JPH0919953A - Evaluation method and design method for fluidity analysis of mold for synthetic resin injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce time and costs to obtain an optimum mold for synthetic resin injection molding by comparing the position of a weld obtained by the first prediction calculation with the thickness of a solidified layer obtained by the second prediction calculation. SOLUTION: The position of a weld is prediction-calculated (step 1) and image-output on a display (steps 2, 3). The output images are overlapped and compared, and the thickness of a solidified layer predicted at the position of the weld is obtained (step 4). The conditions of the mold are regulated so that at the position of the weld which was obtained by the first calculation, the thickness of the solidified layer obtained by the second calculation becomes a prescribed value or less. When the thickness of the solidified layer at the position of the weld is judged to be greater than a prescribed value (step 5), the generation of a visible weld line at the position of the weld is considered possible (step 8). In this case, data are changed, and the steps 1-4 are repeated until the thickness of the solidified layer becomes a prescribed value or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The method of evaluating and designing a flow analysis of a synthetic resin injection molding die according to the present invention uses a decorative panel of a controller provided in a dashboard part for controlling an automobile air conditioner, for example. It is used to design a synthetic resin injection molding die to make.

[0002]

2. Description of the Related Art An air conditioner for cooling and heating or dehumidifying an interior of an automobile is controlled by a controller provided on a dashboard on the side of a driver's seat. Since the surface of this controller is exposed inside the automobile, the appearance is adjusted by covering it with a decorative panel 1 as shown in FIG. This decorative panel 1 is generally A
It is often made by injection molding a BS-based synthetic resin.

In order to manufacture the decorative panel 1 by injection-molding such a synthetic resin, an ABS-based synthetic resin which is heated and melted in a cavity provided inside a mold constituted by a plurality of mold elements is manufactured. The resin is injected through a plurality of gates 2 and 2 provided at positions separated from each other. The inner surface shape of the cavity corresponds to the outer surface shape of the decorative panel 1 to be made. Further, the synthetic resin is heated to about 250 ° C. and stored in the cylinder in a molten state. During injection molding, a predetermined pressure is applied to the synthetic resin from the cylinder into the cavity. It is sent through the gates 2 and 2. The synthetic resin thus sent into the cavity is cooled and solidified in the cavity and then taken out from the mold. At the time of this take-out work, the plurality of mold elements are divided (the mold is opened), and one or a plurality of knockout pins attached to any of the mold elements are protruded, and The decorative panel 1 is separated. The portions shown as gates 2 and 2 in FIG.
The surplus portion formed in the semi-finished product is described as the gates 2 and 2 for the sake of explanation.

In order to injection-mold the decorative panel 1 as described above, it is necessary to send a synthetic resin into the cavity through the plurality of gates 2 and 2. The reason for this is that the molten synthetic resin is evenly distributed in the cavity having a flat inner surface shape in accordance with the outer surface shape of the decorative panel 1, so that the uniform decorative panel 1 is manufactured. However, due to the feeding of the synthetic resin from the plurality of gates 2 and 2 and the shape of the decorative panel 1, a defect called a weld line occurs in the finished decorative panel 1.

That is, a plurality of through holes 3 and 3 are formed in the decorative panel 1 for fitting various switches and indicators.
The synthetic resin sent into the cavity from the plurality of gates 2 and 2 goes around the through holes 3 and 3 and enters the portions 4 and 4 between the adjacent through holes 3 and 3. On this occasion,
Synthetic resin enters these inter-portions 4 and 4 from both sides of the inter-portions 4 and 4 and hits (merges) with each other at the intermediate portions of the inter-portions 4 and 4. As a result, a deformation such as a slight depression of the surface occurs in the intermediate portion between the spaces 4 and 4. This deformation is a defect called the weld line. In the case of the decorative panel 1 shown in FIG. 4,
Weld lines are generated at the portions indicated by the solid lines a.

