JPH10146874A - Controlling method of injection pressure of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct stable molding free from a leakage of resin and the like for a long period by a method wherein a change in the pressure in a power transmission system is set as a reference pressure waveform for mass production and an injection pressure waveform is controlled to be in accord with the reference pressure waveform for mass production by a pressure detector from which a nozzle internal pressure detector is removed. SOLUTION: According to a first injection molding machine, control equipment 10 stores a change in the internal pressure of a nozzle or that of a mold in a nonvolatile memory 24 in an updating manner through the intermediary of an A/D converter 16b and makes it data on a reference pressure waveform. The data are down-loaded on a storage medium connected to an interface 23. The storage medium is connected to the interface 23 of a second injection molding machine equipped with a nozzle internal pressure detector and with a pressure detector in a power transmission system and the nonvolatile memory 24 is made to store the data as a target value of an injection pressure. A servo motor for injection is controlled so that it may be in accord with the reference pressure waveform and a change in the injection pressure is stored in the nonvolatile memory 24 in the updating manner through the intermediary of an A/D converter 16a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in an injection pressure control method for an injection molding machine.

[0002]

2. Description of the Related Art An injection pressure waveform at the time of molding a non-defective product after completion of condition setting is detected as a reference pressure waveform, and this reference pressure waveform is transplanted to another injection molding machine as a target value for pressure control. An injection pressure control method for smoothly performing a molding operation by another injection molding machine is disclosed in Japanese Patent Application No. Hei.
Many have already been proposed as 138906 and the like.

However, many conventional injection pressure control methods use an injection pressure waveform detected by a pressure detector on a power transmission system, for example, a load cell provided at the rear end of an injection screw as a reference pressure waveform, Since this reference pressure waveform was directly transferred to another injection molding machine and feedback control of the injection pressure was performed, differences in structure and individual differences in the injection molding machine, for example, differences in sliding and friction resistance in the power transmission system, etc. In such a case, there is a problem that the change in the internal pressure in the mold cavity directly related to the failure of the molded product is different from the change in the internal pressure at the completion of the condition setting.

In order to solve such a problem, a pressure change in a nozzle or a mold cavity at the time of completion of condition determination is detected by a pressure sensor in a nozzle or a pressure sensor in a mold to obtain a reference pressure waveform. It is memorized, and when performing injection molding work with another injection molding machine, feedback control of injection pressure may be performed using the same nozzle pressure detector and mold pressure detector as this, Nozzles equipped with a pressure sensor inside the nozzle and molds equipped with a pressure sensor inside the mold have structural problems such as resin leakage, and stable injection molding work can be performed over a long period of time. Difficult and not suitable for mass production.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages of the prior art, to make the change in the internal pressure in the mold cavity coincide with the change in the internal pressure at the time of completion of the condition setting, and for a long time. An object of the present invention is to provide an injection pressure control method for an injection molding machine capable of performing a stable injection molding operation without resin leakage or the like over the entirety.

[0006]

According to the present invention, conditions are determined by using a first injection molding machine equipped with a nozzle pressure detector, and a change in the nozzle pressure in the injection process at the time of molding a non-defective product is determined. The injection pressure is detected by a detector and stored as a reference pressure waveform so that the reference pressure waveform is reproduced by a second injection molding machine equipped with a pressure detector in the nozzle and a pressure detector on the power transmission system. A pressure change detected by a pressure detector on the power transmission system when the control is performed is set as a mass production reference pressure waveform in the second injection molding machine, and the second pressure detector in which a nozzle pressure detector is removed is provided. The above object is achieved by a configuration in which the injection pressure feedback control is performed by the pressure detector of the injection molding machine so that the injection pressure waveform matches the reference pressure waveform for mass production.

