A method for controlling the rate of change of current in an electric spark pulse power supply

Abstract

This invention provides a method for controlling the rate of change of current in an electrical discharge pulse power supply. The electrical discharge pulse power supply includes a high-voltage breakdown circuit for gap breakdown machining in electrical discharge processing, a constant current source circuit for controlling the peak current of the pulse discharge, and a current waveform control circuit for controlling the rate of change of current at the leading and trailing edges of the output current waveform. The pulse power supply of this invention adopts an energy-saving design, eliminating power consumption and heat dissipation problems caused by current-limiting resistors in traditional power supplies. It meets different needs in actual processing and has better market applicability. It can effectively control the output current waveform to rise and fall at a certain slope, increasing the variety of output current waveforms, resulting in high processing efficiency and low electrode loss, thus meeting different processing requirements in actual production.

Description

Technical Field

[0001] This invention belongs to the field of electrical discharge machining power supply technology, specifically relating to a method for controlling the rate of change of current in an electrical discharge pulse power supply. Background Technology

[0002] Electrical discharge machining (EDM) is a non-contact special machining technology that uses pulsed energy between a tool electrode and a workpiece to remove material. With the emergence of new materials, such as high-temperature alloys and other high-performance but difficult-to-machine materials, EDM is widely used in aerospace, mold manufacturing, and other fields. Compared to traditional machining, EDM avoids many machining problems caused by contact machining, such as insufficient precision and deformation of small dimensions. Furthermore, it can process special metal materials with high hardness, high strength, and high melting points, as well as some precision parts with complex structures and shapes.

[0003] The variation of discharge energy in electrical discharge machining (EDM) is crucial in determining machining efficiency and quality, and discharge energy control primarily depends on the regulation of the discharge current. Therefore, pulse power supplies are particularly important for EDM. Currently, some traditional power supplies still in use consume most of their energy in current-limiting resistors, resulting in low power efficiency. With increasing demands for energy conservation, environmental protection, and high precision, high efficiency, and low tool wear in machined parts, there is a growing need for pulse power supplies to achieve even lower energy consumption and lower tool wear.

[0004] Currently, in most machining applications, the current waveform output by an EDM pulse power supply approximates a triangular or square wave. Literature indicates that the rate of change of the leading and trailing edges of the output current waveform significantly affects electrode wear. For difficult-to-machine materials such as those with high melting points and high hardness, sufficient energy is required to provide explosive force, resulting in a rapid rise and steep slope of the current leading edge. However, for machining processes requiring low electrode wear and good surface quality, a gentler rise and steeper slope of the current leading edge are preferable. But the energy cannot be too low, otherwise machining time will increase; therefore, the trailing edge of the current waveform cannot fall too quickly and must have a certain pulse width to ensure stable discharge. Combining different machining conditions and requirements necessitates special output current waveforms to meet diverse needs. Patent document CN108422055B discloses a pulse power supply and its current waveform control method. This method eliminates the current-limiting resistor of traditional power supplies, improving energy utilization, and designs the output current rising edge to rise to a certain extent, increasing the variety of output current waveforms. However, this design does not change the falling edge of the current, and the rate of change of the rising edge current is relatively small.

[0005] Existing energy-saving pulse power supplies have relatively simple output current waveforms, making it difficult to simultaneously meet the requirements of high-performance machining. Therefore, solving the waveform control problem of the output current of energy-saving power supplies is one of the important research directions in the field of electrical discharge machining.

[0006] Regarding the problems in the relevant technologies, no effective solutions have yet been proposed in this field. Summary of the Invention

[0007] The present invention provides an electrical discharge pulse power supply, wherein the improvement is that the electrical discharge pulse power supply includes a high-voltage breakdown circuit for gap breakdown processing of electrical discharge machining, a constant current source circuit for controlling the peak current of pulse discharge, and a current waveform control circuit for controlling the rate of change of the leading and trailing edges of the output current waveform.

[0008] The high-voltage breakdown circuit includes a second DC power supply V2, a first resistor R1, a second power switch Q2, a third diode D3, and a discharge gap; the second power switch Q2 is connected to a processing timing controller.

