Simple and practical cutter damage monitoring device

Abstract

The utility model relates to a cutter damage monitoring device for a numerical control machine tool, in particular to a simple and practical cutter damage monitoring device, which comprises an alternating current transmitter, a vibration sensor and a monitoring control circuit board. The vibration sensor is used for collecting vibration amplitude of a spindle bearing part when a machine tool works, and the monitoring control circuit board is the core of the whole device. The main shaft motor vibration monitoring device is composed of a 555 timer, three relays, an operational amplifier and a plurality of components and is responsible for monitoring the magnitude of current and the amplitude of vibration of a main shaft motor, and if the magnitude and the amplitude exceed a set threshold value, an alarm is output. According to the device, major hidden dangers are completely eradicated, and in an automatic factory without supervision, the product quality can be guaranteed, and the machine tool can be prevented from being damaged. And the components of the whole device are all products with high reliability and low price, so that the cost control is very low, the practicability is strong, and the device is more suitable for transformation services of small and medium-sized enterprises.

Description

TECHNICAL FIELD

[0001] The utility model relates to a numerical control machine tool tool breakage monitoring device, concretely to a simple and practical tool breakage monitoring device, which is a device capable of timely discovering accidental breakage of a tool during machining of a numerical control machine tool and applied to the industrial field. BACKGROUND

[0002] Numerical control machine tools are an important component of intelligent manufacturing and have the advantages of high automation, high production efficiency and stable quality and are widely used in the fields of aviation, aerospace, automobiles, electronics and machinery. At present, many factories configure automatic feeding and discharging systems to numerical control machine tools in order to save labor costs and improve efficiency, so that one person can supervise dozens of machine tools.

[0003] However, in order to realize true "unmanned" and reduce human intervention, many practical problems also need to be considered. In addition to designing and installing an automatic feeding and discharging system, a machine tool tool breakage monitoring function is also essential. During automatic machining of a numerical control machine tool, a tool may accidentally break, which will inevitably cause the cutting load to rapidly increase if the operator does not discover it in time. The spindle and tool servo shaft will bear a large load, which may cause the product to be scrapped, or the machine tool mechanical part to be damaged and cause a larger accident. Therefore, in order to realize a truly "unmanned" factory and make the numerical control machine tool play a greater efficiency, it is necessary to consider how to solve the problem of monitoring tool breakage during machining.

[0004] At present, some numerical control machine tools have added a tool detector function, which can not only compensate for normally worn tools, but also regularly detect tool breakage. However, this function of regularly detecting tool breakage is preset in advance and is executed according to the programmed time. It cannot monitor the tool in real time, and tool breakage often occurs randomly. At this time, this function is invalid, causing the product to be scrapped or the machine tool to be damaged. If the function of real-time monitoring of tool breakage is added, such accidents can be avoided. SUMMARY

[0005] The utility model discloses in order to solve the problem that the existing numerical control machine tool cannot monitor tool breakage in real time, provides a simple and practical tool breakage monitoring device, and eliminates major hidden dangers. In an unmanned automated factory, product quality can be guaranteed and the machine tool can be prevented from being damaged.

[0006] The utility model discloses the following technical scheme is realized: a simple and practical tool breakage monitoring device, including alternating current current transmitter and monitoring control circuit board, including delay circuit and detection circuit in monitoring control circuit board,

[0007] The delay circuit includes 555 timer U2, the 1 pin of 555 timer U2 is grounded, the 2 pin and the 6 pin are connected, the 3 pin is grounded through the coil of the first relay K1, the 4 pin and the 8 pin are connected, the 6 pin is connected with one end of the first regulating potentiometer RP1 through the seventh resistor R7, the other end of the first regulating potentiometer RP1 and the regulating end are grounded, the 8 pin is connected with one end of the first capacitor C1, the other end of the first capacitor C1 is connected with the 6 pin, the 8 pin is also connected with the positive power supply through the normally open contact of the second relay K2, the coil of the second relay K2 is connected with the main shaft rotation signal.

[0008] The detection circuit includes the first rectifier circuit, the input end of the first rectifier circuit is connected with the first resistor R1, the input end of the first rectifier circuit is connected with the output of the alternating current transducer, the positive output end of the first rectifier circuit is connected with one end of the second resistor R2, the other end of the second resistor R2 is connected with one end of the third resistor R3, the other end of the third resistor R3 is connected with the negative output end of the first rectifier circuit and grounded, the 3 pin of the operational amplifier U1A is connected with the positive power supply through the fourth resistor R4, the 3 pin is also connected with the negative power supply through the second regulating potentiometer RP2, the 2 pin is connected with one end of the third resistor R3 through the normally open contact of the first relay K1, the 1 pin is connected with the base of the PNP transistor Q1 through the sixth resistor R6, the emitter of the PNP transistor Q1 is connected with the positive power supply and also connected with the base through the fifth resistor R5, the collector of the PNP transistor Q1 is connected with the ground of the coil of the third relay K3; the normally open contact of the third relay K3 is connected in series in the alarm circuit.

