JP3556357B2 - Product quality judgment device in injection molding machine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a method for determining the quality of a product in an injection molding machine.apparatusAbout.
[0002]
[Prior art]
As a method for automatically determining the quality of a product in an injection molding operation, a minimum cushion amount, an injection time, a peak injection pressure, an injection / holding pressure switching position, and the like are detected and compared with an allowable range serving as a determination criterion. Have already been proposed by the present applicants as JP-A-6-170907. These methods mainly determine the quality of the product based on the injection state, and do not use the measured state of the molten resin as the quality determination target.
[0003]
As a method for determining the quality of the molten resin, a method of determining the quality of a product by the present applicant is proposed in Japanese Patent Application Laid-Open No. Hei 6-297532. This method sets a discrimination target section based on the screw position or the elapsed time after the start of the weighing process, and sets a back pressure between the upper limit value and the lower limit value of the back pressure set corresponding to the discrimination target section at that time. It is determined whether or not the melted state of the resin is appropriate based on whether or not the detection value is included, and this is used as a result of the quality determination of the product.
[0004]
According to this configuration, there is an advantage that the determination target section can be divided into a plurality of sections and the quality of the product can be determined by checking the state of the molten resin at a key point in the weighing process. Since the section is set by the screw position or the elapsed time after the start of the weighing process, if the weighing completion position or the required weighing time varies, the quality of the product is determined based on the back pressure at the time of weighing completion. There is also the possibility of receiving support.
[0005]
In addition, when the suck-back operation is performed after the measurement or when the cooling time is set to be longer, the injection operation does not always start immediately after the measurement is completed, and the resin is further melted after the measurement is completed. In some cases, it is not always possible to make an accurate pass / fail judgment by simply checking the state of the molten resin by detecting the back pressure in the weighing process or the like.
[0006]
[Problems to be solved by the invention]
The object of the present invention is to determine the quality of the product by comprehensively determining the state of the measured molten resin immediately before the start of injection, regardless of the dispersion of the measurement completion position and the measurement required time, If necessary, in an injection molding machine that can check the melting state of the resin and make an appropriate quality judgment at any timing suitable for product quality determination during the period from the completion of measurement to the start of the next injection. Product quality judgmentapparatusIs to provide.
[0007]
[Means for Solving the Problems]
The present invention relates to an injection molding machine that holds a screw in a predetermined position after completion of measurement.Product quality judgment device in, Detects resin pressure just before the start of injectionMeans toCompares the detected resin pressure with a preset allowable pressure rangeMeans to do and beforeOutputs a fault signal if the detected resin pressure is out of the allowable pressure rangeMeans are provided to determine the quality of the product.
[0008]
Further, there is provided a device for judging the quality of a product in an injection molding machine for holding a screw at a predetermined position after completion of weighing., Resin pressure detection timing can be set arbitrarily within the period from the completion of measurement to the start of the next injectionMeans to, Detects resin pressure at the set timingMeans toCompares the detected resin pressure with a preset allowable pressure rangeMeans to do and beforeMeans for outputting a failure signal if the detected resin pressure is out of the allowable pressure rangeTo determine the quality of the product.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 shows the product quality judgment of the present invention.Equipped with equipmentFIG. 1 is a block diagram showing a main part of an injection molding machine according to one embodiment, wherein reference numeral 1 denotes a cylinder of the injection molding machine, and reference numeral 2 denotes a screw. The screw 2 is driven in the injection axis direction by an injection servomotor M1 via a drive converter 5 for converting the shaft rotation of the drive source into a linear motion in the injection axis direction. The metering rotation is performed by the rotation motor M2. A pressure detector 4 is provided at the base of the screw 2, and the resin pressure acting in the axial direction of the screw 2, that is, the resin pressure (back pressure) in the injection pressure holding step and the resin pressure (back pressure) in the metering and kneading step, is A. It is detected via the / D converter 16. Note that it is also possible to directly detect the resin pressure by a pressure sensor attached to the tip (measuring unit) inside the cylinder 1 and input the resin pressure to the A / D converter 16. The injection servomotor M1 is provided with a pulse coder P1 for detecting the position and the movement speed of the screw 2, and the screw rotation motor M2 is provided with a speed detector P2 for detecting the rotation speed of the screw 2. Have been.
[0010]
The control device 10 also serving as a product quality judgment device of the injection molding machine includes a CNC CPU 25 which is a microprocessor for numerical control, a CPU 18 for a PMC which is a microprocessor for a programmable machine controller, and a servo CPU 20 which is a microprocessor for servo control. And a pressure monitor CPU 17 for sampling the injection holding pressure and the back pressure. Information can be transmitted between the microprocessors by selecting mutual input / output via the bus 22. ing.
