Simple metal electric spark punching device based on thyristor self-holding type

Abstract

The application provides a simple metal electric spark punching device based on thyristor self-holding, which comprises a mechanical unit and an electrical driving unit. The mechanical unit comprises a metal guide rail with horizontal shaft supports fixed at both ends, guide rail connecting supports fixed outside the horizontal shaft supports, linear bearings slidably sleeved on the metal guide rail, a stepping motor and a needle electrode fixed on the linear bearings through a stepping motor base, a threaded rod connected with the stepping motor main shaft through a shaft coupling, a needle electrode feeding limit switch and a needle electrode retreating limit switch fixed on the opposite sides of the metal guide rail, and a workpiece to be punched fixed on the guide rail connecting support on the side of the needle electrode. The electrical driving unit comprises a discharge main circuit, a needle electrode motor feeding and retreating driving circuit, a voltage detection and pulse control circuit, and a start-stop machine control circuit. The device uses a thyristor to drive a stepping motor through a pulse generated by capacitor charging and discharging, and realizes self-control of the device through the self-holding characteristic of the thyristor, so that energy saving, portability and low cost are achieved.

Description

Technical Field

[0001] This invention relates to the field of electrical discharge drilling devices, specifically to a simple metal electrical discharge drilling device based on a thyristor self-holding mechanism. Background Technology

[0002] In the mold processing industry, electrical discharge drilling devices are widely used in the machining of micro-deep holes in metal workpieces. When an electrical discharge drilling device processes a metal workpiece, the electrode and the workpiece are respectively connected to the two stages of a pulse power supply. When the metal needle electrode (machining electrode) approaches the metal workpiece to be drilled, the metal workpiece discharges with the needle electrode and generates an electric spark. The instantaneous temperature is extremely high, which can melt or vaporize the local material of the metal workpiece, thereby achieving the purpose of electro-corrosion drilling of the metal workpiece.

[0003] Currently, the simplest EDM drilling device is purely manually controlled, with the needle electrode advancing and retreating to control the charging and discharging of the capacitor, thus achieving the purpose of electrical discharge drilling between the needle electrode and the workpiece. However, due to the limited capacity of the capacitor, the amount of corrosion generated by each discharge is extremely small, making purely manual drilling time-consuming and labor-intensive.

[0004] Currently, there are also automatic EDM drilling devices based on electromagnetic relays. However, due to the relatively high power consumption of electromagnetic relays, the slow operation of mechanical contacts, and the arcing of relay contacts, automatic EDM drilling control devices based on electromagnetic relays are inherently characterized by high power consumption, low efficiency, and easy contact damage due to arcing.

[0005] Patent application CN106670606A, published on May 17, 2017, discloses an electrical discharge machining (EDM) machine controlled by a microcontroller. This technology uses a microcontroller and a stepper motor to control the electrodes. While this achieves automatic control of the EDM machine, the strong electromagnetic interference generated by the electrical sparks during operation affects the normal operation of the microcontroller and can even damage it, resulting in low reliability. Furthermore, the microcontroller requires a minimum system, has a large number of pins, a complex structure, and high cost.

[0006] Currently, there are also more advanced high-power, high-frequency EDM drilling machines, which use power electronic converter circuits and have high frequency and single-pulse energy, resulting in high processing efficiency. However, their electrical structure and control system are complex, costly, bulky, and heavy, making them unsuitable for frequent use by small and micro-sized units, or they may not have sufficient funds or space for installation. Summary of the Invention

[0007] To address the technical problems of existing EDM drilling machines, this invention provides a simple metal EDM drilling device based on a thyristor self-holding mechanism. This EDM drilling device utilizes the characteristic that the thyristor will turn off only when the thyristor current drops below the thyristor sustaining current after receiving a trigger signal and then turning on. A pulse signal generation circuit is designed, and this pulse is used to control and drive a stepper motor to achieve automatic operation of the EDM drilling device.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A simple metal EDM drilling device based on thyristor self-holding includes an EDM drilling machine mechanical unit and an electrical drive and control unit. The EDM drilling machine mechanical unit includes two parallel metal guide rails. Horizontal shaft supports are fixedly connected to both ends of the metal guide rails. Guide rail connecting brackets are fixedly connected to the outer sides of the horizontal shaft supports. Linear bearings are slidably sleeved on the metal guide rails. A stepper motor base is fixedly connected to the linear bearing. A stepper motor is fixedly connected to the outer side of the stepper motor base. A threaded rod is fixedly connected to the main shaft of the stepper motor via a coupling. The outer end of the threaded rod passes through the guide rail connecting bracket, and a nut fixedly connected to the guide rail connecting bracket is sleeved on the threaded rod. A needle electrode is fixedly connected to the side of the stepper motor base opposite to the stepper motor. A needle electrode feed limit switch is fixed on the metal guide rail near the needle electrode, and a needle electrode retraction limit switch is fixed on the metal guide rail near the stepper motor. A workpiece to be drilled is fixed on the guide rail connecting bracket on the side of the needle electrode. The electrical drive and control unit includes a discharge main circuit, a needle electrode motor advance and retraction drive circuit, a voltage detection and pulse control circuit, and a start / stop control circuit.

[0010] The main discharge circuit is used to charge the energy storage capacitor with the generated DC voltage after passing through current limiting protection, thereby preparing for the discharge between the needle electrode and the workpiece to be drilled.

[0011] The start / stop control circuit is used to receive start and stop operation commands from the operator, thereby controlling whether the drilling device starts or stops drilling operations, and outputs start / stop commands to the needle electrode motor forward and backward drive circuit.

[0012] The voltage detection and pulse control circuit is used to detect the voltage of the energy storage capacitor through three adjustable potentiometers, which is equivalent to detecting the voltage of the two electrodes of the needle electrode and the workpiece to be drilled, thereby determining whether the two electrodes are in a short circuit, close-range open circuit, or long-range open circuit state, and outputting the judgment result to the needle electrode motor advance and retreat drive circuit as pulse and direction command signals.

[0013] The needle electrode motor forward and backward drive circuit is used to receive the start and stop commands from the start and stop control circuit under the excitation of the switching power supply, and to perform corresponding actions in combination with the pulse and direction command signals provided by the voltage detection and pulse control circuit, driving the stepper motor to rotate, and with the cooperation of the threaded rod and the linear bearing, driving the tip of the needle electrode to approach or move away from the workpiece to be drilled.

[0014] Furthermore, the metal guide rail is made of 304 stainless steel, and the horizontal shaft support is made of aluminum alloy.

[0015] Furthermore, the main discharge circuit includes a fuse F1, a step-down transformer T, diodes D1-D4, capacitors C1-C5, an energy storage capacitor C0, a current-limiting resistor R1, and a needle electrode and the workpiece to be drilled in the mechanical unit. One end of the fuse F1 is connected to the external 220V single-phase AC live wire, and the other end is connected to one end of the primary winding of the step-down transformer T. The other end of the primary winding of the step-down transformer T is connected to the external 220V single-phase AC neutral wire. One end of the secondary winding of the step-down transformer T is connected to one end of capacitors C0, C1, and C5, the positive terminal of diode D1, and the workpiece to be drilled. The capacitors C1-C4... Together with diodes D1 to D4, they form a four-stage series rectifier circuit. The other end of capacitor C1 is connected to the cathode of diode D2, the anode of diode D3, and one end of capacitor C3. The anode of diode D2 is connected to one end of capacitors C2 and C4 and the cathode of diode D1. The other end of capacitor C2 is connected to the other end of the secondary side of step-down transformer T. The other end of capacitor C4 is connected to the cathode of diode D3 and the anode of diode D4. The cathode of diode D4 is connected to the other end of capacitor C3, one end of capacitor C5, and one end of current-limiting resistor R1. The other end of current-limiting resistor R1 is connected to the other end of capacitor C0 and the pin electrode.

