Pulse discharge method

Abstract

The invention discloses a pulsating discharge method, which comprises the following steps that: in electrical discharge machining, a pulse with a higher frequency is additionally superposed on each pulse output during machining, and the discharge current is in a pulsating state within a pulse width. According to the method, in the electric spark machining process, a changing magnetic field is generated through pulsating changing current, the changing magnetic field generates periodically changing acting force on electrons in a discharge channel, the electrons in plasma in the discharge channel sweep a workpiece back and forth, the acting area is large, energy is dispersed, an electric corrosion pit is large and shallow, and the electric spark machining efficiency is improved while high efficiency is kept. Compared with the prior art, better surface roughness and a shallower heat affected layer are obtained, efficiency and quality can be achieved at the same time, the method has the advantages of being simple, reliable and stable, and the actual machining effect cannot be affected.

Description

Technical Field

[0001] The invention relates to the technical field of electric spark machining, and in particular to a pulsating discharge method. Background Art

[0002] Electrospark machining is a processing method that generates high temperature to melt and vaporize the material by discharging electricity between the workpiece and the tool electrode. It has the advantages of being unaffected by the hardness of the workpiece material and having low processing force. It is widely used in aerospace, weapons and civilian fields.

[0003] The characteristics of EDM determine that its processing efficiency and processing quality cannot be achieved at the same time. The larger the discharge energy, the higher the processing efficiency, but the larger the pits produced by the discharge explosion, the poorer the surface roughness, and the more likely it is to produce microcracks; when the discharge energy is low, although the surface quality is good, the processing efficiency is low. In order to take into account both the efficiency and quality of EDM, the prior art uses mixed powder EDM technology to disperse a single discharge point into multiple points for synchronous discharge, with the total energy and total removal unchanged, and the large pits originally eroded by single-point discharge are transformed into multiple small pits by multi-point discharge, thereby improving the surface quality and reducing the heat-affected layer. However, in mixed powder EDM, due to the large difference in density between powder and liquid, it is very easy to precipitate and agglomerate, which affects the actual processing effect. Therefore, there is an urgent need for a pulsating discharge method that can achieve both efficiency and quality, is simple and reliable, and does not affect the actual processing effect. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned problems and provide a pulsating discharge method, which can achieve both efficiency and quality in electrospark machining, has the advantages of being simple, reliable and stable, and will not affect the actual machining effect.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A pulsating discharge method comprises the following steps:

[0007] In EDM, a higher frequency pulse is superimposed on each pulse output during machining, and the discharge current is pulsating within a pulse width.

[0008] In a preferred embodiment of the present invention, the pulsating variation of the discharge current is achieved by adjusting the periodic variation of the current limiting resistor in the pulsating discharge circuit.

[0009] Preferably, the specific steps of achieving the pulsating change of the discharge current by adjusting the periodic change of the current limiting resistor in the pulsating discharge circuit are:

[0010] The pulsating change of the discharge current is achieved by connecting a resistance branch with controllable periodic switching in parallel next to the current limiting resistor in the pulsating discharge loop.

[0011] Preferably, the pulsating discharge circuit includes a power supply, a circuit switch tube, a current-limiting resistor, an electrospark machining part, and a switchable resistance branch; wherein the power supply, circuit switch tube, current-limiting resistor, and electrospark machining part are connected in series; the resistance branch is connected in parallel with the current-limiting resistor; the resistance branch includes a branch switch tube and an adjustable resistor connected in series. In the above-mentioned pulsating discharge circuit, a switchable resistance branch is connected in parallel next to the current-limiting resistor in the pulsating discharge circuit, and the pulsating change of the discharge current is realized by adjusting the periodic switching of the adjustable resistor in the resistance branch.

[0012] Preferably, the specific steps of achieving the pulsating change of the discharge current by adjusting the periodic change of the current limiting resistor in the pulsating discharge circuit are:

[0013] The pulsating change of the discharge current is achieved by periodically switching two current limiting resistors with different resistance values ​​in the pulsating discharge loop.

[0014] Preferably, the pulsating discharge circuit includes a power supply, a resistance pulsating circuit and an electrospark machining part; the power supply, the pulsating circuit and the electrospark machining part are connected in series; the pulsating circuit includes a first resistance branch and a second resistance branch connected in parallel; the first resistance branch includes a first branch switch tube and a first current limiting resistor connected in series; the second resistance branch includes a second branch switch tube and a second current limiting resistor connected in series; the two current limiting resistors are the first current limiting resistor and the second current limiting resistor, respectively, and the resistance values ​​of the first current limiting resistor and the second current limiting resistor are different. In the above-mentioned pulsating discharge circuit, by connecting the first current limiting resistor and the second current limiting resistor with different resistance values ​​in parallel, the on and off of the first current limiting resistor and the second current limiting resistor are periodically switched back and forth to achieve the pulsating change of the discharge current.