[0009] The constant current source circuit includes a constant current source charging circuit and a constant current source freewheeling circuit;

[0010] The constant current source charging circuit includes a DC first power supply V1, a first power switch Q1, a current sensor, a first inductor L1, and a first diode D1. A current closed-loop controller is connected to the first power switch Q1 of the constant current source charging circuit, and the current sensor is connected in series between the first power switch Q1 and the first inductor L1 of the constant current source charging circuit.

[0011] When the first power switch Q1 is disconnected, the second power switch Q2 is disconnected, and the discharge gap is not broken down, the first inductor L1, the first diode D1, the second DC power supply V2, and the second diode D2 constitute a constant current source freewheeling circuit.

[0012] When the first power switch Q1 is open and the second power switch Q2 is closed, and the discharge gap is broken down, the first inductor L1, the second power switch Q2, the parallel second resistor R2 and inductor L, the third diode D3, the discharge gap and the second diode D2 constitute a constant current source freewheeling circuit.

[0013] The current waveform control circuit consists of at least two switches, at least two inductors, a second resistor R2, a third diode D3, a discharge gap, and a fourth diode D4.

[0014] Preferably, the constant current source circuit includes a low-voltage constant current source circuit, which is a low-voltage current output circuit.

[0015] Preferably, the at least two switches and at least two inductors are connected in parallel with the second resistor R2.

[0016] Furthermore, the current waveform control circuit is composed of a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, a second inductor L2, a third inductor L3, a fourth inductor L4, a fifth inductor L5, a second resistor R2, a third diode D3, a discharge gap, and a fourth diode D4.

[0017] Preferably, the constant current source circuit is continuously charged before the gap is broken down. When the gap is broken down, the high voltage breakdown circuit and the constant current source circuit form a discharge current circuit, and the current change rate of the output current waveform at the leading and trailing edges is controlled by the current waveform control circuit.

[0018] Preferably, the discharge current circuit consists of a first DC power supply V1, a second DC power supply V2, a first power switch Q1, a first inductor L1, a second power switch Q2, a second resistor R2, a third diode D3, and a discharge gap.

[0019] Furthermore, the first power switch and the second power switch are either field-effect transistors or insulated-gate bipolar transistors.

[0020] Furthermore, different inductance parameter circuits can be selected and combined through the switch control.

[0021] Furthermore, the current closed-loop controller uses PWM control.

[0022] The present invention also provides a method for controlling the rate of change of current in an electric spark pulse power supply, wherein the improvement is that the method includes

[0023] (1) The constant current source circuit continuously stores energy before the discharge gap breaks down;

[0024] (2) The high voltage breakdown circuit continuously increases the voltage to break down the discharge gap. The current closed-loop controller receives the detection signal of the discharge gap breakdown and sets the target current value.

[0025] (3) The second power switch closed loop is turned on, and the inductor current is output to the current waveform control loop;

[0026] (4) Select the processing mode by switching the first switch S1 on and off;

[0027] (5) The processing timing controller controls the pulse width and pulse interval of the output current;

[0028] (6) Different inductance parameters are combined by switching control, and the current waveform control loop controls the current slope to rise or fall.

[0029] Beneficial effects:

[0030] This invention's pulse power supply adopts an energy-saving design, eliminating power consumption and heat dissipation problems caused by current-limiting resistors in traditional power supplies. It is more environmentally friendly and energy-efficient, with lower electrode losses, higher processing efficiency, and a wider variety of output current waveforms to meet different needs in actual processing, thus having better market applicability.

[0031] This invention can effectively control the output current waveform to rise and fall at a certain slope, increase the variety of output current waveforms, and achieve high processing efficiency and low electrode loss to meet different processing needs in actual production.

[0032] It should be understood that the above general description and the following specific embodiments are merely exemplary and illustrative, and do not limit the scope of the claims made in this application. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of an electric spark pulse power supply process according to the present invention;

[0034] Figure 2 A schematic diagram of current waveform changes in an electric spark pulse power supply according to the present invention. Figure 1 ;

[0035] Figure 3 A schematic diagram of current waveform changes in an electric spark pulse power supply according to the present invention. Figure 2 ;

[0036] Figure 4 A schematic diagram of current waveform changes in an electric spark pulse power supply according to the present invention. Figure 3 ;

[0037] In the diagram, V1 is the first DC power supply, V2 is the second DC power supply, Q1 is the first power switch, Q2 is the second power switch, L is an inductor, L1 is the first inductor, L2 is the second inductor, L3 is the third inductor, L4 is the fourth inductor, L5 is the fifth inductor, R1 is the first resistor, R2 is the second resistor, D1 is the first diode, D2 is the second diode, D3 is the third diode, D4 ​​is the fourth diode, S1 is the first switch, S2 is the second switch, S3 is the third switch, S4 is the fourth switch, S5 is the fifth switch, and S6 is the sixth switch.

