Method and apparatus of injection molding using a heat-transfer enhancing layer

The injection molding apparatus includes a cavity mold formed with a cavity surface for defining a cavity in which a molten injection material is injected, a core mold formed with a core surface for defining the cavity upon engagement with the cavity mold and installed to be movable forward and backward to open or close the cavity by guidance of a guide pin, an injection unit for injecting a material into the cavity during an injection process, and an injection controller for controlling a hydraulic cylinder to move the core mold forward or backward and the injection unit to inject the material into the cavity.

BACKGROUND

The present disclosure relates to injection molding, and more particularly, to heating and cooling an injection molding apparatus.

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

SUMMARY

One aspect of the invention provides an apparatus for injection molding, which comprises: a first mold comprising a first cavity surface; and a second mold comprising a heating plate comprising a second cavity surface opposing the first cavity surface, wherein the first and second cavity surfaces in combination are configured to define a molding cavity with or without an additional surface, a cooling plate movable relative to the heating plate between a first position and a second position, wherein in the first position the cooling plate contacts the heating plate, and a heat-transfer enhancing layer integrated with either of the heating plate and the cooling plate so as to be interposed between the heating plate and the cooling plate, wherein the heat-transfer enhancing layer is formed of a material other than that of a portion of the cooling plate or the heating plate with which the heat-transfer enhancing layer is integrated, wherein the heat-transfer enhancing layer is configured to improve a heat-transfer contact between the heating plate and the cooling plate when the cooling plate is in the first position.

In the foregoing apparatus, the heat-transfer enhancing layer may be integrated with the cooling plate, wherein the heat-transfer enhancing layer may comprise a surface facing the heating plate, wherein the surface may contacts the heating plate when the cooling plate is in the first position, while not contacting the heating plate when the cooling plate is in the second position. The heat-transfer enhancing layer may be integrated with the heating plate, wherein the heat-transfer enhancing layer may comprise a surface facing the cooling plate, wherein the surface may contact the cooling plate when the cooling plate is in the first position, while not contacting the cooling plate when the cooling plate is in the second position. The material of the heat-transfer enhancing layer may be softer than that of the material of the portion of the heating plate or the cooling plate. The heat-transfer enhancing layer may comprise at least one metal selected from the group consisting of gold, silver, copper, tin, lead and aluminum. The heat-transfer enhancing layer may comprise a grease layer coated on a surface of the cooling plate. The heat-transfer enhancing layer may comprise a grease layer coated on a surface of the heating plate.

Still in the foregoing apparatus, the heating plate may further comprise an electric heater embedded therein. The first mold may be movable relative to the cooling plate and further movable relative to the heating plate. The first mold may comprise a passage configured to flow a moldable material toward the cavity. The first mold may comprise a second heating plate comprising the first cavity surface, a second cooling plate movable relative to the first heating plate between a third position and a fourth position, wherein in the third position the second cooling plate contacts the second heating plate, and a second heat-transfer enhancing layer integrated with either of the second heating plate and the second cooling plate so as to be interposed between the second heating plate and the second cooling plate, wherein the second heat-transfer enhancing layer is formed of a material other than that of a portion of the second cooling plate or the second heating plate with which the second heat-transfer enhancing layer is integrated, wherein the second heat-transfer enhancing layer is configured to improve a heat-transfer contact between the second heating plate and the second cooling plate when the second cooling plate is in the third position.

Another aspect of the invention provides a method of injection molding, the method comprising: providing an injection molding apparatus comprising a first mold comprising a first cavity surface, a second mold comprising a heating plate and a cooling plate, wherein the heating plate comprises a second cavity surface opposing the first cavity surface, and a heat-transfer enhancing layer integrated with either of the second heating plate and the second cooling plate so as to be interposed between the heating plate and the cooling plate, wherein the heat-transfer enhancing layer is formed of a material other than that of a portion of the cooling plate or the heating plate with which the heat-transfer enhancing layer is integrated; moving the heating plate relative to the first mold so as to form a molding cavity between the first and second cavity surfaces with or without an additional surface; generating heat in the heating plate; injecting a moldable material into the molding cavity; moving the cooling plate relative to the heating plate such that the heat-transfer enhancing layer contacts the other of the heating plate and the cooling plate, thereby improving a heat-transfer contact between the heating plate and the cooling plate; and cooling the cooling plate so as to enhance heat-transfer from the heating plate to the cooling plate.