[0015] Preferably, the pulsating variation of the discharge current is achieved by using a high voltage power supply and a low voltage power supply in a pulsating discharge circuit to be switched on and off periodically in turn.

[0016] Preferably, the pulsating discharge circuit includes a power pulsating circuit, a current limiting resistor and an electrospark machining part, the power pulsating circuit, the current limiting resistor and the electrospark machining part are connected in series, the power pulsating circuit includes a first power branch and a second power branch connected in parallel; the first power branch includes a first branch switch tube, a low voltage power supply and a first diode connected in series; the second power branch includes a second branch switch tube, a high voltage power supply and a second diode connected in series. In the above pulsating discharge circuit, the high voltage power supply and the low voltage power supply are connected in parallel, and the high voltage power supply and the low voltage power supply are switched on and off periodically to achieve the pulsating change of the discharge current.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The pulsating discharge method of the present invention superimposes a higher frequency pulse on the normal EDM pulse (original pulse), that is, in one pulse width, the discharge current changes in a pulsating manner, rather than the original constant value. The changing current generates a changing magnetic field, and the changing magnetic field generates a changing force on the electrons in the discharge channel, so that the electron beam in the plasma in the discharge channel in the machining gap sweeps back and forth on the workpiece surface, the action area is increased, and the pits generated by the explosion are large and shallow, so that while maintaining the original machining efficiency, the surface roughness is improved and the heat-affected zone is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structural principle and a discharge current variation diagram of the first specific implementation mode of the pulsating discharge circuit in the present invention.

[0020] Figure 2 It is a schematic diagram of the structural principle and a discharge current variation diagram of the second specific implementation mode of the pulsating discharge circuit in the present invention.

[0021] Figure 3 A schematic diagram of the structural principle and a diagram of the discharge current variation of the third specific implementation manner of the pulsating discharge circuit in the present invention. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0023] Example 1

[0024] This embodiment provides a pulsating discharge method, comprising the following steps:

[0025] In EDM, a higher frequency pulse is superimposed on each pulse output during machining, and the discharge current is pulsating within a pulse width.

[0026] The pulsating discharge method in this embodiment superimposes a higher frequency pulse on the normal EDM pulse (original pulse), that is, in one pulse width, it changes in a pulsating manner instead of the original constant value, so that it changes in a pulsating manner during each pulse width. The pulsating current produces a changing magnetic field, and the changing magnetic field produces a periodically changing force on the electrons in the discharge channel. The electrons in the plasma in the discharge channel sweep the workpiece 1 back and forth, with a large effective area, dispersed energy, and large and shallow electro-etching pits. While maintaining high efficiency, better surface roughness and a shallower heat-affected layer are obtained, which can achieve both efficiency and quality, and has the advantages of simplicity, reliability, and stability, and will not affect the actual processing effect.

[0027] See also Figure 1 The pulsating discharge method is implemented by a pulsating discharge circuit. Specifically, the pulsating change of the discharge current is achieved by adjusting the periodic change of the current limiting resistor in the pulsating discharge circuit.

[0028] See also Figure 1 The specific steps of achieving the pulsating change of the discharge current by adjusting the periodic change of the current limiting resistor in the pulsating discharge circuit are: a resistance branch with controllable periodic on and off is connected in parallel next to the current limiting resistor 3 in the pulsating discharge circuit to achieve the pulsating change of the discharge current.

[0029] See also Figure 1 The pulsating discharge circuit includes a power supply 10, a circuit switch tube 7, a current limiting resistor 3, an electrospark machining part, and a switchable resistance branch; wherein the power supply 10, the circuit switch tube 7, the current limiting resistor 3, and the electrospark machining part are connected in series; the resistance branch is connected in parallel with the current limiting resistor 3; the resistance branch includes a branch switch tube 5 and an adjustable resistor 4 connected in series. In the above pulsating discharge circuit, a switchable resistance branch is connected in parallel next to the current limiting resistor 3 in the pulsating discharge circuit, and the pulsating change of the discharge current is realized by adjusting the periodic switch of the adjustable resistor 4 in the resistance branch.

[0030] See also Figure 1 The electrospark machining part includes a workpiece 1 and an electrode 2, and a discharge gap is provided between the workpiece 1 and the electrode 2; the positive pole of the power supply 10 is connected to the workpiece 1, and the current limiting resistor 3 and the adjustable resistor 4 are both connected to the electrode 2; one end of the loop switch tube 7 is connected to the negative pole of the power supply 10, and the other end is respectively connected to the branch switch tube 5 and the current limiting resistor 3.