[0038] It should be understood that the accompanying drawings are not necessarily drawn to scale and present slightly simplified representations of various features illustrating the basic principles of this disclosure. Specific design features of the invention as disclosed herein, including, for example, particular dimensions, orientations, positions, and shapes, will be determined in part by the specifically intended application and usage environment.

[0039] In the figures, throughout the several figures, reference numerals refer to the same or equivalent parts of the invention. Detailed Implementation

[0040] Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawings and described below. Although the invention will be described in conjunction with exemplary embodiments thereof, it should be understood that this specification is not intended to limit the invention to those exemplary embodiments. On the other hand, the invention is intended to cover not only the exemplary embodiments thereof, but also various alternatives, modifications, equivalents and other embodiments that may be included within the spirit and scope of the invention as defined by the appended claims.

[0041] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The specific structures and functions described in the exemplary embodiments of the present invention are for illustrative purposes only. Embodiments of the present invention can be implemented in various forms, and it should be understood that they should not be construed as limited to the exemplary embodiments described in the exemplary embodiments, but include all modifications, equivalents, or substitutions included within the spirit and scope of the present invention.

[0042] Throughout this specification, the technical terms used are for the purpose of describing various exemplary embodiments only and are not intended to be limiting. It will be further understood that the terms "comprising," "including," "having," etc., when used in the exemplary embodiments, specifically refer to the presence of the stated components, steps, operations, or elements, but do not exclude the presence or addition of one or more other components, steps, operations, or elements.

[0043] This invention discloses a method for controlling the rate of change of current in an electrical discharge pulse power supply. Specifically, it is a method for controlling the rate of change of current along the leading and trailing edges of the current waveform in an electrical discharge pulse power supply, which can reduce electrode losses. It considers different rising and falling output current waveforms in actual machining designs to meet machining requirements. The method includes a high-voltage breakdown circuit, a low-voltage constant current source circuit, a current waveform control circuit, a current closed-loop controller, and a detection unit. The high-voltage breakdown circuit is used to break down the discharge gap between the electrode and the workpiece. The low-voltage constant current circuit includes a constant current source charging circuit and a constant current source freewheeling circuit to provide continuous charging and discharging. The discharge and breakdown signals of the discharge gap received from the detection unit are sent to the current closed-loop controller to control the set current value. The current waveform control circuit controls the degree of rise and fall of the output current waveform. The novel pulse power supply designed in this invention is more energy-efficient and environmentally friendly, with lower electrode losses, higher machining efficiency, more types of output current waveforms, and meets different needs in actual machining, resulting in better market applicability.

[0044] like Figure 1 As shown, the present invention provides an electric spark pulse power supply, including a high-voltage breakdown circuit, a constant current source circuit, and a current waveform control circuit.

[0045] The constant current source circuit includes a low-voltage constant current source circuit, which is a low-voltage current output circuit.

[0046] The constant current source circuit includes a constant current source charging circuit and a constant current source freewheeling circuit;

[0047] The constant current source charging circuit comprises a DC first power supply V1, a first power switch Q1, a current sensor, a first inductor L1, and a first diode D1; the constant current source charging circuit is turned on to store energy before the gap breaks down.

[0048] When the first power switch Q1 is disconnected, the second power switch Q2 is disconnected, and the discharge gap is not broken down, the first inductor L1, the first diode D1, the second DC power supply V2, and the second diode D2 constitute a constant current source freewheeling circuit.

[0049] When the first power switch Q1 is open and the second power switch Q2 is closed, and the discharge gap is broken down, the first inductor L1, the second power switch Q2, the parallel second resistor R2 and inductor L, the third diode D3, the discharge gap and the second diode D2 constitute a constant current source freewheeling circuit.

