JP2000238092A - Method for controlling injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress unevenness of resin densities and screw positions by pressure feedback controlling while rotatably drive controlling screws in the step of plasticizing and resin feeding, pressure feedback controlling along a time base in the step of metering a resin amount, and setting a retracting limit specified value. SOLUTION: In the step of plasticizing and feeding resin of a first stage of step of plasticizing and metering, a screw rotational speed is feedback controlled to pressure feedback control the screw 2 while rotatably drive controlling the screw 2 by feedback controlling a screw rotational speed. Subsequently, in the step of metering a resin amount of a second stage, the screw 2 is pressure feedback controlled along a time base in the state the screw 2 is stopped. Further, a retracting limit specified value for specifying a final screw retracting limit position in the step is set, a preset position of the screw 2 is monitored even during a period of the step of metering the resin amount, and controlled so that the screw 2 may not exceed the position specified by the retracting limit specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an injection molding machine of an in-line screw type, and more particularly to a method for controlling a plasticization / metering process in an injection molding machine suitable for stabilizing a resin density. Things.

[0002]

2. Description of the Related Art In an injection molding machine of the in-line screw type, as is well known, a plasticized molten resin is stored at the tip end of the screw by rotation and retreat of the screw, and plasticization and measurement are performed. ing.

Conventionally, the above-described plasticizing / metering process is generally performed by setting a screw stroke from a plasticizing / metering start position to a plasticizing / metering completion position, and using a hydraulic cylinder as an injection drive source. The screw rotation speed and back pressure are set in accordance with the setting conditions, and the screw rotation speed and back pressure are controlled according to these setting conditions. If the injection drive source is a servomotor (electric servomotor), the screw By setting the rotation speed and the screw tip resin pressure, the screw rotation speed and the pressure applied to the screw by the resin are controlled according to these setting conditions. Then, the screw rotation operation and the retreat operation are stopped to terminate the plasticizing and measuring process.

[0004] As described above, the conventional plasticizing and measuring process is as follows.
When the screw reaches the plasticizing / metering completion position, the screw rotation and retreat operations are stopped, so that the plasticizing / metering completion position is always constant. However, conventional plasticization
In the weighing operation, pressure feedback control is performed with the screw constantly rotating from the beginning to the end of the plasticization and weighing process, so the load cell (force sensor (converted to pressure value) is used for pressure feedback control. Do);
Hereinafter, the pressure measurement value detected by the pressure sensor is a value in which the propulsion force (pressure) due to the screw rotation is added. The propulsion force (pressure) due to the screw rotation is likely to fluctuate due to fluctuations in the frictional force between the screw and the resin or between the resin and the inner surface of the heating cylinder. Even if pressure feedback control is performed so as to match, if the propulsion force (pressure) due to screw rotation fluctuates, the actual pressure of the resin will show fluctuations, and as a result, the resin density of the measured and stored molten resin will vary. There was a problem.

Therefore, the applicant of the present application has made the following in order to reduce the above-mentioned variation of the molten resin measured and stored as much as possible.
Japanese Patent Application No. 9-300764 proposed a control method of a plasticizing and measuring process in an in-line screw type injection molding machine. In other words, in this prior application, the plasticizing / measuring process, which was conventionally simply referred to as the measuring process, is performed by melting and plasticizing the resin and feeding it to the screw tip side.
The resin feeding process and the resin amount measuring process for retreating the screw to the metering completion position (retreat limit position) finally have two steps.
In the plasticization / resin feeding process, pressure feedback control is performed on the screw while the screw is rotationally controlled by feedback-controlling the screw rotation speed, and the amount of resin measured following the plasticization / resin feeding process is measured. In the stroke, pressure feedback control is performed on the screw along a time axis while the rotation of the screw is stopped. As described above, in the resin amount measurement process, which is the second stage of the plasticization and measurement process, the pressure feedback control for a predetermined time is performed without being affected by the driving force (pressure) due to the screw rotation. Therefore, the control of the resin pressure can be performed in a very good state, whereby the variation in the resin density of the molten resin measured and stored is reduced as much as possible.