According to this configuration, the first type used for setting the conditions is
Irrespective of the structure of the injection molding machine or the difference in solids, it is possible to accurately detect a change in the pressure in the nozzle directly related to the performance of the molded product and obtain a reference pressure waveform. Further, in the second injection molding machine used for mass production, the injection pressure is controlled so that the pressure change in the nozzle becomes a reference pressure waveform, and the pressure acting on the pressure detector on the power transmission system at that time is controlled. Since the change is set as a reference pressure waveform for mass production, after setting the reference pressure waveform for mass production, feedback control is performed using the pressure detector on the power transmission system to set the reference pressure waveform for mass production as a target value. As a result, the change in the pressure in the nozzle can be exactly matched with that at the time of non-defective molding, that is, the reference pressure waveform. As a result, in the mass production molding operation using the second injection molding machine, the in-nozzle pressure detector becomes unnecessary, and the injection molding operation using a normal nozzle becomes possible. Remove the pressure detector inside the nozzle,
Since the injection molding operation is performed using a normal nozzle, a stable injection molding operation without resin leakage or the like can be performed for a long period of time.

In addition, instead of the reference pressure waveform detected by the pressure detector inside the nozzle, the flow analysis program is generated by performing a flow analysis of the die based on the design data of the die to obtain an optimum injection pressure waveform. The same object can be achieved by using the injection pressure waveform as the reference pressure waveform.

The injection pressure waveform generated by the flow analysis program indicates the ideal reference pressure waveform at the sprue inlet, that is, the inside of the nozzle. Feedback control by a pressure detector has been required. In the present invention, the injection pressure waveform (reference pressure waveform) generated by the flow analysis program and the reference pressure waveform for mass production are replaced in the same manner as described above, so that the use of the pressure detector in the nozzle during mass production is achieved. Is unnecessary, and resin leakage is prevented, and at the same time, the injection pressure waveform (reference pressure waveform) generated by the flow analysis program can be reproduced.

Further, the same object can be achieved by using a pressure detector in the mold instead of the pressure detector in the nozzle.

The injection pressure waveform detected by the in-mold pressure detector is exactly the reference pressure waveform itself indicating a change in the internal pressure in the mold cavity, and is optimal as a target value in feedback control. Conventionally, in order to reproduce this reference pressure waveform, feedback control by an in-mold pressure detector has been required, and there has been a problem such as resin leakage. By replacing the injection pressure waveform (reference pressure waveform) with the reference pressure waveform for mass production, the use of a pressure detector in the mold during mass production is unnecessary, preventing resin leakage, and at the same time,
The injection pressure waveform (reference pressure waveform) detected by the in-mold pressure detector can be reproduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main part of a control device 10 of an injection molding machine according to an embodiment for implementing an injection pressure control method of the present invention.

The control device 10 includes a CNC CPU 25 which is a microprocessor for numerical control, and a PMC which is a microprocessor for a programmable machine controller.
CPU 18, a servo CPU 20, which is a microprocessor for servo control, and A / D converters 16a, 1
6b to detect the injection pressure from a pressure detector (a load cell at the screw base, etc.), a pressure detector in the nozzle, or a pressure detector in the mold provided on the power transmission system of the injection mechanism via 6b to perform sampling processing. Pressure monitor CPU1
7, and information can be transmitted between the microprocessors by selecting mutual input / output via the bus 22.

The A / D converter 16a is an A / D converter for connecting a pressure detector on the power transmission system, and the A / D converter 16b is a nozzle pressure detector or a mold pressure detector. A / D for selectively connecting one of the devices
It is a converter. In the second injection molding machine used for mass production, both A / D converters 16a and 16b are required, but for the first injection molding machine used for condition setting, the A / D converter is used.
Only the D converter 16b may be used.

A ROM 13 which stores a sequence program for controlling a sequence operation of the injection molding machine and a RAM 14 which is used for temporary storage of operation data and the like are connected to the CPU 18 for the PMC. RO that stores the program to be controlled
M27 and RA used for temporary storage of operation data, etc.
M28 is connected.

Each of the servo CPU 20 and the pressure monitoring CPU 17 stores a ROM 21 storing a control program dedicated to servo control, a RAM 19 used for temporarily storing data, and a control program relating to injection pressure sampling processing and the like. ROM 11 and a RAM 12 used for temporary storage of data are connected.

