JP3220272B2 - Injection molding method to paint simultaneously with molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to an injection molding how to perform coating on the surface of the molding simultaneously with the molded product.

[0002]

2. Description of the Related Art Conventionally, in the surface coating of an injection-molded molded product, after the injection-molded molded product is taken out of an injection molding machine, the surface of the molded product is painted by a post-processing coating process.

[0003]

In the above prior art,
The painting process usually requires human labor to perform undercoating, intermediate coating, topcoating, etc., and surface defects such as poor gloss appearance, scratches and pinholes generated during molding can not be repaired by painting in post-processing. Since it is difficult, it was necessary to take measures to prevent the surface defects from occurring during molding.

The present invention has been made in view of the above-mentioned problems of the prior art, and can save labor without requiring a coating step after molding, and can repair surface defects of molded articles. it is an object to realize an injection molding how to perform simultaneously painted molding.

[0005]

In order to achieve the above-mentioned object, an injection molding method according to the present invention for performing coating simultaneously with molding is provided.
A coating nozzle having a cavity for molding a molded product having a thick part in a part thereof and having an opening on a cavity surface for forming a back surface side of the thick part of the cavity surface of the cavity is provided. An injection molding method in which the mold is clamped, the molten resin is injected and filled into the cavity, and a pressure-holding step is performed after the mold is closed, and the molded article after the pressure-holding step is cooled and solidified. During the process, a skin layer is formed on the thick part of the molded product, but the inside is melted. Injecting, breaking the skin layer on the back surface of the thick portion to penetrate into the molded product, and then breaking the skin layer on the surface of the thick portion to form the surface of the molded product and the cavity surface opposed thereto In the middle to form a coating film Chi, is characterized in that the coating film is dried under compression state by clamping the mold again.

[0006]

[0007]

[Function] During the cooling step after the pressure holding step after injection filling, a skin layer is formed on the thick part of the molded product, but the mold is opened only by a small amount at the stage where the inside is molten. After that, when the pressurized paint is injected, the skin layer on the back side of the thick part is broken by the pressure of the paint, and the paint penetrates and passes through the molten resin of the thick part still in a molten state,
The skin layer on the surface side of the thick part is broken, flows into and spreads between the surface of the molded product and the cavity surface facing the molded product, and a coating film is formed on the entire surface of the molded product. after that,
The mold is clamped again to compress the coating film and the molded product, and the paint is dried and the molded product is cooled and solidified. This allows
The surface of the molded article is brought into close contact with the paint.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of an injection mold used for carrying out the injection molding method of the present invention will be described.

FIG. 1 is a schematic sectional view of one embodiment of an injection mold.

As shown in FIG. 1, the injection molding die of this embodiment comprises a fixed die 1 and a movable die 2, and is used for molding a molded product 23 having a thick portion 23a at the time of mold clamping. This is a two-cavity one that forms the cavity 6a.

The fixed mold 1 has one sprue 6e into which the molten resin is introduced from the injection nozzle 12 of the injection unit 11,
It has one surface of the two runners 6 d and a cavity surface for forming the surface of the molded product 23.

On the other hand, the movable mold 2 has a cavity surface for forming the back surface of the molded product 23 corresponding to the two cavity surfaces of the fixed mold 1, and the thick portion 23 of the molded product 23 is formed.
The portion corresponding to a is formed at the end face of the opening 3a of the coating nozzle 3.

The opening 3a of the passage 3b of the coating nozzle 3 is
Piston 7 of cylinder 4 as drive means for opening and closing the valve
Can be opened and closed by a valve rod 5, which is a valve for opening and closing the opening 3a integrally mounted on the cylinder 4, and by switching the supply direction of the pressurized fluid to the cylinder 4, the valve rod 5 is moved backward or forward. Thus, the opening 3a can be opened and closed.

An ejector plate 10 is provided in the cavity of the movable mold 2 in the same manner as the known one, and a plurality of ejector pins 8 for projecting a molded product of each cavity 6a are provided on one surface thereof. , 9 are projected.