[0006]

SUMMARY OF THE INVENTION The aforementioned Japanese Patent Application No. 9-300 is disclosed.
According to the technology proposed in No. 764, in the second stage of the plasticizing and measuring process, the resin amount measuring process performs pressure control for a certain period of time (pressure control along the time axis) with the screw rotation stopped. By doing so, the variation in the resin density of the molten resin measured and stored is reduced as much as possible. If the behavior of the resin is stable, the resin amount measurement process (plasticization and measurement) The variation of the screw position (screw retreat limit position) at the completion of the stroke) is also relatively small. However, since the resin amount measurement process of the prior application is a pressure feedback control along a time axis, the screw retreat limit position cannot be controlled to be constant, and plasticity is unexpectedly changed due to a change in resin behavior or the like. There is a possibility that the screw position (the screw retreat limit position) at the time of completion of the conversion / measurement process will have a large variation.

In other words, in the technique proposed in Japanese Patent Application No. 9-300764, the variation range of the screw position (the screw retreat limit position) at the time of completion of the plasticizing and measuring process is reduced, or the variation is reduced. No consideration has been given to the suppression, and depending on the molding conditions,
Screw position at the time of completion of plasticization and weighing process (screw retraction limit position) while suppressing variation in resin density
In some cases, it is required to suppress the variation of the above and stabilize the measuring volume.

[0008] The present invention has been made in view of the above points,
The purpose of this control is to control the measurement process in an in-line screw type injection molding machine, which can reduce the variation in resin density and the screw position at the completion of the plasticization and measurement process. It is to provide a method.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a screw rotation drive source which drives a screw by rotating the screw in a heating cylinder so that the screw can move forward and backward. In a control method of an in-line screw type injection molding machine having an injection drive source for driving a screw forward and backward, a screwing speed is fed back to a plasticizing / resin feeding process which is a first stage of a plasticizing / metering process. This is performed by performing pressure feedback control on the screw while controlling the screw to rotate while controlling the screw, and is the second stage of the plasticization and measurement process, which is the second stage of the plasticization and measurement process following the plasticization and resin feeding process. The stroke is performed by performing pressure feedback control on the screw along the time axis while the screw rotation is stopped. In both cases, a retraction limit specified value that defines the final screw retraction limit position in the resin amount measurement process is set, and the current position of the screw is monitored even during the resin amount measurement process, and during the resin amount measurement process, The screw is controlled so as not to exceed the position defined by the backward limit specified value.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a main part configuration of an in-line screw type injection molding machine according to one embodiment of the present invention. The mechanism shows only a rotary drive system and a forward / reverse drive system of the screw, and the control system is plasticized. -Only the weighing system is shown.

In FIG. 1, reference numeral 1 denotes a heating cylinder, 2 denotes a screw arranged in the heating cylinder 1 so as to be rotatable and forward / backward, and 3 denotes a screw rotation driving source (plasticizing / driving) for driving the screw 2 to rotate. Servo motor for screw rotation as a resin feeding drive source), 3a is an output pulley of the servo motor 3, 4 is a timing belt for transmitting the rotation of the output pulley 3a to a pulley 5 connected to the rear end of the screw 2, 6 is Servo motor for injection as an injection drive source,
6a is an output pulley of the servo motor 6, and 7 is an output pulley 6.
rotate the rotation of a → the pulley 8 of the linear motion conversion mechanism 8
a is a timing belt to be transmitted to a, 8 is a rotation → linear motion conversion mechanism composed of a ball screw mechanism for converting the rotary motion into a linear motion and transmitting the linear motion to the screw 2, and 9 is a detection of the rotation of the servomotor 3 for screw rotation. An encoder 10 is a load cell for detecting the pressure applied to the screw 2, and 11 is an encoder for detecting the rotation of the servomotor 6 for injection. In the present embodiment, the plasticizing / metering servomotor 3, the timing belt 4, and the pulley 5 move forward and backward integrally with the screw 2.

Reference numeral 12 denotes a plasticizing / measurement condition setting storage unit embodied by a function of a microcomputer or the like, which includes a screw rotation speed setting storage unit 13 and a resin pressure condition setting storage unit 14. A plasticizing / metering control unit 15 is also embodied by the function of the microcomputer, and includes a screw rotation speed feedback control unit 16 and a pressure feedback control unit 17. Reference numeral 18 denotes a servo amplifier for driving and controlling the servo motor 3 for screw rotation, and reference numeral 19 denotes a servo amplifier for driving and controlling the servo motor 5 for injection.