[0006] In such a weld line portion, the strength of the product itself is lower than that of the other portions, but in the case of the decorative panel 1, the decrease in strength hardly poses a problem. However, when a deformation such as a dent appears on the surface, the appearance of the decorative panel 1 is deteriorated and the product value is reduced. For this reason,
Decorative panel 1 obtained by injection molding synthetic resin
The surface of the panel is further painted to hide the weld line, or the surface of the decorative panel 1 is made matt by forming fine textured surface irregularities called grain to make the weld line inconspicuous. . In addition, flow analysis software that predicts the position of the weld line (“T” manufactured by Toray Industries, Inc.
IMON ”) to move the weld line to an inconspicuous position such as a corner of the decorative panel 1,
Attempts have also been made to regulate the position of 2.

However, in the method of coating the surface of the decorative panel 1, the cost of the decorative panel 1 is high. or,
The matte surface method limits the design of the dashboard part. Moreover, even when matte, the weld line is slightly less noticeable than in the case where the glossy surface is finished, and the weld line is not lost. That is, even when the surface of the decorative panel 1 is frosted, as shown in FIG. 5, the height of the unevenness formed in the vicinity of the weld line 5 is formed in the portion distant from the weld line 5. It becomes lower than the height of the unevenness. Then, when the surface of the decorative panel 1 is visually inspected, the existence of the weld line 5 becomes apparent due to the difference in height of the unevenness. Further, the presence of the weld line 5 can be visually confirmed even by the method of moving the weld line 5 to an inconspicuous position such as a corner of the decorative panel 1.

As a technique for solving such inconvenience, the present inventors first set the temperature of the mold at 90 when the synthetic resin is injected into the cavity through the plurality of gates 2, 2.
The inventors invented a method for producing a synthetic resin panel in which the weld line can be made inconspicuous by regulating the temperature in the range of up to 110 ° C. Regarding this invention, in addition to applying for a patent as Japanese Patent Application No. 7-127682, it is also described on pages 23 to 28 of "CALSONICWORLD Vol.2" issued by the applicant company on June 10, 1995. ing.

According to the method for manufacturing a synthetic resin panel of the present invention, the synthetic resin spreads along the inner surface of the cavity even at the weld portion, and a weld line that can be visually confirmed is not formed. Therefore, it is not necessary to paint the surface later. The reason for limiting the mold temperature to the range of 90 to 110 ° C. is that if the temperature is lower than 90 ° C., a weld line that can be visually confirmed is formed on the surface of the obtained synthetic resin panel. On the other hand, the limit on the high temperature side is not from the aspect of suppressing the occurrence of weld lines,
It is regulated in terms of the efficiency of manufacturing work. If the temperature of the mold is too high, it takes time to cool and solidify the ABS synthetic resin fed into the cavity even if the generation of weld lines is suppressed. If this temperature exceeds 110 ° C., it is difficult to secure work efficiency that can be put to practical use. Therefore, the mold temperature is regulated within the range of 90 to 110 ° C. as described above. still,
In order to secure sufficient work efficiency while suppressing the occurrence of weld lines, it is preferable to regulate the mold temperature within the range of 90 to 100 ° C.

The reason why the occurrence of weld lines can be suppressed by increasing the mold temperature in this way is as follows.
The temperature of the synthetic resin sent from the gates 2 and 2 into the cavity of the mold is lowered by touching the inner surface of the cavity. Then, the portion contacting the inner surface of the cavity is solidified before the portion distant from the inner surface.
As shown in (A) and (B), a solidified layer 6, which is also called a skin layer, is formed at the contacting portion. The molten resin 7 present inside the solidified layer 6 deforms the solidified layer 6 while
It is pressed against the inner surface 9 of the cavity 8 of the mold 10. This pressing is sufficiently performed if the solidified layer 6 is thin as shown in FIG. 6B, and the obtained synthetic resin panel (for example, FIG.
The surface shape of the decorative panel 1) shown in to 5 corresponds to the shape of the inner surface 9. On the other hand, when the solidified layer 6 is thick as shown in FIG. 4A, the pressing is incomplete and the surface shape of the obtained decorative panel 1 does not match the shape of the inner surface 9.