[0011]
The ROM 18 storing a sequence program for controlling the sequence operation of the injection molding machine, a control program for determining the quality of the product, and the like, and a RAM 14 used for temporary storage of operation data are connected to the PMC CPU 18. On the other hand, the CNC CPU 25 is connected to a ROM 27 storing a program for controlling the entire injection molding machine and the like, and a RAM 28 used for temporarily storing calculation data.
[0012]
Each of the servo CPU 20 and the pressure monitoring CPU 17 includes 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 pressure data sampling processing. A RAM 12 used for temporary storage of data is connected. Further, the servo CPU 15 is connected to a servo amplifier 15 for driving servomotors of respective axes for mold clamping, ejector (not shown), injection, screw rotation, etc. based on a command from the CPU 20. Each of the outputs from the pulse coder P1 provided for the injection servomotor M1 and the pulse coder P2 provided for the screw rotation motor M2 is fed back to the servo CPU 20, and the screw 2 calculated by the servo CPU 20 based on the feedback pulse from the pulse coder P1. And the rotational speed of the screw 2 detected by the speed detector P2 are stored in the current position storage register and the current speed storage register of the memory 19, respectively.
[0013]
The non-volatile memory 24 is a memory for storing molding data (injection holding pressure conditions, weighing and kneading conditions, etc.) relating to the injection molding operation, and various setting values, parameters, macro variables, and setting data for pass / fail determination. It is.
[0014]
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.
[0015]
A manual data input device 29 with a display is connected to the bus 22 via a CRT display circuit 26 so that a monitor display screen and a function menu can be selected and various data input operations can be performed. And various function keys.
[0016]
Then, the CNC CPU 25 distributes pulses to the servomotors of the respective axes based on the control program in the ROM 27, and the servo CPU 20 determines the movement commands and the pulse coder P1, the speed detector P2, etc. Based on the position feedback signal and the speed feedback signal detected by the detector, servo control such as position loop control, speed loop control, and current loop control is performed in the same manner as in the related art, and so-called digital servo processing is executed.
[0017]
Next, the product quality judgment to which the present invention is appliedapparatusA first embodiment will be described. In this embodiment, the quality of a product is determined by detecting the resin pressure immediately before the start of injection and comparing the resin pressure with a preset allowable pressure range. Therefore, in order to carry out this product quality judgment method, it is necessary to obtain in advance the allowable pressure range to be compared with the resin pressure (back pressure) immediately before the start of injection, and set the allowable pressure range in the nonvolatile memory 24.
[0018]
Therefore, the operator causes the injection molding work to be continuously performed at the time of completion of the condition setting, and during this time, causes the pressure monitoring CPU 17 to perform a back pressure sampling process to determine the resin pressure data immediately before the start of the injection. Measure several times. At this time, if a number line indicating the resin pressure is displayed as a graph on the screen of the manual data input device 29 with a display, and the resin pressure value for each molding cycle is plotted on the graph, a good straight line can be obtained. , The operator can easily grasp the variation in the resin pressure data immediately before the start of injection, and the operator can determine the lower limit value A and the upper limit value B of the allowable pressure range with reference to the variation.
[0019]
In some cases, the lower limit value A and the upper limit value B of the allowable pressure range are set in accordance with the lower limit and the upper limit of the measured resin pressure variation. The value of α (α> 0)] and the upper limit of resin pressure variation + β (β> 0) may be set in the nonvolatile memory 24 as the lower limit A and the upper limit B. The back pressure is sampled by the pressure monitoring CPU 17 immediately before the start of injection, that is, when the mold closing completion signal is output from the CNC CPU 25.
[0020]
Of course, a predetermined number of continuous operations are automatically executed, and during this time, the minimum value and the maximum value of the sampling value are detected by the processing of the CPU 25 for CNC, and these are automatically determined as the lower limit value A and the upper limit value B. The lower limit A and the upper limit B may be set in the memory 24, and the lower limit A and the upper limit B may be calculated based on the minimum and maximum values of the sampling value and the preset values of α and β. It is also possible to make these settings and automatically set them in the nonvolatile memory 24. In addition, another statistical calculation process may be performed using all the sampling values, and the lower limit value A and the upper limit value B may be determined.
[0021]
FIG. 2 is a flowchart showing an outline of a process for judging the quality of a product based on the allowable pressure range (lower limit value A, upper limit value B) thus obtained. This process is performed by an injection molding machine. Is integrated with a sequence program for controlling the above sequence operation and stored in the ROM 13.
[0022]
The sequence control by the PMC CPU 18 is exactly the same as the conventional one, and one molding cycle includes a mold closing process (including mold clamping) → an injection process (including pressure holding) → a measuring process (including cooling) → a mold opening. In the case of semi-automatic operation, this series of operations is performed only once, and in the case of automatic operation, this series of operations is repeatedly executed. Because the injection process is performed before the weighing process, before starting the semi-automatic operation or the automatic operation, perform the weighing operation by manual operation in advance, and screw the screw to the set weighing completion position or behind. It is necessary to retract the molten resin required for one injection operation in the cylinder 1 by retracting the cylinder 2. When the automatic operation is started, the semi-automatic operation is started once, and the automatic operation switch is operated within this one molding cycle, whereby the above-described molding cycle is repeatedly executed.
