DE102014008055B4 - Pressure control device of an injection molding machine - Google Patents

Abstract

Pressure control device of an injection molding machine, comprising:
an injection screw drive unit (30) that drives an injection screw (3);
an injection pressure detecting unit (40) that detects an injection pressure;
a screw speed control unit (31) that controls a moving speed of the injection screw (3) in an injection process;
a pressure control unit (32) that controls an injection pressure in a dwell process;
an injection / dwell process switching unit (50) that switches from the injection process to the dwell process;
a peak pressure detection unit (41) that detects a peak pressure generation timing and a peak pressure value of the injection pressure; and
a peak pressure maintaining control unit that performs such pressure control that the injection pressure from the peak pressure generation timing to a timing at which a condition of completion of the peak pressure maintenance control in the dwell process is satisfied is maintained at the detected peak pressure value;
wherein the pressure control unit (32) performs pressure control in accordance with a set pressure of the dwell process from the time of completion of the peak pressure maintenance control at a time of completion of the dwell process.

Description

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to a pressure control device of an injection molding machine.

Description of the Related Art

A screw-type injection molding machine performs a metering process in which a molten resin is fed into a front end of a heating cylinder by drawing a screw under pressure while the screw is rotated in the heating cylinder, then an injection process in which the molten resin is moved forward the worm is loaded into a mold, and a dwell process.

In the injection process, when the screw is moved forward in accordance with a preset injection movement and a preset injection speed, the molten resin in the heating cylinder is charged into the mold. Then, as the screw advances to an injection / dwell switching position, it is switched from the injection process to the dwell process. In the dwell process, when pressure control is performed according to a preset dwell pressure and a preset dwell time, the molten resin is completely charged into the mold, and the volume shrinkage of the molded product caused by the contraction of the resin is compensated.

Japanese Patent Application Laid-Open JP 2008-74114 A discloses a technique in which a screw is advanced to begin filling a resin into a cavity of a mold, maintaining a screw position of the screw just before the resin is completely filled into the cavity, and a dwell process is selected after the resin has been completely loaded into the cavity (see 5 ).

Japanese Patent Application Laid-Open JP 2-274522 A discloses a technique in which a filling pressure control timer starts a timing operation, and a filling pressure is applied from a time point when an injection pressure reaches a predetermined switching pressure, and a filling pressure control is switched to a dwell control by the time-out of the timer.

Japanese Patent Application Laid-open No. JP 2010-721 A further discloses a technique in which a fill operation is performed by a speed controller until a fill pressure detection value reaches a first set pressure value, the controller is switched from the speed controller to a pressure controller to be controlled at the first set pressure value at a time to the filling pressure detection value becomes the first set pressure value or more, and the control is switched to a dwell control to be controlled at a second set pressure value at a time when a filling speed becomes a set speed or less while the filling operation is being performed by the pressure controller will (see 6 ).

In order to completely fill the resin when a resin flow passage within the mold is narrow or a pouring operation is performed, there is a case where a high peak pressure is necessary in the injection / hold process. However, when the peak pressure excessively increases, there arises the problem that the heating cylinder or the mold is damaged or a burr is generated in the molded product. Thus, there is a need for a technique whereby the resin is fully loaded into the mold without producing the excessive peak pressure.

Here, the performance of filling the resin into the cavity of the mold with the injection pressure is referred to as "filling efficiency". If the filling efficiency is increased, the resin can be fully charged into the mold with a lower injection pressure. In order to achieve a high filling efficiency, it is desirable to perform the pressure control, that is, a peak pressure maintaining control in which a high pressure is maintained within a range in which the pressure does not increase excessively before the filling operation is completed or directly before the filling operation Fulloperation is completed, and then the dwell process to compensate for the volume shrinkage of the molded product is selected.

Further prior art is known from the documents WO 2003/080307 A2 and US 2009/0 315 205 A1 ,

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a pressure control apparatus of an injection molding machine having a pressure control unit controlling an injection pressure in a dwell process, a peak pressure detection unit and a peak pressure maintenance control unit, the peak pressure detection unit detecting a peak pressure generation timing and a peak pressure value of the injection pressure, and the peak pressure maintenance control unit Pressure control executes that the injection pressure from the peak pressure generation timing in the dwell process at the detected peak pressure value is maintained until a condition of completion of the peak pressure maintenance control is satisfied.

