JP2010208263A - Injection molding machine and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding machine which can suck gas or moisture from a material by making the interior of a heating cylinder vacuum and thereby, upgrade energy efficiency, as well as a method of controlling the injection molding machine. <P>SOLUTION: The injection molding machine 11 makes a molded object by melting the material inside the heating cylinder 23 of an injection device 13 and setting the molten material in the cavity 21 of molding dies 19 and 20. In addition, the injection molding machine includes a vacuum suction mechanism 38 which makes the interior of the heating cylinder 23 vacuum and an induction heating device 42 which heats the heating cylinder 23. The melting process is started by heating up the material with the help of the induction heating device 42. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an injection molding machine and a control method thereof.

  In an injection molding machine, a material is melted in a heating cylinder of an injection device, and gas and moisture are generated at that time. If the material in which the gas and moisture are mixed is solidified in the cavity of the molding die to form a molded product, problems such as defects such as silver streak and adhesion of gas components to the die occur. In order to solve the above problem, in Patent Document 1, gas and moisture are sucked in vacuum from the top through the drop port of the heating cylinder. And in patent document 1, suction | inhalation of a gas and a water | moisture content is made easy by setting the preset temperature of a heating cylinder rear zone high, and making material melt | dissolve early in a heating cylinder rear part.

  On the other hand, the housing portion of the injection apparatus that supplies the material needs to be temperature-controlled at a certain temperature or less in order to prevent the material from melting and adhering. Therefore, the heating cylinder rear zone adjacent to the housing portion is deprived of heat most by the housing portion having a large heat capacity. Further, the heating cylinder rear zone is a thorn that first rapidly raises the temperature of the supplied material, and therefore requires the most amount of heat. In particular, in the injection molding machine of Patent Document 1, since the set temperature of the heating cylinder rear zone is set higher than that of a normal injection molding machine, a larger amount of heat is generated in order to maintain the heating cylinder rear zone at the setting temperature. It was necessary.

  Moreover, in the heating cylinder of the conventional injection apparatus, an electric heater that generates resistance heat is used in each zone. However, the electric heater has a problem that the amount of heat released from the surface of the heating cylinder is large, and the energy efficiency is poor in order to melt the internal material. And especially in patent document 1, in order to maintain the temperature of the said heating cylinder rear zone at high temperature rather than usual, the heating with an electric heater was very bad in energy efficiency. And the tendency was so remarkable that the resin material which needs to make the preset temperature of a heating cylinder rear zone much higher temperature.

JP 2009-12447 A (Claim 1, Claim 2, FIG. 1)

  In the present invention, in view of the above problems, an injection molding machine capable of improving energy efficiency and an injection molding machine control method in an injection molding machine that draws gas and moisture from a material in a vacuum state in a heating cylinder. The purpose is to provide.

  An injection molding machine according to claim 1 of the present invention is an injection molding machine that melts a material in a heating cylinder of an injection device and solidifies the molten material in a cavity of a molding die to mold a molded product. A vacuum suction mechanism for evacuating the inside of the heating cylinder and an induction heating device for heating the heating cylinder are provided.

  An injection molding machine according to a second aspect of the present invention is the injection molding machine according to the first aspect, wherein the induction heating device is provided in a rear zone of the heating cylinder adjacent to the housing portion.

  According to a third aspect of the present invention, there is provided a method for controlling an injection molding machine comprising: injection molding in which a material is melted in a heating cylinder of an injection device, and the molten material is solidified in a cavity of a molding die. In the machine control method, the inside of the heating cylinder is evacuated by a vacuum suction mechanism, and the temperature of the material is raised by an induction heating device provided in the rear zone of the heating cylinder adjacent to the housing portion to start melting.

  The method for controlling an injection molding machine according to claim 4 of the present invention is characterized in that, in claim 3, the material is an undried resin material.

  Since the injection molding machine of the present invention includes the vacuum suction mechanism that makes the inside of the heating cylinder a vacuum state and the induction heating device that heats the heating cylinder, energy efficiency can be improved. As for the control method of the injection molding machine of the present invention, the inside of the heating cylinder is evacuated by the vacuum suction mechanism, and the material is heated by the induction heating device provided in the rear zone of the heating cylinder adjacent to the housing portion to start melting. Therefore, the energy efficiency can be improved even if the heating cylinder rear zone is set at a higher temperature than a general injection molding method.