In the foregoing method, the heat-transfer enhancing layer may be integrated with the cooling plate. The heat-transfer enhancing layer may be integrated with the heating plate. The material of the heat-transfer enhancing layer is softer than that of the material of the portion of the heating plate or the cooling plate. The heat-transfer enhancing layer may comprise at least one metal selected from the group consisting of gold, silver, copper, tin, lead and aluminum. The heat-transfer enhancing layer may comprise a grease layer coated on a surface of the cooling plate. The heat-transfer enhancing layer may comprise a grease layer coated on a surface of the heating plate. The method may further comprise moving the cooling plate away from the heating plate after injecting the moldable material. The heating plate may comprise an electrical heater embedded therein.

One aspect of the present invention is to provide an injection molding apparatus having a heating and cooling means, in which a mold is kept at a suitable temperature to maintain the flowability and transferability of an injected molten material and is then cooled rapidly during and after an injection process to shorten a cycle time for the injection molding, and a controlling method thereof. That is, this aspect of the present invention is to provide an injection molding apparatus and a controlling method thereof capable of solving a conflicting problem in that it takes much time to cool the mold and thus the cycle time for the injection molding is increased when the temperature of the mold is increased, whereas the flowability and transferability may be deteriorated when the size of the mold is reduced to rapidly cool the mold.

Another aspect of the present invention is to provide an injection molding apparatus capable of manufacturing a high quality injection-molded product without deformation and also of reducing a cycle time by allowing each of regions on a mold surface to be maintained at a desired temperature to control a cooling rate of the injection-molded product, and a controlling method thereof.

One aspect of the invention provides an injection molding apparatus, which comprises a cavity mold formed with a cavity surface for defining a cavity in which a molten injection material is injected, a core mold formed with a core surface for defining the cavity upon engagement with the cavity mold and installed to be movable forward and backward to open or close the cavity by guidance of a guide pin, an injection unit for injecting a material into the cavity during an injection process, and an injection controller for controlling a hydraulic cylinder to move the core mold forward or backward and the injection unit to inject the material into the cavity. Further, the core mold is divided into a thinner intermediate core mold plate having the core surface and a thicker core mold support plate, and includes a guide pin extending from the core mold support plate to be inserted into a first guide hole formed in the cavity mold upon movement of the core mold toward the cavity mold and fitted through the intermediate core mold plate to allow the intermediate core mold plate to move only forward and backward, and a first elastic member installed between the intermediate core mold plate and the core mold support plate to allow the intermediate core mold plate and the core mold support plate to be separated from each other by means of elastic force when the core mold moves backward to open the cavity.

In addition, the injection molding apparatus further comprises a first heating means installed to a parting surface of the intermediate core mold plate to heat the intermediate core mold plate, a first cooling means for cooling the core mold support plate, and a mold temperature controller for controlling the first heating and cooling means to control a temperature of the intermediate core mold plate during the injection process. Particularly, since the injection molding apparatus is configured such that the injection controller controls the hydraulic cylinder to allow the core mold to move forward and backward and the mold temperature controller controls the temperature of the intermediate core mold plate, injection molding works are automated. Therefore, the number of workers can be reduced and the productivity can also be improved.

In the injection molding apparatus, the core mold, which serves as a movable mold installed to be movable relative to the cavity mold, is divided into the thinner intermediate core mold plate and the thicker core mold support plate. Further, the intermediate core mold plate is heated by the heating means to be kept at a temperature suitable for the injection molding before engagement with the core mold support plate, and the core mold support plate is cooled enough to rapidly cool the intermediate core mold plate when coming into contact with the intermediate core mold plate. During the injection process, the core mold support plate is moved toward the cavity mold such that the intermediate core mold plate is pressed to come into close contact with the cavity mold, and then, the operation of the heating means is stopped and the intermediate core mold plate contacted with the core mold support plate is rapidly cooled after a molten material has been completely injected. Thus, the core surface is kept at a suitable temperature to ensure excellent flowability and transferability when the molten material is being injected, but the mold can be rapidly cooled immediately after the completion of injection. Thus, a cycle time of the injection molding can be shortened.

