TOOL DAMAGE/ABNORMALITY DETECTING DEVICE

• US 20060142893A1
• Filed: 08/23/2005
• Published: 06/29/2006
• Est. Priority Date: 12/28/2004
• Status: Active Grant

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Yasugi, Kuniharu, Maekawa, Susumu
• Granted Patent: US 7,092,786 B2
• Time in Patent Office: Days
• US Class Current: 700/174
• CPC Class Codes: B23Q 17/0957 Detection of tool breakage detecting failure of drills B23B49/001
• CPC Class Codes: B23Q 17/0966 by measuring a force on parts of the machine other than a motor
• 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 2219/37252 Life of tool, service life, decay, wear estimation
• CPC Class Codes: G05B 2219/41376 Tool wear, flank and crater, estimation from cutting force
• CPC Class Codes: G05B 2219/50276 Detect wear or defect tool, breakage and change tool

Abstract

A tool damage/abnormality detecting device capable of easily appropriately setting an allowable range for a value of comparison between a present value and a near past average for indexes indicative of loads on a tool. A machining cycle counter index i is adjusted to i=0, machining is performed as the loads are detected in a given period, and indexes H(i) (area S of load values, absolute value (G⁻) of a maximum inclination between two points obtained during a decrease of loads, etc.) are acquired for n number of cycles. Thereafter, the indexes and values of comparison between the index value for a present cycle and the indexes for the n number of cycles are acquired. A first comparison value can be used for initial value setting for threshold values. If any of the comparison values is deviated from the allowable range, the threshold values are updated so that the allowable range extends, and an update history is saved. If damage/abnormality is observed visually or in any other manner, a threshold value update discontinue command is inputted, machining is stopped after completion of the cycle concerned, and update values for the latest threshold value are collected to be used as set threshold values.

Claims

1. A detecting device for determining tool defect in which indexes, each index indicative of a load exerted on a tool for machining a workpiece, are acquired for a plurality of machining cycles, an index acquired in a present machining cycle is compared with an average of indexes acquired in machining cycles preceding the present machining cycle to acquire a comparison value indicative of a result of the comparison in each machining cycle, and determining damage and/or abnormality of the tool is when the comparison value deviates from an allowable range defined by set values of thresholds, said detecting device comprising means for determining the set values of the thresholds, including:

detecting means for detecting the indexes for a plurality of machining cycles;

comparing means for comparing an index in a selected machining cycle with an average of indexes for a plurality of machining cycles preceding the selected machining cycle to acquire comparison value indicative of a result of the comparison;

first storage means for storing values of the thresholds;

writing means for writing initial values of the thresholds in said first storage means;

updating means for updating the stored values of the thresholds to revised values according to a comparison value that deviates from an allowable range defined by the stored values of the thresholds when the comparison value acquired in the selected machining cycle deviates from the allowable range;

means for discontinuing the updating of the stored values of the thresholds in response to a command to discontinue the updating of the thresholds; and

determining means for determining the set values of the thresholds based on the stored values of the thresholds when the update of the values of the thresholds is discontinued.

2. The detecting device according to claim 1, wherein said indexes include a difference between maximum and minimum load values for a certain machining cycle, an area of load values for the certain machining cycle, and an average of absolute values of loads for the certain machining cycle, a difference between the average of the absolute values of the loads for a directly preceding machining cycle, a value obtained by dividing the difference between the maximum and minimum load values for the certain machining cycle by the average of the absolute values of the loads for the same machining cycle, an absolute value of a maximum inclination between two points obtained during an increase of loads in the certain machining cycle, and/or an absolute value of a maximum inclination between two points obtained during a decrease of the loads in the certain machining cycle, and

the set values of the thresholds are determined for the indexes of various types so that the damage/abnormality of the tool is detected based on at least one of the determined set values of the thresholds.

3. The detecting device according to claim 1, wherein the load exerted on the tool is detected as a torque of a motor for rotating the tool.

4. The detecting device according to claim 1, wherein the load exerted on the tool is detected as a thrust load exerted on the tool.

5. The detecting device according to claim 1, wherein said writing means writes the initial values of the thresholds based on a first comparison value acquired by said comparing means into said first storage means.