A pressure control device of an injection molding machine according to the invention comprises: an injection screw driving unit that drives an injection screw; an injection pressure detection unit that detects an injection pressure; a screw speed control unit that controls a moving speed (feed speed) of the injection screw in an injection process; a pressure control unit that controls an injection pressure in a dwell process; an injection / dwell process switching unit that switches from the injection process to the dwell process; and a peak pressure detection unit that detects a peak pressure generation timing and a peak pressure value of the injection pressure. The pressure control apparatus further includes a peak pressure maintaining control unit that performs pressure control such that the injection pressure from the peak pressure generation timing at a time of completion of the peak pressure maintenance control to which a condition of completion of the peak pressure maintenance control in the dwell process is met is maintained at the peak detected pressure value. Then, the pressure control unit is configured to execute pressure control according to a set pressure of the dwell process from the time of completion of the peak pressure maintenance control to a time of completion of the dwell process.

The condition of completing the peak pressure maintenance control may be at least one of the conditions including: elapse of a period of a predetermined time from the peak pressure generation timing; advancing the worm by a predetermined screw advance amount from the peak pressure generation timing; and a decrease of a screw advance speed up to a predetermined level.

The peak pressure detection unit may detect and detect, as the peak pressure generation timing, a timing at which a pressure change amount per unit time becomes a predetermined change amount or less, or a time at which the screw speed becomes a predetermined speed or less than the peak pressure value, the injection pressure at the peak pressure generation timing detected.

The pressure control unit may perform a pressure control corresponding to the set pressure of the dwell process from an injection / dwell process switching timing to the peak pressure generation timing.

The pressure control unit may perform such control that the screw speed becomes a dwell limiting speed or less from an injection / dwell process switching timing to the peak pressure generation switching timing.

According to the pressure control apparatus of the injection molding machine of the invention, since the peak pressure value is maintained from the peak pressure detection timing, high filling efficiency can be achieved while pressing down the pressure to a pressure value lower than a pressure value at which burr formation occurs. Further, after the condition of completion of the peak pressure maintenance control is satisfied, the process is switched to the dwell process in which the volume shrinkage of the molded product is compensated, so that it is possible to deform the molded product caused by maintaining the peak pressure for a long time to prevent.

BRIEF DESCRIPTION OF THE DRAWINGS

1 FIG. 10 is a schematic configuration diagram illustrating an injection molding machine and a controller that controls the injection molding machine; FIG.

2 Fig. 10 is a block diagram illustrating an embodiment of a pressure control device according to the invention;

3 Fig. 10 is a graph illustrating a transient transition of an injection pressure and a screw position for a casting cycle when a casting operation is performed by the injection molding machine with a pressure control device according to the invention;

4 Fig. 15 is a diagram illustrating a process sequence of a print control executed by the print control apparatus according to the invention;

5 FIG. 12 is a graph illustrating a relationship of an injection pressure and a screw position with a transient forward movement for a casting cycle when a casting operation is carried out by a casting process according to the related art (Japanese Patent Application Laid-Open) JP 2008-74 114 A ); and

6 FIG. 12 is a graph illustrating a relationship of an injection pressure and a screw position with a transient forward movement for a casting cycle when a casting operation is carried out by a casting process according to the related art (Japanese Patent Application Laid-Open) JP H02-274 522 A and Japanese Patent Application Laid-Open JP 2010-721 A ).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

1 FIG. 10 is a schematic configuration diagram illustrating an injection molding machine and a controller that controls the injection molding machine. FIG.

A nozzle 2 is at a front end of a cylinder 1 fixed in the one injection screw 3 is introduced, and a hopper 4 through the cylinder 1 a resin pellet is supplied is at a side part of a rear end of the cylinder 1 attached. The injection screw 3 is driven in the axial direction thereof by an injection servo motor M1 serving as a driving means for driving the injection screw 3 in the axial direction thereof, and a conversion mechanism 7 which converts a rotational movement of a transmission mechanism and a ball screw / nut into a linear motion and thus performs an injection and control of a back pressure. Furthermore, the injection screw 3 turning from a servomotor 2 acting as a rotary drive means for rotating the injection screw 3 serves, and a transmission mechanism 6 driven by a belt, a drive pulley and the like.

The injection servo motor M1 and the screw rotation servomotor M2 are equipped with a position / velocity detector Penc1 and a position / velocity detector Penc2, respectively, which detect their rotational position / velocity. The position (the position in the screw axis direction) and the moving speed (the injection speed) of the injection screw 3 and the rotational speed of the injection screw 3 can be detected by the position / speed detectors Penc1 and Penc2. Further, a pressure sensor 5 , such as As a pressure gauge, provided to the injection screw 3 applied pressure of the molten resin in the screw axis direction to detect.

A PMC CPU 17 is with a ROM 18 , which stores a sequence program for controlling a work flow of the injection molding machine, and a RAM 19 which is used to temporarily store calculation data. A CNC CPU 20 is with a ROM 21 , which stores an automatic work program for complete control of the injection molding machine, and a RAM 22 which is used to temporarily store calculation data.

