RU1798042C - Device for testing failure of cutting tool - Google Patents

Abstract

Usage: the field of mechanical engineering, in particular machine tool engineering, for the protection of metal-cutting equipment during part processing in emergency situations associated with the destruction of the cutting tool. Essence: the device contains a series-connected vibration sensor 1, amplifier 2. detector 3, key 4, low-pass filter 5, sample-storage device b, subtractor 7, the subtracting input of which is connected to the output of the low-pass filter 5, and the output to the first the input of the bipolar comparator 8, the second input of which is connected to the scale converter 9, the second two-input element And 10 and the control unit 11. The amplifier 12 with an adjustable coefficient is connected to the output of the vibration sensor 1, and its input is connected to one of the inputs s of the comparator 13, the second input of which is connected to the output of the low-pass filter 5, and the output is connected to the input of the first two-input element And 14, the second input of which through the time delay element 16 is connected to the output of the comparator 15 by the presence of cutting, the signal input of which is connected to the output of the filter 5 low frequencies, and a reference voltage is applied to the reference input. 9 ill. ate with

Description

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The invention relates to mechanical engineering, in particular to machine tool manufacturing, and is intended to protect the metal-cutting equipment of the workpiece in emergency situations associated with the destruction of the cutting tool during machining, and can be used to diagnose the cutting process. . / -.:

The aim of the invention is to increase the reliability of determining the moment of destruction of the cutting tool by eliminating additional recharge; the capacitance of the low-pass filter during bursts of the VAZ signal by replacing the periodic operation of sampling and storing the signal from the output of the low-pass filter with a one-time operation and eliminating the need to adjust the setting value during cutting to form a command to compare the average value of the VAZ signal before and after the burst. signal. ..; /,,. :. .;

The low reliability of determining the moment of destruction of the cutting tool in the prototype is due to the fact that with an arbitrary arrangement in time of the moments of sampling the voltage from the output of the low-pass filter and the beginning of the analysis of the change in its value, performed each time after exceeding the peak value of the signal. For example, a coincidence of these moments is possible, which leads to storing in the sample-storage device the value of the signal acting during the transient period, which differs significantly from the value of the signal corresponding to the normal course of the cutting process and preceding the appearance of a pulse change in the signal. As a result, during the further processing of the signal, an erroneous result will be obtained.

The elimination of the described drawback is achieved by replacing the continuous one-time sampling and storage operation that previously existed in the prototype with a single operation, which is carried out only once in the presence of a sharp increase in the level of the WHA signal and its achievement. setpoint value. This ensures that the signal stored in the sampling and storing device corresponds to the signal from the low-pass filter output, corresponding to the normal course of the cutting process and the previous occurrence of a VAZ signal burst, which is associated either with the destruction of the cutting tool. Or with random disturbances in the AIDS system. In this case, significantly

simplified management of the fetch-storage device.

Reducing the hardware analysis time of the device (reaction time) is ensured by eliminating the recharging of the low-pass filter capacitance during pulsed increases (bursts) of the WHA signal. To do this, a controlled key is inserted between the output of the detector and the input of the low-pass filter. Key 4 is controlled by a single vibrator. When a burst of VAZ signal cp- appears. starts the comparator and starts the one-shot, which for the duration of the burst

the key opens, and the low-pass filter capacitance is thus disconnected from the detector output.

If the burst of the VAZ signal was caused by the destruction of the cutting tool and the VAZ signal therefore decreased, then at

subsequent analysis of changes in voltage on the filter capacitance low

frequencies there is no need to take into account the time

. for which the low-pass filter capacitance would have to be discharged from the voltage due to the burst of the VAZ signal to the voltage preceding the burst. The length of time the key is in the open state is selected within 5-10 ms and depends on the damping properties of a particular elastic system: machine - tool - tool - part. (AIDS) and is determined by the transition time -

process occurring in the system

AIDS with impulse disturbance. . ....-, ...

Adaptation of the device to the type of material being processed is achieved by introducing a floating setpoint instead of

fixed value in prototype. This eliminates the need to adjust the set value during processing of one part, since even in this case signal changes are possible

in magnitude within 20 dB or more.

The need to adjust the setpoint value is caused by the possibility of reducing the VAZ signal to such a value that even with significant pulse

As the signal increases, its peak values cannot exceed the setting value and as a result, it is possible to skip fixing the moment of destruction of the cutting tool. On the other hand, it is possible that the VAZ signal is so large that its peak values, even during the normal course of the processing process, can exceed the setpoint value, which will be a source of false positives.

The foregoing explains the need to adjust the setpoint value for each process step.

Using the average value of the VAZ signal as the setpoint eliminates the need to adjust the setpoint value during processing of one part. Correction of the setpoint value will only be necessary if the type of material being processed is changed.

