JP3510353B2 - Molding method for synthetic resin molded products - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a synthetic resin molded product, and more particularly to a method for molding a decorative integrated molded product having a good appearance. 2. Description of the Related Art Conventionally, in injection molding, so-called decorative integral molding, in which a separately molded insert, film, or the like is integrally molded with a molded product, in order to impart a different appearance to the molded product. ing. FIG. 19 and FIG. 20 to FIG.
Shown in Reference numeral 41 in the drawing denotes a movable-side mounting plate, reference numeral 42 denotes a fixed-side mounting plate, and reference numeral 50 denotes an injection molding die, which includes a movable die 51 and a fixed die 52. Note that S is a sprue. As shown in FIGS. 19 and 20, a positioning pin 53 is provided on the cavity surface of the movable mold 51, and a film or an insert 54 is arranged at a predetermined position on the cavity surface of the fixed mold 52 by closing the mold. When a film is used instead of the insert, the film is fixed by suction to the cavity surface by an appropriate suction mechanism, or is fixed by sandwiching the edge of the film between a movable mold and a fixed mold. Sometimes.
A resin inlet 55 is formed on the cavity surface of the mold (movable mold 51 in this example) facing the cavity surface of the mold on which the insert 54 is disposed. This resin inlet 5
Numeral 5 is connected to an injection device (not shown) outside the mold, and injects a molten resin into the back surface of the insert 54 in the cavity to form a resin molded product integrated with the insert 54. [0003] By the way, the insert is generally formed prior to the formation of a decorative integral molded product.
The resulting insert may be distorted or warped due to variations in the molding conditions. Therefore, as shown in FIG. 20, the cavity surface 5 of the injection mold 50 is formed.
When the insert 54 is disposed on the insert 2a, a gap may be formed between the cavity surface 52a and the surface of the insert 54. Further, depending on the thickness of the insert 54, the thickness a of the cavity space on the back surface of the insert 54 may be extremely smaller than the thickness b of the cavity space in a portion where no insert is arranged. In such a case, as shown in FIG. 22, the molten resin P flowing from the resin inflow port 55 preferentially flows into the space b having a low flow resistance. Therefore, as shown in FIG. 21, if the insert 54 has the above-mentioned warpage or the like and a gap is formed between the insert 54 and the cavity surface, the resin injected at a portion near the resin inlet 55 is The insert is pressed by the pressure to correct the deformation or deflection, but as shown in FIG. 23, the resin wraps around the gap without correcting the deformation or deflection at a portion far from the resin inlet 55. However, there has been a problem that the appearance of the molded product is deteriorated. When the film 56 is disposed on the cavity surface instead of the insert as shown in FIGS. 24 to 26, the film may be stretched and sagged by the temperature of the mold or the resin pressure. Further, due to the difference in wall thickness of the molded product or the provision of a plurality of gates 57 as shown in the drawing, uneven flow occurs in the molten resin P. Sometimes. SUMMARY OF THE INVENTION The present invention has been proposed to solve such a problem, and it is an object of the present invention to obtain a molded article having a good appearance by a decorative integral molding method. It is an object of the present invention to provide a method for molding a synthetic resin molded article that can be used. [0008] That is, the present invention provides:
An insert or film is arranged on the cavity surface of the injection molding die, and a molten resin is formed on the back surface of the insert or film through a resin inlet formed on a cavity surface opposite to the cavity surface where the insert or film is arranged. In the method of molding a synthetic resin molded article integrated with the insert or the film by injecting, the cavity surface on the molten resin injection side, from the resin inflow port to the approximate center of the back side of the insert or the film Forming a groove-shaped resin guide path extending therethrough, guiding the molten resin to the groove-shaped resin guide path at the time of injecting the molten resin, and flowing from the groove-shaped resin guide path into a cavity substantially in the center of the back surface of the insert or film. By causing the molten resin to reach from the approximate center of the back surface of the insert or film to the back surface end portion And filled into the cavity, then according to the method of molding a synthetic resin molded article, characterized in that press-fitting the gas into the groove-like resin guide path from the resin inlet. The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an injection mold for carrying out the molding method of the present invention, FIG. 2 is a perspective view showing the movable mold,
FIGS. 3 to 10 show an example of the molding method of the present invention with reference to the main part of the mold. FIG. 3 is a sectional view showing a state in which a molten resin is injected into the mold, and FIG. FIG. 5 is a cross-sectional view showing a state in which the resin is guided to the groove-shaped resin guide path, FIG. 5 is a cross-sectional view showing a state in which the molten resin is filled in the cavity, and FIG. 7 is a plan view of the main part of the movable mold in FIG. 3, FIG. 8 is a plan view of the main part of the movable mold in FIG. 4, FIG. 9 is a plan view of the main part of the movable mold in FIG. FIG. 7 is a plan view of a main part of a movable mold in FIG. 6. FIGS. 11 to 18 show another example of the present invention with reference to the drawings of the main part of the mold.
