JP2007118406A - Control method of injection molding machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately stop both of the rotation and retreat of a screw at the time of completion of metering and to ensure high-degree metering precision uniformized in resin density. <P>SOLUTION: A stop target position Xes where a predetermined distance Ls is added to a screw rotation stop position Xe and a rotational speed pattern Ar for rotating the screw 2 are preset and, at the time of metering, a screw position X is detected at every interval of a predetermined time Ts at the time of metering. The residual rotational speed pattern Ar for stopping the rotation of the screw 2 at the stop target position Xes is operationally estimated from the detected screw position X and the screw 2 is rotationally controlled on the basis of the estimated rotationally speed pattern Ar while the rotation stop control of the screw 2 is performed when the screw 2 reaches the screw rotation stop position Xe and, when the retreat speed of the screw 2 becomes a preset predetermined speed Vds, the retreat stop control of the screw 2 is performed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of controlling an injection molding machine that performs measurement by rotating a screw while applying a back pressure to the screw, and stopping the rotation of the screw when the screw is retracted to a preset screw rotation stop position.

  In general, the molding cycle of an injection molding machine has a metering step and an injection step. In the metering step, the screw is rotated to perform metering, and the metering is terminated when the screw is retracted to a preset screw rotation stop position. Weighing control is performed. By the way, various controls such as speed control, pressure control, and position control are performed in the weighing process, but increasing the control accuracy for a series of controls in the weighing process ensures a uniform molding quality amount and high quality molding. Various control methods have been proposed in the past, which is extremely important in obtaining products.

For example, Japanese Examined Patent Publication No. 6-61800 discloses a control method in which a screw is moved backward while rotating at a preset screw rotation number, and the screw is stopped at a preset measurement completion position. The screw rotation detected by the screw position detected by the screw speed detecting means and the screw retraction speed detected by the screw speed detecting means is calculated by calculating a screw rotation speed such that the screw is stopped at the measurement completion position by a predetermined calculation formula. An injection molding machine control method (metering control device) is disclosed in which a number is sent as a rotational drive command. Japanese Patent Laid-Open No. 2004-154988 discloses a screw rotation speed that is proportional to the positional deviation between the set weighing completion position and the current screw retraction position after the screw has moved back to the setting screw position near the set weighing completion position. The screw rotation speed is corrected based on the pressure deviation between the set resin pressure and the current detected resin pressure, and the screw rotation speed is controlled as a screw rotation speed command. A control method (metering method) is disclosed.
JP 6-61800 Japanese Patent Laid-Open No. 2004-154988

  However, the above-described conventional injection molding machine control method has the following problems.

  First, as in Patent Document 1, a screw position and a screw retraction speed are detected, a screw rotation number for stopping the screw at a measurement completion position is calculated, and a control method using the calculated screw rotation number as a rotation drive command is adopted. In such a case, the rotational speed of the screw near the measurement completion position becomes almost zero, and it takes a considerable time for the screw to reach the measurement completion position. For this reason, although it is advantageous for improving the control accuracy of the screw position, the cycle time cannot be shortened, which is extremely disadvantageous in realizing high-speed molding, and it is also limited to increase molding efficiency and mass productivity. Produce.

  Further, as in Patent Document 2, after the screw is retracted to the set screw position in the vicinity of the set measurement completion position, the screw rotation speed proportional to the positional deviation between the set measurement completion position and the current screw retract position is obtained and set. When a control method is adopted in which the screw rotational speed command is corrected by correcting the pressure deviation between the resin pressure and the current detected resin pressure, the control in the vicinity of the set weighing completion position is only the position control, and the control target is fixed. For this reason, although it is advantageous to increase the control accuracy of the screw position, the back pressure control needs to be performed by adjusting the screw rotation speed. It is difficult to ensure responsiveness and stability in realizing the above.

  Furthermore, in weighing control, it is required to stop both the rotation and retraction of the screw properly at the time of completion of weighing (at the end of weighing) in order to equalize the resin density and ensure high weighing accuracy. In the case of Patent Documents 1 and 2, no consideration is given to properly stopping both the rotation and retraction of the screw, and an optical disk with a thin thickness in recent times that requires a high degree of measurement accuracy. It cannot respond sufficiently to the molding of

  An object of the present invention is to provide a method for controlling an injection molding machine that solves the problems existing in the background art.

  In order to solve the above-described problem, the present invention performs measurement by rotating the screw 2 while applying a back pressure Pd to the screw 2 and, if the screw 2 is retracted to a preset screw rotation stop position Xe, the screw 2. In the control method of the injection molding machine M that stops the rotation of the screw, the stop target position Xes obtained by adding the predetermined distance Ls to the screw rotation stop position Xe and the rotation speed pattern Ar that rotates the screw 2 are set in advance. The screw position X is detected every predetermined time Ts interval, and the remaining rotation speed pattern Ar for stopping the rotation of the screw 2 from the detected screw position X at the stop target position Xes is predicted by calculation, and the predicted rotation speed pattern Ar To control the rotation of the screw 2, and if the screw 2 reaches the screw rotation stop position Xe, the screw It performs rotation stop control for the Ryu 2, and is characterized by performing a retraction stop control for the screw 2 if retraction rate of the screw 2 reaches a predetermined speed Vds set in advance.

