JP3550206B2 - Injection control method for injection molding machine - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an injection control method for an injection molding machine. In particular, the injection speedfeedbackControl the injection pressurefeedbackcontrolRowAn object of the present invention is to provide an injection control method capable of easily obtaining an injection speed command pattern and an injection pressure command pattern in injection control.
[0002]
[Prior art]
Conventionally, the injection control of the injection molding machine is generally performed by controlling the injection speed (forward speed) of the screw with respect to the screw position. However, the quality of a molded product is more affected by the injection pressure, that is, the flow pressure of the resin, than by the injection speed. Therefore, the injection pressure is detected, and the pressure is adjusted so that the injection pressure matches the set value.feedbackAn injection control method for performing control has been developed (see JP-A-3-58821). Further, the injection pressure during injection is detected, the injection pressure pattern (waveform) is edited, and the edited pressure pattern is set as a target value to obtain the pressure.feedbackA method of performing injection control by performing control is also known in, for example, International Publication WO92 / 11994.
[0003]
Also, control the injection speedfeedbackControl and pressurefeedbackcontrolRowThis control is also proposed by the present applicant in Japanese Patent Application No. 6-124742. The method of simultaneously performing the injection speed control and the pressure control is to repeat the injection speed and the injection pressure control while correcting the speed command so as to match the set pressure pattern until the set injection pressure pattern matches the actual injection pressure waveform.RowIf a good molded product is not obtained at the stage when the set injection pressure pattern and the actual injection pressure waveform match, the set injection pressure pattern is corrected again, and based on the corrected set injection pressure pattern, the same injection injection as described above is performed. Injection speed and injection pressure control while correcting the speed commandRowIn addition, a set injection pressure pattern and a speed command for obtaining a good molded product are obtained.
[0004]
[Problems to be solved by the invention]
The above injection pressurefeedbackIn the control, a pressure deviation is obtained from the set injection pressure and the injection pressure detected by the sensor, and PID (proportional, integral, differential) control is performed based on the deviation. It is difficult to obtain and set the pattern), and it is necessary to set this difficult optimal pressure pattern every time the mold changes. Furthermore, thisFeedback controlThe PID parameter (gain) is not changed once it is set, and is not changed even when the control target (die) changes. Therefore, there is a problem that the control itself does not change, and optimal control is difficult.
[0005]
In addition, the injection speed and injection pressurePerform feedback controlAlso in the method, there is a problem that it takes time to obtain injection conditions such as an injection pressure pattern and a speed command that are optimal target values.
[0006]
Therefore, the present invention provides an injection speed and an injection pressure.Perform feedback controlAnother object of the present invention is to provide an injection control method that can easily obtain optimum injection conditions.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 of the present applicationInjection control method of injection molding machine that performs feedback control of injection speed and feedback control of injection pressureAnd
a) Perform molding by injection control of only injection speed feedback control according to the set injection speed command pattern, store the injection pressure pattern of all injection sections as a reference injection pressure pattern,
b) Thereafter, molding is performed by injection control of only the injection speed feedback control according to the set injection speed command pattern, and the absolute value of the injection pressure deviation from the reference injection pressure pattern is obtained in time series for all injection sections.
c) The above b) is performed a predetermined number of times, and the absolute values of the injection pressure deviation obtained in time series at each molding are integrated,
d) The injection speed command pattern is corrected based on the integrated value of the pressure deviation, the corrected injection speed command pattern is used as the injection speed command pattern in the injection speed feedback control, and the reference injection pressure pattern is used as the injection pressure command pattern. The injection pressure command pattern of the feedback control is characterized.
[0008]
The invention according to claim 2 is an injection control method for an injection molding machine that performs feedback control of an injection speed and feedback control of an injection pressure.
a) Perform molding by injection control of only injection speed feedback control according to the set injection speed command pattern, store the injection pressure pattern of all injection sections as a reference injection pressure pattern,
b) Thereafter, molding is performed by injection control of only the injection speed feedback control according to the set injection speed command pattern, an injection pressure deviation from the reference injection pressure pattern is obtained in time series for all injection sections, and a screw command is issued. The time when the position deviation between the position and the actual position becomes equal to or greater than the set value is stored as a position deviation increase point,
c) and b) are performed a predetermined number of times, the injection pressure deviations obtained in time series at each molding are integrated, and the minimum screw advance position at the position deviation increase point is obtained.
d)Based on the ratio between the integrated value of the injection pressure deviation obtained in time series and the maximum value of the absolute value thereof, and after the minimum screw advance position obtained in the above c), the above ratio and the preset setting are used. To a value that is chronologically increased by the ratioA correction value of the injection speed command pattern is obtained based on the
e) The injection speed command pattern is corrected based on the obtained correction value, the corrected injection speed command pattern is used as an injection speed command pattern in the feedback control of the injection speed, and the reference injection pressure pattern is used as the injection pressure command pattern. Injection pressure command pattern of feedback control andIs what you do.
[0009]
According to a third aspect of the present invention, in the invention according to the second aspect, the correction of the injection speed command pattern based on the injection pressure deviation is performed by determining the maximum of the obtained injection pressure deviation and the absolute value of the integrated value of the injection pressure deviation. It is based on the value.
