JP4275652B2 - Measuring method of injection molding machine for disk substrate molding - Google Patents

Description

  The present invention relates to a measuring method for an injection molding machine for forming a disk substrate.

  Conventionally, the molding cycle time of a disk substrate molding injection molding machine having a signal surface such as a CD-ROM, CR-R, DVD-ROM, DVD-R, DVD-RW, etc. is about 3.0 to 6.0 seconds. In many cases, the number of screw rotations in the measuring process was about 200 rpm. Further, in the conventional injection molding machine for forming a disk substrate, those described in Patent Document 1 and Patent Document 2 are known as those having a relatively high screw rotation speed. In both Patent Document 1 and Patent Document 2, molding is performed with the screw rotation speed during measurement set at 360 rpm. However, at this screw rotation speed, the time of the metering process cannot be shortened, and it has been difficult to cope with molding in which the molding cycle time is shorter than 2.8 seconds.

  In order to measure a certain amount in a shorter time, it is conceivable to increase the screw diameter and increase the amount of molten resin delivered per rotation. However, such a method increases the overall size of the injection apparatus, leading to an increase in cost. Therefore, it can be considered that the screw currently used is not changed and the screw rotation is made high. However, if the screw rotation is high, the state of the resin after weighing may become unstable due to air entrainment, etc., and there may be defects such as silver in the molded product, and the above defects vary depending on the type of resin. Making the number as high as possible does not solve the problem. Further, there is a problem that the screw retreat completion position becomes unstable as the screw rotation is further increased.

JP 2003-201396 A (0088) JP 11-300842 A (0022)

  The present invention has been proposed in order to solve the above-described problems in the prior art, and for a disc that can reduce the measuring time in order to shorten the molding cycle time of the injection molding machine for molding a disc substrate. It aims at providing the measuring method of a molding machine. It is another object of the present invention to provide a weighing method that does not cause defects such as silver in the molded article, and sink or overfill caused by unstable measurement position. Furthermore, it aims at providing the measuring method which can achieve said objective, without enlarging an injection apparatus.

According to a first aspect of the present invention, there is provided a metering method for an injection molding machine for molding a disk substrate, wherein a screw in a heating cylinder is rotated by a screw rotation motor, and the screw is moved backward while supplying polycarbonate resin to the front of the screw. In the measuring method of the injection molding machine for substrate molding, the set temperature of the heating cylinder corresponding to the compression zone and the metering zone of the screw is set to 300 ° C. to 390 ° C., and 0.30 second to 0.55 second. In the meantime, the screw rotation speed is controlled at a constant speed of 400 rpm to 550 rpm, and the screw rotation speed reduction control obtained using the set value or the measured value of the screw rotation speed at the time of the screw rotation speed constant speed control is performed. From the switching position, the screw speed is reduced so that the speed becomes 0 in 0.15 to 0.35 seconds. Control is performed.

  The measuring method of the disk substrate molding injection molding machine according to claim 2 of the present invention is the metering method according to claim 1, wherein the molding cycle time from the start of the measuring process to the start of the next measuring process is 1.5 seconds to 2.8 seconds. It is characterized by being.

According to a third aspect of the present invention, there is provided a metering method for an injection molding machine for forming a disk substrate according to the first or second aspect, wherein 0.05 second to 0.00 second after reaching a preset screw retreat completion position. The screw rotation speed reduction control is performed so that the screw rotation speed becomes 0 in 25 seconds .

According to a fourth aspect of the present invention, there is provided a metering method for an injection molding machine for molding a disk substrate according to any one of the first to third aspects, wherein the screw rotation speed reduction control is appropriately selected from a plurality of deceleration patterns. It is characterized by selecting and setting an appropriate deceleration pattern .

