JP2002292707A - Method for estimating warp deformation of resin injection-molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a development period and reduce production preparing man-hours, mold correction man-hours and cost by enhancing estimation accu racy by allowing the warpage based on an analytical estimated value to coincide with the warpage of an actual molded product. SOLUTION: In the method for estimating the warpage of the resin injection- molded product by analyzing the injection molding of the box-shaped resin injection-molded product having an opening part and corner parts, the analysis of injection molding is performed on the basis of a model for analyzing injection molding formed by applying the coefficient of heat-transfer to the upper surface and back surface of each of the corner parts to estimate the warp quantity of the opening part.

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 warpage deformation of a resin injection-molded article, which performs injection molding analysis of a resin injection-molded article having a corner portion, and predicts and evaluates the amount of warpage.

[0002]

2. Description of the Related Art A conventional method for predicting warpage deformation of a resin injection molded product is to perform injection molding analysis of a resin injection molded product and predict and evaluate the amount of warpage.

That is, the conventional method for predicting the warpage of a resin injection molded article is based on a general injection molding analysis as shown in FIG. 15. For example, the injection molding analysis of a resin injection molded article having a corner portion is started. If done, step 10
In step 1, the shape of a resin injection molded product having a corner portion is input and divided into meshes, that is, the product portion is divided into shell elements, and an injection molding analysis model is created.

[0004] In step 102, injection molding analysis such as analysis of filling, dwelling and cooling processes and warpage analysis are performed. In step 103, the difference between the reference drawing shape and the predicted molded product shape after molding is determined. That is, the warpage is evaluated.

In step 104, it is determined whether or not the obtained warpage problem exists.
In 5, the analysis model such as the change of the molding conditions such as the holding pressure and the cooling time, the change of the product thickness, the addition of the rib, and the like are changed, and the above-described injection molding analysis of step 102 is performed again.

[0006]

According to the analysis in the conventional method for predicting warpage deformation of a resin injection molded article, the shell element is analyzed with the same area on the front and back surfaces even at the corners of the molded article. In fact, they have different thermal behavior.

That is, since the material is cooled by passing a medium such as water or oil through the cooling pipe in the mold, the exchange of heat with the mold will be different if the area is different. In the conventional analysis, since the analysis is performed on the assumption that the area of the front surface and the back surface of the shell element is the same, the difference in the amount of shrinkage between the front surface and the back surface is naturally estimated to be small. Since the warpage based on the predicted value and the warpage of the actual molded product do not match, the slope and absolute value differ greatly, the prediction accuracy is low, the development period is prolonged,
There has been a problem that the number of man-hours for production preparation, man-hours for correcting molds, and costs increase.

Accordingly, the present inventor has performed a method for predicting warpage deformation of a resin injection molded product, which performs injection molding analysis of a resin injection molded product having a corner portion and predicts and evaluates the amount of warpage. By using different heat transfer coefficients on the back side and performing injection molding analysis based on the created injection molding analysis model, the technical idea of the present invention that the amount of warpage is predicted, and further research and development As a result of the overlap, the warpage based on the analysis prediction value is matched with the warpage of the actual molded product, the prediction accuracy is improved, the development period is shortened, the production preparation man-hour, the mold repair man-hour and the cost are reduced. The present invention has been reached.

[0009]

According to a first aspect of the present invention, there is provided a method for predicting warpage of a resin injection-molded article.
Injection analysis of a resin injection molded product having a corner portion is performed, and in a method of predicting warpage of a resin injection molded product in which a warpage amount is predicted and evaluated, different heat transfer coefficients are used for the front surface and the back surface of the corner portion. Then, by performing injection molding analysis based on the created injection molding analysis model, the amount of warpage is predicted.

In the method for predicting warpage of a resin injection molded article according to the present invention (the second invention according to claim 2), in the first invention, an evaluation is performed based on the predicted warpage amount, and the prediction is performed. If there is a problem in the warpage amount, the molding conditions are changed and the injection molding analysis model is changed.

According to a third aspect of the present invention, there is provided a method for predicting warpage of a resin injection-molded article according to the second aspect of the present invention, wherein the corner has a contact area with a mold. The injection molding analysis is performed and the amount of warpage is predicted.

