METHOD AND APPARATUS FOR DETECTING TOOL WEAR

• US 3,694,637 A
• Filed: 10/22/1970
• Issued: 09/26/1972
• Est. Priority Date: 10/22/1970
• Status: Expired due to Term

• Current Assignee: Allan I. Edwin, Thomas L. Vlach
• Original Assignee: Allan I. Edwin, Thomas L. Vlach
• Inventors: Edwin, Allan I., Vlach, Thomas L.
• Primary Examiner(s): Botz, Eugene G.
• Application Number:
  US05/083,173
• Time in Patent Office: 705 Days
• Field of Search: 73/104,105,67.2,67,71.4 340/267R 235/151.3
• US Class Current: 702/34
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 2219/34048 Fourier transformation, analysis, fft
• CPC Class Codes: G05B 2219/37256 Wear, tool wear
• CPC Class Codes: G05B 2219/37351 Detect vibration, ultrasound

Abstract

A method and apparatus for monitoring tool wear as a function of change in a power-frequency distribution obtained by Fourier analysis of a vibrational characteristic of the tool during use. Optimum tool change time is indicated by comparing a selected power spectrum or a selected portion thereof to a reference spectrum obtained from a test tool. A small general-purpose digital computer is employed in the analysis phase. A specially designed detector circuit for actual tool monitoring is also disclosed.

Claims

1. Apparatus for analyzing the wear characteristics of a machine tool comprising:

an accelerometer for producing an output signal representing the vibration characteristic of an element in mechanical contact with the tool, and analyzer means responsive to the signal for providing frequency-power spectrum data of the vibration over a predetermined frequency range.

2. Apparatus as defined in claim 1 wherein said analyzer means comprises a digital computer for sampling said signal at a rate which is high relative to the highest frequency component in said characteristic.

3. Apparatus as defined in claim 2 wherein the computer is programmed to perform a Fourier analysis on the signal over a predetermined number of selected contiguous frequency bands.

4. A method for determining the optimum tool wear condition at which to effect a tool change comprising the steps of:

coupling a vibration transducer to the tool, obtaining a first relative power distribution representation over a broad frequency range of vibration measured by the transducer when the tool is in a relatively unworn condition;

obtaining a second relative power distribution representation over a broad frequency range of vibration measured by the transducer when the tool is in a relatively worn condition;

comparing the first and second power distribution representations to determine those relatively narrow frequency bands in which the largest power changes occur as between the worn and unworn tool conditions;

coupling a transducer to at least one additional relatively unworn tool, operating the tool, obtaining a third relative power distribution representation comprising at least the said narrow frequency bands, and changing the tool when the power levels in each of said narrow frequency bands has undergone at least a substantial portion of the total change indicated between the first and second power distribution levels.