[0031] See also Figure 1 The loop switch tube 7 is turned on and off at a frequency of f1. During the on-time of the loop switch tube 7, the voltage source provides a basic discharge current I1 through the current limiting resistor 3. The branch switch tube 5 is turned on and off at a frequency f2 higher than f1, and a pulsating current I2 with a pulse frequency of f2 is generated on the resistance branch; I1 and I2 are superimposed to form a pulsating discharge current I0.

[0032] See also Figure 1 , R c1 Represented as current limiting resistor 3, R c2 It is represented by an adjustable resistor 4, Q2 is represented by a branch switch tube 5, Q1 is represented by a loop switch tube 7, and U is represented by a power supply 10.

[0033] Example 2

[0034] See also Figure 2The pulsating discharge circuit in this embodiment is different from the pulsating discharge circuit in Example 1, and the adjustment method is also different. The specific steps of realizing the pulsating change of the discharge current by adjusting the periodic change of the current limiting resistor in the pulsating discharge circuit are: realizing the pulsating change of the discharge current by periodically switching two current limiting resistors with different resistance values ​​in the pulsating discharge circuit.

[0035] See also Figure 2 The pulsating discharge circuit includes a power supply 10, a resistance pulsating circuit and an electrospark machining part; the power supply 10, the pulsating circuit and the electrospark machining part are connected in series; the pulsating circuit includes a first resistance branch and a second resistance branch connected in parallel; the first resistance branch includes a first branch switch tube 6 and a first current limiting resistor 3 connected in series; the second resistance branch includes a second branch switch tube 5 and a second current limiting resistor 4 connected in series; the two current limiting resistors are the first current limiting resistor 3 and the second current limiting resistor 4, respectively, and the resistance values ​​of the first current limiting resistor 3 and the second current limiting resistor 4 are different. In the above pulsating discharge circuit, by connecting the first current limiting resistor 3 and the second current limiting resistor 4 with different resistance values ​​in parallel, the first current limiting resistor 3 and the second current limiting resistor 4 are periodically switched back and forth to achieve the pulsating change of the discharge current.

[0036] See also Figure 2 The EDM machining part includes a workpiece 1 and an electrode 2, and a discharge gap is provided between the workpiece 1 and the electrode 2; the positive electrode of the power supply 10 is connected to the workpiece 1, and the electrode 2 is respectively connected to the first current limiting resistor 3 and the second current limiting resistor 4; the negative electrode of the power supply 10 is respectively connected to the first branch switch tube 6 and the second branch switch tube 5. By alternately turning on the first branch switch tube 6 and the second branch switch tube 5, during the conduction period of the first branch switch tube 6, the discharge current provided by the first resistance branch is I1, and during the conduction period of the second branch switch tube 5, the discharge current provided by the second resistance branch is I2. In one pulse width, I1 and I2 are continuously switched to form a pulsating discharge current I0.

[0037] See also Figure 2 , R c1 Represented as the first current limiting resistor 3, R c2 It represents the second current limiting resistor 4 , Q2 represents the second branch switch tube 5 , Q1 represents the first branch switch tube 6 , and U represents the power supply 10 .

[0038] Example 3

[0039] See also Figure 3 The pulsating discharge circuit in this embodiment is different from the pulsating discharge circuit in Example 1. The pulsating discharge circuit in this embodiment realizes the pulsating change of the discharge current by using the high-voltage power supply 11 and the low-voltage power supply 10 in the pulsating discharge circuit to periodically turn on and off in turn.

[0040] See also Figure 3 The pulsating discharge circuit includes a power supply pulsating circuit, a current limiting resistor 3 and an electrospark machining part. The power supply pulsating circuit, the current limiting resistor 3 and the electrospark machining part are connected in series. The power supply pulsating circuit includes a first power supply branch and a second power supply branch connected in parallel; the first power supply branch includes a first branch switch tube 12, a low-voltage power supply 10 and a first diode 8 connected in series; the second power supply branch includes a second branch switch tube 13, a high-voltage power supply 11 and a second diode 9 connected in series. In the above pulsating discharge circuit, by connecting the high-voltage power supply 11 and the low-voltage power supply 10 in parallel, the high-voltage power supply 11 and the low-voltage power supply 10 are periodically switched back and forth to achieve the pulsating change of the discharge current.

[0041] See also Figure 3 The electrospark machining part includes a workpiece 1 and an electrode 2, and a discharge gap is provided between the workpiece 1 and the electrode 2; the positive electrode of the low-voltage power supply 10 is connected to the first diode 8, and the negative electrode is connected to the first branch switch tube 12; the positive electrode of the high-voltage power supply 11 is connected to the second diode 9, and the negative electrode is connected to the second branch switch tube 13; the workpiece 1 is connected to the first diode 8 and the second diode 9 respectively; one end of the current limiting resistor 3 is connected to the first branch switch tube 12 and the second branch switch tube 13 respectively, and the other end of the current limiting resistor 3 is connected to the electrode 2.