In the measuring method of the injection molding machine for disk substrate molding using polycarbonate resin, the present invention sets the set temperature of the portion of the heating cylinder corresponding to the compression zone and the metering zone of the screw to 300 ° C. to 390 ° C., The screw speed is controlled at a constant speed of 400 rpm to 550 rpm for 0.30 seconds to 0.55 seconds, and is obtained using a set value or an actual measurement value of the screw speed at the time of constant speed control of the screw speed. Prevents the occurrence of defective products such as silver streak by performing screw rotation speed reduction control so that the rotation speed becomes 0 in 0.15 to 0.35 seconds from the switching position to the screw rotation speed reduction control. However, the cycle can be shortened.

In the third aspect of the present invention, the screw rotation speed reduction control is performed so that the screw rotation speed becomes 0 in 0.05 seconds to 0.25 seconds after reaching a preset screw retreat completion position. As a result, the screw back pressure after the completion of the measurement can be changed with a desired curve, and the occurrence of defective products can be prevented.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional view showing an outline of a main part of an injection molding machine for molding a disk substrate according to an embodiment. FIG. 2 is a graph showing changes in screw position, screw rotation speed, and screw back pressure in the measuring step of the embodiment. FIG. 3 is a flowchart illustrating the weighing method according to the embodiment.

  A disk substrate molding injection molding machine 1 includes a mold clamping device (not shown) that contacts and separates or presses an injection device 2 and a disk substrate molding die 3 filled with a molten resin 7 injected from the injection device 2. ), A control device 4 for controlling the injection device 2 and the mold clamping device, and a temperature controller for the disk substrate molding die 3 (not shown). The disk substrate molding die 3 is provided with a cavity 8 having a variable volume so that the injection filled resin 7 can be compressed. In the disk substrate molding die 3, a stamper (not shown) is disposed on the mirror plate of at least one disk substrate molding die 3 so that a signal or the like is transferred to the disk substrate molded in the cavity 8. It has become. Further, a plurality of cooling medium flow paths are formed on the mirror plate for the purpose of improving the cooling rate, and the intervals between the cooling medium flow paths are close. The cooling medium flow path is connected to the temperature controller.

  The injection device 2 includes a heating cylinder 6 to which a nozzle 5 that is brought into contact with and pressed against a sprue of the disk substrate molding die 3 is attached. A band heater 9 is attached to the nozzle 5 and the heating cylinder 6 for each zone, and temperature control is possible independently. A screw 10 is fitted into the center inner hole of the heating cylinder 6 so as to be rotatable and reciprocally movable in the axial direction. A rear portion of the heating cylinder 6 is fixed to the housing 11, and an injection servo motor 12 as an injection actuator is fixed to both ends of the housing 11. A shaft portion at the rear end of the screw 10 fitted into the central inner hole of the heating cylinder 6 so as to freely rotate and reciprocate is pivotally supported by a movable platen 13 provided in parallel with the housing 11 and provided on the movable platen 13. The pressure received by the screw 10 by the load cell 14 is detected.

  A screw rotating servo motor 15 as a screw rotating motor is attached to the side of the movable platen 13 opposite to the heating cylinder, and a shaft portion at the rear end of the screw 10 is connected to a rotating shaft of the screw rotating servo motor 15. . Ball nuts 16 are fixed to both ends of the movable platen 13, and the ball nuts 16 are screwed into ball screws 17 connected to the rotation shaft of the injection servomotor 12. With this structure, the injection device 2 can move the movable plate 13 back and forth through the ball screw 17 and the ball nut 16 by the rotation of the injection servo motor 12, and the screw 10 in the heating cylinder 6 can reciprocate in the axial direction. It has become.

  The screw 10 used in the present embodiment has a screw-like flight, and includes a feed zone 10a, a compression zone 10b, and a metering zone 10c in order from the rear. In the compression zone, the thickness of the shaft core is gradually increased, and at the same time, the depth of the groove formed by the flight is reduced. A backflow prevention valve 10 d is provided at the tip of the screw 10. The diameter of the screw 10 of this embodiment is 28 mm. In the case where one disk substrate for DVD is formed by one injection filling into the disk substrate molding die 3, a screw having a diameter of 24 mm to 30 mm is preferably used. Further, when two DVD disk substrates are molded by one injection filling into a disk substrate molding die, those having a relatively large screw diameter of 30 mm or more are used. In the present embodiment, the rotation shaft of the screw rotation servomotor 15 and the shaft portion of the rear end of the screw 10 are directly connected, but a belt and a pulley may be used to transmit the rotational drive of the motor. The ratio of the pulley on the motor side and the pulley on the screw side is not limited to 1: 1. Furthermore, the configuration of the injection device 2 may be another arrangement.

