Apparatus for predicting tool life

• US 5,428,556 A
• Filed: 10/06/1994
• Issued: 06/27/1995
• Est. Priority Date: 05/27/1992
• Status: Expired due to Fees

• Current Assignee: Okuma Corporation
• Original Assignee: Okuma Corporation
• Inventors: Okabe, Masayuki, Torizawa, Yoshio, Shimizu, Shinji
• Primary Examiner(s): Ramirez, Ellis B.
• Assistant Examiner(s): PEESO, THOMAS R
• Application Number:
  US08/319,055
• Time in Patent Office: 264 Days
• Field of Search: 364/551.02, 364/474.2, 364/474.21, 364/474.17, 395/575, 340/679, 340/680, 73/808, 73/810, 73/821
• US Class Current: 702/34
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 2219/37249 Correction coefficient of life time as function of kind of machining
• CPC Class Codes: G05B 2219/37251 Selfcorrecting, counter for tool life adapts correction
• CPC Class Codes: G05B 2219/37252 Life of tool, service life, decay, wear estimation
• CPC Class Codes: G05B 2219/37336 Cutting, machining time
• CPC Class Codes: G05B 2219/37587 Count number of machining cycles, frequency use of tool
• CPC Class Codes: G05B 2219/37601 Count number of times tool is overloaded, derived from mean and limit

Abstract

There is provided an apparatus for predicting a tool life which reports a tool life ratio to an operator or a control device, when a remarkable change of work load values is detected. In a predicted life setting section 122, there is set a percentage of a quantity worked until the detection of the noticeable change of the work load values based on the workable quantity until the breakage of the tool which is regarded as 100%. A predicted residual work quantity calculating section 123 calculates a residual tool life value converted into a parameter at a point of time when an alarm is input from a work load monitoring section 121, on the basis of data of a work quantity accumulating section 120 and the predicted life setting section 122. A predicted residual work quantity outputting section 124 reports the residual tool life value to an operator or a control device. In consequence, when the remarkable change of the work load values has been detected, a ratio of the residual work quantity to the tool life can be reported to the operator or the control device.

Claims

1. An apparatus for predicting a residual tool life of a tool attached to a machine tool which comprises:

(a) a work quantity accumulating section for accumulating a parameter which represents expended tool life,

(b) a work load monitoring section for detecting a significant change of work load values of the tool,

(c) a predicted life setting section for storing a normalized residual tool life ratio for the tool at a point of time when the significant work load values change appears;

(d) a predicted residual work quantity calculating section for calculating a residual tool life on the basis of the accumulated parameter representing expended tool life of the work quantity accumulating section and the normalized residual tool life ratio of the predicted life setting section, when the significant change of the work load values is detected in the work load monitoring section, and

(e) a predicted residual work quantity outputting section for externally reporting the residual tool life calculated by the predicting residual work quantity calculating section.

2. The apparatus of claim 1, wherein the accumulating section accumulates the number of machining operations performed by the tool.

3. The apparatus of claim 1, wherein the accumulating section accumulates the number of holes made by the tool.

4. The apparatus of claim 1, wherein the accumulating section accumulates a period of time the tool has been in operation.

6. The work load monitor of claim 2, further comprising:

(h) a work quantity accumulating section for accumulating a parameter representing expended tool life,

(i) a predicted life setting section for storing a normalized residual tool life ratio for the tool at a point of time when the significant work load values change appears,

(j) a predicted residual work quantity calculating section for calculating a residual tool life on the basis of the accumulated parameter representing expended tool life of the work quantity accumulating section and the normalized residual tool life ratio of the predicted life setting section, when the significant change of the work load values is detected, and

(k) an outputting section for outputting the residual tool life calculated by the predicting residual work quantity calculating section.

7. The work load monitor of claim 6, wherein the accumulating section accumulates a number of operations performed by the tool.

5. A work load monitor which comprises:

(a) a memory section for storing a predetermined number of work load values of a tool as digital data,

(b) an averaging processing section for calculating a mean value of the work load values,

(c) a band width setting section for setting an allowable width of fluctuation of each of the work load values from the mean value calculated in the averaging processing section,

(d) an abnormal signal detecting section for comparing a difference between the mean value calculated in the averaging processing section and each of the work load values with the allowable width set by the band width setting section, and then outputting abnormal signals when the difference is in excess of the allowable width,

(e) a counter section for counting a number of the abnormal signals output,

(f) a normalizing section for calculating a normalized ratio of the number of the abnormal signals output to the predetermined number of work load values, and externally outputting the normalized ratio, and

(g) a comparing section for outputting an alarm so as to report a significant change of the work load values, when the normalized ratio is larger than a predetermined value.