JPH08244072A - Injection mold and molding method - Google Patents

Abstract

PURPOSE: To raise the temperature of a cavity surface in a short time by providing a high-temperature and high-pressure gas supply port opened at the cavity in a cavity block and a high-temperature and high-pressure gas exhaust port at the parting surface of the block and a core block. CONSTITUTION: High-temperature gas is supplied to a passage 24 and a gas reservoir 25 opened at a fixed side mold plate 3 via a channel 23. At this time, a sprue bush is disposed at a retracted position. The gas is supplied to a sprue bush hole 26 to become a cavity to reduce its loss and to rapidly heat the surface of a cavity 8 with large volume. The gas supplied to the cavity 8 is arrived at a gap 27 provided at the parting surface while heating the surface of the cavity 8, and recovered for reuse to a cooler 33 via exhaust passages 29, 30 and further exhaust channels 31, 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection mold and a molding method for supplying high temperature and high pressure gas into a cavity to improve quality and productivity.

[0002]

2. Description of the Related Art In a conventional injection molding die and molding method, a temperature-controlled heat medium is circulated in a fixed mold and a movable mold before the molten resin is filled in the cavity to keep the surface of the cavity as constant as possible. It has been done so that it is placed and filled with molten resin. Further, in the conventional injection molding, the temperature of the surface of the cavity is kept constant by flowing the cooling medium into the cooling grooves provided in the fixed die and the movable die near the cavity. It is well known that the surface temperature of the cavity has a great influence on the appearance quality of the molded product, such as jetting, flow mark, silver streak, or short shot, and the molding time (or cooling time).

On the other hand, in injection molding, the high surface temperature of the cavity at the time of filling the molten resin means that the filling of the molten resin into the cavity can be easily carried out at a low pressure, and the appearance defect of the molded product can be eliminated. By filling at a high pressure, it is possible to obtain a glossy molded product having excellent transferability during printing. However, if the surface temperature of the cavity is raised, it will take time to cool the molded product to a temperature at which it can be taken out.
There remains a problem that productivity will deteriorate.

Therefore, it is ideal that the surface temperature of the cavity is high at the time of filling the molten resin and the temperature of the cavity becomes low immediately after the completion of the filling, and various techniques have been proposed for this purpose.

For example, Japanese Patent Publication No. 45-22020 discloses a method in which a heating fluid is supplied by a valve device in an injection nozzle and discharged from a parting line. Further, Japanese Patent Application Laid-Open No. 2-162007 describes an example of induction heating using a high-frequency current for heating a mold, and Japanese Patent Application Laid-Open No. 1-241408 discloses heating by a heating element. Examples are given. Further, Japanese Patent Application Laid-Open No. 6-170943 describes a method in which high temperature air is supplied from a valve and discharged from a parting surface.

[0006]

However, according to the method described in Japanese Patent Publication No. 45-202020, since the heating fluid is supplied from the gate having a very small cross-sectional area, a large amount of heating fluid can be discharged. Supply is difficult.
Also, providing a temperature difference between the surface and deep layers of the cavity is
Since the mold is made of a metal material, the heat applied to the surface layer diffuses to the whole, and it is difficult to provide a temperature difference between the surface layer and the deep layer.

Further, in the method of induction heating using a high frequency current described in Japanese Patent Laid-Open No. 2-162007, the equipment cost of the high frequency oscillator is expensive, and the heating coil is manufactured each time according to the shape of the cavity. It is necessary and lacks versatility.

Further, in the case of a mold heated by a heating element described in Japanese Patent Laid-Open No. 1-241408,
It can be easily heated in the case of heating a flat-plate-shaped cavity, but in the case of a cavity with a complicated shape having irregularities, it is necessary to manufacture a heating element that matches the shape of the cavity, which makes the manufacturing cost expensive. Furthermore, in addition to the problem that the heat efficiency is poor due to heating by radiant heat and the temperature distribution on the cavity surface is not uniform, it is necessary to heat the entire volume of the fixed mold and movable mold, and it is necessary to heat the mold and to cool the molten resin. There is a problem that it takes time.

