Tool breakdown detecting system

• US 4,326,257 A
• Filed: 11/21/1979
• Issued: 04/20/1982
• Est. Priority Date: 11/21/1978
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Sata, Toshio, Matsushima, Katsumori
• Primary Examiner(s): Wise, Edward J.
• Application Number:
  US06/096,512
• Time in Patent Office: 881 Days
• Field of Search: 364/508, 364/551, 364/474, 364/111, 73/104, 73/618, 73/619
• US Class Current: 700/175
• CPC Class Codes: B23Q 17/0928 Cutting angles of lathe tools
• CPC Class Codes: B23Q 17/0957 Detection of tool breakage detecting failure of drills B23B49/001
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 2219/37245 Breakage tool, failure
• CPC Class Codes: G05B 2219/37536 Rate of change, derivative

Abstract

A tool breakdown detecting system having at least one predicted standard pattern of change in the cutting resistance of a tool corresponding to a possible breakdown is prestored in a memory and compared with an actual change pattern of the cutting resistance of the tool monitored during working. When a coincidence is found between the prestored change pattern and the actual change pattern of the tool this indicates a breakdown of tool an alarm signal is generated. The alarm signal can activate a visual or audible alarm as well as regulate the further movement of the tool.

Claims

1. A tool breakdown detecting system comprising:

memory means for storing at least one predetermined change pattern of the cutting resistance of a tool corresponding to a tool breakdown condition during working;

means for detecting the actual cutting resistance of the tool during working and forming a change pattern of the actual cutting resistance of the tool; and

comparing means for comparing the predetermined change pattern stored in the memory means with the actual change pattern of the cutting resistance of the tool during working, wherein coincidence of the two change patterns thus compared indicates a tool breakdown condition.

2. A tool breakdown detecting system according to claim 1, wherein the detecting and forming means detects and samples the cutting resistance and, for each sampling, a difference is obtained between the currently sampled value and the previously sampled one, and wherein the difference is coded and used to form the change pattern of the cutting resistance.

3. A tool breakdown detecting system according to claim 1, further comprising means for retreating the tool and wherein the comparing means is operatively connected to the tool retreating means and wherein the predetermined change pattern stored in the memory and the change pattern of the cutting resistance during working are compared and, in the case of coincidence, the tool is retreated.

4. A system for automatically detecting a breakdown of a tool during working comprising:

means for detecting cutting resistance of the tool during working;

means operatively connected to the detecting means for sampling the cutting resistance detected by the detecting means;

means operatively connected to the sampling means for storing sampled values obtained by the sampling means;

arithmetic means operatively connected to the storing means for calculating a difference between the sampled values stored in the storing means, the arithmetic means further comparing the difference calculated between the sampled values to a preset value and coding the difference between the sampled values on the basis of the compared preset value;

first memory means operatively connected to the arithmetic means for storing a progression of figures coded by the arithmetic means representing the actual change pattern of the tool;

second memory means for storing a progression of figures coded to represent at least one predetermined standard change pattern associated with a breakdown condition in the tool; and

comparing means operatively connected to the first and second memory means for comparing the actual change pattern with the at least one predetermined standard change pattern, the comparing means having means for comparing the progressions of coded figures stored in the first and second memory means with each other and means for generating a tool breakdown signal when the compared progressions of figures coincide with each other.

5. A tool breakdown detecting system according to claim 4 wherein the arithmetic means calculates, compares and codes a difference between successively sampled values of the cutting resistance of the tool.

6. A tool breakdown detecting system according to claim 4 further comprising a motor for driving a work piece held in a spindle which is to be machined by the tool, means for supplying power to the spindle motor and wherein the detecting means comprises resistor means connected in series with the spindle motor and spindle power supplying means for generating a voltage signal proportional to the cutting resistance of the tool.

7. A tool breakdown detecting system according to claim 6 further comprising means operatively connected to the spindle motor and to the sampling means for generating a sampling signal wherein the sampling means samples the actual cutting resistance voltage signal in synchronization with the sampling signal.

8. A tool breakdown detecting system according to claim 7 wherein the sampling signal generating means includes a rotary encoder for providing a signal corresponding to a predetermined rotation by the motor of the spindle.

9. A tool breakdown detecting system according to claim 8 wherein the sampling signal is generated for each rotation of the spindle.

10. A tool breakdown detecting system according to claim 7 or 8 wherein the sampling means comprises an A-D convertor which provides a digital output signal from the sampled voltage signal in synchronization with the sampling signal.

11. A tool breakdown detecting system according to claim 10 further comprising means operatively connected between the resistor means and the A-D convertor for removing noise components contained in the detected voltage signal and applying an analog signal to the A-D convertor corresponding to the cutting resistance of the tool.

12. A tool breakdown detecting system according to claim 11 wherein the removing means comprises a pass band filter.

13. A tool breakdown detecting system according to claim 4 wherein the arithmetic means codes the difference between the sampled values in a ternary composition and the second memory means stores a progression of figures representing the at least one predetermined change pattern in a coded ternary composition.

14. A tool breakdown detecting system according to claim 4 or 13 wherein the progression of figures compared by the comparing means is four.

15. A system for automatically detecting a breakdown of a tool during working comprising:

memory means for storing at least one predetermined change pattern of cutting resistance of the tool, with the change pattern corresponding to a tool breakdown condition during working;

means for detecting actual cutting resistance of the tool during working;

means for forming a change pattern of the actual cutting resistance of the tool detected by the detecting means; and

comparing means for comparing the at least one predetermined change pattern stored in the memory means with the acutal cutting resistance change pattern formed by the forming means, wherein coincidence of the two change patterns compared by the comparing means indicates a tool breakdown condition.

16. A tool breakdown detecting system according to claim 15, wherein the forming means comprises sampling means for time sampling values of the actual cutting resistance of the tool detected by the detecting means and coding means for coding a difference between values of the actual cutting resistance time sampled by the sampling means, thereby forming the actual cutting resistance change pattern of the tool.

17. A tool breakdown detecting system according to claim 16, wherein the coding means codes a difference between successively sampled values of the actual cutting resistance of the tool.

18. A tool breakdown detecting system according to claim 15 further comprising means operatively connected to the comparing means for generating a tool breakdown signal when the two compared change patterns compared by the comparing means coincide with each other.

19. A tool breakdown detecting system according to claim 18 or 11 further comprising gate means operatively connected to the tool breakdown signal generating means for controlling supply of a feed pulse which causes the tool to be fed, wherein the gate means is activated by a tool breakdown signal to interrupt the feed pulse supply for stopping the feed of the tool.

20. A tool breakdown detecting system according to claim 18 or 4 further comprising means operatively connected to the tool breakdown signal generating means for retreating the tool to a predetermined position, wherein the tool retreating means is activated by a tool breakdown signal to retreat the tool.

21. A tool breakdown detecting system according to claim 18 or 4 further comprising means operatively connected to the tool breakdown signal generating means for providing a visual or audible signal when a tool breakdown signal is generated.