The screw rotation speed setting storage unit 13 of the plasticizing and measuring condition setting storing unit 12 stores the first plasticizing and measuring process.
The control condition of the screw rotation speed in the plasticizing / resin feeding process, which is the stage, is stored in a rewritable manner. In this embodiment, the starting position of the plasticizing / metering (starting position of the plasticizing / resin feeding process) And a predetermined and fixed number of set screw rotation speeds (rpm) from the time point till the position where the plasticizing / resin feeding process is completed.

The resin pressure condition setting storage unit 14 of the plasticizing / metering condition setting storage unit 12 stores a plasticizing / resin feeding process and a resin amount measuring process which is the second stage of the plasticizing / metering process. , Resin pressure control conditions are stored. In the present embodiment, the resin pressure condition setting storage unit 14 stores a predetermined and fixed number of times from the start position of the plasticizing / metering (start position of the plasticizing / resin feeding process) to the end position of the plasticizing / resin feeding process. Set resin pressure and plasticization
The set resin pressure set in two stages along the time axis from the completion of the resin feeding process to the completion of the resin amount measurement process, and the retreat limit stroke width of the screw in the latter half of the resin amount measurement process (that is, the resin The backward limit specified value that defines the screw backward limit position from the start position of the latter half of the quantity weighing process (this is measured and recognized for each shot) is stored.

The screw speed feedback control unit 16 of the plasticizing / metering control unit 15 outputs the output A of the encoder 11.
3 and monitor the measured screw position obtained from the output A1 of the encoder 9 while comparing the setting data stored in the screw speed setting storage unit 13 with the measured screw speed data obtained from the output A1 of the encoder 9. A control signal is generated so that the section from the start position (the start position of the plasticizing / resin feeding process) to the completion position of the plasticizing / resin feeding process has the set screw rotation speed, and the control signal is generated. Output to the servo amplifier 18 to drive and control the servo motor 3 for screw rotation. The rotation of the servo motor 3
The output is transmitted to the screw 2 via the output pulley 3a, the timing belt 4, and the pulley 5, whereby the screw 2 is rotationally driven by feedback control so as to reach the set rotational speed.

The pressure feedback control unit 17 of the plasticizing / metering control unit 15 monitors the actual measured screw position obtained from the output A3 of the encoder 11 during the plasticizing / resin feeding process, and also controls the resin pressure condition setting storage unit 14.
And the output A2 of the load cell 10
The section from the start position of the plasticization / metering (start position of the plasticization / resin feed process) to the end position of the plasticization / resin feed process is set by comparing the measured pressure data obtained from A control signal is generated so as to be a resin pressure, and is output to the servo amplifier 19 to control the drive of the injection servomotor 6. The rotation of the servo motor 6
The rotation is transmitted to the pulley 8a of the rotation → linear motion conversion mechanism 8 via the output pulley 6a and the timing belt 7, whereby the screw 2 detected by the load cell 10 is
The screw 2 is subjected to forward / backward drive control (including stop control) by feedback control so that the pressure applied to becomes the set resin pressure.

Further, the pressure feedback control unit 17
In the first half of the resin amount measurement process, the setting data stored in the resin pressure condition setting storage unit 14 and the load cell 1
0 with the measured pressure data obtained from the output A2,
A control signal is generated such that the period from the completion of the plasticization / resin feeding process to the completion of the first half of the preset resin amount measurement process is equal to the set resin pressure. 19, which gives
Feedback control is performed such that the pressure applied to the screw 2 detected by the load cell 10 becomes the set resin pressure.

Further, the pressure feedback control unit 17
In the latter half of the resin amount measurement process, the setting data stored in the resin pressure condition setting storage unit 14 and the load cell 1
0 with the measured pressure data obtained from the output A2,
A control signal is generated so that the period from the completion of the first half of the resin amount measurement process to the completion of the second half of the preset resin amount measurement process becomes the set resin pressure, and this is servo-controlled. Output to the amplifier 19, which
Feedback control is performed such that the pressure applied to the screw 2 detected by the load cell 10 becomes the set resin pressure. Further, in the latter half of the resin amount measurement process, the pressure feedback control unit 17 monitors the actually measured screw position obtained from the output A3 of the encoder 11, and completes the first half of the resin amount measurement process (resin amount measurement). At the start of the latter half of the stroke), the measured screw position information measured by the encoder 11 is recognized, and the resin pressure condition setting storage unit based on the actually measured screw position at the start of the latter half of the resin amount measurement process is set. 1
The screw 2 is controlled so that the screw 2 does not exceed the screw retreat limit position defined by the screw retreat limit stroke width in the latter half of the resin amount measurement process stored in the screw 4.