Fig. 1 is a functional block diagram of the claimed device; in FIG. 2 is a functional diagram of a retrieval-storage device; in FIG. 3 is a functional diagram of a bipolar comparator; in FIG. 4 - electrical diagram of single vibrators; in FIG. 5 is a circuit diagram of a low pass filter; in FIG. 6 is an electrical diagram of a time delay element; on Fig, 7 - waveform from the outputs of the amplifier and low-pass filter; in FIG. 8 is a voltage waveform across a capacitor of a low-pass filter when a VAZ signal burst; in FIG. 9 is a timing diagram of the operation of the device.

The device contains a series-connected vibration sensor 1, amplifier 2, detector 3, key 4, low-pass filter 5, a sampling-storage device 6, a subtracting device 7, the subtracting input of which is connected to the output of the low-pass filter 5, and the output is connected to the first input of the two-pole a comparator 8, the second input of which is connected to a scale converter 9, a second two-input element And 10 and a control unit 11.

An amplifier 12 with an adjustable coefficient is connected to the output of the vibration sensor 1, and its input is connected to one of the inputs of the comparator 13, the second input of which is connected to the output of the low-pass filter 5, and the output to the input of the first two-input element And 14, the second the input of which through the time delay element 16 is connected to the output of the comparator 15 by the presence of cutting, the signal input of which is connected to the output of the low-pass filter 5, and the set voltage is applied to the reference input. ... -. .. .-. .-. /.

The sampling-storage device 6 contains a controlled key 19, a storage capacitor 20 and an operational amplifier

21.. ... . :

The bipolar comparator 8 can be made according to the block diagram shown in FIG. 3. It consists of two conventional comparators, on the inverting inputs of which a reference voltage is supplied, and on the non-inverting inputs, an input voltage is supplied, moreover, it goes to one comparator directly from the output of the subtracting device 7, and to the other comparator through an inverting amplifier with a unit gain factor.

The single vibrators 17 and 18 are made according to the circuit shown in FIG. 4. They are triggered by a pulse of positive polarity with the duration of the front

front not less than 25 ... 100 not. The low-pass filter 5 is made according to the standard circuit shown in FIG. 5.

The time delay element 16 can be performed according to the scheme shown in

FIG. 6. His work is as follows: in the initial state, a negative potential is present at the output of the operational amplifier, i.e. positive input is applied to its inverting input

voltage specified by the divider R4, R5, and at the non-inverting input in the absence of a signal there is a zero potential. When the comparator triggers the presence of cutting 15 (see Fig. 1), a positive potential of 12-13 V is applied to R1, the capacitance C1 starts to charge and after a time determined by a constant time. The voltage on it is compared, and then it will exceed the potential,

defined by the divider R4, R5. In this case, the operational amplifier YES is triggered and a positive potential appears at its output. When the signal disappears at the input of the time element

delay signal at the output YES (changes sign after a time determined by the time constant of the discharge circuit rp RSKB. CI, where Req. R1 + R2 + R3.

The device generates a signal indicating the destruction of the cutting tool under the simultaneous presence of the following two conditions.

The first condition is that the setting removed from the output of the low-pass filter 5 is exceeded by the instantaneous value of the VAZ signal amplified by an amplifier 12 with adjustable gain. The second condition is a relative change in the average value of the VAZ signal

by no less than (25 ... 35)%. This value was obtained after v-analysis of the change in the average VAZ signal associated with the destruction of the cutting tool.

The device operates as follows ..

The VAZ signal from the cutting zone is sensed by vibration sensor 1, amplified by amplifier 2, and also fed to

variable gain amplifier 12. The ratio between the amplification factors of these amplifiers is selected based on the following considerations. In the normal course of the processing process, the VAZ signal, converted into an electrical signal by means of a vibration sensor 1 and amplified by an amplifier 2, has the form shown in FIG. 7a. After it passes through the detector 3, the key 4 and the low-pass filter 5, the average signal value shown in Figs. 76. It should be noted that the time constant of detector 3 is determined by the bandwidth of the information channel of the AIDS system and is selected within (0.1-2) ms. The low-pass filter time constant 5 is associated with the degree of non-stationarity of the WHA signal and is selected within 20-50 ms.