[0009] The simple and practical tool breakage monitoring device further includes a vibration sensor, and the detection circuit further includes a second rectifier circuit, the input end of the second rectifier circuit is connected with the eighth resistor R8, the input end of the second rectifier circuit is connected with the output of the vibration sensor, the positive output end of the second rectifier circuit is connected with one end of the ninth resistor R9, the other end of the ninth resistor R9 is connected with one end of the tenth resistor R10, the other end of the tenth resistor R10 is connected with the negative output end of the second rectifier circuit and grounded, the 5 pin of the operational amplifier U1B is connected with the positive power supply through the eleventh resistor R11, the 5 pin is also connected with the negative power supply through the third regulating potentiometer RP3, the 6 pin is connected with one end of the tenth resistor R10 through the normally open contact of the first relay K1, the 7 pin of the operational amplifier U1B is connected with the base of the PNP transistor Q2 through the thirteenth resistor R13, the emitter of the PNP transistor Q2 is connected with the positive power supply and also connected with the base through the twelfth resistor R12, the collector of the PNP transistor Q2 is connected with the ground of the coil of the third relay K3.

[0010] The alternating current transducer is connected in series in the power cable of the main shaft motor, and the phase current of the main shaft motor is detected in real time; the vibration sensor is installed at the main shaft bearing installation position of the machine tool, and is used for detecting the vibration condition of the main shaft in real time; when the machine tool numerical control system sends a start signal to the main shaft, the main shaft starts to rotate, and at the same time, the second relay K2 is attracted, and the 555 timer U2 is powered on to start delay. When the main shaft accelerates to the rated speed, the timing time of the 555 timer U2 arrives, the first relay K1 is attracted, and the detection circuit starts to work. At this time, the alternating current transducer and / or the vibration sensor feed back the collected signals to the monitoring control circuit board, and the two kinds of input signals are compared with the set threshold value. If the main shaft motor working current is normal and the main shaft vibration is normal, the collected signal voltage is less than the set voltage of the comparator, the comparator output is high level, the transistor is cut off, the third relay K3 is not attracted, and the alarm output is not output. If the tool suddenly breaks during the machining process of the machine tool, the load will inevitably increase, the main shaft motor working current will suddenly increase, and the main shaft vibration amplitude will also increase. At this time, if one of the collected signal voltages is greater than the set voltage of the comparator, the comparator output is low level, the PNP transistor Q1 or Q2 is turned on, the third relay K3 is turned on and kept, and the alarm output is output. The alarm signal can be connected to the emergency stop function of the numerical control system, so that the machining is stopped in time, and a larger accident is avoided, and the design purpose of monitoring the tool breakage in real time is achieved.

[0011] The collector of the PNP transistor Q1 is also connected with the anode of the first crystal diode D1, and the cathode of the first crystal diode D1 is connected with one end of the second resistor R2; the collector of the PNP transistor Q2 is also connected with the anode of the second crystal diode D2, and the cathode of the second crystal diode D2 is connected with one end of the ninth resistor R9. After the PNP transistor Q1 or the PNP transistor Q2 outputs a high level, the alarm output is output, then the high level is continuously added to the negative end (2 pins, 6 pins) of the comparator through the first crystal diode D1 or the second crystal diode D2, the comparator always outputs a low level, the PNP transistor Q1 or the PNP transistor Q2 is turned on, and the alarm continuous output is maintained.

[0012] The utility model has the following advantages:

[0013] 1, rigorous design thought

[0014] The tool breakage monitoring is realized through an external sensor and a simple monitoring control circuit, which is a more practical method at present, is simple to debug and is more convenient to realize.

[0015] 2, novel tool breakage monitoring circuit design

[0016] The design of the tool breakage monitoring control circuit board is to select a detection circuit composed of one timer, three relays, one operational amplifier and a plurality of components.

[0017] 3. Strong adaptability

[0018] The main shaft motor starting delay detection timer is designed on the monitoring control circuit board, and the delay time can be conveniently adjusted; the threshold values of the current size and the vibration amplitude are also designed with adjusting potentiometers, and such design is more suitable for the working modes of most machine tools on the market and is more convenient for machine tool manufacturers to install and transform.

