JP2001225355A - Injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the appearance of a molded article, in injection molding the molded article wherein a cylindrical boss part is provided on the rear surface of a plate part having a smooth surface using a synthetic resin containing a brilliant material, by avoiding such a state that a large restriction is applied to the shape of the molded article or a mold. SOLUTION: A synthetic resin is injected in the space between a second mold 14 wherein the tip of a pin 25 is projected from the rear surface forming surface 23 of to mold and a first mold 13 to mold a first semi-molded article 6 wherein a boss part 9 is integrally projected from the rear surface of a thin- walled plate part 11 and, subsequently, a synthetic resin is injected in the gap between the surface of the thin-walled plate part 11 and the surface forming surface 22 of the first mold 13 to mold a plate-shaped second semi-molded article to integrally bond the same to the surface of the thin-walled plate part 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for molding a molded product in which a cylindrical boss is provided on the back surface of a plate having a smooth surface, using a synthetic resin containing a glittering material.

[0002]

2. Description of the Related Art When such a molded product is molded at a time by injecting a molten resin into a mold, the molten resin flowing ahead of the boss portion and the molten resin flowing behind the other portion are merged. Flow marks and weld lines may be formed on the surface of the molded product and impair the appearance of the molded product.In particular, in the case of synthetic resins containing glittering materials such as aluminum foil, glass beads and pearl mica, When the flow of the resin is relatively slow, the flow mark and the weld line tend to be formed on the surface of the molded product.

A technique for preventing the occurrence of such flow marks and weld lines is disclosed in, for example, Japanese Patent Laid-Open No. 4-3751.
No. 6, JP-A-8-276453, and the like, and in these prior arts, a gas pressure is applied to a portion corresponding to a boss portion.

[0004] In addition, heat is generated in the molded product at a portion corresponding to the boss portion, so that the molded product is difficult to cool, and the surface of the molded product may have sink marks.

A technique for preventing the occurrence of such sink marks is as follows.
For example, JP-A-5-278039 and JP-A-7-3
No. 08975, which is already known,
In 78039, a large number of nests or the like made of a material having a lower thermal conductivity than the material of the mold are provided in the mold at portions where sinks are likely to occur.
In Japanese Patent Application Laid-Open No. 5 (1999) -2005, means for pressing the molten resin is provided in the mold.

[0006]

However, in order to prevent the occurrence of flow marks and weld lines, Japanese Patent Application Laid-Open No.
According to the techniques disclosed in Japanese Patent Application Publication No. 37516/1996 and Japanese Patent Application Laid-Open No. Hei 8-276453, it is difficult to apply a required amount of gas pressure to a required position. It is difficult to press-fit even if the pressure is considerably increased,
Significant restrictions are imposed on the shape of the molded product and the mold design.

In order to prevent the occurrence of sink marks, the techniques disclosed in the above-mentioned JP-A-5-278039 and JP-A-7-308975 are provided with a nest or a means for pressing the molten resin. In addition, a great restriction is imposed on the mold design, and the cost is increased.

The present invention has been made in view of such circumstances, and provides an injection molding method capable of improving the appearance of a molded article by avoiding imposing great restrictions on the shape and the mold of the molded article. The purpose is to do.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, a plate having a smooth surface and a cylindrical boss projecting from a back surface of the plate are integrally formed. A molded product having a surface forming surface corresponding to the surface of the plate portion, a back surface forming surface corresponding to the back surface of the plate portion, and a back surface forming surface corresponding to the outer surface of the boss portion. A synthetic resin containing a luminous material is injected and molded between the recess provided and the second mold having a pin having a base end connected to the closed end of the recess corresponding to the inner surface of the boss. In the injection molding method, the synthetic resin is injected into a first cavity formed between a second mold and a first mold having a tip of the pin protruding from the rear surface forming surface, thereby being thinner than the plate portion. The thin plate portion and the boss projecting from the back surface of the thin plate portion are integrally formed. First molding the first semi-molded article to
And by injecting the synthetic resin into a second cavity formed between the surface of the thin plate portion and the surface forming surface of the first mold by separating the first and second molds from each other. A second step of forming a plate-shaped second semi-molded product constituting the plate portion in cooperation with the thin plate portion and integrally joining the second semi-molded product to the front surface side of the thin plate portion.

