Monitoring device and monitoring method

Abstract

To provide a monitoring device and monitoring method capable of identifying the location of abnormalities that affect the injection of molten metal by a plunger. [Solution] The monitoring device according to this disclosure includes an acquisition unit that acquires acceleration information of a plunger during injection operation, a determination unit that determines that there is an abnormality in the drive mechanism that drives the plunger when the fluctuation range of the acceleration in the direction of travel of the plunger exceeds a predetermined value and the fluctuation frequency of the acceleration in the direction of travel of the plunger includes a component of a predetermined frequency, and an output unit that outputs the determination result of the determination unit.

Description

Technical Field

[0001] The present disclosure relates to a monitoring device and a monitoring method.

Background Art

[0002] Injection molding machines, also called die-casting machines, are required to detect various abnormalities that affect the injection of molten metal by a plunger and quickly repair them in order to form high-quality molded products. Techniques related to die-casting machines are disclosed, for example, in Patent Document 1.

[0003] The die-casting machine disclosed in Patent Document 1 includes an acceleration sensor capable of detecting acceleration in three axial directions in at least one of a plunger sleeve, a plunger tip, and a plunger rod. Vibration caused by wear of the plunger sleeve or the plunger tip has been detected from the acceleration in the vertical direction detected by the acceleration sensor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Abnormalities that affect the injection of molten metal by the plunger include not only wear but also abnormalities in the drive mechanism that drives the plunger. However, Patent Document 1 has a problem that it cannot detect abnormalities other than wear among the abnormalities that affect the injection of molten metal by the plunger.

[0006] The present disclosure has been made in view of the above background, and an object thereof is to provide a monitoring device and a monitoring method capable of specifying the location where an abnormality that affects the injection of molten metal by the plunger occurs. [Means for solving the problem]

[0007] The monitoring device according to this disclosure includes an acquisition unit that acquires acceleration information of a plunger during injection operation, a determination unit that determines that there is an abnormality in the drive mechanism that drives the plunger when the fluctuation range of the acceleration of the plunger in the direction of travel exceeds a predetermined value and the fluctuation frequency of the acceleration of the plunger in the direction of travel includes a component of a predetermined frequency, and an output unit that outputs the determination result of the determination unit. The monitoring device according to this disclosure can accurately detect abnormalities in the drive mechanism that drives the plunger. In other words, the monitoring device according to this disclosure can detect abnormalities other than galling that affect the injection of molten metal by the plunger. The injection molding machine can repair the abnormal parts as necessary based on the monitoring results of the monitoring device according to this disclosure, thereby enabling the formation of high-quality molded products.

[0008] The monitoring method according to this disclosure acquires acceleration information of a plunger during injection operation, and if the fluctuation range of the acceleration of the plunger in the direction of travel exceeds a predetermined value, and if the fluctuation frequency of the acceleration of the plunger in the direction of travel includes a component of a predetermined frequency, it determines that there is an abnormality in the drive mechanism that drives the plunger and outputs the result of the determination. The monitoring method according to this disclosure can accurately detect abnormalities in the drive mechanism that drives the plunger. In other words, the monitoring method according to this disclosure can detect abnormalities other than galling that affect the injection of molten metal by the plunger. The injection molding machine can repair the abnormal parts as necessary based on the monitoring results of the monitoring method according to this disclosure, thereby enabling the formation of high-quality molded products. [Effects of the Invention]

[0009] This disclosure provides a monitoring device and monitoring method capable of identifying the location of abnormalities that affect the injection of molten metal by a plunger. [Brief explanation of the drawing]

[0010] [Figure 1]This is a schematic cross-sectional view showing an injection molding machine to which the monitoring device described herein is applied. [Figure 2] This is a schematic cross-sectional view showing an injection molding machine to which the monitoring device described herein is applied. [Figure 3] This block diagram shows an example configuration of the monitoring device relating to this disclosure. [Figure 4] This waveform diagram shows the acceleration of the plunger when there is a malfunction in the drive mechanism. [Figure 5] This waveform diagram shows the acceleration of the plunger when there is no abnormality in the drive mechanism. [Figure 6] This waveform diagram shows a magnified portion of the plunger's acceleration when there is a malfunction in the drive mechanism. [Figure 7] This waveform diagram shows a magnified portion of the plunger's acceleration when there is no abnormality in the drive mechanism. [Figure 8] This figure shows the frequency spectrum for each acceleration measurement period when there is a malfunction in the drive mechanism. [Figure 9] This figure shows the frequency spectrum for each acceleration measurement period when there is no abnormality in the drive mechanism. [Figure 10] This is a flowchart showing the operation of the monitoring device related to this disclosure. [Modes for carrying out the invention]