[0023]
After completing the weighing by manual operation, confirm that the movable side mold is retracted more than the mold opening completion position and that the ejector is retracted more than the retracted position, and operate the semi-automatic operation switch on the operation panel. A mold closing command is output to the CNC CPU 25, and the operation of one molding cycle from the mold closing step to the mold opening step is started. That is, the CNC CPU 25 that has received the mold closing command starts pulse distribution to the mold clamping servomotor based on the control program in the ROM 27 and the setting conditions in the nonvolatile memory 24, and performs the mold closing process in the same manner as in the related art. Meanwhile, the PMC CPU 18 repeatedly executes the determination processing of steps S1 to S4, and enters a standby state waiting for a mold closing completion signal from the CNC CPU 25. When the CNC CPU 25 completes the mold closing process and outputs a mold closing completion signal, the PMC CPU 18 detects this in the determination process of step S2, and issues a start command for the next process, that is, an injection start command. (Step S11) is output to the CPU 25 for CNC. The processing of steps S7 to S10 following step S2 is the gist of the present embodiment. Here, the description will be given later and the overall sequence operation will be described.
[0024]
The processing of each step such as injection, weighing, mold opening and the like is exactly the same as the processing of the mold closing step described above, and the drive control of each axis in each step is executed by the CNC CPU 25 according to a step start command from the CPU 18 for PMC. Then, the CNC CPU 25 that has completed the processing of the process sequentially outputs an injection completion signal, a measurement completion signal, and a mold opening completion signal, and the PMC CPU 18 that has received this outputs the next signal based on the determination results of steps S1 to S4. , A series of molding cycles including the steps of mold closing, injection, weighing, and mold opening are executed by sequentially issuing a weighing start command (step S12) and a mold opening start command (step S13). It is done.
[0025]
If the automatic operation switch is not operated within the molding cycle after the start of the semi-automatic operation, since the reset state of the continuation flag in step S5 is maintained as it is, the mold opening completion signal from the CNC CPU 25 (one molding cycle) Is completed), the result of the determination in step S5, which is performed by detecting the completion of the last step, is false, and the molding cycle ends only once. If the automatic operation switch is operated during the molding cycle of the semi-automatic operation (a period from the output of the mold closing start command to the detection of the mold opening completion signal), the continuation flag of step S5 is set, and the sequence as described above is performed. , The steps of injection, measurement, and mold opening are repeatedly executed.
[0026]
In the weighing process, the screw rotation motor M2 is driven while the driving force of the injection servomotor M1 is maintained at a value corresponding to the set back pressure by the processing of the CNC CPU 25 to perform the weighing operation. The screw 2 retreats in accordance with an increase in the amount of the molten resin to be measured. When the screw 2 reaches the set measurement completion position, the screw rotation motor M2 is stopped to stop the measurement, and the rotation position of the injection servomotor M1 is stopped. Is held at the current position, and the screw 2 is held at the fixed position. As a result, the resin pressure in the cylinder 1 is maintained at the set back pressure during the measurement process. However, when the measurement is completed, the screw 2 is held at the fixed position, the capacity of the cylinder 1 is fixed, and Since the melting of the resin does not take place, the resin pressure may change due to the decomposition of the retained molten resin, the generation of gas, or the resin leakage. Of course, even if the molten resin is decomposed, gas is generated, or the resin leaks during the period from the completion of the measurement to immediately before the injection, there is no problem as long as a normal product is molded using the molten resin. Needless to say, the lower limit value A and the upper limit value B are values determined on the basis of the resin pressure of the molten resin immediately before injection during non-defective molding, and have a direct relationship with the set back pressure in the measuring process. Absent. Immediately after the completion of the measurement, a suck-back operation of retracting the screw 2 from the measurement completion position by a predetermined amount and holding the screw 2 at that position may be performed. This is also a type of holding the screw 2 at a fixed position.
[0027]
The outline of the sequence control by the PMC CPU 18 has been described above, but these points are exactly the same as those of the conventional one.
[0028]
This embodiment differs from the conventional one in the pass / fail judgment processing executed in steps S7 to S10 as described above. As is clear from FIG. 2, the pass / fail judgment processing is incorporated in the sequence at a timing immediately before the injection start command is output.
