any point and at any time on the injection-molded article. By calculating the flow field using the equations of motion, continuity equation and energy equation of Stokes), the instantaneous temperature in the flow process of the resin at an arbitrary point and at an arbitrary time is calculated, and the arbitrary point and A temperature history of the resin is obtained at an arbitrary time, and then an accumulated temperature is obtained based on the temperature history. If the accumulated temperature is equal to or more than a predetermined value, an arbitrary point and an arbitrary time corresponding to the value of the accumulated temperature are obtained. Is characterized by determining that burn occurs.

[0008]

[Action] of the molding resin burnt is greater than the thermal energy given threshold resin is subjected, Ji raw by thermal degradation
You.

Therefore, in the first aspect , the relationship between the position and the accumulated temperature at an arbitrary time is obtained, and it is determined whether or not the accumulated temperature is equal to or higher than a predetermined value, thereby predicting the time at which burns occur. be able to. In the second aspect , the relationship between the accumulated temperature at an arbitrary time and an arbitrary position is determined, and it is determined whether or not the accumulated temperature is equal to or higher than a predetermined value. Can be predicted.

[0010]

FIG. 1 is a system flowchart according to an embodiment of the present invention. This flowchart is for Invention 1 and Invention 2.
However, each invention is characterized by the processing content of ST4 in the flow analysis module M. Therefore, embodiments of the present invention will be described in detail below with reference to the drawings while clarifying the point.

The broken lines in FIG. 1 show the flow of data from each file. The data for flow analysis is
It consists of shape data, resin data and molding condition data stored in the database 4 and is used for calculation in the flow analysis module M. Here, the shape data is data on the cavity shape of the mold used,
It is obtained by dividing the mold shape into minute finite elements, and a flow analysis module M described later performs a flow analysis for each of these elements. The resin data incorporates information on physical properties such as the viscosity, specific heat, density, and solidification temperature of the resin. The molding condition data is data incorporating molding conditions for performing injection molding, that is, information such as the temperature of the injected resin, the temperature of the mold, and the injection time.

The above three types of data are input from the database 4 to the flow analysis module M (ST).
1). Next, in the flow analysis module M, flow analysis is performed by the following algorithm using the above input data. That is, the flow field of the molding resin is obtained from the equation of motion given by equation (1), the equation of continuity given by equation (2), and the equation of energy given by equation (3). The flow field is determined as a function of position and time, and therefore, the amount of heat given to the resin from time to time is determined together with position information and time information. The temperature history of the resin, which changes every moment, can be obtained from the heat quantity thus obtained (ST).
2).

Equations (1), (2) and (3) can be applied to a thin flat plate in a cavity. In the case of a cylindrical shape such as a flow path,
These equations can be applied by converting to a cylindrical coordinate system.

[0014]

(Equation 1)

[0015]

(Equation 2)

[0016]

(Equation 3)

Next, the calculation result of the flow analysis performed in ST2 is output to the intermediate file 5 (ST3). Next, based on the calculation results of the flow analysis stored in the intermediate file 5, in Invention 1, the burn prediction equation given by Equation (4) is used.
Then, a prediction index of burn during the resin filling process is calculated. You
That is, any time during the time when the resin is filled into the mold,
The cumulative temperature の at each position of the time is obtained. Here the judgment reference value
Is set to { ₀ } and compared with the resin temperature at an arbitrary point. Its ratio
Judgment by comparison is that if ζ ≧ ヤ ₀ , burns occur
And, on the other hand in the case of zeta <zeta ₀ and burnt it does not occur.

[0018]

(Equation 4)

Next, in the second invention, (5) using the burnt prediction equation given by equation calculates a predictor of scorch during the filling process of the resin. That is, the accumulated temperature の at an arbitrary position at an arbitrary time during the time when the resin is filled in the mold is obtained. Here, the determination reference value is set to { ₀ }, and is compared with the resin temperature at an arbitrary point. Determination by the comparison, if the zeta ≧ zeta ₀ and scorch occurs if the contrast zeta <zeta ₀ and burnt does not occur. (ST4).