[0011] The embodiments will be described below with reference to the drawings. Note that the drawings are simplified, and the technical scope of the embodiments should not be narrowly interpreted based on their depiction. Furthermore, the same elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0012] <Configuration of injection molding machine 1> First, the configuration of an injection molding machine to which the monitoring device according to the present disclosure is applied will be described using FIGS. 1 and 2. FIGS. 1 and 2 are cross-sectional schematic views showing an injection molding machine 1 to which the monitoring device according to the present disclosure is applied. The injection molding machine 1 is a casting device (so-called die-casting device) that performs casting by injecting molten metal into a mold. FIG. 1 shows the injection molding machine 1 before injection starts, and FIG. 2 shows the injection molding machine 1 immediately after injection starts.

[0013] Note that the right-handed XYZ orthogonal coordinates shown in FIGS. 1 and 2 are for convenience in explaining the positional relationship of the components. The Z direction is the vertical direction, the XY plane is the horizontal plane, and the X direction, Y direction, and Z direction are common among the drawings.

[0014] As shown in FIGS. 1 and 2, the injection molding machine 1 includes a mold 11, a plunger sleeve 12, and a plunger 13.

[0015] The mold 11 includes a movable mold 111 and a fixed mold 112. The movable mold 111 and the fixed mold 112 form a cavity C, which is a hollow space, when clamped. The fixed mold 112 is provided with an opening leading to the cavity C. The opening of the fixed mold 112 forms a gate, which is an entrance to the cavity C, and a runner, which is a flow path for the molten metal M from outside the mold 11 to the gate. The molten metal M is, for example, molten aluminum.

[0016] The plunger sleeve 12 is a cylindrical member. In the examples of FIGS. 1 and 2, the plunger sleeve 12 is arranged to extend in the X direction. An opening 12a for supplying the molten metal M from the outside to the inside of the plunger sleeve 12 is provided on the upper surface of the plunger sleeve 12. In addition, an injection port 12b for injecting the molten metal M from the inside to the outside of the plunger sleeve 12 is provided at the front end of the plunger sleeve 12. The plunger sleeve 12 and the fixed mold 112 are connected such that the injection port 12b of the plunger sleeve 12 communicates with the opening of the fixed mold 112. Further, a fitting port into which the plunger 13 is fitted is provided at the rear end of the plunger sleeve 12.

[0017] The plunger 13 is a rod-shaped member that is inserted into the inside of the plunger sleeve 12 from a fitting hole provided at the rear end portion of the plunger sleeve 12. The plunger 13 is configured to be slidable within the plunger sleeve 12. In the examples of FIGS. 1 and 2, the plunger 13 is configured to be slidable in the X direction within the plunger sleeve 12. For example, from the state of the injection molding machine 1 before the start of injection shown in FIG. 1, as shown in FIG. 2, when the plunger 13 moves (advances) in the negative X direction within the plunger sleeve 12, the molten metal M within the plunger sleeve 12 is injected from the injection port 12b into the cavity C.

[0018] Specifically, the plunger 13 includes a plunger tip 131 and a plunger rod 132. The plunger tip 131 is a cylindrical member having a cross-sectional shape along the inner surface of the plunger sleeve 12, and is inserted into the inside of the plunger sleeve 12 from a fitting hole provided at the rear end portion of the plunger sleeve 12. One end surface of the plunger tip 131 is a surface that contacts the molten metal M supplied into the plunger sleeve 12. The other end surface of the plunger tip 131 is connected to the tip end portion of the rod-shaped plunger rod 132. The rear end portion of the plunger rod 132 is connected to a drive mechanism (not shown).

