JP2008100367A - Injection molding machine and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mold a thin plate molded product having high quality free from a weld line and a large area by an injection molding method. <P>SOLUTION: In this injection molding machine including a plurality of injection units for injecting the same resin material to fill one cavity of a mold, a time lag is provided to the injection and filling start timing of a molten resin into the cavity by a plurality of the injection units and the resin due to the injection unit previously starting injection filling advances through the cavity. After the resin from the injection unit previously starting injection filling is passed through the injection part of the injection unit starting the next injection filling, the injection filling from the injection unit starting the injection filling next is started. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique related to an injection molding machine capable of molding a high-quality, large-area thin sheet molded product.

  When automobile window panels are made of plastic, the specific gravity of plastic is about 50% of that of glass. This reduces the weight of the vehicle body and leads to a reduction in fuel consumption. It also contributes to improving the performance. Furthermore, plastic has various advantages such as high impact strength and easy adaptation to complicated shapes compared to glass. Therefore, attempts to manufacture plastic window panels made of large-area plastics by the injection molding method with high productivity, which is widely used as a plastic molding method, have been actively performed recently. It is believed that there is.

  A mold cavity for forming a thin plate having a large area (a space for forming a molded product) is naturally a large-area space having a small thickness. When injection filling of molten resin is performed, the progress of solidification of the resin gets in the way, the resin does not spread well to every corner of the cavity, the speed of solidification of the resin at the resin entrance side and the back of the cavity is different, There arises a disadvantage that the resin density tends to vary.

  Therefore, as shown in FIG. 6, a plurality of injection units 102 are provided for one cavity 101, and the plurality of injection units 102 are spaced from each other at a predetermined distance (in the example of FIG. Conventionally, a method has been generally adopted in which injection filling is started simultaneously by a plurality of injection units 101 and the resin 103 is spread to every corner of the cavity 102. In FIG. 6, reference numeral 103 denotes a molten resin, a resin that has started to solidify, or a solidified resin.

  As is well known, the molten resin 103 injected from the injection part (resin injection part) of the cavity 101 into the cavity 101 by the injection unit 102 advances while rapidly expanding in the cavity 101, A thin solidified film called a skin layer (skin layer) is formed on the surface of the resin 103 and proceeds in the cavity 101 (the chain line in FIG. 6 schematically shows the progress of the skin layer). . As shown in FIG. 6, when the molten resin 103 is injected into the cavity 101 simultaneously from a plurality of injection units 102, the resin 103 injected from each injection unit 102 merges so that the skin layers are abutted with each other. The resin 103 is integrated and solidified at the joining portion.

  However, when a plurality of resin flows are merged and integrated as described above, it is unavoidable that a weld line 104 is generated at the merged portion as shown in FIG. There is no problem in the case of a molded product in which this weld line can be ignored, but in the case of an automotive window plate, a transparent and large-area thin plate is required, so the presence of the weld line makes the appearance worse, In the first place, this is not acceptable from the viewpoint of passenger visibility, and the weld line also greatly deteriorates the reliability of strength.

  The present invention has been made in view of the above points, and an object of the present invention is to make it possible to form a high-quality large-area thin plate-shaped product without a weld line by an injection molding method.

In order to achieve the above-mentioned object, the present invention provides an injection molding machine including a plurality of injection units that perform injection filling of the same resin material into one cavity of a mold.
By giving a time difference to the timing of injecting and filling molten resin into the cavity by a plurality of injection units, the resin by the injection unit that started injection filling first proceeds in the cavity, and by the injection unit that started injection filling earlier After the resin has passed through the injection portion (resin injection portion = resin injection inlet portion of the resin into the cavity) by the injection unit that starts injection filling next, injection filling by the injection unit that starts injection filling next is started.

