JP3072217B2 - Injection molding method - Google Patents

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 for synthetic resin.
About the law .

[0002]

2. Description of the Related Art Conventionally, when a synthetic resin is injection-molded, an injection molding apparatus having a structure as shown in FIG. 3 has been used.
The synthetic resin molded body was manufactured by the operation described below.

In FIG. 3, reference numeral 101 denotes an injection cylinder 10.
2. Synthetic resin supply unit for supplying resin pellets in 2, 103
Is a screw housed in the injection cylinder 102, 104
Is a heating device for melting and plasticizing the resin pellets in the injection cylinder 102; 105 is a cavity mold 106 and a core mold 10;
7, a mold 108 is a cavity mold 10
6 and the cavity formed by the core mold 107,
It communicates with a nozzle 111 of the injection cylinder 102 via a resin passage formed by a runner 109 and a sprue 110. Reference numeral 112 denotes a heat medium passage provided in the cavity mold 106 and the core mold 107.

As shown in FIG. 4 (a), the heat medium flow path 112 is formed by connecting small-diameter tubes at small intervals (pitch) to the cavity walls 11 of the cavity mold 106 and the core mold 107.
3 or a single-row tube having a large diameter is formed inside the cavity mold 106 and the core mold 107 at a large interval as shown in FIG. 4B.

The resin supplied from the synthetic resin supply unit 101 into the injection cylinder 102 is heated and melt-plasticized by the heating device 104, and then injected and filled into the cavity 108 through the resin passage from the nozzle 111 by the screw 103. .

In this case, hot water is previously flowed through the heat medium flow path 112 to heat the cavity mold 106 and the core mold 107, particularly the cavity walls 113 of the cavity 108, thereby facilitating the flow of the molten resin. After that, the resin is cooled and solidified as it is. The purpose of heating the cavity wall by flowing hot water is to obtain a molded body having a good surface appearance.

As a special molding method, hot water is caused to flow through the heat medium flow channel 112 until the injection filling of the molten resin into the cavity 108 is completed, and the cavity wall is heated.
The hot water is switched to cold water in the same heat medium flow channel 112 to lower the temperature of the cavity wall 113, thereby lowering the surface temperature of the resin filled in the cavity 108, solidifying the resin, and taking out the molded product. However,
In this method, it is necessary to heat and cool the entire mold, which takes time.

[0008]

In the injection molding of a general synthetic resin, the injection step of filling the cavity with the resin does not require much time, and the cooling step before removing the molded body from the cavity takes a lot of time. And most of the injection molding time is spent in this cooling step. In order to increase the efficiency of the cooling process and reduce the time, there is an attempt to stop the flow of the hot water through the heat medium flow path when the injection is started to suppress the rise in the temperature of the cavity wall and facilitate the transition to the cooling process. However, if the temperature of the cavity wall is low during injection,
Since the following problems occur, it is necessary to increase the mold temperature. As a result, the time required for cooling cannot be reduced. (1) In the case of a synthetic resin having a high viscosity such as polycarbonate, for example, a portion in contact with the mold surface at the time of injection is rapidly cooled to form a so-called skin layer. Need to be larger. (2) In the case of thin-wall molding, the injection pressure is increased as in the above case. (3) The surface transferability deteriorates. (4) Weld lines become conspicuous in the molded product. (5) When the humidity is high and the mold is at a low temperature, the surface of the cavity is easily exposed.

In the conventional injection molding apparatus described above, heating of the cavity wall 113 when filling the cavity 108 with resin by injection and cooling of the cavity wall 113 when removing the resin molded body from the cavity 108 are performed. However, it is necessary to heat and cool the mold 105 having a large volume and a large heat capacity, which takes a long time.

The volume of the object to be heated and cooled is large,
If the heat capacity is large, there is a problem that the heat energy loss is also large.

The present invention provides a cavity type or a core type,
In particular heating of the cavity wall, it cooled to taking less time, and it is an object of the this <br/> to provide a small injection molding process heat energy loss.

[0012]

In order to achieve the above object, a cavity type or a core type used in the present invention is reduced.
One of them has two heating medium flow paths.

It is preferable that one of the two heat medium passages is formed near the cavity wall and the other is formed at a position away from the cavity wall.

Further, it is effective that the diameters of the two heat medium flow paths are different from each other, and the diameter of the flow path formed near the cavity wall does not exceed the diameter of the other flow path. .

Further, in order to achieve the above object, in the injection molding method of the present invention, when the mold is heated, the heating medium is separated from the cavity wall in the heating medium flow path formed near the cavity wall. Air flows through the heat medium flow path formed at
Heating by preventing heat conduction by filling or filling
When cooling the mold, the cooling medium flows into the flow path near the cavity wall and cools the flow path away from the cavity wall
Inflow or filling medium to reinforce cooling
is there.

[0016]

In the injection molding method [act above description, the heat medium flow passage located on the cavity wall is heated cavity wall
The heat medium flow path located inside the mold separated from the cavity wall has the function of reinforcing the above-mentioned heating and cooling or preventing the conduction of heat, so that the heating and cooling of the cavity wall can be efficiently performed. Can be done well in a short time.

