JPH07195452A - Plastic-molding die and its molding - Google Patents

Abstract

PURPOSE:To obtain a plastic molding die having a cavity with ideas put into shaping corner parts so that occurrence of a sink mark or a collapse of a shape in a molded piece can be prevented even if a draft is determined as small as possible and to obtain a molded piece thereby. CONSTITUTION:A corner part surface 21 of a cavity is formed into such a shape that a top of a corner part of a molded piece surrounded by three faces 3 can be truncated by one plane that is inclined with respect to each of the three faces.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a plastic molding die used for injection molding and the like and a molded product thereof.

[0002]

2. Description of the Related Art Conventionally, when a plastic molded product is molded by injection molding or the like, it is necessary to provide a cavity of a plastic molding die with a draft of, for example, about 3 degrees. In particular, as shown in FIG. 5, the corners 22 of the box-shaped molded product 1 form their vertices in the three planes 3 that are adjacent to each other at an angle of approximately 90 degrees, so that during the cooling process. When the resin crystallizes or heat shrinks in the cavity of the molding die 6 as shown in FIG. 6, the resin closely adheres to the inner die surface 3A,
Since a large amount of force is required for die cutting,
There is a risk that the molded product will be partially deformed (particularly the portion corresponding to the corner 22A of the cavity), and in order to avoid this, a necessary and sufficient draft is applied to the surface in the direction in which the resin adheres. There must be.

[0003]

However, in the conventional shape of the cavity corner portion 22A, each surface 3A requires a gradient of at least about 3 degrees, and therefore, there is a difference between the root where the gradient begins and the tip where the gradient ends. , The wall thickness of the molded product is considerably different. For example, in the case of a large molded product, set the shape of the cavity so that the thickness of the root is considerably thick to guarantee the wall thickness of the tip. Must. Therefore, the cooling time in the mold is set on the basis of the thick portion of the molded product, which causes a drawback that the working time becomes long.
Further, there is a difference in the cooling rate between the root and the tip, which may cause local sink marks and impair the appearance of the molded product.

Therefore, as a result of earnest research, the present inventor found that
It has been found that most of the causes of difficulty in taking out a molded product from a molding die at the corners surrounded by the above-mentioned three surfaces are in the early stage of the moment when the molded product is peeled off from the mold surface, and the following inventions are provided. Was done.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a plastic molding die having a cavity in which the shape of the corner is devised so as not to cause sink marks or deformation of the molded product even if the draft is made as small as possible, and the molding thereof. It is intended to provide goods.

[0006]

Therefore, in the present invention,
The apex of the corner of the molded product surrounded by the three faces is cut into one plane, and the corner surface of the cavity is formed into a shape in which the above plane is inclined with respect to each of the three faces. A plastic molding die characterized in that it is used for injection molding and the like.

In the molded article of the present invention, the corners of the molded article surrounded by the three surfaces are cut by one plane, and the plane is inclined with respect to each of the three surfaces. Corners are formed.

[0008]

As a result, it is possible to reduce the initial mold releasing force at the corners surrounded by the three surfaces even if the draft of the molding die, which requires the most take-out force for the molded product, is considerably reduced. Became. That is, it is expected that when the molded product shrinks, the vertices surrounded by the three surfaces undergo shrinkage in all three directions, so that a very large stress is concentrated there. In the above shape, the vertices are cut off in one plane, which results in the stress being dispersed.

Therefore, the molded product molded by the molding die of the present invention can have almost the same thickness because the difference in the thickness between the root and the tip is small due to the reduced draft. Therefore, there is no sink mark or shape loss as in the conventional case, and appearance defects can be avoided. Further, since the wall thickness is not unnecessarily increased, the cooling time of the molded product in the molding die can be shortened.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on each embodiment shown in FIGS. In the first embodiment of the present invention, a molded product 1 such as a copying machine exterior chassis as shown in FIG. 1 is molded by a molding die 5 as shown in FIG. Here, the apex of the corner of the molded product 1 surrounded by three surfaces 3 that are orthogonal to each other at about 90 degrees is cut into one plane 2, and the plane 2 is inclined with respect to each of the surfaces 3. The corner surface 2 which is a cut portion of the three mold surfaces 3A forming the cavity of the molding die 5 so as to have the shape of
1 is formed.

Thus, the molded product 1 has the inner corner portion 2 surrounded by the three surfaces, so that the stress generated by the shrinkage during cooling can be dispersed without being concentrated at the apex. Therefore, the molded product 1 molded by the molding die 5 is
As the draft is reduced, the difference in wall thickness between the root and the tip is small, so that the wall thickness can be made almost the same. Therefore, there is no sink mark or shape loss as in the conventional case, and appearance defects can be avoided. Further, since the wall thickness is not unnecessarily increased, the cooling time of the molded product in the molding die can be shortened.

In the molded product 1 shown in FIG. 3, the inner corner 23 is
The mold 5 corresponding to the design extending to the open edge of the box has a corner surface 24 which is a cut portion of the three mold surfaces 3A. The function of the molding die 5 at the time of molding is substantially the same as that of the first embodiment described above.

[0013]

As described above, according to the present invention, the apex of the corner of the molded product surrounded by the three surfaces is cut into one plane,
By forming the corner surface of the cavity in a shape in which the flat surface is inclined with respect to each of the three surfaces, the draft of the molding die that requires the most take-out force can be obtained for the molded product. Even if it is considerably reduced, the initial mold releasing force at the corner surrounded by the three surfaces can be reduced. Therefore, the molded product molded by the molding die of the present invention can have almost the same wall thickness because the draft has a small draft and the thickness difference between the root and the tip is small. Therefore, there is no sink mark or shape loss as in the conventional case, and appearance defects can be avoided. Further, since the wall thickness is not unnecessarily increased, the cooling time of the molded product in the molding die can be shortened. Furthermore, the small slope greatly expands the freedom of product design.

[Brief description of drawings]

FIG. 1 is a perspective view of a shape of a main part of a molded product showing a first embodiment of the present invention.

FIG. 2 is likewise a perspective view showing the shape of the main part of the molding die.

FIG. 3 is a perspective view of a shape of a main part of a molded product showing a second embodiment of the present invention.

FIG. 4 is likewise a perspective view showing the shape of the main part of the molding die.

FIG. 5 is a perspective view of a shape of a main part of a molded product showing a conventional example.

FIG. 6 is a perspective view showing a shape of a main part of a conventional molding die.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molded product 2 Flat surface 21, 23 Corner surface 22 3 Vertex surrounded by 3 surfaces 3 Surface surrounding the vertex 3A Mold surface 5 Mold

Claims (2)

[Claims] 1. The apex of a corner of a molded product surrounded by three surfaces is 1.
Cut into two planes, and for each of the above three planes,
A plastic molding die characterized in that a corner surface of a cavity is formed in an inclined shape. 2. The apex of a corner of a molded product surrounded by three surfaces is 1.
Cut into two planes, and for each of the above three planes,
A plastic molded product characterized by forming a corner in an inclined state.