JPH08244078A - Method for controlling injection pressure of injection molding machine - Google Patents

Abstract

PURPOSE: To perform stabilized pressure control until dwelling process of injection is completed just after the injection is started. CONSTITUTION: During molding products with good qualities, processing for sampling is performed and the resin counterforce IPi and the mold inner pressure MPi are stored at each sampling time i=1 to n. By the time when a resin reaches the position of arrangement of the second pressure sensor 7, feedback control of the pressure is performed based on the deviation between the sampling data IPi of the resin counterforce and the present value IPR of the resin counterforce detected by means of a load cell and after the resin reaches the position of arrangement of the second pressure sensor 7, the feedback control of the pressure is performed based on the deviation between the sampling data MPi of the mold inner pressure and the present value MPR of the mold inner pressure detected by means of the second pressure sensor 7. Just after the injection is started, control of the injection pressure can be immediately started by using a load cell 8 and in addition, after the resin is filled, feedback control of the resin pressure in the mold can be directly performed by means of the second pressure sensor 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved injection pressure control method for an injection molding machine.

[0002]

2. Description of the Related Art A desired change in the pressure inside an injection mold is set as a target value in a control device in advance, and a pressure sensor is provided in the injection mold to determine the actual pressure at each point in the injection process. An injection molding machine which has been detected by a sensor and has feedback control of injection pressure is already known. However, in the structure in which the pressure sensor is provided in the injection molding die, the resin pressure cannot be detected by the pressure sensor until the resin is filled in the injection molding die after the injection is started, and the pressure feedback control is performed. I can't.

Also, inside the tip of the cylinder of the injection molding machine,
That is, there is also proposed an injection molding machine in which a pressure sensor is provided at a position where the resin is filled from the beginning before the start of injection, and feedback control of the injection pressure can be performed immediately after the start of injection. However, with such a configuration, if the resin begins to solidify in the pressure-holding stage in the latter half of the injection process, the resin pressure in the injection-molding die cannot be accurately transmitted to the cylinder, which hinders feedback control of the pressure-holding pressure. May cause Of course, when a pressure sensor such as a load cell is attached to the base of the screw for feedback control of pressure, the same problem as this occurs.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to control injection pressure by feedback control of pressure from immediately after the start of injection until the pressure holding step of injection is completed. It is an object of the present invention to provide an injection pressure control method for an injection molding machine, which can continuously and stably perform the above.

[0005]

According to the present invention, there is provided a first aspect for detecting a resin reaction force acting on a screw or a cylinder pressure.
Second pressure sensor and second pressure to detect the pressure inside the injection mold
Is provided, and the change in the resin reaction force acting on the screw or the pressure in the cylinder and the change in the pressure in the injection molding die are individually set in the control device so that the resin is the second
Until the pressure sensor reaches the pressure sensor, the feedback control of the injection pressure is performed based on the set resin reaction force or the cylinder internal pressure and the current pressure detected by the first pressure sensor, while the resin is controlled to the second pressure sensor. After reaching the pressure sensor, the feedback control of the injection pressure is performed based on the set pressure inside the injection mold and the current pressure detected by the second pressure sensor. The above-mentioned object is achieved by the structure.

Further, by using sampling data at the time of molding a good product as the resin reaction force which is a target value, the pressure in the cylinder and the pressure inside the injection molding die, the optimum injection conditions suitable for the injection molding die can be stabilized. So that it can be reproduced.

Further, the detection value of the second pressure sensor or the pressure inside the injection molding die set in advance in the control device is read for each sampling cycle in the injection process, and whether or not the value is equal to or more than a predetermined value is read. By determining whether the resin has reached the second pressure sensor by
The feedback control can be smoothly switched by each pressure sensor.

[0008]

The change in the resin reaction force acting on the screw or the pressure in the cylinder and the change in the pressure inside the injection mold are individually set as target values in the control device in advance. At this time, if the injection conditions at the time of molding the non-defective product are directly reflected, the sampling data at the time of molding the non-defective product is used as it is as the target resin reaction force, the pressure in the cylinder, and the pressure inside the injection molding die.

Until the resin reaches the second pressure sensor, the control device controls the injection pressure based on the resin reaction force or the cylinder internal pressure and the current pressure detected by the first pressure sensor until the resin reaches the second pressure sensor. Feedback control is performed, and after the resin reaches the second pressure sensor, the injection pressure of the injection pressure is determined based on the pressure inside the injection molding die and the current pressure detected by the second pressure sensor. Perform feedback control.

Whether or not the resin has reached the second pressure sensor is determined by reading the detection value of the second pressure sensor or the pressure inside the injection molding die set in advance in the control device at every sampling cycle in the injection process. It is determined whether or not the value is equal to or larger than a predetermined value.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main part of an electric injection molding machine according to an embodiment of the present invention. The structure of the cylinder 2, the screw 3, the load cell 8, the power transmission mechanism 4, and the injection servomotor 5 is exactly the same as that of the conventional electric injection molding machine, and the rotational movements of the injection servomotor 5 and the motor 5 are converted into linear movements. The screw 3 is driven in the injection axis direction by the power transmission mechanism 4 that operates. The load cell 8 is a pressure sensor provided between the output shaft of the power transmission mechanism 4 and the screw 3, and is the first sensor in this embodiment.
Of the pressure sensor. As the first pressure sensor, in addition to the load cell 8 that detects the resin reaction force acting on the screw 3, a pressure sensor that is mounted inside the tip of the cylinder 2, that is, a pressure sensor that detects the pressure in the cylinder can be substituted. is there. Strictly speaking, the load cell 8 that detects the resin reaction force acting on the screw 3 and the pressure sensor that is installed inside the tip of the cylinder 2 have different detection targets, but in both cases, the resin pressure can be detected immediately after the start of injection. They are the same in some respects, and both can be used as the first pressure sensor in the present invention.