Further, in the method described in Japanese Patent Laid-Open No. 6-170943, it is not suitable to send a large volume of air into the cavity because the opening area of the hot air blowing portion cannot be made large. Moreover, since the cross-sectional area of the air discharge portion is too small, there is a problem that the pressure loss becomes too large to discharge a large volume of air.

In addition, an example of a die in which the die surface is coated and heated by a high temperature gas is described in JP-A-5-38721, but there is a problem that the cooling time becomes long.

Although some examples have been cited above, these techniques have a common problem that although the appearance quality is improved, it takes a long time to cool after molding and the equipment cost is high. The present situation is that it is used only for some special forming processes, for example, where the required quality is emphasized in terms of productivity and cost.

The present invention has been made in view of the above problems, and an object of the present invention is to solve these problems, to improve the quality, and to reduce the time required for cooling. An injection molding die and a molding method with high productivity are provided.

[0013]

The injection mold of the present invention according to claim 1 is composed of a fixed mold and a movable mold, and is an inlay which slides around the cavity of the parting surface in the opening / closing direction of the mold. An injection molding die provided with a section,
A thin cavity block and a core block that form a cavity are provided in the fixed mold plate of the fixed mold and the movable mold plate of the movable mold, respectively, and cooling holes, a cavity block, and a core are formed in the cavity block and the core block. An air heat insulating layer is provided around the contact between the fixed-side mold plate and the movable-side mold plate of the block, and further, a high-temperature high-pressure gas supply port opening to the cavity is provided in the cavity block, and a cavity block-core block party. And a discharge port for high-temperature high-pressure gas is provided on the ring surface.

In the injection mold of the present invention according to claim 2, a sprue bush communicating with the cavity from the cavity block is provided in the fixed mold of the injection mold according to claim 1, and the advance of this sprue bush is made. It is characterized in that it is carried out by utilizing the advancing force of the nozzle of the injection molding machine, and the retreating is carried out by the reaction force of the spring embedded around the sprue bush.

In the molding method of the present invention as set forth in claim 3, the injection molding die set forth in claim 1 or 2 is used, and after the molten resin is injected into the cavity, the cooling groove is formed between the cavity block and the core block. The mold is cooled by circulating the cooling medium only during the period from the completion of the filling of the molten resin to the start or the end of the removal of the molded product.

The thickness of the thin cavity block and the core block provided in the injection molding die of the present invention according to claim 1 is determined by the size and shape of the cavity, and this thickness is 20. -40 mm is preferred.

The cavity block and the core block are provided so as to be fitted into the fixed side and the movable die, and a thermal insulation layer formed by air is provided by providing a very small gap between the surfaces abutting each other. It is possible to improve the efficiency at the time of heating or cooling by interposing.

[0018]

According to the injection molding die of the present invention as set forth in claims 1 and 2, a thin cavity block and a core block for forming a cavity in the fixed mold plate of the fixed mold and the movable mold plate of the movable mold. Are provided in each of the cavity block and the core block, and a cooling hole is provided in the cavity block and the core block. Since a high-temperature high-pressure gas supply port that opens into the cavity and a high-temperature high-pressure gas discharge port are provided on the parting surfaces of the cavity block and core block,
By supplying a large volume of high temperature and high pressure gas, the wind speed can be increased.
It is possible to raise the temperature of the cavity surface in a short time and evenly heat every corner. Further, since the gas is vented by the air vent, the appearance quality is improved, and it is possible to easily form a thin wall or a complicated shape.

Further, since the thin cavity block and the core block have a small heating volume, the temperature can be raised to a high temperature in a short time, and further, the cooling is performed while the fixed die and the cavity block and the movable die and the core block are brought into contact with each other. Since the holes are provided and air is present, it is possible to effectively prevent heat from escaping during heating of the surface of the cavity.

Due to the effect of the thin cavity block and core block having a small heat capacity and the cooling groove provided in the periphery, the molten resin after the filling is quickly cooled in a short time, and the productivity is improved by the shot-up. Can be achieved.