1 is a cross-sectional view showing a state in which the molten resin is injected into the mold, FIG. 12 is a cross-sectional view showing a state in which the molten resin is guided to a groove-shaped resin guiding path, and FIG. 13 is a state in which the molten resin is filled in a cavity. FIG. 14 is a cross-sectional view showing a state in which gas is press-fitted into the groove-shaped resin guide path, FIG. 15 is a plan view of a main part of the movable mold shown in FIG. 11, and FIG. FIG. 17 is a plan view of the main part of the movable mold of FIG. 13, and FIG. 18 is a plan view of the main part of the movable mold of FIG. According to the molding method of the present invention, an insert or a film (hereinafter referred to as an insert) is arranged on a cavity surface of an injection mold, and a molten resin is injected into a back surface of the insert or the like to be integrated with the insert or the like. This is a suitable method for obtaining a synthetic resin molded product with a beautiful appearance. As shown in FIGS. 1 and 2 and the like, in an injection mold used in the molding method of the present invention, a mold (movable mold in this embodiment) opposed to a cavity surface in which an insert or the like is arranged. A resin inlet 15 is provided on the cavity surface of 11). Reference numeral 12 denotes a fixed die that forms a molded product cavity together with the movable die 11, and reference numeral 13 denotes a positioning pin of the insert. And
The insert 14 is arranged on the cavity surface of the fixed mold 12 by the positioning pin 13. Note that reference numerals 41,
Reference numerals 42 and S denote a movable-side mounting plate, a fixed-side mounting plate, and a sprue, respectively, as described in the description of the related art. The resin inlet 15 is connected to an injection device (not shown) outside the mold. As shown in FIGS. 3 and 7, a predetermined amount of molten resin P is supplied through the resin inlet 15 to the cavity. It is injected inside. The resin inlet 15 is also switchably connected to a high-pressure gas generator (not shown) outside the mold. This high pressure gas generator,
After the filling of the molten resin P is completed, a high-pressure gas is injected into the mold, and a known gas injection device is used. A groove-shaped resin guiding path 16 continuous from the resin inlet 15 is provided on the mold on the side where the molten resin is injected, that is, on the cavity surface of the movable mold 11. As shown in FIGS. 4 and 8, when the molten resin P is injected, the molten resin P discharged from the resin inflow port 15 is first placed on the back side of the insert 14 as shown in FIGS. By guiding the flow of the molten resin P in the cavity from the center to the end of the insert 14 by guiding the flow to the substantially central portion, the molten resin P is disposed at least from the resin inlet 15 in the cavity. It is preferable to connect the positions of the inserts and the like reaching the approximate center of the back surface. Thereby, as shown in FIGS. 5 and 9, the back surface of the insert 14 moves from the center to the end by the resin pressure of the molten resin P when the molten resin P reaches the end from the center of the back surface of the insert. As a result, the slack or distortion of the insert is corrected, so that the molten resin P does not enter the gap between the surface of the insert 14 and the cavity surface of the fixed mold 12, and a molded article with a beautiful appearance can be obtained. As can be understood from FIG. 2, in order to smoothly guide the molten resin P from the substantially central portion of the insert 14 toward the end, the grooved resin guide path 16 is provided at the end of the insert 14. A branch guide path 16a may be further provided. In this embodiment, branch guide paths 16a, 16a separated on both sides are provided at the end of the groove-shaped resin guide path 16, and are formed in a substantially T-shape as shown in the figure. By the way, as shown in the figure, the molded product becomes thick at the portion where the concave groove-shaped resin guide path 16 is provided in the cavity, and there is a possibility that sink and deformation may occur in the portion of the molded product. is there. As shown in FIGS. 6 and 10, after the molten resin P is filled in the cavity, a high-pressure gas G is injected from the resin inlet 15 to prevent the sink and deformation. As described above, since the thickness of the cavity space is large in the groove-shaped resin guiding path 16 portion, the molten state of the molten resin P lasts longer than other portions. Therefore, the injected high-pressure gas G selectively flows in the groove-shaped resin guide path 16 and forms a hollow portion 19 in the groove-shaped resin guide path 16. As a result, the thickness of the molded product in the grooved resin guide path 16 is reduced, and the occurrence of sink marks, deformation, and the like is prevented. As the high-pressure gas, an inert gas such as nitrogen is preferably used. FIGS. 11 to 18 show another example of the present invention. In this example, a film 24 is used instead of the insert. As shown in FIGS. 11 and 15, the film 24 has one end formed in a shape cut in the middle of the cavity, and the other end formed by the movable mold 21 and the fixed mold 22 of the injection mold 20. It is pinched. The stationary mold 22 includes a vacuum suction mechanism 2.
