JP2003154550A - Molded article, designing method therefor, and estimating method for length of weld line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the weld line of a molded article having an opening, or make the weld line as short as possible, and also, estimate the length of the weld line. SOLUTION: The flowing of a molten material is adjusted by changing a gate location or the like in such a manner that a location where the molten material which is injected from the gate and branched merges as a first time may become the corner of the opening. For the meeting angle of the molten material which merges at the corner, the angle of the corner is made the minimum angle, and the meeting angle becomes larger as the merging location moves outward. Then, when the meeting angle exceeds 135 deg., the weld line disappears. The meeting angle, at which the molten resin merges, starts from the angle of the corner. Therefore, a distance from a point at which the molten resin merges to a point at which the molten resin exceeds the meeting angle of 135 deg. wherein the weld line is not generated is short. That is, the weld line can be made shorter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a flow analysis to eliminate or shorten a weld line at a position where molten materials merge in a mold, a method for designing the same, and a method for predicting the length of the weld line. Regarding

[0002]

2. Description of the Related Art Conventionally, it is known that it is possible to roughly predict a site where a weld line will occur in injection molding.
The weld line is a groove formed in a portion where the molten material flows so as to branch in the cavity and then joins again to impair the function and appearance of the molded product after molding. For this reason, a method has been adopted in which the weld line is generated at a location that does not impair the design of the molded product or its width is narrowed.

As such a technique, for example, Japanese Patent Laid-Open No.
No. 128818 is known. This technique is to analyze the flow of molten material. When the association angle at which the molten material joins exceeds 135 °, the weld line becomes so small that it becomes hard to see. The width of the weld line is predicted by correcting the corner.

[0004]

However, in the prior art, not only a complicated calculation is required to predict the width and size of the weld line, but also in the case of a molded product having a complicated opening. Had a problem that it was difficult to obtain the width of the weld line and the meeting angle.

The present invention has been made in order to solve the problems of the above-mentioned conventional techniques, and eliminates the weld line of a molded product having an opening or shortens its length to provide excellent design. It is an object of the present invention to provide a molded article and a design method thereof and a method of predicting the length of a weld line.

[0006]

Means for Solving the Problem and Its Action / Effect The present invention has been made to solve the above-mentioned problem. In a molded product having an opening, a weld line formed by the joining of molten materials has an opening. It is characterized in that it is formed from the inner end of the corner to the outside.

According to another aspect of the invention, in a method of designing a molded product for manufacturing a molded product having an opening, a portion where the molten material injected from the gate and split is first merged is set as a corner of the opening. It is characterized by adjusting the flow of the molten material.

Further, another invention is a method for predicting a weld line of a molded article having an opening, wherein a molten material injected from a gate is shunted to form a weld line near a corner of the opening. The flow of the molten material is adjusted so that the molten material is analyzed, and the length of the weld line is obtained based on the association angle of the weld lines formed at the corners.

Here, as a preferable mode for adjusting the flow of the molten material, at least one of changing the gate position, changing the wall thickness of the molded product, or forming the channel of the mold is used.
This can be done by applying one.

In the present invention, molten material is injected through a gate to produce a molded article having an opening. The molten material injected from the gate flows along the openings and merges at the corners. A weld line is formed from the inner end of the corner of the merged portion to the outer side. At this time, the angle of association of the molten materials that meet at the corner becomes the smallest as the angle of the corner becomes smaller, and becomes larger as the meeting position goes outward. When the meeting angle exceeds 135 °, the weld line disappears. In this way, since the meeting angle at which the molten material merges starts from the angle of the corner, the distance until the meeting of 135 ° at which the molten material merges and does not form a weld line is short, that is, the weld line is eliminated. , Its length can be shortened.

In another invention, the flow of the molten material injected from the gate is subjected to flow analysis, the flow of the molten material is adjusted, and the weld line formed from the inside of the corner of the opening to the outside is formed. You can make predictions.
Therefore, the appearance of the molded product can be easily predicted, and the degree of freedom in design can be increased.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below in order to further clarify the constitution and operation of the present invention described above.

FIG. 1 is a perspective view showing a molded product 10 according to an embodiment of the present invention. The molded product 10 is formed by resin injection molding and has an opening 12. At the corner 12a of the opening 12, the weld line 1
4 are formed. The weld line 14 is opened by the molten resin being injected from the gate position Gt of the injection molding machine.
It flows along the peripheral edge of 2 and is a location where the corners 12a meet, and is formed from the inner end toward the outer side. Figure 2
FIG. 4 is a cross-sectional view showing the periphery of the weld line 14 of the molded product 10.

