JP5460355B2 - Control device for injection molding machine having correlation coefficient calculation function - Google Patents

Description

  The present invention relates to an injection molding machine, and more particularly, to a control device for an injection molding machine having a correlation coefficient calculation function.

  Conventionally, as a method for determining the quality of a molded product, a method for detecting a screw position, a method for detecting an injection pressure, and the like are known. For example, when determining the quality of a molded product by detecting the screw position, it detects the screw position (cushion amount) or the screw most advanced position (minimum cushion amount) at the end of pressure holding, which is the final stage of injection. It has been known. In addition, when the injection pressure is detected to determine the quality of a molded product, one that mainly detects the peak injection pressure in the injection process is known. In these, the detection timing for detecting the screw position and the injection pressure is fixed.

  However, in injection molding operations, the screw position at the end of pressure holding, the most advanced position of the screw, and the peak injection pressure do not always determine the quality of the molded product, and depending on the shape of the molded product and the type of resin, In some cases, the screw position and injection pressure at different timings have a great influence on the quality of the molded product.

  In view of the above-described circumstances, Patent Document 1 discloses the quality of a molded product by detecting a screw position and injection pressure at an arbitrary timing from the start of injection and comparing the detected injection pressure value with a discrimination reference value. A technique for performing the discrimination is disclosed. With this technology, it is possible to determine whether a molded product is good or not based on the screw position and injection pressure detected at an arbitrary timing instead of a fixed timing.

Japanese Patent Laid-Open No. 2-78516

  However, in the technique disclosed in Patent Document 1, the timing at which the screw position and the injection pressure should be detected when setting an arbitrary timing from the start of injection is determined by the experience of the molding engineer and trial and error. There was a problem that there was no more method and it was not easy.

  Accordingly, an object of the present invention is to provide an injection molding having a correlation coefficient calculation function capable of specifying a time in a molding cycle in which the correlation is strong in the correlation between the time-series data of physical quantities related to injection molding and molding quality. It is to provide a control device for the machine. Furthermore, the present invention determines the quality of a molded product by calculating timing within a molding cycle at which the correlation between molding quality and time-series data of physical quantities related to injection molding such as injection pressure and screw position is strong. The purpose is to identify the optimal timing. Another object of the present invention is to improve the molding quality itself by controlling and stabilizing physical quantities related to injection molding such as injection pressure and screw position at the timing when the correlation with the molding quality becomes strong.

The invention according to claim 1 of the present application includes a physical quantity detection unit that detects a physical quantity related to injection molding at a predetermined sampling time interval, and a physical quantity detected by the physical quantity detection unit over a plurality of cycles as time series data of the predetermined sampling time interval. Injection molding comprising physical quantity storage means for storing, molding quality data detection means for detecting molding quality data, and molding quality data storage means for storing molding quality data detected by the molding quality data detection means over a plurality of cycles Among the physical quantity time series data stored by the physical quantity storage means, physical quantities at the same time between shots, and molding quality data between shots stored by the molding quality data storage means, Is calculated as the correlation coefficient at the same time. With the correlation coefficient calculating means is a control device for an injection molding machine, characterized in that sequentially calculates a correlation coefficient for each time of the predetermined sampling time interval by the correlation coefficient calculating means.

The invention according to claim 2 obtains a time at which the absolute value of the correlation coefficient sequentially calculated by the correlation coefficient calculating means is maximized, and based on a physical quantity related to injection molding at the obtained time, The control apparatus for an injection molding machine according to claim 1, wherein quality determination is performed. The invention according to claim 3 determines the time when the absolute value of the correlation coefficient sequentially calculated by the correlation coefficient calculation means becomes maximum, and based on the physical quantity related to injection molding at the determined time, the injection holding pressure 2. The injection molding machine control device according to claim 1, wherein the switching position or the injection speed switching position is corrected.
The invention according to claim 4 is a section in which the absolute value of the correlation coefficient sequentially calculated by the correlation coefficient calculation means is compared with a predetermined value, and the absolute value of the correlation coefficient calculated sequentially is a predetermined value or more. The control device for an injection molding machine according to claim 1, wherein feedback control of a physical quantity related to injection molding is performed in the section .

In the invention according to claim 5, the physical quantity related to the injection molding is: injection pressure, screw position, screw speed, in-mold pressure, ejector position, ejector thrust, mold platen position, mold platen thrust, mold parting surface interval, The control device for an injection molding machine according to any one of claims 1 to 4, wherein the control device is any one of a clamping force and a mold temperature.
The invention according to claim 6 is characterized in that the molding quality data is detected from the data capable of directly evaluating the molding quality detected from the molded product itself, or detected from a physical quantity during the molding process, and indirectly the quality of the molded product. The control apparatus for an injection molding machine according to any one of claims 1 to 4, characterized in that the data can be evaluated.
The invention according to claim 7 is the control device for an injection molding machine according to any one of claims 1 to 6, wherein the sequentially calculated correlation coefficient is displayed on a screen as a waveform.