6. The detecting device according to claim 1, wherein the tool comprises a drill or tap.

7. A detecting device for determining tool defect in which indexes, each index indicative of a load exerted on a tool for machining a workpiece, are acquired for a plurality of machining cycles, an index acquired in a present machining cycle is compared with an average of indexes acquired in machining cycles preceding the present machining cycle to acquire a comparison value indicative of a result of the comparison in each machining cycle, and determining damage and/or abnormality of the tool is when the comparison value deviates from an allowable range defined by set values of thresholds, said detecting device comprising means for determining the set values of the thresholds, including:

detecting means for detecting the indexes for a plurality of machining cycles;

comparing means for comparing an index in a selected machining cycle with an average of indexes for a plurality of machining cycles preceding the selected machining cycle to acquire a comparison value indicative of a result of the comparison;

first storage means for storing values of the thresholds;

writing means for writing initial values of the thresholds in said first storage means;

updating means for updating the stored values of the thresholds to revised values according to a comparison value that deviates from an allowable range defined by the stored values of the thresholds when the comparison value acquired in the selected machining cycle deviates from the allowable range;

second storage means for storing a threshold history containing at least some of the values of the thresholds stored in said first storage means prior to the latest updating;

means for discontinuing the updating of the values of the thresholds in response to a command to discontinue the updating of the thresholds; and

determining means for determining the set values of the thresholds based on the values of the thresholds stored in said second storage means when the update of the values of the thresholds is discontinued.

8. The detecting device according to claim 7, wherein said indexes include a difference between maximum and minimum load values for a certain machining cycle, an area of load values for the certain machining cycle, and an average of absolute values of loads for the certain machining cycle, a difference between the average of the absolute values of the loads for a directly preceding machining cycle, a value obtained by dividing the difference between the maximum and minimum load values for the certain machining cycle by the average of the absolute values of the loads for the same machining cycle, an absolute value of a maximum inclination between two points obtained during an increase of loads in the certain machining cycle, and/or an absolute value of a maximum inclination between two points obtained during a decrease of the loads in the certain machining cycle, and

the set values of the thresholds are determined for the indexes of various types so that the damage and/or abnormality of the tool is detected based on at least one of the determined set values of the thresholds.

9. The detecting device according to claim 7, wherein the load exerted on the tool is detected as a torque of a motor for rotating the tool.

10. The detecting device according to claim 7, wherein the load exerted on the tool is detected as a thrust load exerted on the tool.

11. The detecting device according to claim 7, wherein said writing means writes the initial values of the thresholds based on a first comparison value acquired by said comparing means into said first storage means.

12. The detecting device according to claim 7, wherein the tool comprises a drill or tap.

13. A detecting device for determining tool defect in which indexes, each index indicative of a load exerted on a tool for machining a workpiece, are acquired for a plurality of machining cycles, an index acquired in a present machining cycle is compared with an average of indexes acquired in machining cycles preceding the present machining cycle to acquire a comparison value indicative of a result of the comparison in each machining cycle, and determining damage and/or abnormality of the tool when the comparison value deviates from an allowable range defined by set values of thresholds, said detecting device comprising means for determining the set values of the thresholds, including:

detecting means for detecting the indexes for a plurality of machining cycles;

comparing means for comparing an index in a selected machining cycle with an average of indexes for a plurality of machining cycles preceding the selected machining cycle to acquire a comparison value indicative of a result of the comparison;

first storage means for storing values of the thresholds;

writing means for writing initial values of the thresholds in said first storage means;

updating means for updating the stored values of the thresholds to values according to a comparison value that deviates from an allowable range defined by the stored values of the thresholds when the comparison value acquired in the selected machining cycle deviates from the allowable range;

second storage means for storing a threshold history containing at least some of the values of the thresholds stored in said first storage means prior to the latest updating;

means for discontinuing the updating of the stored values of the thresholds in response to a command to discontinue the updating of the thresholds; and

determining means for determining the set values of the thresholds based on the threshold history stored in said second storage means and the values of the thresholds stored in said first storage means when the update of the values of the thresholds is discontinued.

14. The detecting device according to claim 13, wherein said indexes include a difference between maximum and minimum load values for a certain machining cycle, an area of load values for the certain machining cycle, and an average of absolute values of loads for the certain machining cycle, a difference between the average of the absolute values of the loads for a directly preceding machining cycle, a value obtained by dividing the difference between the maximum and minimum load values for the certain machining cycle by the average of the absolute values of the loads for the same machining cycle, an absolute value of a maximum inclination between two points obtained during an increase of loads in the certain machining cycle, and/or an absolute value of a maximum inclination between two points obtained during a decrease of the loads in the certain machining cycle, and

the set values of the thresholds are determined for the indexes of various types so that the damage and/or abnormality of the tool is detected based on at least one of the determined set values of the thresholds.

15. The detecting device according to claim 13, wherein the load exerted on the tool is detected as a torque of a motor for rotating the tool.

16. The detecting device according to claim 13, wherein the load exerted on the tool is detected as a thrust load exerted on the tool.

17. The detecting device according to claim 13, wherein said writing means writes the initial values of the thresholds based on a first comparison value acquired by said comparing means into said first storage means.

18. The detecting device according to claim 13, wherein the tool comprises a drill or tap.