JPH0885142A - Injection molding method and injection mold - Google Patents

Abstract

PURPOSE: To obtain a molded product beautiful in the appearance of a gate part. CONSTITUTION: In an injection molding method injecting a molten thermoplastic resin into a cavity through a runner part, the molten thermoplastic resin is injected into the cavity 3 and, thereafter, the heated and molten thermoplastic resin in the runner part 41 is introduced into the cavity 3 by the movement of a slider pin 5 and the runner part 41 is cut off from the cavity 3 to hold the thermoplastic resin in the cavity under pressure.

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 and an injection molding die, and more specifically, it does not require finishing of a gate portion of a molded product after molding and there is a risk that a sink mark or the like may be generated on the surface of the molded product. There is no such thing.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-1-118423.
As described in Japanese Patent Publication, a cylinder for temporarily accumulating the thermoplastic resin to be injected into the cavity is provided, and after the thermoplastic resin is injected into the cavity, the pin is operated to remove the thermoplastic resin in the cylinder. An injection molding method of press-fitting is known.

Further, for example, as described in JP-A-5-261778, after injecting a thermoplastic resin into a cavity, a minute vibration is applied to a pin to soften the thermoplastic resin near the gate portion. There is known an injection molding method in which a thermoplastic resin in the vicinity of a gate portion is pressed into a cavity by a pin.

[0004]

However, in the conventional injection molding method as described above, after the thermoplastic resin is injected into the cavity, the thermoplastic resin that is press-fitted into the cavity by the pin is placed in the mold. Since the outer layer portion in contact is solidified because the mold is water-cooled, the thermoplastic resin having the outer layer portion thus solidified is press-fitted into the cavity, and as a result, the gate portion of the molded product is so-called. It is wrinkled and the appearance is not good. Further, in order to press-fit the thermoplastic resin in which the outer layer portion is solidified into the cavity, a large pressure input is required.

The present invention has been made in view of the above problems in the conventional injection molding method. The object of the present invention is to solve the above problems and to provide a molded product having a beautiful appearance of the gate portion. An object of the present invention is to provide an injection molding method and an injection mold that can be obtained.

[0006]

In order to achieve the above object, the injection molding method of the present invention according to claim 1 is an injection molding in which a molten thermoplastic resin is injected into a cavity through a runner portion. In the method, after the molten thermoplastic resin is injected into the cavity, the slider pin is moved to press the heated thermoplastic resin in the runner portion into the cavity, and the runner portion and the cavity are blocked. It is characterized in that the thermoplastic resin therein is held under pressure.

Further, in the injection molding die of the present invention according to claim 2, a cavity is provided between the fixed die and the movable die, a runner portion communicating with the cavity is provided, and the runner portion is provided with a thermoplastic resin in the runner portion. Characterized in that a slider pin for press-fitting the resin into the cavity and blocking the inside of the runner portion from the inside of the cavity to hold the thermoplastic resin in the cavity under pressure is provided, and the runner portion is provided with a heating device. Is.

In the present invention as set forth in claim 2, the heating device provided in the runner portion is not particularly limited, but for example, an electric heater by electric heat, an oil heater by heating oil, etc. are compact. The temperature can be easily controlled, so that it can be preferably used.

[0009]

In the injection molding method of the present invention according to claim 1, after the molten thermoplastic resin is injected into the cavity, the slider pin is moved to move the thermoplastic resin in the runner portion in the molten state into the cavity. Since it press-fits and blocks the inside of the runner and the cavity to hold the thermoplastic resin in the cavity under pressure, the gate of the molded product has a beautiful appearance due to the pressing of the slider pin, and the gate There is no need for a cutting process, and there is no risk of sink marks on the surface of the molded product. or,
Since the thermoplastic resin in a heated and molten state in the cavity is press-fitted into the cavity, the press-fitting does not require a large pressure input.