[0020]

(Equation 5)

The calculation results of the burnt prediction formula, i.e. a poor appearance calculation data, and outputs calculation results of the flow field at the same time results in a file 6 in ST2 (ST5). Next, these data stored in the result file 6 are input as graphic software data (ST6). Thereafter, format conversion is performed on the graphic software data so as to match the format of the graphic file format (ST7), and the format-converted graphic processing conversion data is output to the graphic file 7 (ST8).

[0022] Next, the graphic processing by using the data of the graphic file 7 (ST9), for drawing outputs the appearance defect occurrence position on the graphic terminal. In the output drawing, the level indicating the degree of burn can be identified by color. (ST10). FIG. 2 is a block diagram of a system configuration for realizing the embodiment of the present invention as described above.

The input terminal 1 inputs shape data, resin data and molding condition data from the database 4. Using the data input from the input terminal 1, the main computer 2 performs the above-described flow analysis calculation, burn prediction calculation,
And perform graphic processing. After each process is performed, the result is output to the intermediate file 5, the result file 6, and the graphic file 7, respectively. The graphic output terminal 3 outputs an appearance defect predicted image subjected to the graphic processing.

Next, the prediction method of each invention, by way of further detail example will be described.

FIG . 3 is a diagram for explaining the first invention. That is, in this figure, the arbitrary time is a time zone in which the resin flows in all the runner gates, and the distance and temperature obtained by performing the flow analysis calculation using the flow analysis data shown in Table 1 are shown. 3 illustrates the relationship between the temperature and the accumulated temperature.

[0026]

[Table 1]

[0027] Here, of the two types of curve, a-I, a-II
Is a temperature curve representing the relationship between position and temperature, and b-I, b-I
I is a cumulative temperature curve representing the relationship between the position and the cumulative temperature. B-I and b-II are values obtained by integrating a-I and a-II in the distance direction, respectively. In this case, the flow rates of a-I and a-II are constant, and the difference between the conditions of a-I and a-II is the flow rate, and the flow rate of a-I is larger. In both temperature curves a-I and a-II, shear heat is generated in the runner portion, shear heat is further increased in the gate portion where the flow path cross-sectional area is reduced, and in the product portion where the flow rate is diffused, shear heat is generated. The cooling effect from the surface is greater, the temperature goes down, and the curve follows a downward line. Since there is a difference in the flow rate between a-I and a-II, the shear heat generation is larger in the a-I curve with the larger flow rate, and the temperature is higher than in the a-II. Therefore, the cumulative temperature curves b-I and b-II rapidly rise at the runner and the gate portion where the temperature is high, and eventually become constant. Further, in the vicinity immediately greater cumulative temperature curve b-I in the gate of the flow rate exceeds the criterion value zeta ₀ desperation, while not reached the stage b-II in the determination reference value zeta _0.

[0028] In other words, burns occur under the conditions of a-I and b-I.
However, under the conditions of a-II and b-II, no burn was found.
Can be determined. If burns occur, the degree of burns
Is the judgmentReference valueζ₀Between level 1 and level
The five-level display of the rule 5 is performed. Figure4(A) and (B)
Light2FIG. Figure4In (A), a certain resin
Thermal wear that has been received up to any point in the product after entering
Temperature curve diagram showing history, time t, distance from resin injection part
Let l and resin temperature T be the x-axis, y-axis, and z-axis, respectively.
It is a three-dimensional graph. Also figure4(B) is a figure4
Cumulative temperature obtained by integrating the temperature curve of (A)
In the degree curve, the time t, the distance l from the resin injection part and the cumulative
Temperature ζ is a three-dimensional graph with x, y, and z axes, respectively.
It is rough.