[0016] Furthermore, the step-down transformer T is selected as a power frequency power transformer with a turns ratio of 220:12 and adopts a flat design.

[0017] Furthermore, the needle electrode motor forward and backward drive circuit includes a DC-15V switching power supply, a stepper motor driver, and a stepper motor in the mechanical unit. One end of the high-voltage side of the DC-15V switching power supply is connected to the output side of the fuse F1 in the main discharge circuit, and the other end of the high-voltage side of the DC-15V switching power supply is connected to the external 220V single-phase AC neutral line. The V+ terminal of the DC output side of the DC-15V switching power supply is connected to the DC+ terminal of the stepper motor driver, and the V- terminal of the DC output side of the DC-15V switching power supply is connected to the DC- terminal of the stepper motor driver and serves as a reference ground. The A- and A+, B- and B+ terminals of the stepper motor driver are connected to the first phase A- and A+, and the second phase B- and B+ terminals of the stepper motor, respectively. The enable negative terminal E- of the stepper motor driver is connected to the reference ground.

[0018] Furthermore, the stepper motor driver is selected as a stepper motor driver with optical isolation.

[0019] Furthermore, the voltage detection and pulse control circuit includes a power supply stabilization and energization indication circuit, a pulse generation control circuit, and three voltage detection circuits; wherein,

[0020] The control power supply stabilization and energized indication circuit includes a reverse-blocking diode D0, a resistor R3, a light-emitting diode D5, and a capacitor C6. The anode of the reverse-blocking diode D0 is connected to V+ on the DC-15V output side of the switching power supply in the forward and reverse drive circuit of the needle electrode motor. The cathode of the reverse-blocking diode D0 is connected to a +15V power supply and one end of the resistor R3 and capacitor C6. The other end of the resistor R3 is connected to the anode of the light-emitting diode D5. The cathode of the light-emitting diode D5 and the other end of the capacitor C6 are connected to reference ground.

[0021] The pulse generation control circuit includes adjustable potentiometers R6, R7, and R9, resistors R8, R19, R25, and R26, a thyristor V1, temporary capacitors C7 and C8, transistors Ts and V4, and a dual-color two-pin LED D9. One end of capacitor C7 is connected to the anode of thyristor V1, one end of adjustable potentiometers R6 and R7, and the sliding end. The other end of adjustable potentiometer R7 is connected to the emitter of transistor Ts and one end of capacitor C8. The other ends of capacitors C8 and C7 are connected to reference ground. The collector of transistor Ts is connected to the gate of thyristor V1 and one end of resistor R8. The cathode of thyristor V1... One end of the adjustable potentiometer R9 and resistor R19 is connected to the base of transistor V4. The emitter of transistor V4 is connected to reference ground. The collector of transistor V4 is connected to the control power supply +15V through current-limiting resistor R26. The collector of transistor V4 is also connected to one end of resistor R25 and two-pin LED D9. The other ends of resistor R8 and resistor R25, the other end of adjustable potentiometer R9 and the sliding end are connected to reference ground. The other end of two-pin LED D9 is connected to the positive pulse terminal P+ of the stepper motor driver in the forward and backward drive circuit of the needle electrode motor.

[0022] The first voltage detection circuit in the three-channel voltage detection circuit includes a solid-state relay Op, an adjustable potentiometer R2, a light-emitting diode D6, a bicolor two-pin light-emitting diode D8, and current-limiting resistors R4 and R5. The anode of the control terminal of the solid-state relay Op is connected to the sliding terminal of the adjustable potentiometer R2. The cathode of the control terminal of the solid-state relay Op and one end of the adjustable potentiometer R2 are connected to the workpiece to be drilled. The other end of the adjustable potentiometer R2 is connected to the needle electrode. The anode of the output terminal of the solid-state relay Op is connected to a +15V power supply. The cathode of the output terminal of the solid-state relay Op is connected to the anode of the light-emitting diode D6 and one end of the bicolor two-pin light-emitting diode R8. The cathode of the light-emitting diode D6 is connected to the reference ground through the current-limiting resistor R5. The other end of the bicolor two-pin light-emitting diode D8 is connected to the positive direction terminal D+ of the stepper motor driver in the needle electrode motor forward and backward drive circuit through the current-limiting resistor R4.

[0023] The second voltage detection circuit in the three-channel voltage detection circuit includes a solid-state relay Op1, an adjustable potentiometer R21, and a current-limiting resistor R23. The anode of the control terminal of the solid-state relay Op1 is connected to the sliding terminal of the adjustable potentiometer R21. The cathode of the control terminal of the solid-state relay Op1 and one end of the adjustable potentiometer R21 are connected to the workpiece to be drilled. The other end of the adjustable potentiometer R21 is connected to the needle electrode. The anode of the output terminal of the solid-state relay Op1 is connected to a +15V control power supply through the current-limiting resistor R23. The cathode of the output terminal of the solid-state relay Op1 is connected to the pulse negative terminal P- of the stepper motor driver in the needle electrode motor forward and backward drive circuit.

[0024] The third voltage detection circuit in the three-channel voltage detection circuit includes a solid-state relay Op2, an adjustable potentiometer R22, and a pull-down resistor R24. The anode of the control terminal of the solid-state relay Op2 is connected to the sliding terminal of the adjustable potentiometer R22. One end of the adjustable potentiometer R22 is connected to a needle electrode. The cathode of the control terminal of the solid-state relay Op2 and the other end of the adjustable potentiometer R22 are connected to the workpiece to be drilled. The anode of the output terminal of the solid-state relay Op2 is connected to one end of the pull-down resistor R24 ​​and the pulse negative terminal P- of the stepper motor driver in the needle electrode motor forward and backward drive circuit. The cathode of the output terminal of the solid-state relay Op2 and the other end of the pull-down resistor R24 ​​are connected to reference ground.

[0025] Furthermore, the transistors Ts and V4 in the pulse generation control circuit are selected as S9011 transistors, and the solid-state relays Op, Op1 and Op2 in the second voltage detection circuit are selected as Dcm246 solid-state relays.