Further, the servo CPU 20 includes the CPU 2
Servo amplifiers that drive servo motors for each axis for clamping, injection, screw rotation, ejector, etc. are connected based on the command from 0, and a position / speed detector attached to the servo motor for each axis is used. Output is servo CPU 20
It is to be returned to. The current position of each axis is calculated by the servo CPU 20 based on the feedback pulse from the position / speed detector, and is updated and stored in the current position storage register of each axis. FIG. 1 shows only the servo amplifier 15 for one axis, the servo motor M, and the position / velocity detector P, but the configuration of each axis for clamping, injection, ejector, etc. is all the same. However, it is not necessary to detect the current position for the screw rotation type, but only the speed.

The interface 23 is an input / output interface for connecting to a host computer or the like.

A manual data input device 29 with a display is connected to the bus 22 via a CRT display circuit 26 so that a graph display screen, a function menu can be selected and various data input operations can be performed. Numeric keys and various function keys are provided.

The non-volatile memory 24 is a memory for storing molding data for storing operation programs and molding conditions relating to the injection molding operation, various set values, parameters, macro variables, and the like.

The control device 10 is disclosed in Japanese Patent Application Laid-Open No. H6-1709.
No. 07 has a data sampling function known in the art. With this data sampling function, the temperature of the injection cylinder, injection pressure, injection speed, injection / holding pressure switching position, screw position, cushion amount, etc. collected for each molding cycle. In addition to the molding data of the non-volatile memory 24, the molding data such as the molding cycle time, the required measuring time, and the required injection time are detected.
Is to be remembered.

With the above configuration, the CPU 18 for the PMC controls the sequence operation of the entire injection molding machine, and
The PU 25 distributes movement commands to the servo motors of each axis based on the system program in the ROM 27, the operation program in the nonvolatile memory 24, the molding conditions, and the like. Based on the position and speed feedback signals detected by the position and speed detector, servo control such as position loop control, speed loop control, and current loop control is performed in the same manner as in the past.
A so-called digital servo process is executed to drive and control the servo motor of each axis.

A description will now be given of a processing operation when the pressure control method of the present invention is performed by applying the above-described configuration.

FIG. 2 is a flowchart showing an outline of a process for obtaining a reference pressure waveform using the first injection molding machine.

The operator firstly mounts a mold and is equipped with a first injection molding machine equipped with a pressure sensor in the nozzle, or a first injection molding machine equipped with a mold equipped with a pressure detector in the mold. The machine determines the conditions for obtaining good molded products while changing molding conditions in various ways.

The control device 10 performs an injection molding operation based on the set molding conditions, and in each injection step (including the holding pressure), the inside of the nozzle detected by the in-nozzle pressure sensor or the in-mold pressure sensor is detected. The change of the pressure or the pressure in the mold is updated and stored in the non-volatile memory 24 as a time-series function for each molding cycle by the above-mentioned sampling function via the A / D converter 16b (step a1).

The operator confirms the condition of the molded product in each molding cycle, waits until a stable continuous molding operation is achieved, and ends the continuous molding operation for determining the conditions (step a2).

At this time, that is, in one molding cycle during a stable continuous molding operation, the change in the pressure in the nozzle or the change in the pressure in the die stored in the nonvolatile memory 24 becomes a reference pressure waveform at the time of molding a good product. Data.

This reference pressure waveform is data to be implanted in the second injection molding machine as a target value for injection pressure control. Therefore, a storage medium such as a floppy disk and its drive unit are connected to the interface 23, and the data of the reference pressure waveform is downloaded to this storage medium (step a3). Of course, even if the interface 23 of the first injection molding machine and the interface 23 of the second injection molding machine used for mass production are connected by a data transmission path, the data of the reference pressure waveform is directly transferred. I do not care.

When an injection pressure waveform which is a reference pressure waveform is generated by using a flow analysis program for performing an analysis of the flow of the mold based on the design data of the mold to obtain an optimal injection pressure waveform, the flow rate of the injection The data of the reference pressure waveform generated by the analysis program may be directly stored in a storage medium such as a floppy disk, and there is no need to perform the condition setting work to obtain the reference pressure waveform as described above. This kind of flow analysis program is a publicly known program already commercially available as an application program for three-dimensional CAD or the like.