According to the present invention, in the correlation between physical quantity time series data related to injection molding and molding quality, control of an injection molding machine having a correlation coefficient calculation function capable of specifying a time in a molding cycle where the correlation is strong Equipment can be provided.
Further, according to the present invention, the quality of the molded product is determined by calculating the timing within the molding cycle in which the correlation between the time series data of the physical quantity related to injection molding such as injection pressure and screw position and the molding quality becomes strong. The optimum timing can be specified.
Furthermore, the molding quality itself can be improved by controlling and stabilizing physical quantities related to injection molding such as injection pressure and screw position at the timing when the correlation with the molding quality becomes strong.
In Japanese Patent Laid-Open No. 3-199025, measurement data of a plurality of predetermined monitor items are captured and stored for each shot during continuous automatic operation, and any of the captured plurality of monitor items is stored. A technique for calculating a correlation between the two monitor items and outputting a correlation graph based on the calculation processing result is disclosed.
Japanese Patent Laid-Open No. 2007-196480 sequentially detects physical quantities corresponding to a plurality of different detection items related to the operation state for each shot, and obtains and displays statistical data from the detected plurality of physical quantities (detection data). In this case, one or more correlation coefficients R between detection data corresponding to two different detection items Hx, Hy,... A technique is disclosed that displays quantitatively sequentially according to display conditions and displays detected items Hx, Hy,... Corresponding to correlation coefficients R.
The techniques disclosed in these patent documents calculate the correlation between any two monitor items of a plurality of monitor items and output a correlation graph or rearrange them in the order of higher correlation coefficients. It is possible to know which items have a strong correlation, but all are to calculate the correlation coefficient for the data measured at a fixed timing, and to correlate with the molding quality within the molding cycle. It does not specify the timing when becomes stronger.

It is a schematic block diagram of the injection molding machine which is one Embodiment of this invention, and the control apparatus which controls this injection molding machine. It is a figure explaining measuring injection pressure which is a physical quantity concerning injection molding as time series data for every shot. It is the figure which represented the time series data of the injection pressure in a molding cycle for each shot in the graph. It is a figure explaining measuring the minimum amount of cushions which is data which can evaluate the quality of a molded article indirectly for every shot. It is a figure explaining calculating the correlation coefficient of an injection pressure and the minimum cushion amount for every time. It is the figure which represented the time-series data of the injection pressure in a molding cycle for every shot on a graph, and also represented the correlation coefficient of the injection pressure calculated for every time and the minimum cushion amount on the graph. As an example of a case where the absolute value of the correlation coefficient is large, it is a diagram illustrating the relationship between the injection pressure and the minimum cushion amount for each shot at time t1. As an example when the absolute value of the correlation coefficient is small, it is a diagram for explaining the relationship between the injection pressure and the minimum cushion amount for each shot at time t2 when the correlation coefficient is R (t2). It is a figure explaining the quality determination based on the pressure in the time when the absolute value of the correlation coefficient calculated sequentially becomes the maximum. It is a figure explaining the algorithm of the process which performs the quality determination based on the pressure in the time when the absolute value of the correlation coefficient calculated sequentially becomes the maximum. It is a flowchart which shows the algorithm of the process which calculates a correlation coefficient. It is a figure explaining the algorithm of the process which correct | amends the injection | pouring holding pressure switching position based on the pressure in the time when the absolute value of the correlation coefficient calculated sequentially becomes the maximum (the 1). It is a figure explaining the algorithm of the process which correct | amends the injection | pouring holding pressure switching position based on the pressure in the time when the absolute value of the correlation coefficient calculated sequentially becomes the maximum (the 2). It is a figure explaining the algorithm of the process which correct | amends the injection / holding pressure switching position with the absolute value of the correlation coefficient calculated sequentially (the 1). It is a figure explaining the algorithm of the process which correct | amends the injection / holding pressure switching position with the absolute value of the correlation coefficient calculated sequentially (the 2). It is a figure explaining controlling a holding | maintenance area by the absolute value of the correlation coefficient calculated sequentially (the 1). It is a figure explaining controlling a holding | maintenance area by the absolute value of the correlation coefficient calculated sequentially (the 2).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an injection molding machine and a control device that controls the injection molding machine. A nozzle 2 is attached to the tip of the cylinder 1 into which the screw 3 is inserted, and a hopper 4 for supplying resin pellets to the cylinder 1 is attached to the rear end of the cylinder 1. The screw 3 is driven in the axial direction by a conversion mechanism 8 that converts a rotary motion of the injection servomotor M1, a transmission mechanism 7, and a ball screw / nut, etc., as a drive means for driving the screw 3 in the axial direction thereof, into a linear motion, Injection and back pressure control are performed. The screw 3 is rotationally driven by a servo motor M2 for rotating the screw 3 as a rotational driving means and a transmission mechanism 6 including a belt, a pulley and the like.