[0026] Furthermore, the start / stop control circuit includes a capacitor C9, a start button SB1, a stop button SB2, a needle electrode retraction button SB3, limit switches SQ1 and SQ2, thyristors V2 and V3, resistors R10 to R18, a light-emitting diode D7, and a check diode D10. One end of the capacitor C9 is connected to one end of the start button SB1, limit switch SQ2, and stop button SB2. The other end of the stop button SB2 is connected to a +15V control power supply. The other end of the start button SB1 is connected to the anode of the check diode D10 and one end of resistor R10. The cathode of the check diode D10 is connected to the anode of thyristor V2 and the other end of limit switch SQ2. The other end of resistor R10 is connected to one end of resistor R11 and the gate of thyristor V2. The thyristor V2 and its cathode are connected to resistors R12, R13, R14, and limit switches SQ1 and SQ2. The limit switch SQ1, one end of the needle electrode retract button SB3, and the anode of thyristor V3 are connected. The other end of resistor R13 is connected to the enable positive terminal E+ of the stepper motor driver in the needle electrode motor forward / reverse drive circuit. The other end of resistor R14 is connected to the anode of light-emitting diode D7, and the cathode of light-emitting diode D7 is connected to reference ground. The other end of the needle electrode retract button SB3 is connected to resistor R15 and the other end of limit switch SQ1. The other end of resistor R15 is connected to the gate of thyristor V3 and one end of resistor R16. The cathode of thyristor V3 is connected to one end of resistors R17 and R18. The other end of resistor R18 is connected to the direction negative terminal D- of the stepper motor driver in the needle electrode motor forward / reverse drive circuit. The other ends of resistors R17, R16, R12, R11, and capacitor C9 are connected to reference ground.

[0027] Furthermore, the thyristors V2 and V3 are selected as L0103MTRP thyristors.

[0028] Compared with existing technologies, the thyristor-based self-holding simplified metal EDM drilling device provided by this invention utilizes the characteristics of contact discharge ablation of charged electrode contacts and the self-holding property of the thyristor after conduction. It designs a mechanical mechanism for the metal EDM drilling device, as well as a start / stop control circuit, a voltage detection and pulse control circuit. The signals generated by these two circuits control the stepper motor of the drilling device to drive the equipment autonomously, achieving automated drilling of metal workpieces. Furthermore, it uses pulses generated by controlling the charging and discharging of the capacitor through the thyristor to drive the stepper motor, and leverages the self-holding characteristic of the thyristor to eliminate the need for bulky, high-power relays and easily interfered microcontrollers, achieving autonomous control of the EDM drilling device. This saves manpower, is low-cost, energy-efficient, and portable. Thyristors are current-controlled devices, less affected by electromagnetic interference, and superior to microcontroller control systems. They can operate stably in EDM machines. Furthermore, thyristors can operate continuously under relatively low current conditions, which helps reduce control power. The power consumption of the control system is lower than that of ordinary relay control systems. At the same time, by measuring the voltage between electrodes, instead of measuring the gap distance and fine control, the electrode feed and retraction strokes and times are shortened. This allows the discharge to occur at the distance between the two electrodes that is most conducive to electro-corrosion, thus improving processing efficiency. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the left side of the simple metal EDM drilling device based on thyristor self-holding provided by the present invention.

[0030] Figure 2 This is a schematic diagram of the right side of the simple metal EDM drilling device based on thyristor self-holding provided by the present invention.

[0031] Figure 3 This is a schematic diagram of the electrical drive and control unit circuit structure in the simple metal EDM drilling device based on thyristor self-holding provided by the present invention.

[0032] In the diagram, 1. Metal guide rail; 2. Horizontal shaft support; 3. Guide rail connecting bracket; 4. Linear bearing; 5. Stepper motor base; 6. Stepper motor; 7. Coupling; 8. Threaded rod; 9. Nut; 10. Needle electrode; 11. Needle electrode feed limit switch; 12. Needle electrode retraction limit switch; 13. Workpiece to be drilled; 100. Discharge main circuit; 200. Needle electrode motor forward and retraction drive circuit; 300. Voltage detection and pulse control circuit; 400. Start-stop control circuit. Detailed Implementation

[0033] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.

[0034] In the description of this invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] Please refer to Figures 1 to 3 As shown, this invention provides a simple metal EDM drilling device based on thyristor self-holding, comprising an EDM drilling machine mechanical unit and an electrical drive and control unit. The EDM drilling machine mechanical unit includes two parallel metal guide rails 1, with horizontal shaft supports 2 fixedly connected to both ends of the metal guide rails 1. A guide rail connecting bracket 3 is fixedly connected to the outer side of the horizontal shaft support 2 via screws. A linear bearing 4 is slidably sleeved on the metal guide rails 1, and a stepper motor base 5 is fixedly connected to the linear bearing 4. A stepper motor 6 is fixedly connected to the outer side of the stepper motor base 5. The main shaft of the stepper motor 6 is fixedly connected to a threaded rod 8 via a coupling 7. The outer end of the rod passes through the guide rail connecting bracket 3. A nut 9, which is fixedly connected to the guide rail connecting bracket 3, is sleeved on the threaded rod 8. A needle electrode 10 is fixedly connected to the side of the stepper motor base 5 away from the stepper motor 6. A needle electrode feed limit switch 11 is fixed on the metal guide rail 1 near the needle electrode 10. A needle electrode retraction limit switch 12 is fixed on the metal guide rail 1 near the stepper motor 6. A workpiece 13 to be drilled is fixed on the guide rail connecting bracket 3 on the side of the needle electrode 10. The electrical drive and control unit includes a discharge main circuit 100, a needle electrode motor advance and retraction drive circuit 200, a voltage detection and pulse control circuit 300, and a start / stop control circuit 400.

[0037] The discharge main circuit 100 is used to charge the energy storage capacitor after the generated DC voltage (such as DC48~60V) is passed through current limiting protection, thereby preparing for the discharge between the needle electrode 10 and the workpiece 13 to be drilled.

[0038] The start / stop control circuit 400 is used to receive start and stop operation commands from the operator, thereby controlling whether the drilling device starts or stops drilling operations, and outputs start / stop commands to the needle electrode motor forward / backward drive circuit 200.

[0039] The voltage detection and pulse control circuit 300 is used to detect the voltage of the energy storage capacitor through three adjustable potentiometers. Since the needle electrode and the workpiece to be drilled are respectively connected to the two electrodes of the energy storage capacitor, the detection of the voltage of the energy storage capacitor by the three adjustable potentiometers is also equivalent to the detection of the voltage of the two electrodes of the needle electrode and the workpiece to be drilled, so as to determine the contact state of the two electrodes, that is, whether they are in the state of short circuit, close-range open circuit, or long-range open circuit, and the judgment result is output to the needle electrode motor forward and backward drive circuit 200 as pulse and direction command signals.

[0040] The needle electrode motor forward and backward drive circuit 200 is used to receive the start and stop commands from the start and stop control circuit 400 under the excitation of the switching power supply, and to perform corresponding actions in combination with the pulse and direction command signals provided by the voltage detection and pulse control circuit 300, driving the stepper motor to rotate, and with the cooperation of the threaded rod 8 and the linear bearing 4, driving the tip of the needle electrode 10 to approach or move away from the workpiece 13 to be drilled.

[0041] As a specific embodiment, the metal guide rail 1 is made of 304 stainless steel, and the horizontal shaft support 2 is made of aluminum alloy. That is, the metal guide rail 1 is made of 304 stainless steel, and the horizontal shaft support 2 is made of aluminum alloy. Since 304 stainless steel has the characteristics of being lightweight and having excellent rigidity, it can improve the overall structural strength of the EDM drilling device.