On the other hand, when the temperature of the die 10 is low, the temperature of the synthetic resin fed into the cavity 8 is rapidly lowered, so that the solidified layer 6 is welded as shown in FIG. 6 (A). By the time it reaches, the solidified layer 6 becomes hard to be deformed. Therefore, when the temperature of the mold 10 is low, the weld line is conspicuous. On the other hand, the mold 10
When the temperature is high, the temperature drop of the synthetic resin fed into the cavity 8 becomes slow, so that the solidified layer 6 becomes thin as shown in FIG. 6B even in the weld portion. The solidified layer 6 is easily deformed. Therefore, mold 1
When the temperature of 0 is high, the surface shape of the decorative panel 1 matches the shape of the inner surface 9 of the cavity 8 as described above, and the weld line becomes inconspicuous.

7A and 7B, the mold temperature is 60
The weld part of the decorative panel 1 (Figs. 4 and 5) injection-molded so that the surface has a satin finish at ℃ and the weld part of the decorative panel 1 injection-molded at 95 ° C are perpendicular to the weld lines. Direction surface shape,
The measurement result measured by the surface roughness meter is shown. Figure 7
(A) shows the measurement result of what was injection-molded at a mold temperature of 60 ° C, and (B) shows the measurement result of what was injection-molded at 95 ° C. This FIG.
In (and FIG. 8 described later), the vertical axis is magnified 2000 times, and the horizontal axis is magnified 100 times.

From FIG. 7A and FIG. 7B, neither weld line can be confirmed. However, it was confirmed that the surface shape of the invented product injection-molded at 95 ° C. was finer than the surface shape of the conventional product injection-molded at 60 ° C. From this, it can be seen that the previous invention is effective in matching the outer surface shape of the decorative panel 1 with the inner surface shape of the cavity. The weld line of FIG. 7 (A) could be visually confirmed, whereas the weld line of FIG. 7 (B) could not be visually confirmed.

Next, in FIGS. 8A and 8B, the mold temperature is set to 6
The surface shape of the welded part of the decorative panel 1 having a glossy surface which was injection molded at 0 ° C. and the welded part of the decorative panel 1 similarly injection molded at 95 ° C. in the direction perpendicular to the weld line, The result measured by the surface roughness meter is shown. FIG. 8 (A) shows the measurement result of the injection-molded product with the mold temperature of 60 ° C., and FIG. 8 (B) shows the measurement result of the injection-molded product with the mold temperature of 95 ° C.

As is clear from FIGS. 8A and 8B,
In the case of the conventional product injection-molded at 60 ° C, it was confirmed from the measurement results that a clear weld line was formed, but in the case of the previous invention product injection-molded at 95 ° C, the weld line was confirmed. could not. Also, by visual inspection,
A weld line could be confirmed in the one corresponding to FIG. 8 (A), but a weld line could not be confirmed in the one corresponding to FIG. 8 (B). Therefore, even when the surface is a glossy surface, the decorative panel 1 having a good appearance can be obtained without coating the surface.

[0016]

Since the method for producing a synthetic resin panel of the previous invention is constructed as described above,
Although it is possible to obtain a synthetic resin panel that is low in cost and good in appearance, it is necessary to improve the following points in order to obtain a higher quality synthetic resin panel at a lower cost.

As is clear from the above description of the invention,
In order to make the weld line inconspicuous, it is effective to raise the temperature of the mold to reduce the thickness of the solidified layer 6, but
The thickness of the solidified layer 6 is not uniform over the entire surface of the synthetic resin panel and is partially different. Therefore, in order to make the weld line more inconspicuous, it is necessary to control the shape of the cavity of the synthetic resin injection mold and the position of the gate so that the solidified layer 6 becomes thinner at the weld portion.