  In this case, according to a preferred aspect of the invention, the rotational speed pattern Ar includes at least a constant speed section Arc in which the rotational speed of the screw 2 is constant, and a deceleration section that decelerates at a predetermined deceleration rate from the end of the constant speed section Arc. Ars can be included. On the other hand, in the control method according to the present invention, a virtual retreat speed pattern Ab in which the screw 2 retreats is set in advance, and the retreat speed Vd of the screw 2 is detected every predetermined time Ts during measurement, and the detected retreat speed is detected. The remaining reverse speed pattern Ab is predicted by calculation from the speed Vd, the limit value VL (VLa...) For the reverse speed is set, and the back pressure control at the time of prediction is set to the pressure control amount Dp or the screw rotation stop position Xe. On the other hand, the screw 2 can be controlled to move backward by selecting a control amount Dp or Dx that is smaller of the position control amount Dx for performing position control. At this time, the limit value VL (VLa...) Can be set based on the predicted maximum value of the remaining reverse speed pattern Ab. Further, the reverse speed pattern Ab can include at least a constant speed section Abc in which the reverse speed of the screw 2 is constant and a deceleration section Abs that decelerates at a predetermined deceleration rate from the end of the constant speed section Abc. The reverse speed of the screw 2 in the constant speed section Abc is set to be larger than the actual reverse speed Vd of the screw 2. The predetermined speed Vds can be set in the range of 0.01 to 0.1 [mm / s]. On the other hand, the screw position (first stop position X1) where the rotation of the screw 2 is stopped by the rotation stop control and the screw position (second stop position X2) where the backward movement of the screw 2 is stopped by the reverse stop control are detected. A deviation Xa between the stop position X1 and the second stop position X2 is obtained. Based on this deviation Xa, at least one of molding conditions of the injection process, specifically, an injection speed setting switching position, an injection pressure setting switching position, and an injection completion position. Can be corrected. The deviation Xa can also be displayed on the display 3. Furthermore, after the backward movement of the screw 2 is stopped by the backward movement stop control for the screw 2, the suck back process can be performed.

  According to the control method of the injection molding machine M according to the present invention by such a method, the following remarkable effects are obtained.

  (1) Since both the rotation and retraction of the screw 2 can be stopped properly at the end of the measurement, it is possible to ensure a high measurement accuracy with a uniform resin density. As a result, it is possible to sufficiently cope with the molding of a thin optical disk or the like that is recently required to have a particularly high measurement accuracy.

  (2) A stop target position Xes obtained by adding a predetermined distance Ls to the screw rotation stop position Xe and a rotation speed pattern Ar for rotating the screw 2 are set, and the screw position X is detected every predetermined time Ts interval, and the detected screw The remaining rotation speed pattern Ar for stopping the rotation of the screw 2 from the position X to the stop target position Xes is predicted by calculation, and the rotation of the screw 2 is controlled by the predicted rotation speed pattern Ar, so that the screw 2 is screw rotation stop position Xe. Therefore, since the rotation stop control for the screw 2 is performed, it is possible to shorten the cycle time while improving the control accuracy of the screw rotation stop position Xe, and to improve the molding efficiency and mass productivity while maintaining the high molding quality. Can realize high-speed molding.

  (3) According to a preferred embodiment, the rotational speed pattern Ar includes at least a constant speed section Arc in which the rotational speed of the screw 2 is constant and a deceleration section Ars that decelerates at a predetermined deceleration rate from the end of the constant speed section Arc. If it does, rotation control with respect to the screw 2 can be implemented reliably and stably.

  (4) According to a preferred embodiment, a virtual reverse speed pattern Ab in which the screw 2 moves backward is set, the reverse speed Vd of the screw 2 is detected at every predetermined time Ts interval, and the remaining reverse speed is determined from the detected reverse speed Vd. The position where the pattern Ab is predicted by calculation, the limit value VL (VLa...) For the reverse speed is set, and the pressure control amount Dp for performing the back pressure control at the time of prediction or the position control for the screw rotation stop position Xe is performed. If the control amount Dp or Dx that is smaller than the control amount Dx is selected and the screw 2 is reversely controlled, the responsiveness and stability of the control for stopping the reverse in relation to the rotation stop control for the screw 2 can be improved. At the same time, reliable and accurate back pressure control in a short distance section can be realized.

