JP2882122B2 - Quality judgment method of molded product by molten material flow analysis - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for predicting and judging the quality of a molded article molded from a molten material such as an injection molded article by a molten material flow analysis in consideration of a state of a weld line generated at the time of molding. It relates to a method of judging pass / fail. In the present invention, among the molding failure phenomena occurring in the molded product, particularly, the decrease in the strength of the weld line is quantitatively predicted by simulation using a computer, and changes in molding conditions, product shapes, and mold designs are embodied in advance. And, as a result, a high-quality molded article can be obtained.

[0002]

2. Description of the Related Art At present, in the field of plastics, the CAE technique has become very important in the development of products and materials. In the past, plastic CAE was mostly analyzed for resin flow in a mold during injection molding. Recently, however, it has been applied to shrinkage / warpage analysis of injection molded products, characteristic analysis of molded article failure phenomena, blow / extrusion analysis, and more. Its contents are becoming more sophisticated and diversified, such as application to molding machine control. Looking at the injection molding among them, predicting the failure phenomenon of the molded product at the design stage by CAE and taking the optimal countermeasures realizes cost reduction by reducing the number of trial production and shortening the development period. Defective phenomena in injection molding include poor appearance and
There are dimensional accuracy and strength reduction, etc. If these can be explained theoretically and quantitatively expressed by CAE, measures such as changes in molding conditions, product shapes, mold designs, etc. will also be concrete. Recently, each company has been conducting CA
The approach from E is progressing and its practical application will be soon, but it will be an issue to develop it to other molding failure phenomena based on this approach in the future.

[0003]

[Problems to be Solved by the Invention] For example, when a countermeasure is taken against a molding failure phenomenon of an injection molded product, the result of the flow analysis has been conventionally performed by know-how, which is not sufficient. In particular, remarkable appearance defects
The properties of the welds that cause the strength to decrease can not be uniformly determined by the formation process, and it is impossible to predict the strength of the welds quantitatively.

[0004] The greatest factor influencing the properties of the weld is the degree of welding in the line, which is determined by the history of pressure and temperature in the resin flow process. However, this is effective for a completely collapsing weld where two flows collide at a right angle and the flow stops there, and although various studies have been made so far, as seen in general molded products, In the weld line (meld line), which continues to run parallel after the flow merges, there are other geometrical conditions where the flow meets the flow, that is, the weld angle of the weld line,
It is considered that the merging angle of the flow velocity becomes a problem.

[0005]

Means and action for solving the problems In the present invention,
Weld characteristics are predicted from the weld angle of the weld line or the merging angle of the flow velocity obtained by the CAE analysis, and the quality of the molded product is determined. In the present invention, the molten material flow analysis of the molded article shape model is performed to determine the flow line merging angle or association angle of the weld line of the molded article. The quality of the molded product was quantitatively predicted by the correlation factor between the joining angle or the association angle and the weld strength.

Further, the flow rate of the weld line of the molded article is determined by analyzing the flow of the molten material of the model of the molded article to determine the flow stream merging angle or the associated angle of the weld line and the weld strength. The acceptable flow velocity merging angle or the acceptable meeting angle set based on the correlation curve with the flow line merging angle or the association angle of the weld line determined by the flow analysis is compared. Is it judged to be pass when the meeting angle determined by the flow analysis is smaller than the acceptable flow joining angle or larger than the acceptable setting meeting angle, and is the flow velocity joining angle found by the flow analysis larger than the acceptable setting flow joining angle? When the angle of association obtained by the flow analysis is smaller than the set angle of acceptance, it is determined to be rejected.

[0007]

Next, the present invention will be described in detail with reference to one embodiment shown in the drawings. First, an embodiment using a test piece for obtaining a correlation between the weld line association angle and the merging angle of the flow velocity and the weld strength will be described. The weld angle of the weld line and the flow velocity merging angle are defined as follows.

As shown in FIG. 6, for example, as shown by an arrow as a gate, the weld line junction angle is such that the molten resin flows from two different directions on the right and left for convenience, as shown by a wavy line 1, and is instantaneous. When the left and right molten resins meet, the angle θ formed when the left and right molten resins meet is referred to, and the association angle θ increases as the left and right molten resins advance. As shown in FIG. 7, for example, as shown by arrows, when the molten resin flows from two different directions on the right and left as shown in FIG. The angle α formed by the two flow directions is expressed as a constant angle if the two flow directions are constant. In FIG. 6 and FIG. 7, reference numeral 2 denotes a weld line generating position which can be linearly formed at the portion where the left and right molten resins have joined. The weld line occurrence position 1 in FIG. 7 is inclined to the lower flow velocity due to the difference in the flow velocity of the left and right molten resins. In general, the association angle θ and the flow velocity merging angle α are complementary to each other.