The injection molding apparatus further comprises a heat transfer member installed to a surface of the intermediate core mold plate facing the core mold support plate or a surface of the core mold support plate facing the intermediate core mold plate to rapidly cool the heated intermediate core mold plate. Preferably, the heat transfer member is made of soft metal with hardness less than the core mold, and is made of a metal selected from the group consisting of gold, silver, copper, tin, lead and aluminum, or an alloy thereof. More preferably, the heat transfer member contains a heat transfer material having a dissolution temperature of 180° C. or above and is lubricating grease. Therefore, since the heat transfer member is installed between the intermediate core mold plate and the core mold support plate which are separated from each other, the heated intermediate core mold plate can be rapidly cooled. Further, since impact occurring when the intermediate core mold plate and the core mold support plate collide against each other is alleviated, the durability of the injection molding apparatus can be further enhanced.

The injection molding apparatus is configured in such a manner that the first heating means includes an electric heater inserted into a groove formed in the parting surface of the intermediate core mold plate, and the first cooling means includes a coolant pipe installed in the core mold support plate to allow a coolant to flow through the coolant pipe. A copper member filled in a space between the electric heater and the groove to facilitate heat transfer is further provided. Further, the first elastic member is a coil spring through which the guide pin is inserted and a circular hole with a predetermined depth is formed at an outer peripheral region of the core mold support plate, to which the guide pin is fixed, to allow the coil spring to be fully inserted therein when the core mold support plate moves forward. A temperature sensor installed in the intermediate core mold plate to measure the temperature of the intermediate core mold plate is further provided. Furthermore, a plurality of electric heaters each capable of independently controlling its amount of heat are provided.

In the injection molding apparatus, the cavity mold is divided into a thinner intermediate cavity mold plate formed with a cavity surface and a thicker cavity mold support plate formed with a second guide hole. The cavity mold includes a hollow guide cylinder having one end fixed through the intermediate cavity mold plate and the other end fitted into the second guide hole of the cavity mold support plate to allow the intermediate cavity mold plate to move only forward and backward, and a second elastic member installed between the intermediate cavity mold plate and the cavity mold support plate to allow the intermediate cavity mold plate and the cavity mold support plate to be separated from each other by means of elastic force when the core mold moves backward to open the cavity. The injection molding apparatus includes a second heating means installed to a parting surface of the intermediate cavity mold plate to heat the intermediate cavity mold plate and a second cooling means for cooling the cavity mold support plate.

If the cavity mold as well as the core mold is divided into the intermediate cavity mold plate and the cavity mold support plate, the intermediate cavity mold can be heated to be kept at a temperature suitable for injection molding before engagement with the cavity mold support plate and the cavity mold support plate can be cooled enough to rapidly cool the intermediate core mold plate when coming into contact with the intermediate core mold plate. That is, the molten injection molding material is completely injected in a state where the intermediate core mold plate, the intermediate cavity mold plate and the cavity mold support plate are brought into close contact with one another by moving the core mold support plate toward the cavity mold, and also while all the cavity surfaces are kept at a temperature suitable for the injection process by stopping the heating of the first and second heating means. After the injection process has been completed, the whole cavity can be rapidly cooled. Therefore, when the molten material is injected, the cavity and core surfaces are kept at the suitable temperatures to ensure superior flowability and transferability. Further, since the mold can be rapidly cooled just after the injection has been completed, a cycle time of the injection molding process can be shortened.

In addition, in order to enhance a cooling effect of the intermediate cavity mold, it is preferred that the parting surfaces of the cavity mold support plate and the intermediate cavity mold plate be completely brought into close contact with each other during the cooling process. That is, a coil spring is used as the elastic member such that a hollow cylinder can be inserted, and a large-diameter portion with a predetermined depth is preferably formed in the second guide hole of the cavity mold support plate to allow the coil spring to be completely inserted therein when the intermediate cavity mold plate moves backward. In addition, a hollow space of the guide cylinder is used as the first guide hole such that the guide pin can be inserted into the hollow space of the guide cylinder when the core mold moves toward the cavity mold, thereby advantageously simplifying the configuration.