The average value of the WHA signal is used as a setpoint to generate a command using comparator 13 to evaluate the change in the value of the signal from the output of the low-pass filter 5 after a burst of WHA. As can be seen from FIG. 7, the ratio between the average signal value and the maximum instantaneous values is 5-6 times, and when processing difficult materials, this ratio can be 20-25 times, and therefore, to form a setpoint value exceeding the maximum instantaneous values of the VAZ signal. the gain of the amplifier 12 with an adjustable gain should vary from 5 to 25 times depending on the grade of the material being processed. Thus, the setting for generating the comparison command is floating, i.e. varies independently depending on the processing conditions. Forcibly changing the ratio between the average signal value and the maximum instantaneous signal values is necessary only once when changing the brand of the processed material. To this end, the gain of the amplifier 12 is adjusted with an adjustable gain. The command to analyze the change in the signal is generated when the instantaneous value of the VAZ signal amplified by the amplifier 12 with an adjustable gain exceeds the value of the floating setpoint, determined by the voltage value taken from the output of the low-pass filter 5 and corresponding to the current average value of the VAZ signal.

For normal operation of the device, the gain of the amplifier 12 with an adjustable gain is chosen so that the maximum

the instantaneous values of the signal at its output reached a floating value of 1.1 set point only at critical wear of the cutting tool. In addition, from the output of the low pass filter 5, the signal is also fed to

0 one input 15 comparator presence of cutting. A reference voltage Uo is applied to its second input. A cutter comparator 15 is used to enable the device to operate when a cut signal appears. Value

5, the reference voltage U0 is selected so as to surpass interference signals with some margin, i.e., signals not related to the cutting process that occur during rapid movements of the caliper, when the tool turret rotates, etc.

The time delay element 16 delays both the appearance of the signal and its disappearance. Delay

5, the appearance of a signal is necessary in order to avoid false triggering when the cutting tool is cut into the part. This is due to the leading occurrence on the comparator, 13 of the rapidly increasing signal from the output of amplifier 12 with an adjustable gain relative to the averaged signal from the output of low pass filter 5. The amount of delay select-. It is equal to 5-10 ms, because during this time, the signal at the output of the low pass filter 5 manages to take on a steady value. A signal disappearance delay is necessary so that in the case of intermittent cutting in the absence of contact between the cutting tool and the part for this period of time, the operating mode of the device does not change. The delay value is selected to be 0.5-1 s.

The need to introduce a key 4 is to prevent the charging of a capacitor, a low-pass filter 5 when a VAZ signal bursts. This allows a comparison of the average signal before burst and after burst through

0 is the time interval determined only by the duration of the transient process in the elastic AIDS system and the value of the time constant of the low pass filter 5. Voltage change illustrations

5 on the capacitor in the absence and presence of a key is shown in FIG. 8. After a signal surge, a transient occurs in the elastic system of the machine with a duration of 5-10 ms, during which, in the absence of a switch, the voltage across the filter capacitor 5

low frequencies increases to a certain value related to the amplitude of the burst, as shown in FIG. 86. Then, if the signal takes a lower value than before the surge, a decrease in voltage occurs over a time determined by the time constant of the low-pass filter 5. In the presence of a key and its opening at the time of the burst for a time equal to the maximum duration of the transient process, there is no increase in voltage on the capacitor, and after closing the key, the voltage decreases to a new value in a time determined by the filter constant 5 low frequencies. As can be seen from Fig. 8c, a decrease in the voltage U2 on the capacitor of the low-pass filter 5 after a surge in the absence of a key to the initial value Ui occurs during time t3 and, therefore, before this time has passed, it is impossible to give an instruction to analyze the change in the voltage value by capacitor after surge.

Thus, in the presence of key A, there is no need to take into account the time interval tk and, therefore, the total time of apparatus analysis of the device is reduced by this value. A single vibrator is used to control the operation of key A. 17, the opening key when the comparator 13 is triggered.

The one-shot 18 serves to control the operation of the key 19 of the sample-storage device 6. When a signal appears at the output of the one-shot 18, the key 19 of the sample-storage device b opens and the device goes into storage mode for the duration of which the voltage is monitored the low-pass filter capacitor 5 after a surge in the WHA signal relative to the voltage on the same capacitor until a surge occurs. This control is carried out using a bipolar comparator 8, on one input of which the setpoint from the scale converter 9 is received, and on the other - the voltage difference generated by the subtractor from the output of the low-pass filter 5, stored in the sampling-storage device 6 until the appearance surge and current after surge. When the magnitude of the difference in these voltages is greater than the setpoint, the bipolar comparator 8 is triggered. The time taken to carry out the specified control is determined by the duration of the signal from the output of the one-shot 18, triggered by the comparator 13. The signal from the output of the one-shot 18 is supplied as a key 19

sampling-storage devices 6, and to the second two-input element And 10, which, while there are signals at its inputs from the output of the bipolar

comparator 8 and single vibrator 18, generates a pulse supplied to the control unit 11, which generates a command for the control system of the machine to stop the processing and removal of the support in

0 tool change position.