Next, the process of injection molding the molded product 10 will be described. FIG. 3 is an explanatory diagram for explaining the injection process of the molded product 10, which is represented by the shape of the cavity Ct of the mold. In FIG. 3, when the molten resin is injected from the gate position Gt, the molten resin branches and flows along the opening 12. Then, as shown in FIG. 4, a corner 1 of the opening 12 is formed.
The weld line 14 is formed by joining near 2a.

In such an injection molding process, a weld line may or may not be formed depending on the magnitude of the association angle when the molten resins merge. FIG. 5 is an explanatory diagram illustrating a state in which the molten resins merge. In FIG. 5, the contact angle of the weld line is defined as follows. The association angle θ is an angle θ formed when the left and right molten resins meet each other when the molten resins flow from two different directions for convenience, and join at every moment as shown by the wavy Wv. Becomes larger as the left and right molten resin progresses. On the other hand, for the flow velocity merging angle α of the weld line WL, as shown in FIG. 6, for example, as indicated by the arrow, the molten resin flows from two different directions on the left and right for convenience sake as indicated by the wavy Wv. In the case of merging momentarily, it means an angle α formed by two flow directions of the molten resin, and this flow velocity merging angle α appears as a constant angle if the two flow directions are constant. In FIG. 5 and FIG. 6, the weld line WL is linearly formed in the portion where the left and right molten resins merge. The association angle θ and the flow velocity converging angle α are generally complementary to each other. And the meeting angle θ is 135
If it is less than or equal to °, the weld line WL is formed,
It is recognized that the weld line WL is not formed above 5 °.

As described above, the weld line WL is formed in accordance with the association angle θ when the molten resins merge, but the initial angle of the association angle θ differs depending on the position where the molten resins first merge. That is, as shown in FIG. 7, when the first meeting point is a right-angled corner 12a, the meeting angle θ and the flow velocity meeting angle α are initially 90 °,
The converging position gradually increases as it moves from the inner end of the corner 12a to the outer side. On the other hand, as shown in FIG. 8, when the first merging portion is a straight line portion, the meeting angle θ and the flow velocity merging angle α are 0 ° at the beginning, and gradually increase toward the outside. That is, the initial value of the meeting angle θ is large at the time of merging at the corner 12a, and is small at 0 ° at the time of merging at the straight portion. And the confluence angle θ
Gradually increases as the resin material merges, and
If the angle exceeds 35 °, the weld line WL disappears.

As described above, the larger the angle at which the divided molten resins are first merged, the shorter the distance until the association angle θ reaches 135 °, and the weld line WLa in FIG. 7 is changed from the weld line WLb in FIG. Since it can be made shorter, the injection conditions are set so that they meet at the corner 12a where the meeting angle θ can be increased from the beginning. Such an injection condition is a parameter that can adjust the time required for the molten resin to reach the corner 12a. For example, the gate position is changed, the wall thickness of the molded product is changed, or the channel of the mold is formed. It is a condition. Among these, in the means for changing the wall thickness of the molded product and the means for forming the channel in the mold, the flow velocity can be changed due to the change in resistance when the molten material flows, and thus the corner 12a is reached. You can adjust the time until.

Therefore, even if the weld line can be eliminated or the weld line cannot be avoided, the weld line can be the shortest and the appearance of the molded product can be improved.

Next, a method for evaluating a weld line using a flow analysis during injection molding and a method for designing a molded product will be described. The flow analysis evaluation method and design method are carried out by a computer using commercially available flow analysis software as shown in the flowchart of FIG. Although there are various commercially available flow analysis software, the following can be used for carrying out the present invention. C-MOLD, MTI, MMA (Distributor: Moldflow Japan Co., Ltd.) Plamets (Developer: Plamedia Research Co., Ltd.) Keram (Distributor: Toyota Motor Corporation) I-DEAS Plastics (Distributor: Stocks) Dentsu International Information Service Co., Ltd.) I-MAP (Distributor: Toyo Communication System Co., Ltd.) TIMON (Developer: Toray Industries, Inc.)