According to a fourth aspect of the present invention, in the method for predicting warpage of a resin injection-molded article according to the third aspect, a model for thermal stress analysis is created, and the inner warpage evaluating unit is two-dimensional. It is divided into cross-sectional meshes, subjected to thermal stress analysis, evaluated for internal warpage, and taken into account in determining whether there is a problem with the amount of warpage.

According to a fifth aspect of the present invention, there is provided the method for predicting warpage of a resin injection-molded article according to the fourth aspect of the present invention, wherein the injection molding analysis result based on the injection molding analysis model is converted into the thermal analysis result. This is converted into input conditions for stress analysis.

According to a sixth aspect of the present invention, there is provided the method for predicting warpage of a resin injection-molded article according to the fifth aspect, wherein the input conditions for the thermal stress analysis are a resin temperature and a mold temperature. There is something.

According to a seventh aspect of the present invention, there is provided a method for predicting warpage of a resin injection molded article according to the sixth aspect, wherein a heat transfer coefficient is locally determined as an input condition for the thermal stress analysis. To change.

[0016]

According to the first aspect of the present invention, there is provided a method for predicting warpage of a resin injection-molded article having the above-described structure, in which an injection-molding analysis of a resin injection-molded article having a corner portion is performed, and a warpage amount is estimated and evaluated. In the method for predicting warpage deformation of a resin injection molded product, the amount of warpage is predicted by performing injection molding analysis based on a created injection molding analysis model using different heat transfer coefficients for the front and back surfaces of the corner portion. Therefore, the warpage based on the analysis prediction value is matched with the warpage of the actual molded product, and the effect of increasing the prediction accuracy is achieved.

According to the second aspect of the present invention, there is provided a method for predicting warpage deformation of a resin injection-molded article according to the first invention, wherein the evaluation is performed based on the predicted warpage amount, and there is no problem with the predicted warpage amount. If there is, the molding conditions are changed and the injection molding analysis model is changed, so that the effects of shortening the development period, reducing the number of man-hours for production preparation, the number of man-hours for correcting the mold, and reducing the cost are achieved.

According to the third aspect of the present invention, there is provided a method for predicting warpage of a resin injection molded article according to the second aspect, wherein the injection molding analysis is performed in consideration of a contact area of the corner portion with a mold. Since the amount of warpage is predicted, there is an effect that prediction accuracy is improved.

According to the fourth aspect of the present invention, there is provided a method for predicting warpage deformation of a resin injection molded article according to the third invention, wherein a model for thermal stress analysis is created, and an inner warpage evaluation unit is divided into a two-dimensional cross-section mesh to obtain a thermal stress. Stress analysis is performed, the internal warpage is evaluated, and it is added to the determination of whether there is a problem with the amount of warpage, so the prediction accuracy is further improved, and the warpage based on the analysis predicted value matches the actual molded product warpage. It works.

According to a fifth aspect of the present invention, there is provided a method for predicting warpage of a resin injection molded article according to the fourth aspect, wherein an injection molding analysis result based on the injection molding analysis model is used as an input condition for the thermal stress analysis. Since the conversion is performed, a synergistic effect of the injection molding analysis and the thermal stress analysis has an effect of further increasing the prediction accuracy.

According to the sixth aspect of the present invention, there is provided a method for predicting warpage of a resin injection molded article, wherein the resin temperature and the mold temperature are converted as input conditions for the thermal stress analysis. This has the effect of enabling prediction according to the resin temperature and the mold temperature.

In the method for predicting warpage of a resin injection molded article according to the seventh aspect of the present invention, the heat transfer coefficient is locally changed as an input condition for the thermal stress analysis in the sixth aspect. This makes it possible to make predictions in consideration of the temperature difference between the respective parts of the resin injection molded article.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings.

