CN102248235B - Device and method for detecting discharge state in electric spark linear cutting work gap - Google Patents

Abstract

The invention relates to a device and method for detecting gap discharge state in electric discharge wire cutting machining, and belongs to the technical field of electric discharge processing. The differential sampling module of the device is connected to the two poles of the electric discharge machine tool through a signal transmission cable, the signal output terminal of the differential sampling module is connected to the signal input terminal of the threshold value comparison module, and the signal output terminal of the threshold value comparison module is connected to the signal input terminal of the photoelectric isolation module Connection, the first signal input end of the CPLD state discrimination and processing module is connected with the signal output end of the photoelectric isolation module, and the signal output end of the host computer is connected with the second signal input end of the CPLD state discrimination and processing module through the CPLD program download cable. The threshold comparison module compares the sampled gap voltage signal with the three preset thresholds through an integrated comparator, and sends the comparison result to the photoelectric isolation module. The invention can be used for detecting the gap pulse discharge state of electric discharge wire cutting machine tools.

Description

Device and method for detecting gap discharge state in wire electric discharge cutting machining

technical field

The invention relates to a device and method for detecting gap discharge state in electric discharge wire cutting machining, and belongs to the technical field of electric discharge processing.

Background technique

EDM is to etch the material of the workpiece through the pulsed spark discharge between the tool electrode and the workpiece, so as to meet the predetermined processing requirements for the size, shape and surface quality of the part. The EDM method is not limited by the mechanical properties of the workpiece such as hardness and strength, and has the advantages of small macroscopic cutting force. Therefore, it is especially suitable for processing difficult-to-machine materials and complex-shaped workpieces. It has a wide range of applications in aviation, aerospace, molds and other fields. Applications.

During the EDM process of metal materials, the inter-electrode voltage signal reflects the pulse discharge during the machining process, which is closely related to the efficiency and accuracy of EDM. When the pulse discharge is in the state of spark discharge, the voltage at both ends of the gap is delayed from the no-load voltage for a period of breakdown, and the gap breaks down, and the voltage at both ends of the gap drops from the no-load voltage to the discharge maintenance voltage. In wire electric discharge machining, due to the relative motion between the electrode wire and the workpiece, it is generally believed that there is no stable arc discharge phenomenon. However, in the actual processing process, there is a discharge phenomenon without breakdown delay, and this discharge state is an unstable arc discharge state with partial short circuit. It shows that the gap chip removal is difficult and the processing state is poor at this time. Therefore, in the process of WEDM, it is necessary to distinguish this discharge state from the spark discharge state with breakdown delay. Therefore, in wire electric discharge machining of metal materials, gap pulse discharge states are divided into: no-load, spark discharge, unstable arc discharge and short circuit.

EDM technology is generally used to process conductive materials. The existing auxiliary electrode method can realize the use of EDM technology to process insulating ceramics. The principle is to add a conductive layer to the surface of the workpiece, and use the conductive film formed during the discharge process to form an auxiliary electrode to achieve discharge. processing. In the WEDM process of insulating ceramics, when the formation of the conductive film is poor, the thickness of the conductive film is small, the resistance is large, and the gap high-voltage discharge phenomenon occurs. When the gap discharge voltage is higher than the maintenance voltage when processing metal, the spark discharge state at this time is called a high-resistance spark state, and the short-circuit state at this time is called a high-resistance short-circuit state. When the conductive film is well formed, the thickness of the conductive film is large, the resistance is small, and the gap discharge voltage is approximately equal to the maintenance voltage during metal processing. The spark discharge state at this time is called the low-resistance spark state, and the short-circuit state at this time is called Low resistance short circuit condition. Therefore, in the WEDM of insulating ceramics, the gap discharge state is divided into five types, which are no-load, high-resistance spark, low-resistance spark, high-resistance short-circuit and low-resistance short-circuit state.

