Wire cutting short circuit detection protection circuit

Abstract

The utility model discloses a kind of wire cutting short circuit detection protection circuit, including interelectrode voltage sampling and isolation module, voltage comparison module and MCU, interelectrode voltage sampling and isolation module includes photo-coupler N1, the potential of workpiece and molybdenum wire is sampled respectively in two input ends of photo-coupler N1, the voltage signal V-sense of the collector of photo-coupler N1 is input to the input end of voltage comparison module;Inter-electrode voltage is sampled using interelectrode voltage sampling and isolation module, and threshold voltage generated by threshold voltage generation circuit is compared, whether short-circuit state appears according to the digital signal indication of comparator output by MCU, the output of discharge pulse is cut off when short-circuit appears, realizes the closed-loop control of molybdenum wire processing, inter-electrode voltage can be monitored in real time, to eliminate short-circuit.

Description

Technical Field

[0001] This utility model relates to the field of short circuit detection and protection circuit technology, and in particular to a wire cutting short circuit detection and protection circuit. Background Technology

[0002] In the wire electrical discharge machining process, under ideal conditions, the gap between electrodes is usually maintained between a few micrometers and tens of micrometers, and the continuous pulse discharge current and voltage are maintained within a stable range.

[0003] Electrolytic corrosion generated during the cutting process sometimes prevents the wire from breaking quickly, so short circuit detection is crucial. When a short circuit is detected, the pulse discharge should be turned off in time and feedback should be sent to the control system to allow the short circuit to be eliminated.

[0004] During normal processing or no-load conditions, the inter-electrode voltage is relatively high, ranging from tens to over one hundred volts. During a short circuit, it is generally less than ten volts. Therefore, by monitoring the inter-electrode voltage in real time and setting a "short circuit threshold voltage" for comparison, it is possible to determine whether a short circuit has occurred. Utility Model Content

[0005] This invention provides a wire cutting short circuit detection and protection circuit, which uses inter-electrode voltage sampling, optocoupler isolation, voltage comparison, and feedback MCU closed-loop control to monitor the inter-electrode voltage in real time in order to eliminate short circuits.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0007] A wire EDM short-circuit detection and protection circuit includes an inter-electrode voltage sampling and isolation module, a voltage comparison module, and an MCU. The inter-electrode voltage sampling and isolation module is used to collect the inter-electrode voltage signal between the molybdenum wire and the workpiece, safely convert the high-voltage processing signal into a low-voltage signal, and achieve electrical isolation. The inter-electrode voltage sampling and isolation module includes an optocoupler N1. The two input terminals of the optocoupler N1 sample the potentials of the workpiece and the molybdenum wire, respectively. The collector of the output terminal of the optocoupler N1 is connected to a 5V voltage through a pull-up resistor R8. The voltage signal V-sense of the collector of the optocoupler N1 is input to the input terminal of the voltage comparison module. The voltage comparison module includes a comparator U2. The input terminal of the comparator U2 is also connected to a threshold voltage V-ref. The threshold voltage V-ref is compared with the voltage signal V-sense. The output terminal of the comparator U2 outputs an MCU-sense signal to the input terminal of the MCU. The digital signal (high / low level) output by the voltage comparison module to the MCU indicates whether a short circuit has occurred between the molybdenum wire and the workpiece.

[0008] Furthermore, the inter-electrode voltage sampling and isolation module also includes a resistor R7, a capacitor C2, and a diode V1. The resistor R7 is a current-limiting resistor, with one end connected to the workpiece and the other end connected to the anode of the input terminal of the optocoupler N1. The cathode of the input terminal of the optocoupler N1 is connected to a molybdenum wire. The capacitor C2 is connected in series with the input terminal of the optocoupler N1 to filter out sudden abnormal pulses and prevent malfunctions. The diode V1 is connected in reverse series with the input terminal of the optocoupler N1 to prevent reverse current from damaging the input terminal of the optocoupler.