In the present invention, as shown in FIG. 1, a correlation between the weld line association angle θ or the flow velocity merging angle α and the weld strength is obtained in advance. Then, the molten resin flow analysis of the molded product shape model to be molded is performed to determine the weld line association angle θ or the flow velocity merging angle α of the molded product. Then, a weld strength, for example, a bending strength, is obtained from the correlation obtained in advance and the obtained association angle θ or the flow velocity merging angle α, and is quantitatively predicted. Of course, the obtained association angle θ or the flow velocity merging angle α is compared with the acceptable set association angle θ ₁ or the acceptable set flow merging angle α ₁ set from the correlation, and the flow velocity merging angle obtained by the flow analysis. If α is smaller than the set flow joining angle α ₁ or the association angle θ obtained by flow analysis is larger than the set meeting angle θ ₁ , the flow is judged to be acceptable, and the flow velocity joining angle α ₁ found by flow analysis is The meeting angle θ larger than the passing set flow joining angle α ₁ or the meeting angle θ obtained by the flow analysis is the passing set meeting angle θ ₁
When it is smaller than this, it is judged to be rejected.

In the present invention, the weld line association angle θ
An example using a test piece for obtaining a correlation between the flow velocity merging angle α and the weld strength will be described. In FIG. 4, reference numeral 3 denotes a test piece product, the horizontal and vertical dimensions are as shown, and the plate thickness is 2 mm. Further, a pin is provided on the mold so that the hole 4 is formed in the center of the test piece product 3. The gate shape was a film gate. As the material used for the injection, glass fiber 30% reinforced 66 nylon (Ube nylon 2020GC made by Ube Industries)
6).

For the test piece product 3 shown in FIG. 4, four types of injection rates of 10, 50, 100 and 150 cc / sec, three types of resin temperatures of 270, 285 and 300 ° C., and holding pressures of 100, 400 and Three types of 800 kg / cm ² are selected, and flow analysis and molding experiments are performed under each condition.
Note that MELTFLOW (manufactured by Ube Industries) is used as flow analysis software. The mold temperature was 80 ° C. As shown in FIG. 5, a test piece 3 is formed from the test piece product 3 obtained by molding at intervals of 5 mm from the weld formation start point, and a bending and tensile test is performed at a distance between spans of 20 mm. Then, the relationship between the test piece position and the weld strength is plotted.

On the other hand, from the flow analysis, the relationship between the test piece position and the weld line association angle θ and the flow velocity merging angle α is calculated. From the above-described molding experiment / strength test and flow analysis, for example, the correlation between the flow velocity merging angle and the weld strength, in this case, the bending strength shown in FIGS. 2 (a) to 2 (c) is derived. Alternatively, for example, a correlation between the weld line association angle and the weld strength, in this case, the bending strength shown in FIG. 3, is derived. FIG. 2A shows the injection rate, and FIG.
2B shows the effect of the holding pressure, and FIGS. 2C and 3 show the effect of the resin temperature. These relationships are compiled into a database for each resin.

On the other hand, the flow analysis of the target product is performed,
The weld strength is quantitatively predicted from the weld angle of the weld line and the merging angle of the flow velocity calculated from the calculated angle. As a result, appropriate countermeasures are derived. In other words, by changing the weld line generation position and weld line association angle by computer simulation,
Product design satisfying required quality can be performed. Also, changes in molding conditions, product shapes, and mold designs can be embodied in advance. Although it depends on the molding resin and molding conditions, for example, the flow velocity merging angle α is 2
It can be set to 0 to 30 degrees or less. In addition,
Regarding the relationship between the flow velocity merging angle and the bending strength, the analysis results and the measurement results are almost the same.

As shown in FIGS. 2 (a) to 2 (c) and FIG. 3, there is a correlation between the bending angle and the junction angle of the weld line and the flow velocity. This is because during the weld forming process, solidification occurs at the surface layer in contact with the mold as soon as the flow front is reached,
Although the state at that time is maintained, the flow continues without solidification inside, so that the information at the time of reaching the flow front is not left and remains almost constant throughout. In other words, a slight difference near the surface layer is unlikely to appear in the tensile strength, which is affected by the state of the entire cross section of the molded product, but is noticeable in the bending strength, which is affected by the state of the outermost layer in the section. It is considered that it is. In the tensile test, the tensile strength is not influenced by the weld angle of the weld line or the flow velocity merging angle within the range of the measured data.

