HK1118253B - Mold for injection molding machine - Google Patents

Description

Mold for injection molding machine

Technical Field

The present invention relates to a mold for an injection molding machine, and more particularly, to a mold including a separate intermediate mold formed of a groove or core surface which can be heated before injection molding and can be cooled simultaneously with injection molding, so that injection molding can be completed with a short injection molding cycle. Further, the present invention is directed to a molding apparatus in which a high-quality injection-molded product can be manufactured by maintaining an edge region of a mold surface at a desired temperature during injection molding.

Background

The process of injection molding a synthetic resin or metal is a manufacturing method of injecting a molten synthetic resin or metal between a fixed mold (cavity mold) with a recess and a movable mold (core) with a core and then cooling the injected synthetic resin or metal to obtain a recess-shaped molded product.

During injection molding, it is preferable that the mold and the molten material have the same temperature, if possible, when the molten material is injected. The reason is that the flow characteristics of the injected material and the transfer characteristics of the cavity surface pattern can be improved, and the deformation due to the residual stress after the molten material is hardened can be reduced. Also, the mold preferably has a lower temperature after the molten material is completely injected. Thus, the injection material can be rapidly cooled, and the injection molding cycle can be shortened, thereby improving productivity.

However, if the mold is heated in advance to increase its temperature, the flow and transfer characteristics are improved, but it takes a long time to cool the mold. Thus, there is a problem that the injection molding cycle is increased. On the other hand, in the case where the volume of the mold is reduced so that the mold can be rapidly cooled to shorten the injection molding cycle, the hardness and rigidity of the mold are also weakened. Thus, there is another problem in that the molded product may be deformed or its durability may be deteriorated.

Disclosure of Invention

Technical problem

An object of the present invention is to provide a molding apparatus having heating and cooling means in which a mold is maintained at a suitable temperature to maintain the flow and transfer characteristics of an injected molten material and then rapidly cooled during and after injection, thereby shortening the injection molding cycle, and thus enabling to improve productivity. That is, an object of the present invention is to provide a molding apparatus capable of solving the conflicting problems of taking much time to cool a mold when the temperature of the mold is increased, thereby possibly increasing the injection molding cycle, but breaking the flow and transfer characteristics when the size of the mold is reduced to rapidly cool the mold.

Further, another object of the present invention is to provide a molding apparatus capable of manufacturing a high-quality injection-molded product without deformation and capable of shortening the cycle time by allowing each region of the mold surface to be maintained at a desired temperature to control the cooling rate of the injection-molded product.

Technical scheme

According to an aspect of the present invention, there is provided a molding apparatus including a cavity mold fixed to an injection molding machine and formed to have a cavity surface for defining a cavity into which a molten injection material is injected, and a core mold formed to have a core surface and mounted to the injection molding machine, the core surface being engaged with the cavity mold to define the cavity, so that the core mold can be moved forward and backward to open or close the cavity by being guided by guide pins. In particular, the core mold is divided into a thin intermediate core mold plate having a core surface and a thick core mold support plate so that the core mold can be maintained at an appropriate temperature at the time of injection of the molten injection material and rapidly cooled after the injection is completed. Further, the core mold includes guide pins which protrude from the core mold support plate to be inserted into guide holes formed in the cavity mold when moving toward the cavity mold, and which mount the core mold through the intermediate core mold plate so that the intermediate core mold plate moves only in the front-rear direction. Further, the core mold includes a first spring installed between the intermediate core mold plate and the core mold support plate to separate the intermediate core mold plate and the core mold support plate from each other by an elastic force when the core mold moves backward to open the cavity. Further, a first heating means for heating the intermediate core mold plate is installed to a parting surface of the intermediate core mold plate, and a cooling means is installed to the core mold support plate so that the core mold support plate can be maintained at a predetermined temperature when coming into contact with the intermediate core mold plate to allow the intermediate core mold plate to be cooled.

According to the present invention, a core mold, serving as a movable mold, which is movably installed with respect to a cavity mold fixed to an injection molding machine, is divided into a thinner intermediate core mold plate and a thicker core mold support plate. Further, before they are joined, the intermediate core mold plate is heated by the heating means to a temperature suitable for injection molding, and the core mold support plate is cooled to a state where the intermediate core mold plate can be rapidly cooled when it comes into contact with the intermediate core mold plate. During the molten material is injected, the core mold support plate is moved toward the cavity mold to bring the intermediate core mold plate into close contact with the cavity mold. After the molten material is completely injected, the action of the heating means is stopped and the intermediate core mold plate, which is in contact with the core mold support plate, is rapidly cooled. Thus, the temperature of the core surface can be appropriately maintained to ensure excellent flow and transfer characteristics of the molten injection material at the time of injection. Further, since the molding device can be rapidly cooled while the injection of the molten material is completed, the cycle time of the injection molding can be further shortened.

