Control device for molding machine, method of detecting galling, and molding machine

Abstract

To provide a control device capable of determining a galling of a screw against a heating cylinder without being affected by a surrounding temperature.SOLUTION: In a molding machine for performing extrusion molding or injection molding having a heating cylinder (73) and a screw (71) inserted in the heating cylinder (73), a control device (100) determines a galling of the screw (71) against the heating cylinder (73). The control device (100) comprises: one or a plurality of vibration detection units (106) installed on any portion of the molding machine; and a determination unit (101) for determining a galling on the basis of the vibration information detected by the vibration detection unit (106).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a molding machine that uses a screw to knead and melt raw materials made of resin material and extrusion-molding or injection-molding the raw materials, and relates to a method for determining whether a screw has galled against a heater barrel. [Background technology]

[0002] In plastic molding machines, galling of the screw against the heating barrel can lead to accidents such as screw damage or screw rotation stoppage. To prevent accidents in this type of molding machine, methods for detecting screw galling have been proposed. For example, Patent Document 1 (Patent Document 1) installs a radiation thermometer in at least the melting portion of the heating barrel, and determines the temperature profile of the molten resin inside the heating barrel and the temperature profile on the screw surface from the output of this radiation thermometer. Patent Document 1 proposes predicting and detecting galling of the screw against the heating barrel from one or both of the waveform between these two temperature profiles and abnormal temperature changes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 09-52276 Summary of the Invention [Problem to be solved by the invention]

[0004] The surface temperature of the heating barrel rises and falls depending on the degree of heat radiation into the atmosphere (degree of heat radiation and cooling), and fluctuates depending on the ambient temperature. Therefore, for example, the surface temperature of the heating barrel fluctuates between day and night, or the surface temperature of the heating barrel fluctuates depending on the amount of air conditioning or heating air that hits it due to changes in the air flow in the factory. Therefore, with the method of detecting galling based on temperature changes, as in Patent Document 1, there is a risk of erroneously detecting galling if the temperature around the molding machine, including the heating barrel, changes.

[0005] SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a control device that can determine whether a screw has galled against a heater barrel without being affected by the ambient temperature. [Means for solving the problem]

[0006] The present invention provides A control device for determining whether a screw has galled against a heating barrel in a molding machine for extrusion molding or injection molding, the control device comprising: a heating barrel and a screw inserted into the heating barrel; one or more vibration detection units provided at any location in the molding machine; and a determination unit that determines whether or not there is galling based on vibration information detected by the vibration sensor.

[0007] In the determination unit, preferably, The detected vibration frequency obtained from the vibration information is It includes a first reference vibration frequency that is predetermined as not occurring in a normal state where no galling occurs, or When the detected vibration level includes a second reference vibration frequency that is predetermined as a vibration level that increases in an abnormal state where galling occurs compared to a normal state, galling is determined to have occurred.

[0008] The first and second reference vibration frequencies are preferably defined as a determination threshold equal to or greater than a predetermined frequency.

[0009] In the determination unit, preferably, Galling is determined by the vibrations that occur every 2±1 / 4 times the screw rotation period.

[0010] In the determination unit, preferably, Galling is determined by continuously increasing vibration.

[0011] The vibration detection unit preferably includes: Vibration information is detected at the body of the heating barrel or at the rear end side of the heating barrel.

[0012] The vibration detection unit preferably includes: Vibration information is detected in a member fixed to the body of the heating barrel or in a support member that fixes and supports the heating barrel.

[0013] The determination unit preferably When the inlet for the raw material to be molded is in a closed state, galling is judged.

[0014] An input area for the decision threshold; The normal waveform of the frequency spectrum obtained by frequency analysis of vibration information, It is preferable to provide a display device capable of displaying on the same screen a waveform of an abnormal state of a frequency spectrum obtained by frequency analysis of vibration information.

[0015] A method for determining whether a screw has galled against a heating barrel in a molding machine for extrusion molding or injection molding, the molding machine having a heating barrel and a screw inserted into the heating barrel, A first step of detecting vibration information at any part of a molding machine; and a second step of determining whether or not there is galling based on the vibration information.