  A position / speed detector Penc1 and a position / speed detector Penc2 for detecting the rotation position / speed are attached to the injection servo motor M1 and the screw rotation servo motor M2, respectively. These position / speed detectors Penc1 and Penc2 can detect the position of the screw 3 (position in the screw axis direction), the moving speed (injection speed), and the rotational speed of the screw 3. In addition, a pressure sensor 5 such as a load cell that detects the pressure in the axial direction of the screw from the molten resin applied to the screw 3 is provided.

  Connected to the PMCCPU 17 are a ROM 18 storing a sequence program for controlling the sequence operation of the injection molding machine and a RAM 19 used for temporary storage of calculation data. Connected to the CNC CPU 20 are a ROM 21 that stores an automatic operation program and the like for overall control of the injection molding machine, and a RAM 22 that is used for temporary storage of calculation data.

  The servo CPU 15 is connected to a ROM 13 that stores a control program dedicated to servo control that performs processing of a position loop, a speed loop, and a current loop, and a RAM 14 that is used for temporary storage of data. Further, the servo CPU 15 is driven by a servo amplifier 12 that drives a screw rotating servo motor M2 or an injection servo motor M1 that drives the screw 3 in the axial direction to perform injection or the like based on a command from the servo CPU 15. Servo amplifier 11 is connected.

  As described above, the position / speed detectors Penc1 and Penc2 are attached to the servomotors M1 and M2, respectively. Outputs from these position / velocity detectors Penc 1 and Penc 2 are fed back to the servo CPU 15.

  The servo CPU 15 is fed back from the movement command to each axis (injection servo motor M1 or screw rotation servo motor M2) commanded by the CNC CPU 20 and the position / speed detector Penc1 and position / speed detector Penc2. Based on the detection position and detection speed, position and speed feedback control is performed, and current feedback control is also executed to drive-control the servo amplifiers 11 and 12. Further, a current position register for obtaining the forward position (axial position) of the screw 3 by a position feedback signal from the position / speed detector Penc1 is provided, and the screw position can be detected by the current position register. ing.

  Further, the servo CPU 15 receives a resin pressure (resin pressure applied to the screw) obtained by converting the detection signal from the pressure sensor 5 into a digital signal by the A / D converter 16.

  An input device 25 with a display device having a display device composed of a liquid crystal display device or the like is connected to a bus 26 via a display circuit 24. Further, a molding data storage RAM 23 composed of a nonvolatile memory is also connected to the bus 26. The molding data storage RAM 23 stores molding conditions relating to injection molding work, various set values, parameters, macro variables, and the like.

  With the above configuration, the PMC CPU 17 controls the sequence operation of the entire injection molding machine, and the CNC CPU 20 controls the servo motors M1 and M2 for each axis based on the operating conditions stored in the ROM 21 and the molding conditions stored in the molding data storage RAM 23. The servo CPU 15 distributes the movement command to each axis (servo motor M1 for injection and servo motor M2 for rotation of the screw 3) and the position / speed detectors Penc1 and Penc2. Based on the detected position and velocity feedback signals and the like, servo control of position loop control, velocity loop control, and current loop control is performed in the same manner as in the past, and so-called digital servo processing is executed.

  The configuration described above is the same as the control device of the conventional electric injection molding machine, and the difference from the conventional one is that the embodiment of the present invention is related to the correlation between the time series data of physical quantities related to injection molding and the molding quality. Is provided with a correlation coefficient calculation function capable of specifying a time within a molding cycle in which is strong.

  FIG. 2 is a diagram for explaining the measurement of injection pressure, which is a physical quantity related to injection molding, as time-series data for each shot. In FIG. 2, the injection pressure is measured as a physical quantity related to injection molding at time t0, t1, t2,..., Tn-1, tn at predetermined sampling time intervals for each shot, and time series data from the start of each cycle. As shown, the injection pressure data is acquired. In the following description, an injection pressure will be described as an example of a physical quantity related to injection molding.

