SU1426699A2 - Apparatus for monitoring condition of cutting tool - Google Patents

Abstract

The invention relates to mechanical engineering and can be used to determine the wear and breakage of a cutting tool directly in the course of machining parts on machine tools. The purpose of the invention is to expand the functionality by obtaining information about the failure of the cutting tool. When the signal decreases below the minimum level during cutting, followed by its increase, it is possible to determine the failure of the cutting tool with the help of entered comparators 18, 20, differentiator 19, single vibrator 21, trigger 22 and conjuncture 23. 1 sludge.

Description

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The invention relates to a machine structure and can be used. to determine the wear and breakage of the cutting tool directly during the machining of parts on machines,

The purpose of the invention is the expansion of functional capabilities.

The drawing shows the block diagram of the proposed device.10

The device contains a vibration converter 1, a preamplifier 2, band-pass filters 3 and D.dectors 5 and 6, blocks 7 and 8 divisions, comparators 9 and 10, integrators 11 15 and 12, amplifier-limiter 13, voltage source 14, analog key 15, analog memory 16, machine control system 17, third comparator 18, 20 differentiator 19, fourth comparator 20, one-shot 21, trigger 22 and conjunctor 23.

The device works as follows .25

The vibroacoustic emission signal (VAZ) emitted by the cutting zone is recorded by the vibration converter 1, amplified by the preamplifier 2 and fed to parallel-connected band-pass filters 3 and 4. Filter 3 selects the low-frequency component of the VAZ spectrum and the filter. 4 - high frequency component.

An increase in tool wear leads to a redistribution of the VAZ spectrum (the high-frequency part increases). Therefore, to determine the amount of wear, the signal from filter 3 and 4 through detectors 5 and 6 is fed to the input of block 7 division, the signal at the output of which corresponds to the value of tool wear.

However, when processing parts of complex shape, the indications on the division block 7 45 will differ in different parts of the detail, due to the influence on the VAZ spectrum of changes in cutting speed, cut geometry and variations in allowance. In addition, the transition to a new diameter when machining stepped parts causes a relatively long (several seconds) transition process at the output of block 7, due to the fact that the tool needs to grate to a new diameter. Therefore, in order to eliminate the influence of these factors on the measurement accuracy of wear, an integrator 12 is introduced into the device, which integrates the signals at the output of dividing unit 7 during the entire time of part processing. Thus, the signal at the output of block 12 is the average integral wear value, and since the VAZ signal is stationary random, then the accuracy of measurement of parameters based on it will be the higher the averaging time. Therefore, the signal at the output of the integrator 12 characterizes tool wear.

To further improve the accuracy of the device, the signal from the output of the integrator 12 is fed to a dividing unit 8, the second input of which is supplied with a voltage from the output of the integrator 11 proportional to the actual processing time of each part.

Measurement of the actual processing time is as follows. The high-frequency part of the VAZ signal (as less noisy) is fed through the limiting amplifier 13 to the control input of the analog switch 15 and opens it for the duration of the cutting process, and since the integrator 11 is charged with a constant voltage, the voltage at the integrator's output 11 in proportion to the processing time.

Next, the signal from the output of dividing unit 8 is the time averaged wear value, fed to the input of the comparator 10, to another input of which voltage is supplied from the analog storage device 16, in which, in the learning mode, the average value of the signal corresponding to the worn tool is stored ( learning mode is processed with a worn tool).

In the operation mode, the comparator 10 compares the wear value after machining the next part with the memorized one and, if they coincide or exceed the memorized voltage, a command is sent to the TNC system to stop the process and call the operator or automatically change the tool.

During the cutting process, tool breakage is possible, caused, for example, by foreign inclusions in the workpiece. A tool breakage is accompanied by an increased VAZ intensity with its subsequent decline, which is caused by the shortening of the tool cutting edge, due to

as a result, the signal at the output of dividing unit 7 increases sharply and then decreases. When the signal at the output of the dividing unit 7 is increased, the comparator 9 is triggered, setting the trigger 22 to one state. When the signal at the output of dividing unit 7 is reduced, a positive signal is generated at the output of differentiator 19, the value of which is not triggered by the fourth comparator 20, and a single level is formed at its output. When a tool breaks, the signal at the input of the third comparator 18 is reduced to a level, 15 corresponding to the minimum level during cutting and a single signal is formed at its output. In this case, on all three inputs of the conjuncer 23 there are single levels, and from its 20 outputs into the machine control system 17, the command is given to immediately remove the tool from the machining zone and stop the spindle rotation.

If a tool breakage did not occur, and an increase in the signal from the output of dividing unit 7 was caused, for example, by self-oscillation or hardening, then the decrease in signal from the output of dividing unit, 7 dividing will stop at level b. higher than the level of operation of the third comparator 18. By stopping the decrease of the signal at the input of the differentiator 19 and its output, a zero signal is formed, which causes the fourth comparator 20 to turn off and, when the signal drops at its output, the one-shot 21 forms a pulse that sets the trigger 22 to the zero state the

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In particular cases, for example, when roughing, characterized by sharp fluctuations of allowances, the signal from the output of the first comparator 9 can be used as an increased load signal.

Thus, determining the cutting tool breakage by reducing the signal below the minimum level during cutting, followed by its increase, allows determining the cutting tool breakage and eliminating false stops of the cutting process to replace the tool during the appearance of work hardening, self-oscillations, etc. random increase in the intensity of the WHA.

Claims (1)

Invention Formula A device for monitoring the condition of the cutting tool according to auth.St. No. 1079368, characterized in that, in order to expand its functionality, a third comparator and a serially connected differentiator, a fourth comparator, a one-shot, a trigger, a conjunctor are introduced into it, the inputs of the third comparator and the differentiator are connected to the output of the first division unit, the second and third inputs the conjuncture is connected to the outputs of the third and fourth comparators, respectively, the second trigger input is connected to the output of the first comparator, and the output of the conjunctor is connected to the machine control system.