When an amplifier 12 appears at the output with an adjustable burst gain of the VAZ signal, the instantaneous value of which reaches 5 at the output of the low-pass filter 5, the comparator 13 generates a voltage pulse that starts one-shots 17 and 18 with its leading edge. One-shot 17, controls key A produces

0 pulse of duration ti, which opens the key 4 and thereby prevents recharging of the low-pass filter 5 from the burst of the VAZ signal. One-shot 18. used to control the key 19 of the sampling-storage device 6, generates a pulse of duration t2. which at the same time opens the key 19 of the sampling-storage device 6, thereby transferring it to the storage mode., and also serves on one

0 from the inputs of the two-input element And 10. For the duration of the pulse duration t2 from the output of the one-shot 18, the voltage at the storage capacitor 20 does not change, because its load is operating

5, an amplifier 21 is turned on in repeater mode and has a large input impedance.

The voltage value at the output of the sample-storage device 6 during the time interval t2 is equal to the voltage value that was at the output of the low-pass filter 5 before the burst of the VAZ signal. At the output of the subtractor 6, during the interval of time ti 5, the voltage is zero, because at both of its inputs there are equal voltages. In this case, the voltage from the scale converter 9, the value of which is Ше, will be applied to the reference input of the bipolar comparator 8, where k is the proportionality coefficient equal to 0.25-0.35, and the value of which will be constant for a time interval equal to the duration of pulse 5 of pulse t2 generated by the one-shot 18, at the second input of the bipolar comparator 8, during the time interval ti, there will be a zero voltage taken from the output of the subtractor 7.

After the time interval ti has elapsed, the switch 4 is returned to its initial (closed) position and the voltage at the output of the low-pass filter 5 begins to change in proportion to the change in the input signal of the VAZ. At the same time, a constant-level stored voltage is applied to one input of the subtractor 7, and a variable from the output of the low-pass filter 5 is supplied to the second input. In the case of a decrease in the voltage from the output of the low-pass filter 5 at the output of the subtractor 7, a positive voltage appears, and if it increases, it is negative, and in both cases the nature of the change in the voltage at the output of the subtractor 7 will correspond to the nature of the change in voltage The output of the low pass filter is 5. If during the time t2 of the action of the pulse at the output of the one-shot 18 (that is, with the switch 19 open), the voltage U generated by the subtractor 7 does not exceed the threshold voltage of the bipolar comparator 8 set using the scale converter 9, then at the output of the bipolar comparator 8, a voltage equal to zero is stored, and after the key 19 is returned to its original (closed) position, the output of the subtractor 7 will have a zero signal. If the voltage U exceeds the threshold of the bipolar -comparator 8, the latter will work and feed a logical unit to the first input of the AND gate 10; and since at its second input, at this time a logical unit c is already present. single-vibrator 18, then the control unit 11 will be supplied with the voltage necessary for this block to generate a signal sent to the CNC system of the metal-cutting equipment to stop the feed movement,

The reaction time of the device according to the invention is determined by the pulse width of a single-shot 18, which is chosen equal to the sum of the durations of the transient processes in the elastic system of the machine after a pulse disturbance causing a burst of the VAZ signal and in the low-pass filter 5 to establish a new voltage value at its output.

When using the proposed device provides:

increasing the reliability of determining the moment of destruction of the cutting tool;

simplification of setup and operation

devices that allows you to expand the scope

its use, including multi-station

service and unmanned technology;

faster termination of the process

processing during the destruction of the cutting tool, and, as a result, reducing the severity of the consequences arising from the destruction of the tool and the continued movement of the caliper.

Claims (1)

The claims A device for detecting a cutting tool failure, comprising a vibration sensor, an amplifier and a detector in series, as well as a low-pass filter, a sample-storage unit, a subtracting unit, a first comparator, a control unit and a second comparator, a time delay circuit and a first element And connected in series. with the fact that, in order to increase the reliability of determining the moment of destruction of the cutting tool, a key is inserted into the device, included between the output of the detector and the input of the low-pass filter, the output connected to the first input the second comparator, to the second input of which the reference voltage is supplied, and with the block, sample-storage, the output of which is connected to the input of the subtracting block and to the input of the scale converter, the output which is connected to the reference input of the first comparator, the second input of which is connected to the output of the subtracting unit, the input of which is connected to the output of the low-pass filter, an amplifier with an adjustable gain connected to the output of the sensor, the third comparator, the first input of which is connected to the output of the low-pass filter , the second input - to the output of the amplifier with an adjustable gain, and the output - to the second input of the first element And, the first and second single vibrators, the inputs of which are connected to the output of the first element And, at than the output of the first comparator is designed to control key, and the output of the second one-shot - block sampling-storage, in addition, the output of the second one-shot is connected to one of the inputs of the second element And, the second input of which is connected to the output of the first comparator, and the output is connected to the control unit. Uon Ugx. U&K R FIG 2 FIG. -5 hUon willow i. FIG. 4 i Ug OH WITH