JP5529629B2 - Injection molding machine - Google Patents

Description

  The present invention relates to an injection molding machine, and more particularly, to a drive control method for an injection servo motor in a pressure holding process (higher-order injection after the secondary injection) performed after the end of the injection process (primary injection).

  The injection molding machine continuously manufactures a desired molded product by repeating a mold closing process, an injection process, a pressure holding process, a mold opening process, and a product removing process in this order. The pressure holding process is a process in which the molten resin injected and filled in the mold cavity in the injection process shrinks in volume as it cools, so that an appropriate amount of molten resin is replenished in the mold cavity. This is performed by controlling the injection pressure set in multiple stages of injection pressure, tertiary injection pressure, or higher. If the pressure (holding pressure) in the mold cavity at each stage is too low or too high, the quality of the molded product is adversely affected. In general, if the holding pressure is too low, defects such as short shots, sink marks, undersized dimensions, and shrinkage strain will occur. If it is too high, flash, warp, oversized dimensions, cracks, mold release defects, excessive Cause defects such as residual stress.

  For this reason, at the switching position between the injection process (primary injection) and the pressure holding process (secondary injection), the injection servo motor is driven and controlled so that the holding pressure quickly follows the preset secondary injection pressure. It is required to do. That is, in thin molding and precision molding, it is necessary to rapidly reduce the injection pressure at this switching position, and in thick molding, it is necessary to rapidly increase the injection pressure at this switching position. Therefore, it is required to perform these controls stably. The switching position between the injection process and the pressure holding process is a position where the injection servo motor is switched from speed control to pressure control, and is therefore referred to as a VP switching position.

  However, when the drive control of the injection servo motor is switched from speed control to pressure control at the VP switching position, the response of the injection servo motor is delayed, so that the holding pressure reaches a preset secondary injection pressure. It takes a long time, and in thin molded products and precision molded products, the weight variation becomes large and overfilling tends to occur.

  Therefore, in order to eliminate such problems, conventionally, with regard to thin molding and precision molding, when the screw reaches the first set point related to the end of filling when the screw moves forward, the screw is immediately set in advance by the resin pressure. To the second set point, a method of forcibly retreating at a set speed set corresponding to the thin molded product to perform pressure relief (for example, refer to Patent Document 1), and a screw is retracted immediately before VP switching. Thus, a method (for example, see Patent Document 2) has been proposed in which a required pressure waveform is obtained and the quality of a molded product is stabilized.

Japanese Patent No. 3282092 Japanese Patent No. 34044652

  However, the inventions described in Patent Documents 1 and 2 all relate to pressure release at the time of VP switching or immediately before VP switching, and each of the pressure holding controls performed in multiple stages after VP switching is considered at all. Therefore, it is difficult to form a molded article with better dimensional accuracy, and there is room for improvement in this respect. In addition, since the inventions described in Patent Documents 1 and 2 are not considered at all for thick molding, a highly versatile injection molding machine that can be applied to thin molding or precision molding and thick molding. There is room for improvement in this regard.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to respond to drive control of an injection electric servomotor in an injection process and a pressure holding process performed thereafter. It is an object of the present invention to provide an injection molding machine that is capable of molding a high-quality thin article, precision article or thick article with high efficiency.

  In order to solve the above problems, the present invention provides a screw housed in a heating cylinder so as to be rotatable and capable of moving forward and backward, an electric servomotor for injection that drives the screw forward and backward, and an servo amplifier for injection control. An injection molding machine that repeats a mold closing process, an injection process, a pressure holding process, a mold opening process, and a product removal process in this order. A first injection motor drive circuit that drives the electric servomotor for injection so that the position of the screw follows the pattern, and a pressure acting on the screw follows a preset holding pressure setting pattern after VP switching. A second injection motor drive circuit for driving the electric servomotor for injection and a moving speed of the screw in a preset high-speed response pattern And a third injection motor drive circuit that drives the injection electric servo motor so that the pressure acting on the screw during the pressure holding process is set in multiple stages. Each time the set pressure is reached, the control based on the speed command calculated by the third injection motor drive circuit is switched to the control based on the speed command calculated by the second injection motor drive circuit, The driving control of the injection electric servo motor is performed.

