JPH08290450A - Control method for injection molding machine - Google Patents

Abstract

PURPOSE: To attain the molding of a high quality product by stabilizing the weight of a molded product by stabilizing the measured amount of a resin and giving proper pressure holding force. CONSTITUTION: In an inline screw type injection molding machine, a primary injection stroke by velocity feedback control in which a pressure upper limit value is regulated from a measuring finish position (injection start position) is implemented to acquire a measured velocity curve in this operation. The deviation (excess or shortage) of the present measured resin amount from an initialized measured resin amount is calculated from an initialized velocity reduction curve and the velocity reduction curve in the acquired measured velocity curve, and a measuring finish position for the next shot is dislocated by the corrected amount corresponding to the deviation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for an in-line screw type injection molding machine, and more particularly to a control method for stabilizing the amount of measured resin.

[0002]

2. Description of the Related Art A servo motor is used as an injection drive source,
The injection molding machine with feedback control of the injection process (primary injection process and subsequent pressure-holding process) is capable of precise speed feedback control and pressure feedback control. There is.

In an injection molding machine that performs such feedback control, normally, the velocity feedback control is performed on the primary injection process (the process from the measurement completion position (injection start position) to the filling completion position (holding pressure switching point)). The pressure holding process is performed by pressure feedback control. That is, during the primary injection stroke period, a speed target value is set along the screw stroke (screw forward position), and speed feedback control is performed so that the measured speed value matches this value. The pressure target value is set along the time axis, and the pressure feedback control is performed so that the measured pressure value matches this.

However, as described above, since the speed feedback control is performed until the end of the primary injection stroke,
Forced to continue to maintain a speed commensurate with the target speed value, even if the resin pressure is greatly increased due to an unexpected situation at the end of the next injection stroke (for example, by completing filling before the holding pressure switching point). Because it is speed feedback controlled,
Further, there is a problem that the resin pressure is increased to cause overpack (overfilling).

In order to prevent this, a pressure upper limit value other than the velocity target value is set in the primary injection stroke region, and when the actual pressure measurement value reaches the above pressure upper limit value during the primary injection by the velocity feedback control. A method is known in which the speed feedback control is switched to the pressure priority control by the open control according to the pressure upper limit value.

[0006]

However, in this type of injection molding machine, the reaction force received by the screw from the molten resin measured by the screw is caused at every shot due to the expansion variation of the resin during the plasticizing / measuring process. Strictly speaking, the measurement completion position is not uniform in each case, and there is a variation in the front and rear with respect to the standard measurement completion position (set measurement completion position), and the actual measurement completion position has a slightly large amount of resin. Often, the completion position or the measurement completion position where the amount of resin is slightly small is set.

As described above, when the actual measurement completion position varies, for example, when the measurement completion position where the amount of resin is slightly large is taken, the actual pressure measurement value is obtained during the primary injection by the speed feedback control as described above. When the control method that switches to the pressure priority control by the open control according to the pressure upper limit value is reached when the pressure upper limit value is reached, after the actual filling is completed (after the measured screw speed reaches almost 0).
However, there is an inconvenience that the screw does not reach the set holding pressure switching position. That is, the fact that the screw does not reach the set holding pressure switching position even after the actual filling is completed means that there is an excessive amount of resin above the desired cushion amount on the tip side of the screw, Due to the excess resin and the variation in the density of the resin, it becomes difficult to apply a good holding pressure in the pressure-holding process, which causes the variation in the density of the molded product, that is, the variation in the weight of the molded product.

On the other hand, when the resin is taken in the metering completion position where the amount of resin is slightly smaller, the screw reaches the set holding pressure switching position before the actual filling is completed, and the resin filled in the mold is filled. Insufficient density and cushion amount make it impossible to provide good holding pressure in the holding process, which causes insufficient weight of the molded product.

The present invention has been made in view of the above points,
The purpose thereof is to stabilize the amount of the measured resin and to give a good holding pressure, thereby stabilizing the density of the molded product (weight of the molded product) and achieving good product molding.

[0010]

In order to achieve the above-mentioned object, the present invention is an in-line screw type injection molding machine, in which primary control is performed by speed feedback control which defines a pressure upper limit value from a measurement completion position (injection start position). The injection stroke is executed, the speed measurement curve at this time is acquired, and from the speed deceleration curve initially set and the speed deceleration curve in the speed measurement curve acquired above, the measurement of the current shot for the initially set measurement resin amount is performed. Amount of deviation of resin amount (excess and shortage)
Is calculated, and the measurement completion position of the next shot is shifted by the correction amount corresponding to the above-mentioned shift amount.