[0050] In the above technical solution, the high-voltage section of the electrical discharge pulse power supply consists of a second DC power supply V2, a first resistor R1, a second power switch Q2, a second resistor R2, and a third diode D3, used to break down the discharge gap between the electrode and the workpiece. After the gap is broken down, the high and low voltage sections of the power supply work together to output current to the gap, providing a continuous current. When the first power switch Q1 is closed, the first DC power supply V1 and the second DC power supply V2 jointly charge the first inductor L1. The current flows through the first inductor L1, the third diode D3, and the parallel inductor L and the second resistor R2 before flowing to the discharge gap. The timing controller controls the pulse width and pulse interval of the output current.

[0051] The current waveform control circuit consists of at least two switches, at least two inductors, a second resistor R2, a third diode D3, a discharge gap, and a fourth diode D4.

[0052] The at least two switches and at least two inductors are connected in parallel with the second resistor R2.

[0053] The current waveform control circuit is composed of a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, etc., a second inductor L2, a third inductor L3, a fourth inductor L4, a fifth inductor L5, a second resistor R2, a third diode D3, a discharge gap, and a fourth diode D4.

[0054] In the above technical solution, when the second power switch Q2 is closed and the first switch S1 is closed, the current output from the high and low voltage circuit flows through the third diode D3 to the discharge gap. When the second power switch Q2 is open and the first switch S1 is closed, the current from the first inductor L1 flows through the second power switch Q2, the third diode D3, the second diode D2 in the discharge gap, and the current sensor to form a circuit, and the output current is a processing mode.

[0055] In the above technical solution, different inductance parameters L are formed by controlling the switch combination. The second power switch Q2 is closed, the first switch S1 is open, and the output current flows through the parallel second resistor R2, the parallel inductor L, the fourth diode D4, and the discharge gap. The second resistor R2 sets an initial current for the current-limiting resistor, accelerating the energy supply between the electrodes. When the second power switch Q2 is turned off, the energy stored in the inductor L continues to discharge through the gap, and the current flows through the parallel second inductor L, the third diode D3, the discharge gap, and the second diode D2. Due to the characteristic that the inductance cannot change abruptly, the current slope is controlled. The output current follows a processing mode. Under the action of the current closed-loop PWM control mechanism, the energy stored in the inductor is continuously stored and released. Different slopes are achieved by changing the inductance parameters.

[0056] The present invention also provides a method for controlling the rate of change of current in an electric spark pulse power supply, the method comprising:

[0057] (1) The constant current source circuit continuously stores energy before the discharge gap breaks down;

[0058] (2) The high voltage breakdown circuit continuously increases the voltage to break down the discharge gap. The current closed-loop controller receives the detection signal of the discharge gap breakdown and sets the target current value.

[0059] (3) The second power switch closed loop is turned on, and the inductor current is output to the current waveform control loop;

[0060] (4) Select the processing mode by switching the first switch S1 on and off;

[0061] (5) The processing timing controller controls the pulse width and pulse interval of the output current;

[0062] (6) Taking advantage of the characteristic that the current of an inductor cannot change abruptly, different inductor parameters are combined by switching control. The current waveform control circuit controls the current to rise or fall at a certain slope.

[0063] The waveform change process is as follows: Figure 2 As shown, the traditional output current waveform is a square wave, and the leading and trailing edges of the output current remain unchanged. Figure 3 As shown, when the second power switch Q2 is closed and the first switch S1 is closed, the slope of the leading edge of the current waveform changes significantly while the trailing edge remains unchanged. Figure 4As shown, different inductance parameters L are formed by controlling the combination of switches. The second power switch Q2 is closed and the first switch S1 is open. The current waveform of the output current waveform has obvious current change rate at the leading and trailing edges. The slope of the output current is also different according to the different inductance values ​​formed by the combination.

[0064] The output current waveform control method of the present invention can be used as a commonly used control method for energy-saving pulse power supplies that use inductors as output current filtering elements. This method can increase the variety of output current waveforms, thereby improving processing performance and better meeting the needs of use.

