JP5471197B2 - Manufacturing method for forming hollow body by DSI molding - Google Patents

Description

  The present invention relates to a manufacturing method for forming a hollow body by DSI (Die Slide Injection) molding.

In recent years, DSI (Die Slide Injection) molding including DRI (Die Rotation Injection) molding is known as a method for producing a hollow product made of a synthetic resin having a complicated shape.
In DSI molding, in a primary molding, a pair of semi-hollow bodies having a joint at the opening edge is injection molded. In secondary molding, a method of forming a hollow molded product having an internal space by combining the joints of a pair of semi-hollow bodies immediately after molding, injecting molten resin into the joints, and joining the joints together It is.
More specifically, in the secondary molding, the joining passages are formed so as to extend over the entire length of the opening edges of the pair of semi-hollow bodies by joining the joint portions of the pair of semi-hollow bodies.
In addition, when the joint portions of the pair of semi-hollow bodies are combined, an injection port for injecting the molten resin into the joint passage is formed at the joint portion located opposite to the internal space simultaneously with the formation of the joint passage. A plurality of joining passages are formed at intervals in the extending direction.
Then, the molten resin is injected into the joining passage from each injection port, and the molten resin moves in the joining passage while melting the inner wall portion of the joining passage and is filled in the joining passage. As a result, the joints are joined together to form a hollow product made of synthetic resin having an internal space.
In this case, since the temperature of the pair of semi-hollow bodies to which the joint portions are joined in the secondary molding is high and the resin is not completely cured, the wall portion of the joint passage facing the injection port is injected. It is easy to melt depending on the amount of heat of the molten resin, and there is a concern that resin leakage may occur from the melted portion due to the pressure of the molten resin.
In view of this, a technique has been proposed in which resin leakage is prevented by inserting a plate-like insert part into the wall portion of the bonding passage facing the injection port (Patent Document 1).

JP-A-8-11155

However, since the above-described prior art requires insert parts, the cost increases due to the increase in the number of parts and the number of man-hours, which is disadvantageous in reducing the cost.
The present invention has been devised in view of the above circumstances, and an object of the present invention is to provide a manufacturing method for molding a hollow body by DSI molding, which is advantageous in reducing cost while preventing resin leakage. It is to provide.

  In order to achieve the above object, the present invention provides two semi-hollow bodies having a semi-hollow semi-hollow portion having an opening and a joint provided on the entire periphery of the opening by primary molding. The two semi-hollow portions are formed into a hollow portion by combining the joint portions of the two semi-hollow bodies by secondary molding, and an inner wall located on the hollow portion side and the inner wall are located between the joint portions. The joining portions of the two semi-hollow bodies are joined by filling molten resin into a joining passage extending over the entire length of the edge of the opening formed including an outer wall facing the inner wall. Filling the passage with molten resin is a manufacturing method for forming a hollow body by DSI molding performed by injecting molten resin into the joining passage from an injection port provided in the outer wall, Inside the joining passage at the location of the opposing inner wall A thick portion bulging toward the injection port is provided, and the thick portion is positioned on an extension of the center line of the injection port, and a central portion that maximizes the thickness of the inner wall; And including two inclined surfaces that are connected to both sides of the central portion and gradually decrease the thickness of the central portion as the distance from the central portion increases along the extending direction of the joining passage. Features.

In the present invention, when the molten resin is injected from the gate of the mold through the injection port to the joining passage in the secondary molding, the molten resin hits the thick part and is guided by the two inclined surfaces to leave the thick part. It flows in the joining passage in the direction.
In this case, the thick portion has a larger heat capacity than the other inner wall portions, and therefore, without increasing the number of parts and man-hours, the generation of holes in the inner wall portion facing the injection port can be suppressed, and the internal space This is advantageous in preventing resin leakage to the side.

It is the perspective view which fractured | ruptured some hollow molded articles 10 manufactured with the manufacturing method of this Embodiment. 2 is an enlarged perspective view of a joint portion 14 of a hollow molded article 10. FIG. FIG. 6 is a cross-sectional view showing a joint portion 14. It is sectional drawing which shows the state of the junction part 14 when the molten resin 34 is inject | emitted. It is explanatory drawing which shows an experimental result.