[0011]
[Action]
Injection speedfeedbackThe injection control is performed only by the control, and the injection pressure pattern of the entire injection section is acquired at that time. next, FireOut speedfeedbackMolding is performed by injection control only, and an injection pressure deviation from the injection pressure pattern (the integrated value of the injection pressure deviation when performing molding a plurality of times) is obtained for all injection sections. Further, the position deviation increasing point between the command position of the screw and the actual position (the minimum screw advance position of the position deviation increasing point obtained by performing the molding a plurality of times when performing the molding a plurality of times) is determined. The occurrence of the injection pressure deviation means that the flow path of the resin becomes narrow at that position, the flow state of the resin changes, and the control system becomes unstable. In such a position, it is necessary to lower the gain of the control system to stabilize the control system. In the present invention, instead of lowering the gain, the injection speed command is lowered to cope with this. For that purpose, the injection speed command pattern is corrected (decreased command injection speed) according to the injection pressure deviation (or the integrated value of the injection pressure deviation). Further, an increase in the positional deviation means that the resin is filled in the mold, the screw stops moving, and the ability to follow the speed command is deteriorated. At this stage, the response of the speed is hardly necessary, and the gain of the control system may be reduced. However, the present invention responds by lowering the injection speed command in this case instead of lowering the gain. . As a result, the injection speed command decreases due to the injection pressure deviation.OrDecrease in injection speed command after position deviation increase pointRowBy lettingFurthermore, this By causing the injection speed command to decrease due to the output pressure deviation and the injection speed command decreasing after the position deviation increase point,At the position where the control system becomes unstable, the reduction of the injection speed command which is equal to the reduction of the gain of the control system is corrected. Then, the corrected injection speed command pattern isfeedbackThe injection pressure command pattern obtained by the first molding is used as the injection speed command pattern for control.feedbackBy setting the injection pressure command pattern for control, the injection speedfeedbackcontrolAnd fireOut pressurefeedbackIf control is performed, stable injection control can be performed.
[0012]
【Example】
Conventionally, the injection speed of a screw is set based on the screw position, and the injection control is performed by controlling the injection speed of the screw. The quality of the molded product is determined by the injection pressure (resin pressure, resin flow Pressure) The injection speed is adjusted based on the waveform, the injection speed is adjusted based on the determination result, and molding conditions are determined so as to obtain a good molded product. This is because the injection speed and injection pressure of the screw are somehow different. It is assumed that they have correlation.
[0013]
However, the injection speed of the screw is at best only a one-dimensional flow of the molten resin and not a three-dimensional flow in the mold. It is not completely proportional to the flow pressure (injection pressure).
As shown in FIG. 6, a load cell pressure sensor Se1 for detecting a resin pressure (injection pressure) acting in the axial direction of the screw 35 is attached to the base of the screw 35, and the resin of the nozzle is attached to the nozzle of the cylinder 34. A nozzle pressure sensor Se2 for detecting the pressure, a gate pressure sensor Se3 for detecting the resin pressure of the gate portion at the gate portion of the mold 39, and a cavity internal pressure sensor Se4 at the end portion of the product are used for screw injection. SpeedfeedbackControlled injection was performed for 100 shots, and an experiment was performed in which the injection speed at that time and the pressure were detected by each sensor. FIG. 7 is a diagram in which each detection value for 100 shots obtained at this time is drawn in a superimposed manner. As is clear from FIG.feedbackThe controlled injection speed does not fluctuate in each shot and is controlled accurately. However, it can be seen that the detected pressure waveforms from the respective sensors Se1 to Se4 for detecting the resin pressure are band-like at any observation point and vary.
[0014]
This meansfeedbackThe injection speed of the screw is controlled so as to accurately reproduce the set speed by the control, but the resin pressure generated in each sensor unit according to the flow speed of the molten resin generated by the movement of the screw is directly controlled. It is determined that the detected pressure waveform varies due to the absence. In addition, it can be assumed that a backflow prevention ring is provided at the tip of the screw, and the operation of the ring cannot be directly controlled during injection. Further, since the flow resistance of the actually flowing resin changes due to temperature unevenness and viscosity unevenness due to instability of plasticization, it can be assumed that even if the screw speed is constant, the resin pressure detected by each sensor fluctuates. .
[0015]
On the other hand, the pressure waveform when a good molded product is obtainedfeedbackThe screw injection speed detected during control (control so that the resin pressure detected by the load cell pressure sensor Se1 coincides with the injection pressure command pattern), and the resin pressure detected by each of the sensors Se1 to Se4 is equivalent to 100 shots. FIG. 8 shows the overwritten one. It can be seen that the resin pressure detected by each of the pressure sensors Se1 to Se4 is stable without variation, but the injection speed varies.
[0016]
As described above,feedbackIf it is controlled, the resin pressure will fluctuate.feedbackIt can be seen that, if controlled, the injection speed varies.