[0016] There is provided a molding machine for extrusion molding or injection molding, which includes a heating barrel and a screw inserted into the heating barrel. This molding machine includes any one of the control devices described above. [Effects of the Invention]

[0017] The control device of the present invention determines whether or not there is galling based on vibrations caused by galling, which is unlikely to be affected by the ambient temperature, and therefore, according to the present invention, it is possible to determine whether or not there is galling with high accuracy. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing a configuration of a molding machine according to an embodiment. [Figure 2] 10A and 10B are diagrams illustrating vibrations when galling occurs. [Figure 3]10A and 10B are diagrams illustrating vibration when galling does not occur. [Figure 4] FIG. 2 is a diagram showing the behavior of the screw when the screw is rotating. [Figure 5] FIG. 10 is a diagram showing the relationship between the rotation phase of the screw and the frequency distribution of the generated vibration. [Figure 6] FIG. 10 is a diagram showing an example of a display when abnormal vibration is detected. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments will be described with reference to the accompanying drawings. The injection device 1 according to the embodiment is combined with a mold clamping device (not shown) to form an injection molding machine. The injection device 1 detects vibrations caused by galling of the screw 71 against the heating barrel 73 and determines whether galling has occurred based on the detected vibration information. The frequency components used to determine galling are specific to galling, so galling can be determined with high accuracy even if the ambient temperature changes. In the embodiment, the presence or absence of galling is determined based on vibration information detected in the injection section 70. This is because it is possible to distinguish between the vibration frequency in a normal plasticization state (normal state) in which galling has not occurred and the vibration frequency in an abnormal state in which galling has occurred.

[0020] In the present invention, a normal plasticization state (normal state) without galling refers to a plasticization state in which, when the injection device 1 is stopped and the screw 71 is removed from the heating barrel 73 and inspected, no sliding marks are found on the heating barrel 73 and screw 71, or slight sliding marks (scratches) are found on the heating barrel 73 and screw 71 but no galling marks such as chipping marks are found on the heating barrel 73 and screw 71. The qualitative meaning of the normal state is as described above, but the normal state or abnormal state is also quantitatively determined based on the vibration frequency. An example of the configuration of the injection device 1, a method for determining galling related to the injection device 1, and the effects achieved by the injection device 1 will be described below in that order.

[0021] [Configuration of injection unit 1: see Figure 1] [Overall configuration of injection unit 1] As shown in FIG. 1, the injection device 1 includes a base 10, a drive unit 20 supported by the base 10 and responsible for moving the screw 71 back and forth and rotating the screw 71, an injection unit 70 including the screw 71 and involved in injecting the resin, and a detection unit 105 for determining whether the screw 71 has galled into the heating barrel 73. In the injection device 1, the side marked with F in Fig. 1 is defined as the front, and the side marked with R is defined as the rear. The definitions of the front F and rear R include relative meanings. Furthermore, the width direction W, the length direction L, and the height direction H of the injection device 1 are defined as shown in Fig. 1.

[0022] [Base 10: See Figure 1] As shown in FIG. 1, the base 10 includes a base 11 extending from the front F to the rear R, a front support part 12 supporting the heating cylinder 73 at the front F of the base 11, and a rear support part 16 provided at a distance from the front support part 12 on the rear R side and supporting the rotational drive source of the screw 71.

[0023] The front support part 12 is fixed to the base 11 and supports the heating barrel 73 at a fixed position. In addition to supporting the heating barrel 73, the front support part 12 is provided with an input path 13 for inputting resin pellets, which are the raw material for molding, into the heating barrel 73. The input path 13 penetrates in the height direction H between the top surface of the front support part 12 and the heating barrel 73. A hopper 14 is mounted on the top surface of the front support part 12 to store resin pellets and supply them toward the input path 13. A shutter 15 is provided between the hopper 14 and the input path 13. This shutter 15 has an open state in which resin pellets stored in the hopper 14 fall and are supplied to the input path 13, and a closed state in which resin pellets are stored inside the hopper 14. The open state and closed state here mean fully open or fully closed, but the shutter 15 is not limited to being fully open or fully closed, and may be in an intermediate state between the fully open and fully closed states. The front support portion 12 is provided with a vibration sensor 106 for detecting galling and an open / close detection sensor 107 for detecting whether the shutter 15 is open or closed.

[0024] The rear support part 16 is placed on a pair of guide rails 19 fixed on the base 11 with a gap therebetween in the width direction W, and is capable of reciprocating forward F and backward R while remaining on the guide rails 19. The rear support part 16 supports a first drive part 30 (described later), and is provided with an accommodation chamber 17 that particularly accommodates an input shaft 35 of the drive part 30.