(First Embodiment) The method for predicting warpage of a resin injection molded article according to the first embodiment is a box-shaped resin having an opening 11 and a corner 12 as shown in FIGS. In a method of predicting warpage deformation of a resin injection molded product by performing injection molding analysis of the injection molded product 1 and predicting and evaluating the amount of warpage, the method is performed by using different heat transfer coefficients for the front surface and the back surface of the corner portion 12. The amount of warpage of the opening 11 is predicted by performing the injection molding analysis based on the injection molding analysis model thus obtained.

That is, the method for predicting the warpage of the resin injection molded article of the first embodiment is based on a general injection molding analysis. For example, the injection molding of the resin injection molded article 1 having the opening 11 and the corner 12 is performed. Analysis starts.

In step 101, as shown in FIG. 2, for example, a box-like shape of an engine cover of the resin injection molded product 1 having an opening 11 and a corner 12 on each side is input and divided into meshes. It is divided into shell elements, and an injection molding analysis model, molding conditions and resin properties are input as input information, and an injection molding analysis model is created.

FIG. 2 shows an injection-molding analysis model created by dividing the resin injection-molded article 1 as a product part, which is connected to the beam element cooling pipe 2 and the beam element runner 3 in step 101, into shell elements. It is shown.

In general, in flow analysis such as injection molding (the same applies to structural analysis), as shown in FIG. 2 and FIG. And each shell element is analyzed as one unit.

The mesh size of the corner portion in the first embodiment will be described below. The mesh size of the corner portion is the same size as other portions such as the side wall and the bottom surface, and is not particularly fine. The reason is that, if the mesh size is reduced, the man-hours for creating the mesh are also required, and the analysis takes time. Therefore, in the first embodiment, from the viewpoint of shortening the analysis man-hour and the analysis time, the same is used as an example. A mesh was used.

Of course, there is no doubt that the accuracy will be improved if the mesh size is reduced. The case where the mesh is made fine is a case where the shape is expressed in detail or a change in the physical quantity is large.

As an example of expressing the shape in detail, when an attempt is made to create a mesh of a stepped product at a pitch of 10 mm, if the step is less than 10 mm, the stepped portion will be 10 mm.
Since a mesh cannot be created, a fine mesh is created.

As an example of a large change in the physical quantity, a fine mesh is created in the vicinity of the opening of the gate of the mold cavity because the cross-sectional area changes greatly and the flow pressure of the resin changes greatly.

When it is necessary to analyze the change in the stress or the temperature of the corner with a large change, the mesh size of the corner must be reduced.

In step 201, the heat transfer coefficients at the corners of the four sides are changed. Change the heat transfer coefficient on the front and back of the corner element. That is, the heat transfer coefficient on the front side is set to be smaller than that on the back side, so that the inner heat reservoir is evaluated to be larger.

Regarding the change of the heat transfer coefficient at the corner,
This will be described in more detail. At the corners, instead of the actual area, the original heat transfer coefficient is the same for the front and back surfaces, but the heat transfer coefficient (h) is different for the front and back surfaces for analysis. For example, if the thickness is 2 mm and the fillet radius is 5 mm, the inner diameter is 3 mm, the area ratio between the front surface and the back surface is 5: 3, and the heat transfer coefficient is 3: 5 in order to match the heat balance with the actual product. .

Since the amount of shrinkage of the resin can be calculated from the exchange of heat with the mold, the amount of heat (w) that moves can be calculated as follows:
The heat transfer coefficient (w / m ² · K), the difference between the mold temperature Tc (K), and the difference (K) between the resin temperature Tr (K) and the area (m ² ) are expressed by the following formula 1. You.

(Equation 1) q: the amount of heat transferred (w), h: the heat transfer coefficient (w / m ² ·
K), S: area (m ² ), T: temperature (K) That is, the difference in the area of the front and back surfaces, which is actually different, is replaced by a heat transfer coefficient to determine the amount of heat transfer between the front and back molds. The analysis is made differently.

In step 102, the injection molding analysis such as the analysis of the filling, the holding pressure, the cooling process and the warpage analysis is performed. The injection molding analysis is based on MODDFLOW (MODDF
According to flow analysis software such as LOW Co., Ltd., the volume change or shrinkage in the process of solidification from the molten state is calculated for each mesh, and at that time, sink marks and other quantities are calculated so that the meshes are connected, and the distortion generated at that time The mold cooling analysis and the filling pressure-holding cooling analysis are performed by a procedure such as calculating the residual stress from the data. Japanese Patent Application Laid-Open No. 11-138610 also discloses an analysis according to flow analysis software.

