JP4065160B2 - Injection molding machine and optical disk substrate manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a horizontal type injection molding machine and a method of manufacturing an optical disk substrate using the same, and in particular, it is possible to reduce as much as possible a variation in mold clamping force with respect to a molded product such as a disk in a mold. Related technology.
[0002]
[Prior art]
The mainstream of injection molding machines is a horizontal type, and a mold clamping unit in the horizontal type injection molding machine generally has a configuration as shown in FIG.
[0003]
In FIG. 6, 51 is a first die plate which is a fixed die plate on which a fixed mold 52 is mounted, 53 is an end plate which is a holding plate on which a mold opening / closing drive source (not shown) is mounted, and 54 is a first die plate. The four tie bars 55, which are bridged between the four corners of the die plate 51 and the four corners of the end plate 53 and whose both ends are fixed to the first die plate 51 and the end plate 53 with nuts, are movable. A second die plate which is a movable die plate mounted with a side mold 56 and which can be moved back and forth by inserting and guiding four corners of the tie bar 54, 58 is a base plate on which an injection unit and a mold clamping unit are mounted, 59 Is the resin injected into the mold. Servo motors and hydraulic cylinders are used as the mold opening / closing drive source (not shown). In the case of a direct pressure type clamping unit, the piston of the hydraulic cylinder and the linear drive part of the ball screw mechanism that converts the rotation of the servo motor into linear motion In the case of a toggle type clamping unit, the second die plate 55 is moved forward and backward by a piston of a hydraulic cylinder or a linear drive unit of a ball screw mechanism that converts rotation of a servo motor into linear motion. The second die plate 55 is moved forward and backward through the toggle link mechanism by driving the crosshead of the toggle link mechanism forward and backward. FIG. 6 shows a toggle type, and 57 is a toggle link mechanism.
[0004]
In the configuration shown in FIG. 6, the lower end side of the first die plate 51 is fixed on the base plate 58, and the end plate 53 can be moved horizontally on the base plate 58 for well-known die height adjustment. It is arranged like this.
[0005]
In the configuration shown in FIG. 6, when a servo motor which is a mold opening / closing drive source (not shown) is rotationally driven in a predetermined direction, this rotation is converted into a linear motion by a ball screw mechanism (not shown). Is transmitted to the cross head of the toggle link mechanism 57, whereby the second die plate 55 is driven forward toward the first die plate 51 via the toggle link mechanism 57. When the mold clamping completion position is reached, the toggle link mechanism 57 is stretched to generate a large mold clamping force.
[0006]
By the way, in the mold clamping state, reaction forces due to the four tie bars 54 being stretched by the mold clamping force are applied to the four corners of the first die plate 51. In the configuration shown in FIG. Since the lower end side of the die plate 51 is fixed on the base plate 58, the upper side of the first die plate 51 is greatly bent as compared with the lower side thereof, as shown in FIG. When the molded product to be molded is, for example, an optical disk substrate, there is a problem that the plate thickness accuracy is adversely affected.
[0007]
That is, when the optical disk substrate is molded using a mold clamping unit as shown in FIG. 6, the upper side deflection amount of the first die plate 51 is larger than that on the lower side, so that the resin 59 ( The clamping force (compressive stress) is different between the upper side and the lower side of the optical disk substrate), which causes variations in the thickness distribution of the optical disk substrate. In FIG. 5, the points plotted with black circles are the plate thicknesses of the outer periphery 8 points of the optical disc substrate (eight points at 45 degree intervals at the same radius) when the optical disc substrate is molded using the mold clamping unit of FIG. The lower plate thickness in the mold is larger than the upper plate thickness in the mold, resulting in variations in the plate thickness distribution. Such variation in plate thickness is a serious problem that cannot be ignored in high-density recording next-generation optical discs and the like that require severe plate thickness accuracy.
[0008]
FIG. 7 is a diagram showing another conventional configuration of a mold clamping unit in a horizontal type injection molding machine. Components equivalent to those in FIG. 6 are denoted by the same reference numerals. In the configuration shown in FIG. 7, the lower end side of the end plate 53 is fixed on the base plate 58, and the first die plate 51 is disposed so as to be horizontally movable on the base plate 58. A mold clamping unit having a configuration is disclosed in Japanese Patent Publication No. 6-45163 and Japanese Patent Laid-Open No. 9-225979.