[0025] [Drive unit 20: see Figure 1] Next, the driving unit 20 will be described. The drive unit 20 includes a first drive unit 30 that rotates the screw 71 and a second drive unit 50 that moves the screw 71 forward and backward via the rear support unit 16 .

[0026] [First drive unit 30: see Figure 1] 1, the first drive unit 30 includes an electric motor 31 supported by the rear support unit 16, and an output pulley 33 fixed to an output shaft 32 of the electric motor 31. The first drive unit 30 also includes an input shaft 35 fitted with the screw shaft 71B, and an input pulley 37 fixed to the input shaft 35. The first drive unit 30 also includes a transmission belt 34 wound around the output pulley 33 and the input pulley 37. The rotational motion of the electric motor 31 is transmitted to the screw shaft 71B via the transmission belt 34 and the input shaft 35, causing the screw 71 to rotate. The input shaft 35 is rotatably supported inside the accommodation chamber 17 while being supported by bearings 38 and 39. In the present embodiment, an example has been shown in which the power of the electric motor 31 is transmitted to the input shaft 35 using a pulley and a transmission belt, but instead of the pulley and the transmission belt, the power may be transmitted using a known gear train such as a spur gear, a helical gear, or a worm gear.

[0027] [Second driving unit 50: see Figure 1] The second drive unit 50 moves the rear support unit 16, which is slidably mounted on a guide rail 19 fixed to the base 11, forward or backward, that is, moves the rear support unit 16 forward and backward. When the rear support unit 16 moves forward and backward, the screw 71 moves forward and backward. The second drive unit 50 includes a ball screw 51 and an electric motor 55 that applies a rotational driving force to the ball screw 51. The second drive unit 50 also includes an input pulley 53 fixed to a ball screw shaft 51A of the ball screw 51, and an output pulley 57 fixed to an output shaft 56 of the electric motor 55. A transmission belt 58 is wound between the input pulley 53 and the output pulley 57. Therefore, when the electric motor 55 is driven to rotate, the ball screw shaft 51A of the ball screw 51 rotates. Note that, without using the input pulley 53, the output pulley 57, and the transmission belt 58, the electric motor 55 may be fixed to a front support 59 and the output shaft 56 of the electric motor 55 may be directly connected to the ball screw shaft 51A.

[0028] The ball screw 51 includes a ball screw shaft 51A and a ball screw nut 51B fitted onto the ball screw shaft 51A. The ball screw shaft 51A is rotatably supported by a front support 59 and a rear support 61 at the front F and rear R of the base 11. The ball screw nut 51B moves back and forth in the front-to-rear direction as the ball screw shaft 51A rotates. The ball screw nut 51B is connected to the rear support part 16 by a connector 63. The connector 63 is fixed to both the ball screw nut 51B and the rear support part 16. Therefore, when the ball screw nut 51B moves back and forth in accordance with the rotation of the ball screw shaft 51A, the rear support part 16 also moves back and forth via the connector 63.

[0029] Since the second drive unit 50 is configured as described above, the screw 71 can move forward and backward when the electric motor 55 rotates forward or backward. In this embodiment, both the rear support 61 and the front support 59 of the second drive unit 50 are fixed to the base 11, but this is not limited to this. The front support 59 may be fixed to the front support part 12, and the ball screw shaft 51A may be cantilevered by the front support 59 without providing the rear support 61.

[0030] [Injection section 70: see Figure 1] 1, the injection unit 70 includes a screw 71 and a heating barrel 73 into which the screw 71 is inserted. The injection unit 70 also includes a heating barrel head 75 provided at the front end of the heating barrel 73 in the forward direction F, and an injection nozzle 77 provided at the front end of the heating barrel head 75.

[0031] The screw 71 includes a main body 71A having a spiral flight formed on its outer periphery, and a screw shaft 71B connected to the rear end of the main body 71A. The screw shaft 71B is fitted to the input shaft 35, so the screw 71 can be rotated by the first drive unit 30 and moved back and forth by the second drive unit 50. In the screw 71, the top surface of the flight becomes the outermost peripheral surface of the screw 71.