[0029]
The PMC CPU 18 that has detected the completion of the mold closing process, which is the preceding process of the injection process, in the determination process of step S2 via the pressure monitor CPU 17 and the pressure detector 4, the current value P of the resin pressure, that is, immediately before the start of injection. Immediately reads the value of the resin pressure P (step S7), and determines whether the current value P is between the lower limit value A and the upper limit value B set in the nonvolatile memory 24 in advance, that is, within the allowable pressure range. Is determined (step S8). If the current value P is between the lower limit value A and the upper limit value B, a product molded (taken out) in a molding cycle including an injection step performed using the molten resin is regarded as a good product. As a result, a non-defective signal is output to the product sorting apparatus or the non-defective defective shot number counter (step S10). If the current value P is smaller than the lower limit value A or larger than the upper limit value B, a product molded (taken out) in a molding cycle including an injection step performed using the molten resin is defective. And outputs a defective signal to the product sorting device, the non-defective defective shot number counter, or the like (step S9).
[0030]
In this embodiment, since the molding cycle including the resin pressure P and the molding cycle including the injection step performed using the resin always match, the signal output at step S10 or step S9 is received. The destination of the product sorting device may be changed immediately. That is, the product released by the mold opening operation in the same molding cycle is always molded in the injection process performed using the molten resin whose resin pressure is read in the process of step S7 performed in the molding cycle. (However, the measurement of the resin itself is performed one molding cycle before).
[0031]
As described above, the processing related to the sequence control after the output of the non-defective signal or the defective signal (step S11 and subsequent steps) is completely the same as the conventional one, and therefore will not be described here.
[0032]
According to this embodiment, even if the molten state of the resin changes after the completion of the measurement by performing a suck-back operation or setting a longer cooling time, the final molten state of the resin is changed. By detecting the resin pressure as one of the factors shown at the timing immediately before the start of injection, and comparing the resin pressure with the allowable pressure range (lower limit value A, upper limit value B) set based on the resin pressure at the same timing at the time of non-defective molding. The quality of the product can be determined by comprehensively determining the state of the molten resin, including the change in the state of the resin after the completion of the measurement. Although the suck-back sequence is not disclosed in FIG. 2, this operation is performed by stopping the rotation of the screw 2 and retreating the screw 2 by a predetermined amount at the same time as the completion of the measurement, as described above. .
[0033]
Next, the product quality judgment to which the present invention is appliedapparatusAnother embodiment will be described. In this embodiment, the resin pressure detection timing is arbitrarily set within the period from the completion of the measurement to the start of the next injection, the resin pressure is detected at the same timing in each molding cycle, and the resin pressure is set in advance with this resin pressure. The quality of the product is determined by comparing the allowable pressure range.
[0034]
Therefore, in this embodiment, there is no particular limitation on the timing of detecting the resin pressure for quality determination, and the timing of detecting the resin pressure can be arbitrarily set within a period from the completion of the measurement to the start of the next injection. However, the operator must determine the detection timing in advance.
[0035]
The timing at which the state of the molten resin that has the greatest effect on the quality of the product is considered to vary depending on the temperature conditions of the cylinder 1, the type of resin, and the like. Various experiments may be performed according to the type and the like, and the timing at which the state of the molten resin that has the greatest influence on the quality of the product is detected may be grasped.
[0036]
The method of obtaining the allowable pressure range is basically the same as that of the above-described embodiment. However, in this embodiment, the resin pressure detection timing can be set arbitrarily, so that the allowable pressure range is obtained. In the back pressure sampling process, a detection timing predetermined by the operator is set in the control device 10, and the sampling process is performed in accordance with this timing. The resin pressure data is measured several times and displayed as a graph, and the lower and upper limits A and B of the allowable pressure range are determined based on the lower and upper limits of the variation and the allowable ranges of error α and β. This is the same as in the previous embodiment in that it is determined, and that this can be automatically performed by the processing on the control device 10 side.
[0037]
Note that the back pressure sampling by the pressure monitoring CPU 17 is performed by activating the timer by the PMC CPU 18 at the time when the metering completion signal from the CNC CPU 25 is detected, and executed at the time when the timer measures the set time Tx. I do. Needless to say, this Tx is the above-described resin pressure detection timing, and its value is set by the elapsed time when the measurement completion time is zero.
[0038]
FIG. 3 and FIG. 4 are flowcharts showing an outline of a process for determining the quality of a product based on the allowable pressure range (lower limit value A, upper limit value B) thus obtained. It is integrated with a sequence program for controlling the sequence operation of the injection molding machine and is incorporated in the ROM 13.
[0039]
The sequence control by the PMC CPU 18 is exactly the same as that of the conventional one and that of the above-described embodiment with respect to the part relating to the direct molding operation. That is, the processing of steps T1 to T4 in FIG. 3 is the same as the processing of steps S1 to S4 in FIG. 2, and the processing of steps T7, T9, T10, T11, and T15 in FIG. Is exactly the same as each processing of step S5, step S6, step S11, step S12, and step S13 in FIG. 2, and includes a mold closing step (including mold clamping) → an injection step (including holding pressure) → a weighing step ( There is no difference in the sequence operation itself of one molding cycle consisting of each step of cooling (including cooling) → mold opening step (including eject). The start-up of the semi-automatic operation and the switching operation to the automatic operation are the same as those of the conventional one and the above-described embodiment.
