Electrolytic arc complex / electrolytic integrated milling machining device and method

Abstract

The application relates to an electrolytic arc composite / electrolytic integrated milling device and method, and belongs to the electrolytic arc composite and combined milling field. The device is a composite machining system composed of two tool electrodes, two groups of power supplies and two diodes. The system uses high-conductivity electrolyte as a working medium, and the two electrodes are respectively connected to the negative poles of the two groups of power supplies. During machining, the tube electrode located in front of the feeding direction is firstly cut in to perform electrolytic arc composite milling machining to remove a large amount of workpiece materials; and the rectangular electrode located in the rear of the feeding direction is synchronously fed to perform electrolytic machining to remove the recast layer generated by the electrolytic arc composite milling machining and to flatten the surface. The device aims to improve the participation of electrolysis in the electrolytic arc composite milling machining by using additional electrolytic power supplies and electrodes, thereby improving the machining efficiency and the surface quality of the workpiece.

Description

TECHNICAL FIELD

[0001] The application relates to an electrolytic arc composite / electrolytic integrated milling machining device and a machining method, and belongs to the field of electrolytic arc composite and combined milling machining. BACKGROUND

[0002] At present, integration and light weight are the main development directions of structural parts in the field of aerospace, and therefore titanium alloy, as a metal material with high specific strength, high thermal strength and high corrosion resistance, is widely used in the manufacture of aerospace vehicles. However, due to the high strength and poor thermal conductivity of titanium alloy, machining by using a traditional mechanical machining method will generate a large cutting force, which will further cause serious tool wear and workpiece stress deformation, greatly affecting the manufacturing cycle and cost of the product.

[0003] Electrolytic milling machining removes workpiece material in a numerical control milling manner by using a simple rod-shaped cathode, and has the advantages of numerical control milling high flexibility and electrolytic machining no cutting force and tool loss, and is suitable for machining difficult-to-machine materials such as titanium alloy. However, due to the fact that electrolytic machining is prone to discharge under high current density, the improvement of the electrolytic milling machining speed has a certain upper limit, and large amount of titanium alloy material cannot be removed quickly.

[0004] Arc milling machining removes workpiece material by using the heat generated by the discharge of the anode and the cathode. Compared with electrolytic machining, arc machining has higher machining efficiency, but at the same time, it will produce a recast layer and residual stress on the workpiece surface, which will reduce the reliability and service life of the workpiece.

[0005] In order to combine the advantages and disadvantages of electrolytic and arc milling machining, an electrolytic arc composite milling machining method is proposed, which further improves the feed speed of electrolytic milling machining to the stable discharge stage, so that electrolytic machining and arc machining exist synchronously. While using arc machining to improve machining efficiency, electrolytic machining is used to remove the recast layer and residual stress on the workpiece surface. However, electrolytic arc composite machining shows a kind of "duality" in the aspect of feed speed, that is, when the feed speed is too fast, this method is closer to arc machining, the machining efficiency is high but the recast layer is thicker so that it cannot be completely removed by electrolytic machining; while the feed speed is too slow, this method is closer to electrolytic machining, there is no recast layer but the machining efficiency is low. In other words, pure electrolytic arc composite milling machining can achieve ideal machining effect, but its process window is very narrow, and it cannot further improve the machining efficiency. Therefore, how to further increase the participation of electrolytic action in electrolytic arc composite milling machining and then broaden the machining process window to achieve higher material removal rate and no recast layer machining effect is crucial for the development of electrolytic arc composite milling machining process. SUMMARY

[0006] The electrolytic arc composite / electrolytic integrated milling machining device and method of the present application further improve the feeding speed of the tool electrode and the electrolytic machining participation, realize higher material removal rate and the machining effect without recast layer.