In addition, in the injection molding apparatus, each of the first and second heating means utilizes an electric heater capable of easily controlling an amount of heat. Particularly, the first and second heating means are installed into the grooves formed in the parting surfaces of the molds to effectively transfer the generated heat directly to the intermediate core and cavity mold plates in a state where they are brought into contact with the intermediate mold plates. In addition, in order to promote heat transfer by increasing a contact area between the intermediate core mold plate and the core mold support plate, copper is preferably filled in a space between the groove and the electric heater inserted into the groove.

A temperature sensor may also be installed to the intermediate core mold plate to control an amount of heat of the electric heater such that the temperature of the core mold can be kept within a predetermined range. Each of the first and second cooling means includes a coolant pipe inserted into the core mold support plate such that a coolant can flow through the coolant pipe. In addition, each of the electric heaters may use a single heat wire, but a plurality of electric wires each capable of independently controlling an amount of heat are used to control the temperatures of various regions on the cavity or core surface. If the temperature is independently controlled for every region, a cooling rate of an injection molded product can be controlled and the deformation caused by residual stress can also be reduced such that a high quality molded product can be produced. Further, a cycle time can be shortened due to a fast cooling rate of the mold, and thus, the productivity can be improved.

Another aspect of the present invention provides a method of controlling an injection molding apparatus which includes a cavity mold formed with a cavity surface for defining a cavity in which a molten injection material is injected, a core mold formed with a core surface for defining the cavity upon engagement with the cavity mold and installed to be movable forward and backward to open or close the cavity by guidance of a guide pin, the core mold being divided into an intermediate core mold plate and a core mold support plate, an injection unit for injecting a material into the cavity during an injection process, and an injection controller for controlling a hydraulic cylinder to move the core mold forward or backward and the injection unit to inject the material into the cavity, a first heating means installed to a parting surface of the intermediate core mold plate to heat the intermediate core mold plate, a first cooling means for cooling the core mold support plate, and a mold temperature controller for controlling the first heating and cooling means to control a temperature of the intermediate core mold plate during the injection process.

The method comprises the steps of operating the hydraulic cylinder to allow the core mold to be engaged with the cavity mold; operating the first heating means, simultaneously when the hydraulic cylinder is started, to heat the intermediate core mold plate; stopping the operation of the first heating means to stop heating the intermediate core mold plate when a signal detected from a temperature sensor installed to the intermediate core mold plate reaches a predetermined heating temperature; injecting a molten material from the injection unit into the cavity at the same time when the operation of the first heating means is stopped; bringing the core mold support plate mounted with a coolant pipe into close contact with the intermediate core mold plate to cool the intermediate core mold plate simultaneously when the material starts being injected; separating the intermediate core mold plate and the core mold support plate from each other to stop cooling the intermediate core mold plate when the signal detected from the temperature sensor installed to the intermediate core mold plate reaches the predetermined cooling temperature; and operating the hydraulic cylinder to allow the core mold to be disengaged from the cavity mold.

DETAILED DESCRIPTION OF EMBODIMENTS

In the injection molding, it is preferred that the mold have the same temperature as the molten material, if possible, when the molten material is injected. The reason is that the flowability of the injected material and the transferability of a pattern onto a cavity surface can be improved and the deformation caused by residual stress after the molten material is hardened can also be reduced. Further, it is preferred that the mold have a lower temperature after the molten material has been completely injected so that the injected material can be rapidly cooled and a cycle time for the injection molding can also be shortened, thereby enhancing its productivity.

However, if the mold is beforehand heated to increase its temperature, the flowability and transferability are enhanced but it takes long time to cool the mold. Thus, a cycle time for the injection molding may be increased. On the other hand, in a case where the volume of the mold is decreased such that the mold can be rapidly cooled to shorten a cycle time for the injection molding, the stiffness or rigidity of the mold may be weakened. Thus, a molded product may be deformed or its durability may be deteriorated.