A second pressure sensor 7 for detecting the resin pressure inside the mold is located at an appropriate position in the injection mold 1.
Is provided. As the position where the second pressure sensor 7 is provided, a cold slag well (generally, a position where the Z pin is located) near the sprue, a runner portion, a product portion, and other pools of the hot water are considered. The design and manufacture of the injection mold is a problem for the user side. Depending on what kind of pressure control should be performed when performing the injection molding work using the injection mold, the second pressure sensor 7 may be selected. The position to be provided should be decided by each user.

In addition, it is necessary to prevent burning of the resin in the mold due to generation of high heat due to compression of gas.
The injection mold 1 is usually provided with a gas vent, etc.
In addition, it is necessary to allow the gas to be discharged from the parting line or the seam of the core without providing a special gas vent. As a result, even if the injection is started, the injection molding die 1 is completely filled with the resin, or at least until the resin reaches the position where the second pressure sensor 7 is disposed. No pressure is detected by the second pressure sensor 7.

When the second pressure sensor 7 is provided in the cold slug well, runner portion, etc. near the sprue, that is, when the second pressure sensor 7 is provided on the path of the resin filling process, the resin is injected. The feedback control of the pressure by the second pressure sensor 7 is started before the molding die 1 is completely filled. At this time, the second pressure sensor 7 detects the surge pressure of the flowing resin or the position of the second pressure sensor 7 rather than the internal pressure of the injection mold 1 at least at the beginning. It is the sum of the viscous resistance of the resin. Therefore, when the second pressure sensor 7 is provided in the cold slug well, runner portion, etc. near the sprue, the second pressure sensor 7 detects the surge pressure of the flowing resin and the sum of the viscous resistance of the resin. The second pressure sensor 7 has a function similar to that of the load cell 8 (first pressure sensor) as far as it is limited, but the second pressure sensor 7 is provided inside the injection molding die 1, that is, the injection molding die 1. It is provided at a position where the resin does not exist at the time of starting, and moreover, after the filling of the resin is completed, the internal pressure of the injection molding die 1 is accurately detected without being deteriorated in the pressure detection due to the solidification of the resin. However, after the completion of the resin filling, the injection mold 1 is affected by the length of the pressure propagation path and the pressure drop due to the complexity of the path. Internal pressure Load cell 8 it is difficult to precisely detect the (first pressure sensor) and, indeed, its nature is different.

Further, when the second pressure sensor 7 is provided in the product part or the like, that is, when the second pressure sensor 7 is generally provided at the position where the resin is filled last, it is almost complete. After the injection molding die 1 is filled with the resin, in short, the pressure feedback control by the second pressure sensor 7 is started after the substantial pressure holding step is performed. At this time, what is detected by the second pressure sensor 7 is the internal pressure of the resin that acts substantially equally on each part of the injection mold 1 from the beginning.

At the stage of designing and manufacturing the injection molding die 1, it is necessary to consider these points and clarify the purpose of the pressure control to determine the position where the second pressure sensor 7 is arranged.

A control device 10 for driving and controlling the injection molding machine.
Is a C for CNC which is a microprocessor for numerical control
A PU 25, a PMC CPU 18 which is a programmable machine controller microprocessor, a servo CPU 20 which is a servo control microprocessor, and A
It has a CPU 17 for pressure monitoring for detecting the injection pressure and the mold internal pressure from the load cell 8 and the second pressure sensor 7 via the / D converter 16 and performing sampling processing, and they are mutually connected via the bus 22. Information can be transmitted between the microprocessors by selecting input / output.

The PMC CPU 18 is connected to the ROM 13 which stores a sequence program for controlling the sequence operation of the injection molding machine and the RAM 14 which is used for temporary storage of operation data. The CNC CPU 25 is connected to the entire injection molding machine. A ROM 27 that stores a control program that controls the image and a RAM 28 that is used for temporary storage of calculation data are connected.

Further, each of the servo CPU 20 and the pressure monitor CPU 17 relates to a ROM 21 storing a control program dedicated to servo control, a RAM 19 used for temporary storage of data, a sampling process of injection pressure and mold internal pressure, and the like. ROM storing the control program
11 and a RAM 12 used for temporary storage of data are connected. Further, the servo CPU 20 has the CPU 2
Based on the command from 0, the servo amplifier that drives the servo motor of each axis for mold clamping, injection, screw rotation, ejector, etc. is connected, and the output from the pulse coder attached to the servo motor of each axis is output. It is adapted to be fed back to the servo CPU 20. Then, the current position of each axis, its moving speed, etc. are calculated by the servo CPU 20 based on the feedback pulse from the pulse coder.
Although only the servo amplifier 15 for the injection axis, the injection servomotor 5 and the pulse coder 6 of the motor 5 are shown in FIG. 1, the configuration of each axis for mold clamping, ejector, etc. is the same as this. . However, for the screw rotation type, it is not necessary to detect the current position, and only the speed may be detected.