[0065] The foregoing description of specific exemplary embodiments of the invention has been presented for purposes of illustration and description. It is not intended to exclude or limit the invention to the precise forms disclosed, and it will be apparent that many modifications and alterations are possible in light of the foregoing teachings. Exemplary embodiments were chosen and described to explain certain principles of the invention and their practical application, so that others skilled in the art can make or utilize various exemplary embodiments of the invention, and their various alternatives and modifications. The purpose is that the scope of the invention will be defined by the appended claims and their equivalents.

[0066] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. An electrical spark pulse power supply, characterized in that, The electrical discharge pulse power supply includes a high-voltage breakdown circuit for gap breakdown machining in electrical discharge processing, a constant current source circuit for controlling the peak current of the pulse discharge, and a current waveform control circuit for controlling the rate of change of the leading and trailing edges of the output current waveform. The high-voltage breakdown circuit includes a second DC power supply V2, a first resistor R1, a second power switch Q2, a third diode D3, and a discharge gap; the second power switch Q2 is connected to a processing timing controller. The constant current source circuit includes a constant current source charging circuit and a constant current source freewheeling circuit; The constant current source charging circuit includes a DC first power supply V1, a first power switch Q1, a current sensor, a first inductor L1, and a first diode D1. The first power switch Q1 of the constant current source charging circuit is connected to a current closed-loop controller, and the current sensor is connected in series between the first power switch Q1 and the first inductor L1 of the constant current source charging circuit. When the first power switch Q1 is disconnected, the second power switch Q2 is disconnected, and the discharge gap is not broken down, the first inductor L1, the first diode D1, the second DC power supply V2, and the second diode D2 constitute a constant current source freewheeling circuit. When the first power switch Q1 is open and the second power switch Q2 is closed and the discharge gap is broken down, the first inductor L1, the second power switch Q2, the parallel second resistor R2 and inductor L, the third diode D3, the discharge gap and the second diode D2 constitute a constant current source freewheeling circuit. The current waveform control circuit consists of at least two switches, at least two inductors, a second resistor R2, a third diode D3, a discharge gap, and a fourth diode D4. The at least two switches and at least two inductors are connected in parallel with the second resistor R2; Before the gap is broken down, the constant current source circuit is continuously charged. When the gap is broken down, the high voltage breakdown circuit and the constant current source circuit form a discharge current circuit. The current change rate of the output current waveform at the leading and trailing edges is controlled by the current waveform control circuit.

2. The electrical discharge pulse power supply according to claim 1, characterized in that, The constant current source circuit includes a low-voltage constant current source circuit, which is a low-voltage current output circuit.

3. The electrical discharge pulse power supply according to claim 1, characterized in that, The current waveform control circuit consists of a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, a second inductor L2, a third inductor L3, a fourth inductor L4, a fifth inductor L5, a second resistor R2, a third diode D3, a discharge gap, and a fourth diode D4.

4. The electrical discharge pulse power supply according to claim 1, characterized in that, The discharge current circuit consists of a first DC power supply V1, a second DC power supply V2, a first power switch Q1, a first inductor L1, a second power switch Q2, a second resistor R2, a third diode D3, and a discharge gap.

5. The electrical discharge pulse power supply according to claim 3, characterized in that, The first power switch and the second power switch are either field-effect transistors or insulated-gate bipolar transistors.

6. The electrical discharge pulse power supply according to claim 5, characterized in that, The selection is achieved through the switch control, allowing for the combination of different inductance parameter circuits.

7. The electrical discharge pulse power supply according to claim 1, characterized in that, The current closed-loop controller uses PWM control.

8. A method for controlling the rate of change of current using an electric spark pulse power supply according to any one of claims 1 to 7, characterized in that, The method includes (1) The constant current source circuit continues to store energy before the discharge gap breaks down; (2) The high voltage breakdown circuit continues to rise and break down the discharge gap. The current closed-loop controller receives the detection signal of the discharge gap breakdown and sets the target current value. (3) The closed loop of the second power switch is turned on, and the inductor current is output to the current waveform control loop; (4) Select the processing mode by switching the first switch S1 on and off; (5) The processing timing controller controls the pulse width and pulse interval of the output current; (6) By controlling the combination of different inductance parameters through a switch, the current waveform control loop controls the current slope to rise or fall.

Images