KR101142900B1 - Double injection mould for the plastic part with the minimized residual stress distributions - Google Patents

Abstract

The double injection mold of the molded article with the minimum residual stress of the present invention comprises a first mold supported on the first fixing plate, a second mold coupled to and separated from the first mold to form a cavity for the molded article, and Guide means for guiding and detaching the second mold is provided, and the cavity forming portion of the first and second molds is provided to prevent residual stress from occurring during the injection and cooling of the resin due to the difference in thickness of the molded article. Protruding cores are formed.

Description

 Double injection mold for the plastic part with the minimized residual stress distributions}

The present invention relates to an injection mold, and more particularly, to a double injection mold of a molded article is minimized the residual stress caused by the thickness difference during the injection molding of the molded article.

In order to mold an injection molded product, resin is injected into a cavity of a double injection mold, and the resin tends to cool rapidly in the mold and solidify. In addition, there is a problem in that the molded product is deformed after the injection of the resin due to the stress remaining in the injection molded product due to the cooling rate difference according to the thickness difference of the injection product.

In view of these problems, a molding method has been proposed that shortens the cycle time of the molding process and reduces stress by forming a mold by heating the mold before filling and by supplying a heat exchange medium to the heat medium passage in the mold to cool the molded article.

However, even by injection molding using such a molding method, post-deformation due to residual stress of a relatively thin, long or wide molded product cannot be completely removed.

In particular, the front panel of the plasma display device has a lattice structure having a thin and long rim covering the edge of the plasma display device of 50 to 60 inches, and thus is easily cooled during molding of the molded product, There is a problem that deformation occurs after.

 Japanese Patent No. 3601463 discloses an injection method for reducing deformation or stress caused by a difference in cooling temperature. The disclosed injection method heats the molding space above the glass transition point temperature where the flowability of the resin material is good, fills the cavity with molten resin at a slow injection rate of 15 cm 3 / sec or less, and after filling the cavity surface of the mold The molded article is solidified by lowering below the glass transition point temperature, and the mold is opened to take out the molded article.

This molding method minimizes deformation during injection and cooling of the resin but cannot fundamentally solve the generation of stress due to cooling of the resin injected into the cavity.

In Japanese Patent Application Laid-Open No. 2004-322597, a method for manufacturing an injection molded article is a method for manufacturing an injection molded article using a three temperature control device, a heat medium supply means, a heat medium recovery tank, and the like to supply three types of heat medium of high temperature, medium temperature, and low temperature. Disclosed is a multistage cooling structure. However, this method has a problem that it takes a lot of time when cooling the molded article formed by the resin is injected into the cavity can not improve the productivity, there is a problem that post-deformation occurs in the molded article after molding.

The present invention has been made in view of the above-described problems, and an object thereof is to provide a double injection mold of a molded article having a minimum residual stress that can suppress generation of residual stress due to a thickness difference or a cooling rate difference.

Another object of the present invention is to provide a double injection mold of a molded article after the molding of the molded article, the residual stress is minimized to prevent post deformation.

In order to achieve the above object, the double injection mold of the molded article having the minimum residual stress of the present invention includes a first mold supported on the first fixing plate, a second mold coupled to and separated from the first mold, and forming a cavity for the molded article. It is provided with a guide means for guiding and detaching the first mold and the second mold,

The cavity forming portions of the first and second molds are formed with protruding cores for preventing residual stress from occurring in the molded article during injection and cooling of the resin due to the difference in thickness of the molded article.

In the present invention, the protruding core may be formed differently in width and protruding height according to the molding thickness difference of the molded article.

The double injection mold of the molded article with the minimum residual stress according to the present invention can minimize the generation of stress due to resin injection or cooling due to the difference in the thickness of the molded article, and can further prevent post deformation of the molded article after injection molding. have.

1 is a perspective view showing a part of a molded article molded by a double injection mold,
2 is a cross-sectional view of a double injection mold of a molded article minimized residual stress according to the present invention,
Figure 3 is a perspective view showing a double injection mold.

Figure 1 shows an example of a molded article for molding using a double injection mold according to the present invention, Figures 2 and 3 shows the injection mold of the molded article minimized the residual stress according to the present invention.

As shown in FIG. 1, the molded part 100 may have a difference in thickness according to each part, or, in the case of a thin and long molded part such as a front panel of a plasma display, a residual stress in the molded part due to a difference in cooling rate during injection molding. It remains. Such residual stress causes deformation after molding. Since at least one side of the molded product 100 is formed with recessed grooves 101 for removing residual stress during injection molding, post deformation may be prevented. The inlet groove 101 may vary in width and length by the difference in thickness of each part of the molded article.