The servo CPU 15 is with a ROM 13 which stores an exclusive servo control program for executing processes of a position loop, a velocity loop, and a current loop, or a RAM 14 which is used to temporarily store data. The servo CPU 15 is with a servo amplifier 12 which controls the worm rotary servomotor M2 based on the command from the servo CPU 15 drives, and a servo amplifier 11 of the injection servomotor M1 based on the command from the servo CPU 15 drives, connected.

As described above, the servomotors M1 and M2 are equipped with the position / speed detectors Penc1 and Penc2, respectively. The output of the position / speed detectors Penc1 and Penc2 is sent to the servo CPU 15 confirmed. The servo CPU 15 results from the CNC CPU based on the motion command 20 to the respective axes (the injection servo motor M1 and the worm rotation servomotor M2) and the detection position and the detection speed, which are returned from the position / speed detector Penc1 and the position / speed detector Penc2, a position / speed feedback control and further executes a feedback control to the drive states of the servo amplifier 11 and 12 to control.

Further, a register of the present position is provided to the forward moving position (the axial position) of the injection screw 3 by the position feedback signal from the position / velocity detector Penc1, whereby the screw position can be detected from the register of the present position. Further, the resin pressure (the resin pressure applied to the screw) becomes a detection signal (an analog signal) of the pressure sensor 5 from the A / D converter 16 is converted into a digital signal, the servo CPU 15 fed.

An LCD / MDI (device for manually entering data with liquid crystal display) 25 is with a bus 26 via an LCD display circuit 24 connected. Further, a RAM configured as a non-volatile memory 23 for storing pouring data with the bus 26 connected. The RAM 23 For storing pouring data, pouring conditions involved in the injection molding process as well as various setting values, parameters, macro variables and the like are stored.

With the configuration described above, the PMC CPU controls 17 the workflow of the entire injection molding machine and distributes the CNC CPU 20 the movement command with respect to the servomotors M1 and M2 of the respective axes based on the work program of the ROM 21 and in the RAM 23 casting condition stored for storing pour data. Furthermore, the servo CPU performs 15 a so-called digital servo process by performing a servo control such. A position control loop, a speed control loop and a current control loop based on the movement command distributed to the respective axes (the injection servomotor M1 and the screw rotation servomotor M2) and the feedback signal of the position / velocity detectors Penc1 and Penc2, as in the related art.

An embodiment of the pressure control device of the injection molding machine according to the invention is made using a block diagram 2 described.

The pressure control device of the injection molding machine comprises an injection screw drive unit 30 that the injection screw 3 drives, an injection pressure detection unit 40 detecting the injection pressure, a screw speed control unit 31 that determines the speed of movement of the injection screw 3 In the injection process controls, a pressure control unit 32 controlling the injection pressure in the dwell process, an injection / dwell process switching unit 50 , which switches a process from the injection process to the dwell process, a peak pressure detection unit 41 , which detects the peak pressure generation timing and the peak pressure value of the injection pressure, and a peak pressure maintenance control unit 42 ,

The worm speed control unit 31 receives a speed command from one of the peak pressure maintenance control unit 42 (the contact point B) and the pressure control unit 32 (the contact point A), sends a torque command to the injection screw drive unit 30 (the servo amplifier 11 and 12 ) and drives the injection servomotor M1.

The peak pressure detection unit 41 detects the peak pressure generation timing and the peak pressure from a change value of the injection detection unit 40 detected injection pressure. That of the peak pressure detection unit 41 detected peak pressure is sent to the peak pressure maintenance control unit 42 output.

The peak pressure maintenance control unit 42 performs pressure control by controlling the drive torque of the injection screw drive unit 30 so that the injection pressure at that of the peak pressure detection unit 41 detected peak pressure value in a way that the speed command to the worm speed control unit 31 is transmitted by the switch contact point B is maintained from the peak pressure generation timing until a time when the condition of completion of the peak pressure maintenance during the dwell process is satisfied.

In the meantime, the print controller receives 32 the injection pressure from the injection pressure detection unit 40 and sends the speed command through the switching contact point A to the worm speed control unit 31 from the injection / dwell process switching timing by the injection / dwell process switching unit 50 at the peak pressure generation timing and from the timing of completion of the peak pressure maintenance control at the time of completion of the dwell process, whereby the pressure control is executed according to the set pressure of the dwell process.

Next, an injection pressure control performed by the pressure control device of the injection molding machine according to the invention will be explained with reference to FIG 3 described.

