JP2008110583A - Injection molding machine and injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding machine which can efficiently heat and cool a mold near a cavity, and can significantly cut cooling time after an injection process while enhancing the transferability and fluidity of a resin, and an injection molding method which uses the injection molding machine. <P>SOLUTION: The injection molding machine 1 comprises a mold 2 with a cavity 3, mold temperature measuring means 4 and 5, a solenoid induction heating means which heats the mold 2 under solenoid inductive action by energizing a high frequency induction coil 6, a water-cooling means which cools the mold 2 by circulating cooling water W through a circulating water passage 8, a water draining means which forces out the cooling water W by supplying compressed air A to the circulating water passage 8, and a control circuit 15 which controls a heater drive circuit 7, valves 11 to 14, etc. In addition, the coil 6 and the circulating water passage 8 are arranged near the cavity 3 of the mold 2. When the mold 2 is heated by the solenoid induction heating means, the operation is controlled so as to make the circulating water passage 8 a cavity state from which the cooling water W is discharged. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an injection molding apparatus capable of heating and cooling a mold in accordance with a molding process, and an injection molding method performed using such an apparatus.

  In the injection molding method in which a molten thermoplastic resin is injected into a mold cavity to produce a molded product, the temperature of the mold can be controlled when the finished appearance quality is important. is there. In other words, if the mold is heated and the temperature near the cavity is set to be equal to or higher than the thermal deformation temperature of the molding resin, the resin transferability and fluidity will be improved during the injection process, improving the appearance quality of the molded product. Thus, deformation due to residual stress can be suppressed, and coating can be omitted because a filler such as glass filler does not float on the outer surface. However, when the injection process is performed with the mold heated, the cooling time after the injection process required until the molded product is released becomes longer, which necessitates an increase in cost due to a decrease in productivity. End up. Therefore, conventionally, a cooling cycle molding method in which the vicinity of the mold cavity is heated and maintained at the required temperature, and the cooling process is shortened by circulating cooling water around the cavity after the injection process. Is widely adopted (see, for example, Patent Document 1).

As a means for heating the mold, for example, when steam heating is performed by a boiler, the mold temperature can be increased in a short time, but expensive equipment is required and the cost is increased. For this reason, recently, electromagnetic induction heating means for heating a metal mold made of an iron-based metal by electromagnetic induction by energizing a high frequency induction coil (IH coil) disposed in the mold is becoming widespread. That is, in the case of electromagnetic induction heating means, although expensive equipment is unnecessary, the mold temperature can be raised in a short time as steam heating, and control is easy, so that it is disclosed in Patent Document 1 etc. In the conventional injection molding apparatus, a high frequency induction coil is embedded in the vicinity of the cavity in the mold.
JP 2000-127175 A (page 3-4, FIG. 1)

  By the way, in a known injection molding apparatus in which a high-frequency induction coil is embedded in a mold, the high-frequency induction coil is usually arranged close to the cavity in order to raise the mold temperature near the cavity in a short time. The circulation channel for circulating the cooling water is disposed at a location slightly away from the cavity. In other words, even if cooling water is circulated through the circulation channel, it is difficult to quickly lower the mold temperature in the vicinity of the cavity. Therefore, the prior art has the effect of shortening the cooling time after the injection process. There was a problem that it could not be obtained sufficiently.

  If the circulation channel is arranged close to the cavity, the effect of lowering the mold temperature near the cavity is enhanced, but in that case, the water in the circulation channel absorbs a large amount of heat during the heating process in which the high-frequency induction coil is energized. Therefore, it is difficult to raise the mold temperature near the cavity in a short time.

  The present invention has been made in view of the situation of the prior art as described above. The first object of the present invention is to efficiently heat and cool the mold in the vicinity of the cavity, thereby improving the transferability and fluidity of the resin. An object of the present invention is to provide an injection molding apparatus that can significantly reduce the cooling time after the injection process. The second object of the present invention is to provide an injection molding method that exhibits the same effect.

  In order to achieve the first object, in the injection molding apparatus of the present invention, a mold in which a molten thermoplastic resin is injected into the cavity and a high-frequency induction coil disposed in the mold are provided. Electromagnetic induction heating means for heating the mold by electromagnetic induction when energized, water cooling means for cooling the mold by circulating cooling water in a circulation water channel disposed in the mold, and the circulation water channel A drainage means for forcibly discharging the cooling water in the circulation channel by supplying compressed air, and a control means for controlling the electromagnetic induction heating means, the water cooling means and the drainage means, At least a portion is disposed in the vicinity of the cavity with an interval smaller than the interval between the high frequency induction coil and the cavity, and the heating is performed when the mold is heated by the electromagnetic induction heating means. Means has to control as a discharged cavities state of the coolant through the circulation water passage.

  The injection molding apparatus configured in this manner has a circulating water channel in the vicinity of the mold cavity, and thus the mold temperature in the vicinity of the cavity is lowered in a short time by circulating cooling water through the circulating water channel. be able to. Further, since the circulating water channel is in a hollow state when the metal mold is heated by energizing the high frequency induction coil, there is no possibility that the temperature rise of the mold is suppressed by the heat capacity of the water in the circulating water channel. During the heating process, the mold temperature in the vicinity of the cavity can be quickly raised to a required temperature. In other words, since this injection molding apparatus can efficiently raise the temperature of the mold near the cavity, it is easy to improve the transferability and fluidity of the resin during the injection process, and the cooling time after the injection process Therefore, productivity can be improved and manufacturing cost can be reduced.

  In order to achieve the second object described above, in the injection molding method of the present invention, an electromagnetic induction effect is applied to the mold by energizing a high-frequency induction coil disposed in the vicinity of the cavity of the mold. A heating step of heating at a predetermined temperature, an injection step of injecting a molten thermoplastic resin into the cavity while keeping the vicinity of the cavity of the mold at a required temperature, and a vicinity of the cavity of the mold after the injection step. A cooling step of cooling the mold by circulating cooling water through a circulating water channel provided, and after the cooling step, compressed air is supplied to the circulating water channel to forcibly cool the cooling water in the circulating water channel A draining step for discharging, and at the time of the heating step, the circulating water channel is in a hollow state where the cooling water is discharged.

  When the circulating water channel is arranged in the vicinity of the mold cavity as described above, the mold temperature in the vicinity of the cavity can be lowered in a short time by circulating the cooling water through the circulating water channel during the cooling process. Further, since the circulating water channel is in a hollow state during the heating process in which the high-frequency induction coil is energized to heat the mold, there is no possibility that the temperature rise of the mold is suppressed by the heat capacity of the water in the circulating water channel. Therefore, the mold temperature in the vicinity of the cavity can be quickly raised to a required temperature. In other words, if injection molding is performed using a technique that includes a water draining process and the circulation water channel is previously hollowed during the heating process, the cooling efficiency may be adversely affected even if the cooling water channel is disposed near the cavity. Therefore, it becomes easy to improve the transferability and fluidity of the resin during the injection process, and the cooling time after the injection process can be greatly shortened, so that the cost can be reduced along with the improvement in productivity.

  According to the injection molding apparatus of the present invention, since the circulation water channel is disposed in the vicinity of the mold cavity, the mold temperature in the vicinity of the cavity can be lowered in a short time by circulating the cooling water in the circulation water channel. Therefore, the cooling time after the injection process can be greatly shortened, and the cost can be reduced along with the improvement of productivity. Further, in this injection molding apparatus, when the metal mold is heated by energizing the high-frequency induction coil, the circulation water channel is in a hollow state, so that the temperature rise of the mold is suppressed by the heat capacity of the water in the circulation water channel. Therefore, the mold temperature in the vicinity of the cavity can be quickly raised to a required temperature during the heating process, and the transferability and fluidity of the resin can be easily improved during the injection process.

  In addition, according to the injection molding method of the present invention, since the water circulation step can be included and the inside of the circulation water channel can be made hollow during the heating step, the heating efficiency can be improved even if the circulation water channel for cooling is arranged near the cavity. There is no risk of adverse effects. Therefore, it is easy to improve the transferability and fluidity of the resin during the injection process, and the cooling time after the injection process can be greatly shortened, thereby reducing the cost associated with the improvement in productivity.

  FIG. 1 is a block diagram of an injection molding apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic view of a main part of a mold provided in the injection molding apparatus. FIG. 3 is a flowchart showing a flow of steps of an injection molding method performed using the injection molding apparatus.

  An injection molding apparatus 1 shown in FIG. 1 includes a mold 2 having a cavity 3 (see FIG. 2), a thermocouple 4 and a temperature measuring circuit 5 as mold temperature measuring means, and a high-frequency induction coil as electromagnetic induction heating means. (IH coil) 6 and heater drive circuit 7, circulating water path 8 and water temperature adjuster 9 that are water cooling means, and compressor 10 that is a draining means for supplying compressed air A to circulating water path 8 and discharging cooling water W And valves 11 and 12 for opening and closing the flow path of the cooling water W between the water temperature adjuster 9 and the circulation water path 8, and a valve 13 for opening and closing the flow path of the compressed air A and the cooling water W between the compressor 10 and the circulation water path 8. , 14 and a control circuit 15 having an operation unit (not shown) and controlling the heater drive circuit 7, valves 11-14, and the like. The temperature measurement circuit 5, the heater drive circuit 7, the valves 11 to 14, the control circuit 15 and the like are all disposed in the controller 20.

  As shown in FIG. 2, the mold 2 has a fixed mold 2a and a movable mold 2b, and the cavity 3 is defined by clamping the fixed mold 2a and the movable mold 2b. The cavity 3 is provided with a gate (not shown) through which molten thermoplastic resin is injected into the cavity 3. A circulation water channel 8 is embedded in the mold 2 in the vicinity of the cavity 3, and the mold 2 can be cooled by circulating the cooling water W through the circulation water channel 8. In addition, a high frequency induction coil 6 is disposed in the mold 2 relatively near the cavity 3, and the metal mold 2 made of iron-based metal is heated by electromagnetic induction by energizing the high frequency induction coil 6. be able to. However, most of the circulating water channel 8 disposed in the mold 2 is disposed in the vicinity of the cavity 3 with an interval smaller than the interval between the high frequency induction coil 6 and the cavity 3. The temperature in the vicinity of the cavity 3 of the mold 2 is measured by the thermocouple 4 and the temperature measuring circuit 5 and is output to the control circuit 15.

  Next, an injection molding method performed using the injection molding apparatus 1 will be described with reference to the flowchart of FIG. First, after the mold 2 is clamped (step S1), the control circuit 15 that has received the mold clamping signal controls the heater drive circuit 7 to start energization of the high-frequency induction coil 6 (step S2). Thereby, since an eddy current is generated around the cavity 3 of the mold 2, the temperature of the mold 2 rises due to Joule heat. However, in this heating process, the circulating water channel 8 is in a hollow state (the cooling water W is generated). This is done when it is being discharged). In this heating process, the temperature in the vicinity of the cavity 3 of the mold 2 is measured by the thermocouple 4 and the temperature measuring circuit 5, and the temperature information is sent to the control circuit 15.

  When the temperature in the vicinity of the cavity 3 of the mold 2 reaches a set temperature equal to or higher than the thermal deformation temperature of the molding resin, the control circuit 15 that detects this via the temperature measurement circuit 5 switches to the heat retention mode (step) S3). Thereby, the control circuit 15 controls the heater driving circuit 7 so that the vicinity of the cavity 3 of the mold 2 is maintained at the set temperature. After switching to the heat retention mode in this way, a molten thermoplastic resin is injected into the cavity 3 of the mold 2 (step S4).

  After the injection process is completed, the water temperature adjuster 9 is driven to circulate the cooling water W in the circulation water path 8, thereby starting cooling the vicinity of the cavity 3 of the mold 2 (step S5). During the cooling process, the valves 11 and 12 are kept open by the control circuit 15, but the valves 13 and 14 are kept closed. Then, when the temperature in the vicinity of the cavity 3 of the mold 2 is sufficiently lowered, water is drained to forcibly discharge the cooling water W in the circulating water channel 8 (step S6). In such a water draining process, first, the control circuit 15 closes the valves 11 and 12 and opens the valves 13 and 14, and then the compressor 10 supplies the compressed air A to the circulating water channel 8 and forcibly supplies the cooling water W from the circulating water channel 8. To discharge.

  After completion of the water draining process, the movable mold 2b is separated from the fixed mold 2a and the mold 2 is opened (step S7), and then the molded product is released from the cavity 3 by ejecting an unillustrated eject pin (step S7). S8). Since the manufacturing process of one cycle is completed in this way, the circulating water channel 8 is in a hollow state when the mold 2 is clamped at the start stage of the next cycle.

  As described above, in the injection molding apparatus 1 according to the present embodiment, the circulating water channel 8 is disposed in the vicinity of the cavity 3 of the mold 2. The mold temperature can be lowered in a short time, and therefore the cooling time after the injection process can be greatly shortened. Further, in this injection molding apparatus 1, since the circulation water channel 8 is in a hollow state when the high frequency induction coil 6 is energized to heat the mold 2, the heat capacity of the water in the circulation water channel 8 causes the mold 2. There is no possibility that the temperature rise is suppressed, and therefore the mold temperature in the vicinity of the cavity 3 can be quickly raised to a required temperature during the heating process.

  In other words, if injection molding is performed by a technique including a water draining process and leaving the inside of the circulating water channel 8 to be hollow during the heating process, even if the cooling water channel 8 is disposed in the vicinity of the cavity 3, the heating efficiency is adversely affected. Since there is no risk of this, it becomes easy to improve the transferability and fluidity of the resin during the injection process, and the cooling time after the injection process can be greatly shortened, so that productivity can be improved. Accordingly, it is possible to produce an excellent molded product having a good appearance quality, little deformation due to residual stress, and no filling material such as a glass filler floating on the outer surface at low cost.

  In the above embodiment, the molded product is released after the draining step, but the draining step may be performed after the releasing or the draining step may be performed immediately before the heating step.

It is a block diagram of the injection molding device concerning the example of an embodiment of the present invention. It is explanatory drawing which shows typically the principal part of the metal mold | die with which this injection molding apparatus is equipped. It is a flowchart which shows the flow of the process of the injection molding method performed using this injection molding apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection molding apparatus 2 Mold 3 Cavity 4 Thermocouple (Die temperature measuring means)
5 Temperature measurement circuit (mold temperature measurement means)
6 High-frequency induction coil (electromagnetic induction heating means)
7 Heater drive circuit (electromagnetic induction heating means)
8 Circulating water channel (water cooling means)
9 Water temperature controller (water cooling means)
10 Compressor (Draining means)
11-14 Valve 15 Control circuit (control means)
A Compressed air W Cooling water

Claims (2)

A mold in which a molten thermoplastic resin is injected into the cavity, electromagnetic induction heating means for heating the mold by electromagnetic induction by energizing a high-frequency induction coil disposed in the mold, and the mold A water cooling means for cooling the mold by circulating cooling water through a circulating water channel disposed in the mold, and a drain for forcibly discharging the cooling water in the circulating water channel by supplying compressed air to the circulating water channel Means, and control means for controlling these electromagnetic induction heating means, water cooling means and draining means,
At least a part of the circulating water channel is disposed in the vicinity of the cavity with an interval smaller than the interval between the high-frequency induction coil and the cavity, and the mold is heated by the electromagnetic induction heating means. Sometimes, the control means controls the circulating water channel so as to be in a hollow state where the cooling water is discharged. A heating step of heating the mold by electromagnetic induction by energizing a high-frequency induction coil disposed near the cavity of the mold;
An injection step of injecting a molten thermoplastic resin into the cavity while maintaining the vicinity of the cavity of the mold at a required temperature;
After the injection step, a cooling step of cooling the mold by circulating cooling water through a circulating water channel disposed near the cavity of the mold;
A draining step for supplying compressed air to the circulating water channel after the cooling step to forcibly discharge the cooling water in the circulating water channel;
An injection molding method characterized in that, during the heating step, the circulating water channel is in a hollow state from which cooling water is discharged.

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