Ball screw maintenance management system and ball screw maintenance management method

Abstract

The ball screw maintenance management system according to the present embodiment includes a ball screw, a motor that drives the ball screw, a vibration sensor that detects vibration of the ball screw, and a first determination unit that determines whether the ball screw is in a worn state using vibration information in a constant-speed rotation region of the motor among vibration information of the ball screw acquired from the vibration sensor.

Description

Technical Field

[0001] This invention relates to a ball screw maintenance management system and a ball screw maintenance management method. Background Technology

[0002] A ball screw is a drive unit that moves a nut mounted on a ball screw along the screw shaft by applying rotational motion. Ball screws are used as basic components in various processing machines, such as injection molding machines.

[0003] If a ball screw, a fundamental component, fails, it can potentially halt the production line. Furthermore, the manufacture of ball screws used in large processing machines such as jet molding machines takes time; therefore, it is necessary to predict ball screw replacement times and prepare spare parts in advance.

[0004] Japanese Patent Application Publication No. 2013-257014 discloses a technology relating to an abnormality detection device for a ball screw assembly. This abnormality detection device uses a vibration sensor installed on the nut of the ball screw to detect vibration, extracts vibration data of the abnormality detection frequency band of the ball screw from the vibration data, and detects abnormalities by comparing it with normal data. Summary of the Invention

[0005] However, the vibration sensor of the nut installed on the ball screw is susceptible to interference. Therefore, in the method disclosed in Japanese Patent Application Publication No. 2013-257014, noise generated by interference may lead to incorrect judgment and make it impossible to make a correct judgment.

[0006] On the other hand, in the method of detecting the damage condition of the ball screw by measuring the current value of the motor that rotates the ball screw, there is a problem that the damage condition of the ball screw cannot be detected unless it is a damage condition that requires emergency replacement.

[0007] The present invention is proposed to solve the above-mentioned problems, and its purpose is to provide a ball screw maintenance management system and a ball screw maintenance management method that can manage the maintenance period of ball screws.

[0008] One aspect of the present invention relates to a ball screw maintenance management system comprising:

[0009] Ball screw;

[0010] The electric motor that drives the ball screw;

[0011] A vibration sensor for detecting the vibration of the ball screw; and

[0012] The first determination unit uses the vibration information of the ball screw in the constant speed rotation region of the motor from the vibration information of the ball screw obtained from the vibration sensor to determine whether the ball screw is in a worn state.

[0013] One aspect of the present invention relates to a ball screw maintenance management method that uses a computer to manage the maintenance period of the ball screw.

[0014] In this method,

[0015] Vibration information of the ball screw is obtained from a vibration sensor.

[0016] Using the vibration information of the ball screw obtained from the vibration information of the ball screw, specifically the vibration information in the constant-speed rotation region of the motor driving the ball screw, it is determined whether the ball screw is in a worn state.

[0017] When the motor rotates at a constant speed, noise from vibrations caused by interference is less likely to occur compared to when the motor is accelerating or decelerating. One aspect of the ball screw maintenance management system of the present invention uses vibration information from the constant-speed rotation region of the motor, obtained from vibration sensors, to determine whether the ball screw is in a worn state. That is, in one aspect of the ball screw maintenance management system of the present invention, by using vibration information from the constant-speed rotation of the motor, the influence of interference can be suppressed, minute vibrations can be detected, and the wear state of the ball screw, especially the initial stage of wear, can be accurately and early detected. According to one aspect of the ball screw maintenance management system of the present invention, by determining the wear state of the ball screw before damage, the maintenance period of the ball screw can be managed in a way that maintains it in a normal state without malfunctions or defects.

[0018] According to the present invention, a ball screw maintenance management system and a ball screw maintenance management method are provided that can manage the maintenance period of a ball screw.

[0019] The above and other objects, features and advantages of this disclosure will become more fully understood from the following detailed description and the accompanying drawings, which are illustrated by way of example only, and these should not be considered as limiting the disclosure. Attached Figure Description

[0020] Figure 1 This is a diagram showing the configuration of the ball screw maintenance management system according to the first embodiment.

[0021] Figure 2 This is a flowchart illustrating the operation of the ball screw maintenance management system according to the first embodiment.

[0022] Figure 3 This is a diagram illustrating an example of the hardware configuration of the server in the ball screw maintenance management system according to the first embodiment. Detailed Implementation

[0023] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments. In addition, for clarity, the following description and drawings have been appropriately simplified.