In order to reduce excessive peak pressure and achieve high filling efficiency within a predetermined injection pressure during a filling operation, it is desirable to maintain the pressure control (that is, the peak pressure maintaining control) at which the peak pressure generated at an injection / dwell process switching time is maintained at the pressure before the filling is completed or just before the filling is completed, as described above, and then switch to the dwell process, in which the volume shrinkage of the molded product is compensated.

3 FIG. 10 is a graph illustrating a transient transition of the injection pressure and the screw position for one pour cycle when a pouring operation is performed by the injection molding machine with the pressure control device according to the invention.

In the pressure control according to the pressure control apparatus of the invention, when the speed control in the injection process is switched to the pressure control in the dwell process, the injection pressure becomes a peak value, as in FIG 3 1, the peak pressure is maintained until the condition of completion of the peak pressure maintenance control is satisfied, and the pressure control by the controller becomes 10 out 1 according to the set pressure of the dwell process from the time of completion of the peak pressure maintenance control to the time of completion of the dwell process.

In the pressure control apparatus of the injection molding machine of the invention, since the peak pressure value is maintained from the peak pressure detection timing, as in FIG 3 shown to achieve a high filling efficiency while the pressure is reduced to a pressure value which is lower than the pressure value at which burr formation occurs. After the condition of completion of the peak pressure maintenance control is satisfied, the pressure control is executed according to the set pressure of the dwell process for compensating for the volume shrinkage of the molded product. Consequently, the deformation of the molded product caused by maintaining the peak pressure for a long period of time can be prevented.

<Peak pressure detection unit>

The injection pressure may be determined by detecting the force acting on the screw in the axial direction by means of a force detector, such as a force detector. Of a pressure gauge, can be obtained by detecting the resin pressure in the injection cylinder by means of a resin pressure sensor or by detecting the driving torque of the injection screw driving unit 30 be obtained. The injection pressure can also be obtained by detecting the hydraulic pressure when the injection screw is driven by the hydraulic pressure.

The peak pressure detection unit 41 detecting the peak value of the injection pressure detects a pressure change amount per unit time and a time point (time of maximum value generation) at which the pressure change amount per unit time changes from a state of increase to a state of decrease than the peak pressure generation time point. At this time, since the timing of detection of the peak pressure generation is the timing at which the pressure change amount per unit time switches to a state of decrease, the timing of detection of the peak pressure generation is one sample time later than the actual timing of generation of the peak pressure and becomes Pressure value at the time of peak pressure detection, a value that is smaller than the actual peak pressure. However, since a time difference between the actual time of the peak pressure generation and the time of peak pressure generation detection is small and a difference between the actual peak pressure value and the pressure value at the time of peak pressure detection is small, the pressure value at the time of detection of peak pressure generation may be instead of maintaining the detected peak pressure value.

Alternatively, the peak pressure detection unit 41 detect a timing at which the pressure change amount per unit time near the time of peak pressure generation becomes a predetermined change amount or less than the peak pressure generation timing. The peak pressure detection unit 41 detects the timing shortly before the timing of the maximum pressure value generation as the peak pressure generation timing when the predetermined change amount is a positive value, and detects the timing shortly after the timing of the maximum pressure value generation as the peak return generation timing when the predetermined change amount becomes a negative value.

Alternatively, the peak pressure detection unit 41 a timing at which the screw speed becomes a predetermined speed or less than the peak pressure generation timing. This is because the flow of the resin into the cavity decreases around the time when the resin is completely filled, whereby the amount of injection pressure increase per unit time is substantially proportional to the screw speed, and the peak pressure generation timing is therefore substantially equal to one time is at which the screw speed becomes zero.

At this time, the screw speed changes according to the timing of the peak pressure generation depending on the type of the resin or the mold of the molded product, so that the above predetermined speed is determined in advance according to the type of the resin or the mold of the molded product and by the operator can be determined.

<Peak pressure retention control unit>

The peak pressure maintenance control unit 42 For example, the pressure control may be performed by controlling the screw speed so as to maintain the injection pressure at the peak pressure, and may control the pressure by controlling the driving torque of the injection screw driving unit 30 To run. Further, there is a case where the worm does not stop completely in the axis direction but moves forward to maintain the pressure during the peak pressure maintenance control. The forward movement speed at this time is changed in response to the kind of the resin, the shape of the molded product, or the state of the resin loaded in the mold. Further, the pressure control from the time of switching of the injection / dwell process to the peak pressure generation timing corresponding to the set pressure of the dwell process may be executed, the control of stopping the screw may be performed, or the control of the change of the screw speed may be performed at a predetermined speed ,

The condition of completing the peak pressure maintenance control may be the elapse of a predetermined time from the time pressure of the peak pressure generation (which is in 1 shown control device 10 has a time measuring unit), or a forward movement of the worm by a predetermined amount of worm forward movement from the peak pressure generating timing. The extent of forward movement of the injection screw 3 can be measured by using the position detection signal supplied from the position / velocity detector Penc1 attached to the injection servomotor M1 to the servo CPU 15 is fed back.