[0040]
Next, the pass / fail judgment processing of this embodiment will be described in detail.
[0041]
First, the initial values of the measurement standby flag F2 and the signal output state storage flag F4 (both details will be described later) are 0, and when the input of a molding start command by operating the semi-automatic operation switch is detected (this is the start of the molding cycle). First, the PMC CPU 18 sets the process storage flag F1 to 0 (step T8), outputs a mold closing start command to the CNC CPU 25, and starts the process of the mold closing process by the CNC CPU 25. (Step T9), the loop processing of Steps T1 to T6 is started again, and a standby state is waited for a mold closing completion signal from the CPU 25 for CNC.
[0042]
The processing when the mold opening completion signal is input from the CNC CPU 25 during the automatic operation (the processing when the determination result in step T1 is true) is the same as described above. Switching to automatic operation is performed by operating an automatic operation switch during semi-automatic operation. In addition, as can be understood by referring to step T4 and step T13, the value of the process storage flag F1 is 0 in the section from the start of mold closing to the completion of weighing, and the section from the completion of weighing to the start of mold closing in the next molding cycle. Is 1.
[0043]
When the mold closing process by the CNC CPU 25 is completed and a mold closing completion signal is input, the PMC CPU 18 detects this in the determination processing of step T2 and outputs an injection start command to the CNC CPU 25. (Step T10), the process of the injection process including the holding pressure is executed by the CNC CPU 25, and the PMC CPU 18 itself starts the loop process of Steps T1 to T6 again. Needless to say, the resin injected by this injection operation is the molten resin measured by the previous molding cycle or the manual operation at the start of the semi-automatic operation.
[0044]
Next, when an injection completion signal is input from the CNC CPU 25, the PMC CPU 18 detects this in the determination processing of step T3, outputs a weighing start command to the CNC CPU 25 (step T11), and executes the weighing process. Is executed by the CNC CPU 25. Similarly to the above, the PMC CPU 18 itself starts the loop processing of Steps T1 to T6 again.
[0045]
When the process of the weighing process by the CNC CPU 25 is completed and a weighing completion signal is input, the PMC CPU 18 detects this in the determination process of step T4, resets the timer T, and sets the weighing completion time to zero. The counting of the elapsed time is started (step T12). Needless to say, this measurement start timing is the same as that at the time of the sampling process performed for obtaining the allowable pressure range.
[0046]
Next, the PMC CPU 18 sets 1 to the process storage flag F1 and the measurement standby flag F2 (step T13, step T14), outputs a mold opening start start command to the CNC CPU 25 (step T15), and executes the mold opening process. The process is executed by the CNC CPU 25, and the PMC CPU 18 itself starts the loop process of steps T1 to T6 again. As described above, the value of the process storage flag F1 is 1 in the section from the completion of the measurement to the start of closing the mold in the next molding cycle. In addition, as can be seen by referring to steps T16, T17 and T21, the value of the measurement standby flag F2 is determined after the completion of the measurement until the time measured by the timer T reaches the set value Tx and the resin pressure is detected. It is 1 in the section, and 0 in the section from the detection of the resin pressure until the next measurement is completed.
[0047]
The PMC CPU 18 that repeats the loop processing of steps T1 to T6 detects that the value of the measurement standby flag F2 has been switched from 0 to 1 by the determination processing of step T5, and then proceeds to the next processing and proceeds to the timer T It is determined whether or not the measurement time has reached the set value Tx (step T16). If the time measured by the timer T has not reached the set value Tx, the timing for detecting the resin pressure has not reached, and the PMC CPU 18 returns to the process of step T1 again, and thereafter, based on the value of the measurement standby flag F2. , The loop processing of steps T1 to T5 and step T16 is repeatedly executed.
[0048]
Since this loop processing includes the discrimination processing of steps T1 to T4, that is, detection of the mold opening completion signal, detection of the mold closing completion signal, and the like, it does not matter whether the measurement time of the timer T reaches the set value Tx. As long as the processing on the CNC CPU 25 side corresponding to the mold opening start command (see step T15) output in the molding cycle is completed and only the mold opening completion signal is input from the CNC CPU 25, the PMC CPU 18 itself It is possible to start the sequence control of the next molding cycle including the mold closing step. It will be necessary to keep this in mind in understanding the following description.
[0049]
As described above, in this embodiment, the detection timing Tx of the resin pressure can be arbitrarily set within a period from the completion of the measurement to the start of the next injection. Therefore, depending on the set value of Tx. There are two cases: the determination result of step T16 becomes true in the same molding cycle in which the mold opening start command is output, and the determination result of step T16 becomes true during the execution of the next molding cycle.