  In the present invention, for example, first, injection filling of the molten resin into the cavity is started by the injection unit A, and the resin (molten resin) injected by the injection unit A proceeds in the cavity, Immediately after passing through the injection portion by the injection unit B, the injection resin B starts injection filling of the molten resin, and the molten resin injected by the injection unit B so as to break through the skin layer of the resin previously injected and filled. Is injected into the molten resin injected by the injection unit A, injection filling by the injection unit B is performed, and the resin (molten resin) injected by the injection units A and B advances in the cavity, and this Immediately after the resin has passed through the injection part by the injection unit C, the injection filling of the molten resin by the injection unit C is started and the injection filling is performed first. The as break through a skin layer of resin, the injection unit C injection unit the injected molten resin by A, so as to inject into the injected molten resin by B, performing an injection filling by injection unit C. Also, for example, first, injection filling of the molten resin into the cavity is started by the injection unit A, and the resin (molten resin) injected by the injection unit A travels through the cavity. Immediately after passing through the injection part by C, injection filling of the molten resin by the injection units B and C is started and injected by the injection units B and C so as to break through the skin layer of the resin previously injected and filled. The molten resin is injected into the molten resin injected by the injection unit A, and injection filling is performed by the injection units B and C. The resin (molten resin) injected by the injection units A, B, and C is the cavity. Immediately after this resin passes through the injection part by the injection units D and E, the injection filling of the molten resin by the injection units D and E is opened. The molten resin injected by the injection units D, E is injected into the molten resin injected by the injection units A, B, C so as to penetrate the resin skin layer previously injected and filled. Then, injection filling by the injection units D and E is performed. As described above, in the present invention, the molten resin injected by the next injection unit is given a time difference in the injection start timing by the plurality of injection units so as to break through the skin layer of the resin previously injected and filled, Since the injection filling is controlled so as to be injected into the previously injected molten resin, new hot molten resin is replenished to the top side of the resin traveling in the cavity, and thereby, every corner in the back of the cavity The resin spreads smoothly, the solidification speed of the resin at the resin entrance side and the back of the cavity can be equalized, and the variation in resin density can be reduced as much as possible. Furthermore, the injection filling is controlled so that the molten resin injected by the next injection unit is injected into the previously injected molten resin so as to break through the skin layer of the previously injected filled resin. As in the prior art, the top skin layers of the plurality of resin flows are not brought into contact with each other, and therefore no weld line is generated.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 5 relate to an injection molding machine according to an embodiment of the present invention (hereinafter referred to as the present embodiment), and FIGS. 1 and 2 illustrate a mechanism configuration of a main part of the injection molding machine of the present embodiment. It is explanatory drawing shown. The injection molding machine of this embodiment is an example of application to a horizontal injection type machine by vertical clamping (vertical mold opening / closing).

  1 and 2, reference numeral 1 denotes a fixed die plate fixed to an appropriate holding frame, 2 denotes a fixed side mold (lower mold) fixed to the fixed die plate 1, and 3 denotes a molding operation state. A tail stock 4 that is held in a fixed position is a plurality of tie bars 5 that are connected to the fixed die plate 1 and the tail stock 3, and 5 is inserted and guided through the tie bar 4. A movable die plate that can move back and forth (up and down), 6 is a movable die (upper die) fixed to the movable die plate 5, and 7 is a mold opening / closing servo mounted on the tailstock 3. A motor (clamping servomotor) 8 is a driving pulley fixed to the output shaft of the mold opening / closing servomotor 7, 9 is a ball screw mechanism for converting the rotation of the mold opening / closing servomotor 7 into a linear motion, 10 is The tails The nut body 11 of the ball screw mechanism 9 rotatably held by the hook 3 is screwed into the nut body 10 and is moved back and forth (up and down) by the rotation of the nut body 10. Is a driven pulley that is fixed to the nut body 10 and transmits the rotation of the servo motor 7 for opening and closing the mold via a driving pulley 8 and a timing belt (not shown), and 13 includes a tail stock 3 and a movable die plate 5. A toggle link mechanism that is connected and driven to extend or fold when the screw shaft 11 of the ball screw mechanism 9 moves forward (down) or backward (up), thereby moving the movable die plate 5 forward (down) or backward (up). Reference numeral 14 denotes a cavity formed by both molds 2 and 6. In FIGS. 1 and 2, the cavity 14 is depicted as having a certain thickness for convenience of illustration, but this cavity 14 actually forms a window plate for automobiles having a large area and a thin plate. Therefore, the molds 2 and 6 are manufactured so as to be a space having a small thickness and a large area. In addition to the rectangular shape, the cavity 14 can be arbitrarily designed so that an automotive window plate having an arbitrary planar shape such as a trapezoid, a triangle, or a pentagon, or an arbitrary curved shape can be formed. It has become possible.