The interface 23 is an input / output interface for receiving signals from limit switches and operation panels provided in various parts of the injection molding machine body and for transmitting various commands to peripheral equipment of the injection molding machine. .

The manual data input device 29 with a display is connected to the bus 22 via the CRT display circuit 26, and is capable of displaying a graph screen, selecting a function menu and inputting various data. A numeric keypad for inputting and various function keys are provided.

The non-volatile memory 24 is a memory for storing molding data for storing molding conditions and various set values, parameters, macro variables and the like relating to injection molding work. In addition, in the present embodiment, in addition to these data, the set values of the change in the resin reaction force acting on the screw 3 and the change in the pressure inside the injection molding die 1 have a predetermined data format (see FIG. 6). ) Is set and stored.

With the above configuration, the PMC CPU 18 controls the sequence operation of the entire injection molding machine, and the CNC C
The PU 25 outputs a movement command or a speed command to the servo motor of each axis based on the control program of the ROM 27, the molding conditions of the non-volatile memory 24, etc., and the servo CPU
Numeral 20 is a servo for position loop control, speed loop control, or current loop control based on a movement command or speed command for each axis and position and speed feedback signals detected by a detector such as a pulse coder. Control is performed and so-called digital servo processing is executed.

Needless to say, in the injection process, the injection speed / pressure switching control mode is carried out by setting the injection / holding pressure switching position with reference to the screw position to prioritize the injection speed and then switch to the injection pressure control. It is also possible to carry out, and at the stage of injection molding work such as condition setting,
A plurality of injection stages and pressure-holding stages are set by the injection speed / pressure switching control mode, and the injection speed and the injection pressure (holding pressure) are variously changed for each stage, and the target is used in the same manner as in the past. The optimum molding conditions suitable for the injection mold 1 are obtained. In addition, the output of the load cell 8 is detected while performing the priority control of the injection speed, and when the value reaches a predetermined value, the priority control of the injection speed is terminated and the injection pressure (holding pressure) is maintained at a predetermined pressure. The present applicants have also proposed an injection control method in which the control of (1) is started, but it is also possible to perform injection molding work such as condition setting by utilizing such a method.

FIG. 3 shows a "target value" for setting and storing in the control device 10 a change in the resin reaction force acting on the screw 3 and a change in the pressure inside the injection mold 1 in the injection speed / pressure switching control mode. 5 is a flowchart showing an outline of "setting processing". During the operation of the injection molding machine, this processing is repeatedly executed by the pressure monitoring CPU 17 at predetermined intervals in synchronization with the speed loop processing in the servo CPU 20.

The pressure monitor CPU 17 which has started the "target value setting process" first determines whether or not the function menu of the "reference registration mode" is selected (step a).
1), only when this function menu is selected
The processing after step a2 is continuously performed. Therefore, the substantial "target value setting process" is executed only when the function menu of "reference registration mode" is selected. The “target value setting process” is for sampling a change in resin reaction force and a change in mold internal pressure during the injection process during molding of a good product, and setting this in the nonvolatile memory 24 as a target value for pressure control. Therefore, the operator needs to select the function menu of the "reference registration mode" after completing the injection molding work for condition setting. The operator selects the “standard registration mode” during the continuous molding operation by using the manual data input device 2 with a display.
9 is operated by operating the function key 9. Further, while the pressure monitoring CPU 17 is performing the sampling process, a diagram showing the sampling data is displayed on the display screen of the manual data input device 29 with a display as in the case of the normal monitor display. ing. In the example of FIG. 7, the display state of the manual data input device 29 with a display at the end of the sampling process is shown, and each diagram of V, IP and MP shows the injection speed, the resin reaction force, and the internal pressure of the injection molding die 1, respectively. It is a diagram corresponding to the sampling data of. In the conventional monitor display, the diagram of the internal pressure MP of the injection molding die 1 is not displayed (the second pressure sensor 7 is not provided in the first place), and in this respect, the monitor display of the present embodiment is different from the conventional monitor display. However, since there is no technical difficulty in displaying the internal pressure MP itself (similar to the display of the resin reaction force IP), detailed description of this new matter will not be given.

When the function menu of "reference registration mode" is selected, that is, when the determination result of step a1 is true, the pressure monitoring CPU 17 then determines whether the sampling execution flag F'is set. It is determined whether or not (step a2). At the stage immediately after selecting the function menu of "reference registration mode", the sampling execution flag F'is not set, so the pressure monitoring CP
U17 further determines whether or not the injection start detection flag F ″ is set (step a3). The injection start detection flag F ″ is not set at the stage immediately after selecting the function menu of “reference registration mode”. In this state, the CPU 17 for pressure monitoring is further connected to the RAM 1 of the CPU 18 for PMC.
4 and determines whether or not the injection execution flag F is set (step a4). Injection execution flag F
Is a flag that is set when the injection command to start the injection process is output from the PMC CPU 18 that controls the entire sequence control. Therefore, even at this point, the injection execution flag F is not set. There are cases. That is, if the injection process of a certain molding cycle has already started at the time when the operator selects the function menu of "reference registration mode", the injection execution flag F is set, and the operator selects "reference registration mode". If the process of the injection process is not performed at the time when the function menu is selected, the injection execution flag F is not set. Note that the injection step here is to switch between injection speed priority control and injection pressure priority control by setting the injection / holding pressure switching position with reference to the screw position in the injection speed / pressure switching control mode. In the same injection process as in the conventional method, or while detecting the output of the load cell 8 while performing priority control of the injection speed, when the value reaches a predetermined value, the priority control of the injection speed is cut off and predetermined. The same injection process as the conventional one that starts the priority control of the injection pressure (holding pressure) with the set pressure (in short, it is just the injection control performed to extract the sampling data at the time of molding the good product after the condition is set. Absent)
However, the feedback control of pressure performed according to the gist of the present invention is not included.