[0042] For a specific embodiment, please refer to Figure 3As shown, the discharge main circuit 100 includes a fuse F1, a step-down transformer T, diodes D1-D4, capacitors C1-C5, an energy storage capacitor C0, a current-limiting resistor R1, and a needle electrode 10 and a workpiece 13 to be drilled in the mechanical unit. One end of the fuse F1 is connected to the external 220V single-phase AC live wire L, and the other end is connected to one end of the primary side of the step-down transformer T. The other end of the primary side of the step-down transformer T is connected to the external 220V single-phase AC neutral wire N. One end of the secondary side of the step-down transformer T is connected to one end of capacitors C0, C1, and C5, the positive terminal of diode D1, and the workpiece 13 to be drilled. C1 to C4, together with diodes D1 to D4, form a four-stage series rectifier circuit. The other end of capacitor C1 is connected to the cathode of diode D2, the anode of diode D3, and one end of capacitor C3. The anode of diode D2 is connected to one end of capacitors C2 and C4 and the cathode of diode D1. The other end of capacitor C2 is connected to the other end of the secondary side of step-down transformer T. The other end of capacitor C4 is connected to the cathode of diode D3 and the anode of diode D4. The cathode of diode D4 is connected to the other end of capacitor C3 and one end of capacitor C5 and current-limiting resistor R1. The other end of current-limiting resistor R1 is connected to the other end of capacitor C0 and pin electrode 10.

[0043] As a specific embodiment, the step-down transformer T is selected as a power frequency power transformer with a turns ratio of 220:12 and adopts a flat design, which helps to reduce the size of the power supply chassis.

[0044] For a specific embodiment, please refer to Figure 3 As shown, the needle electrode motor forward / backward drive circuit 200 includes a DC-15V switching power supply, a stepper motor driver Drv, and a stepper motor 6 in the mechanical unit. One end of the high-voltage side of the DC-15V switching power supply is connected to the output side of the fuse F1 in the discharge main circuit 100, and the other end of the high-voltage side of the DC-15V switching power supply is connected to the external 220V single-phase AC neutral line N. The V+ of the DC output side of the DC-15V switching power supply is connected to the DC+ terminal of the stepper motor driver Drv, and the V- of the DC output side of the DC-15V switching power supply is connected to the DC- terminal of the stepper motor driver Drv and serves as a reference ground. The A- and A+, B- and B+ terminals of the stepper motor driver are connected to the first phase A- and A+, and the second phase B- and B+ terminals of the stepper motor 6, respectively. The enable negative terminal E- of the stepper motor driver Drv is connected to the reference ground.

[0045] As a specific embodiment, the stepper motor driver Drv is a stepper motor driver with optical isolation. Optically isolated stepper motor drivers have the characteristics of strong anti-interference ability and higher voltage resistance. At the same time, the stepper motor driver can adjust the microstepping of the stepper motor.

[0046] As a specific embodiment, the stepper motor 6 is a two-phase stepper motor with a driving voltage of 9 to 42VDC. This type of stepper motor has the characteristics of high control precision, which can improve the control precision of the EDM drilling device.

[0047] For a specific embodiment, please refer to Figure 3 As shown, the voltage detection and pulse control circuit 300 includes a power supply stabilization and energization indication circuit, a pulse generation control circuit, and three voltage detection circuits; wherein,

[0048] The control power supply stabilization and energized indication circuit includes a reverse-blocking diode D0, a resistor R3, a light-emitting diode D5, and a capacitor C6. The anode of the reverse-blocking diode D0 is connected to V+ on the DC-15V output side of the switching power supply in the needle electrode motor forward / backward drive circuit 200. The cathode of the reverse-blocking diode D0 is connected to the +15V power supply and one end of the resistor R3 and capacitor C6. The other end of the resistor R3 is connected to the anode of the light-emitting diode D5. The cathode of the light-emitting diode D5 and the other end of the capacitor C6 are connected to reference ground. Among them, the capacitor C6 is used to temporarily store and stabilize the control circuit power supply voltage, the reverse-blocking diode D0 is used to prevent the control current from flowing backward due to the current shortage when the stepper motor driver Drv is operating, and the resistor R3 and the light-emitting diode D5 form the electrical indication circuit of the control power supply.

[0049] The pulse generation control circuit includes adjustable potentiometers R6, R7, and R9, resistors R8, R19, R25, and R26, a thyristor V1, temporary capacitors C7 and C8, transistors Ts and V4, and a bi-color two-pin LED D9. In the pulse generation control circuit centered on thyristor V1, one end of capacitor C7 is connected to the anode of thyristor V1, one end of adjustable potentiometers R6 and R7, and their sliding terminals. The other end of adjustable potentiometer R7 is connected to the emitter of transistor Ts and one end of capacitor C8. The other ends of capacitors C8 and C7 are connected to reference ground. The collector of transistor Ts is connected to the gate of thyristor V1 and one end of resistor R8. The cathode of the thyristor V1 is connected to one end of the adjustable potentiometer R9 and resistor R19. The other end of the resistor R19 is connected to the base of the transistor V4. The emitter of the transistor V4 is connected to the reference ground. The collector of the transistor V4 is connected to the control power supply +15V through the current limiting resistor R26. The collector of the transistor V4 is also connected to one end of the resistor R25 and the dual-color two-pin LED D9. The other ends of the resistors R8 and R25, the other end of the adjustable potentiometer R9, and the sliding end are connected to the reference ground. The other end of the dual-color two-pin LED D9 is connected to the positive pulse terminal P+ of the stepper motor driver in the forward and backward drive circuit of the needle electrode motor.

[0050] The first voltage detection circuit in the three-channel voltage detection circuit includes a solid-state relay Op, an adjustable potentiometer R2, an LED D6, a bicolor two-pin LED D8, and current-limiting resistors R4 and R5. The anode of the control terminal of the solid-state relay Op is connected to the sliding terminal of the adjustable potentiometer R2. The cathode of the control terminal of the solid-state relay Op and one end of the adjustable potentiometer R2 are connected to the workpiece 13 to be drilled. The other end of the adjustable potentiometer R2 is connected to the needle electrode 10. The anode of the output terminal of the solid-state relay Op is connected to a +15V power supply. The cathode of the output terminal of the solid-state relay Op is connected to the anode of the light-emitting diode D6 and one end of the bicolor two-pin light-emitting diode R8. The cathode of the light-emitting diode D6 is connected to the reference ground through the current-limiting resistor R5. The other end of the bicolor two-pin light-emitting diode D8 is connected to the positive direction terminal D+ of the stepper motor driver Drv in the needle electrode motor forward and backward drive circuit 200 through the current-limiting resistor R4, so as to complete the detection of the voltage of the needle electrode 10 and control the voltage of the positive direction terminal D+ of the stepper motor driver Drv to control the rotation direction of the stepper motor 6.

[0051] The second voltage detection circuit in the three-channel voltage detection circuit includes a solid-state relay Op1, an adjustable potentiometer R21, and a current-limiting resistor R23. The anode of the control terminal of the solid-state relay Op1 is connected to the sliding terminal of the adjustable potentiometer R21. The cathode of the control terminal of the solid-state relay Op1 and one end of the adjustable potentiometer R21 are connected to the workpiece 13 to be drilled. The other end of the adjustable potentiometer R21 is connected to the needle electrode 10. The anode of the output terminal of the solid-state relay Op1 is connected to a +15V control power supply through the current-limiting resistor R23. The cathode of the output terminal of the solid-state relay Op1 is connected to the pulse negative terminal P- of the stepper motor driver Drv in the needle electrode motor forward and backward drive circuit 200.