2 and 3 show examples of injection molds having a minimum residual stress according to the present invention for molding such a molded article.

Referring to the drawings, a double injection mold of a molded article having a minimum residual stress is combined with the first mold 20 supported by the first fixing plate 11 and the first mold 20 to provide a cavity for injection molding of a product. A second mold 30 forming 12, and guide means 50 for guiding the first mold 20 and the second mold 30 to be coupled and separated (mold-bonded or mold-separated). . And heating and cooling means for heating the first mold 20 when the resin is injected into the cavity 12 for injection molding, and cooling the first mold 20 when curing the resin injected into the cavity 12 ( 60).

The double injection mold according to the present invention configured as described above will be described in more detail for each component as follows.

The first fixing plate 11 and the first mold 20 are provided with a sprue bush 14 for injecting resin into the cavity 12, and the sprue bush 14 and the cavity 12 are connected to each other. The runner 15 is installed. Injection of the resin through the sprue bush is accomplished by pressing the molten resin by the injection machine.

On the other hand, it is preferable that the first and second molds 20 and 30 are not relatively large in calories. The shape of the cavity 12 formed in the first and second molds 20 and 30 may be formed in various shapes according to the shape of the product to be molded. In addition, a protruding core 200 is formed on an inner surface of the cavity of the first and second molds 20 and 30 to prevent concentration of stress in a molded article formed by resin injection into the cavity.

The protruding core 200 may be formed at the thick portion of the molded article or at the interior of the flattened portion or at the gap between the thickness of the molded article and the boss forming portion of the molded article.

The protruding core 200 has a thickness and a height of the molded article may vary according to the generation of cooling stress, and the protruding core 200 may be continuously or discontinuously formed.

The heating and cooling means (60) is for heating the first mold (20) during molding of the product and for cooling while the resin is cured in the state where molding is completed, and for injecting the resin into the cavity (12) for molding. A cooling unit 61 for cooling the mold 20 can be provided.

As shown in FIG. 2, the cooling unit 61 includes a storage tank 62 in which a heat exchange medium is stored, a connection pipe 63 connecting the storage tank 62 to an injection mold water jacket, and the connection pipe ( It may consist of a pump 64 installed in the 63).

Referring to the action of the double withdrawal mold of the molded article minimized residual stress according to the present invention configured as described above are as follows.

First, the first and second molds 20 and 30 are molded for injection. At this time, the first and second molds forming the cavity 12 may be heated to smoothly inject the resin. In this state, a resin is molded by molding the product into the cavity 12 to mold the product.

As described above, the stress is generated by the difference in the cooling rate of the resin injected into the cavity 12 in the process of forming the molded article, the protruding core 200 in the thick portion or planarization portion, the region of the thickness change is severe Since is formed, it is possible to reduce the stress generated during cooling of the molded article.

This can eliminate residual stress remaining in the molded article after molding, thereby preventing post deformation of the molded article. That is, since the bead is formed by the protruding core in the relatively thin and long molded article, the deformation of the molded article can be prevented from being deformed by the residual stress due to the thickness difference. In particular, the bead can be minimized because the width, length and depth are formed differently depending on the degree of stress caused by the difference in thickness.

 While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention.

Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Removing residual stress by using the protruding core of the double injection mold of the molded article minimized residual stress according to the present invention is widely applicable to various molded articles having a thickness difference at each site. To prevent deformation of the molded article, namely the front panel, transfer molding method, compression molding method, reactive molding method, blow molding method, thermoforming method, injection compression method, local heat-pressing method, gas press method, gas assist method, blow molding method It is also applicable to molded products using sandwich molding method, two-color molding method, in-mold molding method, push-pull molding method, and high speed molding method.

20; 1st mold
30; 2nd mold
200; Protruding core

Claims (2)

A first mold supported by the first fixing plate, a second mold coupled to and separated from the first mold to form a cavity for the molded article, and guide means for guiding and separating the first mold and the second mold from each other; Equipped with
Protruding cores are formed in the cavity forming portions of the first and second molds to prevent residual stress from occurring in the molded article when the resin is injected and cooled due to the difference in thickness of the molded article.
The protruding core is a double injection mold of a molded article minimized residual stress, characterized in that formed continuously or discontinuously. delete

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