[0009] Furthermore, the voltage comparison module also includes a resistor R9 and a threshold voltage generation circuit for generating a threshold voltage V-ref. One end of the resistor R9 is connected to the drain of the output terminal of the optocoupler N1, and the other end is connected to the input terminal of the comparator U2. The threshold voltage generation circuit includes two resistors connected in series: resistor R10 and resistor R11. One end of resistor R10 is connected to a 5V voltage, and the other end of resistor R11 is grounded. The common junction of resistors R10 and R11 outputs the threshold voltage V-ref to the comparator U2. A capacitor C3 is also connected in parallel to ground at the input terminal of the comparator V-ref to filter out interference and prevent the comparator from malfunctioning.

[0010] Furthermore, in the threshold voltage generation circuit, resistor R11 is an adjustable resistor, which allows for flexible adjustment of the short-circuit detection sensitivity.

[0011] Furthermore, the MCU uses an STM32 series chip. Its output is connected to a molybdenum wire after passing through an isolation module and an amplification module. The isolation module uses optocoupler isolation and includes optocoupler U1, resistor R3, capacitor C1, resistor R4, resistor R5, and resistor R2. The MCU output is input to the anode of the input terminal of optocoupler U1 through resistor R2. Resistor R3 and capacitor C1 are connected in parallel between the anode and cathode of the input terminal of optocoupler U1. The collector of the output terminal of optocoupler U1 is connected to resistor R4, the emitter is grounded, and the emitter and the other end of resistor R4 are also connected to resistor R5. The amplification module includes a MOSFET Q3. The gate of MOSFET Q3 is connected to the common junction of resistors R4 and R5. The source of MOSFET Q3 is grounded, and the drain is connected to the molybdenum wire. The MCU indicates whether a short circuit has occurred between the molybdenum wire and the workpiece based on the digital signal output by the comparator. When a short circuit occurs, the output of the discharge pulse is cut off.

[0012] Furthermore, the MCU is also connected to a short-circuit alarm circuit, which includes: a light-emitting diode (LED) and a resistor R1. One end of the resistor R1 is connected to a 5V voltage, and the other end is connected in series with the anode of the LED. The cathode of the LED is connected to the MCU. When a short circuit occurs between the electrodes, the LED is driven to trigger a short-circuit alarm.

[0013] The beneficial effects of adopting the above technical solution are as follows: the inter-electrode voltage sampling and isolation module is used to sample the inter-electrode voltage and compare it with the threshold voltage generated by the threshold voltage generation circuit. The MCU indicates whether a short circuit has occurred between the molybdenum wire and the workpiece according to the digital signal output by the comparator. When a short circuit occurs, the output of the discharge pulse is cut off, thus realizing closed-loop control of molybdenum wire processing. The inter-electrode voltage can be monitored in real time to eliminate short circuits. Attached Figure Description

[0014] Figure 1 This is the electrical schematic diagram of this utility model;

[0015] Figure 2 This is the circuit schematic diagram of this technical solution;

[0016] Figure 3 This is the circuit schematic of the threshold voltage generation circuit. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0018] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0019] like Figure 1 As shown, a wire EDM short circuit detection and protection circuit provides sampling isolation of inter-electrode voltage between molybdenum wire and workpiece, voltage comparison module, and feedback MCU closed-loop control. Using this structure, the inter-electrode voltage can be monitored in real time, threshold comparison can be used to determine whether a short circuit has occurred, and the output of the discharge pulse can be cut off to eliminate the short circuit when a short circuit occurs, thus realizing closed-loop control of short circuit anomalies in molybdenum wire processing.

[0020] Specifically, such as Figure 2 As shown, this technical solution provides an inter-electrode voltage sampling and isolation module, a voltage comparison module, and an MCU.

[0021] The inter-electrode voltage sampling and isolation module is used to collect the inter-electrode voltage signal between the molybdenum wire and the workpiece, and safely convert the high-voltage processing signal into a low-voltage signal and achieve electrical isolation. The inter-electrode voltage sampling and isolation module includes: resistor R7, capacitor C2, diode V1, and optocoupler N1. Resistor R7 is a current-limiting resistor. One end of resistor R7 is connected to the workpiece, and the other end is connected to the anode of the input terminal of optocoupler N1. The cathode of the input terminal of optocoupler N1 is connected to the molybdenum wire. The two input terminals of optocoupler N1 sample the potential of the workpiece and the molybdenum wire respectively. Capacitor C2 is connected in series at the input terminal of optocoupler N1 to filter out sudden abnormal pulses and prevent malfunction. Diode V1 is connected in parallel with capacitor C2 and in reverse series at the input terminal of optocoupler N1 to prevent reverse current from damaging the input terminal of optocoupler. The collector of the output terminal of optocoupler N1 is connected to a 5V voltage through pull-up resistor R8. The voltage signal V-sense of the collector of optocoupler N1 is input to the input terminal of the voltage comparison module.