Further, when the time when the resin pressure is sensed by each of the sensors Se1 to Se4 is measured from the start of the injection and the variation is obtained, the result shown in the graph of FIG. 9 is obtained. In FIG. 9, A represents the injection speed.feedbackWhen control is performed, B is the pressureFeedback controlThis shows the variation when performing. As can be seen from FIG. 9, in the injection speed control, the variation in the time until the resin arrives at the position of each sensor has been affected to the last, whereas in the pressure control, the resin flows into the mold. It can be seen that the variation in the arrival time is reduced as the time goes on. This indicates that pressure control is superior to speed control.
[0017]
FIG. 10 is a view showing an experimental result obtained by measuring the variation in the weight of the molded article with respect to the mixing ratio of the recycled resin. Injection speedfeedbackControl when injection control is performedfeedbackIt is an experimental result at the time of performing injection control by control. It can be seen that the resin pressure control has less variation in the weight of the molded product than the speed control, and the pressure control is superior to the injection control.
[0018]
However, since it is easy to assume the relationship between the screw position and the resin filling position in the mold cavity, setting the injection speed by the screw position is relatively easy, but assume the flow resistance of the resin that determines the resin pressure. It is difficult to set the resin pressure based on the screw position.
On the other hand, as described above, the relationship between the injection speed and the injection pressure (resin pressure) has a correlation.Feedback controlWhen the injection control is performed in step (a), a pressure waveform as shown in FIG. 11 (pressure waveforms detected by the sensors Se1 and Se4) is obtained. In this pressure waveform, the peak pressure shown in FIG. Edit the pressure waveform as shown in (a), and use this pressure waveform pattern as the injection pressure command pattern.feedbackWhen the control was performed, the injection speed obtained when the injection speed at the time of generation of the peak pressure shown in FIG. 11A was changed as shown in FIG. 12A was obtained. This indicates that, if the injection pressure command pattern is corrected, the injection speed changes accordingly, and conversely, if the injection speed is changed, the injection pressure waveform also changes.
[0019]
Therefore, the injection speed is increased from 20 mm / s to 60 mm / s in increments of 5 mm / s to maintain a constant injection speed.Feedback controlWhen the injection pressure detected by the load cell pressure sensor Se1 is obtained based on the screw position, the result shown in FIG. 13 is obtained. From FIG. 13, it can be seen that the injection pressure increases as the injection speed increases, and that even if the injection speed is constant in all sections, the change in pressure is not temporary, and the injection speed and the injection pressure have a non-linear relationship. .
[0020]
Therefore, when trying to control the injection pressure by the injection speed, the following must be considered from the above.
(1) In the initial stage of the filling, the resin is in a flowing state in which the resin flows while flowing in the mold. Therefore, high responsiveness is required for the pressure control at this stage.
(2) Since the resin is compressed in the portion where the resin flow path in the mold is narrow, even a small change in speed appears as a large change in pressure. For this reason, if the responsiveness is too good, the oscillation occurs conversely, and the control system becomes unstable.
(3) The latter stage of the filling is a compression filling step for compensating for the cooling shrinkage of the resin. In this step, the flow of the resin is almost stopped, and the force applied to compensate for the shrinkage is detected in a state where there is no compression loss, so that there is almost no need for speed responsiveness.
[0021]
In order to construct a control system using the above knowledge of the nonlinear relationship between speed and pressure, the control system is classified into sections that can be linearly approximated, and control is performed by finding the optimal control gain in each section. The gain schedule method can be applied, but in injection molding, there are many parts that depend on the factors of the resin to be molded and the factors of the mold, and these factors will change if the product to be molded is different, and will vary from product to product. The linear control section and the gain must be reviewed, and it is difficult to apply the gain schedule method.
[0022]
Therefore, the present invention provides injection speed control and injection pressure control.TheAt the same time, the problem was solved by applying fuzzy control to the above-described nonlinear relationship between the injection speed and the injection pressure.
[0023]
As described above, in order to perform optimal pressure control in the injection process, it is necessary to set the optimal injection speed or injection pressure by knowing the resin flow conversion point in the mold and the resin filling rate in the mold. For this purpose, in the present embodiment, first, an injection speed that is expected to be appropriate in molding by the mold is set based on the screw position, and the injection speed is adjusted.Feedback controlTo perform injection control a plurality of times. Then, the pressure deviation between shots is obtained in time series. FIG. 14 shows the pressure deviation between shots ((2) in FIG. 14) thus obtained by the load cell pressure sensor Se1 and the injection pressure ((1) in FIG. 14) detected by the load cell pressure sensor Se1. It is a detection example.
[0024]
In FIG. 14, large peaks of the pressure deviation occur at three places and vary. The large appearance of the pressure deviation is a part that is vulnerable to a disturbance in which feedback compensation in speed control is difficult at this point. It can be presumed that it corresponds to a portion where the flow path in the mold changes narrowly. As a result, as shown in FIG. 15, it is possible to obtain a value of a membership function in fuzzy control based on the screw position with respect to the influence of the disturbance (the influence of the mold shape).
[0025]
Further, at the time of the plurality of shots, the relationship between the screw position and time is detected, and the positional deviation between the shots is obtained. FIG. 16 is a graph showing the obtained screw position (1) and the positional deviation (2) of each shot. It can be seen that a position deviation occurs from the part (A) of FIG. 16 and that the position deviation varies. It is determined that this is because the speed cannot be followed in the vicinity of the completion of the filling, or that the speed varies due to the dwell control. From FIG. 16, the filling rate of the resin, that is, the value of the membership function of the speed following ability can be obtained as shown in FIG.