  According to this configuration, at each stage in the pressure holding process, drive control of the injection electric servomotor is first executed based on the speed command calculated by the third injection motor drive circuit, and then the pressure acting on the screw Is switched to drive control of the injection electric servomotor based on the speed command calculated by the second injection motor drive circuit when the pressure reaches the pressure setting pressure of each stage. Therefore, it becomes possible to control the drive of the electric servomotor for injection having high responsiveness and followability to the holding pressure setting pressure, and a molded product with high dimensional accuracy can be formed. In addition, by appropriately setting the high-speed response pattern, the injection electric servo motor is moved so as to advance the screw during the drive control of the injection electric servo motor based on the speed command calculated by the third injection motor drive circuit. Since it can be driven or the electric servo motor for injection can be driven to retract the screw, it is possible to form a molded product with high dimensional accuracy not only for thin molding or precision molding but also for thick molding. .

  In the injection molding machine having the above-described configuration, the pressure data and time data input means serving as the basis of the pressure holding setting pattern, and the target position data and time data input means serving as the basis of the high-speed response pattern, It was configured to be equipped with.

  According to such a configuration, the pressure holding setting pattern and the high-speed response pattern can be arbitrarily set by operating each input means, so a wide range of molding conditions can be freely created, and molding of various molded products It can be set as a highly versatile injection molding machine applicable to the above.

  According to the present invention, the injection molding machine having the above-described configuration includes a display unit that displays target position data, pressure data, and time data set by the input unit.

  According to this configuration, the input target position data, pressure data, and time data can be confirmed by the operator as needed, so that the operability of the injection molding machine can be improved.

  Further, in the injection molding machine having the above-described configuration, the screw target position set in the high-speed response pattern at the start of control based on a speed command calculated by the third injection motor drive circuit, It is determined whether the position is ahead or behind the position of the screw in the preceding stage of the control. If the position is ahead, the position speed based on the speed command calculated by the third injection motor drive circuit is determined. When the screw is moved forward by control and is behind, the screw is moved backward by position speed control based on the speed command calculated by the third injection motor drive circuit, and the pressure acting on the screw is When reaching the holding pressure setting pressure at each stage, the screw is moved forward or backward by pressure control based on the speed command calculated by the second injection motor drive circuit. It was.

  According to this configuration, by setting an appropriate target position according to the characteristics of the molded product in the high-speed response pattern, the electric servomotor for injection based on the speed command calculated by the third injection motor drive circuit At the time of drive control, the injection electric servomotor can be driven to advance the screw, or the injection electric servomotor can be driven to move the screw backward. And when the target position which advances a screw is set, since sufficient molten resin can be sent in in a mold cavity after primary injection, a high quality thick article without a surface defect can be fabricated. In addition, when the target position for retreating the screw is set, excessive pressure does not act on the molten resin filled in the mold cavity after the primary injection, so a high-quality thin or precision product without deformation or burrs can be obtained. Can be molded.

  The present invention includes first to third injection motor drive circuits in the calculation means, and each time the pressure acting on the screw during the pressure holding process reaches the pressure setting pressure of each stage set in multiple stages, The control based on the speed command calculated by the third injection motor drive circuit is switched to the control based on the speed command calculated by the second injection motor drive circuit to control the drive of the injection electric servo motor. Therefore, for each holding pressure control performed in multiple stages, it becomes possible to perform drive control of the injection electric servo motor having high responsiveness and followability to the holding pressure setting pressure. Also, depending on the characteristics of the molded product, the screw can be moved forward or backward during the drive control of the injection electric servo motor based on the speed command calculated by the third injection motor drive circuit. Regardless of the type of molded product, a high-quality molded product with high dimensional accuracy can be molded.

It is a figure which shows the control circuit of the injection molding machine which concerns on embodiment. It is a figure which shows the injection apparatus of the injection molding machine which concerns on embodiment. It is a figure which shows the control pattern of the screw suitable for shaping | molding of a thin object and a precision product. It is a figure which shows the control pattern of the screw suitable for shaping | molding of a thick material. It is a figure which shows the state transition in the pressure-holding process of the molding machine which concerns on embodiment.

  Hereinafter, an embodiment of an injection molding machine according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the injection molding machine according to the present embodiment includes a screw 1, a metering electric servomotor 2, a metering motor encoder 3 that detects the rotational position of the metering electric servomotor 2, and an injection The electric servo motor 4, the injection motor encoder 5 that detects the rotational position of the injection electric servo motor 4, and the ball screw mechanism 6 that converts the rotational force of the injection electric servo motor 4 to a straight force and transmits it to the screw 1. And a load cell 7 for measuring the injection pressure and the back pressure acting on the screw 1. The ball screw mechanism 6 includes a screw shaft 6a and a nut body 6b screwed to the screw shaft 6a. As the metering motor encoder 3 and the injection motor encoder 5, an absolute type encoder that outputs an absolute value of the rotational position is used.