  As physical quantities related to injection molding, in addition to injection pressure, for example, screw position, screw speed, in-mold pressure, ejector position, ejector thrust, mold platen position, mold platen thrust, mold parting surface interval, mold clamping There is power, mold temperature. Each physical quantity is conventionally used for controlling an injection molding machine in an injection molding machine. Moreover, since the measuring method and means of each physical quantity are well-known, description is abbreviate | omitted.

  FIG. 3 is a graph showing time-series data of injection pressure in a molding cycle for each shot. In FIG. 3, the physical quantity (injection pressure is taken as an example in FIG. 3) is the vertical axis, and the horizontal axis is time t0, t1, t2,... Tn-1, tn, and is shown for each shot.

Next, data capable of evaluating molding quality will be described.
Data that can be used to evaluate molding quality is data that can be detected directly from the molded product and can be directly evaluated (eg, product weight, product dimensions, product strength, optical properties, etc.), or physical quantities during the molding process. Data that can be detected and can indirectly evaluate the quality of the molded product (for example, minimum cushion amount, peak pressure, metering time, metering torque, peak value of in-mold pressure, backflow value, etc.) as molding quality data for each shot To measure. FIG. 4 is a diagram for explaining the measurement of the minimum cushion amount, which is data that can indirectly evaluate the quality of the molded product, for each shot.

Of the time series data of the measured physical quantity, the correlation coefficient between the physical quantity at the same time between shots and the molding quality data for each shot is used as the correlation coefficient at the same time for each time of the predetermined sampling time interval. Calculate sequentially.

  The correlation coefficient can be calculated by, for example, Formula 1.

  FIG. 5 is a diagram illustrating that the correlation coefficient between the injection pressure and the minimum cushion amount is calculated for each time. As shown in FIG. 5 by Equation 1, the correlation coefficient between the injection pressure and the minimum cushion amount at each time t0, t1, t2,..., Tn−1, tn for each predetermined sampling time interval is , R (t0), R (t1), R (t2),..., R (tn-1), R (tn).

  The time at which the absolute value of the correlation coefficient is maximum is calculated in the waveform of the correlation coefficient calculated by the equation (1). FIG. 6 is a graph showing the time-series data of the injection pressure in the molding cycle for each shot, and the graph showing the correlation coefficient between the injection pressure and the minimum cushion amount calculated for each time. In FIG. 6, the absolute value of the correlation coefficient is maximized at time t1. The correlation coefficient at time t1 is R (t1). In the case of negative correlation, since the correlation coefficient is a negative value, the absolute value of the correlation coefficient is taken.

FIG. 7 is a diagram for explaining the relationship between the injection pressure and the minimum cushion amount for each shot at time t1, as an example when the correlation coefficient is large. FIG. 8 is a diagram illustrating the relationship between the injection pressure and the minimum cushion amount for each shot at time t2, as an example when the correlation coefficient is small.
As described above, it is possible to specify the time in the cycle where the correlation between the physical quantity related to injection molding and the molding quality data is strongest.

  Conventionally, the quality of a molded product is determined based on a physical quantity at a fixed timing such as a peak pressure, and is not necessarily an optimal timing for evaluating molding quality. According to the embodiment of the present invention described above, the quality of the molded product can be determined based on the physical quantity related to the injection molding at the time when the absolute value of the obtained correlation coefficient is the largest. It is possible to perform pass / fail judgment at an optimal timing for evaluating the above (see FIGS. 9, 10, and 12).

  According to another embodiment of the present invention, an injection speed switching position, an injection holding pressure switching position, and the like are corrected based on a physical quantity at a time when the absolute value of the obtained correlation coefficient is maximum. It is also possible (see FIG. 13). Conventionally, a technique for correcting an injection speed switching position, an injection holding pressure switching position, and the like based on a physical quantity such as an injection pressure at a predetermined time has been known, but what time should be corrected based on a physical quantity at which time? However, there is a problem that there is no method and it is not easy to determine by the experience of the molding engineer and trial and error. According to the present invention, correction can be performed based on a physical quantity at a time having a strong correlation with molding quality.

  Further, according to another embodiment of the present invention, the absolute value of the obtained correlation coefficient is compared with a predetermined value, and an interval in which the absolute value of the obtained correlation coefficient is equal to or greater than a predetermined value is obtained. Feedback control may be applied so that the physical quantity related to the injection molding is stabilized in the section (see FIG. 14). Generally, as a control method for injection holding pressure, screw position / speed control is performed from the start of injection until reaching a predetermined screw position, and after reaching a predetermined screw position (injection holding pressure switching position), switching to pressure control is performed. Therefore, a control method for holding pressure is widely used.