[0019] When a drive mechanism (not shown) moves the plunger rod 132 in the X direction, the plunger tip 131 slides in the X direction within the plunger sleeve 12. For example, from the state of the injection molding machine 1 before the start of injection shown in FIG. 1, as shown in FIG. 2, when a drive mechanism (not shown) moves the plunger rod 132 in the negative X direction (advances), the plunger tip 131 slides (advances) in the negative X direction within the plunger sleeve 12. Thereby, the molten metal M within the plunger sleeve 12 is injected from the injection port 12b into the cavity C.

[0020] The drive mechanism for driving the plunger 13 is, for example, a hydraulic cylinder whose drive output is controlled by a servo valve. The cylinder rod of the hydraulic cylinder is connected to the base end of the plunger rod 132 via a coupling. However, the drive mechanism for driving the plunger 13 is not limited to a hydraulic cylinder, but any mechanism that has control to slide the plunger 13 in the X direction and has the driving force to inject the molten metal M in the plunger sleeve 12 into the cavity C using the plunger 13.

[0021] After the molten metal M in the plunger sleeve 12 is injected into and fills the cavity C, the molten metal M in the cavity C solidifies to form a molded product P. Subsequently, the movable mold 111 moves to the negative side in the X direction, causing the mold 11 to open. The plunger 13 also moves further to the negative side in the X direction (forward), releasing the molded product P from the fixed mold 112. After the molded product P is removed from the mold 11, the plunger 13 moves to the positive side in the X direction (backward) to return to its position before injection (injection start position). The movable mold 111 also moves to the positive side in the X direction to return to its position before injection. In other words, the mold 11 returns to its clamped state. Subsequently, molten metal M to be used to form the next molded product P is supplied into the plunger sleeve 12 through the opening 12a. This process is repeated in the injection molding machine 1.

[0022] Generally, injection is performed at a low speed from the time the plunger 13 starts pushing out the molten metal M in the plunger sleeve 12 until the plunger sleeve 12 is filled with molten metal M after the air has been removed (preferably until the molten metal M reaches the gate of the mold 11), and then at a high speed until the molten metal M fills the cavity C.

[0023] Here, the injection molding machine 1 is further equipped with an acceleration sensor S. In the examples shown in Figures 1 and 2, the acceleration sensor S is attached near the tip of the plunger rod 132. This prevents the acceleration sensor S from degrading due to the heat of the molten metal M compared to when it is attached to the plunger tip 131. However, the acceleration sensor S may also be attached to the plunger tip 131. In that case, the acceleration sensor S can detect acceleration with greater accuracy compared to when it is attached to the plunger rod 132.

[0024] The acceleration sensor S is a sensor capable of detecting acceleration in three axes. For example, the acceleration sensor S can detect acceleration in the direction of travel (X direction) of the plunger 13 during injection, or acceleration in a direction perpendicular to the direction of travel (parallel to the YZ plane) of the plunger 13 during injection.

[0025] The acceleration measurement by the acceleration sensor S may be performed continuously during the period from the start of injection to the completion of injection, or at any arbitrary timing. That is, the acceleration measurement by the acceleration sensor S may be performed continuously while the plunger tip 131 moves forward within the plunger sleeve 12 from the injection start position to the injection completion position and then moves back to the injection start position, or at any arbitrary timing. The injection start position is the position where the plunger tip 131 begins to extrude the molten metal M within the plunger sleeve 12, and the injection completion position is the position where the injection of the molten metal M into the cavity C is completed.

[0026] In this disclosure, it is assumed that acceleration measurement by the acceleration sensor S is performed during the low-speed injection period, from when the plunger 13 starts to extrude the molten metal M in the plunger sleeve 12 until the plunger sleeve 12 is filled with molten metal M after the air has been released (preferably until the molten metal M reaches the gate of the mold 11).

[0027] In addition, the injection molding machine 1 may be equipped with other sensors instead of the acceleration sensor S, which can detect the acceleration of the plunger 13 in the direction of travel (X direction) during injection, or the acceleration in a direction perpendicular to the direction of travel of the plunger 13 during injection (a direction parallel to the YZ plane).