[0026]
The value of the membership function shown in FIG. 15 is caused by the flow resistance at the flow conversion point. At this point, as described above, the gain of the control system is reduced (the lower the gain, the smaller the variation in the pressure deviation). It is necessary to stabilize the control system. Further, the value of the membership function shown in FIG. 17 indicates the effect of the filling rate of the resin, and as described above, the response of the speed may be very small, which means that the gain is reduced. I do. As a result, a control input amount to be input to the control target is obtained from the two membership functions. That is, in this case, the amount of decrease in gain is obtained. In ordinary fuzzy control, the smaller value of the membership function is adopted, but in the present invention, the larger value of the membership function is used because the gain is reduced. As a result, a gain function (in-mold pressure response) as shown in FIG. 18 is obtained. The gain is adjusted using FIG.Feedback controlIt is also possible to formfeedbackBecause it is difficult to adjust the control parameters, in the present invention, the pressurefeedbackControl andbothInjection speedfeedbackcontrolRowThe control is performed by superimposing the gain function based on FIG. 18 on the speed command. That is, the speed command is reduced by an amount corresponding to this function (the value of the membership function) based on the gain function shown in FIG. Decreasing the speed command is equivalent to substantially lowering the gain, and lowering the speed also lowers the injection pressure. Pressure and position fluctuations can be prevented.
[0027]
FIG. 2 shows the speed according to the speed command corrected by the method described above.feedbackControl and injection pressure command patternFeedback controlFIG. 3 is a block diagram of a drive control system of an injection servomotor to be implemented. A value obtained by multiplying a deviation between the detected injection pressure currently detected by the load cell pressure sensor Se1 and the injection pressure command Pc by a predetermined proportional gain K is added to the corrected speed command Vc for each predetermined cycle. SpeedFeedback controlSpeed command and the same speed as beforefeedbackProcessing, and furthermore, the currentfeedbackBy controlling and driving the injection servomotor M2 via the servo amplifier 15, the speed is controlled so that the injection pressure detected by the load cell pressure sensor Se1 matches the injection pressure command Pc.
[0028]
FIG. 1 is a block diagram showing a main part of an electric injection molding machine 30 for carrying out an embodiment of the present invention by the above-described method. Reference numeral 33 denotes a fixed platen to which a fixed mold 39 is attached, and reference numeral 32 denotes Denotes a movable platen to which the movable mold 39 is attached, reference numeral 34 denotes an injection cylinder, and reference numeral 35 denotes a screw. The movable platen 32 is moved along a tie bar (not shown) of the injection molding machine 30 by a shaft output of the mold clamping servo motor M1 via a mold clamping mechanism 31 including a ball nut & screw, a toggle mechanism, and the like. . The screw 35 is driven in the axial direction by an injection servomotor M2 via a drive conversion device 37 for converting the rotation of the drive source into a linear motion in the direction of the injection axis, and via a gear mechanism 36. The metering rotation is performed by the screw rotation servomotor M3. A load cell pressure sensor Se1 is provided at the base of the screw 35, and detects the resin pressure acting in the axial direction of the screw 35, that is, the injection pressure in the injection process and the screw back pressure in the metering and kneading process. The injection servomotor M2 is provided with a pulse coder P2 for detecting the position and the moving speed of the screw 35, and the mold clamping servomotor M1 is provided with a toggle head of the mold clamping mechanism 31 for driving the movable platen 32. A pulse coder P1 for detecting a position is provided.
[0029]
The control device 10 that drives and controls the injection molding machine 30 includes a CNC CPU 25 that is a microprocessor for numerical control, a CPU 18 for a PMC that is a microprocessor for a programmable machine controller, a servo CPU 20 that is a microprocessor for servo control, and A pressure monitor CPU 17 for sampling the injection pressure and the screw back pressure via the load cell pressure sensor Se1 and the A / D converter 16, and by selecting mutual input / output via the bus 22. Information can be transmitted between the microprocessors.
[0030]
A ROM 13 storing a sequence program for controlling a sequence operation of the injection molding machine and a RAM 14 used for temporary storage of operation data and the like are connected to the CPU 18 for the PMC, and the injection molding machine 30 is generally connected to the CPU 25 for the CNC. A ROM 27 storing a control program and the like and a RAM 28 used for temporary storage of operation data and the like are connected.
[0031]
Each of the servo CPU 20 and the pressure monitoring CPU 17 has a ROM 21 storing a control program dedicated to servo control, a RAM 19 used for temporary storage of data, and a ROM 11 storing a control program related to molding data sampling processing and the like. A RAM 12 used for temporary storage of data is connected. Further, the servo CPU 20 is connected to a servo amplifier 15 for driving servo motors of respective axes for ejector (not shown), for mold clamping, for injection, for screw rotation, etc. based on a command from the CPU 20. Each output from the pulse coder P1 provided to the mold clamping servomotor M1 and the output from the pulse coder P2 provided to the injection servomotor M2 is fed back to the servo CPU 20, and the type calculated by the servo CPU 20 based on the feedback pulse from the pulse coder P1. The current position of the toggle head of the tightening mechanism 31 and the moving speed and the current position of the screw 35 calculated by the servo CPU 20 based on the feedback pulse from the pulse coder P2 are stored in the current position storage register and the current speed storage register of the RAM 19, respectively. Is updated and stored .