3 is provided, and the film 24 is suction-held on the cavity surface of the fixed mold 22. The movable mold 21 is provided with a resin inlet 25 and a groove-shaped resin guide path 26 is formed continuously with the resin inlet 25. The groove-shaped resin guide path 26 is provided from one end of the film 24 (the resin inflow port 25) toward the center of the film 24, and further branches to both ends (up and down in the figure) of the film 24. As shown in FIGS. 12 and 16, the molten resin P flowing from the resin inlet 25 reaches the approximate center of the back surface of the film 24 via the grooved resin guide path 26. Then, as shown in FIGS. 13 and 17,
The molten resin P is sequentially filled toward the edge of the film while extruding the slack of the film 24 by the resin pressure. When one end of the film 24 is cut in the middle of the cavity as in this embodiment, the fixed die 22 and the movable die 21 are located at a position opposite to the end of the film cut in the middle of the cavity. Even if the leading end and the branch portion of the grooved resin guide path 26 are positioned near the end of the film to be sandwiched, the slack of the film 24 can be effectively removed. Next, in order to prevent the molded product from sinking due to the groove-shaped resin guide path 26, the resin inlet 2
From 5, the high-pressure gas G is press-fitted into the groove-shaped resin guide path 26. As shown in FIGS. 14 and 18, the high-pressure gas G forms a hollow portion 29 in the grooved resin guide path 26, and reduces the thickness of the molded product in that portion. As shown and described above, according to the molding method of the present invention, the molten resin injected from the resin inlet through the concave-shaped resin guiding path is substantially centered on the back side of the insert or the like. Since the resin is gradually filled from the portion to the end, the resin back pressure effectively pushes the back surface of the insert and makes it closely adhere to the cavity surface. Thereby, the gap between the insert surface and the cavity surface is eliminated, and the molten resin does not flow into the gap to make the appearance of the molded product poor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing an example of an injection mold for carrying out a molding method of the present invention. FIG. 2 is a perspective view showing a movable mold of the injection molding die. FIG. 3 is a sectional view of a main part of a mold showing a state in which a molten resin is injected into a mold. FIG. 4 is a cross-sectional view of a main part of a mold showing a state in which a molten resin is guided to a groove-shaped resin guide path. FIG. 5 is a cross-sectional view of a main part of a mold showing a state in which a molten resin is filled in a cavity. FIG. 6 is a sectional view of a main part of a mold showing a state in which gas is press-fitted into the grooved resin guide path. FIG. 7 is a plan view of a main part of the movable mold in FIG. 3; FIG. 8 is a plan view of a main part of a movable mold in FIG. 4; FIG. 9 is a plan view of a main part of the movable mold in FIG. 5; FIG. 10 is a plan view of a main part of the movable mold in FIG. 6; FIG. 11 shows another example of the present invention and is a cross-sectional view of a main part of a mold showing a state in which a molten resin is injected into the mold. FIG. 12 is a cross-sectional view of a main part of a mold showing a state in which a molten resin is guided to a groove-shaped resin guide path. FIG. 13 is a cross-sectional view of a main part of a mold showing a state where a molten resin is filled in a cavity. FIG. 14 is a sectional view of a main part of a mold showing a state in which gas is press-fitted into the groove-shaped resin guide path. FIG. 15 is a plan view of a main part of the movable mold of FIG. 11; FIG. 16 is a plan view of the main part of the movable mold of FIG. 12; FIG. 17 is a plan view of a main part of the movable mold of FIG. 13; 18 is a plan view of a main part of the movable mold of FIG. FIG. 19 is a cross-sectional view of a mold showing a method of forming a general decorative integrated molded product. FIG. 20 is a cross-sectional view of a main part of a mold showing an initial stage of injecting molten resin into the cavity. FIG. 21 is a cross-sectional view of a main part of a mold showing a state in which a molten resin is injected into the cavity. FIG. 22 is a cross-sectional view of a main part of a mold showing a state in which a molten resin flows into the cavity. FIG. 23 is a cross-sectional view of a main part of a mold showing a state in which the cavity is filled with a molten resin. FIG. 24 is a sectional view of a main part of a mold showing another conventional example. FIG. 25 is a sectional view showing a state in which a molten resin is injected into a cavity of the mold. FIG. 26 is a cross-sectional view showing a state in which the cavity is filled with a molten resin. [Description of Signs] 10 Injection molding die 11 Movable die 12 Fixed die 13 Positioning pin 14 Insert 15 Resin inlet 16 Groove-shaped resin guide path P Melted resin

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (1)

(57) [Claim 1] An insert or a film is arranged on a cavity surface of an injection mold, and a resin flow formed on a cavity surface opposite to the cavity surface on which the insert or the film is arranged. A method for molding a synthetic resin molded article integrated with the insert or the film by injecting the molten resin into the back surface of the insert or the film through an inlet, wherein the cavity surface on the molten resin injection side includes: Forming a groove-shaped resin guiding path extending from the resin inlet to the approximate center of the back side of the insert or the film; guiding the molten resin to the groove-shaped resin guiding path when injecting the molten resin; The molten resin is inserted into the cavity of the insert or the film by flowing the molten resin into the cavity at a substantially central portion of the back surface of the insert or the film from the path. Filled from the back substantially central portion in the cavity so reaches the rear surface end, then, the molding process of synthetic resin molded article, characterized in that press-fitting the gas into the groove-like resin guide path from the resin inlet.