[0028] Incidentally, the injection molding machine 1 is required to detect and promptly repair various abnormalities that affect the injection of molten metal by the plunger 13 in order to form high-quality molded products. Here, abnormalities that affect the injection of molten metal by the plunger 13 include not only galling but also abnormalities in the drive mechanism that drives the plunger. However, related technologies have had the problem that they cannot detect abnormalities other than galling that affect the injection of molten metal by the plunger 13.

[0029] Therefore, the monitoring device according to this disclosure utilizes the phenomenon in which the drive mechanism that drives the plunger 13 continuously applies vibrations of a predetermined frequency to the plunger 13 when an abnormality occurs in the drive mechanism, and monitors for the presence or absence of abnormalities in the drive mechanism based on acceleration information in the direction of travel of the plunger 13. As a result, the monitoring device according to this disclosure can detect abnormalities other than galling that affect the injection of molten metal by the plunger 13. In other words, the monitoring device according to this disclosure can identify the location of various abnormalities that affect the injection of molten metal by the plunger. The injection molding machine 1 can repair the abnormal location as necessary based on the monitoring results of the monitoring device, thereby enabling the formation of high-quality molded products. The configuration of the monitoring device according to this disclosure will be described below.

[0030] <Configuration of monitoring device 2> Figure 3 is a block diagram showing an example configuration of the monitoring device 2 according to this disclosure. The monitoring device 2 is a device for monitoring the injection molding machine 1. In particular, the monitoring device 2 monitors whether there is any abnormality in the drive mechanism (in this example, a hydraulic cylinder) that drives the plunger 13. In addition, the monitoring device 2 monitors whether there is any galling (wear) of the plunger sleeve 12 or the plunger 13, and whether there is any floating.

[0031] Galling refers to the worn portion of the plunger sleeve 12 or plunger 13. If wear progresses and molten metal enters the worn portion and solidifies, the friction of the solidified molten metal may prevent the plunger 13 from moving smoothly within the plunger sleeve 12. Floating refers to a condition in which the plunger 13 cannot move smoothly within the plunger sleeve 12 due to a malfunction in the coupling between the cylinder rod of the hydraulic cylinder and the base end of the plunger rod 132.

[0032] As shown in Figure 3, the monitoring device 2 comprises an acquisition unit 21, a determination unit 22, and an output unit 23.

[0033] The acquisition unit 21 acquires acceleration information of the plunger 13 during the injection operation, which is detected by the acceleration sensor S, via a wired or wireless network. The acceleration information of the plunger 13 includes information regarding the acceleration of the plunger 13 in the direction of travel (X direction) during the injection operation, and information regarding the acceleration in a direction perpendicular to the direction of travel (parallel to the YZ plane) during the injection operation.

[0034] The determination unit 22 determines whether or not there is an abnormality in the drive mechanism that drives the plunger 13, based on the information regarding the acceleration of the plunger 13 in the direction of travel (X direction) from the acquired acceleration information.

[0035] For example, if the fluctuation range of the acceleration of the plunger 13 in the direction of travel (the amplitude of the waveform representing the acceleration of the plunger 13 in the direction of travel; the vibration of the plunger 13 in the direction of travel) is less than or equal to a first predetermined value, the determination unit 22 determines that there is no abnormality in the drive mechanism that drives the plunger 13. The first predetermined value may be set based on, for example, the fluctuation range of acceleration obtained when injection is performed normally. Alternatively, the first predetermined value may be set based on the average value of acceleration obtained during the acceleration measurement period. The first predetermined value may be fixed or may change in accordance with changes in the reference value.

[0036] On the other hand, if the fluctuation range of the acceleration of the plunger 13 in the direction of travel exceeds a first predetermined value, there is a possibility that there is a problem with the drive mechanism that drives the plunger 13. Therefore, the determination unit 22 then performs a frequency analysis of the acceleration of the plunger 13 in the direction of travel.

[0037] For example, if the determination unit 22 detects a component of a predetermined frequency (e.g., approximately 40 Hz) from the fluctuation frequency of the acceleration of the plunger 13 in the direction of travel, it determines that there is an abnormality in the drive mechanism that drives the plunger 13. Conversely, if the determination unit 22 does not detect a component of the predetermined frequency from the fluctuation frequency of the acceleration of the plunger 13 in the direction of travel, it determines that there is an abnormality in something other than the drive mechanism that drives the plunger 13. The predetermined frequency is set to a value according to the injection conditions of the injection molding machine 1, etc.