[0032] The heating barrel 73 is fixed to the front support part 12 . A raw material inlet 74 is formed in the heating barrel 73, through which resin pellets are introduced via the introduction path 13. The raw material inlet 74 penetrates the inside and outside of the heating barrel 73, and communicates with the introduction path 13 formed in the front support part 12. Therefore, opening / closing of the shutter 15 means opening / closing of the raw material inlet 74. The screw 71 housed inside the heating barrel 73 can move back and forth in the front-rear direction and rotate inside the heating barrel 73 . Heating means such as a band heater or cartridge heater (not shown) are provided around the heating barrel 73, mainly forward of the front support portion 12, and the resin material inside the heating barrel 73 is heated by supplying electricity from a power source (not shown).

[0033] [Control device 100: see Figure 1] Next, the control device 100 will be described. However, the following description will focus on determining whether or not there is galling between the screw 71 and the heating barrel 73, and a description of the control of the operation of the drive unit 30 will be omitted.

[0034] The control device 100 includes a determination unit 101 that acquires detection information from various sensors and determines whether or not there is galling based on the acquired detection information, a display unit 103 that displays the determination result from the determination unit 101, and a detection unit 105 that acquires the detection information. The determination unit 101 is made up of a computer device, and the display unit 103 is made up of a display device such as an LCD (Liquid Crystal Display) that displays images in response to instructions from the computer device.

[0035] [Judgment unit 101] To determine whether galling has occurred, the determination unit 101 acquires vibration information detected in the injection unit 70 from the detection unit 105 and analyzes the acquired vibration information to generate a waveform distribution of the frequency spectrum of the vibration. The determination unit 101 checks whether the generated frequency distribution contains a component in a predetermined high-frequency range, and if the high-frequency component is included, determines that galling has occurred in the injection unit 70. For this determination, the determination unit 101 holds a determination threshold that identifies the high-frequency component and determines the occurrence of galling by comparing the generated frequency distribution with the determination threshold. That is, the method for determining whether galling has occurred in the heating barrel 73 of the screw 71 in a molding machine that performs extrusion molding or injection molding in this embodiment includes a first step of detecting vibration information at any location in the molding machine and a second step of determining whether galling has occurred based on the vibration information. When determining that galling has occurred, determination unit 101 instructs display unit 103 to display that galling has occurred. Note that, in the present invention, high frequency and low frequency simply refer to a frequency range that is relatively high or low, and are not limited to conventional frequency ranges in electrical or radio wave technology (for example, a frequency range of several tens of kilohertz or more, or several megahertz to several hundred megahertz, is called high frequency). In other words, low-frequency vibration simply refers to vibrations that produce a low rumbling sound, for example, that occur in a normal plasticized state (normal state), and high-frequency vibration simply refers to vibrations that produce a high-pitched clicking sound, such as metal clicking, that occur in a galling state (abnormal state).

[0036] The frequency of vibrations generated by high surface pressure sliding between metals can be identified by vibration frequency analysis using FFT (Fast Fourier Transformation) or by extracting high frequency components using a high pass filter, etc. If the identified frequency is determined to be equal to or greater than the determination threshold, it is determined that galling has occurred, and a display and warning is issued on the display unit 103, thereby making it easier to determine galling.

[0037] [Display unit 103: see Figure 1] In accordance with an instruction from the determining unit 101, the display unit 103 issues a warning (alarm) that galling has occurred. The display unit 103 may be a display device 103A such as an LCD that can display text or images such as "Scaling has occurred," an indicator light 103B such as a rotating light or a flashing light in red or yellow, or a speaker 103C that issues an audio warning of scalding.

