Diagnostic device and diagnostic method

Patent metadata

Field	Value
Publication number	US-10620164-B2
Application number	US-201816171466-A
Country	US
Kind code	B2
Filing date	Oct 26, 2018
Priority date	Oct 31, 2017
Publication date	Apr 14, 2020
Grant date	Apr 14, 2020

Abstract

A diagnostic device includes: a spindle rotational frequency acquisition unit configured to acquire a spindle rotational frequency of a spindle; a pitch acquisition unit configured to acquire a pitch of streaks generated on a surface of a workpiece; a feed rate acquisition unit configured to acquire a feed rate of a tool when mirror surface machining is performed on the surface of the workpiece; a streak frequency calculator configured to calculate a streak frequency that is a cause of the streaks, from the pitch of the streaks and the feed rate of the tool; a causal frequency calculator configured to calculate a causal frequency which causes vibrations of the streak frequency; and a notifying unit configured to indicate whether or not there is a peripheral device that generates vibrations at the causal frequency, around a machine tool.

First claim

What is claimed is:

1. A diagnostic device for diagnosing a cause of streaks generated on a surface of a workpiece on which mirror surface machining has been performed by a machine tool by moving a tool attached to a spindle relatively to the workpiece, the diagnostic device comprising:
a spindle rotational frequency acquisition unit configured to acquire a spindle rotational frequency of the spindle;
a pitch acquisition unit configured to acquire a pitch of the streaks generated on the surface of the workpiece;
a feed rate acquisition unit configured to acquire a feed rate of the tool when the mirror surface machining is performed on the surface of the workpiece;
a streak frequency calculator configured to calculate a streak frequency that is a cause of the streaks, from the pitch of the streaks and the feed rate of the tool;
a causal frequency calculator configured to calculate a causal frequency which causes vibrations of the streak frequency, from the spindle rotational frequency and the streak frequency; and
a notifying unit configured to indicating whether or not there is a peripheral device that generates vibrations at the causal frequency around the machine tool.

2. The diagnostic device according to claim 1 , wherein the causal frequency calculator is configured to calculate the causal frequencies by adding the streak frequency to the spindle rotational frequency and by subtracting the streak frequency from the spindle rotational frequency.

3. The diagnostic device according to claim 2 , wherein the causal frequency calculator is configured to calculate the causal frequencies by adding N times or 1/N times the streak frequency to the spindle rotational frequency and by subtracting N times or 1/N times the streak frequency from the spindle rotational frequency, where N is an integer greater than or equal to 2.

4. The diagnostic device according to claim 1 , further comprising:
a storage unit configured to store a natural vibration frequency of the spindle;
a tool vibration frequency calculator configured to calculate a tool vibration frequency of the tool associated with rotation of the spindle, from the spindle rotational frequency and a number of cutting teeth of the tool; and
a determination unit configured to determine whether or not an absolute value of difference between the natural vibration frequency and the tool vibration frequency is equal to or smaller than a threshold value,
wherein the notifying unit is configured to indicate that the streaks are caused due to vibration of the tool vibration frequency in a case that the determination unit determines that the absolute value is equal to or smaller than the threshold value.

5. The diagnostic device according to claim 4 , further comprising a spindle temperature measuring unit configured to measure a temperature of the spindle, wherein:
the storage unit is configured to store the natural vibration frequency in accordance with the temperature of the spindle; and
the determination unit is configured to determine whether the absolute value of the difference between the natural vibration frequency corresponding to the temperature of the spindle and the tool vibration frequency is equal to or smaller than the threshold value.

6. The diagnostic device according to claim 1 , wherein the pitch acquisition unit is configured to acquire the pitch of the streaks from surface roughness of the surface of the workpiece, measured by a surface roughness measuring unit.

7. The diagnostic device according to claim 6 , wherein the pitch acquisition unit is configured to calculate the pitch of the streaks, based on a surface roughness parameter as measurement result of the surface roughness measuring unit.

8. A method of diagnosing a cause of streaks generated on a surface of a workpiece on which mirror surface machining has been performed by a machine tool by moving a tool attached to a spindle relatively to the workpiece, the method comprising:
a first step of, by a spindle rotational frequency acquisition unit, acquiring a spindle rotational frequency of the spindle;
a second step of, by a pitch acquisition unit, acquiring a pitch of the streaks generated on the surface of the workpiece;
a third step of, by a feed rate acquisition unit, acquiring a feed rate of the tool when the mirror surface machining is performed on the surface of the workpiece;
a fourth step of, by a streak frequency calculator, calculating a streak frequency that is a cause of the streaks, from the pitch of the streaks and the feed rate of the tool;
a fifth step of, by a causal frequency calculator, calculating a causal frequency which causes vibrations of the streak frequency, from the spindle rotational frequency and the streak frequency; and
a sixth step of, by a notifying unit, indicating whether or not there is a peripheral device that generates vibrations at the causal frequency around the machine tool.

9. The diagnostic method according to claim 8 , wherein the causal frequency calculator calculates the causal frequencies by adding the streak frequency to the spindle rotational frequency and by subtracting the streak frequency from the spindle rotational frequency.

10. The diagnostic method according to claim 9 , wherein the causal frequency calculator calculates the causal frequencies by adding N times or 1/N times the streak frequency to the spindle rotational frequency and by subtracting N times or 1/N times the streak frequency from the spindle rotational frequency, where N is an integer greater than or equal to 2.

11. The diagnostic method according to claim 8 , further comprising the steps of:
storing a natural vibration frequency of the spindle in a storage unit;
calculating a tool vibration frequency of the tool associated with rotation of the spindle, from the spindle rotational frequency and a number of cutting teeth of the tool, by a tool vibration frequency calculator; and
determining whether or not an absolute value of difference between the natural vibration frequency and the tool vibration frequency is equal to or smaller than a threshold value, by a determination unit,
wherein the notifying unit indicates that the streaks are caused due to vibration of the tool vibration frequency in a case that the determination unit determines that the absolute value is equal to or smaller than the threshold value.

12. The diagnostic method according to claim 11 , wherein:
the storage unit stores the natural vibration frequency in accordance with a temperature of the spindle measured by a spindle temperature measuring unit; and
the determination unit determines whether the absolute value of the difference between the natural vibration frequency corresponding to the temperature of the spindle and the tool vibration frequency is equal to or smaller than the threshold value.

13. The diagnostic method according to claim 8 , wherein the pitch acquisition unit acquires the pitch of the streaks from surface roughness of the surface of the workpiece, measured by a surface roughness measuring unit.

14. The diagnostic method according to claim 13 , wherein the pitch acquisition unit calculates the pitch of the streaks, based on a surface roughness parameter as measurement result of the surface roughness measuring unit.

Assignees

• Fanuc Corp

Inventors

• Fujii Takaaki
• Tong Zheng
• Uenishi Daisuke

Classifications

• G01H13/00

  Measuring resonant frequency · CPC title

• B24B49/00

  Measuring or gauging equipment for controlling the feed movement of the grinding tool or work; Arrangements of indicating or measuring equipment, e.g. for indicating the start of the grinding operation (B24B33/06, B24B37/005 take precedence; if applicable to other machine tools, B23Q15/00 - B23Q17/00 take precedence) · CPC title

• G01N29/50

  using auto-correlation techniques or cross-correlation techniques · CPC title

• B23Q17/0976 Primary

  Detection or control of chatter (B23Q15/12 takes precedence) · CPC title

• G01N29/4454

  Signal recognition, e.g. specific values or portions, signal events, signatures · CPC title