Hereinafter, embodiments of the manufacturing method of the present invention will be described with reference to the drawings.
The present invention is applied to a hollow molded product made of synthetic resin molded by DSI molding, and the shape of the hollow molded product is variously provided from a complicated shape to a simple shape, Although contemplated, the present invention is applicable to all of them.
As shown in FIG. 1, the hollow molded article 10 includes two semi-hollow bodies 18 having a semi-hollow semi-hollow portion 14 having an opening 12 and a joint portion 16 provided on the entire circumference of the edge of the opening 12. It is composed of
By joining the joining portions 16 of the two semi-hollow bodies 18, the semi-hollow portions 14 become hollow portions, and an internal space 20 is formed inside them.
The joint portion 16 of the pair of semi-hollow bodies 18 has a recess 22, and a joining passage 24 is formed over the entire length of the opening 12 by combining the joint portions 16.

As shown in FIG. 2, the joining passage 24 is formed including an inner wall 26 positioned on the hollow portion side (inner space 20 side) and an outer wall 28 facing the inner wall 26.
Further, as shown in FIG. 1, by joining the joining portions 16, an injection port 30 for injecting the molten resin 34 to the joining passage 24 is joined to the outer wall 28 at the same time as the joining passage 24 is formed. A plurality of the passages 24 are formed at intervals in the extending direction of the working passage 24.
The molten resin is injected from the gate 32 of the mold through the injection port 30 into the bonding passage 24, whereby the bonded portion 16 is bonded, and the hollow molded article 10 made of synthetic resin is configured.
1 and 2, reference numeral 34 indicates a molten resin injected and filled in the joining passage 24.

Next, the manufacturing method will be described. In the DSI molding, in the primary molding, two semi-hollow bodies 18 having the joints 16 at the edge of the opening 12 are injection molded.
In the secondary molding, the joining portions 16 of the two semi-hollow bodies 18 are combined, and the molten resin 34 is injected into the joining passage 24 formed in the joining portions 16 to join the joining portions 16 together.

As described above, since the temperatures of the two semi-hollow bodies 18 to which the joint portions 16 are combined in the secondary molding are high and the resin is not completely cured, the joint passage 24 facing the injection port 30 The wall portion is easily melted by the amount of heat of the molten resin 34 injected from the gate 32.
Therefore, in the present embodiment, as shown in FIG. 3, in the primary formation, a thick portion that bulges toward the injection port 30 in the joining passage 24 at the location of the inner wall 26 facing the injection port 30. 36 is provided.
In order to facilitate the flow of the molten resin 34, the thick portion 36 is formed by maximizing the thickness of the central portion 36A and gradually decreasing the thickness as the distance from the central portion 36A increases.
That is, the thick portion 36 is located on an extension of the center line of the injection port 30 and is connected to both sides of the center portion 36A and the center portion 36A that maximizes the thickness of the inner wall 26. And the two inclined surfaces 36B that gradually decrease the thickness of the center portion 36A as the distance from the center portion 36A increases.
The end portions in the direction away from the central portion 36A of the two inclined surfaces 36B when viewed from the injection port 30 when viewed from the bonding passage 24 are located outside the outline of the injection port 30, and the molten resin 34 injected from the injection port 30. Is received by the thick portion 36.

In the present embodiment, as shown in FIG. 3, the angle θ at which each inclined surface 36B is inclined with respect to the inner wall 26 is set to 10 degrees, and the flow of the molten resin 34 injected from the injection port 30 is facilitated. Yes.
Further, the central portion 36A of the thick portion 36 is preferably bulged with a dimension of ½ or less of the distance between the inner wall 26 and the outer wall 28 in order to facilitate the flow of the molten resin 34.
Each inclined surface 36B may be formed as a flat surface, or may be formed as a concave curved surface.