[0038] [Detection unit 105: see Figure 1] The detection unit 105 includes vibration sensors 106A, 106B, 106C, and 106D that detect vibrations, and an open / close detection sensor 107 that detects the opening and closing of the shutter 15. While four vibration sensors 106A, 106B, 106C, and 106D are provided here as an example, only one vibration sensor may be used as long as it can detect vibrations corresponding to galling. When multiple vibration sensors are provided, the vibration information detected by the multiple sensors may be combined for determination. Vibration sensor 106A is provided on the body of the heating barrel 73, and vibration sensor 106B is provided on the rear end of the heating barrel 73, and they detect vibrations at their respective locations. Vibration sensor 106C is provided on a member fixed to the body of the heating barrel 73, and vibration sensor 106D is provided on the front support portion 12, and they detect vibrations at their respective locations. Here, the member that fixes vibration sensor 106C to the body of the heating barrel 73 is preferably made of a high-hardness material that can transmit high-frequency waves without attenuation. Furthermore, the vibration sensors, such as vibration sensors 106B and 106D, are preferably located on the front support portion 12 or the rear side of the front support portion 12, away from the heating portion of the heating barrel 73, to reduce the effect of the high temperature of the heating barrel 73 on the vibration sensor detection accuracy (temperature characteristics). Vibration information detected by one or more of vibration sensors 106A, 106B, 106C, and 106D is acquired by the determination unit 101 and used to determine whether there is galling. Furthermore, an open / closed sensor 107 is provided as a preferred example. While the open / closed sensor 107 is effective in clarifying the criteria for the open / closed state of the shutter 15, it is not an essential element in this embodiment. The open / closed sensor 107 detects the open / closed state of the shutter 15, and information regarding the detected open / closed state is acquired by the determination unit 101 and used to determine whether there is galling. The open / close detection sensor 107 has a mode A for detecting the closed state of the shutter 105 and a mode B for detecting the open state of the shutter 105. In this embodiment, sensors of either mode are applied. When mode A is applied, a galling determination is made if a closed state is detected, and when mode B is applied, a galling determination is made if an open state is not detected.

[0039] There are three indicators that represent the vibration of an object: acceleration, velocity, and displacement. Therefore, a vibration sensor has the function of measuring physical quantities that serve as these indicators and converting them into electrical quantities such as voltage and current. There are two types of vibration sensors: contact and non-contact. These two types of vibration sensors are used depending on the physical quantities (acceleration, velocity, displacement) to be measured and the conditions of the object to be measured. Contact vibration sensors are used to measure acceleration, and non-contact vibration sensors are used to measure velocity and displacement. Contact vibration sensors are classified into frequency change type, piezoelectric type, conductive type, servo type, etc., while non-contact vibration sensors are classified into eddy current type, capacitance type, optical type, etc. Any of these vibration sensors can be used in this embodiment.

[0040] [Difference in vibration due to presence or absence of galling: Figures 2 and 3] The difference in vibration depending on whether or not galling occurs will be described below. In this embodiment, galling between the screw 71 and the heating barrel 73 may be simply referred to as galling.

[0041] [Vibration when galling occurs (abnormal state): See Figure 2] When solid resin pellets PP are plasticized to form molten resin MP, galling occurs between the inner circumferential surface 73I of the heating barrel 73 and the outer circumferential surface 72O of the screw flight 72. This occurs when the surface pressure or relative speed due to the sliding between the two metal surfaces becomes excessively high. Specifically, when the inner circumferential surface 73I and the screw flight 72 slide against each other under excessively high surface pressure or relative speed, the friction at the sliding points heats up, and the inner circumferential surface 73I and the screw flight 72 may adhere to each other. Galling occurs when the screw 71 is forcibly rotated in this state, tearing off the adhered portion. Galling generates adhered metal foreign matter (galling fragments MC) that slides directly against the inner circumferential surface 73I, or when the galling fragments MC slide directly against the outer circumferential surface 72O. Because this sliding portion is metal-to-metal, vibrations containing high-frequency components HF are generated, compared to the vibrations LF generated during resin shearing, as described below. Furthermore, since galling occurs when the surface pressure or relative speed is excessively high, the frequency increases and the vibration level also increases.

[0042] [Normal vibration: See Figure 3] During plasticization under normal conditions where no galling occurs, the inner circumferential surface 73I of the heating barrel 73 and the outer circumferential surface 72O of the screw flight 72 slide against each other via a thin film of molten resin MP. In other words, under normal conditions, a thin film of molten resin MP exists between the inner circumferential surface 73I of the heating barrel 73 and the outer circumferential surface 72O of the screw flight 72, preventing direct metal-to-metal sliding. Even if metal-to-metal sliding does occur, it is extremely minor and difficult to detect. Furthermore, during the plasticization operation of the screw 71, friction between the resin pellets PP caused by the rotation of the screw 71 is friction between resins, which are much softer than metals, so the vibration LF generated has a relatively low frequency. Even if the vibration generated by resin-to-resin friction contains higher-frequency components than normal, resin is less hard than metal and has elasticity, so the generated vibration is not as high-frequency as metal-to-metal sliding. Furthermore, the vibration level is also lower than when galling occurs. Even if the frequency becomes high, the vibrations are absorbed by the softened molten resin MP in the screw groove and the thin resin film consisting of the molten resin MP between the inner surface 73I of the heating barrel 73 and the outer surface 72O of the screw flight 72, and the vibrations are not easily transmitted to the outside as high-frequency components.