  (5) According to a preferred embodiment, the reverse speed pattern Ab includes at least a constant speed section Abc in which the reverse speed of the screw 2 is constant and a deceleration section Abs that decelerates at a predetermined deceleration rate from the end of the constant speed section Abc. In addition, if the reverse speed of the screw 2 in the constant speed section Abc is set larger than the actual reverse speed Vd of the screw 2, the reverse control with respect to the screw 2 can be performed reliably and stably.

  (6) If the limit value VL (VLa...) Is set based on the predicted maximum value of the remaining reverse speed pattern Ab, the reverse control for the screw 2 can be performed easily and reliably.

  (7) If the predetermined speed Vds is set within a range of 0.01 to 0.1 [mm / s] according to a preferred embodiment, the backward movement of the screw 2 is stopped while sufficiently ensuring the uniformity of the resin density. Control can be performed reliably and stably.

  (8) According to a preferred embodiment, the first stop position X1 and the second stop position X2 are detected, and a deviation Xa between the first stop position X1 and the second stop position X2 is obtained. Specifically, if at least one of the injection speed setting switching position, the injection pressure setting switching position, and the injection completion position is corrected, the variation in the stop position of the screw 2 is reflected in the molding conditions of the injection process. Thus, the molding quality can be further improved.

  (9) If the deviation Xa is displayed on the display 3 according to a preferred mode, the operator can easily grasp the deviation Xa, so the degree of influence on the molding quality is judged, and the molding conditions and control conditions are determined. It can be dealt with appropriately, such as changing.

  (10) According to a preferred embodiment, if the suckback process is performed after the backward movement of the screw 2 is stopped by the backward movement stop control with respect to the screw 2, it is possible to shift to the injection process in a state where the measurement accuracy is highly secured. Variations in the injection process based on the suck back process (variations in the molded product) can be eliminated.

  Next, the best embodiment according to the present invention will be given and described in detail with reference to the drawings.

  First, the configuration of an injection molding machine M that can implement the control method according to the present embodiment will be described with reference to FIGS. 3 and 4.

  The injection molding machine M shown in FIG. 3 shows only the injection device Mi excluding the mold clamping device. The injection device Mi includes an injection table 11 and a drive table 12 that are separated from each other, and the rear end of the heating cylinder 13 is supported by the front surface of the injection table 11. The heating cylinder 13 includes an injection nozzle 14 at the front end and a hopper 15 that supplies a molding material to the inside of the heating cylinder 13 at the rear, and the screw 2 is inserted into the heating cylinder 13.

  On the other hand, four tie bars 16 are installed between the injection table 11 and the drive table 12, and a slide block 17 is slidably loaded on the tie bars 16. A rotary block 19 integrally having a driven wheel 18 is rotatably supported at the front end of the slide block 17, and the rear end of the screw 2 is coupled to the center of the rotary block 19. A screw rotating servo motor (electric motor) 20 is attached to the side surface of the slide block 17, and the drive wheel 21 fixed to the rotating shaft of the servo motor 20 is connected to the driven wheel 18 via the rotation transmission mechanism 22. To do. The rotation transmission mechanism 22 may be a gear-type transmission mechanism using a transmission gear or a belt-type transmission mechanism using a timing belt. Further, the servo motor 20 is provided with a rotary encoder 23 for detecting the rotation speed (rotation speed) of the servo motor 20.

  On the other hand, a nut portion 25 is provided coaxially and integrally on the rear portion of the slide block 17, and the front side of the ball screw portion 26 that is rotatably supported by the drive base 12 is screwed into the nut portion 25. A screw mechanism 24 is configured. A driven wheel 27 is attached to the rear end of the ball screw portion 26 that protrudes rearward from the drive base 12, and a screw advancing / retreating servomotor (electric motor) 28 is attached to the support plate 12 s attached to the drive base 12. The driving wheel 29 fixed to the rotating shaft of the servo motor 28 is connected to the driven wheel 27 via the rotation transmission mechanism 30. The rotation transmission mechanism 30 may be a gear-type transmission mechanism using a transmission gear or a belt-type transmission mechanism using a timing belt. Further, the servo motor 28 is provided with a rotary encoder 31 for detecting the rotation speed (rotation speed) of the servo motor 28.

  Further, in FIG. 3, reference numeral 32 denotes a controller provided in the injection molding machine M, and a series of control (sequence control) and calculation in the control method according to the present embodiment can be executed by the stored control program 32p. On the other hand, the controller 32 is connected to the servo motors 20 and 28 and the rotary encoders 23 and 31 described above, and is connected to a pressure sensor (load cell) 33 interposed between the rotary block 19 and the slide block 17. This pressure sensor 33 can detect the back pressure Pd against the screw 2. Furthermore, the display 3 is connected to the controller 32.