[0052] The third voltage detection circuit in the three-channel voltage detection circuit includes a solid-state relay Op2, an adjustable potentiometer R22, and a pull-down resistor R24. The anode of the control terminal of the solid-state relay Op2 is connected to the sliding terminal of the adjustable potentiometer R22. One end of the adjustable potentiometer R22 is connected to the needle electrode 10. The cathode of the control terminal of the solid-state relay Op2 and the other end of the adjustable potentiometer R22 are connected to the workpiece 13 to be drilled. The anode of the output terminal of the solid-state relay Op2 is connected to one end of the pull-down resistor R24 ​​and the pulse negative terminal P- of the stepper motor driver Drv in the needle electrode motor forward and backward drive circuit 200. The cathode of the output terminal of the solid-state relay Op2 and the other end of the pull-down resistor R24 ​​are connected to the reference ground.

[0053] In a specific embodiment, the transistors Ts and V4 in the pulse generation control circuit are selected as S9011 transistors. When the emitter-collector voltage reaches 9V, the emitter and base of this type of transistor break down, resulting in fast conduction speed, which is used to trigger the thyristor. The solid-state relays Op, Op1, and Op2 in the second voltage detection circuit are selected as Dcm246 solid-state relays. This type of solid-state relay has the characteristics of small size, low control current, good electrical isolation, and high control speed, which can reduce the power consumption of the control circuit of the EDM drilling device and improve the control speed.

[0054] For a specific embodiment, please refer to Figure 3 As shown, the start / stop control circuit 400 includes a capacitor C9, a start button SB1, a stop button SB2, a needle electrode retraction button SB3, limit switches SQ1 and SQ2 (SQ1 and SQ2 are respectively the needle electrode feed limit switch 11 and the needle electrode retraction limit switch 12 in the mechanical unit), thyristors V2 and V3, resistors R10 to R18, a light-emitting diode D7, and a check diode D10. One end of the capacitor C9 is connected to one end of the start button SB1, limit switch SQ2, and stop button SB2. The other end of the stop button SB2 is connected to a +15V control power supply. The other end of the start button SB1 is connected to the anode of the check diode D10 and one end of the resistor R10. The cathode of the check diode D10 is connected to the anode of the thyristor V2 and the other end of the limit switch SQ2. The other end of the resistor R10 is connected to one end of the resistor R11 and the gate of the thyristor V2. The thyristor V2 and its cathode are connected to the resistor R11. 12. Resistors R13 and R14, limit switch SQ1, one end of the needle electrode retraction button SB3, and the anode of thyristor V3 are connected. The other end of resistor R13 is connected to the enable positive terminal E+ of the stepper motor driver Drv in the needle electrode motor forward / backward drive circuit 200. The other end of resistor R14 is connected to the anode of light-emitting diode D7, and the cathode of light-emitting diode D7 is connected to reference ground. The other end of the needle electrode retraction button SB3 is connected to resistor R15 and the other end of limit switch SQ1. The other end of resistor R15 is connected to the gate of thyristor V3 and one end of resistor R16. The cathode of thyristor V3 is connected to one end of resistors R17 and R18. The other end of resistor R18 is connected to the negative terminal D- of stepper motor driver Drv in the needle electrode motor forward / backward drive circuit 200. The other ends of resistors R17, R16, R12, R11, and capacitor C9 are connected to reference ground.

[0055] In a specific embodiment, thyristors V2 and V3 are selected as L0103MTRP thyristors. This type of thyristor has low holding current and trigger current, which can reduce the power consumption of the EDM drilling device. Based on this, those skilled in the art can also select L0103MTRP thyristors for thyristor V1 in the aforementioned pulse generation control circuit.

[0056] In the simple metal EDM drilling device based on thyristor self-holding provided in this application, when the power supply to the EDM drilling device is connected, the main charging and discharging circuit 100 introduces the mains power through the overcurrent protection of fuse F1 into the step-down transformer T, reducing it to 12V AC power. Then, it is rectified and filtered by capacitors C1-C5 and diodes D1-D4 in series to become a 0-70V DC voltage (the voltage level depends on specific requirements). After current limiting protection by resistor R1, it charges the energy storage capacitor C0. Subsequently, the voltage of the energy storage capacitor C0 is sampled using a three-terminal adjustable potentiometer R2. When the voltage of the energy storage capacitor C0 reaches a predetermined value, the solid-state relay Op activates, and the output terminal (i.e., the secondary side) conducts; if the voltage of the energy storage capacitor C0 does not reach the predetermined value, the solid-state relay Op does not activate, and the output terminal does not conduct. The reason why a series rectifier circuit is used in the main charging and discharging circuit 100 is that the voltage between the two electrodes 10 and the workpiece 13 to be drilled is doubled before they come into contact and discharge, so as to meet the appropriate voltage value for discharge and drilling. At the same time, the amount of insulated enameled wire is reduced, and the size and weight of the transformer are reduced. At the same time, even if the needle electrode 10 and the workpiece 13 to be drilled are in a short circuit state after the needle electrode 10 comes into contact and discharges, the series rectifier circuit is a heavy load circuit after the short circuit. At this time, the resistance value of resistor R1 and the capacitance values ​​of capacitors C1-C4 are very small, and the capacitance values ​​of capacitors C1, C3 and C4 can be ignored. The circuit is actually converted into the right end of the secondary winding of the step-down transformer being connected in series with capacitor C2, and then D2, D3, D4 and R1 are connected in series in sequence. The lower end of R1 is then connected back to the left end of the secondary winding of the step-down transformer. Resistor R1 only receives the half-wave current pulse isolated by capacitor C2 after the secondary winding of the step-down transformer. The current-limiting resistor generates very little heat, which helps to reduce the resistance, power consumption and size of the current-limiting resistor, making the device lighter and more portable.

[0057] The needle electrode motor forward and backward drive circuit 200 introduces the mains power through the overcurrent protection of the fuse F1 to the DC-15V input terminal of the switching power supply. Then, a 15V control power supply is obtained on the DC-15V output side of the switching power supply to power the stepper motor driver Drv and the stepper motor 6. At the same time, it also powers the voltage detection and pulse control circuit 300 and the start / stop control circuit 400.

