JP3107622B2 - Molding process simulation method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding process simulation of injection molding, and more specifically, to predict in advance deformation defects such as warpage and sink in molded products at the time of designing a thermoplastic resin product or a mold. The present invention relates to a molding process simulation method and apparatus capable of performing the same.

[0002]

2. Description of the Related Art In recent years, in the field of numerical calculation, a molding process simulation for simulating the deformation behavior of a product from filling to holding pressure, cooling and release in injection molding (that is, behavior of a resin in a molding process). The system is finally being developed.

[0003] As such a conventional molding process simulation system, one disclosed in Japanese Patent Application Laid-Open No. 2-258229 has been proposed.

In this molding process simulation, a change in the temperature of the molding material during the molding process is calculated, a time point at which the connection of the molten phase of the molding material is cut off is calculated from the temperature change of the molding material, and the temperature of the molten phase is calculated. The thermal stress strain is calculated by using the temperature distribution of the molded product at the time of cutting, and the shape distortion such as uneven molding shrinkage is calculated from the displacement due to the thermal stress strain.

FIG. 2 shows a method of calculating the shape distortion based on this theory. FIG. 2 shows the relationship among the pressure, temperature, and specific volume of the molding resin.

In FIG. 2, assuming that the pressure at the start of molding shrinkage is P11 and the temperature is T11, the specific volume v1 in this state is as follows.
1 is determined. When the pressure is the atmospheric pressure P10,
The temperature at which the specific volume is v11 is T12. Then, as shown in FIG. 2, the difference between the specific volume v11 determined by the pressure P11 and the temperature T11 and the specific volume v12 determined by the atmospheric pressure P10 and the room temperature T10 is the specific volume v11 determined by the atmospheric pressure P10 and the temperature T12. This is the same as the difference from the specific volume v12 determined by the atmospheric pressure P10 and the room temperature T10.

Assuming isotropic, (v12 / v11)
The value obtained by subtracting 1 from the cubic root of the molding becomes the molding shrinkage ratio. Therefore, the pressure P11 and the temperature T1 are calculated using the pressure, specific volume, and temperature data.
When T1 is given, T12 that makes the molding shrinkage the same can be calculated. By using this relationship, the temperature T1 at the start of molding shrinkage corrected in consideration of the pressure dependency of the specific volume of the resin.
2 is obtained for each part of the molded article. Then, a thermal stress-strain analysis is performed by using a temperature difference between the obtained temperature and the room temperature T10 as a thermal load condition, and a deformation amount is calculated.

[0008]

However, in this method, the pressure P and the temperature T at the time when the molten phase inside the resin is cut off, on the assumption that the cooling in the mold is sufficiently performed. Is calculated, the specific volume v and the temperature T at the atmospheric pressure P are obtained, and the thermal stress-strain analysis is performed by using the specific volume v as the molding shrinkage starting temperature. In other words, it is possible to simulate only when the molded product is sufficiently cooled in the mold and the pressure of each part of the molded product is completely at the atmospheric pressure, and the original purpose is inappropriate molding conditions (cooling conditions).
In addition, the amount of deformation due to thermal deformation strain in such a state cannot be predicted.

[0009] This point will be described more specifically.

FIG. 3 shows such an inappropriate state. That is, if the cooling is originally sufficient, the resin temperature changes from T11 to T12 or less before the mold is opened. However, if the cooling is not enough, the resin temperature becomes T13 when the mold is opened.
It has only declined. If you open the mold in this state,
The specific volume of the molded product becomes v13, and a change from this state to v12 occurs.

That is, according to the conventional method, there is a problem that the amount of change is underestimated unlike the actual state in order to calculate the change from T12, that is, from v11 to v12.

The present invention has been made in view of the above circumstances, and an object of the present invention is to predict an inappropriate molding condition and predict a deformation defect in the state, thereby making it possible to take a measure in advance. To provide a molding process simulation method and an apparatus therefor.

[0013]

In order to solve the above-mentioned problems, a molding process simulation method according to the present invention comprises a molding process simulation for evaluating a mold structure, molding conditions, molding material, and the like. Calculate the temperature change, pressure, and specific volume change of the molded product, calculate the point at which each part of the molded product separates from the mold wall surface, and use the temperature distribution of the molded product at that time as the initial value to determine the heat transfer between the atmosphere and the molded product. of
Perform calculations and calculate the temperature until the temperature of the entire molded product reaches the ambient temperature.
Calculate the temperature distribution of the molded product at each time , and calculate the temperature distribution at each time.
The thermal stress strain at each time is calculated using the temperature distribution data of the molded article, and the deformation due to the thermal stress distortion is used to calculate a shape change such as warpage or sink of the molded article.

Further, the molding process simulation apparatus of the present invention calculates at least a temperature change, a pressure, and a specific volume change of a molding material during a molding process in a molding process simulation for evaluating a mold structure, molding conditions, molding material, and the like. In- mold cooling that calculates the temperature at which each part of the molded product separates from the mold wall surface based on the pressure data calculated by the pressure-flow analysis unit to perform and the temperature distribution of the molded product at that time. Determined by the analysis unit and the in- mold cooling analysis unit
Using the measured temperature distribution as the initial value, heat transfer between the atmosphere and the molded product
Until the temperature of the entire molded product reaches the atmospheric temperature.
Out-of-mold cooling analysis unit that calculates the temperature distribution of the molded product at each time
And each hour calculated by this out-of-mold cooling analysis unit
A configuration including a thermal stress strain analysis unit that calculates thermal stress strain at each time using temperature distribution data of a molded product, and calculates a shape change such as warpage or sink of the molded product from deformation due to the thermal stress strain. And

[0015]

In the injection molding, the molding resin is filled into the mold at high temperature and pressure (filling process), the pressure in the mold is kept constant to compensate for the amount of shrinkage due to cooling (pressure keeping process),
A process in which the compensating flow is lost and the pressure is reduced by cooling (cooling process), and a process in which the molded product is separated from the mold and deformed to room temperature by thermal strain (thermal stress process).

In order to predict the deformation behavior of such a molding resin, the behavior of an example of a filling process, a dwelling process, a cooling process, and a thermal stress process is simulated.

That is, in the cooling process, since the resin in each part of the molded article is cooled by the mold, the pressure is reduced at a constant specific volume as indicated by the line shown in FIG. Then, the pressure becomes atmospheric pressure (indicated by reference numeral a in FIG. 3) or the pressure is released by the mold opening (indicated by reference numeral b in FIG. 3), and the mold is separated, and from this time (reference numeral a or b) It is thought that the deformation starts.

Therefore, the pressure, temperature, and specific volume at the time when the compensation flow is stopped in the cooling analysis unit are set as initial values, and the analysis of the heat transfer between the mold and the molded product is performed for each time. The temperature T of the molded product at the time is obtained. Then, the pressure P is calculated from the temperature T and the specific volume v in the initial state.

Here, the temperature at which the pressure P has decreased to the atmospheric pressure before the mold opening time has reached the atmospheric pressure, and the mold whose pressure P has not decreased to the atmospheric pressure before the mold opening time has opened the mold. The temperature at the time is stored in the storage unit. Further, by calculating the time until the pressure P of the entire molded article becomes zero (atmospheric pressure), the time can be set as the optimum cooling time.

Next, based on the temperature distribution at the time of opening the mold stored in the storage unit, the heat transfer between the atmosphere and the molded product is calculated, and the temperature of the molded product at each time is calculated. To be stored.

The thermal stress / strain analysis unit calculates the amount of sink and warp deformation due to the thermal strain of the molded product based on the temperature distribution stored in the storage unit.

[0022]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an electrical configuration of an apparatus for executing a molding process simulation method according to the present invention.

In FIG. 1, a filling analysis unit 11 for calculating a change behavior of pressure, temperature, etc. of a molding resin in a process of filling a molten resin into a mold at a high temperature and a high pressure includes a shape data of a molded product or a mold. Molding condition data and resin physical property data are given. The shape data is data of nodes and elements obtained by dividing the element, and the molding condition data are filling time (injection rate), holding pressure, holding pressure, mold temperature (distribution), and injection resin temperature. Etc., and the resin physical property data includes viscosity, equation of state, and thermal characteristics (thermal conductivity,
Specific heat, solidification temperature, heat of crystallization, etc.).

The output of the filling analysis unit 11 is a pressure-holding flow analysis unit 12 for calculating the change behavior of the resin pressure, temperature, specific volume, and the like in the compensating flow process from the completion of filling to the stoppage of the compensating flow (gate seal). The output of the pressure-holding flow analysis unit 12 is guided to an in-mold cooling analysis unit 13 that performs a cooling analysis in the mold. Then, the in-mold cooling analysis unit 1
The output of the third storage unit 17 stores the analysis result.
And an out-of-mold cooling analysis unit 14 that performs a cooling analysis outside the mold. The output of the out-of-mold cooling analysis unit 14 is a second storage unit 18 that stores the analysis result, It is led to a thermal stress / strain analysis unit 15 that calculates the amount of deformation due to thermal strain. The output of the first storage unit 17 is output from the out-of-mold cooling analysis unit 14.
The output of the second storage unit 18 is led to the thermal stress / strain analysis unit 15, and the output of the thermal stress / strain analysis unit 15 includes a CRT or the like that outputs a deformation diagram based on the analysis result of the thermal stress / strain. The configuration is guided to the output unit 16.

[0026] Next, describes the operation Nitsu the molding process simulation device configured as described above.

The filling analysis unit 11 performs molding in a process of filling the molten resin into the mold at a high temperature and a high pressure based on the shape data of the molded product or the mold, the molding condition data and the resin physical property data given as the initial conditions. The change behavior such as the pressure and temperature of the resin is calculated, and the result is output to the pressure-holding flow analysis unit 12. The method of calculating the change behavior of pressure, temperature, and the like is the same as that of the conventional filling analysis, and thus a specific description is omitted here.

The pressure-holding flow analysis unit 12 performs a pressure-holding flow analysis based on the state quantity of the resin at the time of completion of the filling given from the filling analyzing unit 11. That is, the change behavior of the pressure, temperature, specific volume, and the like of the resin in the compensating flow process from the completion of the filling to the time when the compensating flow stops (gate seal) is calculated. The method of calculating the change behavior of the pressure, temperature, specific volume, and the like is the same as that of the conventional pressure-holding flow analysis, and a specific description thereof will be omitted.

When the compensating flow stops, the in-mold cooling analyzing section 13 executes the in-mold cooling analysis based on the state quantity of the resin at the time of the compensating flow stop obtained by the holding pressure flow analyzing section 12.
That is, the temperature distribution of each part of the molded article is calculated by the heat transfer between the mold and the molded article from the time when the compensation flow is stopped until the time when the mold is released. Then, the pressure is calculated based on the calculated temperature distribution data and the specific volume calculated by the pressure-holding flow analysis unit 12. At this time, when the pressure P becomes zero during the in-mold cooling analysis, the temperature data at that time is stored in the first storage unit 17. Further, the in-mold cooling analysis unit 13 performs calculations up to the time of release, and when there is a portion where the pressure P is not zero in each part of the molded product, the temperature data at the time of release is stored in the first storage unit 17. To be stored. In this case, calculation is performed until the pressure P of each part of the molded article becomes zero, and the time up to that point is stored in the first storage unit 17 as the optimal cooling time.

Thereafter, when the mold is released, the out-of-mold cooling analysis unit 14 calculates the heat transfer between the atmosphere and the molded product based on the temperature distribution data stored in the first storage unit 17. Calculate the temperature of the molded article at each time. This calculation is
Temperature of the entire molded article is carried out until the ambient temperature, each time
The calculation result of the temperature of each molded product is stored in the second storage unit 18.

The thermal stress / strain analysis unit 14 calculates the amount of deformation such as sink and warpage of the molded product due to thermal strain based on the temperature distribution data of the molded product at each time stored in the second storage unit 18. I do.

The output unit 16 creates a deformation diagram based on the amount of deformation such as sink marks and warpage obtained by the thermal stress / strain analysis unit 14, and displays this on a display unit such as a CRT.

FIGS. 4 and 5 show an example of a modified view when a thermal stress analysis is performed by the present method and apparatus. FIG. 4 is a diagram before deformation, and FIG. 5 is a diagram after deformation.

When comparing the two figures, the outer curved portion contracts,
Since the inner curved portion is expanded, the axes which should be orthogonal to each other are slightly opened (that is, 90 degrees + α). However, in the description here, the figure before deformation and the figure after deformation are separately shown, but by superimposing these figures on the display unit, it is possible to more clearly determine the deformed part. it can.

The deformation is examined by looking at the deformation diagram displayed on the display unit. If a defect is considered to occur, the condition of the input data to the filling analysis unit 11 is changed, and the same conditions as described above are performed. The calculation is performed and the deformed view is displayed again on the display unit.

[0036]

The molding process simulation method and apparatus according to the present invention calculate at least the temperature change, pressure and specific volume change of the molding material during the molding process, and determine the point at which each part of the molded product separates from the mold wall surface. Calculate and set the temperature distribution of the molded article at that time as the initial value, and calculate the heat transfer between the atmosphere and the molded article.
Until the temperature of the entire molded product reaches the atmospheric temperature.
Calculate the temperature distribution of the molded product for each hour, and calculate the temperature distribution for each hour.
The thermal stress strain at each time is calculated using the temperature distribution data of the molded product, and the shape change such as warpage or sink mark of the molded product is calculated from the deformation due to the thermal stress strain. It is possible to simulate even if the pressure of each part of the molded product is not completely atmospheric pressure due to insufficient cooling in the mold, and the original purpose of inappropriate molding conditions (cooling conditions) and under such conditions it can be properly predicted deformation amount due to thermal deformation strain. In addition, it is possible to evaluate the effects of molding conditions, mold structure and molded product shape on deformation such as sink marks and warpage before producing molds, and to appropriately determine various conditions such as mold shapes, product shapes, and molding conditions. Becomes possible. Further, various effects such as reduction of time and cost associated with correction of a mold shape and a product shape can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a molding process simulation apparatus to which a molding process simulation method of the present invention is applied.

FIG. 2 is a graph showing P- for explaining a conventional calculation method of shape distortion;
It is a vT curve figure.

FIG. 3 is a PvT curve diagram for explaining an inappropriate example of a conventional calculation method of shape distortion.

FIG. 4 is an example of a diagram before deformation in which thermal stress analysis is performed by the method and apparatus of the present invention.

FIG. 5 is an example of a diagram after deformation when a thermal stress analysis is performed by the method and apparatus of the present invention.

[Explanation of symbols]

 11 Filling analysis unit 12 Pressure flow analysis unit 13 In-mold cooling analysis unit 14 Out-of-mold cooling analysis unit 15 Thermal stress strain analysis unit

Claims (2)

(57) [Claims] In a molding process simulation for evaluating a mold structure, a molding condition, a molding material, etc., at least a temperature change, a pressure, and a specific volume change of a molding material during a molding process are calculated, and each part of the molded product is molded. Calculate the point of separation from the mold wall surface, set the temperature distribution of the molded article at that point as the initial value,
Calculation of the heat transfer between the molded product and
Calculate the temperature distribution of the molded product every hour until it reaches the atmospheric temperature
Then, using the temperature distribution data of the molded article for each time,
A molding process simulation method, comprising calculating a thermal stress strain for each and calculating a shape change such as warpage or sink of a molded product from deformation due to the thermal stress strain. 2. A pressure-holding flow analysis unit that calculates at least a temperature change, a pressure, and a specific volume change of a molding material during a molding process in a molding process simulation for evaluating a mold structure, molding conditions, molding material, and the like. Based on the pressure data calculated by the holding pressure flow analysis unit, calculate the time when each part of the molded product separates from the mold wall surface,
Initial and mold cooling analysis unit for determining the temperature distribution of the molded product at that time, the temperature distribution obtained by the in-mold cooling analysis unit
Value and calculate the heat transfer between the atmosphere and the molded product.
The temperature of the molded product every hour until the overall temperature reaches the atmospheric temperature
Cooling analysis unit that calculates the temperature distribution, and molding for each hour determined by the cooling analysis unit outside the mold
A thermal stress strain analysis unit that calculates thermal stress strain at each time using the temperature distribution data of the product, and calculates a shape change such as warpage or sink of a molded product from deformation due to the thermal stress strain. Characteristic molding process simulation device.