[0050]
More specifically, when the detection timing Tx is set to be short, the determination result of step T16 is true during the execution of the mold opening process (including the eject) in the same molding cycle as when the mold opening start command is output. When the detection timing Tx is set to be longer, the determination result of step T16 becomes true in the execution process of the mold closing step (including the mold clamping) in the next molding cycle. That is, the resin pressure is measured. If the detection timing Tx is set to be extremely long, the determination result of step T16 may become true for the first time in the injection step or the subsequent steps in the next molding cycle. The setting range of should be limited to the period from the completion of weighing to the start of the next injection until it gets tired, all setting actions that straddle after the next injection step are erroneous, and such setting actions are performed Not be.
[0051]
In other words, in other words, the measurement time of the timer T has reached Tx in the mold closing process (the period in which the process storage flag F1 is 0, but does not include the injection process and the measuring process as described above). If any, it means that the resin pressure of the molten resin measured in the immediately preceding molding cycle was measured after entering the mold closing step of the molding cycle. In this case, the injection was performed in the injection step of the molding cycle. The molten resin to be measured is the same as the molten resin whose resin pressure is measured in the molding cycle. Therefore, in such a case, the non-defective signal or the defective signal obtained from the measurement result is output before the completion of the molding cycle, and the signal is output at the stage before the execution of the mold opening step (strictly, the eject operation) of the molding cycle. The destination of the product sorting device must be determined. In the same molding cycle, the mold closing step is positioned earlier in the time series than the mold opening step (strictly, eject operation), so that the measurement time of the timer T reaches Tx while the step storage flag F1 is 0. In this case, it is possible to output a non-defective signal or a defective signal immediately after the measurement of the resin pressure and the quality determination.
[0052]
On the other hand, if the measurement time of the timer T has reached Tx in the mold opening process (that is, a period in which the process storage flag F1 is 1), the resin pressure of the molten resin measured in the molding cycle is changed to the molding cycle. In this case, the molten resin injected in the injection step of the molding cycle is different from the molten resin whose resin pressure was measured in the molding cycle. More specifically, the molten resin injected in the injection step of the molding cycle is the molten resin measured in the immediately preceding molding cycle, and the molten resin whose resin pressure was measured in the molding cycle is It is a molten resin injected in the injection step of the next molding cycle.
[0053]
Therefore, in such a case, it is not possible to immediately output a non-defective signal or a defective signal obtained based on the measurement result to determine a distribution destination of the product distribution device. In this case, it is necessary to wait for completion of the eject operation, and then output a non-defective signal or a defective signal obtained based on the measurement result of the molding cycle to determine a distribution destination of the product distribution device. Since the eject operation is located in the latter half of the mold opening process on the time series in the same molding cycle, if the destination of the product sorting device is immediately changed according to the determination result obtained by measuring the resin pressure in the mold opening process, This is because there is a possibility that a molded product molded in the injection step of the molding cycle, that is, a molded product measured and measured for the resin pressure in the immediately preceding molding cycle may be distributed by this distribution operation. .
[0054]
If the measurement time of the timer T reaches the set value Tx while repeatedly executing the loop processing of Steps T1 to T5 and Step T16, the PMC CPU 18 detects this in the determination processing of Step T16, and the pressure monitoring CPU 17 The current value P of the resin pressure, that is, the value of the resin pressure P at the lapse of the time Tx after the completion of the metering, is immediately read via the pressure detector 4 (step T17), and the current value P is set in the nonvolatile memory 24 in advance. It is determined whether or not it is between the lower limit value A and the upper limit value B, that is, whether or not it is within the allowable pressure range (step T18).
[0055]
If the current value P is between the lower limit value A and the upper limit value B, the product molded in the molding cycle including the injection step performed using the molten resin is regarded as good and determined. The result storage flag F3 is set to 0 (step T19). If the current value P is smaller than the lower limit value A or larger than the upper limit value B, an injection step performed using this molten resin is included. The product molded in the molding cycle is regarded as defective, and the discrimination result storage flag F3 is set to 1 (step T20). Needless to say, 0 in the flag F3 is a value indicating a good product, and 1 is a value indicating a defect.
[0056]
Next, the PMC CPU 18 sets the measurement standby flag F2 to 0 and stores the completion of the measurement of the resin pressure (step T21), and sets the signal output state storage flag F4 to 1 to output the pass / fail signal. The standby state is stored (step T22).