  FIG. 4 is a block system diagram of main functional units in the controller 32. In the figure, reference numeral 41 denotes a speed feedback control system on the screw rotation side, which includes a deviation calculating section 42, a speed compensating section 43, and a speed converting section 44. The output of the speed compensating section 43 is given to the screw rotating servo motor 20. Is done. Further, one input unit (non-inverted input unit) of the deviation calculating unit 42 is supplied with a rotation speed command value for rotating the screw 2 from the controller main body 32m, specifically, based on a rotation speed pattern Ar described later. A speed command value is given, and a detected value of the rotational speed of the screw 2 is given from the speed conversion part 44 to the other input part (reverse input part) of the deviation calculating part 42. A detection value of the rotational position of the screw 2 obtained from the rotary encoder 23 attached to the servo motor 20 is given to the input side of the speed conversion unit 44, and the detection value of this rotational position is converted by the speed conversion unit 44 into the rotational speed. Converted to detection value. The detected value of the rotation speed is also given to the controller main body 32m.

  On the other hand, 45 is a feedback control system on the screw advance / retreat side, 45x is a position feedback control system, and 45p is a pressure feedback control system. The position feedback control system 45 x includes a deviation calculation unit 46 and a position compensation unit 47, and an output (position control amount Dx described later) of the position compensation unit 47 is given to the control amount selection unit 48. In addition, a preset screw rotation stop position Xe is given as a command value from the controller main body 32m to one input unit (non-inverting input unit) of the deviation calculation unit 46, and the other input of the deviation calculation unit 46 The screw position X (detected value) obtained from the rotary encoder 31 attached to the screw advance / retreat servomotor 28 is given to the part (reverse input part). The screw position X is also given to the controller main body 32m. On the other hand, the pressure feedback control system 45 p includes a deviation calculating unit 49 and a pressure compensating unit 50, and an output of the pressure compensating unit 50 (a pressure control amount Dp described later) is given to the control amount selecting unit 48. Also, one input unit (non-inverted input unit) of the deviation calculating unit 49 is given a back pressure Ps as a command value from the controller main body 32m, and the other input unit (inverted input) of the deviation calculating unit 49. The detection value (back pressure Pd) obtained from the pressure sensor 33 is applied to the (part). This back pressure Pd is also applied to the controller main body 32m.

  Next, a control method according to the present embodiment using such an injection molding machine M will be described according to the flowcharts shown in FIGS. 1 and 2 with reference to FIGS.

  In the measuring step, the operation control of the screw rotation servomotor 20 and the operation control of the screw advance / retreat servomotor 28 are simultaneously performed in association with each other (steps SR and SB).

  First, a control method centering on the operation control of the screw rotation servomotor 20 will be described according to the flowchart shown in FIG. 2 with reference to FIGS. 5 represents a rotational speed pattern Ar with the horizontal axis as time, and FIG. 6 represents a rotational speed pattern Ar with the horizontal axis as the screw position.

  First, a stop target position Xes obtained by adding a predetermined distance Ls to the screw rotation stop position Xe and a rotation speed pattern Ar for rotating the screw 2 are set (step SR1). In this case, as the predetermined distance Ls, for example, a slight distance of about 0.01 to 0.05 [mm] can be arbitrarily selected. Further, as shown in FIGS. 5 and 6, the rotational speed pattern Ar has an acceleration section Ara that accelerates the rotational speed of the screw 2 at a predetermined acceleration rate (acceleration coefficient), and the rotational speed is constant from the end of the acceleration section Ara. Is set by a constant speed section Arc that becomes and a deceleration section Ars that decelerates at a predetermined deceleration rate from the end of the constant speed section Arc. Thus, by including at least the constant speed section Arc and the deceleration section Ars in the rotational speed pattern Ar, the rotation control for the screw 2 can be performed reliably and stably.

  On the other hand, at the time of measurement, a command value for the rotational speed for rotating the screw 2 based on the set rotational speed pattern Ar is given from the controller main body 32m to the deviation calculating section 42, and the screw rotation servomotor 20 is controlled to operate (speed control). (Step SR2). In this case, the deviation calculating unit 42 obtains the speed deviation between the rotational speed (detected value) of the screw 2 applied from the speed converting unit 44 and the rotational speed (command value) applied from the controller main body 32m. The deviation is given to the speed compensator 43, compensated for speed, and then given to the servo motor 20. Thereby, feedback control with respect to the rotational speed of the screw 2 is performed so that the rotational speed (detected value) of the screw 2 matches the command value.