In the above-mentioned MODFLOW, the resin material is analyzed as a fluid, that is, a flow pressure of the resin.
In the detailed shape described later, that is, in the cross-sectional direction, an enormous capacity is required for analysis, and analysis is not possible.

In MODFLLOW, the factors to be considered are temperature, pressure (pressure of resin flow),
The shape (detailed shape of the front and back areas), the mold temperature distribution, and the like are taken into consideration.

That is, the contents of the injection molding analysis include the filling behavior of the resin material into the cavity, that is, when the resin is injected into the cavity, the temperature and the pressure of the resin flowing while cooling on the mold surface are reduced. The shape, that is, high in the narrow part, low in the wide part, and because it flows while being cooled, the pressure of the resin taking into account the increase in pressure due to cooling, the mold is the hot water in the temperature control piping embedded in it and The temperature is controlled by a medium such as oil, but of course the temperature differs between the place where the piping is arranged and the place where the piping is not arranged. In addition to the resin pressure and cooling, the resin temperature, and the mold temperature distribution, as well as the resin pressure to compensate for the volumetric shrinkage due to shrinkage during cooling and solidification of the resin, the resin pressure is used. It is carried out.

The injection molding analysis in the step 102 is to analyze the behavior of the injected material by inputting various conditions relating to the injection molding to the shell element prepared in the first step.

The input conditions include a material temperature, a filling time, an injection pressure, and a dwelling time (the material is filled into a cavity, which is a portion to be filled with a molding material molded using a pair of opposing dies). After molding, the injection pressure must be maintained even when cooling the molded product in order to reduce sink marks due to molding shrinkage), and the material properties such as cooling time, density, specific heat, thermal conductivity, viscosity, etc. Equivalent to.

The output corresponds to the behavior of the material at the time of filling the cavity, the warpage of the molded product, sink marks, and the like. The difference in temperature between the outer mold and the middle mold is fed back to the boundary condition, and the difference in pressure is fed back to physical properties (linear expansion coefficient).

In step 103, the difference between the reference drawing shape and the predicted molded product shape after molding, that is, the warpage is evaluated.

In step 103, the warpage amount of an actual molded product is measured and predicted based on the results in steps 101 and 102. That is, the temperature of the middle mold inside the corner of the resin injection molded article and the temperature of the outer mold outside the opening of the box-shaped resin injection molded article close to the inner warpage evaluation section are arranged at a distance of 2 mm from the product section. The detected sensor detects the temperature.

In step 104, the presence or absence of a warpage problem is determined from the obtained warpage amount. If there is a problem, that is, if the warpage amount is larger than a predetermined value (target value), in step 105, the holding pressure and the cooling time The analysis model such as the change of the molding condition such as the change of the product thickness, the addition of the rib, etc. is changed, and the above-described injection molding analysis of step 102 is performed again.

The method for predicting the warpage of a resin injection molded article according to the first embodiment is based on an injection molding analysis prepared by using different heat transfer coefficients for the front and back surfaces of the corner portion 12 of the resin injection molded article 1. Since the amount of warpage is predicted by performing the injection molding analysis based on the use model, the warpage based on the analysis predicted value is approximated to the measured warpage of the actual molded product, and the effect of increasing the prediction accuracy is exerted. .

In the method for predicting warpage of a resin injection-molded article according to the first embodiment, an evaluation is performed based on the predicted warpage amount. If there is a problem with the predicted warpage amount, the molding conditions are changed. Since the model for injection molding analysis is changed together with the change, the effects of shortening the development period, man-hours for production preparation, man-hours for correcting the mold, and cost can be achieved.

(Second Embodiment) As shown in FIGS. 4 and 5, the method for predicting warpage of a resin injection molded product according to the second embodiment differs between the front surface and the back surface of the corner portion in the first embodiment. The difference from the first embodiment is that the temperature calculation in the injection molding analysis is performed on the assumption that the area of the front surface and the back surface is different for the element of the corner portion instead of performing the injection molding analysis using the heat transfer coefficient. The following description will focus on the differences.