FIG. 1 is a schematic explanatory diagram of an injection molding machine according to the first embodiment. FIG. 2 is an enlarged cross-sectional view of the rear portion of the heating cylinder of the injection molding machine according to the first embodiment. FIG. 3 is a diagram illustrating temperature setting values of the heating cylinder of the injection molding machine according to the first embodiment.

  An injection molding machine according to the present invention includes a vacuum suction mechanism that vacuum-sucks the inside of a heating cylinder through an opening provided in a housing part and an opening provided in a feed cylinder of a feed screw, and induction heating that heats the heating cylinder. Device. The vacuum suction mechanism vacuums the inside of the heating cylinder, and the energy efficiency is improved by heating the material such as resin and starting melting by an induction heating device provided in the rear zone of the heating cylinder adjacent to the housing part. In addition, the temperature in the rear zone of the heating cylinder can be stably maintained. Depending on the type of molded product and material, undried resin material may be used. In that case, the cost of installing the dryer and the power consumption required for the dryer can be reduced, further reducing costs. It becomes possible.

  As shown in FIG. 1, a mold clamping device 12 and an injection device 13 are arranged on a bed (not shown) of the injection molding machine 11. In the mold clamping device 12, a tie bar 16 is inserted between the stationary platen 14 and the pressure receiving plate 15, and a movable platen 17 is slidably provided on the tie bar 16. The ram of the mold clamping mechanism 18 provided on the pressure receiving plate 15 is fixed to the back surface of the movable plate 17. Further, a fixed mold 19 of a molding die is attached to the fixed platen 14, a movable mold 20 of a molding die is attached to the movable platen 17, and the fixed mold 19 and the movable mold 20 are closed. At this time, a cavity 21 is formed. The mold clamping mechanism including the mold opening / closing mechanism may be of another type such as a toggle mechanism.

  The injection device 13 is provided with a housing portion 24 to which a heating cylinder 23 containing a screw 22 is fixed. A drop port 25 for supplying a material such as a resin is provided at the upper center of the housing portion 24, and is connected to the drop port of the heating cylinder 23. A transport cylinder 27 for the feed screw 26 is provided in the horizontal direction above the housing portion 24 via a vertical supply cylinder. A cooling flow path 28 is provided in the housing portion 24, and a cooling medium is sent from the temperature adjustment device 29. It is also assumed that a heat insulating material is provided between the housing portion 24 and the heating cylinder 23. The screw 22 includes zones of a feed zone 22a, a compression zone 22b, and a metering zone 22c, and a backflow prevention valve and a screw head are provided in the front. A seal member 30 seals between the shaft 22 d at the rear end of the screw 22 and the inner hole of the heating cylinder 23. The rear end of the screw 22 is connected to a measuring motor 31 via a sleeve portion (not shown), and the screw 22 is rotated by the rotation of the measuring motor 31. Further, as is well known, the injection device 13 is provided with an injection motor (not shown), its drive mechanism, a pusher plate portion, and the like, and the screw 22 can be moved back and forth.

  A motor 32 for rotating the feed screw 26 is provided at the rear part of the conveying cylinder 27 of the feed screw 26, and a supply cylinder 33 is connected to the rear side of the upper surface of the conveying cylinder 27. The supply cylinder is provided with an upper shutter 34a and a lower shutter 34b, and the supply cylinder 33 is divided into an upper chamber, an intermediate chamber, and a lower chamber by an upper shutter 34a and a lower shutter 34b. The supply cylinder 33 is provided so that the inside of the heating cylinder (including the inside of the conveyance cylinder 27 in which the feed screw 26 is accommodated) is always in a vacuum state even when the material is supplied. Further, an opening 35 of the vacuum suction means is provided on the front side of the upper surface of the transport cylinder 27 of the feed screw 26, and a vacuum pump of the vacuum suction means is provided via a pipe line 36 attached to the opening 35 and an on-off valve 37. 38. The vacuum suction means includes a filter, a silencer, a deodorizing device, etc., not shown. It is desirable that the opening 35 of the vacuum suction means be provided behind the heating cylinder rear zone 23a in order to avoid clogging with the molten resin. As an example, the opening may be provided in the rear end of the heating cylinder (between the shaft portion 22 d of the screw 22 and the heating cylinder 23) or the housing portion 24.