[0019] 4. Simple and reliable, low cost

[0020] The components of the whole device are all selected from products with high reliability and relatively low cost, and the cost control is very low, and the practicality is strong, and it is more suitable for small and medium-sized enterprise transformation services.

[0021] 5. Strong universality

[0022] The whole device can also be installed on other automatic equipment as abnormal detection of various motors. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a circuit principle diagram of the device. DETAILED DESCRIPTION

[0024] Whether the numerical control machine tool is clamped with a workpiece or a tool, the current and the vibration amplitude of the main shaft can reflect the change of the cutting load in real time. Therefore, the working current size of the main shaft motor of the numerical control machine tool and the amplitude of the main shaft vibration are monitored in real time, and if the tool is accidentally broken during the machining process, the cutting load will inevitably increase rapidly, and if the alarm threshold value is reached, the monitoring device will automatically feed back to the numerical control system of the machine tool, so as to rapidly pause the machining and perform human intervention.

[0025] A simple and practical tool breakage monitoring device mainly consists of three parts:

[0026] Part one: The AC current transmitter monitors the working current of the main shaft motor of the numerical control machine tool. An AC current transmitter is connected in series in the power cable of the main shaft motor to detect the phase current of the main shaft motor in real time. Since the current is relatively large when the main shaft motor starts, false alarm is easy to occur, so the monitoring device is internally provided with an adjustable delay function to avoid detection during the starting period of the main shaft motor. The threshold value of the alarm is also adjustable, and the threshold value of the alarm is adjusted by increasing the cutting force to try to cut the workpiece and trigger the alarm.

[0027] Part two: vibration sensor monitors the machine spindle mechanical vibration. With a magnetic vibration sensor adsorbed in the spindle bearing installation part, it is used to detect the spindle vibration in real time. The threshold of alarm is also adjustable, and the threshold of alarm is adjusted by increasing the cutting force to try cutting workpiece to trigger alarm.

[0028] Part three: monitoring control circuit board. It is built-in current signal conversion voltage signal circuit, comparator, relay, delay circuit and other components. It mainly converts the current signal sent by the AC current transmitter and vibration sensor into voltage signal, and compares it with the set reference voltage. If it exceeds the set value, it outputs a relay signal for alarm output.

[0029] The device structure and function of a tool breakage monitoring device:

[0030] (1) AC current transmitter

[0031] The device is designed with an AC current transmitter, which is used to collect the phase current of the spindle motor when the numerical control machine tool is working, and outputs a current signal of 4-20mA according to the actual current size.

[0032] (2) Vibration sensor

[0033] The device is designed with a vibration sensor, which is used to collect the vibration amplitude of the spindle bearing part when the machine tool is working, and outputs a current signal of 4-20mA according to the actual vibration amplitude.

[0034] (3) Monitoring control circuit board

[0035] The monitoring control circuit board is the core of the whole system. It is composed of 1 555 timer (model SA555), 3 relays, 1 operational amplifier (model LF353) and a number of components, responsible for monitoring the size of the spindle motor current and the amplitude of the vibration, and if it exceeds the set threshold, it will alarm output.

[0036] Specifically, the monitoring control circuit board includes 555 timer U2, first relay K1, second relay K2, third relay K3, operational amplifier, first rectifier circuit and second rectifier circuit,

[0037] The 1 pin of 555 timer U2 is grounded, the 2 pin and the 6 pin are connected, the 3 pin is grounded through the coil of the first relay K1, the 4 pin and the 8 pin are connected, the 6 pin is connected through the seventh resistor R7 and one end of the first adjustable potentiometer RP1, the other end of the first adjustable potentiometer RP1 and the adjustment end are grounded, the 8 pin is connected with one end of the first capacitor C1, the other end of the first capacitor C1 is connected with the 6 pin, the 8 pin is also connected with +DC12V through the normally open contact of the second relay K2, the coil of the second relay K2 is connected with the spindle rotation signal;

[0038] The input end of the first rectifier circuit is connected with a first resistor R1, which is a sampling resistor. The input end of the first rectifier circuit is connected with the output of the alternating current transducer. The positive output end of the first rectifier circuit is connected with one end of a second resistor R2. The other end of the second resistor R2 is connected with one end of a third resistor R3. The other end of the third resistor R3 is connected with the negative output end of the first rectifier circuit and grounded. The 3 pin of the operational amplifier U1A is connected with +DC12V through a fourth resistor R4. The 3 pin is also connected with -DC12V through the second regulating potentiometer RP2. The 2 pin is connected with one end of the third resistor R3 through the normally open contact of the first relay K1. The 8 pin of the operational amplifier U1A is connected with +DC12V. The 4 pin is connected with -DC12V. The 1 pin is connected with the base of a PNP transistor Q1 through a sixth resistor R6. The emitter of the PNP transistor Q1 is connected with +DC12V and also connected with the base through a fifth resistor R5. The collector of the PNP transistor Q1 is connected with the ground of the coil of the third relay K3 and also connected with the anode of a first crystal diode D1. The cathode of the first crystal diode D1 is connected with one end of the second resistor R2.