When the resin is injected and filled into the cavity, hot water as a heating medium is flowed or filled in one of the heat medium flow passages located near the cavity wall, and air is flowed or filled in the other flow passage. Then, the cavity wall is easily heated by the hot water.

The flow path in which air is present functions as a heat insulating material, and the conduction of hot water to the inside of the mold is reduced, so that the heat capacity of the cavity type and the core type becomes the same as that of the conventional case. And the cavity wall is heated in a short time.

Further, since the heat conduction area in the mold is considerably reduced due to the presence of the flow path filled with air and filled with air, the heat resistance is increased and the flow of heat is reduced. The heat is hardly transmitted to the inside of the mold, and most of the heat can be used for heating the cavity wall side, the heating time is shortened, and the amount of heat is small.

Next, when cooling the cavity wall in order to take out the resin molded body from the cavity, when water is flown or filled in the two heating medium channels, the heated portion is:
Since the heat capacity is small only in the mold portion existing between the flow path through which the air flows and the cavity wall, the cavity wall is quickly cooled in a short time and the temperature is lowered.

Since the mold temperature can be raised and lowered in a short time as described above, the heat energy loss is small. In particular, when the mold temperature is raised, the heat energy loss is reduced due to the heat insulation effect of the flow path in which air exists. Since the cavity wall becomes less heated, the temperature of the hot water supplied may be lower than that of the conventional case in order to obtain the mold temperature in the conventional case. Can be made higher than before so that low-pressure molding is also possible.

Further, if the diameter of the heat medium flow path provided near the cavity wall is set not to exceed the diameter of the other heat medium flow path, the amount of heat exchange to the whole mold is greatly reduced, and the cavity is reduced. The wall can be heated and cooled effectively,
You.

In the two heat medium passages, when the other heat passage is positioned between one of the heat medium passages so that they do not overlap with each other, the heat medium flowing in each of the flow passages efficiently acts on the cavity wall. In addition, the heat conduction area formed between the two flow passages is reduced, and heat loss into the mold is reduced, so that heating and cooling of the cavity wall become easy.

[0024]

1 and 2, an embodiment of the present invention will be described.

In FIG. 1, reference numeral 1 denotes a synthetic resin supply unit for supplying resin pellets into the injection cylinder 2; 3, a screw housed in the injection cylinder 2; and 4, a heating device for melting and plasticizing the resin pellets in the injection cylinder 2. The apparatus 5 is a mold composed of a cavity mold 6 and a core mold 7, and 8 is a cavity formed by the cavity mold 6 and the core mold 7.
It communicates with the nozzle 11 of the injection cylinder 2 via a resin passage composed of a runner 9 and a sprue 10. Reference numeral 12 denotes a first heat medium flow passage which is bored in the cavity mold 6 and the core mold 7, and is located near the cavity wall 13. Reference numeral 14 denotes a second heat medium flow passage formed in the cavity mold 6 and the core mold 7. The second heat medium flow passage is located farther from the cavity wall than the first heat medium flow passage 12, has a larger diameter, and is located between the flow passages 12. And are arranged so that they do not overlap.

The first heat medium flow path 12 is connected to a heating medium source 16 and a cooling medium source 17 via a switching valve 15 to form a circulation flow path 18 indicated by a two-dot chain line. 14
Are connected to a heating medium source 20, a cooling medium source 21, and an air source 22 via a switching valve 19, respectively, to form a circulation channel 23 indicated by a dashed line. The circulation channel 1 in the core mold 7
Illustrations of 8 and 23 are omitted.

Next, the operation of the injection molding apparatus having the above-described configuration will be described. First, when the mold 5 is heated in the injection molding step, hot water flows from the heating medium source 16 into the first heating medium flow path 12, and the room wall 13 is filled with room temperature air from the air source 22 into the second heating medium flow path 14. Is heated by warm water.

In this case, since the air filled in the second heat medium flow path 14 exhibits a heat insulating effect, the mold heated by the hot water has a portion extending from the cavity wall 13 to the surface of the second heat medium flow path 14. That is, the heat capacity is small and the temperature rise time is short because the portion A in FIG. 2 is not the entire mold and the cavity wall 13 reaches the predetermined temperature in a short time.

Further, due to the presence of the second heat medium flow path 14 filled with air, the heat conduction area of the mold is reduced, the thermal resistance is increased, the heat conduction to the inside of the mold is reduced, and the heat energy loss is reduced. Less than

The resin pellets supplied from the synthetic resin supply unit 1 into the injection cylinder 2 while the cavity wall 13 is heated are melt-plasticized by the heating device 4 and
Is injected into the cavity 8 by the screw 3 through the resin passage.