  Here, there is a problem that the appropriate value of the injection / holding pressure switching position is not easy because there is no method other than to determine it by the experience of the molding engineer and trial and error. According to the embodiment of the present invention, for example, a correlation coefficient between the injection pressure and the molding quality is obtained, a time when the correlation coefficient is equal to or greater than a predetermined value is obtained, and injection holding pressure switching is performed at the time, Injection control (screw position / speed control) is performed in a section where the correlation with molding quality is weak, and pressure holding control (pressure control) can be performed in a section where the correlation with molding quality is strong.

  Furthermore, when the correlation between injection pressure and molding quality becomes weak again during holding pressure control, it can be considered that the gate has been sealed at that time. Since there is no meaning in applying the holding pressure, the holding pressure control may be discontinued at the time (see FIGS. 14-1 and 14-2).

  Also, a method for controlling the pressure inside the mold by providing a pressure sensor (not shown) in the mold is known. According to the embodiment of the present invention, the correlation coefficient between the mold internal pressure and the molding quality can be obtained, and the mold pressure control can be performed in a section where the correlation coefficient is a predetermined value or more.

  Further, a control method is known in which the resin in the cavity is compressed by ejecting the ejector during injection holding pressure (ejector compression). According to the present invention, a correlation coefficient between an ejector position or ejector thrust and molding quality can be obtained, and ejector compression control can be performed in a section where the correlation coefficient is equal to or greater than a predetermined value.

  Also, a control method is known in which a mold is opened by a predetermined amount at the start of injection, and the resin in the cavity is compressed by closing the mold during the injection process (mold compression). According to the embodiment of the present invention, it is possible to obtain a correlation coefficient between a mold platen position or a platen thrust and a molding quality, and to perform mold platen compression control in a section where the correlation coefficient is equal to or greater than a predetermined value.

  Also, a method of detecting the parting surface interval of the mold using a proximity sensor and controlling the detected value to be a predetermined interval in the mold platen compression control is also known. According to the embodiment of the present invention, the correlation coefficient between the detected value of the mold parting surface interval and the molding quality is obtained, and the mold parting surface interval is controlled in a section where the correlation coefficient is a predetermined value or more. It can be carried out.

  Further, the obtained correlation coefficient may be displayed on the screen as a waveform. The operator can set the pass / fail judgment setting and the injection holding pressure switching position with reference to the correlation coefficient waveform displayed on the screen.

In the embodiment of the present invention described above, among the time-series data of physical quantities related to injection molding, the correlation coefficient between the physical quantity at the same time from the start of the cycle between shots and the molding quality data for each shot, Although an example is described in which the correlation coefficient at the same time from the start of the cycle is sequentially calculated for each time of the predetermined sampling time interval, depending on the physical quantity related to injection molding, for example, from the start of the cycle, instead of the time from the start of the cycle The correlation coefficient may be sequentially calculated based on the time, the time from the start of pressure holding, the time from the start of measurement, the time from the start of ejection, the time from the start of mold opening, and the like. For example, in the case of obtaining the correlation coefficient between the time series data of the measured back pressure and the molding quality data for each shot, the correlation coefficient at the same time from the start of measurement between each shot is used for each predetermined sampling time interval You may make it calculate sequentially.

In the above-described embodiment of the present invention, among the time-series data of physical quantities related to injection molding, the correlation coefficient between the physical quantity at the same time between shots and the molding quality data for each shot is used as the phase coefficient at the same time. Although the example in which the number of relations is sequentially calculated for each time of the predetermined sampling time interval has been described, the correlation coefficient may be sequentially calculated for each screw position. That is, the screw position is simultaneously measured together with the physical quantity related to injection molding, and the correlation coefficient between the physical quantity at the same screw position between shots and the molding quality data for each shot is correlated with the correlation at the same screw position. The number may be calculated sequentially for each screw position.

  In addition, by changing the combination of the physical quantity related to injection molding and molding quality data and repeating the above procedure, a physical quantity having a strong correlation with molding quality is extracted from among the physical quantities related to injection molding. Can be identified. Therefore, in performing the pass / fail judgment, switching position correction, and physical quantity control, a physical quantity that has a strong correlation with molding quality is identified from a number of physical quantities related to injection molding, and then based on the identified physical quantity. Pass / fail judgment, switching position correction, and physical quantity control may be performed.

  Next, processing for calculating a correlation coefficient using a flowchart, determination of pass / fail of a molded product, injection holding pressure switching, injection holding pressure switching position correction, holding pressure section control based on the calculated correlation coefficient Will be explained.

