JPH08156028A - Injection mold and injection molding method - Google Patents

Abstract

PURPOSE: To obtain a molded product which is excellent in appearance quality by a method wherein a surface of a cavity is heated by air at a high temperature to improve flow characteristics of a molten resin in the cavity. CONSTITUTION: In a injection mold comprising a fixed mold 1 and a movable mold 2, a cavity is formed by a cavity block 5 provided to the fixed mold 1 and a core block 6 provided to the movable mold 2. An faucet part 9 is, in a slidable manner, provided between the mold 1 and the movable mold 2 along an outer periphery of the cavity 4. A feed hole 10 for high temperature air and its discharge hole 11 are provided on a parting surface 3 between the cavity block 5 and the core block 6 by being interconnected with outside of the mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to injection molding dies and injection moldings characterized by supplying high temperature air into a cavity and then injecting a molten resin to improve the quality of an injection molded product. Regarding the method.

[0002]

2. Description of the Related Art In a conventional injection molding die and injection 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, so that the surface of the cavity is kept as close as possible. It has been practiced to set aside and fill with molten resin. Also, in conventional injection molding,
A cooling medium has been made to flow into cooling grooves provided in a fixed mold and a movable mold near the cavity so that the temperature of the cavity surface becomes constant. The surface temperature of this cavity depends on the appearance quality of the molded product, such as jetting, flow marks,
It is well known that silver streak, short shot and the like have a great influence on 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 has the advantage that the molten resin can be easily filled in the cavity at a low pressure and the appearance defect of the molded product can be eliminated. There is. But,
When the surface temperature of the cavity is increased, it takes time to cool the molded product to a temperature at which it can be taken out, and there is a problem that productivity is deteriorated. 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 filling,
For this purpose, various techniques have been proposed.

For example, as an example of controlling the temperature of the mold by blowing high temperature air, an example described in Japanese Patent Publication No. 45-22020 can be mentioned. In addition, JP-A-61-143
Japanese Patent Application Laid-Open No. 109 and Japanese Patent Application Laid-Open No. 2-162007 describe an example in which electric energy such as induction heating by a high frequency current is used for heating a mold. Furthermore, JP-A 1-2
In Japanese Patent No. 41408, an example in which a heat element is used for heating a mold is described.

[0005]

However, in the method of heating a mold with high temperature air described in Japanese Patent Publication No. 45-202020, a metal is used as the material of the mold and the surface layer of the cavity is heated by the high temperature air. The purpose is to heat only the high temperature, but there is a problem that it is very difficult to obtain the temperature difference due to the heat conduction characteristics of the metal.

Further, in the method of induction heating by a high frequency current described in the above-mentioned JP-A-61-143109 and JP-A-2-162007, the equipment cost of the high-frequency oscillator is high and the shape of the cavity is high. Therefore, there is a problem that the heating coil needs to be manufactured in each case and the versatility is lacking.

Further, in the case of the die by heating with a heating element described in the latter Japanese Patent Laid-Open No. 1-241408, heating of a flat plate-shaped cavity can be easily carried out, but there is unevenness and complexity. In the case of a cavity with a different shape, it is necessary to manufacture a heating element that matches the shape of the cavity, which results in high manufacturing costs, and because of the heating by radiant heat, the thermal efficiency is poor and the temperature distribution on the cavity surface is not uniform. In addition to the problem, there is a problem that it is necessary to heat the entire volume of the fixed mold and the movable mold, and it takes time to heat the mold and cool the molten resin.

Another example of a die in which the die surface is coated and heated by a high temperature gas is described in Japanese Patent Laid-Open No. 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 the appearance quality is improved, but it takes 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 and to heat the surface of the cavity with high temperature air to form the cavity. It is intended to provide an injection molding die and a molding method capable of improving a flow characteristic of a filling resin in the inner part and obtaining a molded article having excellent appearance quality.

[0011]

According to another aspect of the present invention, there is provided an injection molding die comprising a fixed die and a movable die, wherein a cavity block provided in the fixed die and a movable die are provided. A cavity is formed by the provided core block, and a spigot portion is provided slidably between the fixed die and the movable die on the outer periphery of the cavity, and high temperature air is provided on the parting surface between the cavity block and the core block. The supply hole and the discharge hole are provided so as to communicate with the outside of the mold.

According to a second aspect of the injection molding die of the present invention, the cavity block and the core block of the injection molding die according to the first aspect are made of a material having a small heat capacity. Further, in the injection mold of the present invention according to claim 3, the fixed mold and the cavity block of the injection mold according to claim 1 and the movable mold and the core block are provided with heat-insulating surfaces, respectively. An air layer is provided.

According to a fourth aspect of the injection molding method of the present invention, the injection molding die according to the first aspect is used, and high temperature air is supplied from a supply hole provided in the parting surface in a weak crown open state. The cavity is then heated to close the mold completely, and the molten resin is injected into the cavity for molding.