At the time of cooling the mold 5 in the next cooling step, normal-temperature cooling water is supplied from the cooling medium source 17 to the first heat medium flow path 12 and from the cooling medium source 21 to the second heat medium flow path 14. When the heat medium flows in, the heat medium passages 12 and 14 are positioned so as not to overlap with each other, so that heat transfer occurs from the entire surface of the cavity wall 13 and a portion to be cooled (portion A in FIG. 2) has a small heat capacity. The wall 13 is quickly cooled to a low temperature in a short time, so that the molded body can be easily taken out.

Therefore, heating and cooling of the cavity mold 6 and the core mold 7, especially the cavity wall 13, can be efficiently performed in a short time.

In the above description, an example is shown in which the heat medium passages 12 and 14 are embedded in both the cavity type 6 and the core type 7. However, it is confirmed that even if only the heat medium channels 12 and 14 are embedded in either one of them, a sufficient effect can be obtained. Have been. In the above description, an example is shown in which hot water flows into the first heat medium flow path 12 during heating, air is filled in the second heat medium flow path 14, and cooling water flows into both flow paths 12, 14 during cooling. However, if the heating and cooling times are to be shortened at the expense of some heat energy loss, the following may be performed.

That is, (a) hot water flows through both flow paths 12 and 14 during heating, and cooling water flows through both flow paths 12 and 14 during cooling.

(B) Hot water flows through the first heat medium flow path 12 during heating and cooling water flows during cooling, and the second heat medium flow path 14 is filled with cooling water during heating and cooling. And keep it.

Further, in the above embodiment, the first heat medium passage 1
The second and the second heat medium flow passages 14 have been described as examples including a plurality of hole-shaped passages formed by piercing a mold. It may be formed by embedding a tube made of various materials in a meandering shape in a mold.

The size and arrangement of the first heat medium passage 12 and the second heat medium passage 14 are preferably as shown in FIG. 2 from the viewpoint of thermal efficiency. In other words, in the case of FIG. 2A, the diameter d of the first heat medium flow path 12 is small, the diameter of the second heat medium flow path 14 is large and the same as the pitch p of the flow path 12, and FIG.
In the case of (b), the diameter and pitch of the two flow paths 12 and 14 are the same and the flow path 14 is located between the flow paths 12 to reduce the heat conduction area in the mold and to reduce the cavity wall 1.
The channel is made to face the entire surface of the device 3. FIG. 2 (c)
In the case of (1), the diameter of the second heat medium flow path 14 is increased so that most of the diameter does not overlap with the first heat medium flow path 12 to reduce the heat conduction area.

A hole tube having a diameter of 3.0 mm is formed near the cavity wall 13 in the cavity mold 6 and the core mold 7 so that the pitch between the hole tubes is 6.0 mm. As a road 12, a hole pipe having a diameter of 6.0 mm was used.
As shown in (a), the second heat medium flow path 14 is formed separately from the first heat medium flow path 12 so as to be spaced apart from the cavity wall so that the pitch between the holes becomes 3.0 mm. About 12
When the pressurized water at 0 ° C. is flowed and the flow path 14 is filled with air at room temperature, the time for heating the cavity wall 13 to a predetermined temperature (100 ° C.) is about 30 seconds.
When flowing normal-temperature cooling water through 14, the cavity wall 13 was cooled to a predetermined temperature (40 ° C.) for about 40 seconds.

On the other hand, a hole pipe having a diameter of 3.0 mm is used and a hole is drilled near the cavity wall 113 so that the pitch between the hole pipes becomes 6.0 mm to form a heat medium passage 112 as shown in FIG. And about 120 ° C when heated with pressurized water, about 60 hours
Seconds, then about 30 minutes when cooled with normal temperature cooling water.
It takes 0 seconds, and it can be seen that it takes less time to heat and cool the cavity wall in this embodiment.

[0040]

Since the present invention is configured as described above, it has the following effects.

When the resin is injected and filled into the cavity,
The cavity wall can be efficiently and quickly heated by the heating medium present in the heat medium flow path located in the vicinity thereof, so that it can be quickly and quickly heated, so that good injection filling can be performed.When removing the resin molded body from the cavity, The cavity wall can be cooled in a short time by the cooling medium existing in the heat medium flow path located in the vicinity of the cavity wall, and the molded body can be released, so that the molding time can be shortened.

[Brief description of the drawings]

FIG. 1 is a sectional view of an injection molding apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a mold in the injection molding apparatus.

FIG. 3 is a sectional view of a conventional injection molding apparatus.

FIG. 4 is a sectional view of a main part of a mold in the injection molding apparatus.

[Explanation of symbols]

 6 Cavity type 7 Core type 8 Cavity 12 First heat medium channel 13 Cavity wall 14 Second heat medium channel

Claims (1)

(57) [Claims] At least a cavity type or a core type
Near the cavity wall and the cavity wall
Heat medium flow paths are formed at separate positions, and the
Before and during filling of the resin into the
The heating medium is separated from the cavity wall in the flow path near the wall.
The air flows into or fills the flow channels
During cooling, the flow path near the cavity wall and the cavity
The cooling medium may flow into the channels separated from the
Or injection molding method.