The reference pressure waveform obtained by the condition setting operation is (time, pressure) = (sampling timing,
It consists of a collection of point sequence data indicated by (injection pressure), but it is possible to generate a substantially continuous function by generating a Bezier curve or performing smoothing from this point sequence data. Also, since it is possible to replace the reference pressure waveform data generated by the flow analysis program with the point sequence data,
Both are substantially equal. The type of reference pressure waveform that is ultimately required is determined by the secondary
For example, when the data sampling cycle in the first injection molding machine is different from the data sampling cycle in the second injection molding machine, the point of the reference pressure waveform obtained by the condition setting operation depends on the characteristics of the injection molding machine. Although the column data cannot be used as it is in the second injection molding machine, the second pressure
Can be dealt with by a procedure such as re-extraction of pressure data in accordance with the data sampling cycle of the injection molding machine.

When these processes need to be performed, the timing for performing the processes may be anytime. For example, the processing may be performed by the control device 10 of the first injection molding machine before the reference pressure waveform obtained by the condition setting operation is stored in a storage medium such as a floppy disk. May be stored in a storage medium as it is, and the processing may be performed by the control device 10 at the stage when the reference pressure waveform is mounted on the control device 10 of the second injection molding machine. Of course, this may be performed by another arithmetic device during the transfer from the first injection molding machine to the second injection molding machine.

FIG. 3 is a flowchart showing an outline of a process for obtaining a mass production reference pressure waveform to be used in place of the obtained reference pressure waveform.

First, the operator installed a mold and provided a second injection molding machine equipped with a pressure detector in the nozzle and a pressure detector on the power transmission system, or a pressure detector in the mold. The second equipped with a mold and equipped with a pressure detector on the power transmission system
The storage medium such as the above-mentioned floppy disk and its drive unit are connected to the interface 23 of the injection molding machine described above, the data of the reference pressure waveform stored in this storage medium is read, and the feedback of the injection pressure is stored in the nonvolatile memory 24. It is stored as a target value for control (step b1).

As described above, the interface 23 of the second injection molding machine may be connected to the interface 23 of the first injection molding machine via a data transmission line to directly transfer the data of the reference pressure waveform.

The mold attached to the second injection molding machine is the mold itself mounted on the first injection molding machine to determine the conditions, or a mold of the same standard. As described above, since the compatibility of the reference pressure waveform data between the first injection molding machine and the second injection molding machine can be ensured, the specifications of the injection molding machine need not always be the same.

The control device 10 of the second injection molding machine has an A /
The injection servo is controlled so that the injection pressure detected by the in-nozzle pressure detector or the in-mold pressure detector via the D converter 16b matches the target value stored in the nonvolatile memory 24, that is, the reference pressure waveform. Injection molding work is performed by controlling the drive of the motor, and each injection process (including holding pressure)
In the above, the change of the injection pressure detected by the pressure detector on the power transmission system is converted into the sampling data of the non-volatile memory 24 as a time series function for each molding cycle by the sampling function via the A / D converter 16a. Update storage is performed in the storage area (step b2).

The operator confirms the condition of the molded product in each molding cycle, confirms that a stable continuous molding operation has been achieved, and terminates the continuous molding operation for obtaining the reference pressure waveform for mass production. (Step b3).

At this time, the pressure change data for one molding cycle stored in the sampling data storage area of the nonvolatile memory 24 is the reference pressure waveform for mass production (step b4).

That is, when the pressure change in the nozzle or the pressure change in the mold, for which the molding of a non-defective product is confirmed by the condition setting operation by the first injection molding machine, is achieved by the second injection molding machine, The change in the force acting on the pressure detector on the power transmission system in the injection molding machine No. 2 is a reference pressure waveform for mass production.