[0058] The voltage detection and pulse control circuit 300 takes the output of the DC-15V switching power supply, passes it through the anti-reverse diode D0, and then filters it with the filter capacitor C6 for noise reduction. After current limiting by the three-terminal adjustable potentiometer R6, it charges the temporary storage capacitor C7. At the same time, it charges the temporary storage capacitor C8 through the adjustable potentiometer R7. When the voltage of the temporary storage capacitor C8 rises to the breakdown voltage of the transistor Ts, the emitter and collector of the transistor Ts conduct, and the gate voltage of the thyristor V1 rises by one pulse, controlling the anode and cathode of the thyristor V1 to conduct. After the thyristor V1 conducts, the temporary storage capacitor C7 discharges through the signal resistor R9, and a high level is output at the upper end of the signal resistor R9. After the temporary capacitor C7 discharges through the signal resistor R9 for a period of time, the capacitor voltage decreases, and the current flowing through the thyristor V1 also decreases. When the current falls below the holding current of the thyristor V1, the thyristor V1 turns off. At this time, the signal resistor R9 is connected to the reference ground, and a low level appears at the upper end of the signal resistor R9, completing the generation of one pulse. The temporary capacitor C7 then enters the next cycle to recharge. The high and low pulse levels appearing at the upper end of the signal resistor R9, after being current-limited by resistor R19, control the base of transistor V4. Transistor V4 then turns on or off accordingly, establishing a high and low pulse level on the upper side of resistor R25. This pulse passes through the light-emitting diode D9 and is connected to the positive pulse terminal P+ of the stepper motor driver Drv, driving the stepper motor 6 to rotate. When the adjustable potentiometers R6, R7, and R9 are adjusted to suitable matching values, it can be ensured that P+ is a square wave pulse with a frequency of approximately 200 to 100 Hz. This facilitates the use of a stepper motor driver Drv with microstepping function to drive a two-phase stepper motor to a suitable speed.

[0059] When the voltage of the energy storage capacitor C0 reaches a predetermined value, the output terminal of the solid-state relay Op is turned on. The +15V high level passes sequentially through the anti-reverse diode D0, the secondary side (output terminal) of the solid-state relay Op, and the current-limiting resistor R4, and is applied to the positive control direction terminal D+ of the stepper motor driver Drv, controlling the two-phase stepper motor to rotate in the forward direction, causing the needle electrode 10 to advance and approach the workpiece 13 to be drilled. When the needle electrode 10 contacts and discharges with the workpiece 13, the workpiece 13 is slightly corroded by electro-corrosion. At the same time, the voltage on the energy storage capacitor C0 disappears, the voltage signal sampled by the tap (sliding terminal) of the adjustable potentiometer R2 returns to 0, and the output terminal of the solid-state relay Op is disconnected. The light-emitting diode D6 is turned off, and the positive control direction terminal D+ of the stepper motor driver Drv is pulled down by the current-limiting resistor R5, causing the needle electrode 10 to retract and separate from the workpiece 13. After the needle electrode 10 separates from the workpiece 13, the energy storage capacitor C0 is recharged through the power resistor R1. When the charging voltage reaches a predetermined value, it will enter the next cycle.

[0060] The start / stop control circuit uses a +15V power supply, which is filtered locally by capacitor C9. When the start button SB1 is pressed (the stop button SB2 should not be pressed at this time), a +15V high level is applied to the gate of thyristor V2 through signal resistor R10, causing thyristor V2 to conduct. At this time, the upper end of signal resistor R12 outputs a high level, which is applied to the enable positive terminal E+ of stepper motor driver Drv through signal resistor R13, allowing stepper motor driver Drv to receive direction control signal D+ and pulse signal P+, thus normally controlling the forward and reverse rotation of the two-phase stepper motor. Before the start button SB1 is pressed, thyristor V2 is not conducting. At this time, the upper end of signal resistor R12 outputs a low level, causing the A+, A-, B+, and B- terminals of stepper motor driver Drv to be disabled. Both windings of the two-phase stepper motor are not energized, and the motor does not move. When the start button SB1 is pressed, the stop button SB2 can be pressed at any time. The anode current of thyristor V2 will become 0, and then thyristor V2 will be turned off. Similarly, the A+, A-, B+, and B- outputs of the stepper motor driver Drv will be disabled.

[0061] Once the system is running, pressing the needle electrode retraction button SB3 at any time, or triggering the needle electrode feed limit switch SQ1, will trigger the gate of thyristor V3, causing the anode and cathode of thyristor V3 to conduct. A high level will be output from the upper end of signal resistor R17. This high level will raise the voltage at the negative terminal D- of the stepper motor driver Drv to a high level through signal resistor R18, thereby disabling the output of the optocoupler (this device selects a stepper motor driver Drv with optical isolation) from the positive terminal D+ to the negative terminal D- inside the stepper motor driver Drv. After this, the stepper motor 6 will continue to rotate in the opposite direction, and the needle electrode 10 will retract away from the workpiece 13 to be drilled until the limit switch SQ2 is triggered, the thyristor V2 will be disconnected, and the enable signal output from signal resistor R13 will be reset to 0, disabling the output of the stepper motor driver Drv.

[0062] If you wish to restart the system, you can press the start button SB1 directly. Although the needle electrode retraction limit switch SQ2 may be triggered before starting, and its normally closed switch is in an open state, the start button SB1 is a normally open button linked with the anti-reverse diode D10, which bypasses the needle electrode retraction limit switch SQ2, so the system can be started normally.

[0063] The above operation only considers the control logic of the control buttons and limit switches on this drilling device, and does not consider the control of the drilling device by the needle electrode voltage. When considering solid-state relays Op1 and Op2, the acquisition of the needle electrode voltage can replace the measurement of the distance between the needle electrode and the workpiece to be drilled, thereby achieving precise control of the distance between the two at the micrometer level. This greatly shortens the distance and time cost of the needle electrode's forward and backward movement between each charge and discharge cycle. Moreover, the micrometer-level distance provides the best discharge corrosion effect, avoiding short-circuit arcs at close range and spark discharges at long range. In short-circuit arc discharge, the discharge energy is concentrated inside the electrode, while in long-range spark discharge, the energy is distributed in the spark in the air, neither of which is on the surface of the workpiece to be drilled. Therefore, precise control of the two electrodes to discharge at close range achieves the goal of fast and efficient drilling.

[0064] like Figure 3 As shown, when the system is powered on and the SB1 button is pressed to start, the E+ terminal of the stepper motor driver Drv is enabled. If the voltage across the energy storage capacitor C0 is close to 0, the solid-state relays Op, Op1, and Op2 will not operate. The pulse negative terminal P- of the stepper motor driver Drv is pulled down to a low level by the pull-down resistor R24, and the cathode of the dual-color two-pin LED D9 outputs a pulse. The direction negative terminal D- of the stepper motor driver Drv is pulled down to a low level by resistors R18 and R17. The dual-color two-pin LED D8 and resistor R4 in the output branch of the solid-state relay Op are both at a low level. At this time, the stepper motor driver Drv drives the stepper motor to move backward / backward. After the needle electrode separates from the workpiece to be drilled, the voltage of the energy storage capacitor C0 and the needle electrode gradually increases. Because capacitor C5 charges with current limiting through resistor R1, when the voltage rises to the point where solid-state relay Op1 activates (e.g., 20V), the output of solid-state relay Op1 is turned on, and +15V power is applied to the negative pulse terminal P- of the stepper motor driver Drv through resistor R23. That is, the negative pulse terminal P- is pulled up by resistor R23. At this time, the pulse output from the anode to the cathode of the dual-color two-pin LED D9 is blocked, and the positive pulse terminal P+ of the stepper motor driver Drv cannot drive the internal optocoupler. The driver does not receive the pulse and therefore will not drive the stepper motor to rotate, entering a waiting state. In this state, if the needle electrode voltage continues to rise to a certain value, a discharge will occur between the needle electrode and the workpiece to be drilled. If discharge occurs, the voltage will rise again from 0, entering the next boost and discharge cycle. If no discharge occurs, the voltage will rise until solid-state relay Op2 activates.