When the injection execution flag F is already set, if the sampling data extraction is started at this time, the data from immediately after the start of injection until this time is not extracted. ,
At this point, the sampling data extraction is not started, the sampling process in this molding cycle is postponed, the processing of the processing cycle is ended, and the start of the injection process in the next molding cycle is awaited. . Further, if the injection execution flag F is not set, it means that the process of the injection process is not being performed at the time when the operator selects the function menu of the “reference registration mode”. CPU 17 for pressure monitoring cannot be processed.
Sets the injection start detection flag F ″ (step a
5) It waits for the start of the injection process in the next molding cycle. That is, if the setting of the injection execution flag F ″ is detected in the subsequent processing cycle after the setting of the injection start detection flag F ″ is completed in this way, the point at which the injection execution flag F changes from OFF to ON The rise of the injection process can be detected.

As a result, if the injection process has already been started when the operator selects the "reference registration mode" function menu, the determination process of steps a1 to a4 is completed until the injection process is completed. Only is repeatedly executed, and when this injection process is completed, step a
After the injection start detection flag F ″ is set in the process of No. 5, only the determination process of steps a1 to a3 and step a6 is repeatedly executed until the process of the next injection process is started. Further, if the process of the injection process has not been performed at the time when the operator selects the function menu of the “reference registration mode”, as described above, the process of step a5 causes the injection start detection flag at that time. F ″ is set, and thereafter, only the determination process of steps a1 to a3 and step a6 is repeatedly executed in the same manner as described above. The content of the process of step a6 is substantially the same as the process of step a4. It is the same.

When the next injection step is started while the pressure monitoring CPU 17 repeatedly executes the determination processing of steps a1 to a3 and step a6, P
The injection execution flag F is set by the MC CPU 18, and the pressure monitoring CPU 17 detects this in the determination processing of step a6. That is, it is the detection of the rise of the injection process described above. Therefore, the CPU 17 for pressure monitoring resets the injection start detection flag F ″, sets the sampling execution flag F ′, and initializes the address index i that determines the sampling data storage area to zero (step a).
7) Sampling processing of the injection speed present value VR, the resin reaction force present value IPR, and the present value MPR of the internal pressure of the injection molding die 1 is started. It should be noted that an example of the table provided in the RAM 12 for storing each sampling data is shown in FIG. 6 for reference.

The CPU 17 for pressure monitoring which has started the sampling process first increments the value of the address index i by 1 (step a8), and calculates the pressure data from the load cell 8 and the second pressure sensor 7 by the servo CPU 20. The injection speed data at that time is read, and each of them is associated with the value of the address index i, and the RAM
The data is stored in the storage areas Vi, IPi, MPi of the table in 12 (step a9). Next, CPU for pressure monitor
17 determines whether or not the injection execution flag F is reset, that is, whether or not one injection process of a certain molding cycle is completed (step a10), but if not completed, this processing cycle The "target value setting process" in is ended as it is. The reset operation of the injection execution flag F is similar to the operation at the time of setting, and the PMC CPU 1
CPU for pressure monitoring,
It has no direct relation to the action of 17.

In the subsequent processing cycle, the above-mentioned step a
Since the sampling execution flag F'is already set by the process of 7, the steps a1 and a2
Of the injection speed current value VR, the resin reaction force current value IPR, and the mold for each sampling cycle based on the value of the address index i that is sequentially incremented Each value of the internal pressure present value MPR is stored in the storage areas Vi, IPi, MPi of the table in the RAM 12 one after another.

When the injection execution flag F is reset by the PMC CPU 18 and the completion of the injection and pressure holding control in the one injection step is detected by the determination processing in step a10, the pressure monitoring CPU 17 returns to the "reference. After canceling the selection of the function menu of "registration mode" and resetting the sampling execution flag F ', after shifting the final value of the address index i, that is, the total number of sampling data to the register n, the value of the address index i is initialized. Then, the value of the total number n of sampling data and all the stored contents of the table are transferred to and stored in the nonvolatile memory 24, and the data in the RAM 12 is erased (step a1).
1). Incidentally, the time required for this one injection step (including the holding pressure) is equal to the time obtained by multiplying the processing cycle of the "reference registration mode" (the processing cycle of the speed loop) by n. Even if the selection of the function menu of "standard registration mode" is canceled, the display of the line diagram on the display screen of the manual data input device with display 29 is not erased, but this display is displayed when another function menu is selected again. It is automatically deleted.