Further, in the injection molding die of the present invention according to claim 2, a cavity is provided between the fixed die and the movable die, a runner portion communicating with the cavity is provided, and the runner portion is provided with heat in the runner portion. A slider pin that press-fits the plastic resin into the cavity and blocks the inside of the runner part from the inside of the cavity and pressurizes and holds the thermoplastic resin inside the cavity is provided, and the heating device is provided in the runner part. The thermoplastic resin is heated and melted by the heating device, and the thermoplastic resin that has been heated and melted is pressed into the cavity from the runner portion without requiring a large pressure by the movement of the slider pin. As a result, the gate portion of the molded product is formed. Has a beautiful appearance due to the pressing of the slider pin, and there is no risk of sink marks on the surface of the molded product.

[0011]

Embodiments of the present invention will now be described with reference to the drawings. [Embodiment of the Invention According to Claim 2] FIGS. 1 and 2 are explanatory views showing an example of the injection molding die of the present invention. FIG. 1 shows a state before the operation of the slide pin, and FIG. The state after operation is shown. 1 and 2, 1 is a fixed type,
Reference numeral 2 denotes a movable mold, and a cavity 3 having a shape corresponding to the shape of a molded product to be molded is provided between the fixed mold 1 and the movable mold 2.

Reference numeral 4 denotes a runner portion. The runner portion 4 has a first runner portion 41 communicating with the cavity 3 and a second runner portion 42 provided at a right angle to the first runner portion 41 and communicating with the first runner portion 41. It consists of The first runner part 41 is provided on the movable die 2, and the second runner part 4 is provided.
2 is provided so as to straddle the movable die 2 and the fixed die 1. The second runner portion 42 in the movable die 2 is provided with an undercut-shaped concave portion 421. When the movable die 2 is moved and divided from the fixed die 1, the thermoplastic resin in the second runner portion 42 is formed. Moves with the movable die 2 and moves away from the fixed die 1.

Reference numeral 5 is a slide pin.
The rear end of the slide pin 5 is housed in the hydraulic cylinder 51, and the tip of the slide pin 5 is moved to the first position by the operation of the hydraulic cylinder 51.
The runner portion 41 is slidably provided. When the tip portion of the slide pin 5 is most retracted as shown in FIG. 1, the first runner portion 41 and the second runner portion 42 communicate with each other, and the tip portion of the slide pin 5 is most advanced as shown in FIG. In this case, the slide pin 5 cuts off the cavity 3 from the first runner portion 41 and cuts off the first runner portion 41 from the second runner portion 42.

Reference numeral 411 denotes a heating device formed of an electric heater provided around the first runner portion 41, and the heating device 411 heats and melts the thermoplastic resin in the first runner portion 41. An inorganic heat insulating material 412 such as asbestos is provided around the heating device 411.
The heat generated by 11 is prevented from being transmitted to the periphery of the movable mold 2.

Reference numeral 6 is a nozzle provided at the tip of an injection molding machine (not shown), and the tip of the nozzle 6 is the second runner portion 4
The thermoplastic resin sent from the injection molding machine to the second runner 42 is sent to the second runner portion 42 via the nozzle 6. Reference numeral 21 denotes a molded product ejecting pin and a runner ejecting pin, and the rear ends of the ejecting pins 21 and 22 are attached to the extruding plate 23.

[Embodiment of the Invention According to Claim 1] A mode for carrying out the injection molding method of the present invention using the injection molding die of the present invention as described above will be described below. As shown in FIG. 1, the fixed die 1 and the movable die 2 are closed, and the slide pin 5
In a state in which the tip end portion of the is retracted most, the thermoplastic resin melted from the injection molding machine (not shown) is injected into the cavity 3 from the second runner portion 42 and the first runner portion 41 via the nozzle 6. .

Next, the slide pin 5 moves forward by the operation of the hydraulic cylinder 51, and the thermoplastic resin heated and melted by the heating device 411 in the first runner portion 41 is pressed into the cavity 3 by the tip of the slide pin 5. It As shown in FIG. 2, when the slide pin 5 is most advanced, the press-fitting of the thermoplastic resin in the first runner portion 41 into the cavity 3 is completed. In this way, the state in which the slide pin 5 is most advanced is maintained for a while, and the thermoplastic resin in the cavity 3 is held under pressure.