FIG. 1is a block diagram schematically showing an injection molding apparatus according to an embodiment of the present invention,FIG. 2is a schematic view showing an open state of the molds of the injection molding apparatus according to an embodiment of the present invention,FIG. 3is a schematic view showing a closed state of the molds of the injection molding apparatus according to an embodiment of the present invention,FIG. 4is a detailed view showing an electric heater of an intermediate core mold plate according to an embodiment of the present invention,FIG. 5(a) is a schematic view showing an arrangement of the electric heater of the intermediate core mold plate according to an embodiment of the present invention, andFIG. 5(b) is a schematic view showing another arrangement of the electric heater of the intermediate core mold plate according to an embodiment of the present invention.

The injection molding apparatus of an embodiment of the present invention comprises a cavity mold having a cavity surface, a core mold which is engaged with the cavity mold and is divided into an intermediate core mold plate and a core mold support plate, an injection controller for controlling a hydraulic cylinder which allows the core mold to move forward or backward, a first heating means for heating the intermediate core mold plate, a first cooling means for cooling the core mold support plate, a mold temperature controller for controlling the operation of the first heating and cooling means, and a heat transfer member which is installed on a surface of the core mold support plate facing the intermediate core mold plate.

As shown inFIG. 1, an injection unit is a unit for injecting a material into a cavity, and includes a heating cylinder122, a screw124installed within the heating cylinder122, and a hydraulic motor120for rotating the screw124. In addition, a hydraulic cylinder110is provided to move a core mold fixing plate50. Further, a cavity mold20is fixed to a cavity mold fixing plate10, and a molten material is injected into the cavity through an injecting passage formed in the cavity mold fixing plate10which the heating cylinder122comes into close contact with upon injection of material. The screw124is installed within the heating cylinder122in a longitudinal direction of the heating cylinder122, and the hydraulic motor120which is connected to the screw124to rotate the screw124is installed to one side of the heating cylinder122. In addition, the injection controller310is electrically connected to the hydraulic cylinder110, the hydraulic motor120and the mold temperature controller320. Further, the mold temperature controller320is electrically connected with a valve322for regulating the flow of coolant flowing through a coolant pipe43installed to the core mold support plate30, an electric heater33installed to the intermediate core mold plate30, and a temperature sensor80installed to the intermediate core mold plate30.

Referring toFIG. 2, the cavity mold20is formed with a cavity surface21in which a molten injection material is injected and the molten injection material is injected in the cavity surface21through an injection passage23. In addition, the cavity mold20is formed with guide holes22into which the guide pins41are inserted. A core surface31is formed on a side of the intermediate core mold plate30facing the cavity surface21. Referring toFIG. 3showing a state where the cavity mold20and the intermediate core mold plate30are engaged with each other, the core surface31and the cavity surface21define a cavity C in which the molten injection material is injected. The intermediate core mold plate30is shaped as a plate thinner than the core mold support plate40to allow the core mold to be easily heated and cooled.

Referring toFIG. 4, a plurality of grooves37are formed in a parting surface of the intermediate core mold plate30, and electric heaters33for heating the intermediate core mold plate30are inserted in the grooves37. Here, each of the electric heaters33is configured in such a manner that an insulation coating33bsurrounds a heating wire33asuch as a nichrome wire. Further, in order to increase a contact area between the intermediate core mold plate30and the core mold support plate40and also facilitate heat transfer, a copper member36is filled in a space between the electric heater33and the groove37in which the electric heater33is inserted.

Referring toFIGS. 5(a) and (b), a single heating wire (FIG. 5(a)) or a plurality of heating wires (FIG. 5(b)) may be employed in the electric heater33. Reference numeral34designates a mold temperature controller for adjusting an amount of heat from the electric heater33. In a case where a number of the heating wires are used, an amount of heat from the respective electric heaters33can be suitably adjusted such that the temperature of the core surface31of the intermediate core mold plate30can be uniform. In addition, a temperature sensor80is installed to the intermediate core mold plate30. The temperature sensor80is used to measure the temperature of the intermediate core mold plate30in real time and to transmit the measured temperature such that the mold temperature controller34can suitably adjust the amount of heat from the electric heater to cause the core mold plate to be maintained within a certain range of temperature. Although it has been illustrated in this embodiment that a single temperature sensor is used, a plurality of temperature sensors may be installed, if necessary. Particularly, if the amounts of heat from the respective electric heaters are to be adjusted such that respective regions on the mold surface have different temperatures from one another, it is preferred that the temperature sensors be installed to the desired regions on the core surface where different temperatures are set.