The current wire electric discharge machine tool generally only detects the average voltage of the gap, and uses this as a reference value to determine the current servo feed speed. When the average voltage of the gap is higher than the reference value, the feed is accelerated; when the average voltage of the gap is lower than the reference value, the workbench stops feeding and enters the waiting state; when the detected short circuit reaches a certain number, the servo of the workbench is controlled to retreat . This gap state detection method can approximately reflect the current gap discharge state, but since the gap average voltage is composed of the average voltage of various discharge states, it cannot detect a single pulse discharge state, so the average voltage method contains uncertain factors. Real-time and accurate monitoring of the gap cannot be realized, and the processing effect may be deteriorated. Especially for wire electric discharge machining of insulating ceramics, due to the existence of high-resistance discharge state, the average voltage of the gap is high, and the average voltage detection method will speed up the feed speed, which will cause the processing effect to deteriorate or even fail to process. At this time, the average voltage The detection method fails.

Contents of the invention

The object of the present invention is to provide a discharge state detection device for wire electric discharge machining. At the end of the width, the current pulse discharge state is judged, and the pulse state information is statistically processed to infer the processing state of the gap, which is used as the basis for servo control.

The present invention is achieved through the following technical solutions:

Gap discharge state detection device for WEDM, including differential sampling module, threshold value comparison module, photoelectric isolation module, CPLD discrimination and processing module, host computer, PCI104 bus cable, CPLD program download cable and signal transmission cable, differential sampling module through The signal transmission cable is connected to the two poles of the EDM machine tool, the signal output terminal of the differential sampling module is connected to the signal input terminal of the threshold value comparison module, the signal output terminal of the threshold value comparison module is connected to the signal input terminal of the photoelectric isolation module, and the CPLD status is judged and processed The first signal input terminal of the module is connected with the signal output terminal of the photoelectric isolation module, the signal output terminal of the CPLD state discrimination and processing module is connected with the signal input terminal of the host computer through the PCI104 bus cable, and the signal output terminal of the host computer is downloaded through the CPLD program The cable is connected with the second signal input end of the CPLD state discrimination and processing module. The threshold comparison module compares the sampled gap voltage signal with the three thresholds set by the integrated comparator, and sends the comparison result to the photoelectric isolation module; the threshold settings of the three comparators of the threshold comparison module correspond to the threshold V respectively. _ef1 , V _ef2 , V _ef3 , in the electric discharge machining of metal materials, the threshold V _ef3 is set to 3~5V, the threshold V _ef2 is set to be slightly lower than the value of the metal pulse discharge sustaining voltage, and the threshold V _ef1 is set to be slightly lower than the empty voltage. Carrying voltage; in wire electric discharge machining of insulating ceramic materials, only the threshold V _ef2 needs to be adjusted, and the threshold V _ef2 is set to be slightly larger than the metal pulse discharge sustaining voltage value, V _ef3 is set to 3V, V _ef2 is set to 40V, V _ef1 is set to 70V.

A detection method for gap discharge state in wire electric discharge machining, comprising the following steps:

Use the integrated operational amplifier to collect the gap voltage signal to the detection device by means of differential operation, and connect it to the threshold comparison module;

The threshold comparison module compares the sampled gap voltage signal with the three preset thresholds through an integrated comparator, and sends the comparison result to the photoelectric isolation module;

The photoelectric isolation module sends the comparison result to the CPLD state discrimination and processing module through photoelectric isolation;

The CPLD state discrimination and processing module processes the input signal, and judges the discharge state of the current pulse by detecting the gap voltage number and carrying out logical operation on the input signal, and transmits it to the upper computer through the PCI104 bus cable; During the pulse width period, whether there is a falling edge in the input signal is used to detect whether the gap is broken down, and the logic operation is performed on each input signal to judge the pulse discharge state, and then the state output is realized when the pulse width is about to end by sampling the control pulse. And use the state holding module to keep the state information until the end of the pulse interval, so as to realize the discrimination of the gap discharge state;

The host computer obtains the discharge state information of each pulse, and performs statistical processing to infer the processing state of the gap at this time, providing a basis for the operation of the control system.

The beneficial effects of the present invention mainly include:

1. The detection device uses CPLD for state discrimination and processing. CPLD undertakes the main state discrimination work. Since CPLD is an online programmable module, the entire detection device has great flexibility.

