JPH074839B2 - Injection-molded article having undercut portion and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to an injection-molded article having an undercut portion and a method for producing the same.

<< Conventional Technology >> The conventional method for manufacturing a molded article having an undercut portion is
As shown in FIG. 3, a molding material is placed in a cavity formed by a fixed die 1 having a slide 3 driven by a hydraulic cylinder 2 and a movable die 6 having a slide core 5 interlocking with an angular pin 4 of the fixed die 1. A molded product 7 is molded by injection.

In this case, the slide 3 forms a curved surface 8a for molding the undercut portion 9 of the molded product 7 following the shape of the molding portion 8 of the fixed mold 1. Occasionally, the molding surface of the slide core 5 forms a curved surface 5a for molding the undercut portion 9 so as to face the curved surface 8a of the slide 3 and is fixed by the locking block 12 when the mold is closed.

When the molded product 7 is injection-molded and then released, when the movable mold 6 is lowered after pulling up the slide 3 to separate from the molded product 7, the slide core 5 moves in the direction of the arrow along the angular pin 4. At the same time, the movable die 6 descends following the movable die 6, and as the movable die 6 descends, the mold release also increases.

<< Problems to be Solved by the Invention >> However, in the structure of the mold having such a complicated shape, the mold processing cost is high because the mold processing degree is high and the processing difficulty is high, and the slide 3 is used. And Angular Pin 4
Therefore, there are problems that the strength of the mold is weakened and the mold needs to be reinforced, and the durability of the mold is reduced.

Further, if the surface of the molded product 7 has a texture pattern, there is a problem that a nesting line of the slide 3 appears on the texture surface 10 to cause a quality defect.

The present invention has been made in view of the above problems, and one of the objects thereof is to provide an injection-molded article having an undercut portion without a nest line on a grain surface.

Another object of the present invention is to provide a method of manufacturing an injection-molded article having an undercut portion which has a high mold strength and a high mold strength, which reduces mold material costs and processing costs. It is in.

<< Means for Solving the Problem >> In order to achieve the above-mentioned one object, an injection-molded article having an undercut portion of the present invention has an undercut portion, and includes a fixed die, a movable die, and a slide die. An injection-molded product to be molded, having a protrusion inside the tip of the undercut part that slides on the curved surface of the undercut part of the fixed mold at the time of mold release, and molds this protrusion to a shape higher than the embossed depth. Is characterized by.

Further, in order to achieve another object, a method of manufacturing an injection-molded article having an undercut portion of the present invention is such that an undercut portion is formed in a fixed die and a slide core that slides on a movable die. In a method of manufacturing an injection-molded product having an undercut portion, which is formed by injecting a molding material into a cavity composed of a movable mold and a slide core, a fixed depth is formed inside the base portion of the undercut part of the fixed mold. Providing a deep recess, after injection molding, slide the slide core outward to move the movable mold, and at the same time slide the projection of the molded product molded by the recess on the curved surface of the undercut part of the fixed mold. It is characterized in that an undercut portion of the molded product is released by elastically deforming the molded product.

<< Operation >> With such a configuration, the injection-molded product having the undercut portion of the present invention becomes an injection-molded product in which the mold release of the molded product is improved and the undercut portion having no nesting line on the grain surface is provided.

Further, in the method for producing an injection-molded product having an undercut portion of the present invention, after injection molding, the tip of the undercut portion of the molded product is formed in the recess formed inside the base portion of the undercut portion of the fixed mold. The protrusion located at is formed. After injection molding, slide the slide core to the outside and then lower the movable die.The protrusion of the above-mentioned molded article slides on the curved surface of the undercut part of the fixed die and is pushed outward, and the molded article becomes elastic. By deforming, the undercut part of the molded product is released from the undercut part of the fixed mold, and the mold release of the movable mold is facilitated.

Therefore, since the fixed mold does not require an auxiliary member having a complicated shape such as a slide or an anglar pin, the mold has a low degree of processing and is easy to process, and the strength and durability of the mold are not deteriorated. As a result, there is no need for extra material costs such as mold reinforcement and processing costs, and costs are reduced.

Further, a slide nest line does not appear on the surface of the molded product, and a molded product of good quality can be obtained.

<< Embodiment >> An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a cross-sectional view of an injection-molded product having an undercut portion according to the present invention and a mold when the mold is closed, and FIG. 2 is a cross-sectional view of the same injection-molded product and a mold when the mold is released.

In the figure, 1 is a fixed type, 5 is a slide core, 6 is a fixed type, and 9 is an undercut portion.

The fixed die 1 includes a mating surface 1a and a molding portion 8, and the molding portion 8
The surface of (1) maintains the shape along the surface of the molded product (7), and the textured surface (10) is formed on the entire surface. Further, a curved surface 8a is formed at one end of the molded portion 8 along the shape of the undercut portion 9 of the molded product 7. A recess 12 is provided inside the root of the curved surface 8a.

The movable mold 6 is provided with a mating surface 6a and a molding portion 11, and the surface of this molding portion 11 maintains the shape along the back surface of the molded product 7. Also movable type 6
A slide surface 3 on which a slide core 5 slides and a contact surface 4 that abuts on a slide die are formed on the.

Inside the slide core 5, a curved surface 5a is formed along the shape of the undercut portion 9 of the molded product 7. Further, the slide core 5 is driven by the hydraulic cylinder 2, and the movable die 6
It slides on the slide surface 3 and contacts the contact surface 4 when the mold is closed.

