US 4,831,365 A · Cutting tool wear detection apparatus and method

Abstract

Sharp tools have different cutting characteristics from dull or worn tools. Among these differences is that a wear land develops on the cutting tool so that more of the cutting tool comes into contact with the workpiece during the cutting process. The increased contact area between the tool and workpiece forces more energy to be consumed by the cutting machine in making a cut because more energy is expended in non-productive work. Indications of an increase in non-productive work are the increased power or force necessary to operate a spindle in lathes, milling machines, etc., and the increased energy in cutting vibrations in a low frequency range emitted during the cutting process. Another indication of decreased efficiency of the cutting process is the decreased energy in cutting vibrations in a high frequency range emitted during the cutting process. A method and apparatus are described for continuously monitoring a ratio of spindle force or power or low frequency vibration energy to high frequency vibration energy during the cutting process, and generating an output warning signal when the radio reaches a preselected level correlated with excessive tool wear.

Claims28

Dependent claims

A method for automatically detecting worn cutting tools used in machining workpieces comprising the steps of:

(a) sensing data during a machining operation and generating at least one electrical signal indicative of said data;
(b) utilizing said at least one electrical signal to obtain at least two component signals, a first component signal indicative of data of high frequency vibration having a frequency range of from about 25 kHz to about 100 kHz at the tool-workpiece interface and a second component signal indicative of data corresponding to energy consumed during the cutting process;
(c) sampling said sampled first component signal to converting said sampled first component signal to digitized values and deriving a tracking cutting vibration signal corresponding to at least one statistical value of said first component signal that tracks changes in the vibration energy in that signal;
(d) sampling said second component signal, converting said sampled second component signal to digitized values, and deriving a tracking signal corresponding to at least one statistical value of said second component signal that tracks changes in the energy in that signal;
(e) using said tracking first component vibration energy signal and said tracking second component energy signal to obtain a ratio signal representative of the ratio of said tracking first and second component energy signals;
and
(f) producing an output indication when said ratio signal representative of said ratio reaches a predetermined threshold level indicative of a preselected amount of cutting tool wear.

4 more elements

An apparatus for automatically detecting worn cutting tools used in machining workpieces by a machine comprising;

(a) at least one sensor for sensing characteristics of the machine during a machining operation and for generating an electrical signal corresponding to said characteristics;
(b) a first bandpass filter means for extracting at least a first component signal from said electrical signal generated by said at least one sensor, said first component signal corresponding to a high frequency vibration signal in the range of from about 25 kHz to about 100 kHz;
(c) consumed energy monitoring means extracting at least a second component signal from said at least one sensor, said second component signal being indicative of the energy consumed during the machining operation;
(d) sampling means for sampling each of said component signals and for generating a signal indicative of the relationship between at least one statistical value of each of said sampled component signals;
and
(e) alarm means for producing an output indication indicative of a predetermined degree of cutting tool wear when said signal indicative of the relationship between said at least one statistical value of each of said sampled component signals reaches a predetermined threshold value indicative of a predetermined degree of cutting tool wear;
wherein said at least one sensor comprises a vibration transducer for generating an electrical signal corresponding to a broadband vibrational frequency spectrum;
and said consumed energy monitoring means further comprises a low pass filter means for extracting said second component signal from said electrical signal generated by said vibration transducer, said second component signal corresponding to a low frequency vibration signal in a range of less than about 700 Hz, and being indicative of the energy consumed during the machining operation.

5 more elements

Dependencies are inferred from the claim text.

Cutting tool wear detection apparatus and method

Life of this patent

Cutting tool wear detection apparatus and method

Life of this patent

Abstract

Claims28