JPH08230007A - Method and device for simulation of injection molding process - Google Patents

Abstract

PURPOSE: To realize more exact estimate of temperature of resin, its pressure and its specific volume behavior by a method wherein the thermal behavior of a sprue runner part in a hot runner device is modelled as the more strict thermal boundary condition. CONSTITUTION: The shape models for a mold and of a molded article are divided so as to execute a numerical. analysis method including a finite element method, a boundary element method and a finite difference method in the step S1. The dividing method of resin, its heating method, the cooling capacity of cooling pipe and the like on a hot runner device used as defined in the step S2. On the basis of the defined information, boundary conditions on each infinitesimal element is set under the consideration of the difference between the heating systems in the step S3. For any infinitesimal element in the shape model of the molded article, a field of flow is calculated by use of equation of motion, equation of continuity and equation of energy in the step S4. In the flowing, dwelling and cooling process of resin to any infinitesimal element, pressure, temperature and specific volume are calculated momentarily in the step S5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding process simulation method and apparatus for dividing an injection molded product shape and a mold model into minute elements. The temperature of the thermoplastic resin in each injection molding process,
The present invention relates to a method and apparatus for predicting the transition of pressure and specific volume, and more accurately predicting the pressure required for filling, molding failure, and the amount of warpage deformation of a molded product obtained through the molding process.

[0002]

2. Description of the Related Art When simulating injection molding, thermal boundary conditions for considering heat transfer from a molding material to a mold are applied to each part of the modeled sprue, runner and molded product model. Give to Under the conditions, the pressure required for filling, the position of weld line generation, and the prediction of warp deformation are generally performed.

Conventionally, as a method of defining the boundary conditions of the simulation, a mold surface temperature is arbitrarily set, a constant heat transfer amount (heat flux), and a proportional constant (a constant value indicating the amount of heat that moves steadily). Methods such as thermal conductivity have been used. These are typical basic forms of heat conduction.

That is, after the molten molding material is filled in the cavity of the mold, the filling is completed,
Heat transfer until it is sufficiently cooled and removed from the mold (i.e., from the molding material to the mold, the refrigerant flowing through the cooling pipe,
From the outer surface of the mold to the atmosphere, etc.), the basic form of the above-mentioned typical heat conduction was elaborately expressed and given as a boundary condition.

Particularly, when a hot runner device is used in the working die, the temperature around the melting point of the molding material is controlled around the sprue and runner portions. Therefore, the device becomes complicated and the device types are various. Therefore, to set more accurate boundary conditions, for each type,
In addition, it was necessary to devise the definition of the boundary conditions in consideration of the complicated device configuration.

[0006]

However, since the heat transfer from the molding material to the mold cannot be steadily regulated, the thermal behavior is strictly expressed only by the basic form of heat conduction as described above. It was difficult. Especially in the case of a mold using a hot runner device, it is very difficult to accurately represent the different thermal behavior for each device type,
There is a possibility that individual differences among simulation operators may appear in the setting of boundary conditions.

Therefore, in a mold using a hot runner device, how to accurately represent the heat transfer from the molding material to the mold as a thermal boundary condition of the injection molding processing simulation, Setting thermal boundary conditions that are not affected was an unsolved problem to obtain more accurate calculation results.

Therefore, in order to solve the above-mentioned problems, the object of the present invention is to model the thermal behavior of the sprue runner portion in a hot runner apparatus as a more strict thermal boundary condition, and to determine the temperature, pressure and specific volume of the resin. A method and an apparatus capable of predicting behavior more accurately.

[0009]

In order to achieve the above object, a method of simulating an injection molding process using a hot runner apparatus according to the present invention and a basic configuration of the apparatus, a mold structure of the injection molding process, and molding conditions. In the process simulation to evaluate the molding material,
Identifies the type of hot runner equipment specified in advance and determines the thermal behavior that differs depending on the equipment type.
It is expressed in a heat boundary condition in numerical calculation including heat transfer, heat flux regulation, etc., and a motion equation, continuity equation, and energy equation are calculated based on resin data and molding condition data at any point of the molded product shape model. The flow field is used to calculate the transition of pressure, temperature, and specific volume in the process of resin flow / holding / cooling to an arbitrary point.

[0010]

EXAMPLE A hot runner device is often used from the viewpoint of cost reduction of raw materials and protection of the global environment because waste materials of sprue and runner parts can be eliminated. The following three major functions are required for the device.

1) The sprue runner is always kept at a high temperature,
The molten resin must be able to flow from the runner into the cavity at least during the injection stroke.

2) The cavity has a sufficiently low temperature so that the resin is cooled and solidified during molding.

3) The gate, which is the boundary between the runner and the cavity, should be melted at the time of injection, but at the end of cooling, the runner and the cavity should be easily separated so that resin does not leak.

First, focusing on the third function, FIG. 1 shows a classification of general hot runner devices. In any of the four types in the figure, the resin is supplied to the cavity for each shot while being held in a molten state at a runner portion called a manifold. First, it is classified as follows according to the method of dividing the runner and the cavity.

"Heat Balance Method" In the type shown in FIGS. 2 and 3, cooling holes are arranged near the gate. After the filling is completed, the temperature of the resin around the cooling holes is lowered and slightly solidified, thereby facilitating the division of the resin between the cavity portion and the manifold portion. In other words, the function of 3) is fulfilled while keeping a thermal balance.

"Mechanical valve system" FIGS. 4 and 5,
In the type of FIG. 6, as a means for separating the resin in the cavity part and the manifold part after the completion of filling, the resin is not solidified thermally but the function of 3) is forcibly performed by a mechanical mechanism. Specifically, Fig. 4 shows an example in which the gate (manifold outlet) is blocked with a needle. Fig. 4 shows an example in which parting is provided between the cavity part and the manifold part to achieve resin separation when moving the mold. 5, shown in FIG.

Further, each type is classified by focusing on the function of 1) above.

"External Heating Method" First, in the types shown in FIGS. 2, 4, 5, and 6, the resin in the manifold is heated from the outer periphery thereof. Cartridge heaters, sheathed heaters, band heaters, heat pipes for heating, resin heating channels themselves as resistance heating elements, and heating with low voltage, and electromagnetic induction heating method There are things such as things, and they are used in many different ways.

"Internal heating system" On the other hand, in the type shown in FIG. 3, the torpedo itself provided inside the manifold serves as a heating body to heat the resin.

Based on the above, attached FIGS.
An embodiment to which the present invention is applied will be described with reference to FIG.

FIG. 7 is a block diagram showing the simulation processing of the injection molding process.

First, in S1, the die and molded product shape model is divided into minute elements so that a numerical analysis method including a finite element method, a boundary element method and a difference method can be performed.

Next, in S2, information on the hot runner device to be used, that is, the resin cutting method, heating method, heating capacity of the heating element and position / layout inside the mold, cooling capacity of the cooling pipe, and its position. / Define the layout and thermal property values of the mold material. Of course, here, the heat generation capacity of the heating element, the thermal property value of the mold material, the manifold,
It is also possible to prepare a series of thermal data by unitizing the nozzle part, cooling pipe, etc., and make it a database in advance, and quote it as necessary.

Then, in S3, considering the difference in the heating method from the information on the defined hot runner device,
Boundary conditions for each minute element are set as follows.

(In the case of the external heating method) It is assumed that the heating element is present at a position distant from the resin flow path, and a material having a sufficiently high thermal conductivity (a material which is not a so-called heat insulating material) is present between them. . Here, information such as the heating ability of the heating element, the heating program, the distance between the heating element and the flow path of the resin, and the heat conduction / transfer ability of the mold material is input. From these pieces of information, the boundary condition at the boundary position at an arbitrary position of the resin flow path is set according to the following procedure.

First, for the transfer of heat from the heating element to the material existing between the heating element and the resin flow path, one of a predetermined temperature value, a heat flux value and a heat transfer coefficient is specified depending on the type of the device.
In particular, the heat flux value can be arbitrarily changed over time, or can be arbitrarily changed by feedback control from a temperature sensor placed at an arbitrary position.
In reality, the thermal behavior is not uniform on all the heating surfaces of one heating body, but the distribution state can be specified and the conditions can be set depending on the manufacturer and type of the device.

Next, the transfer of heat in the material between the heating element and the resin flow path determines the thermal conductivity according to the material.

The heat transfer from the material between the heating element and the resin flow path to the resin in the resin flow path specifies the heat transfer coefficient according to the material.

(In the case of the internal heating method) It is assumed that a heating body exists in the central portion of the resin flow path and heat is directly transferred from the heating body to the resin flow path. Here, information regarding the heating capacity of the heating element and the heating program is input. From these pieces of information, the boundary condition at any position of the resin flow path is set.

For the transfer of heat from the heating element to the resin flow path, any one of the temperature regulation value, the heat flux value and the heat transfer coefficient is specified depending on the type of the device. In particular, the heat flux value can be arbitrarily changed over time, or can be arbitrarily changed by feedback control from a temperature sensor placed at an arbitrary position. In reality, the thermal behavior is not uniform on all the heating surfaces of one heating body, but the distribution state can be specified and the conditions can be set depending on the manufacturer and type of the device.

When a water pipe is arranged near the gate or near the cavity (whether the "heat balance system" or the "mechanical valve system"), heat is not transferred from the resin in the vicinity to the water pipe. Shall happen. The boundary conditions are the cross-sectional shape / dimension of the water pipe, the type / flow rate of the refrigerant,
Either the heat flux value or the heat transfer coefficient is set in consideration of the thermal physical properties of the material between the water pipe and the resin flow path.

Next, in S4, a flow field is obtained for an arbitrary minute element of the molded product shape model by using a motion equation, a continuity equation, and an energy equation based on the defined resin data and molding condition data.

Then, in step S5, the pressure, temperature, and specific volume are calculated in the process of flowing, holding pressure, and cooling the resin to an arbitrary minute element.

FIG. 9 is a block diagram showing the configuration of an injection molding process simulation apparatus as an embodiment of the present invention.

In FIG. 9, reference numeral 21 denotes a shape modeling preparation device, which divides a mold and a molded product shape model into minute elements so that a numerical analysis method including a finite element method, a boundary element method and a difference method can be performed. Input resin data and molding condition data used for calculation. Then, the data created here is sent to the shape modeling data storage device 31.

Reference numeral 22 is an information input device relating to the hot runner device, which is information relating to the hot runner device to be used,
That is, the resin cutting method, the heating method, the heating capacity of the heating element, the position / layout inside the mold, the cooling capacity of the cooling pipe, and its position / layout, and the thermal property value of the mold material are input. The data is sent to the information data storage device 32 regarding the hot runner device.

23 is a thermal boundary condition data calculation device,
From the information about the hot runner device stored in 32, the difference in the heating method in each microelement is judged,
Set thermal boundary conditions. Then, the data is sent to the thermal boundary condition data storage device 33.

Reference numeral 24 is a flow field calculation device, and based on the shape modeling data stored in 31 and the thermal boundary condition data stored in 33, a motion equation for an arbitrary minute element of the molded product shape model, The flow field is calculated using the continuity and energy equations. Then, the flow field obtained here is sent to the calculation result data storage device 34.

Reference numeral 25 is a pressure, temperature, and specific volume calculation device, and based on the data of the calculation result of the flow field stored in 34, the pressure of the flow of resin to any minute element, the holding pressure, and the momentary pressure in the cooling process. , Temperature and specific volume are calculated, and the data are sent to the pressure, temperature and specific volume data storage device 35.

Reference numeral 26 is a display device which graphically displays the simulation result.

The present invention may be applied to a system including a plurality of devices or an apparatus including a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

EFFECTS OF THE INVENTION According to the present invention, a flow field can be obtained by using a motion equation, a continuity equation, and an energy equation based on resin data and molding condition data for an arbitrary point of an injection molded product shape model. When calculating the transition of pressure, temperature, and specific volume in the process of resin flow / holding / cooling to an arbitrary point, the thermal behavior of the hot runner device used is specified as the temperature regulation at the arbitrary point of the sprue runner part. ,
By replacing with heat boundary conditions such as heat transfer and heat flow velocity regulation, it is possible to calculate more accurate thermal behavior during resin flow / holding / cooling of sprue runner due to the difference in hot runner equipment type. Therefore, it becomes possible to more accurately predict the temperature, pressure, and specific volume of the resin of the entire molded product.

