AUTOMATIC SONIC DETECTION OF CHIPPED CUTTING TOOLS

• US 3,793,627 A
• Filed: 06/28/1972
• Issued: 02/19/1974
• Est. Priority Date: 06/28/1972
• Status: Expired due to Term

• Current Assignee: Bernard Darrel, Paul F. Scott
• Original Assignee: Bernard Darrel, Paul F. Scott
• Inventors: Darrel, Bernard, Scott, Paul F.
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/267,120
• Time in Patent Office: 601 Days
• Field of Search: 340/267R,261 73/67,71.4,104
• US Class Current: 340/680
• CPC Class Codes: B23Q 17/0971 by measuring mechanical vibrations of parts of the machine arrangements for measuring vibrations B23Q17/12
• CPC Class Codes: B23Q 17/098 by measuring noise
• CPC Class Codes: G01N 2291/02827 Elastic parameters, strength or force
• CPC Class Codes: G01P 15/09 by piezoelectric pick-up

Abstract

A cutting tool wear signal is obtained in known manner by sensing the sonic vibrations generated by the cutting action and extracting the high frequencies indicative of cutting tool wear. A chipped tool causes a rapid increase or decrease in the gradually rising averaged tool wear signal. The detection circuit detects this rapid increase or decrease with provision for rejecting the starting and stopping transients in the tool wear signal. The system is compatible with sonic detection of an excessively worn cutting tool.

Claims

1. A chipped cutting tool detection system comprising means for sensing the vibrations of a cutting tool during a machining operation and generating an averaged cutting tool wear signal with a slowly changing amplitude as the tool wears, chippped tool detection circuit means for rejecting transients in said averaged tool wear signal and for producing a chipped tool output signal in response to rapid increases and decreases in said slowly changing tool wear signal caused by chipping of the cutting tool, and output means for indicating the occurrence of a chipped tool, wherein said chipped tool detection circuit means comprises a pair of independently operating circuit sections for respectively detecting the rapid increases and rapid decreases in said averaged tool wear signal, said averaged tool wear signal being supplied in parallel to said pair of circuit sections.

2. A system according to claim 1 wherein said detection circuit sections respectively produce said chipped tool output signal only when the rapid increases and decreases in said averaged tool wear signal exceed predetermined magnitudes.

3. A chipped cutting tool detection system comprising a vibration transducer for sensing the vibrations of a cutting tool during a machining operation, anD an associated frequency selective circuit for generating an averaged cutting tool wear voltage signal, said tool wear signal having a slowly increasing amplitude with greater tool wear and a fast rising starting transient and a fast falling stopping transient, a first chipped tool detection circuit for rejecting said starting transient and for producing a first chipped tool output signal in response to detecting a rapid increase in said slowly increasing averaged tool wear signal caused by chipping of the cutting tool, a second chipped tool detection circuit for rejecting said stopping transient and for producing a second chipped tool output signal in response to detecting a rapid decrease in said slowly increasing averaged tool wear signal caused by chipping of the cutting tool, said averaged tool wear signal being fed to said first and second chipped tool detection circuits in parallel, and output means actuated by either chipped tool output signal for indicating the occurrence of a chipped tool.

4. A system according to claim 3 wherein said first chipped tool detection circuit rejects at least the portion of said starting transient below a selected threshold signal level, and said second chipped tool detection circuit rejects the portion of said stopping transient below the selected threshold signal level, and has a predetermined delay between said rapid decrease and the production of said second chipped tool output signal sufficient for said stopping transient to decay below said threshold level.

5. A system according to claim 4 wherein said threshold signal level is adjustable and said predetermined delay is adjustable, and said first and second chipped tool detection circuits respectively produce said chipped tool output signals only when the rapid increases and decreases in said averaged tool wear signal exceed predetermined adjustable magnitudes.

6. A system according to claim 3 wherein said first chipped tool detection circuit comprises a first voltage follower to which said averaged tool wear signal is supplied, a second voltage follower controlled by the voltage on a control capacitor that approximates said averaged tool wear signal except when said starting transient is below a predetermined threshold level, a bistable circuit connected to sense the output of said first voltage follower and change state at said threshold level, a pair of control capacitor charging circuits effectively controlled by said bistable circuit for charging said control capacitor at a first rate below said threshold level and a slow rate above said threshold level, and a comparator that produces said first chipped tool output signal when the output of said second voltage follower exceeds the attenuated output of said first voltage follower.

7. A system according to claim 3 wherein said second chipped tool detection circuit comprises a peak detector circuit with a long hold period to which said averaged tool wear signal is supplied, a delay circuit for delaying said averaged tool wear signal, a first comparator that produces an output only when said averaged tool wear signal is less than a predetermined threshold signal level, and a second comparator that produces said second chipped tool output signal when the attenuated output of said peak detector circuit exceeds the output of said delay circuit and the output of said first comparator.

8. A chipped cutting tool detection system comprising means for sensing the vibrations of a cutting tool during a machining operation and generating an averaged cutting tool wear signal with a slowly changing amplitude as the tool wears, a chipped tool detection circuit including means for rejecting transients in said averaged tool wear signal and means for producing a chipped tool output signal in response to rapid increases and decreases in said slowly changing tool wear signal caused by a substantially duller or sharper chipped cutting tool edge, and output means for indicating the occurrenCe of a chipped tool.

9. A system according to claim 8 wherein said means for rejecting transients rejects both a fast rising starting transient and a fast falling stopping transient in said averaged tool wear signal.

10. A system according to claim 8 wherein said means for rejecting transients rejects any portion of said transients in said tool wear signal below a preselected adjustable threshold amplitude level, and said means for producing a chipped tool output signal includes a predetermined adjustable delay between the rapid increase in said tool wear signal and the production of said chipped tool output signal sufficient for said transients to decay below said preselected threshold level.