In addition, a first cooling means is installed to the core mold support plate40to keep the core mold support plate40at a certain temperature such that the intermediate core mold plate30can be cooled when the core mold support plate40comes into contact with the intermediate core mold plate30. In this embodiment, the first cooling means includes a coolant tank (not shown), a pump for circulating coolant, and a coolant pipe43formed in the core mold support plate40. The coolant pipe43is connected in the core mold support plate40and inlet and outlet ports (not shown) are formed in sides of the core mold support plate40.

Further, coil springs90are inserted around the guide pins41between the intermediate core mold plate30and the core mold support plate40. When the core mold support plate40moves backward to open the cavity, the coil springs90allow the intermediate core mold plate30and the core mold support plate40to be separated from each other by means of their elastic force such that the intermediate core mold plate30can be rapidly heated by means of the electric heaters33in a state where the intermediate core mold plate30is not further cooled by means of the core mold support plate40. In particular, as shown inFIG. 3, after a molten material has been injected into the cavity C formed by bringing the intermediate core mold plate30into close contact with the cavity mold20, the parting surfaces of the intermediate core mold plate30and the core mold support plate40are preferably brought into close contact with each other to improve the cooling effect of the intermediate core mold plate30. Thus, each of the coil springs90is inserted around the guide pin41. As shown inFIG. 3, when the core mold support plate40is moved to come into contact with the intermediate core mold plate30, the coil springs90are completely inserted into circular holes44each having a constant depth and formed at outer peripheral regions of the core mold support plate to which the guide pins41are fixed.

A heat transfer member94is installed to a surface of the intermediate core mold plate30facing the core mold support plate40in order to rapidly cool the intermediate core mold plate30which has been heated during the injection process. Alternatively, the heat transfer member94may be installed to a surface of the core mold supporting plate40facing the intermediate core mold plate30. Such a heat transfer member94is made of soft metal with hardness less than the core mold, and the soft metal is preferably a metal selected from gold, silver, copper, tin, lead and aluminum, or an alloy thereof. In addition, the heat transfer member94is a gel-state heat transfer material having a dissolution temperature of 180° C. or above. Preferably, the heat transfer material is lubricating grease.

The injection controller310controls the hydraulic cylinder110for moving the core mold forward or backward, and the hydraulic motor120for rotating the screw124. In addition, the mold temperature controller320receives a signal from the temperature sensor80installed to the intermediate core mold plate30and controls the electric heater33serving as the first heating means and the valve322installed to the coolant pipe43serving as the first cooling means, thereby regulating the coolant flow. Of course, the injection controller310and the mold temperature controller320can transmit and receive necessary signals to and from each other.

Hereinafter, an injection molding apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.FIG. 6is a schematic view showing an open state of the molds of an injection molding apparatus according to an embodiment of the present invention, andFIG. 7is a schematic view showing a closed state of the molds of the injection molding apparatus according to an embodiment of the present invention.

This embodiment is different from the previous embodiment in that the cavity mold20is also divided into an intermediate cavity mold plate60and a cavity mold support plate70in the same manner as the core mold, and that electric heaters are installed to a parting surface of the intermediate cavity mold plate60and cooling pipes are formed in the cavity mold support plate70. The molding apparatus of this embodiment further includes hollow guide cylinders92each of which has one end fixed through the intermediate cavity mold plate60and the other end fitted into a second guide hole71formed in the cavity mold support plate70such that the intermediate cavity mold plate60can be moved in one direction with respect to the cavity mold support plate70. In addition, as shown inFIG. 6, coil springs91are inserted into the guide cylinders92such that the intermediate cavity mold plate60can be disengaged from the cavity mold support plate70when the intermediate cavity mold plate60and the intermediate core mold plate30are in an open state. Further, another heat transfer member95is installed to a surface of the intermediate cavity mold plate facing the cavity mold support plate. The heat transfer member95is positioned between the cavity mold support plate and the intermediate cavity mold plate to rapidly cool the heated intermediate cavity mold plate. Alternatively, the heat transfer member may be installed to a surface of the cavity mold support plate facing the intermediate cavity mold plate.