2. The detection device can realize the discrimination of each pulse discharge state, and can obtain more comprehensive gap state information, and the gap discharge state detection device can distinguish the unstable arc discharge state without breakdown delay, which is conducive to more accurate judgment The current gap processing state, so the device has the advantages of good real-time performance, accuracy and stability.

3. The detection device can be used not only for wire electric discharge processing of metal materials, but also for wire electric discharge processing of insulating ceramic materials. It can be realized only by adjusting the threshold value, so the device has the advantages of convenient operation and wide application range. advantage.

Description of drawings:

Figure 1 is the waveform discriminant diagram of pulse discharge state in wire electric discharge machining, in which: Figure a) is the waveform discriminant diagram of wire electric discharge machining of metal materials. , unstable arc and short circuit state, CMP1, CMP2 and CMP3 are the three input signals of CPLD, V _ef1 , V _ef2 , V _ef3 are the three thresholds set; Figure b) is the waveform discrimination diagram of insulating ceramic wire cutting , in the process of wire electric discharge cutting of insulating ceramics, the pulse discharge state has no load, high resistance spark, low resistance spark, high resistance short circuit and low resistance short circuit state, CMP1, CMP2 and CMP3 are the three input signals of CPLD, V _ef1 , V _ef2 and V _ef3 are the three thresholds set;

Fig. 2 is a structural schematic diagram of a gap discharge state detection device for wire electric discharge machining, wherein: label 1 indicates an electric discharge machine tool, label 2 indicates a signal transmission cable, label 3 indicates a differential sampling module, label 4 indicates a threshold value comparison module, and label 5 Indicates the photoelectric isolation module, the number 6 indicates the CPLD state discrimination and processing module, the number 7 indicates the PCI104 bus cable, the number 8 indicates the upper computer, and the number 9 indicates the CPLD program download cable;

Fig. 3 is a schematic diagram of the circuit principle of the detection device for gap discharge state in wire electric discharge machining;

Fig. 4 is a schematic diagram of the CPLD internal circuit program of the wire electric discharge machining gap discharge state detection device;

Fig. 5 is the schematic diagram of the circuit structure of the CPLD internal circuit program SERVO program block;

Fig. 6 is a CPLD program simulation waveform diagram of wire electric discharge machining of metal materials;

Fig. 7 is a simulation waveform diagram of a CPLD program for wire electric discharge machining of insulating ceramic materials.

Detailed ways:

The present invention will be described in further detail below in conjunction with the accompanying drawings: the present embodiment is implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes have been provided, but the protection scope of the present invention is not limited to the following Example. the

As shown in Figure 2, the spark gap discharge state detection device involved in this embodiment includes a signal transmission cable 2, a differential sampling module 3, a threshold comparison module 4, a photoelectric isolation module 5, and a CPLD (complex programmable logic device) state Discrimination and processing module 6, PCI104 bus cable 7, host computer 8 and CPLD program download cable 9. The connection method is as follows: the differential sampling module 3 is connected to the two poles of the electric discharge machine tool 1 through the signal transmission cable 2, the signal output terminal of the differential sampling module 3 is connected to the signal input terminal of the threshold value comparison module 4, and the signal output terminal of the threshold value comparison module 4 is connected to the signal input terminal of the threshold value comparison module 4. The signal input end of photoelectric isolation module 5 is connected, and the first signal input end of CPLD state discrimination and processing module 6 is connected with the signal output end of photoelectric isolation module 5, and the signal output end of CPLD state discrimination and processing module 6 passes PCI104 bus cable 7 Connect with the signal input terminal of host computer 8, the signal output terminal of host computer 8 is connected with the second signal input terminal of CPLD state discrimination and processing module 6 through CPLD program download cable 9.

The main principle is that when the voltage signal of the pole gap of the EDM machine tool is input to the differential sampling module through the signal transmission cable, the differential sampling module collects the voltage signal of the two poles of the EDM machine tool and converts it into a voltage signal below the power supply voltage of the detection device. The threshold comparison module compares the voltage signal with the set threshold to obtain the range of the current voltage. The comparison result is input into the CPLD through the photoelectric isolation module. The CPLD tracks the input voltage signal in real time during the pulse width. According to the voltage signal during the pulse width Whether there is a falling edge in the amplitude range and the signal, when the pulse width ends, the discharge state of the pulse is judged, and the judgment result is sent to the host computer for storage through the PCI104 bus, and statistical processing is performed to provide servo control system for the servo control system. in accordance with. The internal program of CPLD is stored on the host computer, which can be downloaded to CPLD through the JTAG type CPLD program download cable through online programming.