When the thermoplastic resin in the cavity 3 is cooled and solidified, the movable die 2 is moved and divided from the fixed die 1, and the thermoplastic resin in the cavity 3 moves together with the movable die 2 and leaves the fixed die 1. At this time, the thermoplastic resin in the second runner portion 42 is locked by the undercut portion 421 and moves together with the movable die 2.

When the movable die 2 is farthest from the fixed die 1, the ejection pins 21 and 22 are actuated so that the molded product in the cavity 3 is released from the movable die 2 and the second runner portion 4 is formed.
The thermoplastic resin in 2 is projected from the inside of the second runner portion 42. Thereafter, as shown in FIG. 1, the movable die 2 is closed again with the fixed die 1, and the same cycle is repeated.

Although the embodiments of the present invention have been described above with reference to the drawings, the configuration of the present invention is not limited to the illustrated embodiments, and design changes within the scope of the present invention are included in the present invention. Be done. For example, as in the illustrated embodiment, instead of providing a heat insulating material around the heating device, a cavity may be provided so that the heat of the heating device is not transmitted to the surroundings. In addition, if the heat of the heating device does not adversely affect the surroundings,
It is not necessary to perform such heat insulation treatment.

Further, the operation of the slide pin may be performed by an air cylinder instead of the hydraulic cylinder as in the illustrated embodiment, or by other means.

[0022]

In the injection molding method of the present invention as set forth in claim 1, after the molten thermoplastic resin is injected into the cavity, the slider pin is moved to move the thermoplastic resin in the heated molten state into the cavity. Since it press-fits into the inside of the cavity and shuts off the inside of the runner from the inside of the cavity, the thermoplastic resin inside the cavity is held under pressure.
The molded gate portion of the molded product has a beautiful appearance due to the pressing of the slider pin, and the gate cutting step is unnecessary, so that the surface of the molded product is free from sink marks.
Further, since the thermoplastic resin in a heated and molten state in the cavity is press-fitted into the cavity, the press-fitting does not require a large pressure input.

Further, in the injection molding die of the present invention according to claim 2, a cavity is provided between the fixed die and the movable die, a runner portion communicating with the cavity is provided, and the runner portion is provided with heat in the runner portion. A slider pin that press-fits the plastic resin into the cavity and blocks the inside of the runner part from the inside of the cavity and pressurizes and holds the thermoplastic resin inside the cavity is provided, and the heating device is provided in the runner part. The thermoplastic resin is heated and melted by the heating device, and the heated and melted thermoplastic resin is pressed into the cavity from the runner part by the movement of the slider pin.As a result, the gate part of the molded product appears by pressing the slider pin. It is beautiful and there is no risk of sink marks on the surface of the molded product.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an injection molding die of the present invention.

FIG. 2 is an explanatory view showing a state where a slide pin of the injection molding die of the present invention shown in FIG. 1 is operated.

[Explanation of symbols]

 1 Fixed type 2 Mobile type 21, 22 Ejection pin 23 Extrusion plate 3 Cavity 4 Runner part 41 First runner part 42 Second runner part 5 Slide pin 51 Hydraulic cylinder 6 Nozzle

Claims (2)

[Claims] 1. In an injection molding method of injecting a molten thermoplastic resin into a cavity via a runner portion, after injecting the molten thermoplastic resin into the cavity, the slider pin moves to move the inside of the runner portion. An injection molding method, characterized in that a thermoplastic resin in a heated and molten state is press-fitted into a cavity, the runner portion and the cavity are blocked, and the thermoplastic resin in the cavity is pressure-held. 2. A cavity is provided between the fixed die and the movable die, and a runner portion communicating with the cavity is provided,
The runner section is equipped with slider pins that press-fit the thermoplastic resin in the runner section into the cavity, block the inside of the runner section from the inside of the cavity, and hold the thermoplastic resin in the cavity under pressure, and the runner section is equipped with a heating device. The injection mold is characterized by: