JP2011083953A - Injection molding system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding system simplifying setting of a time to open a shut-off valve to improve productivity without excessively supplying an injection molding machine with a molding material. <P>SOLUTION: The injection molding system includes a molding material supply device 13, a vacuum deaerator 14 and the injection molding machine 15. A first hopper 1 and a second hopper 2 of the molding material supply device 13 are provided with a vacuum gage 16 and a vacuum gage 17. A vacuum comparing device 18 is also provided for comparing the degrees of vacuum measured by the vacuum gages 16, 17. The vacuum comparing device 18 compares a difference between the respective degrees of vacuum, and opens the shut-off valve 3 when the vacuum degree difference is not more than a predetermined value (a value not applying an impact to at least the second hopper 2 when the shut-off valve 3 is opened by the pressure difference). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an injection molding system including a vacuum degassing device capable of efficiently removing moisture and volatile matter generated from a molding material during melting in injection molding.

  In injection molding, moisture and volatile components contained in a molding material such as resin cause various defects such as resin burns and bubbles in the molded product. Therefore, a material drying process is required in which the molding material is preheated at a predetermined temperature before injection to remove moisture and volatile components. Further, it has been necessary to perform molding with a vent type injection molding machine having a built-in screw for injecting a molding material and provided with a deaeration hole in the middle of a heating cylinder capable of dissolving the molding material. In the vent type injection molding machine, moisture and volatile components can be naturally exhausted while the molding material is dissolved in the heating cylinder.

  However, these have increased the time and labor required for preparation for molding, and have been a factor of lowering production efficiency in producing products.

  In order to solve this problem, there is a vacuum degassing device as an accessory device of an injection molding machine that can omit the material drying step. The vacuum deaerator removes moisture and volatile matter generated from the molding material by vacuum suction.

  FIG. 2 is a diagram showing a configuration of a conventional injection molding system including a molding material supply device 13, a vacuum deaeration device 14, and an injection molding machine 15.

  The molding material supply device 13 includes a first hopper 1 into which a pellet-shaped molding material is charged from the outside. In the vertically downward direction of the first hopper 1, a second hopper 2 is provided via a shutoff valve 3. In addition, a feed screw housing 5 that houses a feed screw 4 that feeds a molding material by rotating is provided on the opposite side of the second hopper 2 from where the shutoff valve 3 is provided. Yes. A feed cylinder 6 communicating with the injection molding machine 15 is provided in a vertically downward direction at the delivery destination of the feed screw 4, and the molding material is sent to the injection molding machine 15 so as to fall.

  The injection molding machine 15 includes a heating cylinder 11 provided with a heater 10 for applying heat to the molding material, and an injection that is movable in the heating cylinder 11 along the axial direction of the heating cylinder 11 and is rotatable around the axis of the heating cylinder 11. A screw 12 is provided.

  Further, the supply cylinder 6 is connected to the vacuum pump 7 using the first vacuum pipe 8, and the heating cylinder 11, the supply cylinder 6, the feed screw housing 5 and the second hopper 2 are brought into a vacuum state. It has a structure that can. Therefore, moisture and volatile matter generated from the molding material dissolved in the heating cylinder 11 are sucked from the supply cylinder 6 by the vacuum pump 7. The molding material dissolved in the heating cylinder 11 is freed from moisture and volatile components at the time of injection, and can be molded without causing defects such as resin, burns and bubbles.

  Further, the first hopper 1 is also connected to the vacuum pump 7 by the second vacuum pipe 9. Since the shut-off valve 3 is provided between the first hopper 1 and the second hopper 2, the first hopper 1 and the second hopper 2 can be individually in a vacuum state. . When supplying the molding material from the first hopper 1 to the second hopper 2, the vacuum state of the supply cylinder 6 and the like is maintained by opening the shutoff valve 3 after the first hopper 1 is evacuated. I can do it. Further, when the molding material is charged into the first hopper 1 under atmospheric pressure, the outside air does not flow into the second hopper 2 if the shutoff valve 3 is closed.

  The connecting portion between the supply cylinder 6 and the first vacuum pipe 8 and the connecting portion between the first hopper 1 and the second vacuum pipe 9 are provided with a filter or the like, and the molding material is not sucked into the vacuum pump. It is like that. The second vacuum pipe 9 is provided with a valve 25 that shuts off the first hopper 1 and the vacuum pump 7. When the shutoff valve 3 is closed and the molding material is charged into the first hopper 1 under atmospheric pressure, the suction by the vacuum pump 7 can be stopped by closing the valve 25.