  The control device 4 is a sequence control of the mold clamping device and the injection device 2 in the disk substrate molding injection molding machine 1, speed control, pressure control, or positioning of actuators such as the injection servo motor 12 and screw rotation servo motor 15. Control, temperature control of the band heater 9 etc. for heating the heating cylinder 6 and the like are executed by closed loop control. This control device 4 has a known configuration based on a microprocessor, and includes a display unit composed of a liquid crystal display, a setting unit composed of a touch panel provided on the surface of the display unit, a RAM / ROM, and setting values and control programs. A storage unit is included. Further, to a rotary encoder 12a for detecting the rotation angle of the injection servo motor 12, a rotary encoder 15a for detecting the rotation angle of the screw rotation servo motor 15, and an input unit and an actuator for inputting signals from various sensors such as the load cell 14. An output unit for outputting a signal; The control device 4 also includes servo amplifiers for an injection servo motor 12 and a screw rotation servo motor 15. As for the rotary encoder 12a, the position of the screw 10 may be detected by a position sensor separately attached to the movable platen 13.

  Next, an outline of the weighing process of the disk substrate molding injection molding machine 1 will be described. The polycarbonate resin pellets for molding the disk substrate supplied into the heating cylinder 6 through a resin charging hole (not shown) provided on the upper surface of the housing 11 is rotated by the screw 10 when the screw 10 is rotated. Along with this, it is transferred forward. Meanwhile, the polycarbonate resin pellets are plasticized and melted by heat from the heating cylinder 6 heated by the band heater 9 and frictional heat generated by the resin itself being rubbed against the screw 10 and the inner wall of the heating cylinder 6, and While being kneaded by the screw 10, it is sent to the front of the screw 10 and accumulated as a molten resin 7 in the central inner hole of the heating cylinder 6. At that time, the pressure increase of the molten resin 7 becomes a screw back pressure, and a screw back pressure that pushes the screw 10 backward is generated. The screw back pressure is controlled to be a predetermined value mainly by the injection servo motor 12.

  As an example, the temperature of the heating cylinder 6 in this embodiment is 340 ° C. for the nozzle 5, 350 ° C. for the heating cylinder front part and the heating cylinder middle part corresponding to the metering zone 10 c and the compression zone 10 b of the screw 10, and the screw. The temperature of the rear portion of the heating cylinder corresponding to the 10 feed zones 10a is controlled to 310 ° C. However, the temperature of the heating cylinder 6 is preferably set in the range of 300 ° C. to 390 ° C. in the front part of the heating cylinder and the middle part of the heating cylinder, and more preferably set in the range of 330 ° C. to 380 ° C. desirable.

  Next, the measuring method of this embodiment will be described in detail based on FIG. 2 and FIG. In the present embodiment, one DVD disk substrate is formed by one injection filling into the disk substrate molding die 3. As shown by the horizontal axis in FIG. 2, the molding cycle time is 2.0 seconds. In FIG. 2, line A shows the screw position, line B shows the screw rotation speed, and line C shows the screw back pressure.

  As shown in FIG. 2 and FIG. 3, when the injection filling process consisting of injection and holding pressure is completed, the control device 4 proceeds to the measurement process. The screw position A (screw axial position) at the start of the metering process is the cushion position P0 where the previous injection filling has been completed and the molten resin 7 has remained slightly in front of the central inner hole of the heating cylinder 6. The axial movement of the screw 10 is controlled by pressure control in which the load cell 14 detects the pressure and controls the injection servo motor 12 until the middle of the metering process following the previous injection filling process. Note that the measuring step may be started in the middle of holding pressure.

  When the metering process is started, a signal is sent from the control device 4 to the screw rotation servomotor 15, and the screw 10 is started to rotate together with the drive of the screw rotation servomotor 15 (S1). The screw 10 is calculated from the set rotational speed (during screw speed constant speed control) input from the setting unit and the set time until it reaches the set rotational speed, and the rotational speed increase control (S2) is performed with the slope. Made. In the present embodiment, the set time is 0.15 seconds. When it is detected by the rotary encoder 12a attached to the screw rotation servomotor 15 that the screw rotation speed B has reached the set rotation speed (S3), the screw rotation speed B is then maintained at the set rotation speed. The process proceeds to screw speed constant speed control (S4). In the present embodiment, the set rotation speed of the screw 10 in the screw rotation speed constant speed control (S4) is 450 rpm.

  When a polycarbonate resin is used, the set rotational speed of the screw 10 varies depending on the molding cycle time and the diameter of the screw 10, but is preferably 400 rpm to 550 rpm, and more preferably 410 rpm to 470 rpm. If the screw speed B is lower than 400 rpm, it is difficult to shorten the time of the metering process, and if it exceeds 550 rpm, the probability of occurrence of defects such as silver streaks increases due to air entrainment. It should be noted that the screw speed constant speed control (S4) does not exclude that multiple stages can be set, for example, 460 rpm in the first half and 420 rpm in the second half. All of the numerical ranges described above or the numerical ranges described later are used by using an injection device 2 of a standard disk substrate molding injection molding machine 1 having a diameter of the screw 10 of 24 mm to 30 mm. This is a desirable numerical range (rpm, MPa, seconds) in the case of forming a single DVD disk substrate by injection filling 3.

Next, it is detected by the rotary encoder 12a of the injection servomotor 12 whether the screw position A has reached the switching position P1 D (mm) before the screw retreat completion position P2 (S5). The switching position P1 is calculated by the following equation stored in advance in the storage unit using the set rotation speed of the screw 10 in the screw rotation speed constant speed control (S4) and the screw retraction completion position P2.

  Here, r is a set rotation speed (rpm) at the time of screw rotation speed constant speed control (S4), and is set and inputted from the setting unit as a condition of the measuring process. R is the maximum set rotational speed (rpm) that can be set during screw rotational speed constant speed control (S4), and is fixedly stored in advance in the storage unit as a value unique to the disk substrate molding injection molding machine 1. Yes. E is a coefficient (mm).

  In this embodiment, when the rotary encoder 12a of the injection servo motor 12 detects the switching position P1 calculated as described above, the screw rotation speed constant speed control (S4) is terminated, but the screw 10 is The time for screw speed constant speed control (S4), which is rotated at a high speed at the set speed, is set to 0.4 seconds. The screw speed constant speed control (S4) time is preferably 0.30 to 0.55 seconds, and more preferably 0.35 to 0.50 seconds. The calculation of the switching position P1 for determining completion of the screw rotation speed constant speed control (S4) may be performed by actually measuring the actual screw rotation speed and calculating from the actual measurement value. The switching position P1 is determined from the detection of the total rotation speed of the screw after the start of the screw rotation speed constant speed control (S4), the detection of the reverse speed of the screw, and the start of the screw rotation speed constant speed control by the timer. You may perform by other means, such as time detection and the actual measurement detection of the screw position set by the operator.

  When the screw position A reaches the switching position P1 calculated as described above, the control device 4 changes the control of the injection servo motor 12 from the pressure control described above to the speed control (S6). At the same time, the control device 4 starts measuring the deceleration time T1 with a timer (S7). When the operator selects and sets an appropriate deceleration pattern from a plurality of deceleration patterns stored in the storage unit before molding, the deceleration time T1 by the timer is calculated using the set rotational speed. Then, the screw rotation servomotor 15 is controlled by the deceleration time T1, which is the calculated time constant, and screw rotation speed reduction control (S8) is performed. In this embodiment, the time from when the screw rotation speed reduction control (S8) is started to when the screw 10 is stopped is 0.15 to 0.35 seconds, and the screw rotation speed B is 0. It is more preferable that the screw rotation speed B becomes 0 in 0.17 to 0.25 seconds. In this embodiment, only one deceleration pattern is selected, but another deceleration pattern may be combined in the first half and the second half of the deceleration start. Further, the deceleration time T1 (time constant) until the rotation is stopped may be directly input.

  In the screw speed reduction control (S8), when the rotary encoder 12a of the injection servomotor 12 detects that the screw 10 has moved back to the screw reverse completion position P2 (S9), the screw 10 stops moving backward. (S10). Until the suck back is started, the injection servo motor 12 is servo-locked, and the screw 10 is stopped at the screw retraction completion position P2. In the present embodiment, by selecting and setting the deceleration pattern, the screw rotation speed reduction control (so that the screw rotation by the screw rotation servomotor 15 is continued for about 0.15 seconds even after the backward movement of the screw 10 is stopped ( S8) is performed. The time from when the screw 10 reaches the screw retraction completion position P2 until the screw rotation stops is preferably 0.05 seconds to 0.25 seconds and the screw rotation speed B becomes 0, and more preferably 0.10. It is more preferable that the screw rotation speed B becomes 0 in seconds to 0.20 seconds.

  Therefore, at the initial stage of the screw speed reduction control (S8), while the speed is controlled by the injection servo motor 12 and the screw position A is continuously retracted, the screw speed B continues to decrease relatively at the same time. Therefore, the screw back pressure C gradually decreases from 4.5 MPa to 3.0 MPa and 1.5 MPa. Then, after the screw 10 is stopped at the screw retraction completion position P2 by the injection servo motor 12, only the rotation of the screw 10 is continued while the rotation speed is reduced, so that the molten resin 7 further moves forward of the screw 10. Then, the screw back pressure C increases again by 1.5 MPa and becomes substantially the same value as at the start of the screw rotation speed reduction control (S8).

  When the screw rotation speed B further decreases to a certain value or less with the passage of time, the pressure of the molten resin 7 stored in front of the screw 10 is higher than the pressure of the molten resin 7 due to the rotation of the screw 10. As the pressure increases, the pressure of the molten resin 7 begins to decrease again, and at the same time, the check valve 10d is closed. During this time, the screw back pressure C decreases smoothly again by 1.5 MPa. It is particularly important when the screw rotation speed B is performed at a high speed to smoothly reduce the screw back pressure C at this time. As described above, the screw rotation speed after the screw rotation speed reduction control (S8) is started. By controlling the time until B stops and the time until the screw rotation stops after the screw 10 reaches the screw retreat completion position P2, the curve of the screw back pressure C that smoothly decreases can be obtained. .

  Note that the peak C1 formed by the re-raising and lowering of the screw back pressure C during the screw speed reduction control (S8) is preferably raised and lowered within a range of 1.0 MPa to 2.0 MPa. By providing such a peak C1 of the screw back pressure C in the screw rotation speed reduction control (S8), the state of the molten resin 7 that has been measured is stabilized even if the screw rotation speed B is a high rotation of 400 rotations or more. be able to. The control for forming the peak C1 in the screw back pressure C can be performed by controlling the pressure of the screw back pressure C until the screw rotation stops, but in the sense that the screw retreat completion position P2 is accurately determined, It is more desirable to control the screw position A by the servo motor 12.

  Then, the screw rotation continues to be decelerated by the arithmetic expression, and when the deceleration time T1 measured by the timer elapses (S11), the rotation of the screw 10 is stopped (S12). When the rotation of the screw 10 is stopped, a suck back (S13) is performed to slightly retract the screw 10 next. When sucking back (S13), a signal is sent from the control device 4 to the servomotor 12 for injection, and the screw 10 is moved backward by a predetermined distance. In this embodiment, the screw back pressure C is further reduced by about 1.0 MPa as shown by C2 in FIG. 2 by performing the suck back (S13). Become. Note that the timing of the suck back (S13) may be the time after the screw position A reaches the screw reverse completion position P2, and the suck back itself is not essential for the present invention.

  The metering process is completed by the end of suckback, but the time from the start of injection to the completion of the metering process is 1.2 seconds in this embodiment. On the other hand, on the disk substrate molding die 3 and the mold clamping device side, the cooling of the disk substrate formed by the previous injection and the cavity depressurization are completed before the completion of the weighing process. Therefore, in the disk substrate molding injection molding machine 1 of the present embodiment, a series of processes such as mold opening, disk substrate removal, and mold clamping are performed on the mold clamping device side at the same time as the weighing process is completed. Injection filling is performed. It should be noted that the time from the start of the injection filling process to the completion of the metering process requires 0.4 to 0.6 seconds for injection / holding pressure, and may be 1.0 to 1.5 seconds by adding the metering process. Desirably, in the present invention, the entire molding cycle time is added to the operation time on the clamping side, and one molding cycle is completed in 1.8 seconds to 2.8 seconds.

  The present invention is not limited to the embodiments shown and described above, and various modifications can be added and implemented without departing from the spirit of the invention. For example, the actuator for controlling the screw position A and the screw back pressure C is described as being executed by the injection servo motor 12, but may be executed by a hydraulic device such as a servo valve. Further, although the screw rotation motor is described as being executed by the screw rotation servomotor 15, it can be replaced with an induction motor or hydraulic motor using an inverter. In addition, when using a resin other than polycarbonate resin, some of the above numerical values cannot be used as they are, but the control method is similarly performed.

It is a fragmentary sectional view which shows the principal part outline | summary of the injection molding machine for disk board | substrate shaping | molding of embodiment. It is a graph which shows the change of the screw position, screw rotation speed, and screw back pressure in the measurement process of an embodiment. It is a flowchart which shows the measuring method of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection molding machine for disk substrate molding 2 Injection device 3 Mold for disk substrate molding 4 Control device 5 Nozzle 6 Heating cylinder 7 Molten resin 8 Cavity 9 Band heater 10 Screw 10a Feed zone 10b Compression zone 10c Metalling zone 10d Backflow prevention valve DESCRIPTION OF SYMBOLS 11 Housing 12 Servo motor 12a, 15a Rotary encoder 16 Ball nut 17 Ball screw A Screw position B Screw rotation speed C Screw back pressure D Predetermined distance P0 Cushion position P1 Switching position P2 Screw retraction completion position

Claims (4)

In the weighing method of the disk substrate molding injection molding machine, the screw in the heating cylinder is rotated by a screw rotation motor, and the screw is moved backward while supplying polycarbonate resin to the front of the screw.
While setting the set temperature of the portion of the heating cylinder corresponding to the compression zone and the metering zone of the screw to 300 ° C. to 390 ° C.,
During 0.30 seconds to 0.55 seconds, the screw rotation speed is controlled at 400 rpm to 550 rpm, and the screw rotation speed constant speed control is performed.
From the switching position to the screw speed reduction control obtained using the set value or the actual measurement value of the screw speed at the time of the screw speed constant speed control,
A metering method for an injection molding machine for forming a disk substrate, characterized in that screw rotation speed reduction control is performed so that the rotation speed becomes 0 in 0.15 seconds to 0.35 seconds. 2. The measuring method of an injection molding machine for forming a disk substrate according to claim 1, wherein the molding cycle time from the start of the measuring process to the start of the next measuring process is 1.5 seconds to 2.8 seconds. The screw rotation speed reduction control is performed so that the screw rotation speed becomes 0 in 0.05 seconds to 0.25 seconds after reaching a preset screw retreat completion position. 3. A measuring method of an injection molding machine for molding a disk substrate according to 2. 4. The disk substrate molding injection molding machine according to claim 1, wherein the screw speed reduction control selects and sets an appropriate deceleration pattern from a plurality of deceleration patterns. 5. Weighing method.

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