[0042] See also Figure 3 In this embodiment, the pulsating discharge is realized by adjusting the voltage. The low-voltage power supply 10 is a low-voltage DC source, and the high-voltage power supply 11 is a high-voltage DC power supply 10. The low-voltage power supply 10 is connected in series with a first diode 8, and the high-voltage power supply 11 is connected in series with a second diode 9 to prevent the high-voltage power supply 11 from charging the low-voltage power supply 10. The first branch switch tube 12 is turned on and off at a frequency of f1; the low-voltage power supply 10 provides a relatively small basic discharge current I1 with a frequency of f1; the second branch switch tube 13 is turned on and off at a frequency of f2 higher than f1; the high-voltage power supply 11 generates a relatively high pulsating current I2 with a frequency of f2. I1 and I2 are superimposed to form a pulsating discharge current I0.

[0043] See also Figure 3 Since the discharge current I0 is in a pulsating state, a changing magnetic field is generated. The changing magnetic field exerts a periodically changing force on the electrons moving in the discharge channel. The plasma sweeps back and forth on the surface of the workpiece 1, expanding the electro-erosion action area. Under the condition that the processing efficiency remains basically unchanged, the electro-erosion pit becomes shallower and the heat-affected layer becomes thinner, thereby conveniently and reliably achieving efficient and high-quality processing effects.

[0044] See also Figure 3 , R cIt is represented by a current limiting resistor 3, Q2 is represented by a second branch switch tube 13, Q1 is represented by a first branch switch tube 12, U1 is represented by a low-voltage power supply 10, U2 is represented by a high-voltage power supply 11, D2 is represented by a second diode 9, and D1 is represented by a first diode 8.

[0045] The above is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited to the above content. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A pulsating discharge method, characterized in that: The following steps are involved: In EDM, a higher frequency pulse is superimposed on each pulse output during machining, and the discharge current is pulsating within a pulse width.

2. A pulsating discharge method according to claim 1, characterized in that: The pulsating change of the discharge current is achieved by adjusting the periodic change of the current limiting resistor in the pulsating discharge loop.

3. A pulsating discharge method according to claim 2, characterized in that: The specific steps to achieve the pulsating change of the discharge current by adjusting the periodic change of the current limiting resistor in the pulsating discharge circuit are: The pulsating change of the discharge current is achieved by connecting a resistance branch with controllable periodic switching in parallel next to the current limiting resistor in the pulsating discharge loop.

4. A pulsating discharge method according to claim 3, characterized in that: The pulsating discharge circuit includes a power supply, a circuit switch tube, a current limiting resistor, an electrospark machining part and a switchable resistance branch; wherein the power supply, the circuit switch tube, the current limiting resistor and the electrospark machining part are connected in series; the resistance branch is connected in parallel with the current limiting resistor; the resistance branch includes a branch switch tube and an adjustable resistor connected in series.

5. A pulsating discharge method according to claim 2, characterized in that: The specific steps to achieve the pulsating change of the discharge current by adjusting the periodic change of the current limiting resistor in the pulsating discharge circuit are: The pulsating change of the discharge current is achieved by periodically switching two current limiting resistors with different resistance values ​​in the pulsating discharge loop.

6. A pulsating discharge method according to claim 5, characterized in that: The pulsating discharge circuit includes a power supply, a resistance pulsating circuit and an electrospark machining part; the power supply, the pulsating circuit and the electrospark machining part are connected in series; the pulsating circuit includes a first resistance branch and a second resistance branch connected in parallel; the first resistance branch includes a first branch switch tube and a first current limiting resistor connected in series; the second resistance branch includes a second branch switch tube and a second current limiting resistor connected in series; the two current limiting resistors are respectively the first current limiting resistor and the second current limiting resistor, and the resistance values ​​of the first current limiting resistor and the second current limiting resistor are different.

7. A pulsating discharge method according to claim 1, characterized in that: The pulsating change of the discharge current is achieved by using the high-voltage power supply and the low-voltage power supply in the pulsating discharge circuit to be switched on and off periodically in turn.

8. A pulsating discharge method according to claim 7, characterized in that: The pulsating discharge circuit includes a power pulsating circuit, a current limiting resistor and an electrospark machining part, which are connected in series. The power pulsating circuit includes a first power branch and a second power branch connected in parallel; the first power branch includes a first branch switch tube, a low-voltage power supply and a first diode connected in series; the second power branch includes a second branch switch tube, a high-voltage power supply and a second diode connected in series.

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