JPH0469850B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a method for evaluating and determining optimal molding conditions for a molten material to obtain a high-quality molded product when molding a molten material such as a resin. In particular, the present invention relates to an evaluation method capable of determining the range of the molten material non-formable region temperature and the filling time at a required mold temperature and selecting the optimal range of the molten material temperature and the filling time.

[Conventional technology]

Conventionally, when performing a resin flow analysis (simulation) in a mold during injection molding using resin materials, the shape model of the molded product is divided into minute elements, and the finite element method and boundary element method are used, as shown in Figure 2. ,
A commonly used method is to calculate the equation of motion, continuity equation, energy equation, etc. of a fluid using numerical analysis methods such as the finite difference method and the FAN method.

In this method of analyzing resin flow inside a mold,
By selecting the resin to be used and inputting and calculating the resin temperature, mold temperature, and filling speed as the operating conditions of the molding machine, the total filling time can be set as an indicator of the progress (time) of resin filling. An isochronous diagram (see Figure 3), which was created by dividing the time period into the number of times and connecting the arrival position of the resin filled at each time with a line.
Similarly, an isopressure diagram created for pressure (see FIG. 4), an isotemperature diagram similarly created for temperature (see FIG. 5), etc. are determined by the respective required calculations.

[Problem that the invention seeks to solve]

However, in the conventional resin flow analysis method described above, there is no means for determining whether the input conditions are appropriate, whether there are any appropriate input conditions, or which one of several input conditions is the best. was not known, and therefore, the judgment of the suitability of the calculation results had to rely on empirical know-how obtained by repeatedly comparing the analysis results with actual molding.

In this way, the conventional resin flow analysis method in a mold involves inputting the resin temperature, mold temperature, filling speed, etc. that have been empirically obtained for the resin used.
Shape of molded product (product thickness, gate position and number,
The main purpose of this method is to determine the suitability of molding conditions (such as runner dimensions), and no attempt has been made to evaluate the suitability of molding conditions.

However, in this method of analyzing resin flow within a mold, at the stage when the design of the resin molded product is completed and before manufacturing the mold, calculations are performed on a program to determine whether molding is possible or difficult. The purpose is to determine the conditions required to produce molded products, and the suitability of the mold shape (product wall thickness,
In addition to determining the position and number of gates, gate and runner dimensions, etc., it is also desirable to calculate the appropriate molding condition range and optimal molding conditions, and ultimately determine all operating conditions of the molding machine. There is.

Therefore, an object of the present invention is to analyze the flow of molten material in a required molding die by determining the temperature of the area where molten material cannot be formed and the range of filling time for the required mold temperature, thereby determining the appropriate filling time. Another object of the present invention is to provide an evaluation method for flow analysis in mold forming of molten material, which allows selection of the optimum molten material temperature.

[Means for solving problems]

The evaluation method for flow analysis in mold forming of molten materials according to the present invention divides the molded product shape model into minute elements and uses numerical analysis methods including the finite element method, boundary element method, finite difference method, FAN method, etc. Then, the filling progress status of the molten material for each element of the molded product shape model is determined as an isochron diagram by calculating the filling arrival time, and the temperature at each element during filling or after filling is completed.
In a method for evaluating flow analysis in mold forming of molten material by calculating pressure, shear rate, shear stress, etc., for one or more molten material temperature conditions,
Analysis is performed by giving multiple filling times for each element, and the calculation results of the molten material temperature distribution at the time of completion of filling are used to calculate the average temperature of each element or the lowest molten material temperature among all elements of the intermediate layer temperature. A function with the filling time as a variable for the temperature of the molten material
The method is characterized in that it is determined as Tn=fn ₂ (t), and these functions are graphically displayed on a display device to evaluate and determine the appropriate range of molten material temperature and filling time at a predetermined mold temperature.

In the above evaluation method, the function Tn of the minimum melting material temperature at the completion of mold filling with the filling time as a variable
=fn ₂ (t), solidification temperature of the molten material used
Given a limit value based on Ts, the function can be evaluated to determine the appropriate melt material temperature and fill time range.

[Effect]

According to the evaluation method of flow analysis in mold forming of molten material according to the present invention, the minimum molten material temperature of each micro-divided element of the molded product shape model is calculated based on the calculation result of the molten material temperature distribution at the time of completion of filling. Find the filling time as a function as a variable, display these functions graphically on a display device,
It is possible to evaluate and determine the range of temperature and filling time in which molten material cannot be formed.