  The heating cylinder 23 is made of cylindrical nitrided steel (conductive material) having a predetermined thickness. A cylinder head 39 is fixed in front of the heating cylinder 23, and a nozzle 40 is fixed to the cylinder head 39. In the first embodiment, the temperature control zone is divided into a heating cylinder rear zone 23a, a heating cylinder middle zone 23b, a heating cylinder front zone 23c (including the cylinder head 39), and a nozzle zone 40a, and the temperature control zones are controlled to different temperatures. It is possible. Although the screw 22 moves back and forth during weighing, the heating cylinder rear zone 23a substantially corresponds to the feed zone 22a of the screw 22, and the heating cylinder middle zone 23b substantially corresponds to the compression zone 22b of the screw 22, and the front of the heating cylinder. The part zone 23 c substantially corresponds to the metering zone 22 c of the screw 22. A band heater 41 (electric heater) that generates heat by normal resistance heating is attached to the heating cylinder middle zone 23b, the heating cylinder front zone 23c, and the nozzle zone 40a. An induction heating device 42 is attached to the heating cylinder rear zone 23a. The injection molding machine 11 is provided with a controller 43, and signal lines are connected from the controller 43 to the temperature control device 29, the control device 44 of the induction heating device 42, the changeover switch 45 of the band heater 41, and the like. Each zone 23a, 23b, 23c, etc. of the heating cylinder 23 is provided with a thermocouple (not shown), the detected temperature is sent to the controller 43, and the temperature of the heating cylinder 23 is subjected to closed loop control (PID control). It is like that. Further, the temperature control device 29, the band heater 41, and the induction heating device 42 are energized by connecting a power line from a power source 46. The number of band heaters 41 in each zone is not limited to one. Further, the number of zones is not limited to the above.

  As shown in FIG. 2, in the induction heating device 42, a concave groove 47 for allowing compressed air to flow is formed on the outer peripheral surface of the heating cylinder 23. In the first embodiment, the concave groove 47 is formed in a spiral shape, but is formed in a reverse screw direction so as to cross a winding direction of a coil 48 wound in a spiral shape, which will be described later. It is desirable that the groove 47 does not overlap with the direction of the coil 48 in order to secure the cross-sectional area of the cooling channel 51, and a groove may be provided along the longitudinal direction of the heating cylinder 23. The cooling device 50 is connected to the compressed air supply device 52 via a hose on the housing portion side of the concave groove 47, and the nozzle side is open to the outside air.

  A heat insulating material 49 is wound around the heating cylinder 23. The heat insulating material 49 is a material that can withstand a high temperature of about 400 ° C., and has a thickness of about 5 to 30 mm. The heat insulating material 49 may be wound with the above thickness in one layer, or a thin material with multiple layers. A cooling flow path 51 of the cooling device 50 is formed by the concave groove 47 and the heat insulating material 49. The coil 48 is spirally wound around the outer peripheral surface of the heat insulating material 49. In the coil 48, a conductive wire 48a is covered with a heat-resistant insulating layer 48b. The coil 48 is connected to the control device 44 so that a high-frequency current generated by the control device 44 can be energized.

  Although the cooling device 50 of the induction heating device 42 is not indispensable, the temperature of the heating cylinder 23 around which the heat insulating material 49 is wound becomes slow, so that the cooling can be promoted by using the cooling device 50. The cooling device 50 of the first embodiment can simplify the equipment by sending the compressed air to the cooling flow path 51 formed between the heat insulating material 49 and the concave groove 47 of the heating cylinder 23. As another cooling system, a cooling medium such as compressed air or cooling water may be passed through the metal pipe. Furthermore, the coil 48 and the cooling device 50 of the induction heating device 42 provided in the heating cylinder rear zone 23a are not limited to one system and may be two systems or more.