Of course, it is possible to find the optimum shape of these cavities and the position of the gate by trial and error, but not only it takes time to obtain the optimum synthetic resin injection molding die, The cost required for trial production of the mold increases. Since the manufacturing cost of the mold is considerably high, it is not preferable to design the mold by such trial and error. The method for evaluating and designing the flow analysis of the synthetic resin injection molding die of the present invention was invented in view of such circumstances.

[0019]

Among the evaluation methods and design methods of the flow analysis of the synthetic resin injection molding die of the present invention, in the flow analysis evaluation method, heating is performed in the cavity of the synthetic resin injection molding die. It is formed on the surface of the thermoplastic resin in the cavity under the same conditions as the first prediction calculation that predicts the position of the weld that occurs when the molten thermoplastic resin is injected from multiple gates based on computer calculation A second prediction calculation for predicting the thickness of the solidified layer based on computer calculation is performed. Then, at least in a portion of the surface of the obtained synthetic resin product that is visible, the position of the weld obtained by the first prediction calculation is compared with the thickness of the solidified layer obtained by the second prediction calculation. . Then, in the design method, the condition of the mold is regulated so that the thickness of the solidified layer obtained by the second prediction calculation becomes a predetermined value or less at the position of the weld obtained by the first prediction calculation.

[0020]

According to the evaluation method and the design method of the flow analysis of the synthetic resin injection molding die of the present invention as described above, even at the position of the weld where the occurrence is predicted, even if the die is not trial-produced. By obtaining the predicted thickness of the solidified layer, it is possible to predict whether or not the weld line will be noticeable, and to design the mold so as to make the weld line inconspicuous. That is, at the position of the weld obtained by the first prediction calculation, when the thickness of the solidified layer obtained by the second prediction calculation is large, it is considered that the weld line is conspicuous. In order to shift the position with the thick part of the layer, the mold conditions such as the shape of the mold cavity and the gate position are changed to newly
Perform the second prediction calculation. Since these first and second prediction calculations can be performed without actually making a trial mold, the time required to obtain an optimum synthetic resin injection molding mold and the cost can be reduced.

[0021]

EXAMPLE An example of the present invention will be described with reference to FIGS. The flow analysis evaluation method and design method of the synthetic resin injection molding die of the present invention are carried out by a computer using commercially available flow analysis software as shown in the flowchart of FIG. There are various commercially available commercially available flow analysis software, and, for example, the following ones can be used for carrying out the present invention. MOLD FLOW (Distributor: Dentsu International Information Service Co., Ltd.) C-MOLD (Distributor: Ryoka System Co., Ltd.) Plamedia (Developer: Plamedia Research Co., Ltd.) Keram (Distributor: Toyota Motor Corporation) ) I-DEAS Plastics (Distributor: Dentsu International Information Service Co., Ltd.) I-MAP (Distributor: Toyo Information Systems Co., Ltd.) TIMON (Developer: Toray Industries, Inc.) Image data of TIMON
Obtained using.

First, in step 1, in a computer in which the above-mentioned flow analysis software is installed, in addition to the data of the mold used for injection molding of the synthetic resin panel, any position that affects the position of the weld and the thickness of the solidified layer is influenced. Enter the data. Then, the first prediction calculation for predicting the position of the weld and the second prediction calculation for predicting the thickness of the solidified layer are performed. In addition, as the data input to the computer in this step 1, at least the following items (1) to (8) are required. The data of (1) to (4) are especially important,
You need to enter a particularly accurate value. Since the data of (5) to (6) are the next most important, it is necessary to enter the correct value. Although the data of (7) to (8) have little influence on the calculation result, it is preferable to input an accurate value in order to obtain a more accurate calculation result. (1) Three-dimensional shape of cavity in mold (including thickness, width, cross-sectional shape and plane shape) (2) Number of gates and position of each gate (3) Temperature of mold (4) Injection speed ( 5) Physical properties (viscosity, thermal conductivity, specific heat) of the molten resin to be injected (thermoplastic resin heated and melted) (6) Temperature of the molten resin to be injected (7) Injection pressure (8) Injection time