[0024] <First Implementation>

[0025] <Composition of the Maintenance and Management System>

[0026] Reference Figure 1 This describes the configuration of the ball screw maintenance management system 100 according to the first embodiment. Figure 1 This is a diagram showing the configuration of the ball screw maintenance management system 100. Furthermore, Figure 1 The right-handed coordinate system shown is an orthogonal xyz coordinate system used to illustrate the positional relationships of the components of a device with a ball screw 1 (hereinafter also referred to as a ball screw device). Typically, the positive z-axis is vertically upward, and the xy plane is horizontal.

[0027] The ball screw maintenance management system 100 manages a ball screw assembly comprising a ball screw 1, bearings 2 and 3, a motor 4, a vibration sensor 5, a current sensor 6, a drive rod 7, a coupling 8, and a base frame 9. Additionally, the ball screw assembly may include other components required for operation.

[0028] The control console 20 includes amplifier 21, amplifier 22, recorder 23, and recording medium 24. Vibration sensor 5 and current sensor 6 of the ball screw assembly are connected to amplifier 21 and amplifier 22 of the control console 20, respectively. Furthermore, the control console 20 may also include other components required for operation.

[0029] Server 30 includes a first determination unit 31 and a second determination unit 32. The first determination unit 31 is connected to the vibration sensor 5 via a recorder 23 and an amplifier 21. The second determination unit 32 is connected to the current sensor 6 via a recorder 23 and an amplifier 22. Furthermore, server 30 may also include other components necessary for operation. Additionally, server 30 may be connected to an external network (not shown).

[0030] The following is a detailed description of the configuration of the ball screw device, control console 20, and server 30 of the ball screw maintenance management system 100 according to the first embodiment.

[0031] The ball screw 1 has a ball screw shaft 11 and a movable nut 12 that moves along the ball screw shaft 11. Figure 1 In this configuration, the ball screw shaft 11 extends along the x-axis. The movable nut 12 is screwed onto the ball screw shaft 11. If the ball screw shaft 11 rotates, the nut 12 moves along the ball screw shaft 11 towards the positive and negative x-axis directions. The movable area of ​​the movable nut 12 is located between the bearings 2 and 3 at both ends of the ball screw shaft 11.

[0032] Bearings 2 and 3 support the ball screw shaft 11. Figure 1 As shown, bearing 2 is a bearing located at the end of the ball screw shaft 11 on the motor 4 side (negative x-axis side). Bearing 2 is fixed to the bottom frame 9, and the ball screw shaft 11 is embedded in the through hole of bearing 2.

[0033] Bearing 3 is a bearing located at the end of the drive rod 7 (positive x-axis side). Bearing 3 is fixed to the bottom frame 9, and the ball screw shaft 11 is embedded in the through hole of bearing 3.

[0034] That is, the ball screw shaft 11 is rotatably supported on the bottom frame 9 via bearings 2 and bearings 3 located at both ends.

[0035] Motor 4 is the motor that drives ball screw 1. Specifically, motor 4 rotates to drive ball screw shaft 11, causing movable nut 12 to move along ball screw shaft 11. Motor 4 is, for example, a servo motor. Motor 4 is connected to ball screw 1 via coupling 8. The rotational motion of motor 4 is transmitted to ball screw 1 via coupling 8. If the rotational direction of motor 4 is changed, the movement direction of movable nut 12 is changed to the positive or negative x-axis direction.

[0036] Vibration sensor 5 is a sensor for detecting the vibration of ball screw 1. Vibration sensor 5 can be installed at any position in the ball screw assembly. To improve the accuracy of vibration detection, it is preferable that vibration sensor 5 be installed on the movable nut 12, bearing 2, or bearing 3, which is directly connected to ball screw 1. Furthermore, to suppress the influence of interference, it is preferable that vibration sensor 5 be installed on bearing 3, which is furthest away from motor 4. Figure 1 In this example, vibration sensor 5 is mounted on bearing 3.

[0037] Vibration sensor 5 is connected to amplifier 21 of console 20. Vibration detected by vibration sensor 5 is amplified and filtered by amplifier 21, recorded by recorder 23 on recording medium 24, and acquired by first determination unit 31 of server 30.