[0032]
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 and transmitting various commands to peripheral devices of the injection molding machine. 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. And various function keys.
[0033]
The nonvolatile memory 24 is a memory for storing molding data (injection conditions, weighing and kneading conditions, etc.) and various set values, parameters, macro variables, and the like relating to the injection molding operation. The non-volatile memory 24 further stores the corrected speed command pattern and injection pressure command pattern.
[0034]
According to the above-described configuration, first, an injection speed pattern which is considered to be optimal for the mold and resin to be used is set in correspondence with the screw position, and is stored in the nonvolatile memory 24. The injection speed pattern considered to be optimal is a correction that seems to be suitable by referring to the mold used, the mold similar to the resin, the injection speed pattern set when a good molded product is obtained with the resin, etc. Set while adding.
[0035]
When the injection speed pattern and the injection pressure pattern setting command are input after performing a plurality of discard shots, the control device 10 starts a molding operation for obtaining the injection speed pattern and the injection pressure pattern. In the injection step, the CNC CPU 25 reads out the injection speed pattern for each set period and outputs the speed command Vci of the period to the servo CPU 20.Feedback controlStarts the process of removing. That is, based on the speed command Vci and the actual speed of the servomotor detected and fed back by the pulse coder P2, a speed similar to the conventional speed is obtained.feedbackA torque command is obtained by performing a process, and based on the torque command and a feedback signal of a drive current detected by a current detector (not shown), a currentfeedbackThe control is performed to drive the injection servomotor M2 via the servo amplifier 15.
[0036]
On the other hand, when the injection speed pattern and the injection pressure pattern setting command are input, the pressure monitoring CPU 17 starts the processing shown in FIGS. 3 and 4, first, the counter C, the flag f1, the injection start, the injection, and the pressure holding. Is set to “0” in the storage unit Ai (ΔP) (where i = 1 to m) prepared for the number m of sampling cycles until the completion of the above, and the number m of the sampling cycles is set in the register I (Step S1). The sampling cycle is the same as the cycle at which the CNC CPU 25 outputs the speed command.
[0037]
Next, the index i, the flag f2, and the register B for obtaining the command screw position are set to "0" (step S2), and it is determined whether or not the flag F indicating injection is set to "1". Is set to "1" (step S3). The flag F is a flag that is set when the PMC CPU 18 outputs an injection start command to the CNC CPU 25 according to the sequence program, and is reset when the CNC CPU 25 completes the injection process. ing. The initial value of the flag F is 0 in the reset state.
[0038]
When the flag F indicating that the injection is being performed is set to "1", the sampling period is set in the timer T and started, and the system waits for the timer T to expire (steps S4 and S5). When the timer T expires, the sampling cycle is set again in the timer T, and the timer T is started again, the index i is incremented, and the injection pressure detected from the load cell pressure sensor Se1 via the A / D converter 16 and the servo pressure are increased. The current position of the screw stored in the current value storage register in the RAM of the CPU 20 is read as the detected pressure P (i) of the sampling period indicated by the index i and the screw position Pos (i) (steps S6 and S7). , S8).
[0039]
Then, it is determined whether or not the flag f1 is "0". Since the flag f1 is initially set to "0" in step S1, the process proceeds to step S10 to store the reference injection pressure of the file FL2 provided in the RAM 12. The detected pressure P (i) is stored as a reference injection pressure Pc (i) at a position corresponding to the address i of the section.
[0040]
FIG. 5 is a diagram for explaining the configuration of the files FL1 and FL2. FL1 is a file stored in the nonvolatile memory 24. The file FL1 contains a set injection speed command Vc (i) for each sampling cycle. In addition to being stored at each address, the reference injection pressure Pc (i) is also stored for each address. FL2 is a file provided in the RAM 12. The file includes, for each address, a reference injection pressure Pc (i), an integrated value Ai (ΔP) of pressure deviation described later, first and second memberships. The speed command correction value (gain function) γi obtained from the function values αi, βi and the first and second membership function values αi, βi is stored in each address.
[0041]
Next, it is determined whether or not the index i is smaller than the number m of samplings performed for each sampling cycle during the injection (including pressure holding) process (step S19). Therefore, the process proceeds to step S5, and the processes of steps S5 to S10 and step S19 are repeated until the index i reaches the sampling number m, and the reference injection pressure Pc (i) is detected and stored in the file FL2. I do.
[0042]
Thus, when the injection and pressure-holding steps are completed and the index i reaches m, the flag f1 indicating that the first injection step, which is the pattern detection processing of the reference injection pressure Pc (i), is set to "1". Then, the counter C for counting the injection process (shot) is incremented (steps S20 and S21), and it is determined whether or not a molding condition change command is input (step S22). The process in step S22 is for responding to a case where a molding condition change command is input to change the molding condition again, even though the operator has started the injection speed pattern and injection pressure pattern setting process. If this command has been input, this process is terminated as it is, and the process from step S1 is started again based on the input of the injection speed pattern and injection pressure pattern setting command.
