JP3297517B2 - Molding method and molding die for synthetic resin products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of injecting and filling a molten resin into a cavity formed by a fixed mold and a movable mold through a manifold formed in the fixed mold, and cooling and solidifying the molten resin. The present invention relates to a method for molding a synthetic resin product in which a movable mold is opened with respect to a fixed mold to obtain a synthetic resin product, and a molding die used for performing the molding method.

[0002]

2. Description of the Related Art An injection molding method is known as a method for molding a synthetic resin product. The mold used in this injection molding method includes a fixed mold and a movable mold, and these molds are provided with cavities into which molten resin is injected and filled. Therefore, the movable mold is clamped to the fixed mold, and the cavity is injected and filled with a plasticized resin from an injection machine through, for example, a manifold or a gate,
When the movable mold is opened after cooling and solidification, a synthetic resin product having a desired shape molded by the cavity can be obtained. By the way, although a synthetic resin product is obtained as described above, a sprue, a runner, a gate resin formed with a gate, and the like are often attached to the synthetic resin product and must be separated from the product. The separated gate resin and the like can be reused, but must be crushed to an appropriate size so that they can be supplied to, for example, a hopper, and there is a problem with the physical properties of the resin. Further, there are problems of cost and work efficiency for separating the gate resin and the like. Therefore, there is also known a runnerless system, that is, a hot runner system capable of continuously forming a sprue, a runner, a gate resin and the like without taking out the sprue, the runner, the gate resin and the like every cycle.

[0003]

At the same time as the mold is opened, sprue, runner resin and the like can be separated from the synthetic resin product and collected separately. However, since the cavity is filled through a manifold, a gate and the like, Generally, a synthetic resin product has a gate resin formed by a manifold, a gate, or the like. Therefore, it is necessary to cut it off, and there are various problems as described above. It is considered that the cause of the poor cutting of the gate resin is that when the movable mold is opened, the tree finger pressure in the manifold acts on the gate and the gate is blown out, so that the gate cutting is deteriorated. Also, in any mold clamping machine, the mold opening speed at the start of mold opening is generally slower than at other times, so that the gate resin is cut off in a stretched state. Therefore, the gate resin
It is also considered that it is difficult to cut from the end face of the synthetic resin product. In particular, the toggle-type mold clamping machine, when the mold opens to some extent due to its characteristics,
The mold opening speed increases, but the speed at the start of mold opening is low, so the gate resin is cut off in a stretched state, and in a molding machine equipped with a toggle-type mold clamping machine, the gate resin is generally cut. It gets worse. Also, in the hot runner system, the tree fingers in the manifold are heated by the heater and are in a molten state, so that the gate cut is poor. If the gate cut is poor, the gate must be finished as described above, which also increases the cost of the synthetic test product. Accordingly, it is an object of the present invention to provide a method of molding a synthetic resin product having good gate cutting and a molding die used in the molding method.

[0004]

According to the first aspect of the present invention, in order to achieve the above object, a cavity formed by a fixed mold and a movable mold is formed in a fixed mold. Injecting and filling the molten resin through the manifold and the gate, and waiting for cooling and solidification, when opening the movable mold with respect to the fixed mold, reduce the pressure of the molten resin in the manifold. After the mold opening speed increases, the movable mold is separated from the fixed mold to obtain a synthetic resin product. The invention according to claim 2 comprises a movable mold and a fixed mold, and a molten resin is injected and filled into a cavity formed between these molds through a manifold and a gate. Wherein the fixed mold is axially movable with respect to a fixed plate to which the fixed mold is attached, and when the fixed mold is separated from the fixed plate, the manifold of the manifold is removed. The volume is increased and the pressure of the molten resin is configured to decrease, and between the fixed mold and the fixed plate, the movable mold is separated from the fixed mold at an initial stage of mold opening. A pressing means for pressing the fixed mold in the direction of the movable mold is provided so as not to separate, and the invention according to claim 3 is configured such that the pressing means is formed of a spring.

[0005]