FIG. 11 is a flowchart illustrating an algorithm of processing for calculating a correlation coefficient at each time at predetermined sampling time intervals. Hereinafter, it demonstrates according to each step.
[Step SA100] N, which is the value of the cycle counter, is set to an initial value 0.
[Step SA101] The molding cycle of the injection molding machine is started.
[Step SA102] Add 1 to N and set the value to N.
[Step SA103] During the period from the start to the end of the molding cycle in one molding cycle, the physical quantity related to injection molding is detected and stored at predetermined sampling time intervals.
[Step SA104] Molding quality data in one molding cycle is detected and stored.
[Step SA105] End one molding cycle.
[Step SA106] It is determined whether or not the cycle counter N is greater than a predetermined value. If not, the process returns to Step SA101, proceeds to the next molding cycle, and if larger, the process proceeds to Step SA107.
[Step SA107] The correlation coefficient between the physical quantity related to injection molding detected and stored in Step SA103 and the molding quality data detected and stored in Step SA104 is compared with the physical quantity related to injection molding detected and stored in Step SA103. Then, it is calculated and stored at every predetermined sampling time interval, and the process is terminated.

  One injection molding cycle includes the steps of mold closing / clamping, injection, cooling, plasticizing / metering, mold opening, and removal. In the above-described flowchart, step SA101 means starting from the mold closing / clamping process, and in step SA105, taking out the molded product is represented by the end of the cycle.

  The correlation coefficient is calculated by interpolating the predetermined sampling time interval at a time interval shorter than the sampling time interval, or by decimating a physical quantity related to injection molding at a time interval longer than the predetermined sampling time interval. It is also possible to do.

  FIG. 9 is a diagram for explaining quality determination based on the injection pressure at the time when the absolute value of the correlation coefficient calculated sequentially becomes maximum. In FIG. 9, when the correlation coefficient between the physical quantity related to injection molding such as the injection pressure and the molding quality data such as the minimum cushion amount is sequentially calculated, it is found that the correlation between the physical quantity and the molding quality data is strong at time t1. . Therefore, it is preferable to set the standard for determining the quality of the molded product based on the physical quantity data at time t1.

  FIG. 10 is a diagram for explaining pass / fail determination based on pressure at the time when the absolute value of the sequentially calculated correlation coefficient becomes maximum. As described with reference to FIG. 9, FIG. 10 shows that the setting is based on the physical quantity data at time t1. An upper limit value and a lower limit value for pass / fail judgment are set, and when the physical quantity detected at the time t1 in each molding cycle exceeds the upper limit value or falls below the lower limit value, it is determined as a defective product. Can do.

FIGS. 12A and 12B are diagrams for explaining an algorithm for pass / fail determination processing based on a physical quantity at a time when the absolute value of the sequentially calculated correlation coefficient becomes maximum. Hereinafter, it demonstrates according to each step. Steps SB100 to SB107 are preliminary cycles that are executed to specify the time detected in one cycle of the physical quantity to be compared with the upper limit value and the lower limit value, which are the criteria for determining the quality of the molded product. After the preliminary cycle, shift to the main cycle.
[Step SB100] N, which is the value of the cycle counter, is set to an initial value 0.
[Step SB101] The molding cycle of the injection molding machine is started.
[Step SB102] Add 1 to N and set the value to N.
[Step SB103] In a period from the start to the end of the molding cycle in one molding cycle, a physical quantity related to injection molding is detected and stored at predetermined sampling time intervals.
[Step SB104] Molding quality data in one molding cycle is detected and stored.
[Step SB105] One molding cycle is completed.
[Step SB106] It is determined whether or not the cycle counter N is greater than a predetermined value. If not, the process returns to Step SB101, and the process proceeds to the next molding cycle. If greater, the process proceeds to Step SB107.
[Step SB107] The correlation coefficient between the physical quantity related to injection molding detected and stored in step SB103 and the molding quality data detected and stored in step SB104 is compared with the physical quantity related to injection molding detected and stored in step SB103. And calculated and stored for each predetermined sampling time interval.
[Step SB108] The time at which the absolute value of the correlation coefficient sequentially calculated in Step SB107 is maximized is calculated. Let the calculated time be tx.
[Step SB109] The cycle is started.
[Step SB110] A physical quantity P (tx) related to injection molding at time tx calculated in step SB108 is detected.
[Step SB111] It is determined whether or not the physical quantity P (tx) related to injection molding is equal to or lower than the upper limit value. If it is equal to or smaller than the above, the process proceeds to Step SB112.
[Step SB112] It is determined whether or not the physical quantity P (tx) related to injection molding is equal to or greater than the lower limit value. If it is, the process proceeds to Step SB113. Otherwise, the process proceeds to Step SB114.
[Step SB113] A good product signal is output, and the process proceeds to Step SB115. The good product signal may be displayed on the display device of the input device 25 with a display device in FIG.
[Step SB114] A defective product signal is output, and the process proceeds to Step SB115. The defective product signal may be displayed on the display device of the input device 25 with a display device in FIG. Moreover, you may make it accommodate the molded article pushed down from the metal mold | die in a defective article collection box.
[Step SB115] The cycle ends.
[Step SB116] It is determined whether or not the number of times of this cycle has been completed. If the number of times of this cycle has not been reached, the process returns to step SB109 and proceeds to the next molding cycle.