[0009]
In the configuration shown in FIG. 7, in the mold clamping state, reaction forces due to the four tie bars 54 being stretched by the mold clamping force are applied to the four corners of the end plate 53, but in the configuration shown in FIG. Since the lower end side of the plate 53 is fixed on the base plate 58, the upper side of the end plate 53 is greatly bent as compared with the lower side as shown in FIG. Then, as shown in an exaggerated manner by a two-dot chain line, the upper side of the first die plate 51 bends greatly (bends in the direction opposite to that in FIG. 6) compared to the lower side thereof, similarly to the conventional configuration of FIG. There was a problem of adversely affecting the plate thickness accuracy.
[0010]
[Problems to be solved by the invention]
As described above, in the mold clamping unit in the conventional horizontal type injection molding machine, since the lower end side of the first die plate or the lower end side of the end plate is fixed on the base plate, the mold clamping state Due to the difference in the amount of vertical deflection of the first die plate, the thickness distribution varies in the upper and lower parts of the mold, and this is a problem that cannot be ignored in next-generation optical discs that require severe plate thickness accuracy. Become.
[0011]
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 suppress variations in thickness distribution of molded products such as optical disk substrates as much as possible.
[0012]
[Means for Solving the Problems]
In order to achieve the above-described object, in a typical invention according to the present invention, in a horizontal type injection molding machine having an injection unit and a clamping unit, a plurality of tie bars arranged in parallel to a base plate. At least one of the first tie bar and the plurality of tie bars are arranged in order of the first die plate, the second die plate, and the end plate from the injection unit side. Each of the second die plates is mounted with a mold, and a mold opening / closing mechanism that achieves a mold opening / closing operation is provided between the second die plate and the end plate . so as to horizontally move the die plate between said first die plate and said end plate, said first die plate and said end plate, during the molding Depending on the bending amount of change of the first die plate and the end plate with the molding operation, movably configured horizontally along the rails on the base plate.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
1 to 4 relate to an embodiment of the present invention. FIG. 1 is a front view of a horizontal type injection molding machine according to the present embodiment, with a part of the configuration omitted and partially cut. FIG. 1 is a plan view of a horizontal type injection molding machine according to the present embodiment, with a part of the configuration omitted and partially cut, and in FIG. 1 and FIG. (Mold opening / closing unit), which is generally indicated by reference numeral B is an injection unit.
[0015]
In the mold clamping unit A, 1 is a first die plate that is a fixed die plate on which a fixed mold 2 is mounted, and 3 is a holding plate on which a mold opening / closing drive source (here, a mold opening / closing servomotor) is mounted. The end plate 4 is spanned between the four corners of the first die plate 1 and the four corners of the end plate 3, and both ends thereof are fastened to the first die plate 1 and the end plate 3 with nuts, respectively. The four fixed tie bars 5 are mounted on the movable die 6 and the second die plate 7 is a movable die plate that can be moved forward and backward by inserting and guiding the four corners of the tie bar 4. A toggle screw that is driven to extend or fold by a ball screw mechanism (not shown) that converts the rotation of a servo motor (not shown) for mold opening / closing into a linear motion, thereby moving the second die plate 5 forward and backward. Click mechanism 8 is baseplate injected resin into the mold, 9 in which the mold clamping unit A and the injection unit B is mounted. Although an example of a toggle type clamping unit has been shown here, a direct pressure type clamping unit can also be adopted. In this case, a piston of a hydraulic cylinder, a linear drive unit of a linear servo motor, The second die plate 5 is moved forward and backward by a linear drive unit of a ball screw mechanism that converts the rotation of the servo motor into a linear motion.
[0016]
In the present embodiment, the first die plate 1 and the end plate 3 are disposed on the base plate 9 so as to be horizontally movable in the left-right direction of FIG. 1 along, for example, a rail (not shown). That is, in this embodiment, the whole mold clamping unit A is horizontally movable on the base plate 9, and the end surface of the tie bar 4 on the end plate 3 side is engaged with the locking block 10 fixed on the base plate 9. By stopping, the clamping unit A is regulated (positioned). That is, as will be described later, the mold clamping unit A is pressed on the periphery of the resin injection hole 2a of the fixed mold 2 by the nozzle at the tip of the heating cylinder of the injection unit B. Since one end is fixed to the first die plate 1, no force is generated to press the clamping unit A against the locking block 10. Therefore, the locking block 10 on the base plate 9 is 1 is provided for the purpose of restricting the position of the mold clamping unit A so that the mold clamping unit A does not escape in the left-right direction in FIG. 1. It is comprised so that it may latch with respect to 9. Although not shown, it is desirable that the end face of the tie bar 4 be locked with screws by bolts provided on the locking block 10, so that the tie bar 4 is attached to the base plate 9. It can be prevented from moving to the left and right, and a fine position adjustment is also possible. Needless to say, even if the end face of the tie bar 4 is locked with screws, the first die plate 1 and the end plate 3 can be moved horizontally in the left-right direction according to the amount of bending.