[0043]
If the molding condition change command has not been input, the flow shifts to step S23 to determine whether or not the value of the counter C has reached a preset set value C0. If not, the flow returns to step S2. , The process from step S2 onward is started. In this case, since the flag f1 has already been set to “1” in step S20, the process proceeds from step S9 to step S11, and the sampling period (step S11) stored in the file FL2 The injection pressure P (i) detected in step S8 is subtracted from the reference injection pressure Pc (i) corresponding to the cycle indicated by the index i, and the reference injection pressure Pc (i) and the detected pressure P (i) in the cycle are determined. ) Is obtained, and the deviation ΔP (i) is added to the storage value of the storage unit Ai (ΔP) provided in the file FL2 and storing the integrated value of the pressure deviation in the cycle. And, stored in the storage unit (step S11, S12).
[0044]
Next, it is determined whether or not the flag f2 for storing the position deviation increase point detection is “0” (step S13). Since the flag f2 is initially set to “0” in step S2, the process proceeds to step S14. The speed command Vci of the cycle is multiplied by the sampling cycle T and added to the register B for obtaining the screw command position. As shown in FIG. 7 and FIG.feedbackWhen the control is being performed, the screw position completely follows the command at the initial stage when the filling rate of the resin into the mold is low. Therefore, the value obtained by multiplying the speed command value Vci of each sampling cycle by the sampling cycle T is used. If added, the screw position commanded by the speed command is obtained. Then, the current screw position detected in step S8 is subtracted from the screw command position stored in the register B to obtain a position deviation, and it is determined whether the position deviation is equal to or greater than the set value ε (step S15). In the initial state of the start of injection, the filling rate of the resin into the mold is low. In this state, the screw follows the command as shown in FIG. At this time, the process proceeds to step S19, and it is determined whether or not the index i has reached m. If not, the process proceeds to step S5, and the processes of steps S5 to S9, S11 to 15, and S19 are repeatedly performed. The pressure deviation is integrated in the storage unit Ai (ΔP), and it is determined whether the position deviation is equal to or larger than the set value ε.
[0045]
The resin is filled in the mold and the filling rate increases, and as shown in FIG. 16, a deviation occurs between the commanded screw position and the actual screw position, and the position deviation (B-Pos (i)) is set to the set value ε. Then, the process proceeds from step S15 to step S16, and it is determined whether or not the index i at that time is smaller than the value stored in the register I (this initial value is set to m in step S1). The value of the index i is stored in the register I (step S17), the flag f2 is set to "1" (step S18), and if the index i is smaller than m, the process returns to step S5 again, and the above-mentioned steps 5 and below are performed. Execute the process. If the value of the index i is equal to or greater than the value stored in the register I in step S16, the process proceeds to step S18 without rewriting the register I.
[0046]
Thereafter, the processing from step S5 is executed until the index i reaches m, and the pressure deviation from the reference injection pressure is integrated in the storage unit Ai (ΔP) of each address i of the file FL2. , The process proceeds from step S13 to step S19, and the process of detecting the position deviation increase position (steps S14 to S18) is not executed. Thus, when the index i reaches m, the processing of the above-described steps S20 to S23 is performed, and when the value of the counter C has not reached the set value C0, the above-described processing of step S2 and the following steps is executed again. Thereafter, the processing of steps S2 to S23 is repeated until the value of the counter C reaches the set value C0, and the pressure deviation at each address i is integrated into the storage unit Ai (ΔP) of each address i that stores the pressure deviation ΔP ( Along with step S12), the smallest value of the index i when the position deviation (B-Pos (i)) exceeds ε is stored in the register I (steps S15 to S18).
[0047]
When the value of the counter C reaches the set value C0, the maximum value MaxA of the absolute value of the integrated value of the pressure deviation from the reference injection pressure stored in each storage unit Ai (ΔP) of the file FL2 is obtained (step S24). The maximum value MaxA is divided by a value ignoring the sign of the integrated value of the pressure deviation stored in the storage unit Ai (ΔP) of each address, and the membership function 1 based on the pressure deviation with the maximum value being “1” is obtained. The value αi (the sign of αi is always positive) is obtained and stored in the file FL2 (step S25).
[0048]
A shot (injection) is performed with the same speed command pattern, and the fact that the integrated value of the pressure deviation from the injection pressure waveform obtained in the first shot and the injection pressure of the subsequent shot is large means that the integrated value is large. This means that the injection pressure varies at the screw position (address i), which indicates that the resin flow resistance is large due to a narrow resin flow path and the control is unstable. As a result, the magnitude of the value αi of the membership function 1 indicates the degree of the control instability. As will be described later, the speed command Vc is reduced at this position to perform stable control. Let it.