FIG. 2 is a diagram showing an example of the pressure feedback control unit 17 of the plasticizing / metering control unit 15. In FIG. 2, the same components as those in FIG.

In FIG. 2, reference numeral 21 denotes a deviation detecting unit, and 22 denotes a PI for performing PID calculation for pressure feedback control.
D operation unit, 23 is an output conversion unit that converts the output of the PID operation unit 22, 24 is a speed control pattern creation unit, 25 is a deviation counter, and 26 is a speed that generates and outputs a control output value for speed control. A control command value output unit 27 switches between the output of the output conversion unit 23 and an output of the speed control command value output unit 26 for output.
7 is converted into an analog value, and a pressure command value is set as an apparent speed command value (the control value given to the servo motor 6 is:
Even in the case of the pressure feedback control, it becomes a speed control value from the viewpoint of the servo motor 6).

In the plasticizing / resin feeding process, the deviation detecting unit 21 supplies the plasticizing / resin from the start of the plasticizing / resin feeding process to the end of the plasticizing / resin feeding process. Pressure setting value p of feeding stroke
1 and a measured pressure value px obtained by performing an arithmetic operation on the output A2 of the load cell 10 are supplied at appropriate sampling intervals. Further, in the first half of the resin amount measurement process, the deviation detecting unit 21 supplies the resin amount between the arrival of the start command of the first half of the resin amount measurement process and the arrival of the end command of the first half of the resin amount measurement process. The pressure set value p2 in the first half of the weighing process and the pressure measurement value px obtained by performing arithmetic processing on the output A2 of the load cell 10 are supplied at appropriate sampling intervals. In the latter half of the resin amount measuring process, the deviation detecting unit 21 supplies the resin amount from the arrival of the start command of the latter half of the resin amount measuring process to the arrival of the end command of the latter half of the resin amount measuring process. The pressure set value p3 in the latter half of the weighing process and the pressure measurement value px obtained by performing arithmetic processing on the output A2 of the load cell 10 are supplied at appropriate sampling intervals.

The deviation detector 21 calculates the difference between the pressure set value p1 (or p2 or p3) and the measured pressure value px, and calculates the difference (deviation of pressure) e as PI
Output to the D operation unit 22. The PID calculation unit 22 performs a calculation process for performing feedback control based on a PID (proportional / integral / differential) operation using the input deviation e.
That is, the arithmetic processing by the following equation is executed, and the pressure measurement value px
Is calculated so as to match with the pressure set value p1 (or p2 or p3). In the following equation, P
i, Ii, and Di are PID constants.

[0023]

(Equation 1)

The output converter 23 converts the manipulated variable u output from the PID calculator 22 from the manipulated variable u to the control output value y2.
According to the output conversion formula (2), that is, y2 = g (u), a control output value y2 is obtained by arithmetic conversion processing, and this is output to the switch unit 27.

The switch unit 27 unconditionally selects the control output value y2 from the output conversion unit 23 during the plasticizing / resin feeding process and the first half of the resin amount measurement process, and sets the D / A conversion unit 28. Is controlled to output to

In the speed control pattern creating section 24, the actually measured screw position at the start of the latter half of the resin amount measuring process in the latter half of the resin amount measuring process is set as a starting point, and the speed is stored in the resin pressure condition setting storing portion 14. Amount of resin set at each position s1 along a screw stroke axis (position axis) ending at the screw retraction limit regulated position defined by the screw retraction limit stroke width in the latter half of the measured resin quantity measurement process Speed set value v in the latter half of the weighing process
1, a speed control pattern in the latter half of the resin amount measurement process is generated and output to the deviation counter 25. Further, the current screw position information in the latter half of the resin amount measuring process based on the output A3 of the encoder 11 is input to the deviation counter 25.

Based on the speed control pattern information along the position axis from the speed control pattern creating section 24 and the current screw position information, the deviation counter 25 responds to the current screw position in the latter half of the resin amount measurement process. The speed deviation is output to the speed control command value output unit 26. The speed control command value output unit 26 performs almost the same output conversion calculation processing as the output conversion unit 23, and outputs the calculation processing result to the switch unit 27 as a control output value y1.