[0038] Current sensor 6 is used to detect the current value of motor 4. It is worth noting that... Figure 1In this configuration, the current sensor 6 is grounded to the motor 4, but it can be placed at any location that can detect the current value of the motor 4, such as the connection line between the control console 20 and the motor 4, or inside the control console 20.

[0039] The current sensor 6 is connected to the amplifier 22 of the control console 20. The current value of the motor 4 detected by the current sensor 6 is amplified and filtered by the amplifier 22, recorded by the recorder 23 on the recording medium 24, and acquired by the second determination unit 32 of the server 30.

[0040] The drive rod 7 is a component capable of positioning an object in the xy-plane. The shape of the drive rod 7 can be arbitrary. As the drive rod 7, its negative x-axis end is fixed to the positive x-axis end face of the movable nut 12 via a connecting part 10. Alternatively, the drive rod 7 and the movable nut 12 can be fixed together via multiple connecting parts 10. It is worth noting that the method of fixing the drive rod 7 and the movable nut 12 is not limited to this; it is acceptable as long as both can be fixed in a manner that allows them to move as a single unit. Figure 1 In order to distinguish it from the ball screw shaft 11, the connection 10 between the drive rod 7 and the movable nut 12 is shown in diagonal lines. In addition, the drive rod 7 and the connection 10 are configured in a way that does not interfere with the bearing 3.

[0041] Since the drive rod 7 is fixed to the movable nut 12, if the motor 4 drives the ball screw 1, the drive rod 7 will also move in the same direction as the movable nut 12. That is, when the movable nut 12 moves along the positive x-axis, the drive rod 7 will also move accordingly along the positive x-axis. Similarly, when the movable nut 12 moves along the negative x-axis, the drive rod 7 will also move accordingly along the negative x-axis. The movable nut 12 and the drive rod 7 move the same distance as a single unit.

[0042] The bottom frame 9 is a frame that supports bearings 2 and 3, and motor 4. The shape of the bottom frame 9 only needs to be able to support bearings 2, 3, and 4; for example, it can be a plate-like component parallel to the xy-plane. Bearings 2, 3, and 4 are mounted and fixed on the bottom frame 9. The bottom frame 9 can also be connected to bearings 2, 3, and 4 via other connecting components. It is worth noting that the drive rod 7 is connected to the bottom frame 9, but... Figure 1 The connection between the two is omitted.

[0043] The control console 20 includes amplifier 21, amplifier 22, recorder 23, and recording medium 24. Amplifier 21 is connected to vibration sensor 5 and amplifies and filters the vibrations obtained from vibration sensor 5. Amplifier 22 is connected to current sensor 6 and amplifies and filters the current value of motor 4 obtained from current sensor 6.

[0044] The recorder 23, connected to amplifiers 21 and 22, is a device for storing data (vibration information and current value information) measured and collected by the vibration sensor 5 and the current sensor 6. The recording medium 24 is the medium for recording the data from the recorder 23. It is worth noting that the recording medium 24 can also be connected to the server 30. For example, the first determination unit 31 can also obtain vibration information from the recording medium 24 to make a determination. Additionally, the second determination unit can also obtain current value information from the recording medium 24 to make a determination.

[0045] Server 30 includes a first determination unit 31 and a second determination unit 32. Server 30 is, for example, a computer device that performs the processing of the first determination unit 31 and the second determination unit 32. It is worth noting that the first determination unit 31 and the second determination unit 32 may also be configured within console 20. In addition, the processing involved in the first determination unit 31 and the second determination unit 32 may also be performed by other computer devices connected to an external network, and the processing of the first determination unit 31 and the processing of the second determination unit 32 may also be performed by different computer devices.

[0046] The first determination unit 31 uses the vibration information of the ball screw 1 obtained from the vibration sensor 5, specifically the vibration information within the constant-speed rotation region of the motor 4, to determine whether the ball screw 1 is in a worn state. The vibration of the ball screw 1 increases as wear develops. For example, the first determination unit 31 can perform frequency analysis on the vibration information of the ball screw 1 obtained from the vibration sensor 5, and determine that the ball screw 1 is in a worn state when the vibration in the constant-speed rotation region of the motor 4 is above a threshold. It is worth noting that when the rotational motion of the motor 4 is in the constant-speed rotation region, the movable nut 12 moves at a constant speed on the ball screw shaft 11.