FIG. 2 is an explanatory diagram of a fluid circuit for operating the coating nozzle.

The passage 3b in the coating nozzle 3 is connected to the paint tank 17 by a paint supply pipe 17a with a paint switching valve 15 interposed therebetween. The outlet side of the paint injection pump 16 communicates between them. The paint injection pump 16 is connected to the discharge side of the pump 21 by a first conduit 24 with the first switching valve 13 interposed therebetween.
A flow control valve 19 is provided between the pump 3 and the pump 21. Here, when the paint injection pump 16 is a constant-rate pump, the amount of paint to be injected is constant, and the accuracy of the film thickness of the coating film is improved.

On the other hand, a valve stem 5, which is a valve for opening and closing the opening 3a of the coating nozzle 3, is connected to a piston 7 of a cylinder 4, and a pair of guide holes 4a, 4b of the cylinder 4 are connected to a second switching valve. 14 predetermined ports. The second switching valve 14 is connected to the outlet side of the pump 21 by a second conduit 25 with the flow control valve 18 interposed therebetween. In addition, the suction side of the pump 22 communicates with the tank 22 and the pressure adjustment valve 20 is provided on the outlet side of the pump 21 so that the pressure of the pressurized fluid discharged from the pump 21 can be adjusted to a predetermined pressure. It is configured as follows.

In the above embodiment, one coating nozzle is provided. However, if necessary, a plurality of coating nozzles are opened at a plurality of portions of the cavity surface, so that multicolor coating is performed. It is also possible to mold a molded article. Alternatively, the movable mold may be provided with a cavity surface on the molded product front side, and the fixed mold may be provided with a cavity surface on the molded product rear surface side and an opening of the coating nozzle.

Next, each step of the injection molding method of the present invention will be described with reference to FIGS.

FIG. 3 is an explanatory view showing each step of the first embodiment of the injection molding method of the present invention.

(A-1) The fixed mold 1 and the movable mold 2 are mounted on an injection molding machine (not shown) and clamped (step S1).
By injecting the molten resin from the injection nozzle 12 of the injection unit 11, the sprue 6e, the runner 6d and the gate 6
c into the cavity 6a through injection filling.
a is formed by molding the molded article 23 having a.
1 mold clamping 1). In this step, the solenoid b of the second switching valve 14 is excited to make the second conduit 25 communicate with one of the guide holes 4a of the cylinder 4, thereby supplying a pressurized fluid, and FIG.
As shown in (1), the valve stem 5 is moved forward together with the piston 7, and the opening 3a of the coating nozzle 3 is closed.

(A-2) Next, the molded article 23 is cooled and solidified (cooling in step S3-2).
In the stage where the skin layer is formed but the inside is still in the molten state, the movable mold 2 is moved in the mold opening direction by the thickness of the coating film A to be painted to open a small amount (step S3-
1 mold opening 2).

(A-3) Thereafter, the solenoid a of the second switching valve 14 is excited to make one of the guide holes 4b of the cylinder 4 communicate with the second pipe 25, and the valve rod 5 is retracted together with the piston 7. Then, the opening 3a is opened (the coating nozzle is opened in step S4). Then, the solenoid a of the paint switching valve 15 is excited to make the passage 3b communicate with the paint supply pipe 17a, and the solenoid a of the first switching valve 13 is excited so that the first pipe 24 and the discharge side of the pump 21 are excited. And the piston 16
a in the discharge direction, and pressurized the paint B through the passage 3b.
To be injected into the thick part 23a of the molded article 23 from the opening 3a (painting in step S5). At this time, since the skin layer is formed on the surface of the thick portion 23a as described above, the inside is still molten,
The paint B breaks the skin layer on the back side of the molded article 23 and penetrates into the thick portion, and further breaks the skin layer on the front side,
It flows into and spreads between the surface of the molded product and the cavity surface facing the molded product, and the entire surface of the molded product is covered with the coating film A. When it is desired to form a coating film on a part of the surface rather than on the entire surface, a projection serving as a partition is formed on the cavity surface. By doing so, it is possible to prevent the paint from spreading and to perform partial coating.