Further, the high-temperature air generator can be applied to any mold, and the mold can be provided with a gap having an air blow-in part and an air vent for discharging the high-temperature air, or a spigot part. Well, the equipment cost can be reduced.

In the molding method of the present invention according to claim 3, after the molten resin is injected into the cavity, the cooling grooves of the cavity block and the core block are filled with the molten resin until the start or the end of taking out the molded product. Since the cooling medium is circulated only during the period to cool the mold, the inflow of the cooling medium is interrupted while heating the surface of the cavity, and the surface temperature of the cavity is heated more quickly and effectively. You can

Further, by injecting high temperature and high pressure air into the cavity from the air blowing part and discharging it from the gap of the spigot part, the gas in the cavity can be easily discharged, and the burning and short shot of the molded product can be eliminated. It

In the injection molding die and molding method of the present invention, since the surface temperature of the cavity can be raised to a high temperature, the solidification of the molten resin in the cavity is delayed and the flow is facilitated, so that the following effects can be expected. . 1) Improving transferability and appearance quality of molded products. 2) Capable of molding large and thin molded products. 3) Low pressure molding is possible. 4) Molding failure-elimination of weld line, flow mark, silver streak, and floating phenomenon of reinforcing material.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of an injection mold of the present invention, showing a mode before the molten resin is filled in the mold closed state. In FIG. 1, 3 is a fixed-side mold plate of the fixed mold 1, and 4 is a movable-side mold plate of the movable mold 2. Parting surfaces 5, 6, and 7 are provided at the boundary between the fixed-side mold plate 3 and the movable-side mold plate 4, and the parting surface 7 has a spigot structure that can slide in the mold closing direction.

Inside the fixed-side mold plate 3 and the movable-side mold plate 4, a cavity block 9 and a core block 10 which form a cavity 8 for molding a molded product are provided.
The cavity block 9 and the core block 10 are fitted and fixed in the fixed-side mold plate 3 and the movable-side mold plate 4, respectively.

Reference numerals 11 and 12 denote air insulating layers provided on the contact surfaces of the fixed side mold plate 3, the movable side mold plate 4, the cavity block 9 and the core block 10, respectively.

Reference numerals 13 and 14 denote cooling holes provided in the cavity block 9 and the core block 10, respectively, and a cooling medium is supplied to the cooling holes 13 and 14 to pass through the cavity block 9 and the core block 10. In this way, the molten resin in the cavity 8 is cooled.

A sprue bush 17 having a locate ring and a sprue 16 for injecting the molten resin into the cavity 8 is provided at substantially the center of the stationary mold plate 3.

Reference numeral 18 is a nozzle provided on the injection molding machine side, and 19 is a passage for the molten resin. Reference numeral 20 is a coil spring provided on the outer periphery of the sprue 16, and the sprue bush 17 can be moved to the nozzle 18 side after the injection of the molten resin. In the mold of the present embodiment, the sprue bush 17 adopts a method of moving the fixed-side mold plate 3 and the cavity block 9 forward and backward in the mold closing direction.

The heating of the cavity surface by the high temperature gas will be described below with reference to FIG. This Figure 2
It shows a state just before the completion of the mold clamping in the mold closing process, and a slight gap δ is provided on the parting surface. In this state, the parting surface 7 is the fixed side template 3
And the movable side mold plates 4 are fitted to each other.

The molding method of the present invention employs a two-stage system. In the first-stage mold closing process, as shown in FIG. 2, a gap δ is provided, and the second-stage mold closing process is performed. Then, the gap δ becomes 0, and the mold is completely closed. That is, in the mold closing step of the first stage, the surface of the cavity 8 in the hermetically sealed state is heated by the high temperature gas. At this time, the nozzle 18 maintains the retracted position before the injection of the molten resin.

Next, the supply and discharge of high temperature gas will be described. Reference numeral 22 denotes a gas heating device, which has a heater built therein and has a capability of raising the gas temperature to 250 ° C. to 350 ° C. Reference numeral 23 is a high temperature gas passage, and 24 is a high temperature gas passage formed in the fixed-side template 4. Further, 25 is a gas reservoir communicating with the passage 24, which is provided to reduce the flow resistance of the high temperature gas.