If the data of the above (1) to (8) is input to the computer and the above first and second prediction calculations are performed,
Next, in step 2, the result of the first prediction calculation is output as an image on a display, and is output by a printer as needed. FIG. 2 is an example of an image showing the result of the first prediction calculation, which is obtained when it is assumed that the ABS resin heated to 250 ° C. is injected into the mold of 95 ° C. It should be noted that the actual output represents the possibility of weld occurrence for each color (for example, seven colors like a rainbow). For example, the part where weld is unlikely to occur is displayed in red, the part where weld is most likely to occur is displayed in green or blue, and the part where weld is likely to occur is yellow. Display with. FIG.
, The parts that are not likely to generate welds in red are shown in white, and the parts that are most likely to be displayed in green or blue are shown in diagonal lines and in yellow. The portions where there is a possibility that welds may occur are indicated by hatching.

Next, in step 3, the result of the second prediction calculation is output as an image on a display and is output by a printer as needed. Of course, the order of steps 2 and 3 may be reversed. FIG. 3 is an example of an image showing the result of the second prediction calculation. The actual output represents the thickness of the solidified layer for each color, as in the output image representing the first prediction calculation. For example, display the part with the thinnest solidified layer in indigo,
The thickest portion is displayed in red, and the intermediate thickness portion is displayed in yellow to blue. In FIG. 3, the thinnest portion of the solidified layer displayed in indigo is outlined, the thickest portion of the solidified layer displayed in red is hatched, and the thickness of the solidified layer displayed in yellow or blue. Hatching indicates the middle part of each.

The output images obtained in the above steps 2 and 3 based on the calculation result in the above step 1 are overlaid and compared in the next step 4, and the predicted solidified layer at the position of the weld where the occurrence is predicted. Find the thickness of. Then, the condition of the mold is regulated so that the thickness of the solidified layer obtained by the second prediction calculation becomes a predetermined value or less at the position of the weld obtained by the first prediction calculation. For this purpose, the positions of the welds indicated by slanting lattices or hatching in FIG. 2 and the solidified layer portions indicated by slanting lattices or hatching in FIG. To do. The operation of superimposing the output images obtained in steps 2 and 3 in step 4 can be performed not only by superimposing the printed out data, but also by omitting the printout and directly performing it on the display.

As a result of the superposition of the output images in the above step 4, in the next step 5, whether or not the slanted grids or hatching in FIGS. 2 and 3 overlap each other, in other words, solidification at the weld position. It is determined whether the layer thickness is below a predetermined value. If it is determined that the thickness of the solidified layer is less than or equal to the predetermined value, it is considered that no visible weld line is generated at the weld position (step 6). Therefore, in this case, a mold is manufactured under the conditions input to the computer in step 1 (step 7). The predetermined value cannot be generally regulated because it depends on the shape and thickness of the synthetic resin part to be injection-molded. For example, when the synthetic resin part is a decorative panel for a controller provided on the dashboard part as described above, the predetermined value is 0.4 to 0.6 μm.
A value of about m can be adopted. Of course, the smaller the predetermined value, the more reliably the occurrence of weld lines can be prevented.
Therefore, in the case of the above decorative panel, this predetermined value is 0.4
If it is set to μm, the generation of weld lines that are almost visible can be eliminated. In addition, not only the thickness of the solidified layer at the position of the weld but also the association angle, which is the angle when the molten resins flowing from the opposite side at the position of the weld join (associate), is necessary for the generation of the weld line. Affect. On the other hand, since such an association does not occur at positions other than the position of the weld, even if the solidified layer becomes thick, defects such as weld lines do not occur.