From this, the following three specific effects can be expected. (1) Since it is possible to more accurately predict changes in the pressure distribution inside the molded product during the injection molding process, it is possible to predict the pressure (maximum pressure) required for filling and the mold clamping force, which is optimal and necessary. It is possible to select an injection molding machine with sufficient output. Therefore, it becomes possible to suppress the molding equipment investment, which accounts for a part of the cost of the molded product, to the lowest cost. (2) It becomes possible to more accurately predict changes in the temperature distribution in the molded product during the injection molding process, and it is possible to predict the cooling time to the solidification temperature of the resin, that is, the cooling time in the mold, and the molding cycle time. Can be specified. Therefore, it is possible to pursue the shortest molding cycle time by changing the molding conditions or the mold design and repeating the calculation, so that the cost of the molded product can be suppressed to the lowest. (3) Since it is possible to more accurately predict changes in the specific volume distribution within the molded product during the injection molding process, the final molded product size and the amount of warp deformation can be predicted by discretizing the entire molded product. Is possible. Therefore, by repeating the simulation while changing the molding conditions and the mold design, it is possible to realize a molded product with the smallest warp deformation, a higher accuracy and a narrow required accuracy range in a short time.

[0043]

[Brief description of drawings]

FIG. 1 is a classification diagram of a general hot runner device.

[Fig. 2] Example of hot nozzle type hot runner device

[Fig. 3] Example of a torpedo type hot runner device

[Fig. 4] Example of needle valve type hot runner device

FIG. 5: Slide valve type hot runner device example (closed state)

FIG. 6 Example of slide valve type hot runner device (open state)

FIG. 7 is a block diagram showing a simulation process of an injection molding process as an example of the present invention.

FIG. 8 is an example of a model diagram in which a mold and a molded product shape model are divided into minute elements.

FIG. 9 is a block diagram showing a configuration of a simulation device of an injection molding process.

[Explanation of symbols]

 1 Cavity 2 Runner 3 Gate 4 Parting line 5 Needle 6 Cooling hole 7 Manifold 8 Hot nozzle 9 Valve gate 10 Torpedo 11 Torpedo heater S1 Analysis model input step S2 Hot runner information input step S3 Flow field calculation step S4 Thermal boundary condition calculation Step S5 Resin pressure, temperature, specific volume calculation Step 21 Shape modeling creation device 22 Information input device for hot runner device 23 Thermal boundary condition data calculation device 24 Flow field calculation device 25 Pressure, temperature, specific volume calculation device 26 Display device 31 Shape modeling data storage device 32 Information data storage device for hot runner device 33 Thermal boundary condition data storage device 34 Flow field calculation result data storage device 35 Pressure, temperature, specific volume data storage device

Claims (7)

[Claims] 1. At an arbitrary point of a shape model of an injection-molded product, pressure, temperature in a process of flow, holding pressure and cooling of resin,
In the method of simulating the transition of the specific volume, by identifying the type of hot runner device used and specifying the thermal behavior of the sprue runner, it is expressed in the thermal boundary condition of the sprue runner, and the expressed thermal boundary A method for simulating an injection molding process, characterized by performing simulation using conditions. 2. The simulation method according to claim 1, wherein the thermal boundary condition is expressed by numerical calculation including temperature regulation, heat transfer, heat flux regulation and the like. 3. The simulation method according to claim 1, wherein the flow field is calculated based on resin data and molding condition data by using a motion equation, a continuity equation, and an energy equation. 4. The pressure, temperature, flow rate, holding pressure, and cooling process of the resin at any point of the injection molded product shape model,
A device for simulating the transition of specific volume is characterized by having means for inputting the type of hot runner device to be used and means for predicting thermal behavior by calculating the thermal boundary conditions of the sprue runner part. Injection molding process simulation device. 5. The simulation apparatus according to claim 4, wherein the thermal boundary condition is obtained by a numerical calculation means including temperature regulation, heat transfer, heat flux regulation and the like. 6. A means for calculating the flow field from a motion equation, a continuity equation and an energy equation based on resin data and molding condition data.
Simulation device described 7. The simulation result is graphically displayed on a display device.
Simulation device described