First, in step S100, in addition to the data of the mold used for injection molding of the molded product, all data affecting the position of the weld line are input to the computer in which the flow analysis software is installed. At least the following data (1) to (8) are required as the data input to the computer in step S100. Of these, the data in (1) to (4) are particularly important, and it is necessary to enter accurate values. The temperature of the mold may be input from the keyboard, or data calculated by a program may be used. 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) Mold temperature (4) Injection speed ( 5) Physical properties (viscosity, thermal conductivity, specific heat) of molten resin to be injected (thermoplastic resin heated and melted) (6) Temperature of molten resin to be injected (7) Injection pressure (8) Injection time

In the subsequent step S102, a weld line prediction calculation for predicting the position of the weld line is performed. After predicting the position of the weld line in step S102, the result of predicting the position of the weld line is output as an image on the display in step S104. Succeedingly, in a step S106, it is determined whether or not the predicted position where the weld line is generated is close to the corner of the opening. When it is determined that the position of the weld line is not close to the corner, the process returns to step S100, and the conditions such as the gate position, mold shape, injection speed, injection pressure, and mold temperature are changed. Then, in step S106, the position of the weld line is evaluated again, and when the position of the weld line is below the desired level, the mold is manufactured under this condition (step S108), and the condition described above is satisfied. Then, the actual injection molding process is performed.

Therefore, whether the weld line can be eliminated by setting the position of the weld line at a corner at the design stage before manufacturing the mold and before molding.
The length can be accurately predicted, and the design work can be shortened and optimized.

The present invention is not limited to the above-described embodiments, but can be carried out in various modes without departing from the scope of the invention, and the following modifications can be made.

Although the opening in the above embodiment is rectangular and has 90 ° corners, the opening is not limited to this and may be corners of various angles, particularly an acute corner. The weld line can be eliminated when the meeting angle of is not less than 135 °.

[Brief description of drawings]

FIG. 1 is a perspective view showing a molded product 10 according to an embodiment of the present invention.

2 is a cross-sectional view showing the periphery of a weld line 14 of the molded product 10. FIG.

FIG. 3 is an explanatory diagram illustrating an injection process of a molded product.

FIG. 4 is an explanatory diagram illustrating an injection step following FIG.

FIG. 5 is an explanatory diagram illustrating a meeting angle θ.

FIG. 6 is an explanatory diagram illustrating a flow velocity merging angle α.

FIG. 7 is an explanatory diagram illustrating a process of forming a weld line at a corner.

FIG. 8 is an explanatory diagram illustrating a process in which a weld line is formed in a straight line portion.

FIG. 9 is a flowchart illustrating a weld line evaluation method.

[Explanation of symbols]

10 ... Molded products 12 ... Aperture 12a ... Corner 14 ... Weld line Gt ... Gate position Wv ... Wavy

Continued front page    (72) Inventor Kiyoshi Suenaga             Aichi Prefecture Kasuga-cho, Nishikasugai-gun Ochiai character Nagahata 1             Address within Toyoda Gosei Co., Ltd. (72) Inventor Megumi Suto             Aichi Prefecture Kasuga-cho, Nishikasugai-gun Ochiai character Nagahata 1             Address within Toyoda Gosei Co., Ltd. F-term (reference) 4F202 AM23 AM36 AP06 AP11 AR12                       CA11 CB01 CK11 CS10                 4F206 AM23 AM36 AP067 AP11                       AR12 JA07 JL02 JL09 JM04                       JN11 JP01 JP15 JP17 JP30                       JQ81 JQ90

Claims (5)

[Claims] 1. A molded product having an opening, wherein a weld line formed by joining molten materials is formed from an inner end of a corner of the opening toward an outer side. 2. A method of designing a molded article for manufacturing a molded article having an opening, wherein the molten material flowed so that the molten material injected from the gate and split is first merged into a corner of the opening. A method for designing a molded article, which comprises adjusting 3. The method for designing a molded article according to claim 2, wherein the flow of the molten material is adjusted by changing a gate position, changing a wall thickness of the molded article, or forming a channel of a mold.
A method for designing a molded product, which is performed by applying at least one. 4. A weld line predicting method for predicting a weld line of a molded article having an opening, wherein the molten material injected from a gate is shunted to form a weld line near a corner of the opening. The flow of the material is adjusted and the molten material is analyzed,
A method of predicting a weld line, characterized in that the length of the weld line is obtained based on the meeting angle of the weld lines formed at the corners. 5. The weld line prediction method according to claim 4, wherein the flow of the molten material is adjusted by changing a gate position, changing a wall thickness of a molded product, or forming a mold channel.
A method for predicting a weld line performed by applying at least one.