  21, 22, and 23 are arranged in a direction orthogonal to the main plane of the cavity 14, that is, from the end surface in the thickness direction of the cavity 14, so that the molten resin is respectively injected and filled into the cavity 14. 1 and 2, the injection units 21, 22, and 23 are illustrated in a simplified manner, but the injection units 21, 22, and 23 are known in-line screw type injection units. It is configured. In the present embodiment, the number of injection units is three. However, the number of injection units may be an arbitrary number of 2 or more depending on the area and shape of the cavity. In this embodiment, an inline screw type injection unit is used, but a pre-plastic type injection unit may be used.

  In the configuration shown in FIGS. 1 and 2, although not shown, in the mold open state, the toggle link mechanism 13 is in the most folded state, and the movable die plate 5 is in the raised retracted position. When the mold opening / closing servomotor 7 is rotationally driven in a predetermined direction from the mold open state, the nut body 10 of the ball screw mechanism 9 is rotationally driven through the drive pulley 8, the timing belt (not shown), and the driven pulley 12. As a result, the screw shaft 11 of the ball screw mechanism 9 moves forward (lowers), the toggle link mechanism 13 is driven to extend, and the movable die plate 5 moves forward (lowers). The advance of the movable die plate 5 is stopped at the timing when the cavity 14 for injection filling is formed by the movable side mold 6 and the fixed side mold 2 by the advance of the movable die plate 5. The mold opening / closing servomotor 7 is controlled so as to output a torque commensurate with a predetermined mold clamping force so as to maintain (to maintain the position against the resin pressure in the injection filling process described later). FIG. 1 shows a state before such injection filling (immediately after completion of mold closing).

  In the present embodiment, the injection filling after the mold closing is completed, first, the first injection unit 21 starts the injection filling of the molten resin into the cavity 14, and the resin injected by the first injection unit 21. (Molten resin) travels in the cavity 14 and immediately after the top of the resin by the first injection unit 21 passes through the injection portions for the second and third injection units 22 and 23, the second and third injections The injection filling of the molten resin by the units 22 and 23 is started. Here, examples of the resin material used for molding in the present embodiment include polycarbonate resin and acrylic resin, thereby forming a transparent large-area window plate.

  FIG. 3 is a schematic diagram for explaining the state of injection filling of the present embodiment, and FIG. 4 is a schematic diagram in a direction orthogonal to FIG. As shown in FIG. 3, the injection part of the first injection unit 21 is provided at the center of one short side of the cavity 14, and the injection parts of the second and third injection units 22, 23 are the cavity 14. These two long sides are symmetrically provided with a predetermined distance from the injection part of the first injection unit 21. The one-dot chain line in FIG. 3 shows the state of transition of the skin layer (skin layer) on the surface of the resin 31 on the leading side when the resin 31 travels through the cavity 14 from the left side to the right side in the figure. Yes. 3, 2, and 4 indicate a molten resin, a resin that has started to solidify, or a solidified resin.

  In the present embodiment, the injection filling of the molten resin by the second and third injection units 22 and 23 is started at the same time when the skin layer reaches Sn in FIG. 2. By the resin pressure of the molten resin injected from the third injection units 22 and 23, the skin layer of the resin 31 previously injected by the first injection unit 21 is pierced, and the second and third injection units 22 and 23 The second and third injection units 22 and 23 perform injection filling by injecting the molten resin injected by the first injection unit 21 into the molten resin injected by the first injection unit 21.

  Thus, in this embodiment, the first injection unit 21 and the second and third injection units 22 and 23 have a time difference between the injection start timings of the resin 31 previously injected and filled by the first injection unit 21. The molten resin 31 injected by the second and third injection units 22 and 23 at the next stage is injected into the molten resin 31 previously injected by the first injection unit 21 so as to penetrate the skin layer. Since injection filling is controlled, new hot molten resin is replenished to the leading side of the resin 31 traveling in the cavity 14, whereby the resin can smoothly spread to every corner of the cavity 14 and the cavity 14. The resin solidification speed at the resin entrance side and the back of the resin can be equalized, and variations in resin density can be reduced as much as possible. Further, the injection filling is controlled so that the molten resin 31 injected by the next injection unit is injected into the previously injected molten resin 31 so as to penetrate the skin layer of the previously injected injection filled resin 31. Therefore, unlike the conventional case, the top skin layers of the plurality of resin flows are not brought into contact with each other, and therefore no weld line is generated.