Reference numeral 26 denotes a sprue bush hole into which the sprue bush 17 is fitted when it is advanced. In the state shown in FIG. 2, the sprue bush 17 is in the retracted position and is therefore a cavity. The diameter of this sprue bush hole 26 is
It is the same as the outside diameter of the sprue bush 17, and is usually 20 m.
It is provided as thick as m to 30 mm so as to reduce the pressure loss when the high temperature gas flows and to quickly heat the surface of the cavity 8 with a large air flow.

The high temperature gas supplied to the cavity 8 reaches the gap 27 provided on the parting surface while heating the surface of the cavity 8 and passes through the discharge passages 29 and 30 and further discharge passages 31 and 32. After that, it is collected in the cooler 33 for reuse.

During the feeding stage, the hot gas is supplied to the hot gas as described above.
50 ° C to 350 ° C, but at the discharging stage, 150 ° C to
Since it is at a considerably high temperature of 250 ° C., a method of recycling it without discharging it to the atmosphere is preferable. Further, since the high-temperature gas is used intermittently, the blower 34 is continuously operated while being switched by the switching valve 35 to be sent to the cooler 33 via the passage 36 and circulated.

The molding method of the present invention will be described with reference to the flow chart of the molding process of FIG. By the above heating method,
When the surface of the cavity 8 is heated to the set temperature, the heating device 22 is stopped and the supply of high temperature gas is stopped.

Then, in the second step, the mold closing is completed and the injection of the molten resin is started. That is, the nozzle 18 of the injection molding machine is advanced, and the sprue bush 17 is advanced against the repulsive force of the coil spring 20. In this state, the sprue bush hole 26 is closed and the supply of hot gas into the cavity 8 is stopped. Further, the parting surface 5 is also closed at the same time, and the discharge of the high temperature gas is stopped.

Subsequently, the mold closing of the second step is completed, the nozzle 18 is advanced, and the molten resin is injected into the cavity 8 to start the molding step.

After injecting the molten resin into the cavity 8, cooling holes 13 and 14 in the cavity block 9 and the core block 10 are formed.
In addition, the cooling medium is circulated only during the period from the completion of the filling of the molten resin to the start or the end of the taking out of the molded product for cooling. After cooling, take out the molded product by opening the mold and
The cycle is complete.

At this time, while the surface of the cavity 8 is being heated by the high temperature gas, the flow of the cooling medium is interrupted, so that the surface temperature of the cavity 8 can be heated more quickly and effectively. ing.

In the injection molding die of the present invention, the hot gas supply path and the high temperature gas discharge path are two in the embodiment, but it is possible to increase the quantity according to the capacity of the cavity 8. is there.

Further, although the cavity block and the core block are provided as one block in this example, they may be provided separately as needed. As the material of this block, an aluminum material is preferably used from the viewpoint of heating efficiency and high temperature.

The closer the heating temperature of the cavity block and the core block is to the temperature of the molten resin, the more desirable it is in terms of the quality of the molded product, but on the other hand, the cooling takes too much time, the cycle becomes long, and the productivity is affected. Therefore, it is preferable to decide after considering quality and productivity.

[0045]

According to the injection molding die of the present invention as set forth in claims 1 and 2, a thin cavity block and a core for forming a cavity in a fixed mold plate of a fixed mold and a movable mold plate of a movable mold. Blocks are respectively provided, cooling holes are provided in the cavity block and the core block, and an air heat insulating layer is provided around the abutting contact between the fixed side mold plate and the movable side mold plate of the cavity block and the core block. The cavity block has a high-temperature high-pressure gas supply port that opens into the cavity and a high-temperature high-pressure gas discharge port on the parting surface between the cavity block and the core block. In addition, the wind speed can be increased, the temperature of the cavity surface can be raised in a short time, and even heating can be performed uniformly in every corner. Further, since the gas is vented by the air vent, the appearance quality is improved, and it is possible to easily form a thin wall or a complicated shape.