As shown in the flow chart shown in FIG. 4, the injection molding analysis is performed on the assumption that the contact area between the front surface and the back surface of the die differs at the corner. That is, only the mesh at the corner is regarded as a part of the cylinder, and the calculation is performed by changing the heat transfer so that the front and back areas are different. In this case, although the area of the front and back can be changed, it is not possible to cope with a complicated cross section as described later.

In the second embodiment, the corner portion is regarded as a cylinder, and for example, the temperature at a position having a coordinate r from the center after a predetermined time (t) has elapsed is calculated.

In the case of a flat plate, what is analyzed according to the following equation 2 is analyzed according to the following equation 3 in which elements other than the flat plate are newly added.

(Equation 2)

(Equation 3) In Equations 2 and 3, ρ: density, Cp: specific heat, T: temperature, t: time, k: thermal conductivity, and r: coordinates.

The wall thickness of the triangular shell element used in the injection molding analysis appears to be zero as shown in FIG. 5B, but is internally shown in FIG. 5C. In the cross section of the corner part (shell element), the inner part of the shell element must be used for the analysis of a flat plate, despite the fact that the surface area of the front and back surfaces is different. Since the triangles on the front and back surfaces shown in FIG. 5A used in the analysis have the same shape and the same area, the analysis is performed on the assumption that the front and back surfaces have the same surface area. Could not be obtained.

Therefore, in the corner section (shell element), as shown in FIG. 5D, the corner is assumed to have different surface areas on the front surface and the back surface, and a calculation function is added to improve the analysis accuracy. It is.

In the method for predicting the warpage of a resin injection-molded product according to the second embodiment, the injection molding analysis is performed and the amount of warpage is predicted in consideration of the contact area of the corner portion 12 with the mold. This has the effect of increasing the prediction accuracy as compared with the conventional case.

(Third Embodiment) As shown in FIGS. 5 and 6, the method for predicting the warpage of a resin injection-molded article according to the third embodiment is not only the same as the injection molding analysis of the above-described embodiment, but also The point of performing the stress analysis is the difference from the above-described embodiment, and the following description will focus on the difference.

In the analysis in the third embodiment, a model for the injection molding analysis (FIG. 5A) for dividing the product part into the above-described shell elements and a thermal stress analysis for the secondary cross-section mesh of the inner warpage evaluation unit. (D) of FIG. 5 is prepared, and in addition to the injection molding analysis of the flow of the central part in steps 101 to 104 of the flowchart in FIG. 6, steps 301 to 3 in FIG.
The thermal stress analysis is performed by using the structural analysis software capable of performing the stress analysis in the left flow of the flowchart of FIG.

In the thermal stress analysis according to the third embodiment, the software used for performing the thermal stress analysis is ABAQUS (HKS), which cannot be analyzed in a fluid state. The thermal stress analysis is performed by taking into account a part of the temperature and shape of the resin (the detailed shape (cross-sectional direction) of the front and back areas and the temperature distribution of the mold).

In the ABAQUS analysis, the temperature of the resin is cooling by exchanging heat with the mold surface.
Naturally, this is an operation performed even in the fluid state in the above-described MODFLLOW. Here, the temperature distribution of the mold takes into account the temperature of the front and back of the product, but the above MOLD
It is not possible to take into account the temperature distribution depending on the location of the mold performed in FLOW. JP-A-10-278
088 also shows an analysis according to the thermal stress analysis software.

In ABAQUS analysis, a resin material cannot be analyzed as a fluid, but an analysis in a detailed shape (sectional direction) is possible.

In the third embodiment, injection molding analysis is performed to evaluate the overall warpage. The inner warpage is evaluated using a cross-sectional model of a portion to be evaluated as shown in FIG.

In the evaluation of the warpage in step 304, in step 302, the resin temperature and the mold temperature obtained by the injection molding analysis are converted into those for the cross-sectional model, and the heat conduction analysis is performed. The temperature field due to the difference in the contact area between the product front and back molds is calculated, and based on the data, a thermal stress analysis is performed in step 303.