[0065] The setting voltage of solid-state relay Op is set slightly lower than that of solid-state relay Op2, but higher than that of solid-state relay Op1. At this moment, because the output of solid-state relay Op is conducting, the positive terminal D+ of the stepper motor driver Drv is at a high level, the output of solid-state relay Op1 is also conducting, and the negative terminal P- of the stepper motor driver Drv is at a low level. Therefore, the stepper motor driver Drv drives the stepper motor to feed. Simultaneously with the feeding, the voltage of the needle electrode gradually increases until a discharge occurs between the needle electrode and the workpiece to be drilled, at which point the voltage returns to 0.

[0066] Compared with existing technologies, the thyristor-based self-holding simplified metal EDM drilling device provided by this invention utilizes the characteristics of contact discharge ablation of charged electrode contacts and the self-holding property of the thyristor after conduction. It designs a mechanical mechanism for the metal EDM drilling device, as well as a start / stop control circuit, a voltage detection and pulse control circuit. The signals generated by these two circuits control the stepper motor of the drilling device to drive the equipment autonomously, achieving automated drilling of metal workpieces. Furthermore, it uses pulses generated by controlling the charging and discharging of the capacitor through the thyristor to drive the stepper motor, and leverages the self-holding characteristic of the thyristor to eliminate the need for bulky, high-power relays and easily interfered microcontrollers, achieving autonomous control of the EDM drilling device. This saves manpower, is low-cost, energy-efficient, and portable. Thyristors are current-controlled devices, less affected by electromagnetic interference, and superior to microcontroller control systems. They can operate stably in EDM machines. Furthermore, thyristors can operate continuously under relatively low current conditions, which helps reduce control power. The power consumption of the control system is lower than that of ordinary relay control systems. At the same time, by measuring the voltage between electrodes, instead of measuring the gap distance and fine control, the electrode feed and retraction strokes and times are shortened. This allows the discharge to occur at the distance between the two electrodes that is most conducive to electro-corrosion, thus improving processing efficiency.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A simple metal EDM drilling device based on thyristor self-holding, characterized in that, The device includes a mechanical unit and an electrical control unit for an electrical discharge machining (EDM) machine. The mechanical unit comprises two parallel metal guide rails. Horizontal shaft supports are fixedly connected to both ends of the metal guide rails. Guide rail connecting brackets are fixedly connected to the outer sides of the horizontal shaft supports. Linear bearings are slidably sleeved on the metal guide rails. A stepper motor base is fixedly connected to the linear bearing. A stepper motor is fixedly connected to the outer side of the stepper motor base. A threaded rod is fixedly connected to the spindle of the stepper motor via a coupling. The outer end of the threaded rod passes through the guide rails and connects to… The bracket includes a threaded rod fitted with a nut that is fixedly connected to the guide rail connecting bracket. A needle electrode is fixedly connected to the side of the stepper motor base opposite to the stepper motor. A needle electrode feed limit switch is fixed on the metal guide rail near the needle electrode, and a needle electrode retraction limit switch is fixed on the metal guide rail near the stepper motor. A workpiece to be drilled is fixed on the guide rail connecting bracket on the side of the needle electrode. The electrical drive and control unit includes a discharge main circuit, a needle electrode motor advance and retraction drive circuit, a voltage detection and pulse control circuit, and a start / stop control circuit. The main discharge circuit is used to charge the energy storage capacitor with the generated DC voltage after passing through current limiting protection, thereby preparing for the discharge between the needle electrode and the workpiece to be drilled. The start / stop control circuit is used to receive start and stop operation commands from the operator, thereby controlling whether the drilling device starts or stops drilling operations, and outputs start / stop commands to the needle electrode motor forward and backward drive circuit. The voltage detection and pulse control circuit is used to detect the voltage of the energy storage capacitor through three adjustable potentiometers, which is equivalent to detecting the voltage of the two electrodes of the needle electrode and the workpiece to be drilled, thereby determining whether the two electrodes are in a short circuit, close-range open circuit, or long-range open circuit state, and outputting the judgment result to the needle electrode motor advance and retreat drive circuit as pulse and direction command signals. The needle electrode motor forward / backward drive circuit, under the excitation of the switching power supply, receives start / stop commands from the start / stop control circuit and, in conjunction with pulse and direction command signals provided by the voltage detection and pulse control circuit, performs corresponding actions to drive the stepper motor to rotate. With the cooperation of the threaded rod and the linear bearing, it moves the tip of the needle electrode closer to or further away from the workpiece to be drilled. The voltage detection and pulse control circuit includes a power supply stabilization and energization indication circuit, a pulse generation control circuit, and a three-channel voltage detection circuit. The pulse generation control circuit includes adjustable potentiometers R6, R7, and R9; resistors R8, R19, R25, and R26; a thyristor V1; temporary capacitors C7 and C8; transistors Ts and V4; and a dual-color two-pin LED D9. One end of capacitor C7 is connected to the anode of thyristor V1, one end of adjustable potentiometers R6 and R7, and the sliding end. The other end of adjustable potentiometer R7 is connected to the emitter of transistor Ts and one end of capacitor C8. The other ends of capacitors C8 and C7 are connected to reference ground. The collector of transistor Ts is connected to the gate of thyristor V1 and one end of resistor R8. The cathode of thyristor V1 is connected to adjustable potentiometer R9 and one end of resistor R19. The other end of resistor R19 is connected to the transistor... The base of transistor V4 is connected to the reference ground, and the collector of transistor V4 is connected to the control power supply +15V through the current limiting resistor R26. The collector of transistor V4 is also connected to resistor R25 and one end of the dual-color two-pin LED D9. The other ends of resistors R8 and R25, the other end of the adjustable potentiometer R9, and the sliding end are connected to the reference ground. The other end of the dual-color two-pin LED D9 is connected to the positive pulse terminal P+ of the stepper motor driver in the forward and backward drive circuit of the pin electrode motor.

2. The simple metal EDM drilling device based on thyristor self-holding as described in claim 1, characterized in that, The metal guide rail is made of 304 stainless steel, and the horizontal shaft support is made of aluminum alloy.

3. The simple metal EDM drilling device based on thyristor self-holding as described in claim 1, characterized in that, The main discharge circuit includes a fuse F1, a step-down transformer T, diodes D1-D4, capacitors C1-C5, an energy storage capacitor C0, a current-limiting resistor R1, and a needle electrode and the workpiece to be drilled in the mechanical unit. One end of the fuse F1 is connected to the external 220V single-phase AC live wire, and the other end is connected to one end of the primary winding of the step-down transformer T. The other end of the primary winding of the step-down transformer T is connected to the external 220V single-phase AC neutral wire. One end of the secondary winding of the step-down transformer T is connected to one end of capacitors C0, C1, and C5, the positive terminal of diode D1, and the workpiece to be drilled. Capacitors C1-C4 are connected to the diode D1 and the workpiece to be drilled. Diodes D1 to D4 together form a four-stage series rectifier circuit. The other end of capacitor C1 is connected to the cathode of diode D2, the anode of diode D3, and one end of capacitor C3. The anode of diode D2 is connected to one end of capacitors C2 and C4 and the cathode of diode D1. The other end of capacitor C2 is connected to the other end of the secondary side of step-down transformer T. The other end of capacitor C4 is connected to the cathode of diode D3 and the anode of diode D4. The cathode of diode D4 is connected to the other end of capacitor C3, one end of capacitor C5, and one end of current-limiting resistor R1. The other end of current-limiting resistor R1 is connected to the other end of capacitor C0 and the pin electrode.