In order to enhance the cooling effect of the intermediate core mold plate, the parting surfaces of the intermediate core mold plate and the core mold support plate are preferably in close contact with each other. Thus, a coil spring is used as the first spring to insert the guide pin therein. Preferably, a circular hole having a predetermined depth is formed at an edge portion of the core mold support plate to which the guide pin is fixed, so that the first spring can be completely inserted into the circular hole when the core mold support plate moves forward.

Further, the cavity mold of the molding apparatus according to the present invention may be divided into a thin intermediate cavity mold plate formed to have a cavity surface and a thick core mold cavity support plate formed to have a second guide hole, so that the cavity surface and the core surface can be maintained at appropriate temperatures when the molten injection material is injected into the cavity and can be rapidly cooled after the injection is completed. In addition, the cavity mold includes a hollow guide cylinder, one end of which is fixed through the intermediate cavity core mold plate and the other end of which is fitted into the second guide hole of the cavity mold support plate, so that the intermediate cavity mold plate moves only in the front-rear direction; and a second spring installed between the intermediate cavity mold plate and the cavity mold support plate to separate the intermediate cavity mold plate and the cavity mold support plate from each other by an elastic force when the core mold moves backward to open the cavity. A second heating means for heating the intermediate cavity mold plate is mounted to the parting surface of the intermediate cavity mold plate and provides a second cooling means for cooling the cavity mold support plate.

If the cavity mold is divided into the intermediate cavity mold plate and the cavity mold support plate in the same manner as the core mold according to the present invention, the intermediate cavity mold plate is heated by the heating means to a temperature suitable for injection molding before the plates are coupled to each other, and the cavity mold support plate is cooled to a state in which the intermediate cavity mold plate can be rapidly cooled when it comes into contact with the intermediate cavity mold plate. That is, the core mold support plate is moved toward the cavity mold, and injection of the molten material into the cavity is completed while the intermediate core mold plate, the intermediate cavity mold plate, and the cavity mold support plate are brought into close contact with the cavity mold and all cavity surfaces are maintained at a temperature suitable for injection molding by stopping the action of the first and second heating means. After the molten material is completely injected, the entire cavity can be rapidly cooled. Thus, the temperatures of the core and cavity surfaces are properly maintained, thereby ensuring excellent flow and transfer characteristics of the molten injection material when injected. Further, since the molding device can be rapidly cooled while the injection of the molten material is completed, the cycle time of the injection molding can be further shortened.

In order to enhance the cooling effect of the intermediate cavity mold plate, the parting surfaces of the intermediate cavity mold plate and the cavity mold support plate are preferably in close contact with each other. That is, it is preferable to use a coil spring as the second spring into which the hollow guide cylinder is inserted, and a large-diameter portion having a predetermined depth is formed in the second guide hole of the cavity mold support plate so that the second spring is completely inserted therein when the intermediate cavity mold plate moves backward. Further, the hollow interior of the guide cylinder is used as a first guide hole into which the guide pin can be inserted when the core mold moves toward the cavity mold. In this case, the structure of the molding apparatus can be effectively simplified.

An electric heater capable of easily adjusting heat is used as the first and second heating means. In particular, the first and second heating means are installed in the grooves formed on the parting surfaces of the mold plates such that they are in contact with the intermediate core mold plate and the intermediate cavity mold plate, thereby directly and efficiently transferring heat generated from the heating means. Further, in order to facilitate heat transfer by increasing a contact area between the intermediate core mold plate and the core mold support plate, it is preferable that a copper material is filled in a space between the electric heater and the groove into which the electric heater is inserted. In addition, a temperature sensor may be mounted to the intermediate core mold plate to control the amount of heat generated by the electric heater, so that the core mold can be maintained within a certain temperature range. The first and second cooling means include coolant pipes inserted into the core mold support plate so that a coolant can flow therein. Further, a single heating wire may be used in the electric heater, but it is preferable to use a plurality of heating wires to control the temperature of the cavity or the core surface according to the region thereon and then independently adjust the heat. If the temperature control is performed at various regions on the mold surface, the cooling rate of the injection-molded product can be controlled to prevent deformation due to residual stress, so that a high-quality product can be produced. Alternatively, the cooling rate may be increased to shorten the cycle time and thereby increase productivity.