[0011]

In the microcomputer (microcomputer) that controls the entire machine, the speed target value and the pressure upper limit value for speed feedback control are specified as the operating condition setting values for the primary injection stroke during the injection stroke. Pressure regulation value, 1
The speed deceleration curve at the end of the next injection stroke and the planned filling completion position (scheduled pressure switching point) are set.

Then, at each shot cycle, at a predetermined injection start timing after the end of the plasticizing / measuring stroke, the microcomputer refers to the operating condition set value for the primary injection stroke and sets 1 The next injection stroke is first started by speed feedback control. At this time, the above-mentioned pressure regulation value of a constant value for defining the upper limit value of speed is set in the primary injection stroke region, and the microcomputer measures the above-mentioned pressure measurement value that rises as the injection / filling progresses. It is determined whether or not the pressure regulation value has been reached, and when the actual pressure measurement value and the pressure regulation value match during the primary injection stroke, the speed feedback control is terminated, and instead, the pressure regulation value is followed. Start pressure priority control by open control. As a result, the speed starts decreasing, and at the screw forward position where the resin is completely filled in the mold, the speed becomes, for example, almost 0, and the filling is completed (primary injection is completed).

The above-mentioned measured speed value in the primary injection stroke is taken in by the microcomputer and is created and stored as speed measurement curve information. The speed deceleration curve in this speed measurement curve and the initially set speed deceleration curve are stored. Using the microcomputer, the microcomputer calculates the deviation amount (excess / deficiency amount) of the measured resin amount of the current shot with respect to the initially set measured resin amount. Then, the metering completion position for the next shot is set to be shifted by the correction amount corresponding to this shift amount.

By taking such a method, in the second and subsequent shots, the actual measurement completion position of each shot becomes appropriate for the proper amount of measured resin, which reflects the content of the previous shot. As a result, the filling completion position is almost constant, the amount of resin and cushion filled in the mold is stable, and good holding pressure can be applied. Weight) is also stable.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to one illustrated embodiment. FIG. 1 is a block diagram showing a main configuration of a control system in an injection molding machine according to an embodiment of the present invention. In FIG. 1, only a control system related to an injection stroke and a metering stroke is shown.

In FIG. 1, reference numeral 1 is a microcomputer, which is actually an MPU, ROM, RAM,
It is configured with various I / O interfaces and the like, and executes various processes by various programs created in advance to control the entire machine (injection molding machine). In the present embodiment, for convenience of description, the microcomputer 1 described above has a storage unit 11 for setting data for primary injection and a storage unit 12 for storing setting data for pressure holding as functional blocks related to the above-described injection stroke and metering stroke. , A speed feedback control unit 13a, a pressure priority control unit 13b by open control, and an injection stroke control unit 1 including a pressure feedback control unit 13c.
3. Storage section 14 for setting data for weighing process including weighing completion position setting / storage section 14a, weighing process control section 15, input processing sections 16, 17, 18, clock section 19, speed calculation section 20, speed measurement curve The following description will be made assuming that the generator 21, the initial setting speed curve storage 22, the measurement completion position correction value calculator 23, and the like are provided.

In FIG. 1, 2 is a rotation speed sensor for detecting the rotation speed of a known screw (not shown), 3 is a stroke sensor for detecting the position of the screw, and 4 is resin pressure (metal mold) pressed by the screw. A pressure sensor for detecting the pressure of resin injected / filled inside, 5 is an injection servomotor which is an injection drive source for moving the screw forward and backward, 6 is a driver (driver circuit) for the motor 5, and 7 is a screw rotation. A servomotor for measurement, which is a driving source for driving (plasticization / measurement), 8 is a driver of the motor 7.

The rotation speed sensor 2 detects the rotation speed of a screw (not shown) that is rotationally driven during the measurement stroke, and this detection information is appropriately converted by the input processing unit 16 and, if necessary, the measurement stroke control unit. 15 is sent.

The stroke sensor 3 detects the position information of the screw, and after this detection information is appropriately converted by the input processing unit 17, the injection stroke control unit 13, the measurement stroke control unit 15, and the speed calculation unit. 20 and the speed measurement curve generation unit 21.

The pressure sensor 4 detects the resin pressure, and this detection information is appropriately converted by the input processing unit 18 and then sent to the injection stroke control unit 13 and, if necessary, the measurement stroke control unit 15.

The speed calculation unit 20 calculates the actual speed value of the screw in real time from the position data from the input processing unit 16 and the clock signal from the clock unit 19.
This is performed by the injection stroke control unit 13 and the velocity measurement curve generation unit 21.
And send to.

In the storage portion 11 of the setting data for the primary injection, a speed target value along the screw stroke (screw advance position) in the primary injection area for controlling the primary injection area by the speed feedback control is stored. ,
To control the final region of the primary injection region by pressure priority control by open control, set a fixed pressure regulation value in all regions of the primary injection and the planned filling completion position (scheduled pressure switching point).・ Stored.

The holding condition setting data storage unit 12 stores control conditions for the holding pressure region. In this embodiment, the time in the holding pressure region for controlling the entire holding pressure region by pressure feedback control. The target pressure value along the axis is set and stored.

The injection stroke control unit 13 is provided in each of the storage units 1
Based on the control condition data of the primary injection stroke and the pressure-holding stroke stored in 1 and 12, screw position information from the stroke sensor 3, resin pressure information from the pressure sensor 4, clock information from the clock unit 19, speed calculation While referring to the speed information from the unit 20, the speed feedback control unit 13
The servomotor 5 for injection is driven and controlled via the driver 6 by a, the pressure priority control unit 13b, and the pressure feedback control unit 13c.

That is, in the primary injection in the injection stroke, first, the speed feedback control section 13a is used to start injection / filling from the injection start position by speed feedback control, and the pressure that rises as the injection / filling progresses. When the measured value reaches the set pressure regulation value, the speed feedback control is stopped, and then the pressure priority control unit 13b is activated.
Using, the pressure priority control by the open control is started so as to comply with the pressure regulation value, and this is executed up to the holding pressure switching point. The holding pressure in the injection stroke is executed by pressure feedback control using the pressure feedback control unit 13c.

In the storage portion 14 of the setting data for the metering process, the metering completion position indicated by the backward stroke (position) of the screw from the above-mentioned planned filling completion position (scheduled pressure switching point), and the initially set charging The target screw speed along the screw stroke from the planned completion position, the back pressure along the screw stroke from the initially set planned completion position, and the like are set. Then, the measurement completion position (that is, the injection start position) is the new data (new measurement completion position) for the next shot cycle every time the injection of one shot ends It is updated and stored in the setting / storage unit 14a.

The metering stroke control unit 15 is based on the control data of the metering stroke stored in the storage unit 14, and the screw rotation speed information from the rotation speed sensor 2, the screw position information from the stroke sensor 3, and the pressure sensor 4 are stored. The metering servomotor 7 is driven and controlled via the driver 8 while referring to the resin pressure information as the back pressure control information from the above, the clock information from the clock unit 19 and the like. Further, during this measurement process, the measurement process control unit 15 drives and controls the injection servomotor 5 via the driver 6 to control the back pressure applied to the screw. In the present embodiment, the metering stroke control unit 15 controls the screw rotation and the back pressure by feedback control, but the metering stroke control unit 15 may be open control.

At least during the primary injection stroke, the velocity measurement curve generation unit 21 uses the input screw position information and velocity information to obtain velocity measurement curve data along the screw stroke in the primary injection region. It is generated for each shot, and this is updated and held.

The initially set speed curve storage unit 22 stores and holds the initially set speed curve data based on the speed target value along the initially set screw stroke.

The correction value calculation unit 23 for the measurement completion position stores the deceleration curve data in the speed measurement curve data of the current shot stored in the speed measurement curve generation unit 21, and the initial value stored in the initial setting speed curve storage unit 22. Based on the deceleration curve data in the set speed curve data, calculate the deviation amount (excess / deficiency amount) of the measurement resin amount for this shot with respect to the initially set measurement resin amount, and obtain the correction data corresponding to this deviation amount. , And outputs to the storage unit 14 of the setting data for the weighing process. As a result, the weighing completion position data for the next shot is updated and set / stored in the weighing completion position setting / storing unit 14a of the storage unit 14.

Next, the operation of this embodiment will be described with reference to FIG. FIG. 2 is an explanatory diagram showing the state of control of the injection stroke according to the present embodiment, in which the vertical axis represents speed (screw advance speed) and pressure (resin pressure), and the primary axis on the horizontal axis. The injection area represents the position (screw stroke). 2A shows the state of a certain shot (for example, the first shot), and FIG. 2B shows the state of the next shot (for example, the second shot).

In a certain shot cycle, when the predetermined injection start timing after the completion of measurement is reached, the microcomputer 1
Refers to the setting conditions of the primary injection stroke, first starts the primary injection stroke by speed feedback control, and as a result, as shown in FIG. 2A, the actual speed measurement value matches the speed setting value. The screw is advanced from the measurement completion position (injection start position) to start injection / filling while controlling so as to perform. At this time, in the primary injection stroke region, a constant pressure regulation value P for defining the upper speed limit is set.
a is set, and the microcomputer 1 monitors the pressure measurement value that rises as the injection / filling progresses, and determines whether this pressure measurement value has reached the pressure regulation value Pa. .

When the measured pressure value and the pressure regulation value Pa coincide with each other during the primary injection stroke, that is, in FIG.
At the control switching point of (a), the microcomputer 1 ends the speed feedback control, and instead, the pressure regulation value P
The pressure priority control by open control is started so as to comply with a.

When entering the open control region by the above-mentioned pressure priority control, pressure control (motor torque value control) in which the speed is ignored is executed, so the speed is rapidly decelerated and approaches zero. After entering the pressure priority control, the microcomputer 1
It is monitored whether or not the speed has reached a point where the speed approaches 0, and when the speed approaches 0, the control is switched to the pressure holding stroke. That is, the screw position where the speed approaches 0 is regarded as the actual filling completion position, and this point is set as the actual holding pressure switching point.

After that, the microcomputer 1 starts the pressure-holding operation by the pressure feedback control, and controls the pressure so that the measured pressure value follows the pressure set value in the pressure-holding region.

In the example shown in FIG. 2A, the actual filling is completed before the initially set planned filling completion position, and the actual deceleration curve is steeper than the initially set deceleration curve. It has become a thing. In this way, the fact that the screw does not reach the initial planned filling completion position even after the actual filling is complete means that there is excess resin above the desired cushion amount on the tip side of the screw. become.

The measured speed value in the primary injection stroke of the shot shown in FIG. 2 (a) is taken into the microcomputer 1 and, as described above, the measured speed value in the primary injection region is measured by the speed measurement curve generation unit 21. A pattern is generated,
This is retained.

Thereafter, the microcomputer 1 causes the correction value calculation unit 23 for the measurement completion position to measure the speed measurement curve data of the current shot (here, the shot of FIG. 2A) stored in the speed measurement curve generation unit 21. Based on the inside deceleration curve data and the deceleration curve data in the initial setting speed curve data stored in the initial setting speed curve storage unit 22,
The deviation amount (excess / deficiency amount) of the measurement resin amount of this shot with respect to the initially set measurement resin amount is calculated.

As shown in FIG. 2A, the actual deceleration curve and the initially set deceleration curve each include data on the filling completion position, and the curve characteristics of the actual deceleration curve are , The density of the resin in that shot is reflected. That is, the actual deceleration curve can be rephrased as resin amount data in which the density of the resin is taken into consideration, and in the present invention, the amount of deviation of the measured resin amount is not calculated by simply comparing the filling completion positions and calculating the amount of deviation. The deviation amount (excess / deficiency amount) of the measured resin amount in the state where the density is taken into consideration is calculated. This calculation method can be obtained by an approximate calculation formula obtained in advance by performing a case study using the characteristic data of the resin and the inclination of the deceleration curve at each position.

When the microcomputer 1 obtains the deviation amount of the measured resin amount, the microcomputer 1 calculates a correction value of how much to shift the measurement completion position of the next shot from the measurement completion position of the current shot according to the deviation amount. To do. In the case of FIG. 2A, the amount of measured resin is too large. Therefore, in order to set the measured resin amount of the next shot to an appropriate value, the correction value calculation unit 23 at the measurement completion position is set to the correction value calculation unit 23 of FIG. The correction value α as shown in is output to the storage unit 14 of the setting data for the weighing process. As a result, the measurement completion position setting / storage unit 14a of the storage unit 14 is set.
2 shows the measurement completion position for the next shot.
The measurement completion position Sx of (b) is set.

When the predetermined measurement operation start timing for the next shot is reached, the measurement process control unit 15 of the microcomputer 1
As described above, the screw is rotated while controlling the back pressure, and when the set measurement completion position Sx is reached, the screw rotation is stopped and the measurement process is ended. In successive shots during the continuous molding operation, the expansion characteristics of the resin and the like are very similar, and therefore the injection start position of the next shot is usually the set measurement completion position Sx in FIG. 2B. It almost agrees.

After that, when the injection start timing of the next shot is reached, similarly to the above, first, the primary injection stroke by the speed feedback control is started, and as shown in FIG. The screw is advanced from the position (injection start position) Sx to start injection / filling. Then, in the course of the primary injection stroke, the measured pressure value and the pressure regulation value Pa
At the time when and match (that is, at the control switching point of FIG. 2B), the speed feedback control is terminated,
Instead, the pressure priority control by the open control is started so as to comply with the pressure regulation value Pa.

When entering the open control region by the pressure priority control, the speed is rapidly decelerated, but the actual deceleration curve at this time is almost the same as the initially set deceleration curve as shown in FIG. 2 (b). As a result, the control is switched to the pressure-holding stroke when the speed approaches 0. The actual filling completion position, which is the holding pressure switching point at this time, is shown in FIG.
As shown in (1), it almost coincides with the initially set expected completion position of filling, and therefore the cushion amount takes an appropriate value.

After that, the pressure-holding operation by the pressure feedback control is performed in the same manner as above, but the density of the filling resin in the mold at the start of the pressure-holding and the amount of cushion remaining on the tip side of the screw are proper. Therefore, a good holding pressure is applied, so that the density of the molded product is stable, and a good product having an appropriate weight is molded. After that, the control operation described above is repeated.

In the example of FIG. 2 described above, an example in which this is corrected when the actual amount of measured resin is excessive has been described. On the contrary, the actual amount of measured resin is small and this is It is obvious to those skilled in the art that the same method can be used to shift the measurement completion position so as to increase it.

Further, in the above-described embodiment, the deviation amount (excess / deficiency amount) of the measurement resin amount of the current shot with respect to the initially set measurement resin amount is calculated, and when there is the deviation amount, the deviation amount is always detected. Although the measurement completion position of the next shot is shifted by the correction amount corresponding to, when each shot enters the stable area (when the deviation amount falls within the predetermined allowable range), Even if the measurement completion position is not corrected, the continuous molding of good products can be sufficiently ensured in practical use. Therefore, only when the deviation amount is not within the predetermined allowable range, the measurement completion position of the next shot may be shifted by the correction amount corresponding to the deviation amount.

[0047]

As described above, according to the present invention, it is possible to stabilize the amount of the measured resin and to give a good holding pressure, and thus the density of the molded product (weight of the molded product) is stable, Good molding can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a control system in an injection molding machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a state of control of an injection stroke according to one embodiment of the present invention.

[Explanation of symbols]

 1 Microcomputer (Microcomputer) 2 Rotation Sensor 3 Stroke Sensor 4 Pressure Sensor 5 Injection Servo Motor 6 Injection Servo Motor Driver 7 Weighing Servo Motor 8 Metering Servo Motor Driver 11 Storing Setting Data for Primary Injection Part 12 Storage of setting data for holding pressure 13 Injection stroke control part 13a Speed feedback control part 13b Pressure priority control part 13c Pressure feedback control part 14 Storage part of setting data for measurement process 14a Measurement completion position setting / storage part 15 Measurement Stroke control section 16, 17, 18 Input processing section 19 Clock section 20 Speed calculation section 21 Speed measurement curve generation section 22 Initial setting speed curve storage section 23 Corrected value calculation section of measurement completion position

Claims (2)

[Claims] 1. A screw in a heating cylinder is rotated to transfer the resin material to the tip side of the screw while kneading and plasticizing the resin material, storing the measured molten resin at the tip side of the screw, and advancing the screw to move the metal. In the injection molding machine that injects and fills the molten resin in the mold, execute the primary injection stroke by speed feedback control that defines the pressure upper limit value from the measurement completion position (injection start position), and display the speed measurement curve at this time. From the speed deceleration curve that was acquired and initialized and the speed deceleration curve in the speed measurement curve that was acquired above, calculate the deviation amount (excess / deficiency amount) of the measured resin amount for this shot with respect to the initially set measured resin amount. A method for controlling an injection molding machine, characterized in that the measurement completion position for the next shot is shifted by a correction amount corresponding to the above-described deviation amount. 2. The screw in the heating cylinder is rotated to transfer the resin material to the tip side of the screw while kneading and plasticizing the resin material, storing the measured molten resin at the tip side of the screw, and advancing the screw. In the injection molding machine that injects and fills the molten resin in the mold, execute the primary injection stroke by speed feedback control that defines the pressure upper limit value from the measurement completion position (injection start position), and display the speed measurement curve at this time. From the speed deceleration curve that was acquired and initialized and the speed deceleration curve in the speed measurement curve that was acquired above, calculate the deviation amount (excess / deficiency amount) of the measured resin amount for this shot with respect to the initially set measured resin amount. If the deviation amount is not within the predetermined allowable range, the measurement completion position for the next shot is shifted by the correction amount corresponding to the deviation amount. A method for controlling an injection molding machine, characterized in that