  FIG. 2 is a more specific configuration example of the injection molding machine according to the present embodiment. On an injection unit base board (not shown), the head stock 11 and the holding plate 12 face each other with a predetermined interval. These members 11 and 12 are integrally connected via a plurality of tie bars 13. The screw 1 is passed through a screw through hole (not shown) provided in the head stock 11, and an electric servomotor 2 for measurement is connected to the base end side thereof. Further, the distal end side of the screw 1 is accommodated in a heating cylinder 14 fixed to the head stock 11 so as to be rotatable and capable of moving forward and backward. The heating cylinder 14 is provided with a raw material resin supply hole 14a, and the granular raw material resin stored in the hopper 15 is introduced into the heating cylinder 14 through the raw material resin supply hole 14a. The injection electric servo motor 4 is attached to the holding plate 12 and moves the screw 1 and the metering electric servo motor 2 back and forth integrally via the ball screw mechanism 6.

  When the screw 1 is rotationally driven in the heating cylinder 14, raw material resin corresponding to the amount of rotation of the screw 1 is sequentially supplied from the hopper 15 into the heating cylinder 14. The raw material resin supplied into the heating cylinder 14 is subjected to shearing force and frictional force accompanying rotation of the screw 1 and is kneaded and plasticized, while the screw 1 feeds the screw 1 in order (the left side in the figure). ) And is accumulated on the front end side of the heating cylinder 14. In the measurement of the molten resin, as the molten resin accumulates on the tip side of the heating cylinder 14, the electric servo motor 4 for injection is reversely rotated to retract the screw 1, and the screw 1 reaches a predetermined measurement completion position. It ends when After completion of weighing, the electric servomotor for injection 4 is rapidly rotated forward, and the screw 1 is rapidly advanced in the left direction in the figure. Thereby, the molten resin stored in the heating cylinder 14 is injected into a mold (not shown) through the nozzle 14b.

In FIG. 1, a symbol x _ij0 is a position command pattern signal that represents the forward position of the screw 1, a symbol v _ij0 is a speed command pattern signal that represents the forward speed of the screw 1, and a symbol p ₀ is a pressure holding setting pattern signal that represents a pressure holding condition. , code p _H metering motor representing the rotational speed of the high speed response pattern signal, reference numeral v _CG0 metering electric servomotor 2 representing the speed control pattern of the injection electric servomotor 4 executed in the control switching position such as VP switching position These are rotation speed setting pattern signals, and these signals are supplied from the host controller 21. The controller 21 includes an input means 22 for inputting the operating conditions of the injection molding machine including the control conditions of the electric servomotor 2 for metering and the electric servomotor 4 for injection, and the operating conditions of the injection molding machine and the like. Display means 23 for displaying is attached.

The position command pattern signal x _ij0 and the screw position signal x _ijm output from the injection control servo amplifier 36 take a deviation e ₁ in the adder 31 using the screw position signal x _ijm as a feedback signal, and this deviation e ₁ The injection electric servomotor 4 is feedback-controlled based on the above. The screw position signal x _ijm is obtained from the rotation amount from the reference position of the injection electric servo motor 4.

The injection position command PID controller 32 calculates the screw position manipulated variable u ₁ based on the deviation e ₁ , and the speed calculator 33 computes the injection speed command v ₁ based on the manipulated variable u _1. To do. The adder 34 adds a speed addition value signal v _ff obtained by multiplying the speed command pattern signal v _ij0 by a predetermined constant by the amplifier 35 to the injection speed command v ₁ as a feedforward signal, and An injection speed command v ₃ to be given to the electric servo motor 4 is obtained. From the start position of the injection process to the VP switching position, the injection speed command v ₃ calculated by the first injection motor drive circuit is used as the injection speed command v _ij for the injection electric servo motor 4 and the injection control servo amplifier. 36. The injection control servo amplifier 36 controls the rotation of the injection electric servo motor 4 in accordance with the injection speed command v _ij . The rotational position of the injection electric servomotor 4 is supplied to the adder 31 via the injection motor encoder 5 and the injection control servo amplifier 36.