[0022] Optocoupler N1 is a linear optocoupler, using PC817. The brightness of its internal LED is linearly related to the output current of the phototransistor, which can reflect voltage changes well: the higher the inter-electrode voltage between the molybdenum wire and the workpiece, the greater the current flowing through the LED of optocoupler N1, the stronger the conduction of the phototransistor, resulting in a lower voltage at the output terminal V_sense point (closer to GND2). Conversely, when short-circuited, the inter-electrode voltage is 0, there is no current in the LED of optocoupler N1, the phototransistor is cut off, and the voltage at the V_sense point is pulled up to +5V by the pull-up resistor R8.

[0023] The voltage comparison module generates a threshold voltage and compares it with V-sense. It includes comparator U2 and resistor R9. One end of resistor R9 is connected to the drain of the output terminal of optocoupler N1, and the other end is connected to the input terminal of comparator U2. The input terminal of comparator U2 is also connected to the threshold voltage V-ref. The threshold voltage V-ref is compared with the voltage signal V-sense. Comparator U2 uses the LM339 chip, which operates at 5V. As shown in the figure, IN1-IN4+ are the V-sense voltage signal and the threshold voltage V-ref signal. A capacitor C3 is connected in parallel with ground at the V-ref input terminal of comparator U2 to filter out interference and prevent the comparator from malfunctioning.

[0024] Figure 3As shown, the threshold voltage V-ref is an adjustable voltage generated by a threshold voltage generating circuit, which comprises two resistors connected in series: resistor R10 and resistor R11. One end of the resistor R10 is connected to 5V voltage, the other end of the resistor R11 is grounded, and the common connection point of the resistor R10 and the resistor R11 outputs the threshold voltage V-ref to the comparator U2. In this circuit, the resistor R11 is an adjustable resistor, and the use of the adjustable resistor can flexibly adjust the sensitivity of short-circuit detection. The threshold voltage V-ref is adjusted to a fixed value through the resistor R11, and this voltage corresponds to a specific inter-electrode voltage threshold (e.g., 10V). When the inter-electrode voltage is lower than the inter-electrode voltage threshold (e.g., 10V), it is determined as a short circuit;

[0025] 1) Normal state: high inter-electrode voltage -> low V_sense voltage (e.g., 0.5V). At this time, V_sense < V_ref, and the comparator outputs a high level.

[0026] 2) Short-circuit state: low inter-electrode voltage -> high V_sense voltage (e.g., Vcc=5V). At this time, V_sense > V_ref, and the output of the comparator flips to a low level.

[0027] The OUT1 and OUT4 pins of the output end of the comparator U2 output the MCU-sense signal to the input end of the MCU, and the digital signal (high / low level) output from the voltage comparison module to the MCU indicates whether a short circuit occurs between the molybdenum wire and the workpiece.

[0028] Further, the MCU adopts an STM32 series chip, the output end of which is connected to the molybdenum wire after passing through an isolation module and an amplification module. The isolation module performs electrical isolation on the signals of the MCU control loop to improve the anti-interference capability, and the amplification module provides a larger load-carrying driving capability for the control signal after passing therethrough.

[0029] Further, the isolation module adopts optocoupler isolation, which comprises an optocoupler U1, a resistor R3, a capacitor C1, a resistor R4, a resistor R5 and a resistor R2. The output end of the MCU is input to the anode of the input end of the optocoupler U1 through the resistor R2, the resistor R3 and the capacitor C1 are connected in parallel between the anode and the cathode of the input end of the optocoupler U1, the collector of the output end of the optocoupler U1 is connected to the resistor R4, the emitter is grounded, and a resistor R5 is further connected between the emitter and the other end of the resistor R4.

