Apparatus for detecting tool damage in automatically controlled machine tool

• US 4,574,633 A
• Filed: 02/02/1984
• Issued: 03/11/1986
• Est. Priority Date: 02/04/1983
• Status: Expired due to Fees

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Ohnuki, Yasuhide, Uchibori, Minoru
• Primary Examiner(s): Birmiel, Howard A.
• Application Number:
  US06/576,235
• Time in Patent Office: 768 Days
• Field of Search: 73/587, 364/474, 364/508, 364/184, 364/185
• US Class Current: 73/587
• CPC Class Codes: B23Q 17/098 by measuring noise
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 2219/37351 Detect vibration, ultrasound
• CPC Class Codes: G05B 2219/37434 Measuring vibration of machine or workpiece or tool

Abstract

An apparatus for detecting damage to the cutting tool fitted in a machine tool controlled by automatic machining control circuit means such as a microprocessor, which acts to sense the level of acoustic emission generated by the machine tool during machining, compares that level with one of a plurality of different predetermined data values which are stored in a memory circuit, and generates a warning signal if the noise level exceeds the predetermined level. The different data values stored in the memory circuit are respectively utilized for different machining conditions, i.e. different combinations of cutting tool, machining material, feed rate, etc.

Claims

1. An apparatus for generating warning indications of damage to a cutting tool fitted in a machine tool controlled by automatic machining control circuit means, comprising:

sensing means coupled to said machine tool for sensing acoustic emission generated by a machining operation thereof, to thereby produce an operation monitor signal whose amplitude is indicative of a level of said acoustic emission;

memory circuit means, and selector circuit means operable for setting said memory circuit means in a read operating mode and a write operating mode;

data setting means operable while said memory circuit means are functioning in said write operating mode for setting a plurality of discriminations data values into said memory circuit means, respectively corresponding to predetermined machining acoustic emission levels for each of a plurality of different machining conditions of said machine tool, and address setting means operable in said memory write mode for designating the addresses of memory locations in said memory circuit means into which said discrimination data values are respectively set by said data setting means;

address signal generating circuit means controlled by said automatic machining control circuit means for producing address signals corresponding to the address in said memory circuit means of a discrimination data value for a current machining condition of said machine tool, said address signals being input to said memory circuit means while said memory circuit means are functioning in said read operating mode, to designate output of a corresponding discrimination data value therefrom;

signal conversion means for converting said discrimination data value output from said memory circuit means into a discrimination signal;

comparator means for comparing the amplitudes of said operation monitor signal and said discrimination signal and for generating a damage indication signal when a predetermined amount of difference therebetween is attained, indicative of a condition of damage to said cutting tool, said damage indication signal being input to said automatic machining control circuit means, and said automatic machining control circuit means being responsive thereto for halting operation of said machine tool; and

warning signal generating circuit means responsive to said damage indication signal from said comparator means for generating a tool damage warning signal.

2. An apparatus according to claim 1, in which said automatic machining control circuit means further produce an operation indication signal while machining operation by said machine tool is in progress, and further comprising logic gate circuit means controlled by said operation indication signal for inhibiting output of said damage indication signal at all times other than when said machining operations are in progress.

3. An apparatus according to claim 1, in which said sensing means comprise a transducer coupled to said machine tool for generating electrical signals in response to accoustic emission generated by machining operations of said machine tool, and signal processing circuit means for converting said transducer output signals into said operation monitor signal.

4. An apparatus according to claim 3, in which said signal processing circuit means comprise a band-pass filter coupled to receive said transducer output signal and an envelope detector circuit coupled to receive an output signal from said filter to thereby generate said operation monitor signal.

5. An apparatus according to claim 1, in which said plurality of different conditions of said machine tool correspond respectively to machining operations using a plurality of different types of said cutting tool.