Next, the operation will be described. After the movable die 6 is raised with respect to the fixed die 1 to bring the mating surfaces 1a and 6a of both dies into alignment with each other, the hydraulic cylinder 2 is driven to slide the slide core 5 to make a hit. Surface 4
When all the molds are brought into contact with each other, the mold is closed, and at this time, a predetermined gap for injection molding the molded product 7 is maintained between the fixed mold 1, the movable mold 6, and the slide core 5. Become.

Next, when a molding material is injected from a predetermined injection port, a molded product 7 is molded in the above-mentioned gap and the curved surface of the fixed mold 1 described above.
A projection 14 continuous with the undercut portion 9 of the molded product 7 is formed at the root portion of 8a.

After the injection molding is completed, the slide core 5 is slid in the direction of the arrow A as shown in FIG. 2 so that the required space is maintained between the curved surface 5a of the slide core 5 and the molded product 7. . Next, when the movable mold 6 is lowered, the protrusion 14 formed at the tip of the undercut portion 9 of the molded product 7 is recessed in the fixed mold 1.
When it deviates from 12, it slides on the curved surface 8a of the undercut portion 9 and is expanded and elastically deformed in the direction of arrow B. At this time, since the protrusion 14 of the molded product 7 is formed higher than the embossed depth, the embossed surface 10 is the curved surface of the undercut portion of the fixed mold 1.
It is completely separated from 8a and is not rubbed by the curved surface 8a of the undercut portion 9 and can be easily released from the mold.

Further, when the movable mold 6 descends and the mold release is completed, the protrusion 14 returns to its original position by elasticity and restores the molded product 7 to a predetermined shape.

Therefore, in injection molding of a molded product having an undercut portion provided with a pattern such as grain, a molded product of good quality can be obtained by the above method without damaging the grain surface.

Further, also in the injection molding of a molded product having an undercut portion without a grain or the like, a molded product of good quality can be obtained by the above method.

<< Effects of the Invention >> As described above, the injection-molded article having the undercut portion of the present invention is an injection-molded article having an undercut portion and molded by a fixed die, a movable die, and a slide die. The inside of the tip of the undercut part is provided with a protrusion that slides on the curved surface of the undercut part of the fixed mold at the time of mold release, and this protrusion is formed in a shape higher than the depth of the embossing. As a result, when an injection-molded product having an undercut portion is injection-molded, the mold release of the molded product is improved, and an injection-molded product having an undercut portion with no nesting line on the grain surface is obtained.

Further, in the method for producing an injection-molded product having an undercut portion of the present invention, an undercut portion is formed in a fixed die and a slide core that slides on the movable die, and the fixed die, the movable die, and the slide core are In a method of manufacturing an injection-molded product having an undercut portion that is formed by injecting a molding material into a cavity, a recess deeper than the grain depth is provided inside the root portion of the undercut portion of the fixed mold, and injection molding is performed. After that, the slide core is slid outward, and at the same time as the movable mold moves, the projection of the molded product formed by the recess is slid on the curved surface of the undercut part of the fixed mold to elastically deform the molded product. Since the undercut part of the molded product is made to be released from the mold, after injection molding, the recess formed inside the base part of the undercut part of the fixed mold is not formed. Projections located at the top of the undercut portion of the article is to be molded. After injection molding, slide the slide core to the outside and then lower the movable die.The protrusion of the above-mentioned molded product slides on the curved surface of the undercut part of the fixed mold and is pushed outwards to form the molded product. By elastically deforming, the undercut portion of the molded product is released from the undercut portion of the fixed die, and the release of the movable die becomes easy.

Therefore, the fixed mold does not require auxiliary members with complicated shapes such as slides and angular pins, so the mold has a low degree of processing, which facilitates processing and also reduces the strength and durability of the mold. No additional material costs such as mold reinforcement and processing costs are required, and costs are reduced.

Further, a slide nest line does not appear on the surface of the molded product, and a molded product of good quality can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an injection-molded product having an undercut portion according to the present invention and a mold when the mold is closed, FIG. 2 is a cross-sectional view of the same injection-molded product and a mold when the mold is released, and FIG. It is sectional drawing of the conventional injection molded product and the metal mold | die at the time of mold closing. 1 ... Fixed type, 5 ... Slide core, 6 ... Movable type, 7 ... Molded product, 9 ... Undercut part, 13 ... Recessed part, 14 ... Protrusion.

Claims (2)

[Claims] 1. An injection-molded product having an undercut portion, which is molded by a fixed die, a movable die, and a slide die, wherein the undercut portion of the fixed die is inside the tip of the undercut portion when the die is released. An injection-molded product having an undercut portion, which is characterized in that a protrusion that slides on the curved surface of is provided, and the protrusion is molded into a shape higher than the embossed depth. 2. An undercut portion is formed in a fixed die and a slide core that slides on the movable die, and a molding material is injected into a cavity formed by the fixed die, the movable die, and the slide core for molding. In the method of manufacturing an injection-molded article having an undercut portion, a concave portion deeper than the grain depth is provided inside the root portion of the fixed mold undercut portion, and after injection molding, the slide core is slid outward, Simultaneously with the movement of the movable mold, the projection of the molded product formed by the recess is slid on the curved surface of the undercut portion of the fixed mold to elastically deform the molded product to release the undercut portion of the molded product. A method for manufacturing an injection-molded article having an undercut portion, which is characterized by the above.