  Further, during the operation of the servo motor 20, the position of the screw 2 (screw position X) is obtained by the rotary encoder 31 every predetermined time Ts interval (for example, 50 to 200 [μs] interval) (step SR3). In the controller main body 32m, the remaining rotation speed pattern Ar for stopping the rotation of the screw 2 at the stop target position Xes from the screw position X detected every predetermined time Ts interval is predicted by calculation (step SR4). In this case, by detecting the actual screw position X, the already weighed resin amount can be known, and the remaining resin amount to be weighed can be calculated from the measured resin amount. A rotational speed pattern Ar to be stopped at Xes is predicted. After the prediction, the screw 2 is rotationally controlled by the predicted rotation speed pattern Ar. Furthermore, since the stop target position Xes and the deceleration start point tc shown in FIGS. 5 and 6 are specified for each prediction time based on the prediction of the rotational speed pattern Ar, the screw 2 reaches the deceleration start point tc shown in FIG. Then, deceleration (deceleration section Ars) is started (steps SR5 and SR6), and when the screw 2 reaches the screw rotation stop position Xe, the rotation of the screw 2 is stopped, that is, the rotation of the servo motor 20 is controlled to stop. Servo lock is performed (steps SR7 and SR8).

  By the way, the rotational speed of the predicted rotational speed pattern Ar at the screw rotation stop position Xe is not zero but the magnitude of Ve as shown in FIGS. 5 and 6, but when the screw rotation stop position Xe is reached. A control for forcibly stopping the rotation of the screw 2 is performed by outputting a screw rotation stop command. Since the magnitude of the rotational speed Ve at this time can be varied by selecting the predetermined distance Ls described above, the time to reach the screw rotation stop position Xe is shortened by selecting the length of the predetermined distance Ls, and the screw rotation What is necessary is just to set the magnitude | size of the optimal rotational speed Ve which stops the rotation of the screw 2 rapidly by the output of a stop command. Therefore, as shown in FIG. 6, the rotational speed Vrs in the deceleration zone Ars of the predicted rotational speed pattern Ar becomes zero at the stop target position Xes, but the actual rotational speed Vrd is, as indicated by the phantom line, It becomes zero at the rotation stop position Xe.

  In actual control, since the rotational speed of the screw 2 is detected with respect to the screw position X, control according to the waveform shown in FIG. 6 is performed. For this reason, for example, when the biting state of the molding material with respect to the screw 2 is changed, the speed is reduced at a constant rate in the deceleration zone Ars with respect to time, which causes variation at the screw rotation stop position Xe. Since the detected rotational speed of the screw 2 is different in the deceleration zone Ars with respect to X, the screw 2 can be reliably stopped at the screw rotation stop position Xe by correcting the command value.

  As described above, in the operation control on the screw rotation servomotor 20 side, the stop target position Xes obtained by adding the predetermined distance Ls to the screw rotation stop position Xe and the rotation speed pattern Ar for rotating the screw 2 are set, and the predetermined time. The screw position X is detected at every Ts interval, and the remaining rotation speed pattern Ar that stops the rotation of the screw 2 from the detected screw position X to the stop target position Xes is predicted by calculation, and the screw is predicted by the predicted rotation speed pattern Ar. 2 is controlled, and if the screw 2 reaches the screw rotation stop position Xe, the rotation of the screw 2 is stopped. Therefore, the cycle time can be shortened while improving the control accuracy of the screw rotation stop position Xe. Improve molding efficiency and mass productivity while maintaining high molding quality, and at high speed. It can be realized.

  Next, a control method centering on the operation control of the screw advance / retreat servomotor 28 will be described according to the flowchart shown in FIG. 1 with reference to FIGS.

  First, a back pressure Ps for the screw 2 and a virtual retraction speed pattern Ab for retreating the screw 2 are set in advance (step SB1). In this case, as shown by the solid line in FIG. 7A, the reverse speed pattern Ab is an acceleration zone Aba for accelerating the reverse speed of the screw 2 at a predetermined acceleration rate (acceleration coefficient), and reverse from the end of this acceleration zone Aba. A constant speed section Abc where the speed is constant and a deceleration section Abs where the vehicle decelerates at a predetermined deceleration rate from the end of the constant speed section Abc are set. Xeb represents a virtual screw rotation stop position in the reverse speed pattern Ab. Further, the reverse speed of the screw 2 in the constant speed section Abc is set to be larger than the actual reverse speed Vd of the screw 2. That is, a magnitude that is not actually possible is set with respect to the actual reverse speed Vd assumed in advance. As described above, the reverse speed pattern Ab includes at least the constant speed section Abc and the deceleration section Abs, and the reverse speed of the screw 2 in the constant speed section Abc is set larger than the actual reverse speed Vd of the screw 2. Thus, the backward control for the screw 2 can be carried out reliably and stably.