[0043] Here, to determine whether or not galling has occurred based on the vibration frequency, either an abnormal state or a normal state can be used as the standard. In most cases, the presence or absence of galling can be determined based only on the abnormal state, but in exceptional cases, an example of which will be explained below, it is desirable to determine whether or not galling has occurred based on the normal state. Both the normal state and the abnormal state may also be used as the standard. An example of an exception is when a raw resin containing some kind of high-hardness piece or powder is used to impart high functionality. When molding using such a raw resin, even under normal plasticization conditions where galling is not occurring, the high-hardness piece or powder may aggregate into small lumps in the high-pressure environment between the inner circumferential surface 73I of the heating barrel 73 and the outer circumferential surface 72O of the screw flight 72. In this state, when the aggregates of high-hardness piece or powder slide against the inner circumferential surface 73I and the outer circumferential surface 72O, respectively, vibrations containing the expected high-frequency components may be generated. In such cases, simply determining whether or not galling has occurred based on whether or not the detected vibration contains high-frequency components in a predetermined frequency band may result in an erroneous determination that galling has occurred even when the condition is normal. In contrast, by determining whether or not galling has occurred based on the normal condition, even if the detected vibration contains high-frequency components, if those high-frequency components are also contained in normal vibrations, the erroneous determination of galling can be prevented.

[0044] As described above, in the embodiment, the occurrence of galling is estimated and determined based on the fact that the vibration in the abnormal state where galling occurs is significantly different from the vibration in the normal state where galling does not occur. There are at least two modes of the significant difference. The first is a state in which high frequency components that are not included in vibrations occurring under normal conditions are included. In other words, if vibrations including high frequency components HF can be detected in Figure 2, it can be determined that galling has occurred inside the heating barrel 73. The second is a mode in which high frequency components are included in vibrations that occur in a normal state, but the vibration level of these frequency components becomes high and apparent in an abnormal state. As described above, this embodiment utilizes the fact that the high-frequency vibration components and their vibration levels that are not apparent become apparent in vibrations that cause galling, and by detecting either or both of the high-frequency vibration components and the high vibration levels, determines whether galling has occurred.

[0045] [Effects of the embodiment] As described above, the control device 100 of this embodiment determines whether or not galling has occurred based on the frequency of vibrations generated by sliding between metals. Since vibrations generated by sliding between metals are not affected by the ambient temperature of the injection device 1, this embodiment makes it possible to determine with high accuracy whether or not galling has occurred, regardless of fluctuations in the environmental temperature.

[0046] In addition to the above, the configurations given in the above embodiments can be selected or changed as appropriate without departing from the spirit of the present invention.

[0047] [Consideration of periodic fluctuations: see Figures 4 and 5] Through extensive research, the inventors have found that the screw 71 exhibits a characteristic behavior as it rotates. It is preferable to utilize this behavior in determining galling. This behavior means that the screw 71 oscillates within the gap between the inner circumferential surface 73I of the heating barrel 73 and the outer circumferential surface 72O of the screw flight 72 of the screw 71. That is, as shown in Fig. 4, the axis 71C of the screw 71 moves up and down relative to the axis 73C of the heating barrel 73 at a period that is approximately twice the rotation period RP of the screw 71. Fig. 4(U) shows a state in which the axis 71C is raised, and Fig. 4(D) shows a state in which the axis 71C is lowered. This means that the inner circumferential surface 73I of the heating barrel 73 and the outer circumferential surface 72O of the screw flight 72 of the screw 71 come into contact with each other at a period that is approximately twice the rotation period RP of the screw 71.