  When the injection molding system as shown in FIG. 2 is used, when the supply amount by the feed screw 4 exceeds a predetermined supply amount, the supply cylinder 6 is closed by the molding material. If the molding material is supplied when the rotation of the injection screw 12 of the injection molding machine 15 is stopped, the gap between the heating cylinder 11 and the injection screw 12 is filled when the injection screw 12 starts to rotate. , Block the path to suck moisture and volatiles.

  Due to these blockages, moisture and volatile components of the molding material are not sucked, and the product is molded in a state where moisture and volatile components remain in the molding material, resulting in defects. Therefore, in Patent Document 1, the supply amount of the molding material to the heating cylinder 11 is controlled by changing the rotation speed of the feed screw 4 to prevent the supply cylinder 6 and the like from being blocked.

  Further, in Patent Document 2, by installing a shielding cylinder smaller than the inner diameter of the supply cylinder 6 inside the supply cylinder 6, the space formed by the supply cylinder 6 and the shielding cylinder is taken as one path, and the inside of the shielding cylinder Are different routes. The molding material delivered by the feed screw 4 falls from the feed screw housing 5 vertically downward. That is, the path formed by the supply cylinder 6 and the shielding cylinder is a molding material supply path, and the shielding cylinder is a suction path for moisture and volatile matter. Therefore, it is possible to prevent the suction path from being blocked by the molding material supplied to the heating cylinder 11.

JP 2006-347051 A JP 2005-1119090 A

  Release of the shutoff valve 3 provided between the first hopper 1 and the second hopper 2 estimates the time until the first hopper 1 is in a vacuum state, and opens the shutoff valve 3. It was done by setting the time. However, if a connection failure such as a vacuum pipe or a filter provided in a connection portion between the first hopper 1 and the vacuum pipe 9 or the like occurs, it is estimated until the first hopper 1 reaches a vacuum state. Requires more time than time. In this case, the shutoff valve 3 may be opened before the first hopper 1 reaches the vacuum state.

  When the shutoff valve 3 is opened before the first hopper 1 reaches a vacuum state, that is, when the shutoff valve 3 is opened in a state where there is a large difference in pressure between the first hopper 1 and the second hopper 2, An impact is applied to the second hopper 2 and the feed screw housing 5 by the pressure of the first hopper 1. As a result, the molding material remaining in the second hopper 2 and the like is pushed out by the pressure of the first hopper 1 and directly supplied to the injection molding machine 15. As a result, the supply cylinder 6 is closed, and the moisture and volatile components of the molding material in the heating cylinder 11 are not sufficiently removed, and the molded product may be defective.

  Patent Document 1 discloses a method in which a vacuum gauge is installed in each hopper and the shutoff valve 3 is opened after confirming that the respective vacuum degrees are close to each other. In this method, the shutoff valve 3 cannot be opened immediately after the vacuum degree of the first hopper 1 and the vacuum degree of the second hopper 2 become close to each other, and it takes time to supply the molded product. As a result, productivity may be reduced.

  Further, since the vacuum pump 7 is operated more than necessary even after the vacuum degree of the first hopper 1 reaches the vacuum degree of the second hopper 2, the cost may be increased. In a large injection molding machine, when the distance between the vacuum gauges is increased, a problem that requires labor for the operator to check each vacuum gauge and decide when to open the shutoff valve 3 also occurs.

  Therefore, an object of the present invention is to provide an injection molding system that simplifies the setting of the timing for opening the shut-off valve and improves productivity without excessively supplying the molding material to the injection molding machine.

In order to achieve the above object, the present invention provides a first hopper into which a molding material constituting a molded product is charged, and a second hopper for receiving the molding material from the first hopper and supplying it to an injection molding machine. In an injection molding system comprising: a hopper, a shut-off valve that shuts off the first hopper and the second hopper, and a vacuum deaeration device that places each hopper in a vacuum state.
It further comprises a vacuum comparison device that compares the difference in vacuum between the first hopper and the second hopper and opens the shut-off valve when the difference in vacuum is equal to or less than a predetermined value.

  According to the present invention, it is possible to simplify the setting of the timing for opening the shutoff valve, and to improve productivity without excessively supplying the molding material to the injection molding machine.