[0049]
Next, a value βi of the membership function based on the position deviation that is increased from the address position of the position where the position deviation stored in the register I is increased to 1 at a set ratio (1 / q) is obtained, and the obtained value is stored in the file FL2. It is stored (step S26). That is, assuming that the value stored in the register I is I for convenience, the value βi of the membership function is “0” and the value of the membership function of the address I is “0” when the address i is 1 to (I−1). β (I) is “1 / q”, the value β (I + 1) of the membership function of the next address (I + 1) is “2 / q”, and β (I + 2) = 3 / q,. 1) = q / q = 1, and subsequent β (I + q) to βm are set to “1”.
[0050]
Then, the larger of the two membership function values αi and βi is determined for each address as a value γi as a control input amount for correcting the injection speed command, and stored in the file FL2 (step S27). .
Next, a corrected injection speed command is obtained at each address position by subtracting a value obtained by multiplying the control input amount γi thus obtained by the set proportional constant k from the injection speed command Vci, and is stored in the file FL1 of the nonvolatile memory 24. Injection pressure stored in file FL2 after rewriting injection speed command VciPc (i)Is stored in the file FL1 of the nonvolatile memory 24 and the injection pressure commandPattern Pc (i)(Steps S28 and S29), and the injection speed pattern and injection pressure pattern setting processing ends.
[0051]
As described above, the control input amount γi based on the membership function values αi and βi causes the flow resistance of the resin to fluctuate due to narrowing of the resin flow path and the like, so that the control becomes unstable. A speed command pattern in which the command speed Vci is reduced can be obtained from a position where the resin filling rate in the mold increases and the screw cannot follow the command.
[0052]
After the injection speed pattern and the injection pressure pattern are set in this way, when a continuous molding command is input to the injection molding machine, when the injection process is started, the CNC CPU 18 sets the speed stored in the file FL1 for each sampling cycle. The command Vci is output to the servo CPU 20, and the servo CPU 20 controls the injection speed shown in FIG.feedbackProcessing and injection pressurefeedbackExecute the process. That is, the servo CPU 20 reads the injection pressure command Poi for each sampling cycle from the file FL1, subtracts the actual injection pressure fed back from the load cell pressure sensor Se1 from the injection pressure command Poi to obtain a pressure deviation, and sets a proportional constant to the pressure deviation. The value multiplied by K is added to the speed command Vci sent from the CNC CPU 18, a corrected speed command is obtained, and the corrected speed command and the actual speed obtained by the pulse coder P2 are fed back to obtain the same speed as the conventional speed command.feedbackA torque command is obtained by performing control, and the same current as before is obtained by the torque command and a feedback signal from the current detector.feedbackThe control is performed to drive the injection servomotor M2 to execute the injection (including the holding pressure).
[0053]
At positions where the flow resistance of the resin fluctuates due to narrowing of the resin flow path and the control becomes unstable, and where the resin filling rate in the mold increases and the screw cannot follow the command, command injection is performed. By reducing the speed, the instability of control is eliminated, stable injection control can be performed, and an injection speed command pattern and an injection pressure command pattern for easily obtaining a good molded product can be obtained.
[0054]
In the above embodiment, when the value αi of the membership function is obtained, the position where the pressure deviation ΔP occurs is determined as the position where the control becomes unstable due to narrowing of the resin flow path at that position. The value αi of the membership function was determined from the value Ai (ΔP) obtained by integrating the deviation ΔP. That is, in each position where the pressure deviation ΔP occurs, the pressure deviation having the same sign is generated, and it is sufficient to simply integrate the pressure deviation ΔP. However, at the same screw position, there is variation in the pressure deviation, and positive and negative pressure deviations occur. When the pressure deviation ΔP is integrated, the positive and negative pressure deviations cancel each other out, and a small integrated value, or “0” ". Therefore, in order to make it more accurate, the sign of the pressure deviation ΔP is ignored by integrating the absolute value of the pressure deviation ΔP obtained in step S11 of FIG. 3 into the storage unit Ai (ΔP), and the variation of the pressure deviation ΔP is reduced. The integrated value of the absolute value of the pressure deviation ΔP in the considered steps S24 and S25 and the membership function value αi based on the integrated value of the absolute value of the pressure deviation ΔP may be obtained.
[0055]
Further, at a screw position, a phenomenon may occur in which a positive pressure deviation ΔP occurs at each shot at a certain position, and a negative pressure deviation ΔP occurs at each shot at another position. Even in this case, in the above-described embodiment, the position where the pressure deviation ΔP occurs is a position where the control is unstable, and the value αi of the membership function is determined so as to decrease the command injection speed. However, when the pressure deviation ΔP is negative (Pc (i) <P (i)), the command injection speed command is determined to be too high in the reference injection pressure pattern, and the speed command is reduced. (Pc (i)> P (i)) indicates that the command injection speed command can be increased to a low value, and the value αi of the positive / negative member sheep function is obtained in accordance with the sign of the integrated value of the pressure deviation ΔP. VCi may be increased or decreased.
[0056]
【The invention's effect】
According to the present invention, an injection speed command pattern and an injection pressure command pattern can be easily obtained by a plurality of injection moldings. Moreover, instead of setting a non-linear gain such as lowering the gain for a place where the control system becomes unstable, for a control object that differs depending on the type of the mold or resin, the place where the control system becomes unstable is used. Therefore, it is not necessary to change the gain of the control system, and the gain of this control system can be made larger than that of the conventional control system. Can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram of a main part of an electric injection molding machine according to one embodiment for implementing an injection control method of the present invention.