In this case, by giving a limit value to the reference temperature determined based on the solidification temperature of the molten material used for the function of the minimum molten material temperature at the completion of filling,
Appropriate melt material temperature and filling time ranges can be determined.

In general, as a criterion for flow analysis in mold molding of molten materials such as resin materials,
It is necessary to set the following molding conditions.

(1) The shorter the filling time, the better.

(2) The lower the filling pressure, the better.

(3) The lower the resin temperature, the better.

(4) The lower the mold temperature, the better.

That is, in the filling process, high-temperature molten resin is filled into a low-temperature mold, so the resin is cooled during filling, the temperature decreases, the viscosity increases, and the fluidity decreases. For this reason, if the filling speed is slow, pressure transmission will be insufficient, and the unevenness of the surface caused by the flow near the end of the mold cavity will not come into close contact with the mold cavity surface and will remain as flow marks, and the cooling process will be affected. This can lead to molding defects such as shrinkage due to failure to compensate for shrinkage, insufficient re-fusion at the weld area where the resin flows merge, formation of weld lines, and insufficient strength at the weld area. It is more likely to occur.

Therefore, it is desirable to complete the filling in as short a time as possible, but if the filling speed is too high, the resin may deteriorate due to local heating due to shear heat generation during flow, and the volatile content may vaporize as a result. silver streaks that form on the surface of the molded product, gas burns caused by the residual air in the mold cavity being trapped by the resin flow and adiabatic compression, and zonal flow caused by the flow path not being sufficiently filled in areas where the cross-sectional area rapidly expands. A defective phenomenon such as jetting occurs due to the formation and folding of this.

Therefore, as a means to complete filling in the shortest possible time without causing these molding defects,
Depending on the change in the cross-sectional area of the flow path in the mold cavity,
Control is generally applied in which the filling speed is programmed in multiple stages to prevent the flow speed in the mold from becoming too high.

In addition, filling pressure is generated as a load resistance when molten resin of a certain viscosity is filled into a mold at a certain temperature at a certain filling speed, and is expressed by the oil pressure of the injection cylinder performing filling. , it may be displayed as the molten resin pressure actually measured inside the mold. That is, this filling pressure is a parameter representing ease of filling, and a low pressure indicates that filling is easy, which is a desirable state. In continuous molding, the fact that the filling pressure value is stable from shot to shot indicates that molding of stable quality with little variation is being performed.

Further, both the resin temperature and the mold temperature are molding conditions related to the apparent viscosity, which indicates the ease of resin flow, and the higher both are, the lower the apparent viscosity is, and the easier it is to fill. On the other hand, considering the cycle operation of injection molding in which the molded product is cooled and taken out from the mold after filling is completed, these high temperatures will delay the molding cycle.

Therefore, if the viscosity of the molten resin can be suppressed to a certain level and the filling pressure and its stability can be satisfied, the temperature conditions of the resin and the mold should be as low as possible.

〔Example〕

Next, an example of the evaluation method for flow analysis in mold molding of molten material according to the present invention will be described in detail below with reference to the accompanying drawings.

In the present invention, the procedure for analyzing the resin flow within a mold for a shape model of a predetermined molded product is the same as that of the conventional simulation method. That is,
As shown in Fig. 2, in order to analyze the resin flow inside the mold, the shape model of the molded product is divided into elements (triangular elements are used in the illustrated example, but quadrilateral elements may also be used). Apply the finite element method. The position and number of gates G are set for this shape model of the molded product, and runners are provided as necessary to complete the setting of the mold side shape for flow analysis. Here, after selecting the resin to be used and inputting resin physical property data, inputting molding conditions such as resin temperature, mold temperature, and filling speed, the process moves to analysis. The procedure up to this point is similar to the conventional resin flow analysis in a mold (see FIGS. 3 to 5).

Next, in this example, the mold temperature is fixed (60°C), and one or more resin temperatures are set, for example, the temperature of the resin flowing into the mold is set to 200°C, 220°C, 260°C.
Three types of temperatures were selected, and molding conditions were set for each resin temperature with six types of filling time: 0.2, 0.5, 1, 2, 3, and 4 seconds, and analytical calculations were performed sequentially. Among the calculated data obtained as a result, the lowest resin temperature of each element of the shape model is extracted using the resin temperature distribution data at the time of completion of filling, and is used as data at that filling time. If you graph the data obtained by repeating this procedure, you will get a characteristic curve diagram as shown in Figure 1, with the resin temperature at a constant mold temperature as a parameter, the filling time on the horizontal axis, and the minimum resin temperature on the vertical axis. is obtained.