  In this embodiment, when the injection filling process is completed, the compression process is started immediately. In this compression process, the mold opening / closing servomotor 7 is controlled so that a compression force larger than the mold clamping force in the injection filling process is applied to the resin 31, whereby the mold opening / closing servomotor 7 is moved in the mold closing direction. As a result, the toggle link mechanism 13 is shifted to a fully extended state or a state close thereto, and the movable side mold 6 mounted on the movable die plate 5 is finally driven. 1 advances (lowers) by a minute amount from the state of FIG. 1, and the volume of the cavity 14 is reduced compared to the state of FIG. As a result, a large compressive force is applied to the resin 31 that has started to solidify in the cavity 14, and the resin 31 that contracts by solidification / cooling has a smooth surface without sink marks and a homogeneous density distribution without strain. As a transparent window plate with the desired thickness and no weld line, it is manufactured with high quality. In this compression process, a known holding pressure is applied by the injection units 21, 22, and 23 via a resin pressure. FIG. 2 shows the state of the compression process as described above.

  After the compression step, after a cooling period, the mold is opened and the molded product is taken out by the robot.

  FIG. 5 is an explanatory diagram showing the control system and mechanism configuration of each of the injection units 21, 22, and 23 described above, and the control system and functional configuration of the mold closing / compression / mold opening described above. The same reference numerals are given to the constituent elements described above. In FIG. 5, portions corresponding to the first, second, and third injection units 21, 22, and 23 are each surrounded by a two-dot chain line.

  In FIG. 5, reference numeral 41 denotes a system controller that controls the entire machine (injection molding machine). The system controller 41 includes various application programs created and deployed in advance, and various sensors provided in each part of the machine. Various control systems of the machine are controlled based on measurement information from the position sensor, pressure sensor, safety confirmation sensor, etc., state confirmation information from various control systems of the machine, timekeeping information, and the like.

  Reference numeral 51 denotes a screw of the first injection unit 21, and the screw 51 is disposed in a heating cylinder (not shown) of the first injection unit 21 so as to be able to rotate and move forward and backward. The screw 51 receives the rotation of a measuring servo motor 53 driven and controlled via a servo driver 52 based on a command from the system controller 41 via a rotation transmission mechanism 54 composed of a pulley / timing belt. And is driven to rotate. In addition, the screw 51 transmits the rotation of the injection servo motor 56, which is driven and controlled via the servo driver 55, based on a command from the system controller 41 via a rotation transmission mechanism 57 including a pulley / timing belt. The ball screw mechanism 58 is linearly driven by converting rotation into linear motion.

  Reference numeral 61 denotes a screw of the second injection unit 22, and the screw 61 is disposed in a heating cylinder (not shown) of the second injection unit 22 so as to be able to rotate and move forward and backward. The screw 61 transmits the rotation of the metering servo motor 63 that is driven and controlled via the servo driver 62 based on a command from the system controller 41 via a rotation transmission mechanism 64 including a pulley / timing belt. And is driven to rotate. Further, the screw 61 transmits the rotation of the injection servo motor 66 driven and controlled via the servo driver 65 based on a command from the system controller 41 via a rotation transmission mechanism 67 including a pulley / timing belt. The ball screw mechanism 68 is linearly driven by converting rotation into linear motion.

  Reference numeral 71 denotes a screw of the third injection unit 23, and the screw 71 is disposed in a heating cylinder (not shown) of the third injection unit 23 so as to be able to rotate and move forward and backward. The screw 71 receives the rotation of a measuring servo motor 73 driven and controlled via a servo driver 72 based on a command from the system controller 41 via a rotation transmission mechanism 74 including a pulley / timing belt. And is driven to rotate. The screw 71 transmits the rotation of the injection servo motor 76 driven and controlled via the servo driver 75 based on a command from the system controller 41 via a rotation transmission mechanism 77 including a pulley / timing belt. The ball screw mechanism 78 is linearly driven by converting rotation into linear motion.

  81 is a servo driver that drives and controls the mold opening / closing servomotor 7 based on a command from the system controller 41, and 82 is a drive pulley 8 that transmits the rotation of the mold opening / closing servomotor 7 to the ball screw mechanism. And a rotation transmission mechanism including a timing belt (not shown) and a driven pulley 12.

