TOOL WEAR DETECTOR

• US 3,841,149 A
• Filed: 01/08/1973
• Issued: 10/15/1974
• Est. Priority Date: 01/08/1973
• Status: Expired due to Term

• Current Assignee: Allan I. Edwin, Melvin T. Bennett, Thomas L. Vlach
• Original Assignee: Allan I. Edwin, Melvin T. Bennett, Thomas L. Vlach
• Inventors: Edwin, Allan I., Vlach, Thomas L., Bennett, Melvin T.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Kreitman, Stephen A.
• Application Number:
  US05/322,037
• Time in Patent Office: 645 Days
• Field of Search: 73/71.4,70,71,71.2,67.2,67.4,104,67.3 340/267R 235/151.3
• US Class Current: 73/659
• CPC Class Codes: G01N 3/58 Investigating machinability by cutting tools; Investigating the cutting ability of tools
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 2219/37525 Mean, average values, statistical derived values

Abstract

A tool wear detector wherein a tool wear condition which calls for a tool change is determined by establishing a reference value representing the broadband vibrational energy output of the tool during utilization thereof in a relatively unworn condition, maintaining a running average of broadband vibrational energy levels during successive and substantially regular intervals of tool utilization in progressively more worn conditions and comparing the running average to the reference value such that the tool change condition is indicated whenever the running average exceeds the reference value by some predetermined amount. In the illustrated embodiment, the running average is maintained on the basis of ten successive vibrational energy level readings taken at ten discrete intervals during a cutting operation. The vibrational energy level readings are taken by means of an accelerometer producing an analog representation.

Claims

1. Apparatus for detecting a tool wear condition comprising:

input means for obtaining signals representing discrete values of the energy level of a signal quantity produced during operation of the tool, first means for establishing a reference value representing the energy of the tool in a first relatively unworn condition, second means connected to said input means for maintaining a running average of a predetermined number N of said signals taken at substantially regular and successive intervals during utilization of the tool, and output means for producing an indication when said running average varies from said referEnce value by a predetermined amount.

2. Apparatus as defined in claim 1 where N is on the order of 10.

3. Apparatus as defined in claim 1 wherein said output means is actuated whenever said running average is approximately 15 percent greater than said reference value.

4. Apparatus as defined in claim 1 wherein said input means produces an electrical signal which is an analog representation of vibration energy levels.

5. Apparatus as defined in claim 4 including means for monitoring the dc level of said analog signal to indicate an incipient catastrophic condition.

6. Apparatus as defined in claim 4 including means to convert said analog signal representation to digital form, said analog-to-digital converter means being connected between said input means and said second means.

7. Apparatus as defined in claim 4 wherein said input means comprises an accelerometer.

8. A method of detecting a tool wear condition comprising the steps of:

establishing a reference value of energy produced by the tool during utilization thereof in a relatively unworn condition, measuring vibrational energy levels produced by the tool at successive regularly spaced intervals during utilization thereof in progressively more worn conditions, calculating a running average of said vibrational energy levels, comparing a representation related to the average to the reference value, and generating an indication when the average varies from the reference value by at least some predetermined amount.

9. A method as defined in claim 8 wherein the step of establishing a reference value of energy includes the further steps of attaching an accelerometer to the tool and operating the accelerometer to produce an analog signal representation of the vibration level produced by the tool.

10. The method defined in claim 9 wherein the step of calculating the running average includes the further step of converting the analog signal representations of the accelerometer to digital form.