  On the other hand, during metering, the screw advancing / retreating servomotor 28 is controlled to perform reversing control on the screw 2 (step SB2). In this case, the screw position X and the reverse speed Vd of the screw 2 are detected at predetermined time intervals Ts (for example, 50 to 200 [μs] intervals) (step SB3). Then, the remaining reverse speed pattern Ab is predicted by calculation from the detected reverse speed Vd (step SB4). That is, the amount of resin already measured can be known by detecting the actual reverse speed Vd (screw position X), and the remaining amount of resin to be measured can be calculated from the measured amount of resin. The remaining amount of resin to be weighed may be calculated so as to coincide with the area obtained by integrating the virtual reverse speed pattern Ab shown in FIG. 7A, and the remaining reverse speed pattern Ab can be easily obtained. Can be predicted. FIG. 7 (a) shows the predicted reverse speed pattern Ab in phantom lines, and FIGS. 7 (b), (c), (d), and (e) show the reverse speed patterns Ab predicted at different times. Show.

  Further, the controller 32m sets (changes) the limit value VL for the reverse speed of the screw 2 based on the predicted maximum value of the remaining reverse speed pattern Ab (step SB5). In this way, by setting the limit value VL based on the predicted maximum value of the remaining reverse speed pattern Ab, the control method according to the present invention for the screw reverse side can be easily and reliably performed.

  On the other hand, at the time of measurement, the controller 32m gives a back pressure Ps as a command value to the deviation calculating unit 49, and the deviation calculating unit 49 calculates the back pressure Ps and the back pressure Pd (detected value) obtained from the pressure sensor 33. While obtaining the pressure deviation, this pressure deviation is applied to the pressure compensation unit 50, and after pressure compensation by the pressure compensation unit 50, it is applied to the control amount selection unit 48 as the pressure control amount Dp for performing the back pressure control. . Further, the command value of the screw rotation stop position Xe is given to the deviation calculation unit 46 from the controller 32m, and the deviation calculation unit 46 determines the command value of the screw rotation stop position Xe and the screw position X (detection) obtained by the rotary encoder 31. (Position) is obtained, and the position deviation is compensated by the position compensation unit 47 and then given to the control amount selection unit 48 as a position control amount Dx for performing position control with respect to the screw rotation stop position Xe. Is done.

  The control amount selector 48 selects and outputs the smaller one of the pressure control amount Dp applied from the pressure compensator 50 and the position control amount Dx applied from the position compensator 47 (step SB6). . As a result, the selected pressure control amount Dp or position control amount Dx is applied to the servo motor 28. When the pressure control amount Dp is smaller than the position control amount Dx, pressure control (back pressure control), that is, the set back control amount is set. Feedback control is performed on the back pressure Pd so as to coincide with the pressure Ps, and when the position control amount Dx is smaller than the pressure control amount Dp, the screw position X is adjusted so as to coincide with the screw rotation stop position Xe. The feedback control for is performed.

  In this case, since the limit value VL for the reverse speed of the screw 2 is set large from the start of measurement to the vicinity of the screw rotation stop position Xe, basically, pressure control (back pressure control) is performed. That is, as shown in FIGS. 7B and 7C, since the constant speed section Abc remains in the predicted reverse speed pattern Ab, the reverse speed (maximum value) of the constant speed section Abc is set as the limit value VL. The position control amount Dx is set relatively larger than the pressure control amount Dp. On the other hand, after the screw 2 reaches the vicinity of the screw rotation stop position Xe, as shown in FIG. 7D, the constant speed section Abc of the reverse speed pattern Ab disappears as the screw 2 moves backward, and the deceleration section Since only Abs remains, the maximum value of the reverse speed pattern Ab decreases along the deceleration zone Abs, and the limit value VL also decreases. As a result, the limit value VL is set so as to gradually decrease as the screw 2 moves backward, such as VLa, VLb, VLc, VLd... Shown in FIG. As a result, the retraction speed of the screw 2 is regulated by the limit value VL, so that the position control amount Dx is more relative to the pressure control amount Dp from the vicinity of the screw rotation stop position Xe to the screw rotation stop position Xe. May occur.

  Actually, the pressure control amount Dp (pressure deviation) with respect to the back pressure is considerably small, and it is not clear which one of the feedback control with respect to the position and the feedback control with respect to the pressure is selected. However, by selecting the smaller control amount, the responsiveness and stability of the control for stopping the retreat in relation to the rotation stop control for the screw 2 can be improved, and the reliability in a slight distance section can be improved. In addition, accurate back pressure control can be realized.

  Such backward control with respect to the screw 2 is performed until the screw 2 reaches the screw rotation stop position Xe, and when the screw 2 reaches the screw rotation stop position Xe, the reverse control (back pressure control) is maintained. Then, the backward speed Vd of the screw 2 is monitored (steps SB7 and SB8). The monitoring of the reverse speed Vd does not mean monitoring the speed only in the reverse direction, but means monitoring the moving speed in the front-rear direction in the reverse control. When the rotation of the screw 2 is stopped, the screw 2 may temporarily move in the forward direction due to the applied back pressure, and the forward speed at this time is also included in the reverse speed Vd to be monitored. .