[0038] More preferably, the determination unit 22 determines that there is an abnormality in the drive mechanism that drives the plunger 13 if it continuously detects a component of a predetermined frequency (for example, about 40 Hz) from the fluctuation frequency of the acceleration in the direction of travel of the plunger 13 during the acceleration measurement period (in this example, the low-speed injection period). Conversely, if the determination unit 22 does not detect a component of a predetermined frequency from the fluctuation frequency of the acceleration in the direction of travel of the plunger 13 during the acceleration measurement period, it determines that there is an abnormality in a mechanism other than the drive mechanism that drives the plunger 13. Alternatively, if the determination unit 22 detects a component of a predetermined frequency from the fluctuation frequency of the acceleration in the direction of travel of the plunger 13 only during a portion of the acceleration measurement period, it determines that there is an abnormality in a mechanism other than the drive mechanism that drives the plunger 13.

[0039] Furthermore, the determination unit 22 may determine whether there is galling of the plunger sleeve 12 or the plunger 13, and whether there is floating, based on the information regarding the acceleration in the direction perpendicular to the direction of travel of the plunger 13 (the direction parallel to the YZ plane) from the acquired acceleration information.

[0040] For example, if the fluctuation range of acceleration in the direction perpendicular to the direction of travel of the plunger 13 (amplitude of the waveform representing the acceleration in the direction perpendicular to the direction of travel of the plunger 13; vibration in the direction perpendicular to the direction of travel of the plunger 13) is less than or equal to a second predetermined value, the determination unit 22 determines that neither galling nor floating abnormalities have occurred. On the other hand, if the fluctuation range of acceleration in the direction perpendicular to the direction of travel of the plunger 13 exceeds the second predetermined value, the determination unit 22 determines that neither galling nor floating abnormalities have occurred. If either galling or floating abnormalities occur, the injection molding machine 1 may not be able to perform accurate injection operations, and in that case, defective molded products P may be formed.

[0041] The second predetermined value may be set based on, for example, the range of acceleration fluctuations obtained when injection is performed normally. Alternatively, the second predetermined value may be set based on the average value of acceleration obtained during the acceleration measurement period. The second predetermined value may be fixed or may change in response to changes in the reference value.

[0042] Furthermore, the determination unit 22 may determine whether there is galling or floating by considering not only the amplitude of the fluctuation of the acceleration perpendicular to the direction of travel of the plunger 13, but also the frequency of the fluctuation of the acceleration perpendicular to the direction of travel of the plunger 13. For example, if the amplitude of the fluctuation of the acceleration perpendicular to the direction of travel of the plunger 13 exceeds a second predetermined value, and the frequency of the fluctuation of the acceleration perpendicular to the direction of travel of the plunger 13 includes a second predetermined frequency, the determination unit 22 may determine that either galling or floating is occurring.

[0043] The second predetermined frequency may be set based on, for example, the frequency of acceleration fluctuations obtained when injection is performed normally. Alternatively, the second predetermined frequency may be set based on the average value of the acceleration fluctuation frequencies obtained during the acceleration measurement period.

[0044] The output unit 23 outputs the determination result of the determination unit 22 as the monitoring result of the monitoring device 2. The determination result of the determination unit 22 is displayed on a monitor (not shown), for example. This allows the manager of the injection molding machine 1 to refer to the determination result displayed on the monitor and, if necessary, repair the drive mechanism where an abnormality has occurred, repair the plunger sleeve 12 or plunger 13 where galling has occurred, or repair the coupling where floating has occurred.

[0045] Alternatively, the output unit 23 may be configured to output instructions to the control unit (not shown) of the injection molding machine 1 according to the determination result of the determination unit 22. For example, if it is determined that any abnormality has occurred in the injection molding machine 1, the output unit 23 outputs an instruction to stop the injection operation to the control unit of the injection molding machine 1. As a result, the control unit of the injection molding machine 1 stops the injection operation of the injection molding machine 1 in accordance with the instructions from the monitoring device 2. After the injection operation of the injection molding machine 1 is stopped, the manager of the injection molding machine 1 can repair the abnormal part of the injection molding machine 1. Note that the monitoring device 2 may be used as part of the control unit of the injection molding machine 1.