  Next, a control method of the injection molding machine 11 will be described with reference to FIG. In the injection molding machine 11, the set temperatures of the heating cylinder rear zone 23a and the housing part 24 are set higher than those of a normal injection molding machine. Specifically, the heating cylinder rear zone 23a is set to the same temperature as the heating cylinder middle zone 23b. Further, as an example, the temperature of the heating tube rear zone 23a is desirably set within a range of plus or minus 20 ° C., and more preferably within a range of plus or minus 10 ° C. with respect to the heating tube middle zone 23b. The reason why the temperature of the heating cylinder rear zone 23a is set to be relatively high is that the resin material is melted early in the heating cylinder rear zone 23a, thereby inducing gas and moisture early and facilitating vacuum suction. The main reason for increasing the set temperature of the housing part 24 is to prevent the generated moisture from being cooled and condensed in the housing part 24.

  In the first embodiment, the heating zone rear zone 23a is heated by the induction heating device 42. A high frequency current is passed through the coil 48 of the induction heating device 42 from the control device 44 and an induction current is generated in the heating cylinder 23 to generate heat from the actual part of the heating cylinder 23. Therefore, unlike the case where the band heater 41 is used, there is no heat distribution in which the temperature decreases from the surface side toward the inside of the heating cylinder 23, and the temperature can be raised and maintained up to a high temperature range. Further, heat radiation from the heating cylinder 23 is suppressed by the heat insulating material 49. In the induction heating device 42 according to the first embodiment, the control device 44 generates and controls the high-frequency frequency sent to the coil 48. However, the current value sent to the coil may be controlled, or the type in which the high-frequency current is controlled to be turned on and off by the switch 45 or the like may be used similarly to the band heater 41.

  The inside of the heating cylinder is always sucked by a vacuum pump 38 of a vacuum suction mechanism and is in a vacuum state. As an example, the degree of vacuum is −90 kPa or less (11.33 kPa on an absolute pressure basis) to −101 kPa (0.33 kPa on an absolute pressure basis) in terms of gauge pressure (based on atmospheric pressure). In the first embodiment, no drying device is provided, and an undried resin material (polycarbonate as an example) is supplied through the supply cylinder 33 and the feed screw 26. Supply of the resin material to the groove portion of the screw 22 in the heating cylinder is performed during measurement and is controlled so that the supply amount is reduced by the feed screw 26 (supplied so that the inside of the heating cylinder is starved). ) The resin material supplied to the groove portion (screw shaft 22h) of the screw 22 is sent to the compression zone 22b from the feed zone 22a in a starved state by rotating the screw 22 by driving the measuring motor 31. And when it is sent to the metering zone 22c, it is further heated by shearing and sent to the front of the screw 22. When the measurement is performed in a starved state, the resin material whose supply amount is limited as described above is moved along the front surface 22f side of the flight 22e of the screw 22 in the feed zone 22a, and the rear surface of the flight 22e of the screw 22 On the 22g side, the space or the resin material is sparse. Since the thickness of the screw shaft 22h in the feed zone 22a is uniform, the resin material is hardly affected by the shear heat generated by the screw rotation, and is heated and melted exclusively by the heat from the heating cylinder 23.

  As described above, since the heating cylinder rear zone 23a is set higher than the set temperature of the heating cylinder rear zone of a normal injection molding machine, the resin material starts to melt at this portion. At this time, the heating tube rear zone 23a is heated by using the induction heating device 42, and the temperature is raised from the inside of the plate thickness portion of the heating tube 23 and the heat insulating material 49 prevents heat dissipation. Stable temperature rise and maintenance can be achieved with power consumption of 30 to 70% when using. And even if it is an undried resin material (normal temperature), it can heat up favorably. In the case of an undried resin material, more water is generated when it is melted than the dried resin material. However, the moisture and gas generated from the resin material are sent rearward through the space formed on the flight rear surface 22g side of the screw 22 as described above, and further passed through the drop opening 25, the opening 35, the pipe line 36, and the like. Then, vacuum suction is performed by the vacuum pump 38. Then, when the molten resin is stored in front of the screw 22 by the measuring step, an injection motor (not shown) is operated next, and a cavity between the fixed mold 19 and the movable mold 20 clamped by the mold clamping device 12 is operated. 21 is injected. Since the molded product is free of moisture, there is almost no defect such as silver streak and the gas hardly adheres to the cavities 21 of the molding dies 19 and 20.