  In the configuration shown in FIG. 5, the system controller 41 performs the weighing operation, the injection filling operation with a time difference, the pressure holding operation, and the mold closing operation by appropriately driving each servo driver. Perform compression and mold opening operations.

  In the injection filling operation with the time difference described above, the setting of the injection filling start timing of the injection unit in the second stage, the third stage,... Is performed by simulation using a computer system corresponding to the shape of the cavity, and a test. Confirmation by shots and retry settings are required, but once optimal conditions are set, automobile window plates of any size and shape (planar shape and curved shape) can be produced in large quantities with high productivity.

  In addition, the number of injection units used for the injection filling operation with a time difference is arbitrary, and the number of injection units used in the second stage, the third stage,...

It is explanatory drawing which shows the mechanism structure of the principal part before injection filling in the injection molding machine which concerns on one Embodiment of this invention. It is explanatory drawing which shows the mechanism structure of the principal part of a compression state in the injection molding machine which concerns on one Embodiment of this invention. It is explanatory drawing which shows typically the mode of injection filling in the injection molding machine which concerns on one Embodiment of this invention. It is typical explanatory drawing of the direction orthogonal to FIG. It is explanatory drawing which blocks and shows the control system and mechanism structure of the principal part in the injection molding machine which concerns on one Embodiment of this invention. It is explanatory drawing which shows typically the mode of the injection filling by a prior art.

Explanation of symbols

1 Fixed die plate 2 Fixed mold (lower mold)
3 Tailstock 4 Tie bar 5 Movable die plate 6 Movable side mold (upper mold)
7 Servo motor for mold opening / closing 8 Drive pulley 9 Ball screw mechanism 10 Nut body 11 Screw shaft 12 Driven pulley 13 Toggle link mechanism 14 Cavity 21 First injection unit 22 Second injection unit 23 Third injection unit 31 Resin 41 System controller 51 Screw ( Screw of the first injection unit)
52 Servo Driver 53 Servo Motor for Metering 54 Rotation Transmission Mechanism 55 Servo Driver 56 Servo Motor for Injection 57 Rotation Transmission Mechanism 58 Ball Screw Mechanism 61 Screw (Screw of the Second Injection Unit)
62 Servo Driver 63 Servo Motor for Weighing 64 Rotation Transmission Mechanism 65 Servo Driver 66 Servo Motor for Injection 67 Rotation Transmission Mechanism 68 Ball Screw Mechanism 71 Screw (3rd Injection Unit Screw)
72 Servo Driver 73 Servo Motor for Weighing 74 Rotation Transmission Mechanism 75 Servo Driver 76 Servo Motor for Injection 77 Rotation Transmission Mechanism 78 Ball Screw Mechanism 81 Servo Driver 82 Rotation Transmission Mechanism

Claims (6)

An injection molding machine including a plurality of injection units that perform injection filling of the same resin material into one cavity of a mold,
By giving a time difference to the timing of starting injection and filling of the molten resin into the cavity by the plurality of injection units, the resin by the injection unit that has started injection and filling first proceeds in the cavity, and starts injection and filling after this. The plurality of injection units are configured to start injection filling by the injection unit that starts injection filling next after the resin by the injection unit passes through the injection portion by the injection unit that starts injection filling next. An injection molding machine comprising a controller for controlling the operation. The injection molding machine according to claim 1,
An injection molding machine characterized in that the injection unit that starts injection filling later performs injection filling by breaking through the skin layer of the resin that has been previously injected and filled. The injection molding machine according to claim 1,
The controller controls the mold opening and closing device so as to apply a compressive force to the resin in the cavity after the injection filling by the plurality of injection units is completed. In the injection molding machine according to any one of claims 1 to 3,
An injection molding machine characterized in that a molded product to be molded is a transparent large-area thin plate having no weld line. A method for controlling an injection molding machine comprising a plurality of injection units for performing injection filling of the same resin material into one cavity of a mold,
By giving a time difference to the timing of starting injection and filling of the molten resin into the cavity by the plurality of injection units, the resin by the injection unit that has started injection and filling first proceeds in the cavity, and starts injection and filling after this. An injection molding machine that starts injection filling by the injection unit that starts injection filling next after the resin by the injection unit passes through the injection portion by the injection unit that starts injection filling next Control method. In the control method of the injection molding machine according to claim 5,
A method for controlling an injection molding machine, wherein a molded product to be molded is a transparent large-area thin plate without a weld line.

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