(A-4) After the completion of the paint injection, the solenoid b of the second switching valve 14 is excited to make the other conduit 4a of the cylinder 4 communicate with the second pipe 25, and the valve rod together with the piston 7 is opened. Is moved forward to close the opening 3a (the coating nozzle is closed in step S6), and then the coating film A is dried in a state where the coating film A and the molded article 23 are compressed by applying a mold clamping force ( Mold clamping 2 in step S7, coating film drying in step S8),
The mold is opened to take out the molded product (mold opening 2 in step S9, removal in step S10).

In the second embodiment, instead of the step (A-2) of the first embodiment, a skin layer is formed on the thick portion 23a at the stage where the molded product 23 is cooled and solidified. However, at the stage where the inside is in a molten state, the magnitude of the mold clamping force is reduced by the pressure of the injected paint B to the size that the movable mold 2 moves in the mold opening direction by the thickness of the coating film A. . In this case, when the pressurized paint B is injected, the movable mold 2 moves in the mold opening direction by the thickness of the coating film A due to the pressure.

The other steps are the same as those in the first embodiment, and the description is omitted.

[0027]

Since the present invention is configured as described above, the following effects can be obtained.

[0028] The labor saving of the coating process after the injection molding can be realized. In addition, the surface defects that occur on the surface of the molded product during molding can be repaired by the coating film to form a molded product with good appearance, and paint is pressed from the back side of the thick part of the molded product and molded. Since the coating film is formed on the surface of the product, the surface of the coating film becomes smooth, so that it is particularly suitable for molding exterior parts.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of one embodiment of an injection mold.

FIG. 2 is an explanatory diagram of a hydraulic circuit for operating a coating nozzle.

FIG. 3 is an explanatory view showing each step of an injection molding method in which coating is performed simultaneously with molding using the injection molding die shown in FIG.

FIG. 4 is a sequence diagram showing steps of one embodiment of an injection molding method for performing coating simultaneously with molding.

[Explanation of symbols]

 Reference Signs List 1 fixed type 2 movable type 3 painting nozzle 3a opening 3b passage 4 cylinder 4a, 4b guide hole 5 valve stem 6a cavity 7 piston 11 injection unit 12 injection nozzle 13 first switching valve 14 second switching valve 15 paint switching valve 16 Paint injection pump 16a Piston 17 Paint tank 17a Paint supply pipe 18, 19 Flow control valve 20 Pressure control valve 21 Pump 22 Tank 23 Molded product 24 First pipe 25 Second pipe A Coating film B Paint

Continuation of the front page (72) Inventor Atsushi Teraoka 1-6-1, Funakoshiminami, Aki-ku, Hiroshima-shi, Hiroshima Japan Steel Works Co., Ltd. (56) References JP-A-63-268615 (JP, A) JP-A-62 -160216 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (2)

(57) [Claims] 1. A cavity for molding a molded article having a thick part in a part thereof, and an opening is formed in a cavity surface for forming a back surface side of the thick part in a cavity surface of the cavity. An injection molding method using a mold provided with a coating nozzle, clamping the mold, injecting and filling a molten resin into the cavity, and then performing a pressure-holding step, wherein the molding after the pressure-holding step is performed. During the process of cooling and solidifying the product, a skin layer is formed on the thick part of the molded product, but the interior is melted. The pressurized paint is injected to break the skin layer on the back surface of the thick portion and penetrate into the molded product, and then break the skin layer on the surface of the thick portion to face the surface of the molded product and face the molded product. Between the cavity surface After having formed the injection molding method of molding and simultaneously painting, characterized in that the coating film is dried under compression by clamping the mold again. 2. The method according to claim 1, wherein instead of opening the mold by a small amount, the mold clamping force is reduced, and the mold is opened by a small amount by the pressure of the paint when the pressurized paint is injected. An injection molding method for performing coating simultaneously with the molding according to claim 1.