The thickness of the cavity block and core block provided in the injection molding die of the present invention is determined by the size and shape of the cavity, and the thickness is preferably 20-40 mm. . Further, as a metal material used for the cavity block and the core block, an aluminum alloy having a small heat capacity is suitable. By using this aluminum alloy, it is possible to increase the temperature rising rate of the cavity and obtain a high temperature. is there.

The cavity block and the core block are provided so as to be fitted into the fixed side and the movable mold, and a gap in which air is interposed is provided between the surfaces abutting each other so as to be thermally insulated by the air. By interposing the layers, it is possible to improve efficiency during heating and cooling.

[0016]

In the injection molding die of the present invention according to claim 1 and the injection molding method of the present invention according to claim 4, a cavity block and a core block are provided in each of the fixed die and the movable die, and the cavity is provided. A spigot part is provided between the fixed mold and the movable mold on the outer periphery of the mold, and a high-temperature air supply hole is provided on the parting surface between the cavity block and the core block. By supplying air to the cavity and heating the cavity, it is possible to improve the flow characteristics of the molten resin, enable low-pressure molding, and mold a molded product with improved appearance quality.

In the injection molding die of the present invention of claim 2, since the cavity block and the core block are made of a material having a small heat capacity, the cavity is heated quickly by the high temperature air and is heated to a high temperature. It becomes possible to do.

In the injection-molding die according to the third aspect of the present invention, since the air layers for heat insulation are provided on the respective contact surfaces of the fixed die and the cavity block and the movable die and the core block. It is possible to efficiently and quickly heat the cavity with high temperature air and cool it after molding.

[0019]

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, 1 is a fixed type,
2 is a movable type. A parting surface 3 is provided at the boundary between the fixed die 1 and the movable die 2.

Inside the fixed mold 1 and the movable mold 2, there are provided a thin cavity block 5 and a core block 6 which form a cavity 4 for molding a molded product. The cavity block 5 and the core block 6 are provided. Are fitted and fixed in the fixed mold 1 and the movable mold 2, respectively.

A spigot portion 9 is provided on the outer periphery of the cavity 4 of the fixed mold 1 and the movable mold 2 so that the mold 4 slides smoothly as the mold is opened and closed.

A cavity 4 is provided at a substantially central portion of the fixed mold 1.
Further, a sprue bush 8 having a sprue 7 for injecting the molten resin is provided.

Reference numeral 10 denotes a high-temperature air supply hole that penetrates the core block 6 and reaches the cavity 4. The high-temperature air is supplied to the cavity 4 from the supply hole 10 and the high-temperature air after heating the cavity 4 is opposite. Discharge hole 1 provided on the side
It is designed to be discharged from the mold from 1. By supplying high temperature air to the cavity 4, the cavity block 5 and the core block 6 can be selectively heated.

Reference numerals 12 and 12a denote air layers for heat insulation provided on the contact surfaces of the fixed mold 1 and the cavity block 5, and the movable mold 2 and the core block 6, respectively. 6 can be efficiently heated.

FIG. 2 is a cross-sectional view showing a mode immediately before the mold closing of the injection molding die of the present invention, in which the mold is not completely closed but is in a weakly opened state. That is, the mold closing process in the injection molding using the present injection mold comprises a first process in which the mold is weakly opened and a second process in which the mold is completely closed.

That is, in the stage of the first step, a gap is provided between the fixed die 1 and the movable die 2 by the stroke S. The stroke S is usually preferably about 1 to 5 mm.

Therefore, in this state, the parting surface 3 and the cavity 4 are closed spaces due to the spigot portion 9, and in this state, high temperature air is supplied to the cavity 4 from the supply hole 10, and the cavity block 5 and the core block. 6 can be efficiently heated.

The supply of high temperature air will be described below.
In FIG. 1 or FIG. 2, 13 is a blower, and the air supplied from the blower 13 is heated to a high temperature by a heater 14 and passes through an electromagnetic switching valve 15 to supply holes 10.
Is supplied to the cavity 4.

The high temperature air supplied to the cavity 4 rapidly heats the cavity block 5 and the core block 6, and the air used for this heating is deprived of heat, cooled, and discharged from the exhaust hole 11, It is sent again to the blower 13 via the electromagnetic switching valve 16 provided on the discharge side, and is circulated for use.

The tip of the hot air supply hole 10 is communicated with a supply groove 10a provided in the width direction of the parting surface 3 of the core block 6, and is rapidly diffused over the entire surface of the cavity 4 to form a cavity block 5. And the core block 6 can be heated rapidly. The cooled air is sucked into the exhaust hole 11 through the exhaust groove 11a provided on the opposite side and exhausted.

Therefore, the high-temperature air flowing into the cavity 4 diffuses and flows in the cavity 4 at high speed, and enables efficient heating of the cavity block 5 and the core block 6 in a short time.