It is the figure which showed the structure of the injection molding system in embodiment of this invention. It is the figure which showed the structure of the conventional injection molding system.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a diagram showing a schematic configuration of an injection molding system according to an embodiment of the present invention. The injection molding system includes a molding material supply device 13, a vacuum deaeration device 14, and an injection molding machine 15. The first hopper 1, the second hopper 2, the shutoff valve 3, the feed screw 4, the feed screw housing 5, and the supply cylinder 6 provided in the molding material supply device 13 are supplied with the molding material shown in FIG. 2. Since it is the same as that of each structure of the apparatus 13, those description is abbreviate | omitted. Vacuum pump 7, first vacuum pipe 8, second vacuum pipe 9 and valve 25 provided in vacuum degassing device 14, heater 10 provided in injection molding machine 15, heating cylinder 11, and injection screw 12 is the same as each conventional configuration, and the description thereof is omitted.

  In the embodiment of the present invention, the first hopper 1 and the supply cylinder 6 are provided with a first vacuum gauge 16 and a second vacuum gauge 17 for measuring respective vacuum degrees. The supply cylinder 6, the heating cylinder 11, the feed screw housing 5, and the second hopper 2 are not separated by a valve or the like, so that the pressures are equal. Therefore, the second vacuum gauge 17 measures the degree of vacuum of the second hopper 2.

  The first vacuum gauge 16 and the second vacuum gauge 17 are connected to a vacuum comparison device 18 that compares the measured degree of vacuum. The connection method depends on the conversion method of the measurement value of the vacuum gauge. When the measurement value is converted into an electric signal, the first vacuum gauge 16 and the second vacuum gauge 17 and the vacuum comparison device 18 are electrically connected by electric wiring or the like. Connected.

  The vacuum comparison device 18 is also electrically connected to the shut-off valve 3 using electric wiring or the like, and can transmit a signal for opening and closing the shut-off valve 3.

  Then, the structure which throws a molding material into the 1st hopper 1 in this invention is demonstrated. In the present invention, the charging method using the blower disclosed in Patent Document 1 is used.

  The first hopper 1 is connected by a material tank 19 for supplying a pellet-shaped molding material and a conveying pipe 20. A blower 21 for conveying a molding material from the material tank 19 to the first hopper 1 is also connected to the first hopper 1 using a blower pipe 22. A connection portion between the first hopper 1 and the blower pipe 22 may be provided with a filter or the like so that the molding material in the first hopper 1 is not conveyed to the blower 21. The conveyance pipe 20 and the blower pipe 22 are provided with valves 23 and 24 that can open and close each pipe. Each valve may be constituted by an electromagnetic valve or the like.

  Next, a method for supplying a molding material to the injection molding machine 15 by the injection molding system shown in FIG. 1 will be described.

  First, the valve 25 and the shutoff valve 3 are closed, and suction is performed from the supply cylinder 6 by the vacuum pump 7, and the heating cylinder 11, the supply cylinder 6, the feed screw housing 5 and the second hopper 2 are brought into a vacuum state. To do. Next, the valve 23 and the valve 24 are opened, and the blower 21 is used to suck the atmosphere present in the material tank 19, the transfer pipe 20, and the first hopper 1, thereby the first from the material tank 19. The molding material is conveyed to the hopper 1. Since the first hopper 1 and the blower pipe 22 are separated by a filter, the molding material is not conveyed to the blower 21 and stays in the first hopper 1. When a sufficient amount of the molding material is conveyed to the first hopper 1, the blower 21 is stopped and the valve 23 and the valve 24 are closed.

  Since the first hopper 1 is now at atmospheric pressure, in order to move the molding material staying in the first hopper 1 to the second hopper 2, the first hopper 1 is individually evacuated. There must be. Therefore, the valve 25 is opened, and the atmosphere of the first hopper 1 is sucked by the vacuum pump 7.

  The measured values of the first vacuum gauge 16 provided in the first hopper 1 and the second vacuum gauge 17 provided in the supply cylinder 6 are sent to a vacuum comparison device 18. When the difference between the measured values of the vacuum gauge 16 and the vacuum gauge 17 becomes a predetermined value or less, that is, the vacuum difference between the first hopper 1 and the second hopper 2 becomes a predetermined vacuum difference or less. When this occurs, the vacuum comparison device 18 gives a signal for opening the shutoff valve 3 to the shutoff valve 3.