  By executing the processing of the algorithm described above with the injection molding machine shown in FIG. 1, the timing within the molding cycle at which the correlation between the physical quantity related to injection molding such as the injection pressure and screw position and the molding quality becomes strong is calculated. Thus, it is possible to provide a control device for an injection molding machine having a correlation coefficient calculation function capable of specifying an optimal timing for determining pass / fail of a molded product.

FIG. 13A and FIG. 13B are diagrams for explaining an algorithm of processing for correcting the injection / holding pressure switching position based on the absolute value of the correlation coefficient calculated sequentially. Hereinafter, it demonstrates according to each step. Steps SC100 to SC107 are preliminary cycles that are executed to obtain a set position used for the injection hold pressure switching position correction process. After the preliminary cycle, shift to the main cycle.
[Step SC100] N, which is the value of the cycle counter, is set to an initial value 0.
[Step SC101] The molding cycle of the injection molding machine is started.
[Step SC102] Add 1 to N and set the value to N.
[Step SC103] During the period from the start to the end of the molding cycle in one molding cycle, the physical quantity related to injection molding is detected and stored at predetermined sampling time intervals.
[Step SC104] Molding quality data in one molding cycle is detected and stored.
[Step SC105] One molding cycle is completed.
[Step SC106] It is determined whether or not the cycle counter N is greater than a predetermined value. If not, the process returns to step SC101, and the process proceeds to the next molding cycle. If greater, the process proceeds to step SC107.
[Step SC107] The correlation coefficient between the physical quantity related to injection molding detected and stored in step SC103 and the molding quality data detected and stored in step SC104 is compared with the physical quantity related to injection molding detected and stored in step SC103. And calculated and stored for each predetermined sampling time interval.
[Step SC108] The time at which the absolute value of the correlation coefficient sequentially calculated in Step SC107 is maximized is calculated. Let the calculated time be tx.
[Step SC109] The cycle starts.
[Step SC110] The injection is started.
[Step SC111] The physical quantity P (tx) related to injection molding at the time tx calculated in Step SC108 is detected.
[Step SC112] The correction amount X of the injection / holding pressure switching position is calculated based on the physical quantity P (tx) detected in step SC111. Correction amount X = (P (tx) −β) * α where X: correction amount, α: correction coefficient, and β: reference value.
[Step SC113] It is determined whether or not the screw position is smaller than (set position + correction amount X). If smaller, the process proceeds to step SC114. If not smaller, the process proceeds to step C114. To do.
[Step SC114] Holding pressure is started.
[Step SC115] End the cycle.
[Step SC116] It is determined whether or not the number of times of this cycle has been completed. If the number of times of this cycle has not been finished, the process returns to step SC109 to proceed to the next molding cycle.

FIGS. 14A and 14B are diagrams for explaining the control of the pressure holding section by the absolute value of the correlation coefficient calculated sequentially. Hereinafter, it demonstrates according to each step. Step SD100 to step SD107 are preliminary cycles for obtaining the holding time start time and end time. After the preliminary cycle, shift to the main cycle.
[Step SD100] N, which is the value of the cycle counter, is set to an initial value 0.
[Step SD101] The molding cycle of the injection molding machine is started.
[Step SD102] Add 1 to N and set the value to N.
[Step SD103] In a period from the start to the end of the molding cycle in one molding cycle, a physical quantity related to injection molding is detected and stored at predetermined sampling time intervals.
[Step SD104] Detect and store molding quality data in one molding cycle.
[Step SD105] One molding cycle is completed.
[Step SD106] It is determined whether or not the cycle counter N is greater than a predetermined value. If not, the process returns to step SD101, and the process proceeds to the next molding cycle. If greater, the process proceeds to step SD107.
[Step SD107] The correlation coefficient between the physical quantity related to injection molding detected and stored in step SD103 and the molding quality data detected and stored in step SD104 is compared with the physical quantity related to injection molding detected and stored in step SD103. And calculated and stored for each predetermined sampling time interval.
[Step SD108] Time at which the absolute value of the correlation coefficient is equal to or greater than the first predetermined value is calculated.
[Step SD109] After the time tx1, calculate the time when the absolute value of the correlation coefficient is equal to or less than the second predetermined value.
[Step SD110] Start cycle.
[Step SD111] Injection starts.
[Step SD112] It is determined whether or not the current time in one cycle is greater than the time tx1, and if it is greater, the process proceeds to step SD113. To do.
[Step SD113] Pressure holding starts.
[Step SD114] It is determined whether or not the current time in one cycle is greater than the time tx2. If the current time is larger, the process proceeds to Step SD115. If not, the process proceeds to Step SD115.
[Step SD115] The pressure holding is finished.
[Step SD116] End the cycle.
[Step SD117] It is determined whether or not the number of times of this cycle has been completed. If the number of times of this cycle has not been reached, the process returns to step SD110 to proceed to the next molding cycle.

