Servo control device, spindle failure detection method using servo control device, and non-transitory computer readable medium encoded with computer program

Patent metadata

Field	Value
Publication number	US-10493576-B2
Application number	US-201715671576-A
Country	US
Kind code	B2
Filing date	Aug 8, 2017
Priority date	Aug 9, 2016
Publication date	Dec 3, 2019
Grant date	Dec 3, 2019

Abstract

To provide an arrangement capable of detecting spindle failure in a machine tool using an existing servo control device, without providing separate external sensors, a failure analysis device or the like. A servo control device ( 22 ), which detects failure of a spindle of a machine tool including the spindle, a feed shaft, and a positioning servomotor that is installed to the feed shaft and is for deciding the position of the spindle, includes: a feedback acquisition unit ( 222 ) that acquires a feedback signal of the positioning servomotor; and an analysis/detection unit 226 that analyzes the feedback signal acquired to detect failure of the spindle.

First claim

What is claimed is:

1. A servo control device that detects failure of a spindle in a machine tool including the spindle, a feed shaft, and a positioning servomotor that is installed to the feed shaft and is for deciding a position of the spindle, the servo control device comprising:
a feedback acquisition part that acquires a feedback signal of the positioning servomotor; and
an analysis/detection unit that analyzes the feedback signal acquired to detect failure of the spindle,
wherein the analysis/detection unit conducts Fourier transformation on the feedback signal to obtain a spectrum of a predetermined frequency range, and determines that failure has occurred in the spindle in a case of a signal intensity of the spectrum of the predetermined frequency range exceeding a predetermined first threshold,
the predetermined frequency range is adjusted according to the machine tool, contents of work performed by the machine tool, characteristic of the servomotor, and frequency of vibration occurring in the case of the spindle failure, and
the predetermined first threshold is adjusted according to the machine tool, contents of work performed by the machine tool, and characteristic of the servomotor, and
wherein the analysis/detection unit analyzes the feedback signal based on an operating state of the positioning servomotor, and determines a timing for detecting a failure of the spindle that corresponds to damage of a bearing of the spindle.

2. The servo control device according to claim 1 , wherein the feedback signal is at least one of any type of signal among an electrical current, velocity and position of the positioning servomotor.

3. The servo control device according to claim 1 , further comprising a notification unit that externally notifies of failure of the spindle detected by the analysis/detection unit.

4. The servo control device according to claim 1 , further comprising a notification unit that externally outputs a failure detection signal, in a case of the analysis/detection unit detecting failure of the spindle.

5. The servo control device according to claim 1 , further comprising a retracting unit that outputs a command causing the spindle to retract from a workpiece, in a case of the analysis/detection unit detecting failure of the spindle.

6. A method for detecting failure of a spindle of a machine tool including the spindle, a feed shaft, and a positioning servomotor that is installed to the feed shaft and is for deciding a position of the spindle, the method comprising the steps of:
acquiring a feedback signal of the positioning servomotor; and
analyzing the feedback signal thus acquired to detect failure of the spindle,
wherein, in the analyzing of the feedback signal, Fourier transformation is conducted on the feedback signal to obtain a spectrum of a predetermined frequency range, and it is determined that the failure has occurred in the spindle in a case of a signal intensity of the spectrum of the predetermined frequency range exceeding a predetermined first threshold,
the predetermined frequency range is adjusted according to the machine tool, contents of work performed by the machine tool, characteristic of the servomotor, and frequency of vibration occurring in the case of spindle failure, and
the predetermined first threshold is adjusted according to the machine tool, contents of work performed by the machine tool, and characteristic of the servomotor, and
wherein, in the analyzing of the feedback signal, the feedback signal is analyzed based on an operating state of the positioning servomotor, and a timing for detecting a failure of the spindle is determined that corresponds to damage of a bearing of the spindle.

7. A non-transitory computer readable medium encoded with a computer program enabling a computer to operate as a servo control device that detects failure of a spindle of a machine tool including the spindle, a feed shaft, and a positioning servomotor that is installed to the feed shaft and is for deciding a position of the spindle, wherein the computer program causes the computer to execute:
feedback acquisition processing of acquiring a feedback signal of the positioning servomotor; and
analysis/detection processing of analyzing the feedback signal thus acquired to detect failure of the spindle,
wherein, in the analysis/detection processing, Fourier transformation is conducted on the feedback signal to obtain a spectrum of a predetermined frequency range, and it is determined that the failure has occurred in the spindle in a case of a signal intensity of the spectrum of the predetermined frequency range exceeding a predetermined first threshold,
the predetermined frequency range is adjusted according to the machine tool, contents of work performed by the machine tool, characteristic of the servomotor, and frequency of vibration occurring in the case of spindle failure, and
the predetermined first threshold is adjusted according to the machine tool, contents of work performed by the machine tool, and characteristic of the servomotor, and
wherein, in the analysis/detection processing, the feedback signal is analyzed based on an operating state of the positioning servomotor, and a timing for detecting failure of the spindle is determined that corresponds to damage of a bearing of the spindle.

Assignees

• Fanuc Corp

Inventors

• Sonoda Naoto
• Oho Yuusaku

Classifications

• B23Q17/007

  for managing machine functions not concerning the tool · CPC title

• B23Q5/58 Primary

  Safety devices {(protecting the operator B23Q11/0089)} · CPC title

• B23Q17/09

  for indicating or measuring cutting pressure or {for determining} cutting-tool condition, e.g. cutting ability, load on tool (arrangements preventing overload of tools B23Q11/04; devices for indicating failure of drills during boring B23B49/00) · CPC title

• G05B2219/37245

  Breakage tool, failure · CPC title

• G05B19/4065 Primary

  Monitoring tool breakage, life or condition · CPC title