Drawings

FIG. 1 is a schematic view illustrating a molding apparatus according to one embodiment of the present invention in an open state;

FIG. 2 is a schematic view illustrating the molding apparatus of FIG. 1 in a closed state;

FIG. 3 is a detailed view illustrating an electric heater of an intermediate core mold plate used in the molding apparatus of FIG. 1;

fig. 4(a) and (b) are schematic views illustrating an example of an electric heater used for an intermediate core mold plate in the molding device of fig. 1;

FIG. 5 is a schematic view illustrating a molding apparatus of another embodiment of the present invention in an open state;

fig. 6 is a schematic view illustrating the molding apparatus of fig. 5 in a closed state.

[ detailed description of the reference numerals ]

10: cavity mold fixing plate 20: fixed cavity die

30: the intermediate core mold plate 33: electric heater

35: the core mold bushing 40: core mould supporting plate

41: guide pin 43: cooling pipe

50: core mold fixing plate 60: intermediate cavity die

70: cavity mold support plate 80: temperature sensor

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a schematic view illustrating a molding apparatus according to one embodiment of the present invention in an open state, fig. 2 is a schematic view illustrating the molding apparatus of fig. 1 in a closed state, fig. 3 is a detailed view illustrating electric heaters of an intermediate core mold plate used in the molding apparatus of fig. 1, and fig. 4(a) and (b) are schematic views illustrating examples of the electric heaters of the intermediate core mold plate used in the molding apparatus of fig. 1.

As shown in fig. 1, the molding apparatus 100 of this embodiment includes a cavity mold 20 fixed to an injection molding machine (not shown), an intermediate core mold plate 30 installed to be guided by guide pins 41 and to slide toward or away from the cavity mold 20, and a core mold support plate 40 fixed to a core mold fixing plate 50 movably installed on the injection molding machine. Further, the guide pins 41 fitted into the bushes 35 of the intermediate core mold plate 30 are fixed to the core mold support plate 40. The cavity mold 20 is formed to have a cavity surface 21 into which a molten injection material is injected, the molten injection material being injected into the cavity surface 21 through an injection passage 23. Further, the cavity mold 20 is formed to have guide holes 22 into which the guide pins 41 are inserted. The core surface 31 is formed on the facing surface of the intermediate core mold plate 30On the side of the cavity surface 21. Referring to fig. 2 illustrating the cavity mold 20 and the intermediate core mold plate 30 in a coupled and mutually engaged state, the core surface 31 and the cavity surface 21 define a cavity into which the molten injection material is injectedC. The intermediate core mold plate 30 is formed as a plate thinner than the core mold support plate 40 so that the mold can be easily heated and cooled. In other words, the conventional core mold may be divided into the intermediate core mold plate 30 and the core mold support plate 40.

Referring to fig. 1 and 2, a plurality of grooves 35 are formed on a parting surface of the intermediate core mold plate 30, and electric heaters 33 for heating the intermediate core mold plate 30 are inserted into the grooves 35. Referring to fig. 3, each electric heater 33 is configured in such a manner that an insulating coating 33b surrounds a heating wire 33a such as a nichrome wire. Further, in order to increase a contact area between the intermediate core mold plate 30 and the core mold support plate 40 and also to facilitate heat transfer, a copper material 36 is filled in a space between the electric heater 33 and the groove 35 into which the electric heater 33 is inserted. Referring to fig. 4, a single heating wire (fig. 4(a)) or a plurality of heating wires (fig. 4(b)) may be used as the electric heater 33. Reference numeral 34 denotes a controller for adjusting the amount of heat from the electric heater 33. When a plurality of heating wires are used, the total amount of heat from the electric heaters 33 can be appropriately adjusted so that the temperature of the core surface 31 of the intermediate core mold plate 30 can be equalized. Further, a temperature sensor 80 is mounted to the intermediate core mold plate 30. The temperature sensor 80 is used to measure the temperature of the intermediate core mold plate 30 in real time so that the controller 34 can appropriately adjust the amount of heat from the electric heater to maintain the core mold plate within a certain temperature range. Although the use of a single temperature sensor is illustrated in this embodiment, a plurality of temperature sensors may be installed and used if necessary. In particular, if the heat of the respective electric heaters is to be controlled so that the respective regions on the mold surface have different temperatures from each other, it is preferable to mount the temperature sensors on desired regions on the core surface where the different temperatures are set.