4. The simple metal EDM drilling device based on thyristor self-holding as described in claim 3, characterized in that, The step-down transformer T is selected as a power frequency power transformer with a turns ratio of 220:12 and adopts a flat design.

5. The simple metal EDM drilling device based on thyristor self-holding as described in claim 1, characterized in that, The needle electrode motor forward and backward drive circuit includes a DC-15V switching power supply, a stepper motor driver, and a stepper motor in the mechanical unit. One end of the high-voltage side of the DC-15V switching power supply is connected to the output side of the fuse F1 in the main discharge circuit, and the other end of the high-voltage side of the DC-15V switching power supply is connected to the external 220V single-phase AC neutral line. The V+ of the DC output side of the DC-15V switching power supply is connected to the DC+ terminal of the stepper motor driver, and the V- of the DC output side of the DC-15V switching power supply is connected to the DC- terminal of the stepper motor driver and serves as a reference ground. The A- and A+, B- and B+ terminals of the stepper motor driver are connected to the first phase A- and A+, and the second phase B- and B+ terminals of the stepper motor, respectively. The enable negative terminal E- of the stepper motor driver is connected to the reference ground.

6. The simple metal EDM drilling device based on thyristor self-holding as described in claim 5, characterized in that, The stepper motor driver is selected as an optically isolated stepper motor driver.

7. The simple metal EDM drilling device based on thyristor self-holding as described in claim 1, characterized in that, The control power supply stabilization and energized indication circuit includes a reverse-blocking diode D0, a resistor R3, a light-emitting diode D5, and a capacitor C6. The anode of the reverse-blocking diode D0 is connected to V+ on the DC-15V output side of the switching power supply in the forward and reverse drive circuit of the needle electrode motor. The cathode of the reverse-blocking diode D0 is connected to a +15V power supply and one end of the resistor R3 and capacitor C6. The other end of the resistor R3 is connected to the anode of the light-emitting diode D5. The cathode of the light-emitting diode D5 and the other end of the capacitor C6 are connected to reference ground. The first voltage detection circuit in the three-channel voltage detection circuit includes a solid-state relay Op, an adjustable potentiometer R2, a light-emitting diode D6, a bicolor two-pin light-emitting diode D8, and current-limiting resistors R4 and R5. The anode of the control terminal of the solid-state relay Op is connected to the sliding terminal of the adjustable potentiometer R2. The cathode of the control terminal of the solid-state relay Op and one end of the adjustable potentiometer R2 are connected to the workpiece to be drilled. The other end of the adjustable potentiometer R2 is connected to the needle electrode. The anode of the output terminal of the solid-state relay Op is connected to a +15V power supply. The cathode of the output terminal of the solid-state relay Op is connected to the anode of the light-emitting diode D6 and one end of the bicolor two-pin light-emitting diode R8. The cathode of the light-emitting diode D6 is connected to the reference ground through the current-limiting resistor R5. The other end of the bicolor two-pin light-emitting diode D8 is connected to the positive direction terminal D+ of the stepper motor driver in the needle electrode motor forward and backward drive circuit through the current-limiting resistor R4. The second voltage detection circuit in the three-channel voltage detection circuit includes a solid-state relay Op1, an adjustable potentiometer R21, and a current-limiting resistor R23. The anode of the control terminal of the solid-state relay Op1 is connected to the sliding terminal of the adjustable potentiometer R21. The cathode of the control terminal of the solid-state relay Op1 and one end of the adjustable potentiometer R21 are connected to the workpiece to be drilled. The other end of the adjustable potentiometer R21 is connected to the needle electrode. The anode of the output terminal of the solid-state relay Op1 is connected to a +15V control power supply through the current-limiting resistor R23. The cathode of the output terminal of the solid-state relay Op1 is connected to the pulse negative terminal P- of the stepper motor driver in the needle electrode motor forward and backward drive circuit. The third voltage detection circuit in the three-channel voltage detection circuit includes a solid-state relay Op2, an adjustable potentiometer R22, and a pull-down resistor R24. The anode of the control terminal of the solid-state relay Op2 is connected to the sliding terminal of the adjustable potentiometer R22. One end of the adjustable potentiometer R22 is connected to a needle electrode. The cathode of the control terminal of the solid-state relay Op2 and the other end of the adjustable potentiometer R22 are connected to the workpiece to be drilled. The anode of the output terminal of the solid-state relay Op2 is connected to one end of the pull-down resistor R24 ​​and the pulse negative terminal P- of the stepper motor driver in the needle electrode motor forward and backward drive circuit. The cathode of the output terminal of the solid-state relay Op2 and the other end of the pull-down resistor R24 ​​are connected to reference ground.

8. The simple metal EDM drilling device based on thyristor self-holding as described in claim 7, characterized in that, The transistors Ts and V4 in the pulse generation control circuit are selected as S9011 transistors, and the solid-state relays Op, Op1 and Op2 in the three voltage detection circuits are selected as Dcm246 solid-state relays.

9. The simple metal EDM drilling device based on thyristor self-holding as described in claim 1, characterized in that, The start / stop control circuit includes a capacitor C9, a start button SB1, a stop button SB2, a needle electrode retraction button SB3, limit switches SQ1 and SQ2, thyristors V2 and V3, resistors R10~R18, an LED D7, and a check diode D10. One end of the capacitor C9 is connected to one end of the start button SB1, limit switch SQ2, and stop button SB2. The other end of the stop button SB2 is connected to a +15V control power supply. The other end of the start button SB1 is connected to the anode of the check diode D10 and one end of resistor R10. The cathode of the check diode D10 is connected to the anode of thyristor V2 and the other end of limit switch SQ2. The other end of resistor R10 is connected to one end of resistor R11 and the gate of thyristor V2. The thyristor V2 and its cathode are connected to resistors R12, R13, R14, and the limit switch SQ2. The pin electrode retraction button SB3 is connected to one end of SQ1 and the anode of thyristor V3. The other end of resistor R13 is connected to the enable positive terminal E+ of the stepper motor driver in the pin electrode motor forward / backward drive circuit. The other end of resistor R14 is connected to the anode of LED D7, and the cathode of LED D7 is connected to reference ground. The other end of pin electrode retraction button SB3 is connected to resistor R15 and the other end of limit switch SQ1. The other end of resistor R15 is connected to the gate of thyristor V3 and one end of resistor R16. The cathode of thyristor V3 is connected to one end of resistors R17 and R18. The other end of resistor R18 is connected to the direction negative terminal D- of the stepper motor driver in the pin electrode motor forward / backward drive circuit. The other ends of resistors R17, R16, R12, R11, and capacitor C9 are connected to reference ground.

10. The simple metal EDM drilling device based on thyristor self-holding as described in claim 9, characterized in that, The thyristors V2 and V3 are selected as L0103MTRP thyristors.

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