Therefore, regardless of the difference in structure or difference between the first injection molding machine and the second injection molding machine, for example, the difference in sliding or frictional resistance on the power transmission system, Unless the mounting position of the pressure detector on the power transmission system in the second injection molding machine is changed, or if the performance of the second injection molding machine itself is not significantly deteriorated, the power of the second injection molding machine is not changed. By reproducing the injection molding operation in which the pressure change detected by the pressure detector on the transmission system coincides with the reference pressure waveform for mass production, the pressure change in the nozzle or the mold in the injection process is reduced to the first pressure. That is, it can be reproduced in exactly the same manner as the reference pressure waveform at the time when the condition setting operation by the injection molding machine is completed. As described above, it has been confirmed at the stage of setting the conditions that the molded product formed by the reference pressure waveform becomes a non-defective product.

Therefore, in the subsequent continuous molding operation, it is not necessary to perform feedback control using the pressure sensor in the nozzle or the pressure sensor in the mold. Naturally, the pressure sensor in the nozzle or the pressure sensor in the mold itself is not necessary. There is no need.

Therefore, the operator replaces the nozzle provided with the in-nozzle pressure detector with a normal nozzle, and when using a mold provided with the in-mold pressure detector, the in-mold pressure detector is used. The mold components such as core block and cavity block with the interior are replaced with normal mold components such as normal core block and cavity block, and the members that may leak resin etc. are removed from the injection cylinder or mold. Exclude and start continuous molding work for mass production.

FIG. 4 is a flowchart showing an outline of a process relating to a continuous molding operation for mass production.

First, the operator updates and stores the mass production reference pressure waveform stored in the sampling data storage area in the nonvolatile memory 24 as a target value of the injection pressure control, and at the same time, activates the pressure detector on the power transmission system. A / D connection
Switch from converter 16a to 16b (step c)
1).

As a procedure of the festival, the reference pressure waveform for mass production stored in the sampling data storage area is updated and stored in the non-volatile memory 24 as a target value of the injection pressure control, and the pressure detector in the nozzle has been used up to that time. Alternatively, the pressure detector on the power transmission system is reconnected to the A / D converter 16b to which the in-mold pressure detector was connected, and the A / D converter 1
The feedback control from injection pressure control is performed by comparing the feedback pressure from 6b with the reference pressure waveform for mass production transferred to the storage area for the target value of injection pressure control (setting example of step c1), and sampling data storage The reference pressure waveform for mass production stored in the area is left as it is in the sampling data storage area, and the A / A pressure sensor to which the in-nozzle pressure detector or the in-mold pressure detector has been connected up to that point.
Reconnecting the pressure detector on the power transmission system to the D converter 16b, comparing the feedback pressure from the A / D converter 16b with the mass production reference pressure waveform in the sampling data storage area, and performing feedback control of the injection pressure. And when
The mass-production reference pressure waveform stored in the sampling data storage area is updated and stored in the nonvolatile memory 24 as a target value of the injection pressure control, and the feedback pressure is read from the A / D converter 16b to the A / D converter 16b. D converter 1
In the case of switching to the side of 6a and performing feedback control of the injection pressure while comparing the feedback pressure from the A / D converter 16a with the reference pressure waveform for mass production transferred to the storage area of the target value of the injection pressure control And leave the mass-production reference pressure waveform stored in the sampling data storage area in the sampling data storage area as it is, and read the feedback pressure from the A / D converter 16b to the A / D converter 16a. And the feedback control of the injection pressure is performed while comparing the feedback pressure from the A / D converter 16a with the reference pressure waveform for mass production in the sampling data storage area. Feedback pressure from the pressure detector on the powertrain for the system program Read as detection data, at the same time, mass reference pressure waveform is only that rather it suffices read as comparison target data, all these procedures are substantially identical.

Hereinafter, the control device 10 of the second injection molding machine will be described.
Until the shot number of the injection molding operation reaches the set value (step c3), the injection pressure detected from the pressure detector on the power transmission system is the target value stored in the non-volatile memory 24, that is, The drive of the injection servomotor is controlled so as to coincide with the reference pressure waveform, and the injection molding operation for mass production is repeatedly executed (step c2).

Since neither the nozzle nor the mold is provided with a pressure detector that adversely affects the hermetically sealed state, there is no fear that resin leakage will occur from the nozzle or the mold even after a long-term molding operation. In addition, the pressure change in the nozzle and the pressure change in the mold during the injection process by the feedback control of the pressure by the reference pressure waveform for mass production and the pressure detector on the power transmission system, and in short, the filling characteristics of the molten resin are determined. Since it is reproduced in the same manner as that at the time of completion, a good molded product can be molded stably.