[0046] <Experimental Results> Next, the experimental results of the injection operation of injection molding machine 1 will be explained using Figures 4 to 9. Note that the component of gravity acceleration in the acceleration of plunger 13 is not considered.

[0047] Figure 4 is a waveform diagram showing the acceleration of the plunger 13 when there is a malfunction in the drive mechanism. Figure 5 is a waveform diagram showing the acceleration of the plunger 13 when there is no malfunction in the drive mechanism. Figures 4 and 5 also show the stroke of the plunger 13 (distance from the ejection start position of the plunger 13) and the movement speed of the plunger 13.

[0048] In the example shown in Figure 4, the injection velocity changes subtly during the low-speed injection period. Furthermore, in the example shown in Figure 4, of the vibrations in the acceleration of the plunger 13 in the direction of travel and the vibrations in the acceleration perpendicular to the direction of travel of the plunger 13, the vibration in the acceleration of the plunger 13 in the direction of travel is linked to the subtle changes in injection velocity. In other words, the subtle changes in injection velocity are caused by vibrations in the acceleration of the plunger 13 in the direction of travel. Here, as shown in Figure 4, before the drive mechanism was repaired, the vibration of the acceleration of the plunger 13 in the direction of travel was greater than the first predetermined value. In contrast, as shown in Figure 5, after the drive mechanism was repaired, the vibration of the acceleration of the plunger 13 in the direction of travel was suppressed to below the first predetermined value. Thus, when there is a problem with the drive mechanism, the fluctuation in the acceleration of the plunger 13 in the direction of travel is greater than when there is no problem with the drive mechanism.

[0049] Figure 6 is a waveform diagram showing a magnified portion of the acceleration of the plunger 13 when there is a malfunction in the drive mechanism. Figure 7 is a waveform diagram showing a magnified portion of the acceleration of the plunger 13 when there is no malfunction in the drive mechanism. Figures 6 and 7 show waveform diagrams for a portion of the low-speed injection period.

[0050] Comparing Figures 6 and 7, the range of acceleration fluctuation in the direction perpendicular to the direction of travel of the plunger 13 is approximately the same regardless of whether or not there is a malfunction in the drive mechanism. In contrast, the range of acceleration fluctuation in the direction of travel of the plunger 13 is larger when there is a malfunction in the drive mechanism than when there is no malfunction in the drive mechanism.

[0051] Figure 8 shows the frequency spectra for each acceleration measurement period T11 to T14 when there is an abnormality in the drive mechanism. Figure 9 shows the frequency spectra for each acceleration measurement period T21 to T24 when there is no abnormality in the drive mechanism. The acceleration measurement period T11 to T14 in Figure 8 corresponds to the acceleration measurement period T11 to T14 in Figure 6. The acceleration measurement period T21 to T24 in Figure 9 corresponds to the acceleration measurement period T21 to T24 in Figure 7.

[0052] As shown in Figure 8, when there is a malfunction in the drive mechanism, a predetermined frequency component is continuously detected from the fluctuation frequency of the acceleration in the direction of travel of the plunger 13 during the acceleration measurement period T11 to T14. In the example in Figure 8, a predetermined frequency component of approximately 40 Hz with an amplitude of 0.1 mm or more is continuously detected throughout the entire acceleration measurement period T11 to T14. Furthermore, a predetermined frequency component of approximately 40 Hz with an amplitude of approximately 0.3 mm or more is detected for most of the acceleration measurement period T11 to T14 (the period from T12 to T14). In contrast, as shown in Figure 9, when there is no malfunction in the drive mechanism, the predetermined frequency component is not continuously detected from the fluctuation frequency of the acceleration in the direction of travel of the plunger 13 during the acceleration measurement period T21 to T24. In the example in Figure 9, a predetermined frequency component of approximately 40 Hz with an amplitude of 0.1 mm or more is detected only during the period from T22 to T24 within the acceleration measurement period T21 to T24. Furthermore, in all acceleration measurement periods T21 to T24, no predetermined frequency component of approximately 40 Hz with an amplitude of approximately 0.3 mm or more was detected. Thus, when there is an abnormality in the drive mechanism, a predetermined frequency component with a larger amplitude is continuously detected from the fluctuation frequency of the acceleration in the direction of travel of the plunger 13, compared to when there is no abnormality in the drive mechanism.