In the latter half of the resin amount measurement process, the switch unit 27 controls the control output value y2 from the output conversion unit 23.
And the control output value y1 from the speed control command value output unit 26 are constantly monitored to determine the magnitude relationship between the two, y1 and y2. When y1> y2, the output from the output conversion unit 23 The control output value y2 is output to the D / A converter 28, and y1 ≦ y
When the value becomes 2, the control output value y1 from the speed control command value output unit 26 is output to the D / A conversion unit 28.

FIG. 3 is an explanatory view showing the relationship between the above-mentioned control output values y1 and y2, showing the state of the latter half of the resin amount measuring step. The horizontal axis in FIG. 3 shows the screw stroke (screw position). The vertical axis in the figure indicates the speed.

As shown in FIG. 3, pressure feedback control (pressure feedback control along the time axis) in the first half of the resin amount measurement process over a predetermined period of time.
Is completed, pressure feedback control (pressure feedback control along the time axis) in the latter half of the resin amount measurement process over a predetermined period of time is started. In the pressure feedback control along the time axis of the latter half of the resin amount measurement process, feedback control giving priority to pressure is performed so that the measured pressure value px matches the pressure set value p3 of the latter half of the resin amount measurement process. The output converter 23 outputs a control output value y2 for controlling the measured pressure value px to match the set pressure value p3. This control output value y2 is given as an apparent speed command value to the servo motor 6, but is a control output for pressure priority control, so as shown in FIG. , A certain variation range S.

On the other hand, the control output value y1 output from the speed control command value output section 26 is for defining the screw retreat limit position in the latter half of the resin amount measurement process, and as shown in FIG. Except for the end position section of the latter half of the resin amount measurement process along the screw position, it is set to take a value sufficiently larger than the control output value y2, and the end position section of the latter half of the resin amount measurement process Depends on the variation of y2 due to the variation range S of the control output value y2 before the completion of the latter half of the resin amount measuring process (that is, the time of the latter half of the predetermined resin amount measuring process is determined in advance). Before the time elapses), the control output value y1 has its deceleration pattern characteristic determined so that y1 ≦ y2.

Therefore, the holding pressure feedback control unit 1
When y1 ≦ y2 before the time of the second half of the predetermined resin amount measurement process elapses, the switch unit 28 of the switch 7 outputs the output to the D / A conversion unit 28 to the control output value y2.
To the control output value y1, whereby the screw retreat limit position in the latter half of the resin amount measurement process is set to the predetermined position defined by the deceleration pattern characteristic of the control output value y1 (as shown in FIG. 3, The control output switching control is performed so as to be a screw retreat limit position defined by the retreat limit stroke width from the start position of the latter half of the resin amount measurement process.

If y1.ltoreq.y2 is not satisfied in the second half of the predetermined resin amount measuring step, that is, y1 is not reached until the end of the second half of the resin amount measuring step. If> y2, the switch unit 27 continues to select the control output value y2 as the output to the D / A conversion unit 28 until the end. When the switch unit 27 continues to output the control output value y2 to the end in this way, the screw position (screw retreat limit position) at the time of completion of the latter half of the resin amount measurement process is the screw retreat limit position described above. Before or the screw retreat limit position.

Here, when pressure feedback control is performed along the time axis of the second half of the resin amount measurement process without performing the control as in the present embodiment, that is, during the second half of the resin amount measurement process, When pressure feedback control is performed along the time axis without restricting the retreat limit position, the screw position at the completion of the second half of the resin amount measurement process when good plasticization and measurement are being performed ( Assuming that the average value of the variation of the screw retreat limit position is set to the screw retreat limit regulation position, in the present embodiment, the variation range of the screw position at the time of completion of the latter half of the resin amount measurement process is as follows: As a result, the measurement volume is reduced to a half of the conventional one, and thus the variation in the measuring volume becomes smaller than in the conventional case. Also, for example, the value of the smaller screw retreat amount within the variation range of the screw position at the time of completion of the latter half of the resin amount measurement process when good plasticization and measurement is performed is determined by the screw retreat amount. If it is set to the limit position, the screw position at the time of completion of the latter half of the resin amount measurement process will generally converge to the screw retreat limit position, and the metering volume will be stable.