[0039] The input end of the second rectifier circuit is connected with an eighth resistor R8, which is a sampling resistor. The input end of the second rectifier circuit is connected with the output of the vibration sensor. The positive output end of the second rectifier circuit is connected with one end of a ninth resistor R9. The other end of the ninth resistor R9 is connected with one end of a tenth resistor R10. The other end of the tenth resistor R10 is connected with the negative output end of the second rectifier circuit and grounded. The 5 pin of the operational amplifier U1B is connected with +DC12V through an eleventh resistor R11. The 5 pin is also connected with -DC12V through the third regulating potentiometer RP3. The 6 pin is connected with one end of the tenth resistor R10 through the normally open contact of the first relay K1. The 7 pin of the operational amplifier U1B is connected with the base of a PNP transistor Q2 through a thirteenth resistor R13. The emitter of the PNP transistor Q2 is connected with +DC12V and also connected with the base through a twelfth resistor R12. The collector of the PNP transistor Q2 is connected with the ground of the coil of the third relay K3 and also connected with the anode of a second crystal diode D2. The cathode of the second crystal diode D2 is connected with one end of the ninth resistor R9. The normally open contact of the third relay K3 is connected in series in the alarm circuit.

[0040] Working principle:

[0041] (1) The role of the timer:

[0042] The monitoring control circuit board is powered by ±DC12V. After the device is powered on, the detection circuit of the monitoring control circuit board does not start working under the action of the normally open contact of the first relay K1, but waits for the arrival of the "main shaft rotation signal". The main shaft of the numerical control machine tool starts to start, and the numerical control system will send a "main shaft rotation signal" to turn on the second relay K2. At this time, DC12V starts to power the 555 timer U2. After the 555 timer U2 is powered on, it starts to delay according to the value set by the first adjusting potentiometer RP1. When the delay time arrives, the 3 pin of the 555 timer U2 outputs high level, making the first relay K1 conductive, and the detection circuit starts to work. The delay time of the 555 timer U2 is determined by the start-up acceleration time of the machine tool main shaft. Since this time is not very strict, the delay output time of the 555 timer U2 is generally adjusted to about 10 seconds to ensure that the main shaft motor start-up time is less than the delay time, preventing excessive start-up current and false alarms.

[0043] (2) Conversion of current signal:

[0044] In order to prevent interference, both the current and vibration detection sensors use current type sensors, which output 4-20mA current signals. Therefore, the current signal input to the monitoring control circuit board needs to be converted into a voltage signal. Therefore, the device is designed with a current conversion circuit. The first resistor R1 and the eighth resistor R8 are sampling resistors for voltage signals, which are then converted into voltage signals through a rectifier circuit for more convenient comparison.

[0045] (3) Comparison circuit:

[0046] U1 is an operational amplifier used as a comparator in the monitoring control circuit board. The 3 pin of U1A and the 5 pin of U1B are the set threshold values of the two comparators, which can be adjusted by the second adjusting potentiometer RP2 and the third adjusting potentiometer RP3. The two input voltage signals are compared with the set threshold value. If it is less than the set threshold value, the comparator outputs high level, and the PNP transistor Q1 and the PNP transistor Q2 are cut off, and the third relay K3 is not attracted. If one of the input voltage signals is greater than the set threshold value, the comparator outputs low level, the PNP transistor Q1 or the PNP transistor Q2 is turned on, the third relay K3 is attracted, and the alarm output is generated. At the same time, the circuit is self-locked through diode D1 or D2 to keep the transistor in the on state and the alarm continuously outputs. After human intervention, the "main shaft rotation signal" is stopped, the 555 timer U2 stops supplying power, the normally open contact of the first relay K1 is disconnected, the comparator outputs high level, the transistor is cut off, the third relay K3 is disconnected, and the alarm is reset.