[0017]
Further, in the injection unit B of FIG. 1, 11 is an injection unit base member that is disposed on the base plate 9 so as to be horizontally movable in the left-right direction of FIG. Is a front holding plate fixed on the injection unit base member 11, 13 is a rear holding plate fixed on the injection unit base member 11, 14... Are a front holding plate 12 and a rear holding plate 13. The guide bar 15 is bridged between the front holding plate 12 and the rear holding plate 13, and both ends thereof are held and fixed to the front holding plate 12 and banded on the outer periphery. A heating cylinder around which the heater 16 is wound, 17 is a nozzle attached and fixed to the tip of the heating cylinder 15, and 18 can rotate and move forward and backward in the heating cylinder 15 It is disposed a screw as it is.
[0018]
As shown in FIG. 1, a moving body 19 is inserted and arranged in the guide bar 14, and the moving body 19 can move forward and backward along the guide bar 14. A rotating body 20 that integrally couples the rear end of the screw 18 is rotatably held on the moving body 19, and a pulley 21 is fixed to the rotating body 20. The pulley 21 is adapted to transmit the rotation of a measuring servo motor (not shown) mounted on the moving body 19. Then, when the metering servo motor (not shown) is rotationally driven in a predetermined direction, the pulley 21, the rotating body 20, and the screw 18 are rotated together, and thereby supplied to the rear end side of the screw 18. The resin material thus obtained is fed to the front side of the screw 18 while being kneaded and plasticized, and the screw 18 is moved back together with the moving body 19 and when one shot of molten resin is stored on the front side of the screw 18. The rotation of a measuring servo motor (not shown) is stopped.
[0019]
As shown in FIG. 1, a screw shaft 23 of a ball screw mechanism 22 is rotatably held on the rear holding plate 13 via a bearing 25, and a pulley 26 is attached to an end of the screw shaft 23. It is fixed. The end of the nut body 24 of the ball screw mechanism screwed to the screw shaft 23 is fixed to the moving body 19. The pulley 26 at the end of the screw shaft 22 is adapted to transmit the rotation of an injection servo motor 27 (FIG. 2) mounted on the rear holding plate 13, and when the pulley 26 is driven to rotate. The screw shaft 23 integrated therewith is rotated, and this rotational force is converted into a linear moving force by the nut body 24 and transmitted to the moving body 19, whereby the moving body 19 is driven forward or backward. . That is, during the injection stroke, the screw 18 is driven forward by the injection servo motor 27 via the pulley 26, the ball screw mechanism 22 and the moving body 19, and during the metering stroke, the pulley 26 and the ball screw mechanism 22 are driven by the injection servo motor 27. The back pressure of the screw is controlled via the moving body 19.
[0020]
As shown in FIG. 2, a nozzle touch servomotor 28 is mounted on the front holding plate 12, and nut bodies 29 and 29 are rotatably held. The rotation is transmitted to the nut bodies 29 and 29. In FIG. 2, 30 and 30 are nozzle touch control bars whose ends are fixed to the first die plate 1 during the molding operation, and a nut body 29 is screwed into the threaded portion 30 a of the nozzle touch control bar 30. ing. Then, the nut body 29 is rotated by rotationally driving the nozzle touch servomotor 28, and the front holding plate 12, that is, the entire injection unit B is moved forward and backward along the nozzle touch control bar 30 together with the nut body 29. It has become.
[0021]
By such a nozzle touch control mechanism, in the molding operation state, the nozzle 17 at the tip of the heating cylinder 15 of the injection unit B is fixed to the fixed mold of the mold clamping unit A by the nozzle touch servomotor 28 that is pressure feedback controlled. The peripheral portion of the second resin injection hole 2a is pressed. As described above, the clamping unit A does not move in the left-right direction in FIG. 2 by locking the end surface of the tie bar 4 on the end plate 3 side to the locking block 10. The position is regulated.