[0030] Further, the amplification module comprises a MOS transistor Q3, the gate of the MOS transistor Q3 is connected to the common connection point of the resistor R4 and the resistor R5, the source of the MOS transistor Q3 is grounded, and the drain is connected to the molybdenum wire. The MCU determines whether a short circuit occurs between the molybdenum wire and the workpiece according to the digital signal (low-level signal) output by the comparator. When an inter-electrode short circuit occurs, the MCU outputs a low-level signal to the isolation module, the optocoupler U1 is turned off, the MOS transistor is cut off, the output of the discharge pulse is cut off, and retraction is performed to eliminate the short circuit.

[0031] Furthermore, the MCU is also connected to a short-circuit alarm circuit, which includes: a light-emitting diode (LED) and a resistor R1. One end of the resistor R1 is connected to a 5V voltage, and the other end is connected in series with the anode of the LED. The cathode of the LED is connected to the MCU. When a short circuit occurs between the electrodes, the LED is driven to trigger a short-circuit alarm.

Claims

1. A wire cutting short-circuit detection and protection circuit, characterized in that: The device includes an inter-electrode voltage sampling and isolation module, a voltage comparison module, and an MCU. The inter-electrode voltage sampling and isolation module includes an optocoupler N1. The two input terminals of the optocoupler N1 sample the potentials of the workpiece and the molybdenum wire, respectively. The collector of the output terminal of the optocoupler N1 is connected to a 5V voltage via a pull-up resistor R8. The voltage signal V-sense from the collector of the optocoupler N1 is input to the input terminal of the voltage comparison module. The voltage comparison module includes a comparator U2. The input terminal of the comparator U2 is also connected to a threshold voltage V-ref. The threshold voltage V-ref is compared with the voltage signal V-sense. The output terminal of the comparator U2 outputs an MCU-sense signal to the input terminal of the MCU.

2. The wire cutting short-circuit detection and protection circuit according to claim 1, characterized in that: The inter-electrode voltage sampling and isolation module also includes a resistor R7, a capacitor C2, and a diode V1. One end of the resistor R7 is connected to the workpiece, and the other end is connected to the anode of the input terminal of the optocoupler N1. The cathode of the input terminal of the optocoupler N1 is connected to a molybdenum wire. The capacitor C2 is connected in series at the input terminal of the optocoupler N1, and the diode V1 is connected in reverse at the input terminal of the optocoupler N1.

3. The wire cutting short-circuit detection and protection circuit according to claim 1, characterized in that: The voltage comparison module further includes a resistor R9 and a threshold voltage generation circuit for generating the threshold voltage V-ref. One end of the resistor R9 is connected to the drain of the output terminal of the optocoupler N1, and the other end is connected to the input terminal of the comparator U2. The threshold voltage generation circuit includes two resistors connected in series: resistor R10 and resistor R11. One end of resistor R10 is connected to a 5V voltage, and the other end of resistor R11 is grounded. The common junction of resistors R10 and R11 outputs the threshold voltage V-ref to the comparator U2.

4. The wire cutting short-circuit detection and protection circuit according to claim 3, characterized in that: In the threshold voltage generation circuit, the resistor R11 is an adjustable resistor.

5. The wire cutting short-circuit detection and protection circuit according to claim 1, characterized in that: The MCU uses an STM32 series chip. Its output is connected to a molybdenum wire after passing through an isolation module and an amplification module. The isolation module uses optocoupler isolation and includes an optocoupler U1, a resistor R3, a capacitor C1, a resistor R4, a resistor R5, and a resistor R2. The MCU output is input to the anode of the input terminal of the optocoupler U1 through resistor R2. Resistor R3 and capacitor C1 are connected in parallel between the anode and cathode of the input terminal of the optocoupler U1. The collector of the output terminal of the optocoupler U1 is connected to resistor R4, the emitter is grounded, and the emitter and the other end of resistor R4 are also connected to resistor R5. The amplification module includes a MOS transistor Q3. The gate of the MOS transistor Q3 is connected to the common junction of resistors R4 and R5. The source of the MOS transistor Q3 is grounded, and the drain is connected to a molybdenum wire.

6. The wire cutting short-circuit detection and protection circuit according to claim 5, characterized in that: The MCU is also connected to a short-circuit alarm circuit, which includes a light-emitting diode and a resistor R1. One end of the resistor R1 is connected to a 5V voltage, and the other end is connected in series with the anode of the light-emitting diode. The cathode of the light-emitting diode is connected to the MCU.

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