Fig. 3 is the circuit schematic diagram of the spark gap discharge state detection device provided by this specific embodiment, and the drawing software used is Protel DXP2004. Including differential sampling module, threshold comparison module, photoelectric isolation module, CPLD state discrimination and processing module.

Specifically, the differential sampling module (U1) is an integrated operational amplifier LF357N, the positive pole of the machine tool is connected in series with the inverting input terminal 2 of U1 with R1 and R3, and the negative pole of the machine tool is connected in series with the non-inverting input terminal 3 of U1 with R2 and R4. The non-inverting input terminal 3 of U1 is connected in series with the analog ground with R5, and the output terminal 6 of U1 is connected in series with the inverting input terminal 2 of U1 with R7. After C9 and C21 are connected in parallel, they are connected between the positive power input terminal of U1 and the analog ground to play the role of decoupling. After C10 and C20 are connected in parallel, they are connected between the negative power input terminal of U1 and the analog ground to play a role of decoupling.

The threshold comparison module (U4 and U5) is an integrated comparator LM393AN. The output terminal 6 of U1 is connected in series with the inverting input terminal 2 of U4A with R8, and the output terminal 6 of U1 is connected in series with the inverting input terminal of U4B with R10. Terminal 6, the output terminal 6 of U1 is connected in series with R14 to the inverting input terminal 2 of U5A. R9 and potentiometer R23 are connected in series between +15V and the analog ground, and the output terminal 2 of the potentiometer R23 is connected to the non-inverting input terminal 3 of U4A. R11 and potentiometer R24 are connected in series between +15V and the analog ground, and the output terminal 2 of the potentiometer R24 is connected to the non-inverting input terminal 5 of U4B. R15 and potentiometer R25 are connected in series between +15V and analog ground, and output terminal 2 of potentiometer R25 is connected to non-inverting input terminal 3 of U5A. The output terminal 1 of U4A is connected in series with R12 and then connected to +5V, the output terminal 7 of U4B is connected in series with R13 and then connected to +5V, and the output terminal 1 of U5A is connected in series with R16 and then connected to +5V.

The photoelectric isolation module (U7, U8 and U9) is a high-speed optocoupler 6N137. The output terminal 1 of U4A is connected to the terminal 2 of U7 in series with R17, and the output terminal 1 of U5A is connected to the terminal 2 of U8 in series with R18. Output terminal 7 is connected in series with R17 to terminal 2 of U9. The 3 terminals of U7 are connected to the analog ground, the 3 terminals of U8 are connected to the analog ground, and the 3 terminals of U9 are connected to the analog ground. Terminal 8 of U7 is connected to the positive pole VCC of the digital circuit power supply, terminal 5 of U7 is connected to the digital ground, terminal 8 and terminal 5 of U7 are connected to C13, terminal 6 of U7 is connected in series with terminal 8 of U7 with R20. Terminal 8 of U8 is connected to the positive pole VCC of the digital circuit power supply, terminal 5 of U8 is connected to digital ground, terminal 8 and terminal 5 of U8 are connected to C14, terminal 6 of U8 is connected in series with terminal 8 of U8 R21. Terminal 8 of U9 is connected to the positive pole VCC of the digital circuit power supply, terminal 5 of U9 is connected to the digital ground, terminal 8 and terminal 5 of U9 are connected to C15, terminal 6 of U9 is connected in series with terminal 8 of U9 R22.