  In this case, even if the rotation stops when the screw 2 reaches the screw rotation stop position Xe, the resin pressure remains, so that the backward movement of the screw 2 does not stop simultaneously with the rotation stop of the screw 2. Therefore, when the backward movement of the screw 2 is stopped at the screw rotation stop position Xe, the variation in the resin pressure remains as it is. For this reason, even if the screw 2 reaches the screw rotation stop position Xe, the backward control of the screw 2 is maintained as it is, and the backward speed Vd of the screw 2 is monitored.

  On the other hand, the backward speed Vd of the screw 2 is monitored. As shown in FIG. 9, when the screw 2 reaches a predetermined speed Vds set in advance, the backward movement of the screw 2 is stopped at this time, that is, the rotation with respect to the servo motor 28 is performed. Stop control is performed, and servo lock is performed and control for stopping the application of back pressure is performed (steps SB9 and SB10). Therefore, the reverse speed Vd of the screw 2 becomes zero in this state. In this case, it is desirable to set the predetermined speed Vds within a range of 0.01 to 0.1 [mm / s]. Thereby, it is possible to reliably and stably perform control to stop the backward movement of the screw 2 while sufficiently ensuring the uniformity of the resin density (resin pressure). As described above, when the rotation of the screw 2 is stopped, the screw 2 may temporarily move in the forward direction due to the applied back pressure. In this case, the speed in the forward direction is When the predetermined speed Vds is reached, control is performed to stop the backward movement (movement) of the screw 2. FIG. 7E shows this state, which is a reverse speed pattern based on the actually detected reverse speed Vd. FIG. 9 shows the backward speed Vd of the screw 2 with the horizontal axis as the screw position X.

  On the other hand, the controller main body 32m detects the screw position (first stop position X1) where the rotation is stopped by the rotation stop control for the screw 2 and the screw position (second stop position X2) where the reverse is stopped by the reverse stop control for the screw 2. At the same time, a deviation Xa between the first stop position X1 and the second stop position X2 is obtained. Based on this deviation Xa, the molding conditions of the injection process performed after the above-described metering process, specifically, the injection speed setting switching position , At least one of the injection pressure setting switching position and the injection completion position is corrected. That is, correction is performed by adding or subtracting the deviation Xa to these positions. For this correction, it is desirable to provide a correction mode that can be selected separately so that the operator can arbitrarily select it. Therefore, the operator can confirm the deviation Xa displayed on the display 3 to be described later and determine whether or not to perform correction. Thereby, the variation in the stop position of the screw 2 can be reflected in the molding conditions of the injection process, and the molding quality can be further improved. Further, the obtained deviation Xa is displayed on the display 3. As a result, the operator can easily grasp the deviation Xa, determine the degree of influence on the molding quality, etc., and take appropriate measures such as selecting the correction mode described above and changing the molding conditions and control conditions. There are advantages you can

  Further, as shown in FIG. 9, the suck back process in which the screw 2 is retreated by a certain distance by the retreating speed Vs to release the pressure is stopped by the rotation stop control for the screw 2, and the retreat stop control for the screw 2. Can be performed after the reverse has stopped. If the weighing process is controlled by the control method according to the present invention, it is possible to shift to the next process in a state in which the weighing accuracy is highly secured. Therefore, variation in the injection process based on suck back processing (variation of molded product) Can be eliminated.

  As described above, in the operation control on the screw advance / retreat servomotor 28 side, the virtual retreat speed pattern Ab in which the screw 2 retreats is set, and the retreat speed Vd of the screw 2 is detected and detected every predetermined time Ts interval. The remaining reverse speed pattern Ab is predicted from the calculated reverse speed Vd by calculation, the limit value VL (VLa...) For the reverse speed is set, and the back pressure control at the time of prediction is performed. If a control amount Dp or Dx that is smaller than the position control amount Dx for performing position control on Xe is selected and the screw 2 is controlled to move backward, a control response for stopping the reverse operation in relation to the rotation stop control for the screw 2 Performance and stability, and can achieve reliable and accurate back pressure control in a short distance section. That.

  Further, by simultaneously performing the operation control on the screw advance / retreat servo motor 28 side and the above-described operation control on the screw rotation servo motor 20 side, both rotation and retraction of the screw 2 are stopped under appropriate conditions. Therefore, it is possible to secure a high measurement accuracy with the resin density made uniform. As a result, it is possible to sufficiently cope with the molding of a thin optical disk or the like that is recently required to have a particularly high measurement accuracy.

  Although the best embodiment has been described in detail above, the present invention is not limited to such an embodiment, and the scope of the present invention is not limited in the detailed configuration, quantity, numerical value, method, and the like. It can be changed, added, or deleted arbitrarily.