The injection molding method using the injection mold of the present invention will be described below. As shown in FIG. 2, first, in the first step, the mold is closed until the weak crown mold is opened. Upon receiving this mold closing completion signal from the controller of the injection molding machine, the electromagnetic switching valves 15 and 16 are switched. By this switching, high temperature air is supplied into the cavity 4 to rapidly heat the cavity block 5 and the core block 6.

The supply of high temperature air is stopped when the surface of the cavity 4 rises to a constant temperature or after the electromagnetic switching valves 15 and 16 have been switched for a fixed time.

Subsequently, in the second step, the mold is completely closed, and the molten resin is injected into the cavity 4 for molding. After that, one cycle can be completed by removing the molded product by holding the pressure and cooling and opening the mold.

Also in the injection mold of the present invention, the cavity block 5 and the core block 6 are provided with respective cooling holes 17 and 18, so that the molten resin in the cavity 4 is cooled. Has become.

The cooling of the mold is interrupted while the hot air is supplied to the cavity 4, and is intermittently performed when the injection molding with the molten resin is completed so that the cavity 4 can be efficiently heated. It is possible to Further, the supply temperature of the high-temperature air is preferably as high as possible, but in consideration of maintaining the accuracy of the mold and the heat resistance of the equipment used, it is usually preferable to be 200 to 350 ° C.

As described above, by heating the cavity block 5 and the core block 6 forming the cavity 4, the flow characteristics of the molten resin in the cavity 4 are improved, and molding can be performed even at a relatively low pressure. Therefore, it is possible to obtain a molded product with excellent quality.

[0038]

The injection mold of the present invention according to claim 1,
And in the injection molding method of the present invention according to claim 4,
A cavity block and a core block are provided in each of the fixed die and the movable die, and a spigot portion is provided between the fixed die and the movable die on the outer periphery of the cavity, and high temperature air is provided on the parting surface between the cavity block and the core block. Since the supply hole is provided, hot air is supplied to the cavity while the mold is slightly open, and the cavity is heated to improve the flow characteristics of the molten resin, enabling molding at low pressure, It is possible to mold a molded product having excellent appearance quality without the occurrence of marks, jetting, short shots, weld lines, and the like. Further, it is possible to obtain a molded product having improved transferability and good surface gloss.

In the injection molding die of the present invention as defined in claim 2, since the cavity block and the core block are made of a material having a small heat capacity, the cavity is heated by the high temperature air quickly and is heated to a high temperature. It becomes possible to do.

In the injection-molding die of the present invention as defined in claim 3, the fixed mold and the cavity block, and the movable mold and the core block are provided with air layers for heat insulation on their respective contact surfaces. It is possible to efficiently and quickly heat the cavity with high temperature air and cool it after molding.

Furthermore, due to the effect of the thin cavity block and core block having a small heat capacity and the surrounding air tank, the molten resin after the filling is quickly cooled in a short time, and the productivity is improved by the shot-up. Can be improved.

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 as set forth in claim 4, since the inflow of the cooling medium is interrupted while the surface of the cavity is being heated, the surface temperature of the cavity and further the cavity block and the core block can be swiftly increased. , Can be heated effectively.

In the injection molding die according to the first aspect of the present invention, the gas in the cavity can be easily discharged through the gap having the spigot portion, and the gas burn and short shot of the molded product can be eliminated.

Therefore, it can be suitably used as an injection molding die 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 cross-sectional view showing an aspect of the injection molding die of the present invention immediately before the mold is closed.

[Explanation of symbols]

 1 Fixed Type 2 Movable Type 3 Parting Surface 4 Cavity 5 Cavity Block 6 Core Block 7 Sprue 8 Sprue Bushing 9 Inlay Part 10 Supply Hole 11 Exhaust Hole 10a Supply Groove 11a Exhaust Groove 12, 12a Air Layer 13 Blower 14 Heater 15, 16 Solenoid switching valve S clearance

Claims (4)

[Claims] 1. An injection molding die comprising a fixed mold and a movable mold, wherein a cavity is formed by a cavity block provided on the fixed mold and a core block provided on the movable mold, and the fixed mold on the outer periphery of the cavity. And a movable die are provided with a spigot portion slidably, and a hot air supply hole and a hot air discharge hole are provided on the parting surfaces of the cavity block and the core block so as to communicate with the outside of the die. An injection molding die characterized in that. 2. The injection molding die according to claim 1, wherein the cavity block and the core block are made of a material having a small heat capacity. 3. The injection mold according to claim 1, wherein an air layer for heat insulation is provided on each of the contact surfaces of the fixed mold and the cavity block and the movable mold and the core block. 4. The injection molding die according to claim 1, wherein the cavity is heated by supplying high temperature air from a supply hole provided in a parting surface in a weakly opened state, and then the die is completely completed. And a molten resin is injected into the cavity to carry out molding.