[0048] Based on the above characteristic behavior, it is assumed that abnormal vibration due to galling occurs at a period approximately twice the rotation period RP of the screw 71, or increases at a period approximately twice the rotation period RP. This is illustrated in Figure 5. FIG. 5 compares a graph showing the frequency distribution of vibration with a graph showing the rotation phase of the screw 71. In addition to the rotation of the screw 71, the graph also shows the oscillation of the axis 71C of the screw 71 relative to the axis 73C as a dashed line. The low-frequency component LF is generated continuously during each or every rotation of the screw 71. In contrast, the high-frequency component HF is generated intermittently at a period approximately twice the rotation period of the screw 71. In an example of the rotation phase of the screw 71, the axis 73C of the screw 71 oscillates once during approximately two rotations of the screw 71. The high-frequency component HF is generated when the oscillation of the axis 73C causes galling debris MC adhering to the outer peripheral surface 72O of the screw flight 72 to locally collide with the inner peripheral surface 73I of the heating barrel 73. Therefore, by detecting abnormal vibrations due to galling in this embodiment at a period approximately twice the rotation period RP, false detection can be suppressed. The detection cycle is preferably RP·(2±1 / 4) times, and more preferably RP·(2±1 / 8) times.

[0049] [Consideration of changes in vibration level] Galling occurs when the inner circumferential surface 73I and the screw flight 72 slide against each other under conditions of excessively high surface pressure or relative speed, causing adhesion, and then the screw 71 is forcibly rotated to tear off the adhered portion. Furthermore, once galling occurs, galling debris adheres to the galling-causing area between the inner circumferential surface 73I and the screw flight 72, causing the sliding to become a localized overpressure state (a point-contact sliding state) at the corners of the galling debris, resulting in a gradual or rapid increase in galling. This means that the level of abnormal vibration caused by galling increases in response to the increase in galling. Conversely, once galling occurs, the degree of galling does not continuously decrease over a long period of time, so it is thought that the abnormal vibration indicating the degree of galling will not be significantly reduced. Furthermore, during the plasticization process under normal conditions, vibrations containing the expected high-frequency components may occur, but these vibrations occur repeatedly at the same steady level, so the vibrations containing the expected high-frequency components do not increase continuously. As described above, false detections of abnormal vibrations causing galling can be reduced by detecting vibrations that continuously increase during one plasticization process or vibrations that continuously increase over multiple plasticization processes. The term "continuous increase" here includes both intermittent and continuous increases and continuous increases.

[0050] [Consideration of opening and closing of raw material inlet] During molding operation, high torque is applied to the screw 71 to apply high shear forces to the resin inside the heating barrel 73, resulting in a high vibration level during the normal plasticization process. Therefore, the raw material inlet 74 is closed with the shutter 15, stopping the introduction of raw material into the screw 71 and emptying at least the base groove of the screw 71 to create a starvation state. This reduces the rotational torque, which is the screw's excitation force during plasticization, and lowers the vibration level of the low-frequency vibration LF, thereby facilitating detection of the high-frequency component HF. It is preferable to close the raw material inlet 74 with the shutter 15 as a prerequisite for rotating the screw 71 and monitoring for abnormal vibrations in the heating barrel 73. In other words, the presence or absence of abnormal vibrations is detected after the shutter 15 is detected by the open / close sensor 107. This is referred to as the vibration detection mode. By using the vibration detection mode, the vibration level of the low-frequency vibrations generated during normal plasticization is reduced, making it easier to detect the high-frequency component HF caused by galling. The raw material inlet 74 may not be completely closed by the shutter 15, but may be half-open or half-closed, or in an intermediate state between fully open and fully closed. Even an intermediate state between fully open and fully closed can reduce the amount of raw material that falls into the raw material inlet 74, so the groove of the screw 71 is not filled with raw material but is in a semi-starved state, reducing the rotational torque during visualization. This reduces the vibration level of the low-frequency vibration LF, making it relatively easy to detect the high-frequency component HF.

[0051] [Example of display on a display device: Figure 6] A preferred example of a display on the display device 103A is shown in Fig. 6. This example of a display is executed in, for example, a vibration detection mode. In Figure 6, an input area for inputting and setting the frequency (determination threshold: nnnn) used as the criterion for determining whether galling has occurred is displayed on the same screen, along with the frequency distribution in a normal state and the frequency distribution in an abnormal state of the frequency spectrum obtained by frequency analysis of the vibration detected by the vibration sensor 106. This makes it easy to distinguish and interpret the high-frequency frequencies generated or increased due to abnormal vibration from the vibration frequency in a normal state, and based on this interpretation result, the operator can easily select and input a predetermined high-frequency value. In this case, the vibration waveform that is determined to be abnormal vibration may be vibration generated with a period twice the screw rotation period.