Pressure-holding setting pattern signal _{p 0,} the injection pressure signal _{p ijm} output from the load cell 7, the injection pressure signal _{p ijm} as a feedback signal, the pressure deviation _{e 2} taken in the adder 37, the pressure deviation _{e 2} The injection electric servomotor 4 is feedback-controlled based on the original. PID controller for dwell pressure control 38 calculates the operation amount u ₂ of the pressure control based on the pressure deviation e _2, the speed calculator 39, the injection speed based on the operation amount u ₂ command v ₂ Is calculated. In the pressure-holding process performed after the VP switching, the injection speed command v ₂ calculated by the second injection motor drive circuit is used as the injection speed command v _ij for the injection electric servo motor 4, and the injection control servo amplifier 36. The injection control servo amplifier 36 controls the rotation of the injection electric servo motor 4 in accordance with the injection speed command v _ij .

The high-speed response pattern signal p _H is a signal for increasing the control responsiveness at the control switching position such as the VP switching position. The injection electric servomotor 4 receives the high-speed response pattern signal p at the initial stage of the control switching position. _The speed is controlled according to _H. The circuit supplies the high-speed response pattern signal p _H in the injection control servo amplifier 36, referred to herein as the third injection motor drive circuit.

Injection speed command v _3, switching of the injection speed command v _2, and high-speed response pattern signal p _H is first injection motor drive circuit and the switch 41 is disposed at the connection point of the second injection motor drive circuit, and, This is done by switching the switch 42 arranged at the connection point between the second injection motor drive circuit and the third injection motor drive circuit at an appropriate timing. The switch 41 is switched at the timing when the VP switching position set between the start of the injection process and the end of the pressure holding process is reached. Further, the switch 42 is switched by the speed command calculated by the third injection motor drive circuit each time the pressure acting on the screw 1 reaches a plurality of holding pressure setting pressures set during the holding process. The second is switched to the speed command calculated by the injection motor drive circuit, and is performed at a timing when the pressure acting on the screw reaches a predetermined holding pressure setting pressure. These settings by operating the input unit 22, performed by the input pressure data and time data underlying the holding pressure setting pattern p _0, the target position data and time data underlying the fast response pattern p _H be able to. A timer 24 built in the controller 21 is set based on the input time data. As described above, when the required data is input by operating the input device 22, the setting of the holding pressure setting pattern and the high-speed response pattern can be arbitrarily set, so that a wide range of molding conditions can be freely created. Therefore, it is possible to provide a highly versatile injection molding machine that can be applied to molding various molded products.

The weighing motor rotation speed setting pattern signal v _cg0 is supplied to the weighing control servo amplifier 40, and the weighing control servo amplifier 40 rotates the weighing electric servo motor 2 according to the weighing motor rotation speed setting pattern signal v _cg0. Control.

FIGS. 3A and 3B show a control pattern of the screw 1 suitable for forming a thin object or a precision product. As apparent from FIG. 3A, in this example, the injection pressure is controlled in six stages from the secondary injection pressure to the seventh injection pressure in the pressure-holding step after VP switching. Control step of each subsequent injection pressure, injection pressure control time (e.g., such as secondary pressure timer), fast response pattern p time for control in accordance with _H (e.g., pp2 primary pressure timer or the like), the screw 1 It is regulated by the speed and the pressure acting on the screw 1. In forming the thin and precision products, after the screw 1 reaches the VP switching position, to retract the screw 1 in the control according to the high-speed response pattern p _H, is required to carry out the depressurized quickly. S _2p shown in FIG. 3 (b), the target position of the screw 1 when performing control in accordance with the fast response pattern p _H (hereinafter, this target position, the secondary pressure position, that 3 primary pressure position, and the like. In the case of this example, the screw 1 is set to a position retracted from the VP switching position. Further, s _3p shown in FIG. 3 (b) is the target position of the screw 1 at the time of holding pressure control termination is performed after the control in accordance with a high speed response pattern p _H ends, from the secondary pressure position, etc. s _2p Also, the screw 1 is set at the advanced position. Each of these data is displayed on the display means 23. Therefore, since the operator can confirm these data at any time, the operability of the injection molding machine can be improved.

4 (a) and 4 (b) show examples of control patterns of the screw 1 suitable for molding thick materials and the like. 3 and as is apparent from a comparison between FIG. 4, in this example, the control time of the injection pressure, time for control in accordance with a high speed response pattern p _H, the pressure acting on the speed and the screw 1 of the screw 1 Regarding the setting, it is performed in the same manner as when forming a thin object or a precision product. In molding of thick, etc., after the screw 1 reaches the VP switching position, the control in accordance with the fast response pattern p _H, further to advance the screw 1, instantaneously and stably the pressure in the mold cavity It is necessary to improve. Therefore, in this case, as shown in FIG. 4B, the secondary pressure position or the like s _2p is set in front of the VP switching position. The target position s _3p of the screw 1 at the time of holding pressure control termination is performed after the control in accordance with a high speed response pattern p _H ended is set to the rear than the VP switching position. These data shown in FIGS. 4A and 4B are also displayed on the display means 23.