In addition, a cooling means is mounted to the core mold support plate 40 to maintain the core mold support plate 40 at a temperature such that the intermediate core mold plate 30 can be cooled when the core mold support plate 40 and the intermediate core mold plate 30 are in contact. In this embodiment, the cooling means includes a coolant tank (not shown), a pump for circulating a coolant, and a coolant pipe 43 formed in the core mold support plate 40. The coolant pipe 43 is communicated in the core mold support plate 40, and an inlet and an outlet (not shown) are formed on the side of the core mold support plate 40.

Further, a coil spring 90 is inserted around the guide pin 41 between the intermediate core mold plate 30 and the core mold support plate 40. When the core mold support plate 40 moves backward to open the cavity, the coil spring 90 separates the intermediate core mold plate 30 and the core mold support plate 40 from each other by its elastic force, so that the intermediate core mold plate 30 can be rapidly heated by the electric heater 33 without being cooled by the core mold support plate 40. In particular, as shown in FIG. 2, the molten material is injected into a cavity formed by the intermediate core mold plate 30 being in close contact with the cavity mold 20CAfter that, the parting surfaces of the intermediate core mold plate 30 and the core mold support plate 40 are brought into close contact with each other better, thereby enhancing the cooling effect of the intermediate core mold plate 30. Thus, each coil spring is used as the first spring 90 and inserted around the guide pin 41. As shown in fig. 2, when the core mold support plate 40 is moved to contact the intermediate core mold plate 30, the coil springs 90 are completely inserted into the circular holes 44 having a constant depth formed in the edge region of the core mold support plate to which the guide pins 41 are fixed.

The operation and advantageous effects of this embodiment will be described below. A method of manufacturing an injection molded product using the molding apparatus according to this embodiment is explained as follows. First, in a state where the molding apparatus 100 of this embodiment of fig. 1 is mounted on an injection molding machine, electric current is supplied to electric heaters to heat the intermediate core mold plate 30 to a temperature suitable for injection molding. At the same time, the coolant flows into the coolant pipe 43 of the core mold support plate 40 so that the core mold support plate 40 can be maintained at a predetermined temperature required for effective cooling of the core mold support plate. If the intermediate core mold plate 30 and the core mold support plate 40 reach a predetermined temperature suitable for injection molding and cooling, the core mold fixing plate 50 is moved in a leftward direction (toward the cavity mold) as viewed in the drawing, so that the cavity mold 20, the intermediate core mold plate 30, and the core mold support plate 40 are brought into close contact with each other. Then, a molten injection material is injected into the mold2 defined by the chamberCDuring or upon completion of the injection procedure, the electrical power to the electrical heater is turned off. If the injection process is completed and the injection material is completely solidified, the core mold fixing plate 50 is moved backward (rightward as viewed in the drawing) so that the guide pins 41 are removed from the guide holes 22. At this time, the intermediate core mold plate 30 is separated from the core mold support plate 40 due to the restoring force of the coil springs 90, thereby preventing the intermediate core mold plate from being cooled by the core mold support plate, and at the same time, electric power is supplied to the electric heaters 33 to heat the intermediate core mold plate 30. Slave cavity for injection molded productCRemoved and the previous process repeated for injection molding.

If the molding device of this embodiment is used, the intermediate core mold plate 30 is heated by a heating device before joining to keep the plate at a temperature suitable for injection molding, and the core mold support plate 40 is cooled so that it can rapidly cool the intermediate core mold plate when it comes into contact with the intermediate core mold plate. After the plates are joined, an injection molding step is performed, and the intermediate core mold plate 30 is rapidly cooled by the core mold support plate 40. Thus, the core mold surface can be maintained at an appropriate temperature to ensure excellent flow and transfer characteristics when the molten injection material is injected, and the molding device can be rapidly cooled while the material injection is completed, so that the cycle time of the injection molding can be shortened. In particular, in the case where the heating means is configured such that a plurality of electric heaters can be independently controlled, respective regions on the mold surface may have different temperatures to prevent the injection-molded product from being deformed due to residual stress when the injection-molded product is cooled, so that a high-quality injection-molded product can be produced, and the cooling rate can also be controlled to further shorten the cycle time.