CPLD discrimination and processing module (U6) is EPM7064SLC44-10 CPLD, U3 is inverter 74AC14B, U2 is OSC 25MHz active crystal oscillator, P1 is JTAG download terminal, G1 is exclusion. Terminal 33 of U6 is connected to terminal 6 of U7, terminal 34 of U6 is connected to terminal 6 of U8, terminal 36 of U6 is connected to terminal 6 of U9, terminal 37 of U6 is connected to the external pulse width end signal. Terminals 16, 17, 18, 19 and 20 of U6 are output terminals, which are connected to the PCI104 bus. Terminals 10, 22, 30 and 42 of U6 are connected to the digital ground, terminals 3, 15, 23 and 35 of U6 are connected to the power supply VCC. Terminal 1 of P1 is connected to terminal 32 of U6, terminal 3 of P1 is connected to terminal 38 of U6, terminal 5 of P1 is connected to terminal 13 of U6, terminal 7 and terminal 9 of P1 are connected to terminal 7 of U6, terminal 2 of P1 Terminals 10 and 10 are connected to digital ground, and terminal 4 of P1 is connected to VCC. Terminal 2 of U2 is connected to digital ground, terminal 3 of U2 is connected to terminal 1 of U3A, and terminal 4 of U2 is connected to VCC. Terminal 2 of U3A is connected to terminal 43 of U6.

Fig. 4 is the CPLD internal circuit program diagram of the spark gap discharge state detection device provided by this specific embodiment, and the program development software used is Quartus II 7.0. Input CLK is terminal 43 of chip U6, input End_pulse is terminal 37 of the chip, input CMP1 is terminal 33 of U6, input CMP2 is terminal 34 of U6, and input CMP3 is terminal 36 of U6. Output Spark/Spark_H is U6 terminal 19, output Spark_L is U6 terminal 18, output Open is U6 terminal 20, output Arc/Short_H is U6 terminal 17, output Short/Short_L is U6 terminal 16.

The internal circuit program of CPLD includes four modules, which are gap breakdown detection module, logic judgment module, state sampling control module and state holding module.

Specifically, for the gap breakdown detection module: it can be seen from the electric discharge machining discharge state waveform discrimination diagram shown in Figure 1 that when the gap occurs, there is a falling edge of CMP1 or CMP2 during the high level of CMP3 , so the gap breakdown signal can be detected by detecting the falling edges of CMP1 and CMP2 during the high level period of CMP3. The gap breakdown detection module consists of two parts, which are the DFF register Inst33 of the CMP1 falling edge detection module and the DFF register Inst1 of the CMP2 falling edge detection module. The output of PUL1 is always low level. When the input CMP1 has a falling edge during the high level period of CMP3, PUL1 outputs high level and remains until the end of the pulse width. The output of PUL2 is always low level, when input CMP2 has a falling edge during the high level period of CMP3, PUL2 outputs high level and remains until the end of the pulse width. Use CMP3 as the clearing signal of the two registers. During the low level period of CMP3, that is, between pulses, the gap breakdown detection module is cleared and waits for the next pulse width.

Logic judgment module: Two-input AND gates Inst5, Inst6, Inst11, three-input AND gates Inst13, Inst14, Inst15 and NOT gates Inst8, Inst10, Inst12, Inst16 form a logic judgment module during the high level of CMP3.

State sampling control module: NOT gate Inst34, SELECT_PUL program block, DFF register Inst2 and two-input AND gates Inst19, Inst20, Inst21, Inst22, Inst23 form a state sampling control module, and End_Pulse is the state sampling control signal when the pulse width is about to end. Since the gap voltage signal enters the detection device from the signal transmission cable, and enters the CPLD through differential sampling, comparison, and photoelectric isolation processing, an overall transmission delay of 1-2μs will be generated, so the main oscillator signal of the power supply can be used as the End_Pulse signal. When the End_Pulse signal has a falling edge, it indicates that the output of PUL1, PUL2, Inst13, Inst5, and Inst6 is sampled at this time, and the sampling result is held for 0.8 μs. The SELECT_PUL program block is used to set the sampling pulse length to 0.8μs, where SLE_PUL is the rising edge of the sampling pulse, and END_PUL is the end signal of the sampling pulse. Input these two signals into the DFF register to obtain a 0.8μs sampling pulse. The outputs of PUL1, PUL2, Inst13, Inst5, and Inst6 are sampled through five two-input AND gates.