As one example, as described above, the resin reaction force obtained in the injection process at the time of molding a good product and the respective sampling data IP1 to IPn and MP1 to MPn of the mold internal pressure are used to change and inject the resin reaction force. Although the one in which the change in the internal pressure of the molding die 1 is set and stored in the control device 10 as it is has been described, the data after the correction or the edit is added to the data by correcting or editing the data. May be stored in the non-volatile memory 24 of the control device 10 again. As a working method such as correction and editing, a method of rewriting the data of the table transferred to the non-volatile memory 24 by a direct numeric input operation with a ten-key or the like, or a diagram as shown in FIG. There is a method such as displaying on the manual data input device 29 with a display and changing the shape of the diagram by an operation using a graphic cursor, digitizing this again, and automatically writing it as data in the corresponding position of the table. In any of these cases, the data editing method itself belongs to the related art, and a detailed description thereof will be omitted.

In this embodiment, sampling data IP1 to I of resin reaction force obtained in the injection process at the time of molding a good product.
Pn and mold internal pressure sampling data MP1
Injection speed sampling data V1 to Vn together with MPn
Are stored in the non-volatile memory 24, and V1 to Vn are command data necessary for superimposing speed feedback control together with pressure feedback control in this embodiment. Therefore, in the case where only the pressure feedback control is executed without performing the speed feedback control, it is not necessary to store the injection speed sampling data V1 to Vn.

FIG. 2 is a functional block diagram showing an outline of the injection speed feedback control executed in the injection pressure feedback control mode in this embodiment and the injection control in which the pressure feedback control is superimposed. Vi is C
The speed command for each predetermined period given from the NC CPU 25 to the servo CPU 20, that is, the sampling data Vi (where i = 1 to 1) of the injection speed extracted as described above.
The value of n). Further, ΔVi is a pressure deviation correction command given from the CNC CPU 25 to the servo CPU 20 for each predetermined cycle, and is derived from the value of the resin reaction force sampling data IPi (where i = 1 to n) extracted as described above. Mold A at that time from the value A obtained by multiplying the deviation obtained by subtracting the current value IPR of the resin reaction force at that time by a predetermined gain, or the sampling data MPi (where i = 1 to n) of the mold internal pressure It is either a value B obtained by multiplying a deviation obtained by subtracting the current value MPR of the internal pressure by a predetermined gain.
As a result, until the resin reaches the arrangement position of the second pressure sensor 7, the sampling data IPi of the resin reaction force is obtained.
And the current value IPR of the resin reaction force detected by the load cell 8 (first pressure sensor) and the feedback control of the pressure is performed with ΔVi = A, and the resin is distributed by the second pressure sensor 7. After reaching the installation position, pressure feedback control is performed with ΔVi = B based on the deviation between the sampling data MPi of the mold internal pressure and the current value MPR of the mold internal pressure detected by the second pressure sensor 7. Will be done. The predetermined cycle here is the same as the above-described sampling cycle, that is, the processing cycle of the speed loop in the digital servo control.

The CNC CPU 25 uses the speed command Vi described above.
And the pressure deviation correction command ΔVi described above are added to the servo CP.
Output as a speed command to U20. The servo CPU 20 performs a speed loop process based on the speed command Vi + ΔVi and the speed feedback signal from the pulse coder 6 of the injection servo motor 5 to obtain a torque command (current command), and further performs a current loop process as in the conventional case. The injection servomotor 5 is driven via the servo amplifier 15, and the current value IPR of the resin reaction force detected by the load cell 8 and the mold internal pressure detected by the second pressure sensor 7 are controlled along with the speed feedback control. Pressure feedback control is superposed so that the current value MPR coincides with the sampling data IPi of the resin reaction force during molding of a good product and the sampling data MPi of the internal pressure of the mold during molding of a good product. According to this method, since the reference speed command Vi is always present, the resin reaches the position where the second pressure sensor 7 is arranged and ΔVi =
Even when the pressure deviation correction command is switched from A to ΔVi = B, there is an advantage that inadvertent fluctuation is unlikely to occur. Further, as described above, it is also possible to carry out only the pressure feedback control. In that case, the basic speed command Vi is not used, and the pressure deviation correction command ΔVi is directly applied to the current loop as the torque command value. Be sure to enter.

FIG. 4 shows a process for obtaining the speed command (Vi + ΔVi) to the speed loop process executed by the servo CPU 20 in order to realize the function shown in FIG. This process corresponds to CN in the injection pressure feedback control mode.
This is processing that is repeatedly executed by the C CPU 25 for each processing cycle of the speed loop relating to the injection servomotor 5.

The CNC CPU 25 first determines whether or not the injection execution flag F is set (step b1). If the flag F is not set, it means that the process of the injection process is not performed at this point, and therefore the processes after step b2 are not executed, and the process of the cycle ends.

For the injection process, the CNC CPU
25 is incremented by 1 for the value of the address index i for retrieving the sampling data (same configuration as in FIG. 6) stored in the non-volatile memory 24 (step b2).
Then, it prepares to read the sampling data corresponding to the processing cycle. Since the initial value of the address index i is set to zero by the initial setting, in the process executed immediately after the injection execution flag F is set, that is, immediately after the start of the injection process, the value of i in the process of step b2. Will be set to 1.

Next, the CPU 25 for CNC determines whether or not the pressure control switching flag MF is set (step b3). This flag MF is a flag set by the CPU 25 when the second pressure sensor 7 detects the arrival of the resin. Therefore, if this flag is not set, sampling data IP of resin reaction force
It is necessary to perform feedback control of the pressure based on i and the current value IPR of the resin reaction force. Further, if the pressure control switching flag MF is set, the sampling data MPi of the mold internal pressure and the mold internal pressure This means that it is necessary to perform pressure feedback control based on the current value MPR.