Fig. 5 is a schematic view illustrating a molding apparatus according to another embodiment of the present invention in an open state, and fig. 6 is a schematic view illustrating the molding apparatus of fig. 5 in a closed state.

The molding apparatus of fig. 5 is different from that of fig. 1 in that the cavity mold 20 is also divided into an intermediate cavity mold plate 60 and a cavity mold support plate 70 in the same manner as the core mold, electric heaters are also installed on the parting surface of the intermediate cavity mold plate 60, and cooling pipes are also formed in the cavity mold support plate 70. Further, the molding apparatus of this embodiment includes hollow guide cylinders 92, each of which has one end fixed through the intermediate cavity mold plate 60 and the other end installed in a second guide hole 71 formed in the cavity mold support plate 70, so that the intermediate cavity mold plate 60 can move in a direction associated with the cavity mold support plate 70. Further, as shown in fig. 5, coil springs 91 are inserted into the guide cylinders 92 so that the intermediate cavity mold plate 60 can be separated from the cavity mold support plate 70 when the intermediate cavity mold plate 60 and the intermediate core mold plate 30 are in an opened state. Referring to fig. 6, in order to bring the intermediate cavity mold plate 60 and the cavity mold support plate 70 into close contact with each other, the large-diameter portion 74 is formed to be connected to the second guide hole 71 into which the guide cylinder 92 is inserted, so that the second spring 91 is completely inserted into the guide cylinder 92 in the same manner as the circular hole 44 is formed at the fixing of the guide pin 41 on the core mold support plate 40 so that the core mold support plate 40 can be brought into close contact with the intermediate core mold plate 30. Although the knock-up pin for removing the injection-molded product from the molding apparatus is not illustrated in this embodiment, the knock-up pin should be installed to release the product molded by the intermediate cavity mold or the core mold plate from the molding apparatus when the product cannot be automatically released from the molding apparatus.

The method of using the molding apparatus of this embodiment is the same as the previous embodiment except that the intermediate cavity mold plate 60 should be heated to a predetermined temperature suitable for injection molding and the cavity mold support plate 70 should be pre-cooled to a predetermined temperature suitable for cooling the material injected into the cavity mold before the injection molding step.

The molding apparatus of this embodiment is configured such that the cavity mold is divided into the intermediate cavity mold plate and the cavity mold support plate in the same manner as the core mold. Thus, before the joining, the intermediate cavity mold plate is heated by the heating means to a temperature suitable for the injection molding, and the cavity mold support plate is cooled and maintained in a state in which the intermediate cavity mold plate can be rapidly cooled when being brought into contact with the intermediate cavity mold plate. Thus, when the molten injection material is injected, the cavity surface and the core surface are maintained at a temperature suitable for injection molding to ensure excellent flow and transfer characteristics. Further, since the molding apparatus can be rapidly cooled when the material is completely injected, the cycle time of injection molding can be shortened. In particular, since the electric heaters are mounted to the intermediate cavity mold plate and the intermediate core mold plate, the cycle time can be further shortened when the cooling rate is controlled by setting the temperatures of the mold plates to be different from each other.

Industrial applications

According to the present invention, there is provided a molding apparatus including independent intermediate core and cavity mold plates. The separate intermediate core mold plate and cavity mold plate are heated to a proper temperature using a heater before injection molding and are rapidly cooled by the previously cooled and separated core mold support plate and cavity mold support plate, so that the molding apparatus has excellent flow and transfer characteristics and excellent productivity due to the shortened injection molding cycle. In particular, since a plurality of heaters may be used to maintain respective regions of the mold surface at different temperatures, the cooling rate of the product may be controlled, thereby preventing the product from being deformed due to residual stress. Further, since the cycle time can be further shortened, a molding apparatus having excellent productivity can be obtained.

The embodiments in the drawings described and illustrated above should not be construed as limiting the technical spirit of the present invention. The scope of the present invention is defined only by the appended claims, and various changes and modifications within the spirit and scope of the present invention may be made by those skilled in the art. Thus, if it is apparent to those skilled in the art, such changes and modifications are to be included within the scope of the present invention.