FIG. 2 is a block diagram of a servo motor control system in the embodiment.
FIG. 3 is a part of a flowchart of a process for obtaining an injection speed command pattern and an injection pressure command pattern in the embodiment.
FIG. 4 is a continuation of the flowchart.
FIG. 5 is an explanatory diagram of a file provided in a memory in the embodiment.
FIG. 6 is an explanatory diagram illustrating a mounting position of a pressure sensor in an experiment for detecting a resin pressure.
FIG. 7 shows the injection speedfeedbackFIG. 9 is a diagram illustrating an experimental result in which an injection speed obtained by performing control and pressure detected by each pressure sensor are drawn.
FIG. 8 shows the injection pressurefeedbackFIG. 9 is a diagram illustrating an experimental result in which an injection speed obtained by performing control and pressure detected by each pressure sensor are drawn.
FIG. 9 is a diagram illustrating an experimental result obtained by measuring a variation in a time delay when each pressure sensor senses a pressure from the start of injection as a starting point.
FIG. 10 is a view showing an experimental result obtained by measuring a variation in weight of a molded product obtained by performing molding while changing a mixture ratio of a recycled material.
FIG. 11 shows the injection speedfeedbackIt is a figure which shows the injection speed waveform and injection pressure waveform of the injection | molding by control which performs the injection | molding and shows the peak in the detected injection pressure.
12 edits the injection pressure waveform of FIG. 11, and uses the injection pressure waveform having a peak as an injection pressure command pattern to obtain the injection pressure;feedbackIt is a figure which shows the injection speed waveform and the injection pressure waveform at the time of performing control.
FIG. 13: The injection speed is increased from 5 mm / s from 20 mm / s to 60 mm / s while the injection speed is constant, and the injection speed is increased.feedbackIt is a figure showing an experimental result which measured injection pressure when performing molding by control.
FIG. 14 shows the relationship between the injection speed under the same injection conditions.feedbackIt is a figure which shows the injection pressure waveform obtained by performing molding by control several times, and the injection pressure deviation in each molding.
FIG. 15 is a diagram showing values of membership functions obtained from FIG. 14;
FIG. 16 shows the relationship between the injection speed under the same injection conditions.feedbackIt is a figure which shows the screw position obtained by performing shaping | molding by control several times, and the screw position deviation in each shaping | molding.
FIG. 17 is a diagram showing values of membership functions obtained from FIG. 16;
FIG. 18 is a gain function as a control input amount obtained from FIGS. 15 and 17;
[Explanation of symbols]
10 Control device
15 Servo amplifier
17 CPU for pressure monitor
20 Servo CPU
24 Non-volatile memory
25 CNC CPU
30 Electric injection molding machine
35 screws
M2 Injection servo motor
P2 pulse coder
Se1 load cell pressure sensor

Claims (2)

In an injection control method for an injection molding machine that performs feedback control of an injection speed and feedback control of an injection pressure,
a) Perform molding by injection control only of injection speed feedback control according to the set injection speed command pattern, store the injection pressure pattern of all injection sections as a reference injection pressure pattern,
b) Thereafter, molding is performed by injection control of only the injection speed feedback control according to the set injection speed command pattern, and the absolute value of the injection pressure deviation from the reference injection pressure pattern is obtained in time series for all injection sections.
c) The above b) is performed a predetermined number of times, and the absolute values of the injection pressure deviation obtained in time series at each molding are integrated,
d) based on the integrated value of the pressure deviation and correct the injection speed command pattern, the injection speed command pattern the modified and the injection speed instruction pattern in the feedback control of the injection speed, the reference injection pressure pattern of the injection pressure An injection control method for an injection molding machine, wherein an injection pressure command pattern for feedback control is used. In an injection control method for an injection molding machine that performs feedback control of an injection speed and feedback control of an injection pressure,
a) Perform molding by injection control only of injection speed feedback control according to the set injection speed command pattern, store the injection pressure pattern of all injection sections as a reference injection pressure pattern,
b) Thereafter, molding is performed by injection control of only the injection speed feedback control according to the set injection speed command pattern, an injection pressure deviation from the reference injection pressure pattern is obtained in time series for all injection sections, and a screw command is issued. The time when the position deviation between the position and the actual position becomes equal to or greater than the set value is stored as a position deviation increase point,
c) and b) are performed a predetermined number of times, and the injection pressure deviation obtained in time series at each molding is integrated, and the minimum screw advance position at the position deviation increase point is obtained.
d) On the basis of the ratio between the integrated value of the injection pressure deviation obtained in time series and the maximum value of its absolute value, and after the minimum screw advance position obtained in the above c), the ratio is preset to the ratio. The correction value of the injection speed command pattern is obtained based on the value increased in time series at the set ratio ,
e) The injection speed command pattern is corrected based on the obtained correction value, the corrected injection speed command pattern is used as the injection speed command pattern in the injection speed feedback control, and the reference injection pressure pattern is used as the injection pressure command pattern. An injection control method for an injection molding machine, wherein an injection pressure command pattern for feedback control is used.

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