[0057]
For the reason described above, in this embodiment, after the discrimination processing is completed, the output of the non-defective signal or the defective signal is temporarily suspended, and the measurement of the resin pressure is performed in the mold closing process (the period when the process storage flag F1 is 0). Only when performed, the non-defective signal or the defective signal is immediately output in the next processing cycle in the PMC CPU 18, and the resin pressure is measured in the mold opening process (the period when the process storage flag F1 is 1). In such a case, a good signal or a defective signal is output at the start of the next molding cycle.
[0058]
As a result of setting the flags F2 and F4 to 0 and 1 in the processing of the above-described steps T21 and T22, in the next processing cycle, after executing the determination processing of steps T1 to T6, the PMC CPU 18 sets the process storage flag. It is determined whether or not F1 is set, that is, whether the measurement of the resin pressure is performed in the mold closing process or the mold opening process (step T23).
[0059]
If the process storage flag F1 is not set and the measurement of the resin pressure is performed in the mold closing process, the PMC CPU 18 determines whether the value of the determination result storage flag F3 is 0 or 1. It is determined (step T24) that if the value of the determination result storage flag F3 is 0, a molding cycle including an injection step performed using the molten resin, that is, a product molded in the molding cycle is a non-defective product. It is considered that there is, and a good signal is output to a product sorting device or a good / defective shot count counter (step T25), and if the value of the discrimination result storage flag F3 is 1, molding is performed in the molding cycle. The product is regarded as a defective product, and a defective signal is output to a product sorting device, a non-defective defective shot number counter, or the like (step T26).
[0060]
In other words, when the resin pressure is measured in the mold closing process (generally, when the set value of Tx is long), a non-defective signal or a defective signal is immediately output in the next processing cycle of the PMC CPU 18 after the pressure measurement is performed. It is done.
[0061]
Then, the PMC CPU 18 that has output the non-defective signal or the defective signal resets the signal output state storage flag F4 to 0 (step T27), starts the loop processing of steps T1 to T6 again, and Upon receiving the mold closing completion signal, the injection completion signal, and the weighing completion signal, the sequence control as described above is performed, and the processing of one molding cycle is completed. Since at least each step of injection and measurement is performed from the output of the pass / fail determination signal to the ejection of the product molded in the molding cycle, the operation allowance time of the product sorting device is sufficiently ensured. The molten resin injected in this molding cycle is a resin that has been measured in the immediately preceding molding cycle, and only the resin pressure has been measured in the molding cycle.
[0062]
On the other hand, when the process storage flag F1 is set and the measurement of the resin pressure is performed in the process of opening the mold, the above-described determination result of step T23 becomes true. Accordingly, in such a case, until the process storage flag F1 is set to 0 in the process of step T8, in short, the mold opening operation currently being performed is completed and the mold closing process in the next molding cycle starts. Until the process is completed, the processes of steps T24 to T27 are suspended, and until the mold closing process in the next molding cycle is started, the PMC CPU 18 performs the determination processes of steps T1 to T6 and step T23. It will be executed repeatedly.
[0063]
Then, when the mold opening process is completed and the mold opening completion signal is input from the CNC CPU 25, the PMC CPU 18 detects this in the discrimination processing of step T1 and executes the discrimination processing of step T7 (automatic operation). Since the continuation flag is set, the determination result in step T7 becomes true), the process storage flag F1 is set to 0 (step T8), and a mold closing start command is output to the PMC CPU 25 to process the mold closing process. Is started (step T9), and the value of the measurement standby flag F2 is determined (step T5). Since the measurement standby flag F2 is reset to 0 (see step T21) and the value of the signal output standby flag F4 is set to 1 (see step T22) at this time in the state of the pass / fail determination signal output standby state, The result of the determination in step T5 is false, and the result of the determination in step T6 following this is true. Further, since the value of the process storage flag F1 has been reset to 0 with the execution of the process of Step T8, the determination result of Step T23 following Step T6 is false, and the same as in Step T24 to Step T27. Processing will be performed.
[0064]
That is, when the resin pressure of the molten resin is measured during the execution of the mold opening process (generally, when the set value of Tx is short), the mold opening of the molding cycle (the molding cycle in which the resin pressure was measured) is performed. Completion, or more precisely, after waiting for the start of mold closing in the next molding cycle, a non-defective signal or a defective signal is output.
[0065]
Then, the PMC CPU 18 that has set the signal output state storage flag F4 to 0 starts the loop processing of steps T1 to T6 again, and transmits the mold closing completion signal, the injection completion signal, and the weighing completion signal from the PMC CPU 25. Then, the sequence control as described above is performed, and the sequence processing of one molding cycle is completed. Also in this case, since the mold closing, injection, and metering processes are performed from the output of the pass / fail determination signal until the corresponding product is ejected, the operation allowance time of the product sorting device is sufficiently ensured. In the case where the resin pressure of the molten resin is measured during the execution of the mold opening step of the N-th molding cycle, the molten resin that is injection-molded and taken out as a product in the N-th molding cycle is: The resin is measured in the (N-1) th molding cycle, and the resin pressure is measured in the same (N-1) th molding cycle. The pass / fail judgment result used for sorting the products is obtained during the execution of the mold opening process of the (N-1) th molding cycle, and this result is carried over to the start of the Nth mold closing operation. Then, the distribution destination of the product distribution device or the like is changed only at the start of the Nth mold closing operation.