Claims (8)

1. A molding apparatus comprising a cavity mold fixed to an injection molding machine and formed to have a cavity surface for defining a cavity into which a molten injection material is injected, and a core mold formed to have a core surface for engaging with the cavity mold to define the cavity and mounted to the injection molding machine so that the core mold can be moved forward and backward to open or close the cavity by being guided by guide pins,

wherein the core mold is divided into a thinner intermediate core mold plate having a core surface and a thicker core mold support plate, and the core mold includes a guide pin protruding from the core mold support plate when moving toward the cavity mold, inserted into a first guide hole formed in the cavity mold and installed through the intermediate core mold plate such that the intermediate core mold plate moves only in a front-rear direction, and a first spring installed between the intermediate core mold plate and the core mold support plate such that the intermediate core mold plate and the core mold support plate are separated from each other by an elastic force when the core mold moves backward to open the cavity; and also

The molding device includes a first heating device mounted to a parting surface of the intermediate core mold plate to heat the intermediate core mold plate, and a first cooling device for cooling the core mold support plate.

2. The apparatus according to claim 1, wherein the intermediate core mold plate is installed to be guided by guide pins and to slide toward or away from the cavity mold, and the core mold support plate is fixed to a core mold fixing plate movably installed on the injection molding machine.

3. The apparatus of claim 1, wherein the cavity mold includes an injection channel through which molten injection material is injected.

4. The apparatus as claimed in claim 1, wherein the first heating means comprises an electric heater inserted into a groove formed on a parting surface of the intermediate core mold plate.

5. The device as claimed in claim 4, wherein the device further comprises a copper material filled in a space between the electric heater and the recess into which the electric heater is inserted to facilitate heat transfer.

6. The device of claim 1, wherein the mandrel support plate has a cooling device mounted thereon, the cooling device comprising a coolant tube formed therein.

7. The apparatus of claim 1, wherein the cavity mold is divided into a thinner intermediate cavity mold plate formed to have a cavity surface and a thicker core mold support plate formed to have a second guide hole,

the cavity mold includes a hollow guide cylinder having one end fixed through the intermediate core mold plate and the other end fitted into a second guide hole of the cavity mold support plate so that the intermediate cavity mold plate moves only in the front-rear direction, and a second spring installed between the intermediate cavity mold plate and the cavity mold support plate to separate the intermediate cavity mold plate and the cavity mold support plate from each other by an elastic force when the core mold moves backward to open the cavity; and also

The molding device includes a second heating device mounted to a parting surface of the intermediate cavity mold plate to heat the intermediate cavity mold plate and a second cooling device for cooling the cavity mold support plate.

8. A method of injection molding, the method comprising:

providing a molding apparatus, the molding apparatus comprising: a cavity mold fixed to the injection molding machine and formed to have a cavity surface for defining a cavity into which the molten injection material is injected, and a core mold formed to have a core surface for engaging with the cavity mold to define the cavity and mounted to the injection molding machine so that the core mold can be moved forward and backward by the guide pin to open or close the cavity,

wherein the core mold is divided into a thinner intermediate core mold plate having a core surface and a thicker core mold support plate, and the core mold includes a guide pin protruding from the core mold support plate when moving toward the cavity mold, inserted into a first guide hole formed in the cavity mold and installed through the intermediate core mold plate such that the intermediate core mold plate moves only in a front-rear direction, and a first spring installed between the intermediate core mold plate and the core mold support plate such that the intermediate core mold plate and the core mold support plate are separated from each other by an elastic force when the core mold moves backward to open the cavity; and also

The molding device includes a first heating device mounted to a parting surface of the intermediate core mold plate to heat the intermediate core mold plate, and a first cooling device for cooling the core mold support plate;

wherein:

first, in a state where the molding apparatus is mounted on an injection molding machine, a current is supplied to a first heating means to heat an intermediate core mold plate to a temperature suitable for injection molding, and at the same time, a coolant flows into a core mold support plate;

when the intermediate core mold plate and the core mold support plate reach predetermined temperatures suitable for injection molding and cooling, the core mold fixing plate to which the core mold support plate is fixed moves toward the cavity mold, so that the cavity mold, the intermediate core mold plate, and the core mold support plate are in close contact with each other;

then, the molten injection material is injected into the mold cavity, and the power of the first heating means is turned off during the injection process or when the injection process is completed;

when the injection process is completed and the injection material is completely solidified, the core mold fixing plate moves away from the intermediate core mold plate such that the guide pin is removed from the guide hole, and at this time, the intermediate core mold plate is separated from the core mold support plate due to the restoring force of the first spring, and at the same time, the first heating means is supplied with power to heat the intermediate core mold plate;

the injection molded product is removed from the mold cavity.