[0053] <Operation of monitoring device 2> Next, we will explain the operation of the monitoring device 2 using Figure 10. Figure 10 is a flowchart showing the operation of the monitoring device 2.

[0054] First, the monitoring device 2 acquires acceleration information of the plunger 13 during the injection operation, which is detected by the acceleration sensor S (step S101). The acceleration information of the plunger 13 includes information regarding the acceleration of the plunger 13 in the direction of travel (X direction) during the injection operation, and information regarding the acceleration in a direction perpendicular to the direction of travel (parallel to the YZ plane) during the injection operation.

[0055] Subsequently, the monitoring device 2 determines whether or not there is an abnormality in the drive mechanism that drives the plunger 13 based on the acceleration information in the direction of travel of the plunger 13 (step S102).

[0056] For example, if the fluctuation range of the acceleration of the plunger 13 in the direction of travel is less than or equal to a first predetermined value (NO in step S102), the monitoring device 2 determines that there is no abnormality in the drive mechanism that drives the plunger 13 (step S103). On the other hand, if the fluctuation range of the acceleration of the plunger 13 in the direction of travel exceeds the first predetermined value (YES in step S102), there is a possibility that there is an abnormality in the drive mechanism that drives the plunger 13, so the monitoring device 2 then performs a frequency analysis of the acceleration of the plunger 13 in the direction of travel (step S104).

[0057] For example, if the monitoring device 2 continuously detects a component of a predetermined frequency (e.g., approximately 40 Hz) from the fluctuation frequency of the acceleration in the direction of travel of the plunger 13 during the acceleration measurement period (in this example, the low-speed injection period) (YES in step S104), it determines that there is an abnormality in the drive mechanism that drives the plunger 13 (step S105). Conversely, if the monitoring device 2 does not detect a component of the predetermined frequency from the fluctuation frequency of the acceleration in the direction of travel of the plunger 13 during the acceleration measurement period (NO in step S104), it determines that there is an abnormality in something other than the drive mechanism that drives the plunger 13 (step S106). Or, if the monitoring device 2 detects a component of the predetermined frequency from the fluctuation frequency of the acceleration in the direction of travel of the plunger 13 only during a portion of the acceleration measurement period (NO in step S104), it determines that there is an abnormality in something other than the drive mechanism that drives the plunger 13 (step S106).

[0058] Subsequently, the monitoring device 2 determines whether or not there is galling of the plunger sleeve 12 or the plunger 13, and whether or not there is floating, based on acceleration information in a direction perpendicular to the direction of travel of the plunger 13 (step S107).

[0059] For example, if the fluctuation range of the acceleration perpendicular to the direction of travel of the plunger 13 is less than or equal to the second predetermined value (NO in step S107), the monitoring device 2 determines that neither galling nor floating abnormalities have occurred (step S108). On the other hand, if the fluctuation range of the acceleration perpendicular to the direction of travel of the plunger 13 exceeds the second predetermined value (YES in step S107), the monitoring device 2 determines that neither galling nor floating abnormalities have occurred (step S109).

[0060] Subsequently, the monitoring device 2 outputs the judgment result (step S110). The judgment result is displayed on a monitor (not shown), for example. This allows the manager of the injection molding machine 1 to refer to the judgment result displayed on the monitor and repair the injection molding machine 1 as necessary.

[0061] Alternatively, the monitoring device 2 may output instructions to the control unit (not shown) of the injection molding machine 1 according to the determination result. For example, if it is determined that any abnormality has occurred in the injection molding machine 1, the monitoring device 2 outputs an instruction to the control unit of the injection molding machine 1 to stop the injection operation. As a result, the control unit of the injection molding machine 1 stops the injection operation of the injection molding machine 1 in accordance with the instruction from the monitoring device 2. After the injection operation of the injection molding machine 1 is stopped, the manager of the injection molding machine 1 can repair the abnormal part of the injection molding machine 1. Note that the monitoring device 2 may be used as part of the control unit of the injection molding machine 1.