[0007] The electrolytic arc composite / electrolytic integrated milling machining device of the present application comprises a rectangular electrode, a tube electrode, a first power supply, a second power supply, a first diode and a second diode. The center axes of the tube electrode and the rectangular electrode are arranged in front and back along the feeding direction, and the two are synchronously moved, the relative position is kept unchanged, the tube electrode performs the electrolytic arc composite milling machining in front, removes most of the material, and the rectangular electrode removes the recast layer on the surface after the machining in back. The first power supply and the second power supply are two groups of DC stabilized power supplies with the same type, the rectangular electrode and the tube electrode are connected to the negative poles of the first power supply and the second power supply respectively, the workpiece is connected to the positive poles of the first power supply and the second power supply through the first diode and the second diode respectively, and the unidirectional conductivity of the diode is used to prevent the backflow of the power supply current. High-conductivity electrolyte is used as the working medium for the electrolytic arc composite milling machining and the electrolytic milling machining, and the electrolyte is sprayed into the machining area through the tube electrode.

[0008] The machining method using the electrolytic arc composite / electrolytic integrated milling machining device comprises the following steps.

[0009] (1) The tube electrode and the rectangular electrode are installed, the cutting depth is set after the synchronous tool setting, the electrolyte is supplied into the tube electrode, and the same working voltage is set for the first power supply and the second power supply.

[0010] (2) The tube electrode cuts into the workpiece in front along the feeding direction to perform the electrolytic arc composite milling machining and remove the workpiece material in large excess, and the rectangular electrode is synchronously fed in back to perform the electrolytic milling machining using the electrolyte sprayed by the tube electrode to remove the recast layer remaining on the surface of the groove.

[0011] The length of the rectangular electrode and the tube electrode is the same, and the bottom surfaces of the electrodes are located on the same horizontal plane and have the same projection area along the feeding direction.

[0012] The tube electrode is a rotating inner liquid spraying electrode, the liquid outlet holes and the liquid outlet grooves are uniformly distributed along the bottom and the side wall respectively, and the material of the tube electrode is copper-tungsten alloy resistant to electric corrosion.

[0013] The high-conductivity electrolyte is a sodium chloride solution with a mass fraction of 20%.

[0014] The present application has the following advantages.

[0015] 1.Using high conductivity electrolyte as the common working medium of the electrochemical arc hybrid machining and the electrochemical machining, on one hand, it can play the electrolysis function to the greatest extent and increase the participation of electrolysis, on the other hand, it can use lower working voltage, and then reduce the single discharge energy of the arc, and reduce the thickness of the recast layer and the loss of the tool cathode.

[0016] 2.Using the electrolysis power supply and electrode arranged additionally, it improves the electrolysis current and the total rated current of the power supply, reduces the influence of the discharge plasma on the electrolysis current, and further improves the participation of electrolysis, so as to realize higher feed speed.

[0017] 3.Only once clamping of the two electrodes can realize high efficiency and recast layer-free machining, and without adding rotating shaft or liquid spraying device, only simple fixing and power supply of the rectangular electrode behind the feed direction can realize machining. When repeating machining, only the front tube electrode needs to be replaced, and the rear rectangular electrode does not need to be clamped and aligned, which simplifies the operation and reduces the preparation time. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the schematic diagram of the electrochemical arc hybrid / electrochemical integrated milling machining device;

[0019] Figure 2 is the schematic diagram of the tube electrode structure;

[0020] Figure 3 is the schematic diagram of the material removal and flow field direction in the machining gap;

[0021] Wherein the label name: 1. Workpiece, 2. First diode, 3. First power supply, 4. Rectangular electrode, 5. Liquid inlet direction, 6. Tube electrode rotation direction, 7. Second power supply, 8. Feed direction, 9. Second diode, 10. Recast layer, 11. Tube electrode, 12. Machining groove side wall and bottom flow field direction, 13. Arc discharge. EMBODIMENT

[0022] The present application is further described below in combination with the drawings.