  Further, when the molding operation is interrupted or when the heating cylinder 23 is changed to a resin material whose setting temperature may be low, energization to the coil 48 of the induction heating device 42 is stopped and the heating cylinder rear zone 23a is cooled. To do. Cooling of the heating cylinder rear zone 23 a is performed by sending compressed air to the cooling flow path 51 of the cooling device 50. In this case, the temperature distribution in the heating cylinder rear zone 23a is a low temperature on the housing portion 24 side and a desirable temperature curve is obtained by performing from the housing portion 24 side. In some cases, the temperature may be adjusted by sending compressed air from the front side of the heating cylinder rear zone 23a.

  In the present invention, it is not excluded that the heating cylinder middle zone 23b, the heating cylinder front zone 23c, and the nozzle zone 40a are also induction heating devices, but at least the heating cylinder rear zone 23a is provided with the induction heating device 42. It is desirable to provide it. The reason why the induction heating device 42 is provided only in the heating tube rear zone 23a in the first embodiment is as follows. The first reason is that the induction heating device 42 has a higher cost than the band heater 41, and the cost increases when many zones are used as the induction heating device 42. The second reason is that the heating cylinder rear zone 23a is the zone that consumes the most power. For example, when the inside of the heating cylinder is in a vacuum state and the heating cylinder rear zone 23a is set to the same temperature as or close to the heating cylinder middle zone 23b, when all the zones are the band heaters 41, the entire heating cylinder including the nozzle 40 is heated. About 30 to 60% of the power consumption for this is consumed for heating the heating cylinder rear zone 23a. Accordingly, it is most effective in terms of energy saving to provide the induction heating device 42 in the heating tube rear zone 23a, and the power consumption of the heating tube rear zone 23a is reduced by about 30 to 60% compared to the case of the band heater 41. it can. As a third reason, since the heating cylinder front zone 23c and the like have a higher set temperature and are not adjacent to the housing part 24 from which heat is taken away, a large cooling device 50 is added to the induction heating device 42. If it is not provided, it is possible to cool well. The point heating cylinder rear zone 23a is adjacent to the housing part 24 and has a lower set temperature than the heating cylinder front zone 23c. Therefore, the cooling device 50 can easily lower the temperature. Even simple compressed air is sufficient.

  As for the injection molding machine 11 of the present invention, the higher the set temperature such as PC, PET, PMMA, PPS (for example, the set temperature of the heating cylinder rear zone 23a is 220 ° C. or higher), the greater the energy saving effect is used. The resin material is not limited. The injection molding machine 11 has a greater energy saving effect for uniformly raising the thickness of the thick heating cylinder 23 as it is larger than a middle size such as a screw diameter of 45 mm or more, but the size of the injection molding machine is not limited. The injection molding machine may use a plunger as an injection mechanism. In that case, the induction heating device 42 is attached to the rear zone of the heating cylinder, which is a plasticizing device. The injection device may be a vertical type.

DESCRIPTION OF SYMBOLS 11 Injection molding machine 13 Injection apparatus 22 Screw 22a Feed zone 22b Compression zone 22c Metalling zone 23 Heating cylinder 23a Heating cylinder rear zone 23b Heating cylinder middle zone 23c Heating cylinder front zone 38 Vacuum pump (vacuum suction mechanism)
41 Band heater 42 Induction heating device 47 Concave groove 48 Coil 49 Heat insulating material 50 Cooling device 51 Cooling flow path

Claims (4)

In an injection molding machine that melts a material in a heating cylinder of an injection device and solidifies the melted material in a cavity of a molding die to mold a molded product,
A vacuum suction mechanism for evacuating the heating cylinder;
An injection molding machine comprising an induction heating device for heating a heating cylinder. The injection molding machine according to claim 1, wherein the induction heating device is provided in a rear zone of a heating cylinder adjacent to the housing portion. In a control method of an injection molding machine that melts a material in a heating cylinder of an injection device and solidifies the melted material in a cavity of a molding die to mold a molded product,
A method for controlling an injection molding machine, wherein the inside of a heating cylinder is evacuated by a vacuum suction mechanism, and the material is heated to start melting by an induction heating device provided in a rear zone of the heating cylinder adjacent to the housing portion. The method for controlling an injection molding machine according to claim 3, wherein the material is an undried resin material.

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