[0062] Thus, the monitoring device 2 according to this disclosure utilizes the phenomenon in which the drive mechanism that drives the plunger 13 continuously applies vibrations of a predetermined frequency to the plunger 13 when an abnormality occurs in the drive mechanism, and monitors for the presence or absence of abnormalities in the drive mechanism based on acceleration information in the direction of travel of the plunger 13. As a result, the monitoring device 2 according to this disclosure can detect abnormalities other than galling that affect the injection of molten metal by the plunger 13. In other words, the monitoring device 2 according to this disclosure can identify the location of various abnormalities that affect the injection of molten metal by the plunger 13. The injection molding machine 1 can repair the abnormal location as necessary based on the monitoring results of the monitoring device 2, thereby forming a high-quality molded product P.

[0063] Furthermore, this disclosure can be realized by having a CPU (Central Processing Unit) execute a computer program to perform some or all of the processing in the monitoring device 2 or the injection molding machine 1 equipped with the monitoring device 2.

[0064] The program described above includes, when loaded into a computer, a set of instructions (or software code) for causing the computer to perform one or more of the functions described in the embodiments. The program may be stored in a non-temporary computer-readable medium or a physical storage medium. Examples, but not limited to, include RAM (Random-Access Memory), ROM (Read-Only Memory), flash memory, SSD (Solid-State Drive), or other memory technologies, CD-ROM, DVD (Digital Versatile Disc), Blu-ray® disc, or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage devices. The program may be transmitted over a temporary computer-readable medium or a communication medium. Examples, but not limited to, include temporary computer-readable medium or a communication medium that includes electrically, optically, acoustically, or otherwise propagating signals.

[0065] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as can be understood by those skilled in the art within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate. [Explanation of symbols]

[0066] 1 Injection molding machine, 2 Monitoring device, 11 Mold, 12 Plunger sleeve, 12a Opening, 12b Injection port, 13 Plunger, 21 Acquisition unit, 22 Judgment unit, 23 Output unit, 111 Movable mold, 112 Fixed mold, 131 Plunger tip, 132 Plunger rod, C Cavity, M Molten metal, S Acceleration sensor

Claims

1. An acquisition unit that acquires acceleration information of the plunger during the injection operation, A determination unit determines that there is an abnormality in the drive mechanism that drives the plunger if the fluctuation range of the acceleration of the plunger in the direction of travel exceeds a predetermined value, and if the fluctuation frequency of the acceleration of the plunger in the direction of travel includes a component of a predetermined frequency. An output unit that outputs the determination result of the determination unit, A monitoring device equipped with this device.

2. The determination unit determines that there is an abnormality in the drive mechanism that drives the plunger if the fluctuation range of the acceleration in the direction of travel of the plunger exceeds the predetermined value, and if the fluctuation frequency of the acceleration in the direction of travel of the plunger continuously includes a component of the predetermined frequency during the acceleration measurement period. The monitoring device according to claim 1.

3. The determination unit determines that there is an abnormality other than the drive mechanism that drives the plunger, even if the fluctuation range of the acceleration of the plunger in the direction of travel exceeds the predetermined value, if the fluctuation frequency of the acceleration of the plunger in the direction of travel contains a component of the predetermined frequency only for a part of the acceleration measurement period, or if the fluctuation frequency of the acceleration of the plunger in the direction of travel does not contain a component of the predetermined frequency during the acceleration measurement period. The monitoring device according to claim 2.

4. The determination unit further determines whether or not there is galling in at least the plunger sleeve and the plunger, based on the information relating to the acceleration in the direction perpendicular to the direction of travel of the plunger from the acceleration information. The monitoring device according to claim 1.

5. Acquire acceleration information of the plunger during the injection operation. If the fluctuation range of the acceleration of the plunger in the direction of travel exceeds a predetermined value, and if the fluctuation frequency of the acceleration of the plunger in the direction of travel includes a component of a predetermined frequency, it is determined that there is an abnormality in the drive mechanism that drives the plunger. Output the result of the above determination. Monitoring method.

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