[0066]
Hereinafter, while the continuous molding operation is performed, the same processing operation as described above is repeatedly performed for each molding cycle, and the quality of the product molded and taken out in each molding cycle is determined, and the product actually taken out in the molding cycle is determined. The product sorting device or the like is driven according to the quality of the product.
[0067]
According to this embodiment, the detection timing of the resin pressure can be arbitrarily set within a period from the completion of the measurement to the start of the next injection. Accordingly, as long as the timing at which the state of the molten resin that has the greatest influence on the quality of the product is detected can be specified by the temperature condition of the cylinder 1, the type of the resin, and the like, the timing can be set as Tx to achieve extremely high accuracy. , It is possible to execute the pass / fail judgment with high quality.
[0068]
Further, if the elapsed time after the completion of the weighing corresponding to the completion of the suckback is experimentally obtained and set as Tx, the quality of the product can be determined based on the resin pressure at the completion of the suckback. This is advantageous for determining the quality of a product in which the resin pressure at the time of completion has the greatest effect on the quality of the product. Of course, in any case, it is necessary to perform sampling processing for obtaining the lower limit and the upper limit of the allowable pressure range in accordance with the value of Tx.
[0069]
For products for which it is known from the beginning that the resin pressure at the time of completion of suckback has the greatest effect on the quality of the product, the elapsed time after completion of weighing corresponding to the time of completion of suckback is nothing. It is not necessary to set Tx by bothersome determination, and it is sufficient to read the current value P of the resin pressure and perform the discrimination processing by detecting the suck-back completion signal.
[0070]
In other words, in the configuration in which “the resin pressure detection timing is arbitrarily set within the period from the completion of the measurement to the start of the next injection”, not only the elapsed time after the completion of the measurement is set as a timing setting element, This means that an internal control signal such as a completion signal can also be applied as an element for timing setting. Of course, when setting the resin pressure detection timing using an internal control signal, it is necessary to perform sampling processing for obtaining the lower limit value and the upper limit value of the allowable pressure range in accordance with this internal control signal. is there.
[0071]
【The invention's effect】
Product quality judgment of the present inventionapparatusDetects the resin pressure immediately before the start of injection and compares the resin pressure with a preset allowable pressure range to judge the quality of the product. In addition, the state of the measured molten resin is comprehensively determined immediately before the start of injection, and the quality of the product can be determined accurately.
[0072]
Further, the resin pressure detection timing is arbitrarily set within a period from the completion of the metering to the start of the next injection, and the resin pressure is detected at the set timing for each molding cycle. The determination of the quality of the product is made by comparing with the above, so that the detection timing of the resin pressure can be set in accordance with the timing at which the state of the molten resin that has the greatest influence on the quality of the product is detected. Therefore, if the pass / fail judgment is made at an appropriate timing, it is possible to execute the pass / fail judgment with extremely high accuracy.
[Brief description of the drawings]
FIG. 1 is a judgment of the quality of a product according to the present invention.Equipped with equipmentIt is a block diagram showing an important section of an injection molding machine of one embodiment.
FIG. 2 is a flowchart schematically showing a sequence program and a pass / fail determination process in the embodiment.
FIG. 3 is a flowchart schematically illustrating a sequence program and a pass / fail determination process according to another embodiment;
FIG. 4 is a continuation of a flowchart showing an outline of a sequence program and pass / fail determination processing.
[Explanation of symbols]
1 cylinder
2 Screw
4 Pressure detector
10 Control device
15 Servo amplifier
16 A / D converter
17 CPU for pressure monitor
18 CPU for PMC
20 Servo CPU
24 Non-volatile memory
25 CNC CPU
M1 Injection servo motor
M2 screw rotation motor

Claims (2)

A device for judging the quality of a product in an injection molding machine for holding a screw at a predetermined position after completion of metering, wherein a means for detecting a resin pressure immediately before the start of injection is compared with a predetermined allowable pressure range. means and, before Symbol detection resin pressure product quality decision device in elevation molding machine having means for outputting a failure signal if it is outside the allowable pressure range. A metering completion screw a product quality decision device in an injection molding machine to hold in position, means for arbitrarily setting the resin pressure detection timing in the period until completion next injection start weighing before Symbol Set Timing in the means for detecting the resin pressure, and means for comparing the allowable pressure range set in advance and the detecting resin pressure, the means for pre-Symbol detection resin pressure to output the failure signal if it is outside the allowable pressure range product quality decision device in elevation molding machine having.

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