[0047] The second determination unit 32 uses the current value of the motor 4 obtained from the current sensor 6 to determine whether the ball screw 1 is in a damaged state. The load involved in the motor 4 increases as the ball screw 1 wears out. That is, the current value of the motor 4 increases. For example, the second determination unit 32 may determine that the ball screw 1 is in a damaged state when the current value of the motor 4 obtained from the current sensor 6 is above a threshold. In addition, from the point of view to improve the accuracy of the determination, it is preferable that the second determination unit 32 uses the current value of the motor 4 in the constant speed rotation region of the motor 4 obtained from the current sensor 6 to determine whether the ball screw 1 is in a damaged state.

[0048] The ball screw maintenance management system 100 of this embodiment, by utilizing vibration information in the constant-speed rotation region of the electric motor 4, can suppress the influence of interference, detect minute vibrations, and accurately and early detect the wear condition of the ball screw 1, especially the initial stage of wear. The ball screw maintenance management system 100 can manage the preparation period for the prior preparation and preparation of spare ball screws by determining the wear condition of the ball screw 1. In other words, the ball screw maintenance management system 100 can manage the maintenance period of the ball screw 1.

[0049] Furthermore, the ball screw maintenance management system 100 can use the current value of the motor 4 obtained from the current sensor 6 to determine whether the ball screw 1 is damaged. Therefore, the ball screw maintenance management system 100 can manage the replacement period of the ball screw 1 by detecting the period when the damage to the ball screw 1 begins to load the motor 4. That is, the ball screw maintenance management system 100 can not only manage the preparation period but also manage the maintenance period of the ball screw 1 in accordance with its replacement period. According to the ball screw maintenance management system 100, the high-value ball screw 1, which is still usable up to this point, can be used until its lifespan limit.

[0050] It is worth noting that the ball screw maintenance management system 100 may also include a notification unit (not shown) that notifies the user of the ball screw maintenance management system 100 of the determination results of the first determination unit 31 or the second determination unit 32. This allows the user of the ball screw maintenance management system 100 to be notified of the determination results of the first determination unit 31 or the second determination unit 32.

[0051] The notification unit can be located, for example, at the console 20, the server 30, or a terminal (not shown) connected to the server 30 via a network. For example, the notification unit can output an alarm corresponding to the determination result of the first determination unit 31 or the second determination unit 32. Additionally, the notification unit can send a message indicating the determination result to the console 20, the server 30, or the terminal. For example, if the first determination unit 31 determines that the ball screw 1 is in a worn state, the notification unit can notify that the ball screw 1 is in a preparation period. Similarly, if the second determination unit 32 determines that the ball screw 1 is in a damaged state, the notification unit can notify that the ball screw 1 is in a replacement period.

[0052] Therefore, users of the ball screw maintenance management system 100 can easily grasp the maintenance period of the ball screw 1.

[0053] Furthermore, the notification department can set different alarms for the judgment results of the first judgment unit 31 and the second judgment unit 32. Therefore, users of the ball screw maintenance management system 100 can easily determine the preparation and replacement periods for the ball screw based on the different alarms.

[0054] <Maintenance and Management Methods>

[0055] Next, use Figure 2 This describes the ball screw maintenance and management method involved in the first embodiment. Figure 2 This is a flowchart illustrating the operation of the ball screw maintenance management system 100 according to the first embodiment.

[0056] Power is supplied to devices that require electricity, such as motor 4, vibration sensor 5, and current sensor 6 (step S1). Then, vibration is measured by vibration sensor 5 and current value of motor 4 is measured by current sensor 6 (step S2).

[0057] After the vibration and current value measurements begin, a rotation command is sent to the motor 4 from a motor control device (not shown) on the control console 20. The motor 4 begins to rotate based on the rotation start command (step S3). After the rotation of the motor 4 begins, the vibration of the ball screw 1 is detected by the vibration sensor 5, and the current value of the motor 4 is detected by the current sensor 6.

[0058] The motor 4 accelerates its rotation based on an acceleration command (step S4). While the motor 4 is in the acceleration rotation region, the movable nut 12 and the drive rod 7 fixed to the movable nut 12 move at an accelerated speed. Then, the motor 4 rotates at a constant speed based on a constant speed command (step S5). While the motor 4 is in the constant speed rotation region, the movable nut 12 and the drive rod 7 fixed to the movable nut 12 move at a constant speed.

[0059] The first determination unit 31 uses the vibration information of the ball screw 1 obtained from the vibration sensor 5, specifically the vibration information in the constant speed rotation area of ​​the motor 4, to determine whether the ball screw 1 is in a worn state (step S6).

[0060] If the vibration of ball screw 1 exceeds a threshold (step S6: Yes), the first determination unit 31 determines that ball screw 1 is in a worn state. In this case, the notification unit outputs an alarm indicating that ball screw 1 is in a preparation period (step S7). On the other hand, if the vibration of ball screw 1 does not exceed the threshold (step S6: No), the first determination unit 31 determines that ball screw 1 is not in a worn state. In this case, the first determination unit 31 continues to make determinations based on vibration.

[0061] Alternatively, the ball screw maintenance management system 100 can automatically perform preparation and order processing for the ball screw 1 when it determines that the ball screw 1 is in a worn state. For example, an order management department (not shown) can be set up in the server 30. When the first determination unit 31 determines that the ball screw 1 is in a worn state, the order management department automatically performs preparation and order processing for the ball screw 1. Specifically, the order management department can send an order request message for the ball screw 1, which is the object of maintenance, to the information processing device of a pre-registered supplier. In addition, the order management department can manage the delivery status, arrival date, etc. of ball screws 1 with completed orders. As a result, the ball screw maintenance management system 100 can reduce the management work involved in the maintenance of the ball screw 1.

[0062] The second determination unit 32 uses the current value of the motor 4 obtained from the current sensor 6 to determine whether the ball screw 1 is damaged. Figure 2 As shown, from the point of improving the accuracy of the determination, it is preferable that the second determination unit 32 uses the current value of the motor 4 in the constant speed motion region of the motor 4 obtained from the current sensor 6 to determine whether the ball screw 1 is in a damaged state (step S8).

[0063] If the current value of motor 4 is above the threshold (step S8: Yes), the second determination unit 32 determines that ball screw 1 is damaged. In this case, the notification unit outputs an alarm indicating that ball screw 1 is due for replacement (step S9). On the other hand, if the current value of motor 4 is not above the threshold (step S8: No), the second determination unit 32 determines that ball screw 1 is not damaged. In this case, the second determination unit 32 continues to make determinations based on the current value.

[0064] The motor 4 decelerates its rotation based on a deceleration command (step S10). When the motor 4 is in the deceleration rotation region, the movable nut 12 and the drive rod 7 fixed to the movable nut 12 decelerate their movement. Then, the motor 4 stops rotating based on a rotation stop command (step S11). When the motor 4 stops rotating, the movable nut 12 and the drive rod 7 fixed to the movable nut 12 also stop moving.

[0065] Steps S1 to S11 can also be repeatedly executed each time the ball screw device operates. Therefore, the ball screw maintenance management system 100 according to this embodiment can continue to determine whether the ball screw 1 is in a worn state and whether it is in a damaged state.

[0066] As described above, the ball screw maintenance management system 100 of this embodiment can manage the preparation period of the ball screw 1 by determining the wear condition of the vibration sensor 5. Therefore, it is no longer necessary to prepare spare parts in advance to deal with ball screw 1 failures, reducing the need for spare parts for ball screw 1. Furthermore, it can prevent production line shutdowns due to ball screw 1 failures. In addition, the ball screw maintenance management system 100 can manage the replacement period of the ball screw 1 by determining the damage condition of the current sensor 6. According to the ball screw maintenance management system 100 of this embodiment, the maintenance period, including the preparation period and replacement period of the ball screw 1, can be managed.

[0067] use Figure 3 This section describes an example of the hardware configuration of the server 30 in the ball screw maintenance management system 100 according to the first embodiment. It is worth noting that the console 20 may also have the same hardware configuration as the server 30. Figure 3 In this configuration, server 30 includes processor 101 and memory 102. Processor 101 may be, for example, a microprocessor, an MPU (Micro Processing Unit), or a CPU (Central Processing Unit). Processor 101 may contain multiple processors. Memory 102 consists of a combination of volatile and non-volatile memory. Memory 102 may also include storage units configured separately from processor 101. In this case, processor 101 can access memory 102 via an input / output interface (not shown).

[0068] Furthermore, the devices in the above embodiments can be composed of hardware or software, or both; they can be composed of one piece of hardware or software, or multiple pieces of hardware or software. The functions (processing) of the devices in the above embodiments can also be implemented by a computer. For example, a program for performing the actions in the embodiments can be stored in memory 102, and the functions can be implemented by executing the program stored in memory 102 by processor 101.

[0069] The program contains a set of commands (or software code) for causing the computer to perform one or more functions described in the implementation when read by the computer. The program may be stored on a non-transitory computer-readable medium or a physical storage medium. By way of example, and not limitation, computer-readable media or physical storage media include random access memory (RAM), read-only memory (ROM), flash memory, solid-state drives (SSDs) or other storage technologies, CD-ROMs, digital versatile optical discs (DVDs), Blu-ray discs or other optical disc storage, cassette tapes, magnetic tapes, disk drives, or other magnetic storage devices. The program may also be transmitted via a temporary computer-readable medium or a communication medium. By way of example, and not limitation, temporary computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagation signals.

[0070] Based on the above disclosure, it is obvious that embodiments of the present invention can be modified in various ways. These modifications are also included within the spirit and scope of the present invention, and those skilled in the art will recognize that all modifications are included within the scope of protection claimed in the claims.

Claims

1. A ball screw maintenance management system, comprising: A ball screw, having a ball screw shaft and a movable nut that moves along the ball screw shaft; The electric motor that drives the ball screw; A vibration sensor for detecting the vibration of the ball screw; The first determination unit uses the vibration information of the ball screw in the constant speed rotation area of ​​the motor from the vibration information of the ball screw obtained from the vibration sensor to determine whether the ball screw is in a worn state. A current sensor that detects the current value of the motor; as well as The second determination unit uses the current value of the motor obtained from the current sensor to determine whether the ball screw is damaged. The ball screw maintenance management system also includes a first bearing and a second bearing to support the ball screw shaft. The first bearing and the second bearing are disposed at both ends of the ball screw shaft. The second bearing is located at the end of the ball screw shaft furthest from the motor, such that the ball screw shaft is embedded in the through hole of the second bearing. The vibration sensor is mounted on the second bearing. The ball screw maintenance management system further includes: a notification unit, which notifies the determination results of the first determination unit or the second determination unit. If the first determination unit determines that the ball screw is in a worn state, the notification unit reports that the ball screw is in a preparation period. If the second determination unit determines that the ball screw is in a damaged state, the notification unit reports that the ball screw is in a replacement period.

2. The ball screw maintenance management system according to claim 1, wherein, The second determination unit uses the current value of the motor in the constant speed rotation region of the motor obtained from the current sensor to determine whether the ball screw is damaged.

3. The ball screw maintenance management system according to claim 1 or 2, The notification unit sets the alarms under the judgment results of the first judgment unit and the alarms under the judgment results of the second judgment unit to be different alarms.

4. A ball screw maintenance and management method, which is a ball screw maintenance and management method that uses a computer to manage the maintenance period of the ball screw. In this method, Vibration information of the ball screw is obtained from a vibration sensor. By using the vibration information of the ball screw obtained from the constant-speed rotation region of the motor driving the ball screw, it is determined whether the ball screw is in a worn state. The current value of the motor is obtained from the current sensor. Using the obtained current value of the motor, it is determined whether the ball screw is damaged. The ball screw has a ball screw shaft and a movable nut that moves along the ball screw shaft. The ball screw shaft is further provided with a first bearing and a second bearing at both ends to support the ball screw shaft. The second bearing is located at the end of the ball screw shaft furthest from the motor, such that the ball screw shaft is embedded in the through hole of the second bearing. The vibration sensor is mounted on the second bearing. The results of determining whether the ball screw is in a worn state using the vibration information or the results of determining whether the ball screw is in a damaged state using the current value of the motor will be reported. If the ball screw is determined to be in a worn state, the system will notify that the ball screw is in a preparation period; if the ball screw is determined to be in a damaged state, the system will notify that the ball screw is in a replacement period.

5. The ball screw maintenance and management method according to claim 4, wherein, The current value of the motor in the constant speed rotation region obtained from the current sensor is used to determine whether the ball screw is damaged.

6. The ball screw maintenance and management method according to claim 4 or 5, wherein, The alarms based on the determination that the ball screw is in a worn state using vibration information and the alarms based on the determination that the ball screw is in a damaged state using the current value of the motor are set as different alarms.

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