Therefore, if we formulate the characteristic curve shown in Figure 1, we get
The following equation is obtained.

Tn=fn ₂ (t) (n=1, 2, 3) (1) In FIG. 1, Ts indicates the solidification temperature level of the resin. Therefore, this solidification temperature
Below the level of Ts, resin molding is not possible.

By the way, in general, in injection molded products, the flow becomes incomplete even if the resin temperature does not drop to the solidification temperature Ts, depending on the wall thickness and the distance from the gate to the flow end, so the function Tn is A temperature not lower than a reference value (Ts+α) based on the solidification temperature Ts can be used as a criterion for evaluating the flowability limit. However, the tendency of the flow of molten resin in injection molding varies depending on the physical properties of the resin used and the thickness and shape of the molded product, so the standard value (Ts + α)
Although it is difficult to make an absolute evaluation of the α value that should be kept within, it is better to understand the trends of changes when changing the resin temperature and filling time. This is important for determining conditions.

Therefore, the graph shown in Figure 1 can be used for LCD, CRT,
Graphical display on a display device such as plasma or EL is effective in determining appropriate conditions. Furthermore, by graphically displaying the graph shown in Fig. 1 on a display device, it is possible to determine the non-formable area in relation to the reference value (Ts + α), and if these functions are expressed mathematically,
By giving a limit value to the α value that determines the reference value (Ts+α), an appropriate filling time range and optimum resin temperature can be selected on the display device through interactive operation.

[Effects of the Invention] As is clear from the examples described above, according to the present invention, the viscosity of the molten resin can be maintained at a predetermined level with respect to the resin temperature and the mold temperature, and the magnitude and stability of the filling pressure can be satisfied. The minimum resin temperature and filling time range can be easily determined under the appropriate conditions.

Therefore, according to the present invention, when performing resin flow analysis on a molded product shape model, molding conditions for obtaining a high-quality molded product can be easily determined using a simple graphical display, and the determination results can be used to Based on this, various appropriate molding conditions can be selected, which has an extremely large effect in contributing to the creation of a mold molding program for molten resin.

In addition, in the above-mentioned example, the evaluation method of flow analysis in mold molding of molten resin was explained, but the present invention is not limited to this example, and can be applied to mold molding of molten materials other than resin, e.g. It goes without saying that the present invention can also be applied to a die-casting machine, and that various other design changes can be made without departing from the spirit of the present invention.

[Brief explanation of drawings]

FIG. 1 shows an example of the evaluation method of flow analysis in mold molding of molten material according to the present invention.
A graphic display showing the minimum resin temperature characteristics with respect to filling time with resin material temperature as a parameter,
Figure 2 is a display diagram showing the state in which the molded product shape model is divided into three-dimensional minute elements, Figure 3 is an isochronous diagram of the filling pattern in the shape model shown in Figure 2, and Figure 4 is the diagram shown in Figure 2. FIG. 5 is an isopressure diagram of the filling pattern in the shape model shown in FIG. 2, and FIG. 5 is an isotemperature diagram of the filling pattern in the shape model shown in FIG.

Claims (1)

[Scope of Claims] 1 A molded product shape model is divided into minute elements, and each element of the molded product shape model is divided using a numerical analysis method including a finite element method, a boundary element method, a finite difference method, a FAN method, etc. The filling progress of the molten material is calculated as an isochron diagram by calculating the filling arrival time, and the temperature, pressure, shear rate, shear stress, etc. at each element during filling or after filling is calculated. In a method for evaluating flow analysis in mold forming, for one or more molten material temperature conditions,
Analysis is performed by giving multiple filling times for each element, and the calculation results of the molten material temperature distribution at the time of completion of filling are used to calculate the average temperature of each element or the lowest molten material temperature among all elements of the intermediate layer temperature. A function with the filling time as a variable for the temperature of the molten material
The function of molten material is calculated as Tn=fn ₂ (t), and these functions are displayed graphically on a display device to evaluate and determine the appropriate range of molten material temperature and filling time at a predetermined mold temperature. Evaluation method for flow analysis in mold forming. 2. In the evaluation method for flow analysis in mold forming of molten material as described in claim 1, the function Tn = fn ₂ (t) of the lowest molten material temperature at the time of completion of mold filling with filling time as a variable. On the other hand, give a limit value based on the solidification temperature Ts of the molten material used,
An evaluation method for flow analysis in mold forming of molten material, comprising evaluating the function to determine an appropriate range of molten material temperature and filling time.