Firstly, FIG. 4 (A), the shearing heat generation occurs at the runner part, further increases the shear heating in the gate portion the flow path cross-sectional area decreases from the surface than the shear heat generation in the product portion of the flow is diffused Because the cooling effect is greater, the temperature decreases. On the other hand, it soared in FIG 4 (B) the temperature of a high runner and gate section, exceeds the criterion value zeta ₀ desperation at H ₁ immediately after the gate. By reading the values of the points H ₃ and H ₂ that project the point H ₁ on the x-axis and the y-axis, respectively, the time and position at which the burn occurs can be obtained at the same time. The degree of burn is the temperature at which the judgment reference value ζ ₀
Five levels from level 1 to level 5 are displayed according to the difference .

When the above-described prediction method is performed for each resin having a different injection pattern, the time zone and the position where burns occur can be accurately predicted as a whole.

[0031]

As described above, according to the first aspect,
Predetermined from a predetermined position at any time
Whether or not the accumulated temperature at the distance of
Judgment analysis module in simulation method
The appearance of the injection molded product is poor
Burn can be easily and accurately predicted. Also, the forming strip
It is possible to review the matter in advance. I
In this case, since the accumulated temperature is used as a criterion,
The total amount of resin that changes every moment as time passes
Judgment on calorific value allows for more accurate burn prediction
Measurement results can be obtained.

According to the second aspect of the present invention, when the cumulative temperature based on the temperature history of the resin is equal to or higher than a predetermined value at an arbitrary point and an arbitrary time, the above-mentioned arbitrary point corresponding to the cumulative temperature value and The same effects as those of the first aspect can be obtained also by incorporating an analysis module that determines that burns occur at an arbitrary time into the simulation method. Moreover, in this case, since the analysis is performed using a three-dimensional graph, the time zone and the position where the burn occurs can be obtained at the same time, so that the accuracy of the prediction is further improved.

Furthermore, these results, it is possible to create a mold burnt does not occur, thereby improving the quality and yield of the molded article. In addition, even when correcting a mold, since a correction portion or the like can be specified based on a simulation result in advance, the cost of the correction can be reduced, and the time required for the correction can be shortened. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a system flowchart according to an embodiment of the present invention.

FIG. 2 is a block diagram of a system configuration for realizing an embodiment of the present invention;

FIG. 3 is a diagram for explaining an embodiment of the invention 1 ;

FIG. 4 is a view for explaining an embodiment of the invention 2;

[Explanation of symbols]

 1 Input terminal 2 Main computer 3 Graphic output terminal 4 Database 5 Intermediate file 6 Result file 7 Graphic file

Claims (2)

(57) [Claims] 1. At an arbitrary time during a process of forming an injection molded article, a Navier Stokes (Navi Stokes) is formed based on resin data, mold shape data and molding condition data.
By calculating the flow field using the equation of motion, continuity equation, and energy equation of er-Stokes), the temperature at a predetermined position to form the injection molded article at the arbitrary time is calculated, and from the calculation result, At an arbitrary time, if the accumulated temperature obtained by integrating the temperature at a predetermined distance from a predetermined position in the distance direction is equal to or more than a predetermined value, it is determined that burn occurs at the arbitrary time. A method for predicting appearance defects in injection molded products. 2. At an arbitrary point and an arbitrary time of an injection-molded article, a Navier-Stokes is performed based on resin data, mold shape data and molding condition data.
The instantaneous temperature in the flow process of the resin at the above-mentioned arbitrary point and at any time is calculated by calculating the flow field using the equation of motion, continuity equation and energy equation of Determine the temperature history of the resin at a point and any time, then determine the cumulative temperature based on the temperature history, and if the cumulative temperature is equal to or more than a predetermined value, the arbitrary point corresponding to the value of the cumulative temperature and A method for predicting appearance defects in an injection-molded article, which determines that burns occur at an arbitrary time.