Therefore, if the pressure control switching flag MF is not set, the CPU 25 for CNC reads the current value MPR of the mold internal pressure and the current value IPR of the resin reaction force via the pressure monitoring CPU 17 (step b4),
It is determined whether or not the current value MPR of the mold internal pressure is zero (less than or equal to the set value), that is, whether or not the resin has reached the disposition position of the second pressure sensor 7 (step b5).

If the current value MPR of the mold internal pressure is zero and the resin has not reached the position where the second pressure sensor 7 is disposed, the CNC CPU 25 determines the nonvolatile memory based on the value of the address index i. Sampling data I of the resin reaction force which is the target value at this time from the 24 sampling data
Pi is read to obtain the deviation between the current value IPR of the resin reaction force and the sampling data IPi of the resin reaction force, and this deviation is multiplied by a predetermined gain to obtain the pressure deviation correction command ΔVi (step b6). This is the block 100 shown in FIG.
Is a process corresponding to. And the CPU 25 for CNC
Further, the sampling data Vi of the injection speed corresponding to the address index i is read from the sampling data of the nonvolatile memory 24, and the value obtained by adding ΔVi to the reference speed command Vi is used as the speed command (servo loop of the servo CPU 20). To (step b7). This is the process corresponding to the block 103 shown in FIG.

Then, the CNC CPU 25 determines whether or not the value of the address index i has reached the total number n of sampling data, that is, whether or not the processing of the injection step including the pressure holding may be terminated ( Step b8), if not reached, the processing of this cycle is ended.

Hereinafter, as long as zero is continuously detected as the current value MPR of the internal pressure of the mold, the CPU 25 for CNC repeatedly executes the processing of steps b1 to b8 in a predetermined cycle in the same manner as described above, at that time. Sampling data IPi of resin reaction force that is the target value and current value I of resin reaction force
The target speed command Vi at that time is added to the pressure deviation correction command ΔVi based on the deviation of PR, and the servo C
The speed command (Vi + ΔVi) is output to the PU 20.
The servo CPU 20 performs speed loop processing in the same manner as in the conventional method to obtain a torque command based on the speed command (Vi + ΔVi) and the current speed detected by the pulse coder 6, and further,
A current loop process is performed in the same manner as in the conventional case to drive and control the injection servomotor 5, and the injection operation by the screw 3 is performed. Thereby, the feedback control of the injection speed and the feedback control of the injection pressure are superposed.

On the other hand, when the resin reaches the position where the second pressure sensor 7 is provided and the second pressure sensor 7 detects the pressure, the determination result of step b5 becomes false, and the CPU for CNC is used.
In step 25, the pressure control switching flag MF is set (step b9), and the feedback control of the pressure is started based on the sampling data MPi of the mold internal pressure and the current value MPR of the mold internal pressure. This is the switching process corresponding to the block 102 shown in FIG.

Sampling data MPi of mold internal pressure
In the feedback control of the pressure based on the current value MPR of the mold internal pressure and the current value MPR of the mold, C based on the value of the address index i.
The CPU 25 for NC reads the sampling data MPi of the mold internal pressure from the non-volatile memory 24 and obtains the deviation between the current value MPR of the mold internal pressure and the sampling data MPi of the mold internal pressure which is the target value at that time. Then, the deviation is multiplied by a predetermined gain to obtain the pressure deviation correction command ΔVi (step b11). This is the process corresponding to the block 101 shown in FIG. Injection speed sampling data V corresponding to the value of the address index i
The point that ΔVi is added to i and output as a speed command is the same as above (step b7).

As a result of the pressure control switching flag MF being set, steps b1 to b in the following processing cycle.
3. Step b10 (reading process of MPR in place of step b4) to step b11 and step b7 to step b8 are repeatedly executed every predetermined period, and the current value MPR of the mold internal pressure and the target value at that time are set. The injection servo motor 5 is driven and controlled while the pressure feedback control and the velocity feedback control based on the sampling data MPi of a certain mold internal pressure are superimposed.

Finally, when it is confirmed that the value of the address index i has reached the total number n of sampling data in the discrimination processing of step b10, the CNC CPU 25
Resets the pressure control switching flag MF and initializes the address index i to zero (step b12).
An injection completion command is output to the PU 18 (step b1
3) Then, the processing of the cycle is finished.

The PMC CPU 18 receiving this resets the injection execution flag F, and as a result, the injection process of a new molding cycle is started and the injection feedback flag F is set again until the injection execution flag F is set again. Enters a substantial dormant state. Then, when the injection step of the next molding cycle is started again, the same process as described above is repeated with the initialized value of the address index i as the initial value (the initial value of the address for reading the data is 1). Will be executed.

As described above, from the time immediately after the start of injection until the resin reaches the position where the second pressure sensor 7 is disposed, the resin reaction force at the time of molding a good product is set as the target value and the load cell 8 is used.
The feedback control of the resin reaction force is performed using the pressure sensor as the pressure sensor, and further, from the time the resin reaches the disposition position of the second pressure sensor 7 until the holding pressure in the injection process is completed, a good product is molded. The pressure in the mold is controlled by using the second pressure detection sensor 7 provided in the mold as the pressure sensor, and the pressure control in the mold is performed. It is possible to reliably control the pressure during the entire injection process.