[0047] Work flow:

[0048] When the spindle starts to rotate after the start signal from the machine tool numerical control system, the second relay K2 is attracted, and the 555 timer U2 is powered on to start the delay. When the spindle accelerates to the rated speed, the 555 timer U2 timing time is up, the first relay K1 is attracted, and the monitoring circuit starts to work. At this time, the AC current transducer and the vibration sensor will feed back the collected signals to the monitoring control circuit board, and the two input signals are compared with the set threshold value. If the spindle motor working current is normal and the spindle vibration is normal, the collected signal voltage is less than the set voltage of the comparator, the comparator output is high, the transistor is cut off, the third relay K3 is not attracted, and the alarm output is not output. If the tool suddenly breaks during the machining process of the machine tool, it will inevitably cause the load to increase, the spindle motor working current will suddenly increase, and the spindle vibration amplitude will also increase. At this time, if one of the collected signal voltages is greater than the set voltage of the comparator, the comparator output is low, which causes the PNP transistor Q1 or Q2 to conduct, causing the third relay K3 to conduct and remain, and the alarm output. The alarm signal can be connected to the emergency stop function of the numerical control system, so that the machining is stopped in time to avoid greater accidents and achieve the design purpose of real-time monitoring of tool breakage.

Claims

1. A simple and practical tool breakage monitoring device, characterized by: The application relates to an alternating current transducer and a monitoring control circuit board, wherein the monitoring control circuit board comprises a delay circuit and a detection circuit, The delay circuit comprises a 555 timer U2, the 1 pin of the 555 timer U2 is grounded, the 2 pin and the 6 pin are connected, the 3 pin is grounded through the coil of a first relay K1, the 4 pin and the 8 pin are connected, the 6 pin is connected with one end of a first regulating potentiometer RP1 through a seventh resistor R7, the other end of the first regulating potentiometer RP1 and a regulating end are grounded, the 8 pin is connected with one end of a first capacitor C1, the other end of the first capacitor C1 is connected with the 6 pin, and the 8 pin is also connected with the positive power supply through the normally open contact of a second relay K2, and the coil of the second relay K2 is connected with a main shaft rotation signal; The detection circuit comprises a first rectifier circuit, the input end of the first rectifier circuit is connected with a first resistor R1, the input end of the first rectifier circuit is connected with the output of the alternating current transducer, the positive output end of the first rectifier circuit is connected with one end of a second resistor R2, the other end of the second resistor R2 is connected with one end of a third resistor R3, the other end of the third resistor R3 is connected with the negative output end of the first rectifier circuit and grounded, the 3 pin of an operational amplifier U1A is connected with the positive power supply through a fourth resistor R4, the 3 pin is also connected with the negative power supply through a second regulating potentiometer RP2, the 2 pin is connected with one end of the third resistor R3 through the normally open contact of the first relay K1, the 1 pin is connected with the base of a PNP triode Q1 through a sixth resistor R6, the emitter of the PNP triode Q1 is connected with the positive power supply and also connected with the base through a fifth resistor R5, and the collector of the PNP triode Q1 is grounded through the coil of a third relay K3; the normally open contact of the third relay K3 is connected in series in an alarm circuit.

2. A simple and practical tool breakage monitoring device according to claim 1, characterized in that: The application further comprises a vibration sensor, and the detection circuit further comprises a second rectifier circuit, the input end of the second rectifier circuit is connected with an eighth resistor R8, the input end of the second rectifier circuit is connected with the output of the vibration sensor, the positive output end of the second rectifier circuit is connected with one end of a ninth resistor R9, the other end of the ninth resistor R9 is connected with one end of a tenth resistor R10, the other end of the tenth resistor R10 is connected with the negative output end of the second rectifier circuit and grounded, the 5 pin of an operational amplifier U1B is connected with the positive power supply through an eleventh resistor R11, the 5 pin is also connected with the negative power supply through a third regulating potentiometer RP3, the 6 pin is connected with one end of the tenth resistor R10 through the normally open contact of the first relay K1, the 7 pin of the operational amplifier U1B is connected with the base of a PNP triode Q2 through a thirteenth resistor R13, the emitter of the PNP triode Q2 is connected with the positive power supply and also connected with the base through a twelfth resistor R12, and the collector of the PNP triode Q2 is grounded through the coil of the third relay K3.

3. A simple and practical tool breakage monitoring device according to claim 2, characterized in that: The collector of the PNP triode Q1 is also connected with the anode of a first crystal diode D1, the cathode of the first crystal diode D1 is connected with one end of the second resistor R2; the collector of the PNP triode Q2 is also connected with the anode of a second crystal diode D2, and the cathode of the second crystal diode D2 is connected with one end of the ninth resistor R9.

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