  For example, the injection molding machine M is an electric type using the servo motors 20 and 28, but may be another drive type such as a hydraulic drive type using a hydraulic cylinder or an oil motor. The rotational speed pattern Ar includes at least a constant speed section Arc in which the rotational speed of the screw 2 is constant and a deceleration section Ars that decelerates at a predetermined deceleration rate from the end of the constant speed section Arc. Although the case where the Ab is included at least in the constant speed section Abc where the reverse speed of the screw 2 is constant and the deceleration section Abs that decelerates at a predetermined deceleration rate from the end of the constant speed section Abc is given in Ab, The present invention is not limited to the case of decelerating at a predetermined deceleration rate, and the deceleration patterns of the deceleration sections Ars and Abs can be arbitrarily set.

The flowchart which shows the process sequence at the time of screw retreat in the control method of the injection molding machine which concerns on the best embodiment of this invention, The flowchart which shows the process sequence at the time of screw rotation in the control method, Partial cross-sectional plan view of an injection molding machine that can implement the control method, Block system diagram of the main functional parts of the controller provided in the injection molding machine, Characteristic diagram of the rotational speed of the screw with respect to time when the control method is implemented (rotational speed pattern diagram), Characteristic diagram of the rotational speed of the screw with respect to the screw position when the control method is implemented (rotational speed pattern diagram), Characteristic diagram of the reverse speed of the screw with respect to time when the control method is implemented (reverse speed pattern diagram), Explanatory drawing of the principle of changing the limit value for the screw retraction speed when the control method is implemented, Characteristic diagram of the reverse speed of the screw with respect to the screw position when the control method is implemented (reverse speed pattern diagram),

Explanation of symbols

2 Screw 3 Display M Injection molding machine Pd Back pressure Xe Screw rotation stop position Xes Stop target position X Screw position X1 First stop position X2 Second stop position Ls Predetermined distance VL Limit value VLa ... Limit value Vd Reverse speed Vds Predetermined speed Ar Rotational speed pattern Arc Constant speed section Ars Deceleration section Ab Reverse speed pattern Abc Constant speed section Abs Deceleration section Dp Pressure control amount Dx Position control amount

Claims (11)

  In the injection molding machine control method, the screw rotation is stopped in advance in the method of controlling the injection molding machine that rotates the screw while applying back pressure to the screw and performs measurement, and stops the screw rotation if the screw is retracted to a preset screw rotation stop position. A stop target position with a predetermined distance added to the position and a rotation speed pattern for rotating the screw are set, and at the time of weighing, the screw position is detected at predetermined time intervals, and the screw is rotated at the stop target position from the detected screw position. The remaining rotation speed pattern for stopping the screw is predicted by calculation, the screw is controlled to rotate based on the predicted rotation speed pattern, and if the screw reaches the screw rotation stop position, the rotation stop control for the screw is performed, and the screw is retracted. When the speed reaches a preset speed, The method of controlling an injection molding machine which is characterized in that the retraction stop control for.   2. The injection according to claim 1, wherein the rotational speed pattern includes at least a constant speed section in which the rotational speed of the screw is constant and a deceleration section that decelerates at a predetermined deceleration rate from the end of the constant speed section. Control method of molding machine.   In addition to setting a virtual reverse speed pattern in which the screw retreats in advance, the screw reverse speed is detected at predetermined time intervals during weighing, and the remaining reverse speed pattern is predicted by calculation from the detected reverse speed, and the reverse Set a limit value for the speed, and select the smaller control amount of the pressure control amount that performs back pressure control at the time of prediction or the position control amount that performs position control with respect to the screw rotation stop position, and control the screw to move backward The method of controlling an injection molding machine according to claim 1.   4. The method of controlling an injection molding machine according to claim 3, wherein the limit value is set based on a predicted maximum value of the remaining reverse speed pattern.   5. The reverse speed pattern includes at least a constant speed section in which the reverse speed of the screw is constant and a deceleration section that decelerates at a predetermined deceleration rate from the end of the constant speed section. Method of injection molding machine.   6. The method of controlling an injection molding machine according to claim 5, wherein the retreating speed of the screw in the constant speed section is set larger than the actual retreating speed of the screw.   2. The method of controlling an injection molding machine according to claim 1, wherein the predetermined speed is set in a range of 0.01 to 0.1 [mm / s].   A screw position (first stop position) where the rotation of the screw is stopped by the rotation stop control and a screw position (second stop position) where the screw retreat is stopped by the reverse stop control are detected, and the first stop position The method of controlling an injection molding machine according to claim 1, wherein a deviation of the second stop position is obtained, and molding conditions of the injection process are corrected based on the deviation.   9. The method of controlling an injection molding machine according to claim 8, wherein the molding condition includes at least one of an injection speed setting switching position, an injection pressure setting switching position, and an injection completion position.   9. The method of controlling an injection molding machine according to claim 8, wherein the deviation is displayed on a display.   9. The method of controlling an injection molding machine according to claim 1 or 8, wherein suck back processing is performed after the backward movement of the screw is stopped by the backward movement stop control with respect to the screw.

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