Needless to say, even in the conventional injection molding machine in which the pressure sensor is provided only inside the tip of the cylinder, it is possible to control the pressure throughout the entire injection process, but when the resin filling is completed, the pressure control is substantially completed. If the pressure is kept constant, the resin will begin to solidify inside the die and the tip of the cylinder, and the resin pressure inside the die will not be accurately transmitted to the pressure sensor inside the tip of the cylinder. It is impossible to accurately detect and perform pressure feedback control. Also, the solidified state of the resin changes considerably depending on the temperature of the cylinder and the mold, so in the configuration in which the pressure sensor is provided only inside the tip of the cylinder, the gain adjustment of the feedback control should be performed in anticipation of the pressure drop. It is impossible to do it. On the other hand, in the present embodiment, the load cell 8 for detecting the resin reaction force (of course, a conventional pressure sensor inside the cylinder tip may be used in place of the load cell 8) and the resin pressure inside the mold. The second pressure sensor 7 for detecting is provided independently, and the target value is set for each of them to perform the feedback control of the pressure according to the filling state of the resin. It is possible to perform precise pressure control which is hardly affected by the resin pressure drop at the tip of the cylinder and the fluctuations caused by the temperature change.

Further, the actual injection speed detected at the time of molding the non-defective product is used as the speed command, and the pressure deviation correction command is further superposed on the actual injection speed so that the speed feedback control and the pressure feedback control are superposed. Therefore, even when the pressure control based on the resin reaction force is switched to the pressure control based on the pressure inside the mold, this can be stably performed without causing an inadvertent change.

As described above, by actually detecting the current value MPR of the internal pressure of the injection molding die 1, it is determined whether the resin has reached the position where the second pressure sensor 7 is disposed, and the pressure control is performed. Although the embodiment in which the switching is performed has been described, this can be determined by referring to the sampling data stored in the non-volatile memory 24.

FIG. 5 shows the processing of the embodiment in which the arrival of the resin at the pressure sensor 7 is determined by referring to the sampling data. Note that step c1 to step c3, step c6 to step c8, step c10 shown in FIG.
Since each process of step c13 is exactly the same as each process of step b1 to step b3, step b6 to step b8, and step b10 to step b13 described in FIG. 4, description thereof will be omitted.

The embodiment shown in FIG. 5 differs from the embodiment described with reference to FIG. 4 in that, first, in the embodiment of FIG. 4, the current value MPR of the internal pressure of the injection molding die 1 is actually read and the value is read. While it is determined whether or not the resin has reached the second pressure sensor 7 by determining whether or not is zero (FIG. 4: step b4 to step b5), execution of FIG. In the example, the sampling data MPi + 1 of the internal pressure of the injection molding die 1 one cycle ahead is read from the sampling data of the internal pressure of the injection molding die 1 stored in the non-volatile memory 24, and is the value zero? Depending on whether or not the resin reaches the second pressure sensor 7 in the processing cycle of the next speed loop, it is predicted (FIG. 5: step c5).

Here, if the sampling data MPi + 1 is zero, naturally, the value of the sampling data MPi of the internal pressure of the injection mold 1 in the processing cycle, which is one cycle before that, is also zero. Therefore, it means that the resin has not reached the second pressure sensor 7 at this time, and the sampling data IP of the resin reaction force in the processing cycle.
A process for performing pressure feedback control based on i and the current value IPR of the resin reaction force is applied (FIG. 5: step c6).

Even if the sampling data MPi + 1 is not zero, as long as the pressure control switching flag MF is not set, the sampling data of the internal pressure of the injection molding die 1 in the processing cycle one cycle before the sampling data MPi + 1. Since the value of MPi is zero (for the reason described later), the processing for performing the feedback control of the pressure is applied in the processing cycle based on the sampling data IPi of the resin reaction force and the current value IPR of the resin reaction force. There is a need to. However, in this case, since it is clear that the resin reaches the second pressure sensor 7 in the next processing cycle, the pressure control switching flag M
F is set at this point (FIG. 5: Step c
9) In the same manner as described above, pressure feedback control is performed based on the resin reaction force sampling data IPi and the resin reaction force current value IPR (FIG. 5: step c6). That is, even at the time of sampling during molding of a good product, the second pressure sensor 7 always detects zero until the resin reaches the first time, and always detects a value of zero or more after the resin once reaches. Therefore, as shown in step c5 of FIG. 5, the sampling data MPi + 1 of the internal pressure one cycle ahead is always prefetched at the time of feedback control of the pressure after the completion of sampling, and the sampling data MPi + 1 of one cycle or more is prefetched. Sampling data MPi + 1 having a value
Is detected in the first processing cycle, that is, the i-th processing cycle, the flag MF is set, and the last pressure feedback based on the resin reaction force sampling data IPi and the current value IPR of the resin reaction force in the processing cycle is set. Control the i +
The current value M of the mold internal pressure from the first processing cycle to the next
It suffices to start the pressure feedback control based on PR and the sampling data MPi + 1 of the mold internal pressure which is the target value at that time. Step b in FIG.
This is the reason why the branch destination after execution of 9 and the branch destination after execution of step c9 in FIG. 5 are different.