By executing the above-described algorithm processing in the injection molding machine shown in FIG. 1, the physical quantity related to injection molding such as injection pressure and screw position is controlled and stabilized at the timing when the correlation with the molding quality becomes strong. By doing so, it is possible to provide a control device for an injection molding machine having a correlation coefficient calculation function capable of improving the molding quality itself.
Although the time at which the absolute value of the correlation coefficient is maximized is calculated in step SB108 and step SC108 described above, for example, a peak value may be selected as the value at which the absolute value of the correlation coefficient is maximized. .

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Nozzle 3 Screw 4 Hopper 5 Pressure sensor 6, 7 Transmission mechanism 8 Conversion mechanism 10 Control apparatus 11 Servo amplifier 12 Servo amplifier 13 ROM
14 RAM
15 Servo CPU
16 A / D converter 17 PMCCPU
18 ROM
19 RAM
20 CNCCPU
21 ROM
22 RAM
23 Molding data storage RAM
24 Display Circuit 25 Input Device with Display Device 26 Bus Penc1 Position / Speed Detector Penc2 Position / Speed Detector M1 Injection Servo Motor M2 Screw Rotation Servo Motor

Claims (7)

Physical quantity detection means for detecting physical quantities related to injection molding at predetermined sampling time intervals, physical quantity storage means for storing the physical quantities detected by the physical quantity detection means as time-series data of the predetermined sampling time intervals over a plurality of cycles, and molding quality data A molding quality data detecting means for detecting the molding quality data storage means for storing the molding quality data detected by the molding quality data detecting means over a plurality of cycles, and a control device for an injection molding machine,
Of the time series data of the physical quantity stored by the physical quantity storage means, the correlation coefficient between the physical quantity at the same time between shots and the molding quality data between shots stored by the molding quality data storage means is the same. Correlation coefficient calculation means for calculating as a correlation coefficient at time,
A control apparatus for an injection molding machine, wherein the correlation coefficient is sequentially calculated by the correlation coefficient calculation means at each predetermined sampling time interval. A time at which the absolute value of the correlation coefficient sequentially calculated by the correlation coefficient calculation means is maximized is obtained, and quality determination of the molded product is performed based on a physical quantity related to injection molding at the obtained time. The control apparatus for an injection molding machine according to claim 1 . A time at which the absolute value of the correlation coefficient sequentially calculated by the correlation coefficient calculating means is maximized is obtained, and an injection holding pressure switching position or an injection speed switching position is determined based on a physical quantity related to injection molding at the obtained time. The control apparatus for an injection molding machine according to claim 1, wherein correction is performed. The absolute value of the correlation coefficient sequentially calculated by the correlation coefficient calculation means is compared with a predetermined value to obtain a section where the absolute value of the correlation coefficient calculated sequentially is equal to or greater than the predetermined value, and injection molding is performed in the section. The control apparatus for an injection molding machine according to claim 1, wherein feedback control of the physical quantity related to is performed.   The physical quantities related to the injection molding are: injection pressure, screw position, screw speed, in-mold pressure, ejector position, ejector thrust, mold platen position, mold platen thrust, mold parting surface interval, mold clamping force, mold temperature. It is any one of them, The control apparatus of the injection molding machine as described in any one of Claims 1-4 characterized by the above-mentioned.   The molding quality data is data capable of directly evaluating the molding quality detected from the molded product itself, or data which can be detected from a physical quantity during the molding process and indirectly evaluate the quality of the molded product. The control apparatus for an injection molding machine according to any one of claims 1 to 4.   7. The control apparatus for an injection molding machine according to claim 1, wherein the sequentially calculated correlation coefficient is displayed on a screen as a waveform.

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