In the method for predicting warpage of a resin injection-molded article according to the third embodiment, a model for thermal stress analysis is created, the inner warpage evaluation section is divided into a two-dimensional cross-section mesh, and thermal stress analysis is performed. Is evaluated and added to the determination of whether there is a problem with the amount of warpage, so that there is an effect that the prediction accuracy is further improved, and the warpage based on the analysis predicted value matches the actual warpage of the molded article.

In the method for predicting warpage of a resin injection molded article according to the third embodiment, the result of the injection molding analysis based on the model for the injection molding analysis is converted into the input condition for the thermal stress analysis. The synergistic effect of the analysis and the thermal stress analysis has the effect of further increasing the prediction accuracy.

Further, in the method for predicting warpage of a resin injection-molded article according to the third embodiment, the resin temperature and the mold temperature are converted as input conditions for the thermal stress analysis. This makes it possible to make predictions according to the conditions.

In the injection molding analysis in the above-described embodiment, only the exchange of heat (temperature) between the injected material and the mold can be analyzed. However, in the third embodiment, the injection molding analysis and the thermal stress analysis are performed as described above. Since the analysis is performed in combination, the absolute value is different for the mold material as shown in FIG. 7, but the inclination is the same and the same as the actual value measured by the three-dimensional measuring device. This indicates the tendency, and the prediction error is suppressed to about 1.5 mm.

When the corner portion 12 of the resin molded product 1 has a uniform thickness, the front side is cooled and solidified first, and the back side is cooled later. Is deformed inward, so that FIG.
The cross-sectional shape is as shown in FIG. The shape shown in FIG. 5 (E) is a cross-sectional shape as shown in FIG. 5 (F) because the die is pulled out undercut, a slide core is required, and the die becomes complicated. Is set to

In the third embodiment, the calculation is performed using ABAQUS for the resin filled in the cavity. In this case, since a plurality of meshes can be created in the cross-sectional direction, complicated shapes can be handled. However, in this case, the heat transfer coefficient was not changed.

(Fourth Embodiment) As shown in FIG. 8, the method for predicting the warpage of a resin injection molded article according to the fourth embodiment differs from the actually measured value in the third embodiment in the absolute value. The difference from the third embodiment is that the heat transfer coefficient (h) at the corner portion, which is performed in the first embodiment described above, is locally varied between the front surface and the back surface in order to make correction. The following description focuses on the differences.

That is, an injection molding analysis is performed to evaluate the overall warpage. Evaluate the inner warpage using the cross-sectional model of the part to be evaluated. At the time of the internal warpage evaluation, the heat transfer coefficient of the corner portion is locally changed in the heat conduction analysis to improve the accuracy of the internal warp prediction.

In the fourth embodiment, when it is difficult to predict how much the front and rear heat transfer coefficients (h) and the rear heat transfer coefficient (h) should match to match the absolute value, various attempts are made to match. The value will be determined in advance.

The method for predicting warpage of a resin injection-molded article according to the fourth embodiment, in addition to the effects of the third embodiment, locally changes the heat transfer coefficient as an input condition for the thermal stress analysis. Therefore, there is an effect that prediction can be performed in consideration of a temperature difference between respective parts of the resin injection molded article at the time of molding.

In other words, in the method for predicting warpage of a resin injection molded article according to the fourth embodiment, as shown in FIGS. The absolute value and the inclination are almost the same, and the predicted value of the inner warpage amount is 0.7 mm against the actually measured value of the inner warpage amount of 1.0 mm. And the prediction accuracy of the inner warpage can be remarkably improved.

In the warpage deformation prediction method according to the fourth embodiment, an evaluation is performed based on the predicted warpage amount. If there is a problem with the predicted warpage amount, the molding conditions are changed and the warpage is changed. Since the injection molding analysis model is changed, the effects of shortening the development period, reducing the number of man-hours for production preparation, man-hours for correcting the mold, and reducing the cost are achieved.

