Machine tool and vibration diagnosis support method

Patent metadata

Field	Value
Publication number	US-11073497-B2
Application number	US-201916676486-A
Country	US
Kind code	B2
Filing date	Nov 7, 2019
Priority date	Nov 13, 2018
Publication date	Jul 27, 2021
Grant date	Jul 27, 2021

Abstract

A machine tool includes: a first calculator configured to calculate a first frequency characteristic based on a first oscillation signal and a measurement signal of a physical quantity measured by a measurement unit when the drive shaft of a servo motor swings in accordance with the first oscillation signal; and a second calculator configured to calculate a second frequency characteristic based on a second oscillation signal and a measurement signal of the physical quantity measured by the measurement unit when the drive shaft of the servo motor swings in accordance with the second oscillation signal.

First claim

What is claimed is:

1. A machine tool, comprising:
a drive system ranging from a servo motor to a driven target driven by drive force of the servo motor;
a first signal sending unit configured to send a first oscillation signal, the first oscillation signal being configured to cause a drive shaft of the servo motor to swing periodically and having an oscillation frequency that becomes higher with time;
a second signal sending unit configured to send a second oscillation signal, the second oscillation signal being configured to cause the drive shaft to swing periodically and having an oscillation frequency that becomes lower with time;
a measurement unit configured to measure a physical quantity representing a state of the machine tool;
a first calculator configured to calculate a first frequency characteristic based on a measurement signal of the physical quantity measured by the measurement unit when the drive shaft swings in accordance with the first oscillation signal, and the first oscillation signal; and
a second calculator configured to calculate a second frequency characteristic based on a measurement signal of the physical quantity measured by the measurement unit when the drive shaft swings in accordance with the second oscillation signal, and the second oscillation signal.

2. The machine tool according to claim 1 , further comprising a display controller configured to cause a display device to display the first frequency characteristic and the second frequency characteristic in a comparative manner.

3. The machine tool according to claim 2 , wherein the display controller is configured to cause the display device to display, in a distinctive manner, a first resonance point appearing in the first frequency characteristic and a second resonance point appearing in the second frequency characteristic corresponding to the first resonance point when a deviation between the first resonance point and the second resonance point is equal to or greater than a predetermined threshold.

4. The machine tool according to claim 2 , wherein the display controller is configured to cause the display device to display a comment relating to vibration in accordance with a deviation between a first resonance point appearing in the first frequency characteristic and a second resonance point appearing in the second frequency characteristic corresponding to the first resonance point.

5. The machine tool according to claim 1 , further comprising a parameter setting unit configured to set at least one signal parameter selected among a frequency band within which the oscillation frequency is changed for each of the first oscillation signal and the second oscillation signal, number of steps by which the oscillation frequency is changed within the frequency band, and an amplitude of each of the first oscillation signal and the second oscillation signal, based on operation performed by an operator, wherein
the first signal sending unit is configured to send the first oscillation signal so as to satisfy the signal parameter set by the parameter setting unit, and the second signal sending unit is configured to send the second oscillation signal so as to satisfy the signal parameter set by the parameter setting unit.

6. The machine tool according to claim 5 , wherein the parameter setting unit is configured to set up the frequency band so that the frequency band contains a frequency input by the operator and is narrower than a preset initial frequency band, and set up the number of steps that is greater than a preset initial number.

7. The machine tool according to claim 1 , further comprising:
a vibration factor estimating unit configured to estimate whether or not a vibration includes an abnormality of the machine tool, based on a deviation between a first resonance point appearing in the first frequency characteristic and a second resonance point appearing in the second frequency characteristic corresponding to the first resonance point; and
a notification unit configured to notify an estimation result of the vibration factor estimating unit.

8. The machine tool according to claim 7 , wherein the vibration factor estimating unit is configured to estimate that there is a high possibility that a vibration including an abnormality of the machine tool is occurring when the deviation is equal to or greater than a predetermined threshold and estimate that there is a low possibility that a vibration including an abnormality of the machine tool is occurring when the deviation is less than the predetermined threshold.

9. The machine tool according to claim 8 , wherein the vibration factor estimating unit is configured to compare a first Q value obtained based on the first frequency characteristic and a second Q value obtained based on the second frequency characteristic with a predetermined Q value threshold when the deviation is less than the predetermined threshold, and also configured to estimate that there is a high possibility that a vibration inherent to the machine tool is occurring when both the first Q value and the second Q value are less than the predetermined Q value threshold and estimate that there is a high possibility of electrical noise occurring when at least one of the first Q value and the second Q value is equal to or greater than the predetermined Q value threshold.

10. A vibration diagnosis support method for supporting diagnosis of vibration of a machine tool having a drive system ranging from a servo motor to a driven target driven by drive force of the servo motor, comprising:
a first measurement step of measuring a physical quantity representing a state of the machine tool when a drive shaft of the servo motor swings in accordance with a first oscillation signal, the first oscillation signal being configured to cause the drive shaft to swing periodically and having an oscillation frequency that becomes higher with time;
a second measurement step of measuring the physical quantity when the drive shaft swings in accordance with a second oscillation signal, the second oscillation signal being configured to cause the drive shaft to swing periodically and having an oscillation frequency that becomes lower with time; and
a frequency characteristic calculation step of calculating a first frequency characteristic based on a measurement signal of the physical quantity measured at the first measurement step, and the first oscillation signal, and calculating a second frequency characteristic based on a measurement signal of the physical quantity measured at the second measurement step, and the second oscillation signal.

11. The vibration diagnosis support method according to claim 10 , further comprising a display step of causing a display device to display the first frequency characteristic and the second frequency characteristic in a comparative manner.

12. The vibration diagnosis support method according to claim 11 , wherein the display step causes the display device to display, in a distinctive manner, a first resonance point appearing in the first frequency characteristic and a second resonance point appearing in the second frequency characteristic corresponding to the first resonance point when a deviation between the first resonance point and the second resonance point is equal to or greater than a predetermined threshold.

13. The vibration diagnosis support method according to claim 11 , wherein the display step causes the display device to display a comment relating to vibration in accordance with a deviation between a first resonance point appearing in the first frequency characteristic and a second resonance point appearing in the second frequency characteristic co

Assignees

• Fanuc Corp

Inventors

• Arimatsu Yohei

Classifications

• G01N29/4445

  Classification of defects · CPC title

• B23Q17/12

  for indicating or measuring vibration · CPC title

• G01N29/12 Primary

  by measuring frequency or resonance of acoustic waves {(measuring frequency or resonant frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04, G01H13/00; acoustic resonators G10K11/04; vibration or shock testing of structures G01M7/00)} · CPC title

• G01H1/003

  of rotating machines (G01H1/10 takes precedence) · CPC title

• G01H13/00

  Measuring resonant frequency · CPC title