The movable mold is clamped to the fixed mold by using, for example, a toggle mold clamping machine. Then, the pushing means for pushing the fixed mold in the direction of the movable mold is in a retracted state or a compressed state. Cavities are formed between these molds. Therefore, the molten resin is injected from the nozzle of the injection machine into the cavity through the gate through, for example, a manifold, and is filled. After cooling and solidifying, open the movable mold. Then, the pressing means provided between the fixed die and the fixed plate presses the fixed die toward the movable die. Since the fixed mold is pushed toward the movable mold, the movable mold does not separate from the fixed mold in the initial stage of mold opening. When the pressing means finishes pressing, the movable mold separates from the fixed mold. Then, the synthetic resin product is taken out. As described above, at the initial stage of mold opening, the pressing means pushes the fixed mold toward the movable mold, and the parting P is not separated.
Although the gate cannot be cut, the volume of the manifold increases, the tree finger pressure in the manifold decreases, and the gate does not act because the fixed mold is separated from the fixed plate. When the tree finger pressure decreases and does not act on the gate, the pressing means stops pushing the fixed mold toward the movable mold, and the movable mold is separated from the fixed mold. At this time, the separation speed is high, and the gate is reliably cut off.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a hot runner system and the pressing means is implemented by a coil spring will be described below. As shown in FIG. 1, the mold includes a fixed mold 2 on the fixed plate 1 side, and a movable plate 1 paired with the fixed mold 2.
The movable mold 12 on the 0 side, the separating member 20 attached to the fixed mold 2, and a plurality of springs 5, 5,... Urge the separating member 20 toward the movable mold 12. Have been. In the figure of the fixing plate 1, a relatively large opening is formed substantially at the center, and the boss 3 of the fixing die 2 is loosely fitted in this opening. Therefore, the fixed mold 2 is fixed to the fixed plate 1.
Can be moved in the axial direction with respect to. Also, a plurality of holes 4, 4, 4
Are opened, and one ends of the coil springs 5, 5,... Are mounted in these holes 4, 4,.

[0007] A separation member 20 is attached to the end surface of the fixed die 2 on the fixed plate 1 side. And this separation member 2
0, a plurality of holes are formed in pairs with the holes 4, 4,... Of the fixing plate 1, and coil springs 5, 5,.
Is mounted on the other end. A manifold 6 is formed in the axial direction of the fixed mold 2. The injection nozzle 30 is loosely mounted on the manifold 6.
The manifold 6 extends in the horizontal direction and continues to the nozzle hole 7, and the tip of the nozzle hole 7 is a gate 8. As is well known, the fixed die 2 is provided with a concave portion 9 which opens toward the movable die 12, and a gate 8 is opened in the concave portion 9. A torpedo 21 is attached to the separating member 20, and the torpedo 21 extends to near the tip of the nozzle hole 7. The reference numeral 22 in FIG.
Is shown .

The movable mold 12 has a conventionally known structure. That is, the movable mold 12 is provided with the core 13 paired with the recess 9 of the fixed mold 2. The core 13 cooperates with the recess 9 to form a synthetic resin product. The diameter of the core 13 is smaller than the diameter of the recess 9 by a predetermined amount, and the protrusion amount is smaller than the depth of the recess 9. Therefore, the movable mold 12
Is fixed to the fixed mold 2, cavities 14 are formed at predetermined intervals between the outer peripheral surface of the core 13 and the inner peripheral surface of the concave portion 9 of the fixed mold 2. The movable mold 10 has a recess 9
Ejector pins 15, 15 protruding and retracting around are provided to be able to move forward and backward. The figure does not show a mold clamping machine, for example, a toggle mold clamping machine. Also, a cooling mechanism for cooling the cavity 14 is not shown.

Next, a molding method for molding a synthetic resin product using the dies 2 and 12 will be described. The movable mold 12 is abutted against the fixed mold 2 and the mold is clamped by a conventionally known, for example, toggle-type mold clamper. Then, the state shown in FIG. 1 is obtained. That is, the core 13 of the movable mold 12 enters the recess 9 of the fixed mold 2 to form the cavity 14. Also, the coil springs 5, 5,. From the injection nozzle 30, the plasticized molten resin J is injected into the manifold 6. Then, the molten resin J reaches the nozzle hole 7 from the manifold 6 and fills the cavity 14 via the gate 8. FIG. 2 shows the state after the injection filling.

As shown in FIG. 2, when the filling is completed, the area around the cavity 14 is cooled. Cavity 1
The resin filled in 4 solidifies. The resin J such as the manifold 6 and the nozzle holes 7 does not solidify. The movable mold 12 is shown in FIG.
Open as shown. When released, the tightening force is lost, so that the compressed coil springs 5, 5,... Are released, and the separating member 20 is separated from the fixed plate 1 by the restoring force of the coil springs 5, 5,. That is, the fixed mold 2 is separated from the fixed plate 1 as shown in FIG.
After a predetermined distance, the movable mold 12 is moved to the fixed mold 2
Move away from The detached state is shown in FIG.