FIG. 4 is a view showing an example of a screen for setting the plasticizing and measuring conditions displayed on the display device of the injection molding machine according to the present embodiment. In the figure, 31 is a condition setting column for the plasticizing / resin feeding process, 32 is a condition setting column 33 for the first half of the resin amount measuring process, and a condition setting column 34 for the second half of the resin amount measuring process. It is a condition setting column of the resin amount measurement process.

Condition setting column 3 for plasticizing / resin feeding process
1 includes a screw stroke setting section 31a for a plasticizing / resin feeding process and a screw rotation setting section 31b.
And a resin pressure setting section 31c. Also,
The condition setting field 33 for the first half of the resin amount measurement process includes a time setting unit 33a and a resin pressure setting unit 33b for the first half of the resin amount measurement process. At the completion of the first half of the journey,
A display portion 33c is provided for indicating a retreat width from the screw measurement position at the completion of the plasticizing / resin feeding process (a minus sign is displayed when the screw retreats). The condition setting field 34 for the latter half of the resin amount measurement process includes a setting section 34 for the screw retreat limit stroke width of the screw for the latter half of the resin amount measurement process.
a, and a setting unit 34b for setting the time of the latter half of the resin amount measurement process
And a resin pressure setting section 34c are provided.
A display portion 34d is provided for displaying the retreat stroke width of the screw from the screw measurement position at the time of completion of the first half of the resin amount measurement process at the time of completion of the second half of the resin amount measurement process in the latest shot. And the operator
Display unit 34 when good plasticization and weighing are being performed
By referring to the display data of d, the set value of the retreat limit stroke width in the setting section 34a can be set to an appropriate value.

FIG. 5 is an explanatory diagram showing an example of a state along the time axis of the plasticizing / measuring process of the present embodiment associated with each set value on the screen of FIG. The horizontal axis represents time, and the vertical axis in the figure represents resin pressure and screw rotation speed.

In FIG. 5, N1 is a screw rotational speed set value set in the plasticizing / resin feeding process, and is set to 350 rpm here. N2 is an actually measured value of the screw rotation speed in the plasticizing / resin feeding process.

M1 is a resin pressure set value which is set according to each of the plasticizing and measuring steps, and is 100 kgf / cm ² in the plasticizing and resin feeding step, and 150 kgf in the first half of the resin amount measuring step. / Cm ² , and 10 kgf / cm ² in the latter half of the resin amount measurement process. M2 is a measured resin pressure value in each of the plasticizing and measuring steps.

As shown in FIG. 5, in the present embodiment, the resin pressure set value in the first half of the resin amount measuring process is set to be larger than the resin pressure set value in the plasticizing and resin feeding process. The reason for this is that, as mentioned earlier, the thrust (pressure) generated by screw rotation during the plasticization and resin feeding process
Because the resin pressure is not controlled accurately, the resin density varies at the completion of the plasticization / resin feeding process. This is because it has been experimentally proved that when a resin pressure larger than the resin pressure of the above is added for a predetermined time by the pressure feedback control (by the pressure feedback control along the time axis), the variation in the resin density can be reduced favorably. .

As shown in FIG. 5, in the present embodiment, the resin pressure set value in the second half of the resin amount measuring process is set to be much smaller than the resin pressure set value in the first half of the resin amount measuring process. is there. The reason for this is that if the resin pressure raised in the first half of the resin amount measurement process is maintained as it is until immediately before the start of injection, the molten resin may drool from the nozzle at the tip of the heating cylinder (drooling phenomenon). Therefore, in order to prevent this, an effect substantially equivalent to suckback is obtained in the latter half of the resin amount measurement process.

In the case of an injection molding machine having a nozzle provided with a drooling prevention valve, it is not necessary to provide the latter half of the above-described resin amount measuring step. The above-described retreat limit stroke width is set at the start of the resin amount measurement process by executing the pressure feedback control of one stage pressure, which is set to a resin pressure set value larger than the resin pressure set value of the resin feeding process. The position may be set as a reference.

FIG. 6 is an explanatory diagram showing an example of a state along the screw stroke axis of the plasticizing / measuring process of the present embodiment, which is associated with each set numerical value on the screen of FIG. The horizontal axis of represents the screw stroke (screw position),
The vertical axis in the figure represents the resin pressure.

As shown in FIG. 6, the measured resin pressure value M2 is
It rises from the start position of the plasticizing / resin feeding process and reaches the end position of the plasticizing / resin feeding process, that is, to the start position of the first half of the resin amount measuring process (here, the starting position of the plasticizing / resin feeding process is Reference position 0
Up to the position of 28.50 mm), pressure feedback control is performed so as to follow the resin pressure set value in the plasticizing / resin feeding process. From the start position of the first half of the resin amount measurement process, pressure feedback control is performed for 0.3 seconds so as to follow the resin pressure set value of the first half of the resin amount measurement process. At the end of the first half of the resin amount measurement process (the start of the second half of the resin amount measurement process), the screw position takes a position from the reference position 0, for example, 28.35 mm in this case at the end of the first half of the resin amount measurement process. . This 28.35 mm is actually measured and recognized as the position at the start of the second half of the resin amount measurement process, and the position of 28.35 mm at the start of the second half of the resin amount measurement process is added to the resin amount measurement process. The position obtained by adding the retraction limit stroke width 1.20 mm of the screw in the latter half stroke, that is, the screw position of 29.55 mm, is set as the position where the screw cannot further retreat (the screw retraction limit restriction position). From the position at the start of the second half of the resin amount measurement process, pressure feedback control is performed for 0.2 seconds so as to follow the resin pressure set value of the second half of the resin amount measurement process, and as a result, The screw retreats by a predetermined amount, and at the end of the latter half of the resin amount measurement process, the screw stops at the position of 29.55 mm or a position immediately before it.

[0045]

As described above, according to the present invention, in the in-line screw type injection molding machine, the variation in the resin density and the variation in the screw position at the time of completion of the plasticizing and measuring process are also suppressed. Is possible,
Good and stable plasticization and measurement suitable for precision molding and the like can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a main configuration of an in-screw type injection molding machine according to an embodiment of the present invention.

FIG. 2 shows a configuration 1 of a pressure feedback control unit in FIG.
It is explanatory drawing which shows an example.

FIG. 3 shows a control output value y1 in one embodiment of the present invention.
FIG. 10 is an explanatory diagram showing a state of a latter half of a resin amount measuring process, showing a relationship between the resin amount measuring process and y2.

FIG. 4 is an explanatory diagram showing an example of a setting screen of a plasticizing / metering condition displayed on a display device according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an example of a state along a time axis of a plasticizing / metering process associated with each numerical value on the screen of FIG. 4 according to an embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an example of a state along a screw stroke axis of a plasticizing / metering process associated with each numerical value on the screen of FIG. 4 according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Screw 3 Screw rotation servo motor 6 Injection servo motor 9 Encoder 10 Load cell 11 Encoder 12 Plasticization / metering condition setting storage unit 13 Screw rotation speed setting storage unit 14 Resin pressure condition setting storage unit 15 Plasticization・ Measurement control unit 16 Screw rotation speed feedback control unit 17 Pressure feedback control unit 18 Servo amplifier 19 Servo amplifier

Claims (3)

[Claims] 1. An injection molding apparatus comprising: a screw rotating drive source for rotating a screw; and an injection drive source for driving the screw forward and backward. A method of controlling a machine, wherein the first step of a plasticizing / metering process is a plasticizing / resin feeding process, wherein the screw rotational speed is feedback-controlled while the screw rotational speed is controlled by feedback control of the screw. The second step of the plasticization / metering process, which is executed by performing control, is the second stage of the plasticization / metering process following the plasticization / resin feeding process. This is performed by performing pressure feedback control along the axis, and the retraction limit that defines the final screw retraction position in this resin amount measurement process. Set a fixed value to monitor the current position of the screw even during the resin amount measurement process, and control so that the screw does not exceed the position specified by the retraction limit value during the resin amount measurement process. A method for controlling an injection molding machine. 2. The pressure feedback control according to claim 1, wherein at least an initial predetermined time of the resin amount measuring step is set by a set pressure value higher than a set pressure value of the pressure feedback control in the plasticizing / resin feeding step. A method for controlling an injection molding machine. 3. The pressure feedback control according to claim 2, wherein during the first half of the resin amount measurement process, a pressure set value higher than a pressure set value of the pressure feedback control of the plasticization / resin feeding process is performed. A method for controlling an injection molding machine, wherein pressure feedback control is performed in a latter half of the resin amount measurement process using a set pressure value that is low enough to produce a suck-back effect.