  The shutoff valve 3 is opened by a signal from the vacuum comparison device 18, and the molding material staying in the first hopper 1 moves to the second hopper 2. At this time, the predetermined value is set to a pressure value at which no impact is applied to the second hopper 2 and the feed screw housing 5 by the pressure of the first hopper 1. It is better to set a value close to the pressure of the second hopper 2.

  When the molding material has finished moving from the first hopper 1 to the second hopper 2, the shutoff valve 3 and the valve 25 are closed. The molding material that has moved to the second hopper 2 is pushed out to the supply cylinder 6 by the feed screw 4 and is supplied to the heating cylinder 11 of the injection molding machine 15 by dropping inside the supply cylinder 6.

  The molding material supplied to the heating cylinder 11 is melted by the frictional heat and shearing heat generated with the rotation of the injection screw 12 and the heat applied from the heater 10 provided on the outer periphery of the heating cylinder 11. At that time, moisture and volatile components contained in the molding material are released. The released moisture and volatile matter are sucked from the supply cylinder 6 by the vacuum pump 7. Therefore, the molding material can be dissolved without moisture and volatile matter staying in the heating cylinder 11, and the moisture and volatile matter can be removed from the molding material. Therefore, in the manufacture of a molded product, it can be molded without causing defects such as resin burns and bubbles.

  When the molding material is added to the second hopper 2, the molding material must be conveyed from the material tank 19 to the first hopper 1 again. When it is known that the molding material must be added to the second hopper 2 in advance, the transfer of the molding material from the first hopper 1 to the second hopper 2 is completed. The conveyance to the first hopper 1 may be started.

  The valve 23 and the valve 24 are opened, the blower 21 is operated, and the molding material is conveyed from the material tank 19 to the first hopper 1. After the conveyance, the blower 21 is stopped and the valves 23 and 24 are closed. Subsequently, the valve 25 is opened, and the first hopper 1 is brought into a vacuum state by the vacuum pump 7.

  The shutoff valve 3 is opened when the difference in vacuum between the first hopper 1 and the second hopper 2 becomes a predetermined value or less. The predetermined value is a value at which an impact is not applied to the second hopper 2 and the feed screw housing 5 by the pressure of the first hopper 1. Therefore, when the shutoff valve 3 is opened, the molding material remaining in the second hopper 2 and the feed screw housing 5 is not subjected to an impact, and the molding material of the first hopper 1 is applied to the second hopper 2. Can be moved.

  Further, the vacuum comparison device 18 compares the degree of vacuum of the first hopper 1 and the degree of vacuum of the second hopper 2. Further, the shut-off valve 3 is opened by a signal from the vacuum comparison device 18. Therefore, it is possible to increase the accuracy of the timing for opening the shutoff valve 3, and to reduce the operation of the vacuum pump more than necessary after the degree of vacuum of the first hopper 1 reaches a sufficient value. it can. Further, in a large injection molding machine, even if the distances between the vacuum gauges are separated, the vacuum comparison device 18 compares the vacuum degrees and opens and closes the shut-off valve 3, so that the vacuum degree can be confirmed. Does not require operator effort.

  As described above, it is possible to simplify the setting of the timing for opening the shut-off valve and improve the productivity without excessively supplying the molding material to the injection molding machine.

DESCRIPTION OF SYMBOLS 1 Hopper 2 Hopper 3 Shut-off valve 4 Feed screw 5 Feed screw housing 6 Supply cylinder 7 Vacuum pump 8 Vacuum pipe 9 Vacuum pipe 10 Heater 11 Heating cylinder 12 Injection screw 13 Molding material supply apparatus 14 Vacuum deaerator 15 Injection molding machine 16 Vacuum gauge 17 Vacuum gauge 18 Vacuum comparison device 19 Material tank 20 Transport piping 21 Blower 22 Blower piping 23 Valve 24 Valve 25 Valve

Claims (2)

A first hopper into which a molding material constituting the molded article is charged; a second hopper for receiving the molding material from the first hopper and supplying the molding material to the injection molding machine; the first hopper and the first hopper In an injection molding system comprising: a shutoff valve that shuts off the two hoppers; and a vacuum deaeration device that places each of the hoppers in a vacuum state;
A vacuum comparison device that compares a difference in vacuum between the first hopper and the second hopper and opens the shut-off valve when the difference in vacuum is equal to or less than a predetermined value; Injection molding system.   2. The injection molding system according to claim 1, wherein the predetermined value is a difference in the degree of vacuum in which an impact is not applied to at least the second hopper by the pressure of the first hopper.

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