[0052] It is difficult to define a single threshold value for the judgment criterion. This is because the frequency of vibrations generated in the heating barrel 73 depends on molding conditions such as the structure of the plasticizing device and the rotation speed of the screw. Therefore, the frequency used as the judgment criterion may be determined in advance through experiments or numerical analysis such as structural analysis. Alternatively, the frequency used as the judgment criterion may be set automatically or manually in the control device so as to exclude the frequency band detected by measuring vibrations at any or predetermined timing during normal production molding operation.

[0053] Furthermore, the control device according to the present invention may be incorporated into a control device that controls the operation of an injection molding machine or an extruder, or may be installed separately and be capable of communicating with the control device of the injection molding machine or the extruder. Furthermore, the control device according to the present invention can be installed in a newly installed injection molding machine or extrusion molding machine at the same time as the new machine is installed, and can also be newly installed in an existing injection molding machine or extrusion molding machine. [Explanation of symbols]

[0054] 1 Injection device 10 base 11 Foundation 12 Front support part 13 Input route 14 Hopper 15 Shutter 16 Rear support part 17 Containment Room 19 Guide rail 20 Drive unit 30 First drive unit 31 Electric motor 32 Output shaft 33 Output pulley 34 Transmission Belt 35 input shaft 37 Input pulley 50 Second drive unit 51A ball screw shaft 51B Ball screw nut 53 Input pulley 55 Electric Motor 56 Output shaft 57 Output pulley 58 Transmission Belt 59 Forward support 61 Rear support 63 Connectors 70 Injection part 71 Screw 71A main body 71B screw shaft 71C Axial center 72 Screw Flight 72O outer surface 73 Heating cylinder 73C Axial center 73I Inner surface 74 Raw material input port 75 Heating cylinder head 77 Injection Nozzle 100 control device 101 Judgment section 103 Display section 103A Display device 103B Indicator light 103C Speaker 105 Detection unit 106A, 106B, 106C, 106D Vibration Sensor 107 Open / Close Recognition Sensor HF High frequency component LF Low frequency component F forward R rear H Vertical direction W width direction L Longitudinal direction MC galling fragments MP molten resin PP resin pellets RP screw rotation period RP rotation period

Claims

1. A control device for determining whether a screw has galled against a heating barrel in a molding machine for extrusion molding or injection molding, the molding machine including a heating barrel and a screw inserted into the heating barrel, one or more vibration detection units provided at any location of the molding machine; a determination unit that determines whether or not there is galling based on vibration information detected by the vibration detection unit, Control device.

2. In the determination unit, The detected vibration frequency obtained from the vibration information is The first reference vibration frequency is predetermined as a frequency that does not occur in a normal state where no galling occurs, or The galling is determined to occur when a predetermined second reference vibration frequency is included as a frequency at which a vibration level increases in an abnormal state where the galling occurs compared to the normal state. The control device according to claim 1 .

3. The first reference vibration frequency and the second reference vibration frequency are defined as determination thresholds equal to or greater than a predetermined frequency. The control device according to claim 2 .

4. In the determination unit, The galling is determined based on vibrations occurring at intervals of (2±1 / 4) times the rotation period of the screw. The control device according to claim 1 .

5. In the determination unit, The galling is determined by continuously increasing vibration. The control device according to claim 1 .

6. The vibration detection unit The vibration information is detected at a body portion of the heating barrel or at a rear end side of the heating barrel. The control device according to claim 1 .

7. The vibration detection unit The vibration information is detected in a member fixed to a body portion of the heating barrel or in a support member that fixes and supports the heating barrel. The control device according to claim 1 .

8. The determination unit The determination of galling is performed when an inlet for a raw material to be molded is in a closed state. The control device according to claim 1 .

9. an input area for the judgment threshold; a waveform of a normal state of a frequency spectrum obtained by frequency analysis of the vibration information; a display device capable of displaying on the same screen a waveform of an abnormal state of a frequency spectrum obtained by frequency analysis of the vibration information, The control device according to claim 3 .

10. A method for determining whether a screw in a heating barrel is galling in a molding machine for extrusion molding or injection molding, the molding machine including a heating barrel and a screw inserted into the heating barrel, comprising: a first step of detecting vibration information at any part of the molding machine; a second step of determining the galling based on the vibration information. How to determine galling.

11. A molding machine for extrusion molding or injection molding, comprising a heating barrel and a screw inserted into the heating barrel, A control device according to any one of claims 1 to 9, Molding machine.

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