When the separating member 20 is separated from the fixed plate 1, the injection nozzle 30 is fixed to the fixed plate 1,
Since the fixed mold 2 moves to the left from the fixed plate 1 in the figure, the space or volume V of the manifold 6 increases. As a result, the tree finger pressure in the manifold 6 decreases,
The pressure on the gate 8 has also decreased. That is, the gate is easily cut. In particular, the mold opening speed of the toggle-type mold clamping machine is low in an early stage, but increases after a certain time. According to the present embodiment, since the movable mold 12 separates from the fixed mold 2 at the time when the movable mold 12 becomes large, the separation speed is also high. As described above, when the gate is easily cut, the movable mold 12 separates from the fixed mold 2 at a high speed, so that the gate is surely cut. FIG. 4 shows an almost completely cut state. Further, the movable mold 12 is opened, and the synthetic resin S is taken out with the ejector pins 15 and 15 as conventionally known. The movable mold 12 is again clamped to the fixed mold 2 and molded in the same manner.

According to this embodiment, various effects can be obtained. For example, since the pressing means is composed of the coil springs 5, 5,..., When the mold is opened, the fixed mold 2 separates from the fixed plate 1 before the parting P of the molds 2, 12 opens, and the mold opening There is an advantage that timing can be taken automatically. Also, since the coil springs 5, 5,... Are provided, the effect of damping the impact of the molds 2, 12 during mold clamping can be obtained.
In the above embodiment, the pressing means is the coil springs 5, 5,.
However, it is obvious that the present invention can be implemented by air pressure instead of the coil springs 5, 5,. It can also be implemented with hydraulic pressure. Since the hydraulic pressure has a small amount of compression, it is desirable to combine it with an air pressure accumulator or the like when implementing with hydraulic pressure. As described above, since the coil springs 5, 5,..., Air pressure, etc. are compressible and have a restoring force, the opening timing of the parting P of the molds 2, 12 can be automatically set. It can also be implemented by a member such as a cam. That is, a cam is provided between the fixed plate 1 and the separating member 20, and in the initial stage of the mold opening, the cam is driven so that the parting P does not open according to the mold opening speed, and the mold opening speed increases. Therefore, the fixed mold 2 can be separated from the fixed plate 1. However, this embodiment
As in the pneumatic embodiment, it is not shown in the figure.

[0013]

As described above, according to the present invention, the molten resin is injected into the cavity formed by the fixed mold and the movable mold via the manifold and the gate formed in the fixed mold. Filling, and waiting for cooling and solidification, when opening the movable mold with respect to the fixed mold, increase the volume of the manifold filled with resin, that is, reduce the pressure of the resin in the molten state, mold After the opening speed increases, the movable mold is separated from the fixed mold to obtain a synthetic resin product. Therefore, the gate is easily cut, and when the mold opening speed is high, the movable mold is separated from the fixed mold. So
An advantage unique to the present invention is that the gate can be reliably cut.

[Brief description of the drawings]

FIG. 1 is a front view showing a state in which a fixed mold and a movable mold are clamped in a partial cross section, showing an embodiment of the present invention relating to a mold.

FIG. 2 is a front view showing a state in which a cavity of a clamped mold is fully filled with a molten resin in a partial cross section.

FIG. 3 is a front view showing a partial cross section of a mold at an initial stage of mold opening.

FIG. 4 is a front view showing a state in which a mold is advanced and a movable mold is separated from a fixed mold in a partial cross section.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed plate 2 Fixed mold 5 Coil spring 6 Manifold 8 Gate 12 Movable mold 14 Cavity

Claims (3)

(57) [Claims] A fixed mold (2) is provided in a cavity (14) formed by a fixed mold (2) and a movable mold (12).
The molten resin is injected and filled through the manifold (6) and the gate (8) formed in the above, and after cooling and solidifying, the movable mold (12) is molded with respect to the fixed mold (2). When opening, the pressure of the molten resin in the manifold (6) is reduced, and after the mold opening speed increases, the movable mold (12) is separated from the fixed mold (2) and the synthetic resin is removed. A method for molding a synthetic resin product to obtain the product (S). 2. A movable mold (12) and a fixed mold (2). A cavity (14) formed between these molds (12, 2) has a manifold (6) and a gate (2). 8) A mold that is configured to be injected and filled with the molten resin through 8), wherein the fixed mold (2) is a fixed plate (1) to which the fixed mold (2) is attached. So that when the fixed mold (2) is separated from the fixed plate (1), the volume of the manifold (6) increases and the pressure of the molten resin decreases. Is configured,
The fixed mold (2) is provided between the fixed mold (2) and the fixed plate (1) so that the movable mold (12) does not separate from the fixed mold (2) at the initial stage of mold opening. 2) A mold for molding a synthetic resin product, comprising a pressing means for pressing the movable mold in the direction of the movable mold (12). 3. The pressing means according to claim 2, wherein the pressing means comprises a spring (5,
5.), a mold for molding a synthetic resin product.