[0010] According to the method of the first aspect,
Even if a flow mark or a weld line is formed on the surface of the thin plate portion in the first semi-molded product, the surface of the thin plate portion is covered with the second semi-molded product. No flow mark or weld line remains on the surface of the molded product. Further, since the tips of the pins for forming the inner surface of the boss protrude from the back surface forming surface of the second mold, it is possible to avoid the occurrence of heat accumulation at the portion corresponding to the boss, and therefore, the Prevents the corresponding part from becoming harder to cool than other parts,
The occurrence of sink marks on the surface of the semi-molded product can be prevented as much as possible, and the influence of the sink marks on the surface of the second semi-molded product covering the surface of the first semi-molded product can be avoided.
As a result, the appearance of the molded product can be improved, and further, since there is no need to apply gas pressure, provide a nest, or provide means for pressing the molten resin, the shape of the molded product and the design of the mold There is no great restriction on the above, and an increase in cost can be suppressed.

[0011] The invention according to claim 2 provides the above-mentioned claim 1.
In addition to the configuration of the invention described in the above, the amount of protrusion of the tip of the pin from the back surface forming surface is set to １ ／ of the thickness of the thin plate portion.
According to such a method,
It is possible to more effectively prevent the surface of the first semi-molded product from sinking while avoiding the thickness of the first semi-molded product at the portion corresponding to the boss portion from becoming too thin.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on one embodiment of the present invention shown in the attached drawings.

1 to 5 show an embodiment of the present invention. FIG. 1 is a perspective view of a molded product, and FIG. 2 is a cross-sectional view of the molded product viewed from a direction along line 2-2 in FIG. FIG. 3 is a longitudinal sectional view of the molding die during execution of the first step, FIG. 4 is a longitudinal sectional view of the molding die corresponding to FIG. 3 before the execution of the second step, and FIG. FIG. 4 is a longitudinal sectional view of the molding die corresponding to FIG. 3 at the time of executing a step.

First, in FIGS. 1 and 2, this molded article 5 is made of AAS or AES containing 0.1 to 7% of a glittering material such as aluminum foil, glass beads and pearl mica.
A first semi-molded product 6 injection-molded with a synthetic resin such as
The first molded product 6 and a second semi-molded product 7 that is injection-molded with the same material are integrally joined, and are formed, for example, in a cylindrical shape on the back surface of a plate portion 8 having a smooth surface. The boss 9 is provided.

The first semi-molded product 6 is formed by integrally forming a thin plate portion 11 thinner than the plate portion 8 of the molded product 5 and the boss 9 protruding from the back surface of the thin plate portion 11. The second half-molded product 7 is injection-molded into a plate shape constituting the plate portion 8 in cooperation with the thin plate portion 11 of the first half-molded product 6, and the thin plate portion is formed. 11 is integrally joined to the surface side.

In order to form such a molded product 5, a molding die 12 as shown in FIG. 3 is used. The molding die 12 includes a fixed die 13 as a first die and a fixed die 13 as a first die. Movable mold 1 as a second mold capable of moving forward and backward with respect to 13
4 is provided.

The fixed die 13 is integrally provided with a projection 15 protruding toward the movable die 14, and the movable die 14 is provided with a fitting recess 16 for fitting the projection 15 so as to be relatively slidable. The fixed mold 13 has the protrusions 15 of the fixed mold 13.
A gate 17 for injecting the molten synthetic resin between the fitting recesses 16 of the movable mold 14; a gate pin 18 for opening and closing the gate 17;
A cylinder 19 for driving the gate pin 18 in the axial direction is provided.

The front end surface of the projection 15 in the fixed die 13 constitutes a surface forming surface 22 corresponding to the surface of the plate portion 8, and the closed end surface of the fitting recess 16 in the movable die 14 is formed on the back surface of the plate portion 8. Is formed on the rear surface forming surface 23 corresponding to the above. Further, the movable die 14 is provided with a concave portion 24 in which a closed end is formed at the tip end of the pin main body 26 fitted and fixed to the movable die 14 so as to open to the back surface forming surface 23.
4 is formed in a shape corresponding to the outer surface of the boss 9. Further, a base end of a pin 25 is integrally connected to a closed end of the concave portion 24, that is, a distal end of the pin main body 26, and the pin 25 is formed in a shape corresponding to the inner surface of the boss portion 9. In addition, the tip of the pin 25 protrudes from the rear surface forming surface 23 by a protruding amount L, and the protruding amount L is ２〜 to ／ of the thickness t1 of the thin plate portion 11 in the first semi-molded product 6.
And the thickness t1 of the thin plate portion 11
Is desirably set to 0.1 mm ≦ t1 ≦ 5 mm.

When the molded article 5 is molded by the molding die 12, the first and second steps are sequentially performed. First, in the first step, FIG.
As shown in the figure, a first cavity 20 corresponding to the first semi-molded product 6 is formed between the fixed mold 13 and the movable mold 14. That is, the advance / retreat position of the movable mold 14 is adjusted so that the interval between the fixed mold 13 and the movable mold 14 corresponds to the thickness t1 of the thin plate portion 11 in the first semi-molded product 6, and the gate 17 is opened to melt. A resin is injected into the first cavity 20.

In this first step, the thin plate portion 11
Then, the first semi-molded product 6 integrally having the boss portion 9 protruding from the back surface of the thin plate portion 11 is injection-molded.

After the execution of the first step, for example, 1
After cooling for ~ 180 seconds, the second step is performed. In the second step, first, as shown in FIG. By moving the movable mold 14 away from the fixed mold 13 by a predetermined distance, the second cavity 2 corresponding to the second semi-molded product 7 is formed.
1 is formed in a mold 12. That is, the thin plate portion 11 of the second semi-molded product 7 moved together with the movable die 14 and the fixed die 1
3 is adjusted so as to correspond to the thickness t2 of the second semi-molded product 7, and the gate 17 is opened and the molten resin is placed in the second cavity 21 as shown in FIG. Inject.

According to the second step, the second half-molded product 7 is injection-molded so as to be integrally joined to the surface side of the thin plate portion 11 of the first half-molded product 6. The thickness t2 of the semi-molded product 7 is 0.1 mm ≦ t2 ≦ 5
mm.

After the processing of the second step is completed, after cooling for, for example, 1 to 180 seconds,
The molded article 5 can be obtained by opening.

Next, the operation of this embodiment will be described. In molding the molded article 5 from a synthetic resin containing a glittering material, a thin plate portion 11 and a boss portion 9 projecting from the back surface of the thin plate portion 11 are formed. Semi-finished product 6 integrally having
Is injection-molded in a first step, and a plate-shaped second semi-molded product 7 constituting the plate portion 8 of the molded product 5 in cooperation with the thin plate portion 11 is integrally joined to the surface side of the thin plate portion 11. So that the second
Injection molding was performed in the step.

According to such an injection molding method, even if a flow mark or a weld line is formed on the surface of the thin plate portion 11 in the first semi-molded product 6, the surface of the thin plate portion 11 is formed by the second half molding. Since it is covered with the article 7, no flow mark or weld line remains on the surface of the second semi-molded article 7, that is, the surface of the molded article 5.

Since the tip of the pin 25 for forming the inner surface of the boss 9 protrudes from the rear surface forming surface 23 of the movable die 14, the first semi-molded product 6 is formed at the portion corresponding to the boss 9. Is prevented, and the portion corresponding to the boss portion 9 is prevented from becoming harder to cool as compared with other portions, so that the surface of the first semi-molded product 6 is prevented from sinking as much as possible. Thus, the influence of the sink on the surface of the second semi-molded product 7 covering the surface of the first semi-molded product 6 can be avoided.

At this time, the protruding amount L of the tip of the pin 25 from the back surface forming surface 23 is set to be ２〜 of the thickness t 1 of the thin plate portion 11.
By setting the ratio to 2/3, it is possible to prevent the first semi-molded product 6 from being excessively thin at a portion corresponding to the boss portion 9 and to prevent the surface of the first semi-molded product 6 from sinking. It can be more effectively prevented.

In this way, it is possible to prevent flow marks and weld lines from being formed on the surface of the molded product 5 and to prevent sink marks from being generated on the surface of the molded product 5, thereby improving the appearance of the molded product 5. Can be.

Further, since no gas pressure is applied to the inside of the mold 12 or any means or nest is provided for pressing the molten resin into the mold 12, the shape of the molded article 5 and the design of the mold 12 are not considered. There is no great restriction, and an increase in cost can be suppressed.

Further, in the first step, the first semi-molded product 6 is molded by injecting a synthetic resin into the first cavity 20 formed between the fixed mold 13 and the movable mold 14, and in the second step, Synthetic resin is injected into a second cavity 21 formed by moving the movable mold 14 away from the fixed mold 13 by a predetermined distance while the first semi-molded product 6 is housed in the molding die 12, thereby forming the second semi-molded product 7. In addition, since integral joining with the first semi-molded product 6 is performed, a plurality of molding dies are not required, so that the installation space for the molding dies 12 can be reduced, and the equipment cost can be reduced. it can.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the appended claims. It is possible.

[0032]

As described above, according to the first aspect of the present invention, the appearance of the molded article is prevented by preventing the occurrence of flow marks and weld lines on the surface of the molded article and by minimizing the occurrence of sink marks. It is possible to improve the shape and shape of the molded product and the design of the molding die without adding great restrictions, and it is possible to suppress an increase in cost.

According to the second aspect of the present invention, the surface of the first semi-molded product has sink marks while the thickness of the first semi-molded product at the portion corresponding to the boss portion is prevented from becoming too thin. This can be prevented more effectively.

[Brief description of the drawings]

FIG. 1 is a perspective view of a molded product.

FIG. 2 is a cross-sectional view of the molded product viewed from a direction along line 2-2 in FIG.

FIG. 3 is a vertical cross-sectional view of a molding die when a first step is performed.

FIG. 4 is a longitudinal sectional view of a molding die corresponding to FIG. 3 in a state before execution of a second step.

FIG. 5 is a longitudinal sectional view of the molding die corresponding to FIG. 3 at the time of executing the second step.

[Explanation of symbols]

 5 Molded product 6 First semi-molded product 7 Second semi-molded product 8 Plate part 9 Boss part 11 Thin plate part 13 First mold The fixed mold 14 as the movable mold as the second mold 20 the first cavity 21 the second cavity 22 the surface forming surface 23 the back surface forming surface 24 the concave portion 25 ··pin

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 4F202 AB14 AD03 AD04 AG02 AG03 AG28 CA11 CB01 CB26 CK52 CL01 4F206 AB14 AD03 AD04 AG02 AG03 AG28 JA07 JB24 JL02 JM04 JN12 JN33 JQ81

Claims (2)

[Claims] 1. A molded product (5) integrally comprising a plate portion (8) having a smooth surface and a cylindrical boss (9) projecting from the back surface of the plate portion (8). A first mold (13) having a surface forming surface (22) corresponding to the surface of the portion (8);
A back surface forming surface (23) corresponding to the back surface of the plate portion (8);
The back surface forming surface (2) corresponds to the outer surface of the boss portion (9).
A second mold (14) including a recess (24) provided in 3) and a pin (25) whose base end is connected to the closed end of the recess (24) corresponding to the inner surface of the boss (9). A second mold (14) in which the tip of the pin (25) is made to project beyond the back surface forming surface (23) in the injection molding method of injecting and molding a synthetic resin containing a glitter material.
The first cavity (2) formed between the first mold (13) and
By injecting the synthetic resin into 0), a thin plate portion (11) thinner than the plate portion (8) and the boss portion (9) protruding from the back surface of the thin plate portion (11) are integrally formed. A first step of forming the first semi-molded product (6), and the first and second molds (13, 14) are separated from each other by separating the surfaces of the thin plate portion (11) and the first mold (13). A) forming the plate portion (8) together with the thin plate portion (11) by injecting the synthetic resin into a second cavity (21) formed between the surface portion and the surface forming surface (22); Second
A second step of forming a semi-molded product (7) and joining it integrally to the surface side of said thin plate portion (11). 2. The amount of protrusion of the tip of the pin (25) from the back surface forming surface (23) is set to 1/2 to 2/3 of the thickness of the thin plate portion (11). Claim 1
The injection molding method according to the above.