Referring toFIG. 7, large-diameter portions74are formed in series with the second guide holes71in which the guide cylinders92are inserted such that the second springs91are inserted therein to completely bring the intermediate cavity mold plate60and the cavity mold support plate70into close contact with each other, in the same manner as the circular holes44are formed on the core mold support plate40at positions where the guide pins41are fixed such that the core mold support plate40can be brought into close contact with the intermediate core mold plate30. Although an eject pin for removing an injection-molded product from the molding apparatus is not illustrated in this embodiment, an eject pin is installed to eject a product molded through the intermediate cavity or core mold plates from the molding apparatus in a case where the product is not automatically ejected from the molding apparatus.

Hereinafter, a method of controlling the injection molding apparatus according to an embodiment of the invention will be described with reference to the accompanying drawings.FIG. 8is a flowchart illustrating a method of controlling the injection molding apparatus according to an embodiment of the present invention. First, when a signal indicating that the molds are opened is input to the injection controller310, the injection controller310operates the hydraulic cylinder110such that the core mold can be engaged with the cavity mold40. At the same time, the signal is also input to the mold temperature controller320, and the mold temperature controller320operates the electric heater33serving as the first heating means to heat the intermediate core mold plate30.

As the intermediate core mold plate30is heated, a signal detected from the temperature sensor80installed to the intermediate core mold plate30is sent to the mold temperature controller320, which in turn terminates the operation of the electric heater33to stop the heating of the intermediate core mold plate30when the temperature sent to the mold temperature controller320reaches a predetermined heating temperature. Simultaneously, when the operation of the electric heater33is stopped, the hydraulic motor120is operated to allow a molten material in the heating housing122to be injected into the cavity through the injection passage23by means of the screw124.

At the same time, the core mold support plate40mounted with the coolant pipe43is brought into close contact with the intermediate core mold plate30in order to cool the intermediate core mold plate30. Here, the reason that the intermediate core mold plate30is cooled simultaneously when the injection material is injected into the cavity is that the time taken to inject the molten material into the cavity is relatively shorter than the time taken to cool the intermediate core mold plate30.

Then, a signal detected from the temperature sensor80installed to the intermediate core mold plate30is input to the mold temperature controller320, which in turn allows the intermediate core mold plate30to be separated from the core mold support plate40in order to stop the cooling of the intermediate core mold plate30when the temperature input to the mold temperature controller320reaches a predetermined cooling temperature.

If the cooling of the intermediate core mold plate30is stopped, the injection controller310operates the hydraulic cylinder110such that the core mold is disengaged from the cavity mold40. In addition, an ejector pin (not shown) is operated to remove the molded product from the molding apparatus, if desired. According to an embodiment of the present invention, a molding apparatus includes separate intermediate core and cavity mold plates. The separate intermediate core and cavity mold plates are heated to a suitable temperature using the electric heaters before the injection molding and then rapidly cooled by means of the previously cooled separate core and cavity mold support plates. Therefore, an embodiment of the present invention can provide a molding apparatus having excellent flowability and transferability and high productivity due to the shortened cycle time for the injection molding, and a controlling method thereof. In particular, since a plurality of electric heaters are used to allow respective regions on the mold surface to be kept at the different temperatures, a cooling rate of the product can be controlled to prevent the product from being deformed due to the residual stress. Further, since the cycle time for the injection molding can be shortened, a molding apparatus with high productivity and a controlling method thereof can be obtained.

In addition, the injection molding apparatus according to an embodiment of the present invention is configured such that the injection controller controls the hydraulic cylinder for causing the core mold to move forward or backward and the mold temperature controllers control the temperature of the intermediate core mold. Therefore, since the injection molding work is automated, the number of workers can be reduced and the productivity can also be improved.

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