FIG. 5 shows a transition state of control at each control switching position described with reference to FIGS. 3 and 4. As is clear from this figure, when the molding machine according to the embodiment reaches the VP switching position, the secondary pressure position s _2p is behind the VP switching position (secondary pressure position s _2p ≧ VP switching position). It is determined (secondary pressure position determination) whether it is set or forward (secondary pressure position s _2p <VP switching position). Then, when the determination result is secondary pressure position s _2p ≧ VP switching position, the process proceeds to the control in accordance with the fast response pattern p _H, retracting the screw 1 until the secondary pressure position s _2p, injection pressure Is switched to the control according to the holding pressure setting pattern p ₀ when the secondary pressure reaches the preset secondary pressure. When secondary pressure position determination of the determination is secondary pressure position s _{2p <VP} switching position, the process proceeds to the control in accordance with the fast response pattern p _H, advances the screw 1 until the secondary pressure position s _2p It is allowed, at the stage where the injection pressure reaches the secondary pressure which is set in advance, switching to control in accordance with the holding pressure setting pattern p _0. Thereafter, the control of the injection electric servo motor 4 is repeated in the same procedure until the final holding pressure setting pressure.

Thus, an injection molding machine according to the present embodiment is applicable not VP switching position only, in the switching position and the holding pressure setting of each subsequent injection pressure in the pressure holding step, the speed control according to a high speed response pattern p _H Therefore, it is possible to form a molded product with small weight variation and high dimensional accuracy when molding thin and precision products, and molding a molded product with stable optical characteristics. it can. In addition, by setting a high-speed response pattern, the screw can be controlled to move forward or backward at each stage of the pressure-holding process, so a highly versatile injection molding machine that can be applied to molding various molded products. It can be.

  The present invention can be used for screw acceleration / deceleration control in an injection molding machine.

DESCRIPTION OF SYMBOLS 1 Screw 2 Electric servo motor for measurement 3 Encoder for measurement motor 4 Electric servo motor for injection 5 Encoder for injection motor 6 Ball screw mechanism 6a Screw shaft 6b Nut body 7 Load cell 11 Headstock 12 Holding plate 13 Tie bar 14 Heating cylinder 14a Raw material resin Supply hole 15 Hopper 21 Controller 22 Input means 23 Display means 24 Timer 31, 34, 37 Adder 32, 38 PID controller 33, 39 Speed calculator 35 Amplifier 36 Servo amplifier for injection control 37 Servo amplifier for measurement control 41, 42 switch

Claims (4)

A screw housed in a heating cylinder so as to be rotatable and capable of moving forward and backward, an electric servomotor for injection for driving the screw forward and backward, and a calculation means for calculating a speed command to be given to the servo amplifier for injection control, In an injection molding machine that repeats a mold closing process, an injection process, a pressure holding process, a mold opening process, and a product removal process in this order,
The arithmetic means includes a first injection motor drive circuit that drives the injection electric servomotor so that the position of the screw follows a preset position command pattern;
A second injection motor drive circuit that drives the electric servomotor for injection so that the pressure acting on the screw follows a preset holding pressure setting pattern after VP switching;
A third injection motor drive circuit for driving the injection electric servomotor so that the moving speed of the screw follows a preset high-speed response pattern;
Control based on the speed command calculated by the third injection motor drive circuit every time the pressure acting on the screw during the pressure holding process reaches the pressure setting pressure of each stage set in multiple stages. Is switched to control based on the speed command calculated by the second injection motor drive circuit, and drive control of the electric servomotor for injection is performed.   2. The pressure data and time data input means serving as a basis of the pressure holding setting pattern, and target position data and time data input means serving as a basis of the high-speed response pattern are provided. Injection molding machine.   The injection molding machine according to claim 2, further comprising display means for displaying target position data, pressure data, and time data set by the input means.   At the start of control based on the speed command calculated by the third injection motor drive circuit, the target position of the screw set in the high-speed response pattern is ahead of the position of the screw in the previous stage of the control. When it is forward, the screw is moved forward by position speed control based on the speed command calculated by the third injection motor drive circuit. Is a position speed control based on the speed command calculated by the third injection motor drive circuit, the screw is retracted, and when the pressure acting on the screw reaches the pressure setting pressure of each stage, 2. The injection molding machine according to claim 1, wherein the screw is advanced or retracted by pressure control based on a speed command calculated by the second injection motor drive circuit.

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