That is, in the design stage, in order to predict the above-mentioned inner warpage amount and take a countermeasure, in order to minimize the temperature difference between the outer die and the middle die, the mold cooling pipe 2 shown in FIG. It is possible to optimize the product thickness of the resin injection-molded article 1, that is, to locally reduce the thickness by locally forming a thin portion, to locally adopt a high thermal conductivity material and to change or deform the mold material. This allows for optimized mold design and cooling pipe efficiency.

[0076]

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

(Embodiment) A method for predicting the warpage of a resin injection molded article according to this embodiment, which is a more specific example of the fourth embodiment described above, will be described with reference to FIGS.

A specific example of the resin injection-molded product 1 having the opening 11 and the corner 12 to be examined for predicting the warpage in the method for predicting the warpage of the resin-injection molded product of the present embodiment is as follows. As shown in FIG.
The approximate dimensions of the mm-box-shaped product part are 250 × 180 × 80 and the thickness t = 2, and the flow direction of the cooling water is also shown.

According to the recognition of the present inventor, the inner warpage of the resin injection molded article 1 is caused by the difference in the amount of heat radiation due to the difference in the surface area of the front and back surfaces of the corner portion 12 (factor 2), as shown in FIG. Has a large effect, and also has a correlation with the mold temperature difference (factor 1) of the injection molding analysis result.

That is, the warpage generation factors which are the basis of the concept of the warp prediction in the present inventor are shown in FIG.
1 will be described below. The cause of the warpage of the corner portion 12 of the resin injection molded article 1 is that the heat transfer to the mold is large because the outer mold is at a low temperature, and the heat transfer to the mold is small in the middle mold at a high temperature. A factor 1 caused by the difference between the mold temperature and the middle mold temperature is considered.

Next, since the surface area of the surface of the corner portion 12 of the resin injection-molded article 1 is larger than the surface area of the back surface, it is conceivable that Factor 2 is attributed to the difference in heat radiation due to the difference in surface area between the front surface and the back surface.

Further, it is conceivable that there is a factor 3 caused by the difference in pressure which causes the shrinkage of the heat reservoir (post-shrink portion) based on the difference in pressure inside the corner portion 12 of the resin injection-molded article 1.

The basic concept of the warpage prediction by the present inventor based on the recognition of the above-described warpage occurrence factor will be described below with reference to FIGS.

A temperature sensor is disposed on the middle mold inside the corner portion 12 of the resin injection-molded article 1 at a position of a distance of 2 mm from the product section, and the temperature sensor is located slightly inside from the opening end of the resin injection-molded article 1. The mold is disposed at a position at a distance of 2 mm from the product section, and the amount of internal warpage represents the distance between the outer wall forming the designed opening and the predicted outer wall after deformation.

As a consideration for the lack of accuracy of the predicted value with respect to the actually measured value, the resin injection molded product 1 shown in FIG.
Since the mold temperature in the analysis is the average temperature in one cycle in the stable molding,
Since the temperature difference between the outer mold and the middle mold is too smaller than the actual temperature difference, the temperature between the outer mold and the middle mold during molding decreases after a temperature peak occurs as shown in FIG. It is necessary to consider the actual temperature difference in the transition.

As a consideration for improving the quantitative prediction accuracy, in the cross section of the corner portion 12 of the resin injection-molded product 1 shown in FIG. The present inventor paid attention to changing the thermophysical properties in the thermal stress analysis because the analysis was impossible.

As a result, the distance X from the corner was determined as a parameter for determining the temperature rise of the middle corner.
And heat transfer coefficient h, X is 10 mm as an example of parameter optimization, and heat transfer coefficient h is 2500
[W / (m · K)]. The heat transfer coefficient h of the other parts is 25000 [W / (m · K)].

Accordingly, the present inventor has developed a prediction system capable of quantitatively predicting the amount of warpage within a prediction error of ± 1 mm by combining the injection molding analysis and the structural analysis as described above.

In the warpage deformation prediction method of this embodiment,
It is expected that the development period will be shortened by one month, production preparation man-hours will be reduced by 15 hours or more, and die repair costs will be reduced by hundreds of thousands or more.