Looking at the correlation between the weld line association angle and the flow velocity merging angle with respect to the weld strength, both of them maintain a constant low level up to the angle (150 deg at the weld line association angle and around 30 deg at the flow velocity merging angle). After that, it shows a form in which the strength rapidly rises to the original strength of the material, and no particularly significant difference is observed.
Therefore, when evaluating the weld characteristics, both the weld line association angle and the flow velocity merging angle can be used.

The correlation between the molding conditions and the weld strength indicates that the higher the injection rate and the resin temperature are, the higher the bending strength tends to be. This is the temperature at the time of flow
It is considered that the increase in the pressure increased the degree of welding at the weld portion. The holding pressure is almost the same at the three levels, and it can be said that the bending strength of the weld is determined by the flow process of the resin.

In the above, the correlation between the weld line association angle or the flow merging angle and the bending strength of the weld portion has been mainly described. However, when the weld characteristics are evaluated by CAE, the molding data which is input data is used. Weld line information is output in the form of temperature, pressure, flow velocity, weld line junction angle or flow velocity merging angle with respect to conditions. Therefore, if information other than the meeting angle is to be considered,
The weld characteristic can be predicted as in the following equation. W = a ₁ F (weld line association angle or flow velocity merging angle) + a ₂ F (temperature) + a ₃ F (pressure) + a ₄ F (flow velocity) where W is a quantitative value indicating the characteristics of the weld portion, and F is each function of factors, a ₁ is a coefficient, which is determined in advance by experimental analysis and CAE analysis.

[0018]

According to the present invention, as described in the claims, the flow analysis of the target product is performed, and the weld strength is calculated from the joint angle of the weld line and the confluence angle of the flow velocity calculated from the flow analysis. Is quantitatively predicted.
As a result, appropriate countermeasures are derived. That is,
By changing the weld line generation position and the weld line association angle by computer simulation, it is possible to design a product that satisfies the required quality. Also, changes in molding conditions, product shapes, and mold designs can be embodied in advance. In addition, pass / fail can be determined based on the magnitude of the flow velocity merging angle or the association angle obtained by the flow analysis.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

2 (a) to 2 (c) are graphs showing a relationship between a merging angle of flow velocity and bending strength.

FIG. 3 is a graph showing a relationship between a weld line association angle and a bending strength.

FIG. 4 is a plan view showing the shape of a test piece used as one embodiment of the present invention.

FIG. 5 is a plan view showing physical property measurement conditions using a test piece.

FIG. 6 is an explanatory diagram showing a definition of a weld line association angle.

FIG. 7 is an explanatory diagram showing a definition of a flow velocity merging angle.

[Explanation of symbols]

 θ Weld line association angle α Flow velocity merging angle 1 Wavy 2 Weld line generation position 3 Test piece product 4 Hole 5 Test piece

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Osamu Amano, “Injection molding CAE and molding failure”, February issue of Plastics, Industrial Research Institute, Ltd., February 1, 1988, Vol. 39, No. 2, No., p. 25-33 Fujita, Shigai, 1 "<ASPLAST> System for Mold Design and Optimization of Molding Conditions", Synthetic Resins, Japan Synthetic Resins Institute of Technology, November 1, 1987, p. 2- 7 (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45/00-45/84 G06F 15/60 310

Claims (2)

(57) [Claims] A flow analysis of a molten material of a model of a molded article is performed to determine a flow stream merging angle or an association angle of a weld line of the molded article. A method for judging the quality of a molded article by molten material flow analysis, which quantitatively predicts the quality of the molded article based on the correlation factor between the junction angle or association angle and the weld strength. 2. A flow rate merging angle or an association angle of a weld line of a molded product is obtained by performing a molten material flow analysis of a molded product shape model, and a flow line merging angle or an association angle of the weld line and a weld portion strength determined in advance. The acceptable flow velocity merging angle or the acceptable meeting angle set based on the correlation curve with the flow line merging angle or the association angle of the weld line obtained by the flow analysis is compared. Is it judged to be pass when the meeting angle determined by the flow analysis is smaller than the acceptable flow joining angle or larger than the acceptable setting meeting angle, and is the flow velocity joining angle found by the flow analysis larger than the acceptable setting flow joining angle? A method for determining the quality of a molded article by a molten material flow analysis, wherein a failure is determined when the angle of association obtained by the flow analysis is smaller than the set angle of acceptance.