JPS61117051A - Tool breakage detecting apparatus - Google Patents

Abstract

PURPOSE:To prevent the erroneous detection due to noise by outputting an alarm signal on the basis of the detection signal for the breakage of a tool by a sound-wave sensor only when the number of revolutions of a main shaft becomes over a prescribed value, in an NC machine tool. CONSTITUTION:A controller 2 drives a machine tool 1 according to a set program, and when the revolution speed signal supplied from a revolution speed sensor 10 exceeds a certain value, said controller outputs a revolution speed signal (a). While, an AE signal (b) is outputted from an AE detector 5 according to the output supplied from a sound-wave sensor 4 according to the cutting condition, and if anomaly exists, a cutting anomaly signal (c) is outputted, and input into a tool breakage judging apparatus 6 with the signal (a). When the both signals (a) and (c) are H, an alarm signal (d) which passes through the AND circuit 15 in case of turning-ON of an unmanned operation switch 18 is sent into the NC controller 2, through an AND circuit 14, and an alarm signal (e) is sent into a power source apparatus 17, and the machine stops operation, and the necessary information is displayed onto an indicator 9. Therefore, the noise in transient period in the revolution of the main shaft can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tool damage detection device in a numerically controlled (NC) machine tool.

[Conventional technology]

NC machine tools are equipped with a large number of cutting tools and automatically perform multi-step machining by changing the tools according to the machining process.

In such NC machine tools, if the tool is damaged, machining will proceed without proper cutting, resulting in machining defects and idle machining time, reducing the operating rate of the machine. Therefore, when a tool is damaged, it is necessary to immediately stop the machine and take necessary measures such as replacing the tool.

Traditionally, A E (A
There is a method (coustic emission), that is, when an object breaks, internal strain energy is released, and at that time, a high frequency sound wave is generated, and damage to the tool is detected by detecting this sound wave.

[Problems to be solved by the invention] However, NC machine tools have various noises, such as noises when a tool is attached to and removed from the spindle, noises made when the spindle rotates and stops, and gear changes to change the rotation speed. It is difficult to distinguish between the sound waves generated when the tool is damaged and these noises, and erroneous detections often occur.

Means for Solving Problem C] The present invention provides an alarm when there is a signal detected by a sonic sensor at the time of tool damage and a signal from a rotation speed detector when the spindle exceeds a predetermined rotation speed. It is equipped with a tool damage detector that emits a signal.

[For production]

A signal is emitted based on the tool damage detection signal from the sonic sensor only when the spindle rotation speed exceeds a predetermined value, and each scratching operation noise is generated when the spindle rotation speed increases or decreases or when the spindle stops. This eliminates the influence of

〔Example〕

First, in the present invention, it is noted that the above-mentioned noise occurs during the transition period of starting and stopping the rotation of the spindle, or during the rotation stop, and the AE
The detection timing is set when the rotation of the spindle is in a steady state, so that only the sound waves generated when the tool is damaged can be reliably detected.

Embodiments of the present invention will be specifically described below with reference to the drawings.

In the figure, 1 is the NC work #N castle, and 2 is the NCi #I control device. A sonic sensor 4 is installed near the tool 3, and the sonic sensor 4 is connected to an AE detector 5. The AE detector 5 is further connected to a tool damage discriminator 6. A printer 7, a keyboard 8, and a display 9 are connected to the tool damage discriminator 6 as necessary to enable setting of discrimination conditions and necessary display. ,
The machine tool l is driven, and the signal from the rotational speed detector 10 is processed appropriately, and when the rotational speed exceeds a certain value, it is inputted as a rotational signal a to the tool damage discriminator 6, and from the tool damage discriminator 6 The alarm signals d and C are inputted when the tool is damaged.

Since the output from the sonic sensor 4 changes depending on the cutting conditions, set the amplification factor of the amplifier 11 from the keyboard 8 and set the amplification factor of the amplifier 11.
Appropriately adjust the signal level from the keyboard 8
Then, the determination level setting is inputted to the comparator 12.

The output from the sonic sensor 4 is appropriately amplified and input to the tool damage discriminator 6 and the comparator 12.

The comparator 12 determines whether the AE flaw signal from the amplifier 11 is higher or lower than a set discrimination level, and if it is higher, inputs the cutting abnormality signal C to the tool damage discriminator 6.

The tool damage discriminator 6 includes an A/D converter 13 and an AND circuit 1.
4.15, has an arithmetic unit 16, and the AE flaw signal is A/D
The signal is digitally processed by the converter 13 and input to the arithmetic unit 16 . Also rotation signal A1 off 1g! IJ11 normal signal C is AND
When the rotation signal a and the cutting abnormality signal C are both input to the circuit 14, the AND circuit 14 issues a signal to cause the computing unit 16 to perform a discrimination operation.When there is a signal from the AND circuit 14, the computing unit 16 issues an AND circuit 15 output to AND circuit 1
An alarm signal d is sent to the NC control device 2 and the power supply device 17 via the
, emits e. The NC control H device 2 stops the work 1IH41, and then the power supply device 17 cuts off the power supply to the NNC11d1 device 2. Further, the computing unit 16 is a printer 7,
Each drive signal is output to the display 9 to display required information.

Further, 18 is a switch for switching between unmanned operation and manned operation, and if this switch 18 is turned off, the AND circuit 15 will not operate and no alarm signal will be issued, so it should not be selected during test machining or manned operation. It can be used as

In the above embodiment, the AND circuit 14 is used as the tool damage discriminator 6.
Although the amplifier 11 and the ratio amplifier 1 in the AE detector 5
It may be provided between 2 and 2. Also, comparator 12 and comparator 1
2 may be provided after the A/D converter 13.

〔Effect of the invention〕

As described above, according to the present invention, damage to the tool is detected only when the main spindle is in steady rotation, thereby eliminating false detection due to noise and making it possible to reliably detect damage to the tool.

[Brief explanation of the drawing]

The figure is a block diagram showing one embodiment of the present invention. 4 is a sonic sensor, 5 is an AE detector, 6 is a tool damage discriminator, and 10 is a rotation speed detector.

Claims (1)

[Claims] 1) Equipped with a tool damage discriminator that issues an alarm signal when the signal detected by the sonic sensor and the signal from the rotation speed detector when the spindle exceeds a predetermined rotation speed match. A tool damage detection device featuring: