SU1717296A1 - Apparatus for detecting cutting tool damage - Google Patents

Abstract

The invention relates to mechanical engineering, primarily to the means of diagnosing the state of the cutting tool in the GPM. The purpose of the invention is to expand the technological capabilities of the device by increasing the accuracy and reliability in operation, as well as increasing its adaptability to changes in cutting conditions in the GPM. The analysis of the level of the acoustic signal is carried out simultaneously on the general level of the signal and the level in the high-frequency region of the spectrum. As a result of the cutting tool breakage due to the redistribution of the vibroacoustic spectrum, the overall signal level may not change or change slightly. Additional analysis of the high-frequency region of the spectrum using the organization of the second signal transmission circuit allows fixing not only global breakdowns, when a loss of contact of the instrument with the workpiece is observed, but also its small chips and chipping. The device has a function of storing information about the magnitude of the signal levels in the intervals between cutting, which makes it possible to reliably fix the breakage at the time of insertion of the tool into the part, as well as in intermittent cutting modes. 4 il. (Ls

Description

The invention relates to mechanical engineering, primarily to the means of diagnosing the condition of the cutting tool in the PMG.

The aim of the invention is to expand the technological capabilities of the device for detecting breakage of the cutting tool by increasing the accuracy and reliability of its operation, as well as adaptability to specific conditions of cutting, due to the operation of the PMG.

FIG. 1 shows a functional diagram of the proposed device; in fig. 2 - functional diagram of the storage device; in fig. 3 - time diagrams of the device; in fig. 4 - time diagrams of zone formation

allowed values of the change of the signal OVAK.

The device diagram (Fig. 1) contains a vibration transducer 1 connected in series, an amplifier 2, a high-pass filter 3 (HPF), a detector 4, a first low-pass filter 5 (1 FNC), and also three channels of signal passing, the first of which contains in series a comparator 6 with a dead zone with its input connected to output 1 of the low-pass filter 5, and a time delay circuit 7, the input of which is connected in parallel to the second input of the AND-NE element 8. The second signal transmission channel consists of the series-connected detector 9 and the second th of LPF 10, and also two

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parallel circuits, each of which contains serially connected storage units 11 and 10, comparison circuits 13 and 14 and two-threshold comparators 15 and

16 (for the first and second circuits, respectively), the other inputs of which are connected to the outputs of the storage units 11 and 12, while the other inputs of the comparison circuits 13 and 14 are connected to the inputs of the storage units 11 and 12, respectively. The input of the storage unit 11 of the first circuit is connected to the output of 1FNCh5, ablok12-k2yod2FNCh 10.

The third channel contains a generator of 17 pulses, as well as a series-connected differentiator 1.8, its input connected to output 1 of the low-pass filter 5, a comparator with an adjustable threshold 19, the reference input of which is connected to the output of the storage unit 1.2 of the second circuit, element 8 AND-NOT connected with its first input to the output of the comparator 19, IK-trigger 10, to the inverse output of which one element OR 21 is connected by one input, and the first element 22 to the forward output of IK-trigger 20, connected to the generator output parallel to

17 impulses and the third input of the three-input element And 23, a pulse counter 24 connected in series, its input connected to the output of the first element And 22, the decoder 25, the three-input element OR 26, the second element And 27, the system

28 controls The other input of the second element AND 27 is connected to the output of the second element OR 29, the inputs of which are connected to the outputs of the two-threshold comparators 15 and 16 of both circuits of the second channel of the signal, the first input of the element 23 and connected to the inverse output of the trigger 22, the second one connected to the output of the circuit 7 delay time, and the output is connected in parallel to the write enable inputs of the storage blocks 11 and 12, the output of the comparator 19 is connected to another input of the OR element 21, the output of which is connected to the zero input input of the pulse counter 24. .

The two-threshold comparators 15 and 16 in the device provide a signal at their output to the logic IUBxi U0n (where Don is the reference voltage) and can be performed in a known pattern. The storage units 11 and 12 (Fig. 2) include an analog-to-digital converter D1, a buffer register D2, and a digital-to-analog converter D3. Analog-to-digital converter D1 is controlled by pulses from the output of the three-input element AND 23 (Fig. 1). The information is written to the buffer register D2 by the signal SE Readiness data generated in D1 (FIG. 2).

As a machine control system 28, an electro-automatic system or a CNC machine tool can be used.

The time delay circuit 7 provides the appearance of the signal logical 1 at its output 100-150 ms after the appearance of the last positive level difference at its input and can be performed according to a well-known scheme based on a one-shot with restarting.

The differentiator 18 may be performed, for example, on the basis of a differentiating operational amplifier.

The operation of the device is illustrated by time diagrams (Figs. 3, 4), on which are marked: ZOA signal — at the output of the low-pass filter 5, signal 306 — the level of operation of the comparator with the dead zone 6, signal 31 at the output of the comparator with the dead zone 6, signal 22 - at the output of the time delay circuit 7, signal ЗЗа - at the output of the differentiator 18 (signal input of the comparator with adjustable threshold 19), signal 336 - at the reference input of the comparator 19, signal 34 - at the output of the second element OR 29, signal 35 - at the output square pulse generator, signal 36 - at the output of the element 8 AND-NOT, the signal 37 - at the inverse output of the trigger 20, the signal 38 - at the output of the first element AND 22, the signal 39 - at the output of the three-input element OR 26, the signal 40 - at the output of the second element And 27, 41 a - the signal at the output of the second low-pass filter 10, 416 — at the output of the storage unit 12 of the second circuit; 42a — at the output of the comparison circuit 14; 426 and c, respectively, negative and positive response levels of the two-search comparator 16.

The device works as follows.

The signal of vibroacoustic oscillations from the output of the converter 1 of the virations installed on the tool holder or on the cutter is amplified by the amplifier 2 and fed to a high-pass filter 3 with a cut-off frequency of 1-2 kHz, which is used to offset the signal from the low-frequency interference caused by the machine's drive and a caliper. Next, the signal is fed to the first detector 4 and the first low-pass filter 5, where the OVAC signal is extracted (the AOA signal, Fig. 3) in the entire frequency band passed by the device. From the output of the low-pass filter 5, the signal simultaneously enters three transmission channels, the first of which determines the existence of a cutting process corresponding to logical 1 at the output of the comparator 6 with the dead zone, whose response level is higher than the noise level occurring at the output of the first low-pass filter 5 at no cutting process (signal 306, fig. 3) From the output of the comparator b, the signal is fed to the time delay circuit 7, which serves to neutralize the effect of impulse noise in the absence of cutting. In this case, the noise (time instant ty, fig; 3) caused by accidental strikes on the caliper, pulsed electromagnetic interference, etc., does not pass to the output of the delay circuit 7 (signals 31 and 32, Fig. 3), which does not lead to false triggering of the device.

The signal about the presence of cutting from the output of the comparator 6 also goes to the second input of element 8 AND-NOT, to the second input of which a signal is output from the output of the comparator with an adjustable threshold 19. As a result, the output of element 8 AND-NOT forms a logical signal O, which indicates the occurrence of a steep edge in the cutting process, the level of the signal OVAC, which is 1.5–2 times greater than the original one (signal 36, Fig. 3).

From the output of the low-pass filter, the OVAC signal also enters the second channel of the signal, where it is analyzed in terms of time variation in two parallel circuits, each of which consists of a series-connected storage unit (11, 12), a comparison circuit (13, 14) and a two-threshold comparator (15, 16), respectively. In this case, in the storage units 11 and 12, sequential discrete memorization of the voltage levels at their signal inputs takes place in accordance with the control pulses received from the output of the three-input element And 23 (signal 336, Fig. 3 and signal 416, Fig. 4 ). In the storage unit 11 of the first circuit, information is stored about the overall level of the HVAC signal, and in block 12 of the second circuit, the level of the high-frequency component is stored, since the signal to the input of block 12 comes from the output of the LPF 5 sequentially through the differentiator 18, the second detector 9 and the second LPF 10. From the outputs of the storage units 11 and 12 of both circuits of the second channel, the discretely memorized signals are fed to the inputs of the comparison devices (signal 416, Fig. 4, for the first circuit - similarly), the second inputs of which receive the current values of the HVAC signals (signal41 a, fig. 4).

At the outputs of the comparison circuits 13 and 14, the differences in the voltage of the signals applied to their inputs are formed (signal 42a, FIG.

four). These voltage differences are fed to the signal inputs of the respective two-threshold comparators 15 and 16, the reference inputs of each of which are fed to a portion of the output voltage of the corresponding storage unit, which is 20-40% of the amplitude of the output signal of the latter. In Comparators 15 and 16, two thresholds of -Cop and + Uon are formed (signals 426 and in, Fig. 4, respectively), the voltage interval between which determines the zone of allowable values of changes in signals OVAK during a time equal to the period of the generator 17 pulses (signal 35, Fig. 3) when cutting in the absence of tool breakage.

The outputs of the two threshold comparators 15 and 16 are connected to the inputs of the second element OR 29, the voltage of logical 1 at the output of which signals the output of the OVAC signal either in the first or in the second circuit, or simultaneously in both circuits outside the zone of allowable values. This indicates a significant redistribution of the spectrum of the vibroacoustic oscillations of the AIDS system, which in general is a consequence of changes in the processing conditions and with other constant factors affecting the vibrations of the elastic system of the machine during cutting (stationary cutting, the constancy of the elastic-dissipative properties of the machine and the workpiece) may indicate the fact of a cutting tool failure (signal 34, fig. 4).

The third channel of the signal passage is designed to isolate and record the steep edge of the differential level of the HVAC signal (times t3, W Figs. 3 and 4), control the operation of the storage units 11 and 12, and form, starting from these times, two consecutive intervals, The second (intervals ts -14, ti2 - Хтз, fig. 3) serves as a delay for the transient time that occurs during a breakdown, and during the second interval (intervals t4 - ts, 113 - tn, fig. 3) OVAK on their exit from zones of admissible values, sf assigned for each of these signals to the moments of registration of a steep front (time points ts, ti2, figs. 3 and 4).

To isolate the steep front of the level difference from the output of the low-pass filter 5, the OVAK signal is fed through a differentiator to the input of a comparator with an adjustable threshold 19, to another input of which a voltage proportional to the output voltage of the storage unit 12 is applied,

increased in amplitude 1.5-2 times (signal 336, fig. 3).

The logical 1 signal corresponding to the selected steep edge of the OVAC signal from the output of the comparator 19 passes through the first element OR 21 to the input of setting the zero of the counter 24 pulses and simultaneously enters the input of the AND-NE element 8, to another input of which the logical voltage 1 is already output comparator 6, corresponding to the presence of cutting. A logical O signal appears at the output of the IS-NE 8 element (signal 36, time points t, 3, ti2, Fig. 3) and is fed to the S input of the trigger 20, which results in its inverse output of the logical O signal. (signal 37, times t, s, W, Fig. 3), which prohibits the passage of pulses from the generator 17 through the three-input element AND 23 (time intervals t3 - ts, ti2 - ti4, Fig. 3) to the control the inputs of the storage units 11 and 12, which determines the preservation of information about the levels of signals OVAK from the moment of registration of the steep front at the time 4TG At: 5TG, where Tg

-period generator period. The prohibition of the passage of pulses is also carried out by the logic signal O from the output of the time delay circuit 7 (signal 32, Fig. 3), which ensures the storage of the levels of OVAC signals in the intervals between the cutting intervals (te-tn, tis-tie, Fig. 3) ,

At times ts and ti2 (Fig. 3), a logical signal 1 appears at the direct output of flip-flop 20, which is fed to the input of the first element AND 22, to the other input of which pulses are fed from the generator 17. These pulses pass through the element AND 22 (signal 38, fig. 3), go to the counting input of the pulse counter 24, at the output of which information in a binary code appears about the number of pulses transmitted to its input. This information is then fed to the input of the decoder 25, at each of the terminals of which a signal 1 appears when a pulse 24 is passed to the input of the counter corresponding to this output.

The signals from the second to fourth outputs of the decoder 25 are fed to the input of the three-input element OR 26, at the output of which from the beginning of the second pulse to the beginning of the fifth, starting from the times tz and t2 of FIG. 3, a time interval is formed with a logic level 1 ( signal 39, t4 intervals

-ts, From - ti4, fig, 3), which provides an analysis of the levels of signals OVAK only in specified time intervals (t4 - ts, ti3 -in, Fig. 3), which increases the accuracy of

the definition of the cutting tool breakage, the result of analyzing the location of the OVAC signals in the zones of acceptable values as a signal from the output of the second element And 27

(signal 40, fig. 3) enters the machine control system 28, which issues a command to turn off the main drive drive and retract the caliper.

The first output of the decoder 26 is not active, therefore the time intervals (ts - t4, ti2 - ti3, fig. 3) serve as a delay to eliminate the effect of the transient process occurring in the event of a breakdown on the analysis of the presence of OVAC signals in the zones of acceptable values. The time of the transient after a breakdown in the elastic system during processing is determined by its specific dynamic state. This imposes certain conditions on the choice of frequency.

0 generator 17 pulses, namely, the longer the time of any transition process in an elastic system, which can be estimated experimentally, the longer must be the period of the pulse generator, with

5 This should satisfy the condition Tr, Tr, where Tr is the time of the transition process in the AIDS system, determined experimentally for each type of machine.

At the moment of arrival of the fifth pulse (time point ts, ti4, fig. 3), the corresponding output of the decoder appears at a signal of logical 1 and is fed to the input of the setting O of the trigger 20 (K-input), which transfers the trigger 20 to the initial ( zero) condition. At the inverse output of the trigger 20, a logical 1 signal appears, which through the first element OR 21 is fed to the input of the O installation of the counter 24, which results in the appearance of the decoder

0 25 of the logical O signal (times ts, ti4, fig. 3).

The circuit returns to the pending state of the next OVAC signal level.

5B, an OVAC level analysis is performed simultaneously on the overall signal level (in the first circuit of the second signal transmission channel) and on the OVAC level in the high-frequency region of the spectrum (in the second signal transmission circuit). In the known device, only the general level of this signal is analyzed (in the whole frequency band transmitted by the device) and the high-frequency region of the spectrum is extracted.

5 by sending an OVAK signal through the differentiator to the comparator to determine the steep front of the signal level difference, i.e. the expected moment of occurrence of a breakdown. In the proposed device introduced additionally sequentially

connected to the output of the differentiator, the second detector and the second low-pass filter, which allowed to receive the OVAC signal of the high-frequency region of the spectrum, and together with the known signal transmission circuit: a storage unit — a comparison circuit — a comparator, as well as an additional second element, OR, to be combined into one channel of both circuits, The initial positive properties of the known device are enhanced. At the same time, as a result of the cutting tool breakage due to the redistribution of the vibroacoustic spectrum, the overall level of the OVAC signal may not change or change slightly.

Additional analysis of the high-frequency region of the spectrum due to the organization of the second signal transmission circuit allows fixing not only global faults when, for example, a loss of contact of the instrument with the workpiece is observed, but also its minor chips and chipping. This improves the accuracy of damage detection and the reliability of the device.

The proposed device implements the function of storing information about the magnitude of the OVAK signal levels in the intervals between cutting (interval te - tio, fig. 3), which is not known, which allows reliably fixing the breakage at the moment the tool is embedded in the part, as well as in intermittent cutting modes. This is ensured by introducing a new element - a three-input element AND 23 controlling the recording of information into the storage units 11 and 12 and connecting one of its inputs to a comparator with the dead zone b via delay circuit 7 and time (Fig. 1). At the end of the next processing section (time instants te, 115, figs. 3 and 4), a logic O signal (signal 32, fig. 3) appears at the output of the delay circuit 7, which ensures the termination of control pulses through element 23 from the generator 17 to the storage units 11 and 12. Thus, when stopping the cutting, the information on the level of HVAC in the previous pass in the device is retained until the next pass.

FORUMAWLAH AND ISLANDS

A device for detecting a cutting tool failure, comprising a vibration transducer connected in series, an amplifier, a high-pass filter, a first detector, a first low-pass filter, and a control system and three channels of signal passing, the first of which contains a comparator connected in series with a dead zone, the input connected to the output of the first low pass filter, and the time delay circuit, the second channel contains

5 two parallel circuits, in each of which a storage unit, comparison circuits and a two-threshold comparator are connected in series, the other input of which is connected to the output of the storage

0 block, while another input of the comparison circuit is connected to the input of the storage unit of each circuit, respectively, and the input of the storage unit of the first circuit is connected to the output of the first low-pass filter,

5, the third channel contains a pulse generator, a differentiator, the input of which is connected to the output of the first low-pass filter, and a series-connected element IS-NOT, IK-trigger, to the inverse output

0 of which is connected by one input the first element OR, and to the direct output is the first element AND, a series-connected pulse counter, a decoder and a three-input element OR, and the second input

5 of the first element OR is connected to the first input of the element NAND, and the output is connected to the input of the zero setting of the pulse counter, the output of the generator of rectangular pulses is connected to another input of the first element AND,

0 one of the outputs of the decoder is connected to the K-input of the trigger, and the input of the pulse counter

- to the output of the first element, which is so that, with the aim of expanding technological capabilities by increasing accuracy and reliability in operation, as well as increasing adaptability to changes in cutting conditions in the PMG, it is equipped with a comparator with an adjustable threshold, the reference input of which is connected to the output

0 storage unit of the second circuit, and the output

- to the first input of the element IS-NOT, connected in series by the second detector and the second low-pass filter, the output of which is connected to the input of the storage unit of the same circuit, and the input of the second detector in parallel is connected to the signal input of the comparator with the second element OR whose inputs are connected to

0 outputs of two-threshold comparators, a three-input element I, the first input of which is connected to the inverse output of the trigger, the second to the output of the time delay circuit, the third to the output of the generator 5 straight-angle pulses, and the output in parallel to the control inputs of the storage blocks, the second element I , the first input of which is connected to the output of the second element OR, the second input. to the output of the three-input element OR, and the output to the input of the control system, and the output of the comparator with the non-sensitive zone is the second input of the element AND-NOT luchen to nosti.

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Claims (1)

Claim A device for determining a cutting tool breakdown, comprising a vibration converter, an amplifier, a high-pass filter, a first detector, a first low-pass filter, and a control system and three signal transmission channels, the first of which contains a comparator with a dead band, an input connected to the output of the first low-pass filter, and a time delay circuit, the second channel contains two parallel circuits, in each of which a learning unit, a comparison circuit and a two-threshold comparator, the other input of which is connected to the output of the storage unit, while the other input of the comparison circuit is connected to the input of the storage unit of each circuit, respectively, and the input of the storage unit of the first circuit is connected to the output of the first low-pass filter, the third channel contains a pulse generator, a differentiator, the input of which is connected to the output of the first low-pass filter, and series-connected element NAND, IK-trigger, to the inverse output of which is connected by one input the first element is AND, and to the direct output is the first element AND, sequentially connected pulse counter, decoder and three-input OR element, and the second input of the first OR element is connected to the first input of the AND-NOT element. and the output is to the zero-pulse counter input, the output of the square-wave generator is connected to the other input of the first AND element, one of the decoder outputs is connected to the K-input of the trigger, and the pulse counter input - to the output of the first element And, with the fact that, in order to expand technological capabilities by increasing the accuracy and reliability of the work, as well as increasing adaptability to changes in cutting conditions in the GPM, it is equipped with a comparator with an adjustable threshold, the reference input of which is connected to the output of the storage unit of the second circuit, and the output - to the first input of the AND-NOT element connected in series with the second detector and the second low-pass filter, the output of which is connected to the input of the storage unit of the same circuit, and the input of the second detector is connected in parallel to the signal input of the comparator with an adjustable threshold and the output of the differentiator, the second element OR whose inputs are connected to the outputs of two-threshold comparators, a three-input element And, the first input of which is connected to the inverse output of the trigger, the second to the output of the time delay circuit, the third to the output of the gene a square-wave pulse generator, and the output is connected in parallel to the control inputs of the storage units, the second AND element, the first input of which is connected to the output of the second OR element, the second input - to the output of the three-input OR element, and output 11 - to the input of the control system, and the output of the comparator with the deadband, the second input of the AND-NOT element is connected to the note. Figure 1