[0022]
In FIG. 2, 31 is a nozzle touch control unit that controls nozzle touch based on a command from a host controller (not shown), and 32 is a servo motor for nozzle touch based on a command from the nozzle touch control unit 31. This is a servo amplifier that drives 28 by feedback control. The servo amplifier 32 includes a control command value from the nozzle touch control unit 31, a position actual value (velocity actual value) S1 obtained from an encoder (not shown) provided in the nozzle touch servomotor 28, and a nozzle touch servomotor. Referring to an actual torque value S2 obtained from a drive current value sensor means (not shown) provided at 28, in the molding operation state, the nozzle touch servo is set so that the actual torque value S2 coincides with a predetermined set torque value. The motor 28 is driven and controlled by pressure feedback control.
[0023]
In this way, during the molding operation, the nozzle touch servo motor 28 is driven by pressure feedback control, so that the mold clamping, such as whether the mold is open or clamped, regardless of the tie bar elongation amount. (Regardless of the state of the unit A), always around the resin injection hole 2a of the fixed mold 2 of the clamping unit A by the nozzle 17 at the tip of the heating cylinder 15 of the injection unit B at a constant pressure. Can be pressed.
[0024]
FIG. 3 is a schematic diagram of the mold clamping unit A in the mold clamping state. In the mold clamping state, reaction forces due to the four tie bars 4 being stretched by the mold clamping force are applied to the four corners of the first die plate 1 and the end plate 3. Since the lower end sides of the die plate 1 and the end plate 3 are both free with respect to the base plate 9, the first die plate 1 and the end plate 3 are exaggerated with a two-dot chain line in FIG. The upper side and the lower side are bent in substantially the same manner. That is, in this embodiment, in the mold clamping state, each of the first die plate 1 and the end plate 3 is bent outwardly and the bending is substantially uniform in a circumferential shape. FIG. 4 is a diagram comparing the amount of bending of the first die plate during mold clamping between the present embodiment and the conventional example shown in FIG. 6, and as indicated by white squares, as shown in FIG. In the conventional example, the amount of bending of the upper portion of the first die plate is about 55 μm, whereas in the present embodiment shown by the white circle, the amount of bending of the first die plate is equal in the vertical direction and is about 27 μm. It was.
[0025]
As a result, the mold clamping force (compressive stress) is substantially uniform between the upper side and the lower side of the disk-shaped resin 8 (optical disk substrate) in the mold. In FIG. 5, the points plotted with black squares are the plate thicknesses of the outer periphery 8 points of the optical disc substrate (eight points at 45 degree intervals at the same radial position) when the optical disc substrate is molded by the injection molding machine of this embodiment. The measurement result is shown. As is clear from FIG. 5, it was confirmed that the optical disk substrate molded in this embodiment has almost no variation in the upper and lower sides in the mold and can suppress the variation in the plate thickness in all directions as much as possible.
[0026]
Furthermore, according to experiments, as a result of producing an optical disk substrate having a plate thickness of 0.8 mm or less using PMMA resin or PC resin, the thickness unevenness in the circumferential direction of the optical disk substrate can easily be achieved to 15 μm or less (actual As shown in FIG. 5, all are several μm or less), birefringence is 60 nm or less, T-skew (tangent skew) is 0.15 eg or less, and eccentricity is 70 μm or less. It was confirmed. Therefore, it was confirmed that next-generation optical discs and the like that require severe plate thickness accuracy can be molded with high quality.
[0027]
The optical disk substrate is molded by a mold clamping process, an injection process for injecting and injecting a molten resin into the cavity space of the molding die, a pressure holding and cooling process, and a mold opening process. In the injection process, the mold clamping pressure is set to be lower than the resin pressure when the cavity space is filled with molten resin, and this setting temporarily allows the movable mold to retreat, and then holds and cools. In the process, the optical disc substrate is molded by using a clamping pressure that resists the resin pressure.
[0028]
【The invention's effect】
As described above, according to the present invention, in a horizontal injection molding machine and an optical disk substrate manufacturing method using the same, it is possible to suppress variations in the thickness distribution of molded products such as an optical disk substrate as much as possible. It becomes possible.
[Brief description of the drawings]
FIG. 1 is a front view of an injection molding machine according to an embodiment of the present invention, with some components omitted and partially cut.
FIG. 2 is a plan view of the injection molding machine according to the embodiment of the present invention, with some components omitted and partially cut.
FIG. 3 is a schematic view of a mold clamping unit of an injection molding machine according to an embodiment of the present invention.
FIG. 4 is an explanatory view showing the amount of bending of a first die plate during mold clamping in an injection molding machine according to an embodiment of the present invention and an injection molding machine according to the prior art.
FIG. 5 is an explanatory view showing a comparison of plate thickness distributions of an optical disk substrate molded by an injection molding machine according to an embodiment of the present invention and an injection molding machine according to the prior art.
FIG. 6 is a schematic view of a mold clamping unit of an injection molding machine according to a first prior art.
FIG. 7 is a schematic view of a mold clamping unit of an injection molding machine according to a second prior art.
[Explanation of symbols]
A Clamping unit (mold opening / closing unit)
B Injection unit 1 First die plate (fixed die plate)
2 Fixed mold 2a Resin injection hole 3 End plate (holding plate)
4 Tie bar 5 Second die plate (movable die plate)
6 Movable mold 7 Toggle link mechanism 8 Resin 9 Base plate 10 Locking block 11 Injection unit base member 12 Front holding plate 13 Rear holding plate 14 Guide bar 15 Heating cylinder 16 Band heater 17 Nozzle 18 Screw 19 Moving body 20 Rotating body 21 Pulley 22 Ball screw mechanism 23 Screw shaft 24 Nut body 25 Bearing 26 Pulley 27 Injection servo motor 28 Nozzle touch servo motor 29 Nut body 30 Nozzle touch control bar 30a Screw portion 31 Nozzle touch control portion 32 Servo amplifier

Claims (8)

In a horizontal type injection molding machine with an injection unit and a clamping unit,
Locking at least one of a plurality of tie bars arranged parallel to the base plate to the base plate;
The plurality of tie bars are arranged in the order of the first die plate, the second die plate, and the end plate from the injection unit side,
Each of the first and second die plates has a mold, and includes a mold opening / closing mechanism that achieves a mold opening / closing operation between the second die plate and the end plate . Moving the second die plate horizontally between the first die plate and the end plate;
The first die plate and the end plate are horizontally aligned with the rails on the base plate according to a change in the amount of deflection of the first die plate and the end plate during the molding operation during molding. An injection molding machine characterized by being configured to be movable. The injection molding machine according to claim 1, wherein
An injection molding machine characterized in that the whole mold clamping unit is positioned by locking the tie bar with respect to the base plate by a locking portion provided on the base plate. The injection molding machine according to claim 1 or 2,
When the first die plate, the second die plate, and the end plate are all movable in the horizontal direction on the base plate, the mold opening / closing mechanism is driven to achieve the mold opening / closing operation. An injection molding machine characterized in that the first die plate and the end plate are bent outwardly so that the bending is substantially uniform in a circumferential shape. In the injection molding machine according to any one of claims 1 to 3,
An injection molding machine characterized in that the nozzle is pressed with a predetermined pressure around the resin injection port of the mold clamping unit by performing pressure feedback control of a nozzle touch servomotor of the injection unit. A horizontal type injection molding machine for molding an optical disk substrate,
Equipped with an injection unit and mold clamping unit on the base plate,
The mold clamping unit is arranged in the order of a first die plate, a second die plate, and an end plate from the injection unit side, and a plurality of tie bars arranged in parallel to the base plate; A drive source that moves the two die plates back and forth horizontally between the first die plate and the end plate ;
At least one tie bar is connected and positioned with respect to the base plate,
The first die plate and the end plate are horizontally aligned with the rails on the base plate according to a change in the amount of deflection of the first die plate and the end plate during the molding operation during molding. An injection molding machine characterized by being configured to be movable. Using the injection molding machine according to any one of claims 1 to 5 ,
Mold clamping step and the injection step of injecting injecting molten resin into a cavity of the forming metal mold, pressure-holding and cooling step, the mold opening process, the manufacturing method of the optical disk substrate, which comprises forming by. The manufacturing method according to claim 6,
Wherein in the injection step, mold clamping pressure is lower than set the resin pressure when the molten resin is filled in the cavity space, allowing the temporary retraction of the variable Dokin type by the setting, then the pressure-holding And in the cooling step, the optical disk substrate is manufactured by forming a mold clamping pressure against the resin pressure. The manufacturing method according to claim 6,
The method of manufacturing an optical disk substrate, wherein the optical disk substrate is a nominal 0.6 mm thin substrate, and is made of PMMA resin or PC resin.

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