Further, since the thin cavity block and the core block have a small heating volume, the temperature can be raised to a high temperature in a short time, and further, the cooling is performed while the fixed die and the cavity block and the movable die and the core block are in contact with each other. Since the holes are provided and air is present, it is possible to effectively prevent heat from escaping during heating of the surface of the cavity.

Due to the effect of the thin cavity block and core block having a small heat capacity and the cooling groove provided in the periphery, the molten resin after the filling is quickly cooled in a short time, and the productivity is improved by the shot-up. Can be achieved.

Further, the high-temperature air generator can be applied to any mold, and the mold is simply provided with a gap having an air blow-in portion and an air vent for discharging hot air, or a spigot portion. Well, the equipment cost can be reduced.

In the molding method according to the third aspect of the present invention, after the molten resin is injected into the cavity, the cooling grooves of the cavity block and the core block are filled with the molten resin until the start or the end of taking out the molded product. Since the cooling medium is circulated only during the period to cool the mold, the inflow of the cooling medium is interrupted while heating the surface of the cavity, and the surface temperature of the cavity is heated more quickly and effectively. You can

Further, by injecting high-temperature and high-pressure air into the cavity from the air blowing part and discharging it from the gap of the spigot part, the gas in the cavity can be easily discharged, and gas burning and short shot of the molded product are eliminated. It

In the injection molding die and molding method of the present invention, since the surface temperature of the cavity can be raised to a high temperature, the solidification of the molten resin in the cavity is delayed and the flow becomes easy, so that the following effects can be expected. . 1) Improving transferability and appearance quality of molded products. 2) Capable of molding large and thin molded products. 3) Low pressure molding is possible. 4) Molding failure-elimination of weld line, flow mark, silver streak, and floating phenomenon of reinforcing material. Therefore, it is preferably used as an injection mold and a molding method.

[Brief description of drawings]

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

FIG. 2 is a system diagram illustrating a method for heating the injection mold of FIG.

FIG. 3 is a flowchart illustrating steps of a molding method.

[Explanation of symbols]

 1 Fixed type 2 Movable type 3 Fixed side type plate 4 Movable side type plate 5, 6, 7 Parting surface 8 Cavity 9 Cavity block 10 Core block 11, 12 Air insulation layer 13, 14 Cooling hole 15 Locate ring 16 Sprue 17 Sprue bush 18 nozzle 19 passage 20 coil spring 22 heating device 23, 36 flow passage 24 passage 25 gas reservoir 26 sprue bush hole 27 gap 28 discharge groove 29, 30 discharge passage 31, 32 discharge passage 33 cooler 34 blower 35 switching valve

Claims (3)

[Claims] 1. An injection molding die comprising a fixed die and a movable die, wherein a spigot part that slides in the opening / closing direction of the die is provided around a cavity of a parting surface, the die being a fixed side of the fixed die. A thin cavity block and a core block that form a cavity are provided in the plate and the movable mold plate of the movable mold, respectively, and cooling holes are provided in the cavity block and the core block, and a fixed mold plate of the cavity block and the core block. An air insulating layer is provided around the abutting surface of the movable side mold plate with the movable side mold plate, and the high temperature high pressure gas is further provided on the parting surface between the cavity block and the core block and the supply port of the high temperature high pressure gas that opens into the cavity in the cavity block. And a discharge port of the injection mold are provided. 2. The stationary mold is provided with a sprue bush communicating with the cavity from the cavity block, the forward movement of the sprue bush is performed by utilizing the forward movement force of the nozzle of the injection molding machine, and the backward movement is around the sprue bush. The injection molding die according to claim 1, wherein the injection molding die is performed by a reaction force of a spring embedded in the. 3. Use of the injection molding die according to claim 1 or 2 to inject a molten resin into a cavity, and then take out a molded product after the molten resin is completely filled in the cooling grooves of the cavity block and the core block. A molding method, characterized in that a cooling medium is circulated until the start or end of the step to cool the mold.