The other points are exactly the same as those of the embodiment shown in FIG. 4, and the operational effects are almost the same.

[0060]

According to the injection pressure control method of the present invention, the first pressure sensor for detecting the resin reaction force acting on the screw or the pressure in the cylinder and the second pressure sensor for detecting the pressure inside the injection molding die are provided. Is provided, and the change in the resin reaction force acting on the screw or the pressure in the cylinder and the change in the pressure inside the injection molding die are individually set in the control device, until the resin reaches the second pressure sensor. The feedback control of the injection pressure is performed based on the set resin reaction force or the cylinder internal pressure and the current pressure detected by the first pressure sensor, while it is set after the resin reaches the second pressure sensor. Since the feedback control of the injection pressure is performed based on the internal pressure of the injection molding die and the current pressure detected by the second pressure sensor, the injection is maintained immediately after the start of injection. Until process is completed, it is possible to perform stably continue the injection pressure control by the feedback control of the pressure.

Further, sampling data at the time of molding a good product is used as the resin reaction force which is the target value, the pressure in the cylinder and the pressure inside the injection molding die, and whether the resin reaches the second pressure sensor or not is determined. The detection value of the second pressure sensor or the pressure inside the injection molding die set in advance in the control device is read for each sampling cycle in the injection process, and it is determined by whether or not the value is equal to or more than a predetermined value. Therefore, it is possible to accurately reproduce the pressure change in the same state as when molding the good product.

Further, a first pressure sensor for detecting the resin reaction force and a second pressure sensor for detecting the resin pressure inside the injection molding die are separately provided, and a target value is set for each of them. Since the pressure feedback control is performed according to the resin filling state, there is a difference due to the narrowing of the resin path inside the mold and the tip of the cylinder, and the change in the solidification state of the resin. Without being affected by the difference between the resin pressure detected inside the mold and the resin pressure detected inside the cylinder,
Precise pressure control can be performed on the resin inside the injection molding die.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of an electric injection molding machine of an embodiment to which an injection pressure control method of the present invention is applied.

FIG. 2 is a functional block diagram showing an outline of pressure feedback control in the embodiment.

FIG. 3 is a flowchart showing an outline of target value setting processing by a control device of the injection molding machine of the embodiment.

FIG. 4 is a flowchart showing an example of a speed loop process for performing pressure control by the control device of the injection molding machine of the same embodiment.

FIG. 5 is a flowchart showing another example of a speed loop process for carrying out pressure control.

FIG. 6 is a diagram conceptually showing an example of a table storing sampling data.

FIG. 7 is a diagram showing an example of a monitor display screen in a target value setting process.

[Explanation of symbols]

F Injection execution flag F'Sampling execution flag F "Injection start detection flag MF Pressure control switching flag i Address index VR Current value of injection speed IPR Current value of resin reaction force MPR Current value of internal pressure of injection mold Vi Injection speed Sampling data (standard speed command) IPi Sampling data of resin reaction force (target value of resin reaction force) MPi Sampling data of internal pressure of injection molding die (target value of internal pressure) n Total number of sampling data ΔVi pressure Deviation correction command A Pressure deviation correction command based on resin reaction force B Pressure deviation correction command based on mold internal pressure 1 Injection molding mold 2 Cylinder 3 Screw 4 Power transmission mechanism 5 Injection servo motor 6 Pulse coder 7 Second pressure sensor 8 load cell (first pressure sensor) 9 function key 10 controller 16 A / D converter 17 CPU for pressure monitor 24 Non-volatile memory 25 CPU for CNC 29 Manual data input device with display

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kaoru Hiraga 3580 Kobaba, Oshinomura, Minamitsuru-gun, Minamitsuru-gun, Yamanashi FANUC Co., Ltd. (72) Motohiro Hase 3580, Kobaba, Oshinomura, Minamitsuru-gun, Yamanashi Local FANUC Co., Ltd.

Claims (4)

[Claims] 1. A resin reaction force acting on a screw, comprising a first pressure sensor for detecting a resin reaction force acting on a screw or a pressure in a cylinder and a second pressure sensor for detecting a pressure inside an injection molding die. The change in the force or the pressure in the cylinder and the change in the pressure in the injection molding die are individually set in the control device, and the set resin reaction force or the set resin reaction force is set until the resin reaches the second pressure sensor. Feedback control of the injection pressure is performed based on the cylinder internal pressure and the current pressure detected by the first pressure sensor, and after the resin reaches the second pressure sensor, the inside of the set injection molding die is set. And a current pressure detected by the second pressure sensor, feedback control of the injection pressure is performed, and the injection pressure control method for an injection molding machine is characterized. 2. The injection pressure control method for an injection molding machine according to claim 1, wherein the set resin reaction force or cylinder internal pressure and the set internal pressure of the injection molding die are sampling data during molding of a good product. . 3. The detection value of the second pressure sensor is read in every sampling cycle in the injection step, and when the value exceeds a predetermined value, it is considered that the resin has reached the second pressure sensor. An injection pressure control method for an injection molding machine according to claim 1 or 2. 4. The pressure inside the set injection molding die is read at each sampling cycle in the injection step, and when the value exceeds a predetermined value, it is considered that the resin has reached the second pressure sensor. The injection pressure control method for an injection molding machine according to claim 1 or 2.