State holding module: 5 SERVO program blocks form a state holding module, which is used to hold 5 outputs of the state sampling control module. Figure 5 is a circuit structure diagram of the SERVO program block. The output of each channel sampled by the state sampling control module is used as state information, which is transmitted into the SERVO program block and kept by the DFF register Inst1 until the next pulse width comes. The DFF register Inst is used to provide a clear signal, and ENABLE is connected to the external CMP3. When the next pulse width comes, the ENABLE signal changes from low to high, and the previous state sampling information is cleared. 2us_CON is used to clear the clear signal when the sampling control signal comes, and prepare for state maintenance. For the output of the 5-way SERVO, during each pulse period, only the output corresponding to the pulse discharge state has a high level, and the other four outputs are always low, so that the pulse discharge state can be distinguished. In metal EDM, the output Spark/Spark_H corresponds to the spark state output, the output Spark_L is meaningless, the output Open corresponds to the no-load state output, the output Arc/Short_H corresponds to the unstable arc state output, and the output Short/Short_L corresponds to the short circuit state output. In the WEDM of insulating ceramics, the output Spark/Spark_H corresponds to the high-impedance spark state output, the output Spark_L corresponds to the low-impedance spark state output, the output Open corresponds to the no-load state output, and the output Arc/Short_H corresponds to the high-impedance short-circuit state output. The output Short/Short_L corresponds to the low-impedance short-circuit state output.

The process of spark gap discharge state detection is further described below by specific embodiments:

Embodiment 1 Wire electric discharge machining of metal materials

The hardware circuit and CPLD internal circuit are as shown in Figure 2-5, only need to adjust the three thresholds of V _ef1 , V _ef2 and V _ef3 . The corresponding threshold setting values are relative to the no-load voltage. The threshold setting of the three comparators of the threshold comparison module correspond to the thresholds V _ef1 , V _ef2 , V _ef3 respectively, but their values are equal to V _ef1 , V _ef2 , V _ef3 times The sampling scale of the differential sampling module. Threshold V _ef3 is set to 3~5V. Its function is to distinguish the pulse width and pulse interval of each pulse. The control detection program only judges the discharge state during the pulse width, and does not judge the state during the pulse interval to prevent errors. judge. The threshold V _ef2 is set to be slightly lower than the sustaining voltage of the metal pulse discharge, and the threshold V _ef1 is set to be slightly lower than the no-load voltage. In the EDM of metal materials, V _ef3 is set to 3V, and V _ef2 is set to 18V. V _ef1 is set to 70V.

The gap voltage enters the threshold comparison module through the differential sampling module, and compares it with the set threshold. After photoelectric isolation, the waveforms of the CMP1, CMP2, and CMP3 signals, as well as the outputs of the CPLD internal breakdown signal detection modules Inst1 and Inst33, as shown in Figure 1 a) as shown.

During the high level period of CMP3, that is, the pulse width period, different gap discharge states have different CMP1 and CMP2 signals. During the pulse width, if there is a falling edge on CMP1, it indicates that the gap voltage is from high to low, and a breakdown phenomenon occurs, and there is no falling edge on CMP2, and the gap voltage is higher than V _ef2 after breakdown. This pulse discharge is in a spark state, Inst33 Output high level, after the sampling control ends, the output Spark/Spark_H is high level, and the other outputs are low level. During the pulse width, when neither CMP1 nor CMP2 has a falling edge, the following three situations need to be distinguished. First, if the output of CMP1 is high level, it means that the voltage at both ends of the gap is higher than V _ef1 , this pulse discharge is in the no-load state, and Inst13 outputs high level. After the sampling control is over, the output Open is high level, and the rest output is low level; secondly, if CMP1 is low level and CMP2 is high level, it indicates that the voltage at both ends of the gap has been between V _ef1 and V _ef2 at this time, and there is no gap breakdown, and this pulse discharge is In the unstable arc state, Inst4 outputs high level, after the sampling control ends, the output Arc/Short_H is high level, and the other outputs are low level. Finally, if CMP2 is always at low level, it indicates that the voltage at both ends of the gap has been lower than V _ef2 at this time, and there is no gap breakdown. It is considered that this pulse discharge is a short circuit state, and Inst15 outputs high level. After the sampling control is completed, The output Short/Short_L is high level, and the other outputs are low level. In this way, the state discrimination of any pulse discharge is realized, and the judgment result is transmitted to the host computer through the PCI104 bus, and the host computer estimates the gap processing state at this time according to the discharge state information of each pulse. Fig. 7 Simulation waveform diagram of CPLD program for electric discharge machining of metal materials. Set the input signal of CPLD according to CMP1, CMP2 and CMP3 in Figure 1 a), and use the Simulator module of Quartus program to simulate the CPLD program. It can be seen from the simulation results that the system can distinguish the discharge state of each pulse, and the state information Hold until the next pulse comes.