It is to be noted that the first machine as a dedicated condition setting machine is usually used.
Of the present invention and the second injection molding machine (single or plural) as a mass production machine, but the method of the present invention can be applied even when there is only one injection molding machine. . In this case, the one injection molding machine is connected to the A / D converter 1
6a and 16b, and FIGS. 2 and 3
Is performed by the control device 10 of the injection molding machine,
Alternatively, after the reference pressure waveform is obtained by the flow analysis program and the process of FIG. 3 is performed, the nozzle of the injection molding machine or the core block or the cavity block of the mold is replaced in the same manner as described above, and FIG. A continuous molding operation for mass production is performed by the processing shown.

When there are a plurality of second injection molding machines, it is necessary to perform the processing shown in FIGS. 3 and 4 and the replacement work of the nozzle or mold core block or cavity block for each of the plurality of second injection molding machines. is there.

[0051]

According to the injection pressure control method of the present invention, the change in the internal pressure in the mold cavity when the condition of the change in the internal pressure is completed, or the ideal change in the internal pressure obtained by the flow analysis program is obtained. Therefore, a stable injection molding operation can be performed for a long time without leakage of the resin from the nozzle or the mold.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a control device of an injection molding machine according to an embodiment for implementing an injection pressure control method of the present invention.

FIG. 2 is a flowchart showing an outline of a process for obtaining a reference pressure waveform using a first injection molding machine.

FIG. 3 is a flowchart illustrating an outline of a process for acquiring a mass production reference pressure waveform to be used in place of a determined reference pressure waveform.

FIG. 4 is a flowchart showing an outline of a process related to a continuous molding operation for mass production.

[Explanation of symbols]

 Reference Signs List 10 control device of injection molding machine 11 ROM 12 RAM 13 ROM 14 RAM 15 servo amplifier 16a A / D converter 16b A / D converter 17 CPU for pressure monitoring 18 CPU for PMC 19 RAM 20 Servo CPU 21 ROM 22 Bus 23 Interface 24 Non-volatile memory 25 CNC CPU 26 CRT display circuit 27 ROM 28 RAM 29 Manual data input device with display

Claims (3)

[Claims] A condition is determined using a first injection molding machine provided with a pressure detector in a nozzle, and a change in nozzle pressure in an injection step during molding of a non-defective product is detected by a pressure detector in the nozzle to determine a reference pressure. When the injection pressure control is performed by a second injection molding machine equipped with a pressure detector in the nozzle and a pressure detector on the power transmission system so as to reproduce the reference pressure waveform, the power is stored as a waveform. A pressure change detected by a pressure detector on a transmission system is set as a reference pressure waveform for mass production in the second injection molding machine, and a pressure detector of the second injection molding machine from which a pressure detector in a nozzle is removed. Wherein the feedback control of the injection pressure is performed so that the injection pressure waveform coincides with the reference pressure waveform for mass production. 2. A flow analysis program for obtaining an optimum injection pressure waveform by performing a flow analysis of a mold based on design data of a mold instead of a reference pressure waveform detected by a pressure detector in a nozzle. 2. The injection pressure control method for an injection molding machine according to claim 1, wherein the injection pressure waveform is used as a reference pressure waveform. 3. A condition is determined using a first injection molding machine having a pressure sensor in the mold, and a change in the pressure in the mold in the injection process at the time of molding a good product is detected by the pressure sensor in the mold. The injection pressure control is performed so that the reference pressure waveform is reproduced by a second injection molding machine equipped with a pressure detector in the mold and a pressure detector on the power transmission system. The pressure change detected by the pressure detector on the power transmission system is set as a reference pressure waveform for mass production in the second injection molding machine, and the second injection with the in-mold pressure detector removed An injection pressure control method for an injection molding machine, wherein feedback control of the injection pressure is performed so that an injection pressure waveform matches a reference pressure waveform for mass production by a pressure detector of the molding machine.