The above-described embodiments and examples have been described by way of example only, and the present invention is not limited thereto. The present invention is not limited to the claims, the detailed description of the invention, and the drawings. Modifications and additions are possible without departing from the technical idea of the present invention that can be recognized by those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a chart showing an analysis procedure of a method for predicting warpage of a resin injection molded product according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing an analysis mesh, a cooling pipe, and a runner of a resin injection molded product of a product part in the first embodiment.

FIG. 3 is an enlarged perspective view showing an analysis mesh of another product part and a resin injection molded product of a runner in the first embodiment.

FIG. 4 is a chart showing an analysis procedure of a method for predicting warpage of a resin injection molded product according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining deformed shapes of shell elements and corner portions in the resin injection molded products of the second and third embodiments.

FIG. 6 is a chart showing an analysis procedure of a warpage deformation prediction method for a resin injection molded product according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a relationship between a predicted value and a measured value regarding a mold temperature difference and an amount of internal warpage in the warpage deformation prediction method according to the third embodiment.

FIG. 8 is a chart showing an analysis procedure of a method for predicting warpage of a resin injection molded product according to a fourth embodiment of the present invention.

FIG. 9 is a diagram showing a relationship between a predicted value and a measured value relating to a mold temperature difference and an amount of internal warpage in the warpage deformation prediction method of the fourth embodiment.

FIG. 10 is an explanatory diagram for explaining a relationship between a predicted value and an actually measured value regarding the amount of warpage in the warpage deformation prediction method according to the fourth embodiment.

FIG. 11 is an explanatory diagram for explaining a cause of warpage of a corner portion in the embodiment of the present invention.

FIG. 12 is a perspective view showing a shape of a resin injection molded product in the present embodiment, and an explanatory diagram for explaining an inner warpage evaluation unit.

13A and 13B are a diagram illustrating a transition of a temperature difference between the outer mold and the middle mold and a cross-sectional view illustrating the outer mold and the middle mold around the corner portion, for explaining the consideration for insufficient prediction accuracy in the present embodiment.

FIG. 14 is a cross-sectional view for explaining parameters of a corner portion in the present embodiment.

FIG. 15 is a chart showing an analysis procedure of a conventional warpage deformation prediction method for a resin injection molded product.

FIG. 16 is a diagram showing a relationship between a predicted value and an actually measured value of a mold temperature difference and an amount of internal warpage in a conventional warpage deformation prediction method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Resin injection-molded article 11 Opening 12 Corner

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4F206 AM35 AP05 JA07 JP13 JP18 JQ81

Claims (7)

[Claims] 1. A method for predicting warpage deformation of a resin injection molded product in which an injection molding analysis of a resin injection molded product having a corner portion is performed and a warpage amount is predicted and evaluated. A method for predicting warpage of a resin injection molded product, wherein an amount of warpage is predicted by performing injection molding analysis based on a created injection molding analysis model using a heat transfer coefficient. 2. The method according to claim 1, wherein an evaluation is performed based on the predicted warpage amount, and if there is a problem with the predicted warpage amount, molding conditions are changed and the injection molding analysis model is changed. A method for predicting warpage of a resin injection molded product, wherein the method is changed. 3. The method according to claim 2, wherein a contact area between the corner portion and a mold is taken into consideration.
A method for predicting warpage deformation of a resin injection-molded article, wherein the warpage amount is predicted by performing the injection molding analysis. 4. A model according to claim 3, wherein a model for thermal stress analysis is created, the internal warpage evaluating section is divided into a two-dimensional cross-section mesh, thermal stress analysis is performed, the internal warpage is evaluated, and there is no problem in the amount of warpage. A method for predicting warpage of a resin injection-molded article, which is taken into account in the judgment of (1). 5. The method according to claim 4, wherein an injection molding analysis result based on the injection molding analysis model is converted into an input condition for the thermal stress analysis. 6. The method according to claim 5, wherein input conditions for the thermal stress analysis are a resin temperature and a mold temperature. 7. The method according to claim 6, wherein the heat transfer coefficient is locally changed as an input condition for the thermal stress analysis.