Alternatively, the condition of completing the peak pressure maintenance control may be a decrease in the screw advance speed to a predetermined level. The forward movement speed (feed speed) of the injection screw 3 can be measured by using the speed detection signal supplied from the position / speed detector Penc1 attached to the injection servomotor M1 to the servo CPU 15 is fed back. This is because, in a state where the filling operation is not completed, the resin flows into the cavity of the mold so that the screw speed becomes high to maintain the peak pressure, and the flow of the resin into the cavity decreases Completion of the filling process approaches, so that the screw speed to maintain the peak pressure is smaller. Since the peak pressure maintaining control is completed after the screw advancing speed decreases to a predetermined level, the peak pressure is maintained until the filling operation is substantially completed. Then, the pressure control is executed on the basis of the set pressure of the dwell process in which the volume shrinkage of the molded product is compensated.

4 FIG. 15 is a diagram illustrating a process sequence of the print control executed by the print control apparatus according to the invention. The following describes this process according to the steps.

[Step SA01] The injection process is executed.

[Step SA02] Switching of the injection process to the dwell process is carried out.

[Step SA03] The pressure control is executed so that the pressure becomes the set pressure.

[Step SA04] It is determined whether or not the peak pressure is generated, and the routine proceeds to Step SA05 when the peak pressure is generated (YES), or the routine returns to Step SA03 if the peak pressure is not generated ( NO).

[Step SA05] The control is executed so that the peak pressure is maintained.

[Step SA06] It is determined whether a predetermined time elapses from the peak generation timing, and the routine proceeds to step SA07 when a predetermined time elapses (YES), or the routine returns to step SA05 if a predetermined time does not elapse (FIG. NO).

[Step SA07] The pressure control is executed so that the pressure becomes the set pressure.

[Step SA08] It is determined whether the dwell process is completed or not, and the routine proceeds to step SA09 when the dwell process is completed (YES), or the routine returns to step SA017 if the dwell process is not completed ( NO).

[Step SA09] The measuring process and the pressure reducing process are executed and then this process is finished.

Claims (5)

Pressure control device of an injection molding machine, comprising: an injection screw drive unit ( 30 ), which is an injection screw ( 3 ) drives; an injection pressure detection unit ( 40 ) detecting an injection pressure; a screw speed control unit ( 31 ), which has a speed of movement of the injection screw ( 3 ) in an injection process; a print control unit ( 32 ) controlling an injection pressure in a dwell process; an injection / dwell process switching unit ( 50 ) switching from the injection process to the dwell process; a peak pressure detection unit ( 41 ) detecting a peak pressure generation timing and a peak pressure value of the injection pressure; and a peak pressure maintenance control unit ( 42 ) that performs such pressure control that the injection pressure from the peak pressure generation timing to a timing at which a condition of completion of the peak pressure maintenance control in the dwell process is satisfied is maintained at the detected peak pressure value, the pressure control unit ( 32 ) performs a pressure control according to a set pressure of the dwell process from the time of completion of the peak pressure maintenance control at a time of completion of the dwell process. The pressure control apparatus of the injection molding machine according to claim 1, wherein the condition of completion of the peak pressure maintenance control is at least one of the conditions including: elapse of a predetermined time from the time of peak pressure generation; Forward movement of the screw ( 3 with a predetermined amount of screw advance from the peak pressure generation time; and decreasing a screw advancing speed to a predetermined level. The pressure control apparatus of the injection molding machine according to claim 1, wherein the peak pressure detecting unit (10) 41 ) as the peak pressure generation timing detects a timing at which a pressure change amount per unit time becomes a predetermined change amount or less, or a time when the screw speed becomes a predetermined speed or less, and as the peak pressure value detects the injection pressure at the detected peak pressure generation timing. Pressure control device of the injection molding machine according to one of claims 1 to 3, wherein the pressure control unit ( 32 ) performs a pressure control according to the set pressure of the dwell process from a timing of switching the injection / dwell process to the peak pressure generation timing. Pressure control device of the injection molding machine according to one of claims 1 to 3, wherein the pressure control unit ( 32 ) performs such control that the screw speed becomes a dwell limiting speed or less from a timing of switching of the injection / dwell process to the peak pressure generation timing.

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