Embodiment 2 Wire-cut electric discharge machining of insulating ceramic material

The hardware circuit and CPLD internal circuit are described in Figure 2-5, only need to adjust the threshold V _ef2 . The threshold V _ef2 is set to be slightly larger than the metal pulse discharge sustaining voltage value, so in the wire electric discharge machining of insulating ceramics, V _ef3 is set to 3V, and V _ef2 is set to 40V. V _ef1 is set to 70V.

The gap voltage enters the threshold comparison module through the differential sampling module, and compares it with the set threshold. After photoelectric isolation, the waveforms of the CMP1, CMP2, and CMP3 signals, as well as the outputs of the CPLD internal breakdown signal detection modules Inst1 and Inst33, as shown in Figure 1 b) as shown.

During the high level period of CMP3, that is, the pulse width period, different gap discharge states have different CMP1 and CMP2 signals. During the pulse width, if the output of CMP1 and CMP2 has a falling edge, it indicates that the gap voltage changes from high to low, and a breakdown phenomenon occurs, and after the breakdown, the gap voltage is lower than V _ef2 , and this pulse discharge is a low-resistance spark state, Inst1 Output high level, after the sampling control ends, the output Spark_L is high level, and the other outputs are low level. During the pulse width, when there is no falling edge on CMP2 and there is a falling edge on CMP1 output, it indicates that although the gap has broken down, the gap discharge voltage is higher than V _ef2 but lower than V _ef1 , and this pulse discharge is considered to be a high-resistance spark state , Inst33 outputs high level, after the sampling control ends, the output Spark/Spark_H is high level, and the other outputs are low level. When neither CMP1 nor CMP2 has a falling edge during the pulse width, the following three situations need to be distinguished. First, if the output of CMP1 is high level, it indicates that the voltage at both ends of the gap is higher than V _ef1 , and this pulse discharge is considered to be in a no-load state, and Inst13 outputs high level. After the sampling control is completed, the output Open is high level, and the rest The output is low level; secondly, if CMP1 is low level and CMP2 is high level, it indicates that the voltage at both ends of the gap has been between V _ef1 and V _ef2 at this time, and there is no gap breakdown, so it is considered that this The pulse discharge is a high-impedance short-circuit state, and Inst4 outputs a high level. After the sampling control is completed, the output Arc/Short_H is a high level, and the other outputs are a low level. Finally, if CMP2 is always at low level, it indicates that the voltage at both ends of the gap has been lower than V _ef2 at this time, and there is no gap breakdown. It is considered that this pulse discharge is a low-impedance short-circuit state, Inst15 outputs high level, and the sampling control ends After that, the output Short/Short_L is high level, and the other outputs are low level. In this way, the state discrimination of any pulse discharge is realized, and the judgment result is transmitted to the host computer through the PCI104 bus, and the host computer estimates the gap processing state at this time according to the discharge state information of each pulse. Fig. 8 is a simulation waveform diagram of a CPLD program for wire electric discharge machining of insulating ceramic materials. Set the input signal of CPLD according to CMP1, CMP2 and CMP3 in Figure 1 b), and use the Simulator module of Quartus program to simulate the CPLD program. It can be seen from the simulation results that the system can distinguish the discharge state of each pulse, and the state information Hold until the next pulse comes.