In the present embodiment, as shown in FIG. 4, when the molten resin 34 is injected from the mold gate 32 into the joining passage 24 through the injection port 30 in the secondary molding, the molten resin 34 has a thick portion 36. In this case, the fluid flows in the joining passage 24 in a direction away from the thick portion 36 while being guided by the two inclined surfaces 36B.
In this case, the thick portion 36 has a larger heat capacity than the other inner wall 26 portion.
Accordingly, even if the wall portion of the thick portion 36 is melted by the molten resin 34 by the molten resin 34 from the injection port 30 and flows out into the joining passage 24, the hole of the inner wall 26 facing the injection port 30 is not formed. Generation can be suppressed.
Therefore, it is advantageous in preventing resin leakage to the inner space 20 without increasing the number of parts and man-hours.

Next, experimental results will be described.
As shown in FIG. 3, the inner diameter D of the joining passage 24 is 4 mm, the thickness T of the inner wall 26 and the outer wall 28 is 1.5 mm, and the height (thickness) H of the central portion 36A of the thick portion 36 is 2. The experiment was conducted by setting the angle θ at which the inclined surface 36B is inclined with respect to the inner wall 26 to 10 degrees, and 0.5 mm, 3 mm, 3.05 mm, 3.1 mm, 3.4 mm, and 3.5 mm.
The experimental results are shown in FIG.
In the comparative example in which the height was 2.5 mm, resin leakage to the inner space 20 side was observed.
Moreover, in Examples 1-5 which made height 3mm, 3.05mm, 3.1mm, 3.4mm, 3.5mm, the resin leak to the internal space 20 side was not seen.
In Examples 3, 4, and 5 in which the height is 3.1 mm, 3.4 mm, and 3.5 mm, the wall surface on the inner space 20 side is deformed at the location of the inner wall 26 where the thick portion 36 is located. However, in Examples 1 and 2 in which the height was 3 mm and 3.05 mm, deformation of the wall surface on the inner space 20 side was observed at the location of the inner wall 26 where the thick portion 36 is located.
Although the above experimental results vary depending on the resin used, injection pressure, angle θ, etc., the height (thickness) H of the central portion 36A of the thick portion 36 is set to the thickness of the inner wall 26 and the outer wall 28. When it is set to 2 times to 2.05 times or more of T, it is advantageous in preventing resin leakage to the internal space 20 side.

  DESCRIPTION OF SYMBOLS 10 ... Hollow molded article, 12 ... Opening, 14 ... Semi-hollow part, 16 ... Joint part, 18 ... Semi-hollow body, 24 ... Passage for joining, 26 ... Inner wall, 28 ... Outer wall, 30 ... injection port, 34 ... molten resin, 36 ... thick part, 36A ... center part, 36B ... inclined surface.

Claims (4)

Forming two semi-hollow bodies having a semi-hollow semi-hollow portion having an opening and a joint provided on the entire periphery of the edge of the opening by primary molding,
By the secondary molding, the two semi-hollow bodies are joined together to form two semi-hollow parts as hollow parts, and the inner wall located on the hollow part side is opposed to the inner wall between the joint parts. And joining each joint part of the two semi-hollow bodies by filling a molten resin into a joining passage extending over the entire length of the edge of the opening formed including the outer wall.
Filling the bonding passage with the molten resin is a manufacturing method of forming a hollow body by DSI molding performed by injecting molten resin into the bonding passage from an injection port provided in the outer wall,
In the location of the inner wall facing the injection port, a thick portion bulging toward the injection port in the bonding passage is provided,
And the thick part is located on the extension of the center line of the injection port, the central part is the maximum thickness of the inner wall, and is connected to both sides of the central part in the extending direction of the joining passage. And two inclined surfaces that gradually reduce the thickness of the central portion as the distance from the central portion increases.
The manufacturing method which shape | molds a hollow body by DSI shaping | molding characterized by the above-mentioned. The angle at which each inclined surface is inclined with respect to the inner wall is 10 degrees.
The manufacturing method which shape | molds a hollow body by DSI shaping | molding of Claim 1. The central portion of the thick portion is bulged with a dimension of ½ or less of the distance between the inner wall and the outer wall.
A manufacturing method for forming a hollow body by DSI molding according to claim 1 or 2. An end portion in a direction away from the central portion of the two inclined surfaces when looking at the joining passage from the injection port is located outside the outline of the injection port.
The manufacturing method which shape | molds a hollow body by DSI shaping | molding of Claim 1.

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