On the contrary, when the slanted lattices or hatching of FIGS. 2 and 3 overlap each other, in other words, when it is determined in step 5 that the thickness of the solidified layer at the weld position is larger than the predetermined value. It is considered that a visible weld line may occur at the position of the weld (step 8). Therefore, in this case, steps 1 to 4 are repeated again by changing the data that influences the shape of the cavity in the mold, the number of gates and the position of each gate, the position of the weld and the thickness of the solidified layer. This repetition is repeated until the slanted lattices or hatching in FIGS. 2 and 3 do not overlap with each other, that is, until the thickness of the solidified layer becomes equal to or less than a predetermined value in step 5. The relationship between the changing direction of the data and the changing direction of the position of the weld and the thickness of the solidified layer is known to some extent from experience. Therefore, those skilled in the art can easily predict the data for preventing the oblique grids or the hatching from overlapping each other. Therefore, if the data is changed based on the prediction, the number of times of the above repetition will not be excessively increased. During such repetition, it is not necessary to actually make a trial mold before determining the optimum mold shape. Therefore, it is possible to reduce the cost and time required for manufacturing a die, which is costly and time-consuming.

It is an object of the present invention to prevent the formation of a visible weld line on the surface of a synthetic resin part such as a decorative panel of a controller and to improve the texture of this synthetic resin part. It is in. Therefore, there is no problem in forming a weld line on the surface of the synthetic resin part which cannot be seen in the assembled state. Therefore, as shown in FIG.
It is sufficient to determine whether or not the slanted grids or hatching of 3 are overlapped with each other only on the portion of the surface of the synthetic resin product that is visible.

[0029]

EFFECTS OF THE INVENTION The flow analysis evaluation method and design method of the synthetic resin injection molding die of the present invention can determine whether or not the weld line is conspicuous, without actually making a trial of the die, so that it is optimal. The time required to obtain a synthetic resin injection molding die and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

FIG. 2 is a diagram showing image data representing the result of the first prediction calculation.

FIG. 3 is a diagram showing image data representing a result of second prediction calculation.

FIG. 4 is a front view of a decorative panel made by injection molding of synthetic resin.

FIG. 5 shows a decorative panel made by a conventional method, FIG.
FIG.

FIG. 6 is a schematic view showing a state in which a cavity portion is cut in the same direction as FIG. 5 in order to explain the reason why the weld line is inconspicuous according to the prior invention.

FIG. 7 shows a measurement result of a welded portion of a decorative panel having fine irregularities formed on its surface, which is measured by a surface roughness meter,
FIG. 3A is a diagram showing the measurement results for a decorative panel made by the conventional method, and FIG. 6B is a diagram showing the measurement results for a decorative panel made by the prior invention method.

FIG. 8 shows measurement results of a welded part of a decorative panel having a glossy surface, which is measured by a surface roughness meter, and (A) shows a measurement result of a decorative panel manufactured by a conventional method,
(B) is a diagram showing the measurement results of the decorative panel manufactured by the method of the prior invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Decorative panel 2 Gate 3 Through hole 4 Intersection 5 Weld line 6 Solidified layer 7 Molten resin 8 Cavity 9 Inner surface 10 Mold

Claims (2)

[Claims] 1. A first prediction calculation for predicting the position of a weld occurring when a thermoplastic resin heated and melted is injected from a plurality of gates into a cavity of a synthetic resin injection molding die based on computer calculation. And a second prediction calculation for predicting the thickness of the solidified layer formed on the surface of the thermoplastic resin in the cavity under the same conditions, based on computer calculation, and at least on the surface of the obtained synthetic resin product. Evaluation of the flow analysis of the synthetic resin injection molding die that compares the position of the weld obtained in the first prediction calculation with the thickness of the solidified layer obtained in the second prediction calculation in the part touching Method. 2. A first predictive calculation for predicting the position of a weld generated when a thermoplastic resin heated and melted is injected from a plurality of gates into a cavity of a synthetic resin injection molding die based on computer calculation. And a second prediction calculation for predicting the thickness of the solidified layer formed on the surface of the thermoplastic resin in the cavity under the same conditions, based on computer calculation, and at least on the surface of the obtained synthetic resin product. At the position of the weld obtained by the first prediction calculation, the conditions of the mold are regulated so that the thickness of the solidified layer obtained by the second prediction calculation becomes a predetermined value or less at the portion touching Design method of mold for synthetic resin injection molding.