The above are only preferred specific implementations of the present invention. These specific implementations are all based on different implementations under the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Anyone familiar with the technical field Within the technical scope disclosed in the present invention, any changes or substitutions that can be easily conceived by a skilled person shall fall within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (5)

1. a Wire-cut Electrical Discharge Machining clearance discharge condition detection apparatus, it is characterized in that, comprise the difference sampling module, the threshold value comparison module, photoelectric isolation module, CPLD condition discrimination and processing module, host computer, the PCI104 bus cable, CPLD program download cable and signal-transmitting cable, the difference sampling module is connected with the two poles of the earth of spark-erosion machine tool by signal-transmitting cable, the signal output part of difference sampling module is connected with the signal input part of threshold value comparison module, the signal output part of threshold value comparison module is connected with the signal input part of photoelectric isolation module, the first signal input of CPLD condition discrimination and processing module is connected with the signal output part of photoelectric isolation module, the signal output part of CPLD condition discrimination and processing module is connected with the signal input part of host computer by the PCI104 bus cable, the signal output part of host computer is connected with the secondary signal input of CPLD condition discrimination and processing module by CPLD program download cable, described threshold value comparison module compares three threshold values of the gap voltage signal of sampling and setting by integrated comparator, and the result compared is sent into to photoelectric isolation module, the threshold value setting of three comparators of threshold value comparison module is corresponding threshold value V respectively _ef1, V _ef2, V _ef3, in the spark machined of metal material, threshold value V _ef3be set as 3～5V, threshold value V _ef2be set to be slightly less than the metal pulsed discharge and maintain magnitude of voltage, threshold value V _ef1be set to a little less than floating voltage, in the Wire-cut Electrical Discharge Machining of insulating ceramic materials, only need to adjust threshold value V _ef2get final product threshold value V _ef2be set to be slightly larger than the metal pulsed discharge and maintain magnitude of voltage.

2. Wire-cut Electrical Discharge Machining clearance discharge condition detection apparatus according to claim 1, it is characterized in that, described difference sampling module is the integrated operational amplifier module that bandwidth 5MHz is above and voltage conversioning rate is 50V/ μ s, described threshold value comparison module is the high speed analog comparator module that reaches nanosecond time delay, and described photoelectric isolation module is the photoelectric coupler module that bandwidth 1MHz is above and voltage conversioning rate is 500V/ μ s.

3. a Wire-cut Electrical Discharge Machining clearance discharge condition detection method, is characterized in that, comprises the steps:

Utilize integrated operational amplifier to adopt the mode of calculus of differences that the gap voltage signals collecting is arrived to checkout gear, and access threshold value comparison module;

Described threshold value comparison module compares three threshold values of the gap voltage signal of sampling and setting by integrated comparator, and the result compared is sent into to photoelectric isolation module;

Described photoelectric isolation module is sent into CPLD condition discrimination and processing module by comparative result through the photoelectricity isolation by photoelectrical coupler;

Described CPLD condition discrimination and processing module are processed the signal of input, by the detection to the gap voltage signal with to input signal, carry out logical operation, judge the discharge condition when prepulse, and are sent to host computer by the PCI104 bus cable; At first during pulsewidth, by whether exist trailing edge to come detector gap whether to puncture to input signal, and each input signal is carried out to logical operation, differentiate the pulsed discharge state, then realize carrying out State-output by the controlling of sampling pulse when pulsewidth closes to an end, and utilize state to keep module that status information is remained between arteries and veins and finishes always, realize the differentiation to clearance discharge condition with this;

Described host computer obtains the discharge condition information of each pulse, and carries out statistical disposition, infers the now machining state in gap, for the operation of control system provides foundation.

4. Wire-cut Electrical Discharge Machining clearance discharge condition detection method according to claim 3, it is characterized in that, the sample mode of described gap voltage is the calculus of differences mode, and corresponding sampling A/D chip is integrated operational amplifier and has the above bandwidth of 5M and the voltage conversioning rate of 50V/ μ s.

5. Wire-cut Electrical Discharge Machining clearance discharge condition detection method according to claim 3, is characterized in that, the photoelectrical coupler of described photoelectric isolation module has the above frequency response of 1MHz and the voltage conversioning rate of 500V/ μ s.

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