[0023] Figure 1The diagram shows an electrolytic arc combined / electrolytic integrated milling apparatus. This apparatus includes: a first diode 2, a first power supply 3, a rectangular electrode 4, a second power supply 7, a second diode 9, and a tube electrode 11. The tube electrode 11 and the rectangular electrode 4 are respectively connected to the negative terminals of the second power supply 7 and the first power supply 3. The workpiece serves as the common anode, and the second diode 9 and the first diode 2 prevent backflow between the two power supplies. The second power supply 7 and the first power supply 3 are two sets of identical DC regulated power supplies, and both sets are set to the same operating voltage during machining. The tube electrode 11 and the rectangular electrode 4 are arranged front and rear along the feed direction 8, maintaining synchronous movement during machining. The two electrodes have the same length, and their bottom surfaces are also located on the same horizontal plane, having the same projected area along the feed direction. During machining, the tube electrode 11 in front of the feed direction 8 cuts into the workpiece 1 with a certain depth of cut, performing electrolytic arc combined milling to remove a large amount of workpiece material; the rectangular electrode 4 behind the feed direction feeds synchronously, using electrolysis to remove the recast layer 10 generated during the electrolytic arc machining process, improving surface quality.

[0024] Figure 2 The diagram shows the structure of the tube electrode 11. To promptly remove the products generated during the electrolytic arc composite machining process and achieve a good arc-breaking effect, the tube electrode 11 rotates and adopts an internal liquid spraying outlet structure. It is fixed to the end of the spindle of the electrolytic milling machine tool by a universal water-stop chuck. Six circumferentially distributed liquid outlet grooves and three liquid outlet holes are opened on its sidewalls and bottom. To reduce electrode wear, the tube electrode is made of a copper-tungsten alloy material resistant to electrical corrosion.

[0025] Figure 3 This is a schematic diagram of material removal and flow field direction within the machining gap. A 20% sodium chloride solution is injected from the machine tool spindle along the inlet direction 5 into the interior of the tube electrode, and then... Figure 2 The electrode sidewall outlet groove and bottom outlet hole shown spray the electrolyte into the machining gap. During machining, the tube electrode 11 is continuously fed forward. When the inter-electrode gap in front of the tube electrode 11 reaches a critical value, an arc discharge 13 is generated, so that arc machining and electrolytic machining coexist in the machining area of ​​the tube electrode 11. To improve machining efficiency, a faster machining speed is adopted. At this time, the removal of material is dominated by electrical discharge machining, the frequency of arc discharge 13 is higher, and the resulting recast layer 10 cannot be removed by the electrolytic action of the tube electrode 11 alone. Therefore, some recast layer 10 remains in the area swept by the tube electrode 11. The rectangular electrode 4 uses the electrolyte sprayed by the tube electrode 11 along the sidewall and bottom surface direction 12 of the machining groove for electrolytic milling to remove the residual recast layer 10 and make up for the lack of electrolytic action of the tube electrode 11.

Claims

1. A combined electrolytic arc / electrolytic integrated milling machining device, characterized in that: The system includes a rectangular electrode (4), a tube electrode (11), a first power supply (3), a second power supply (7), a first diode (2), and a second diode (9). The central axes of the tube electrode (11) and the rectangular electrode (4) are arranged in front and behind along the feed direction (8). They move synchronously and their relative positions remain unchanged. The tube electrode (11) performs electrolytic arc composite milling in front to remove most of the material, while the rectangular electrode (4) trims the surface after processing in the rear to remove the recast layer. The first power supply (3) and the second power supply (7) are two sets of DC regulated power supplies of the same model. The rectangular electrode (4) and the tube electrode (11) are respectively connected to the negative terminals of the first power supply (3) and the second power supply (7). The workpiece is used as a common anode and is connected to the positive terminals of the first power supply (3) and the second power supply (7) through the first diode (2) and the second diode (9), respectively. The unidirectional conductivity of the diode is used to prevent the reverse flow of the power supply current. A high-conductivity electrolyte is used as the common working medium for electrolytic arc composite milling and electrolytic milling. The electrolyte is sprayed into the processing area through the tube electrode (11).

2. The electrolytic arc composite / electrolytic integrated milling apparatus according to claim 1, characterized in that: The rectangular electrode (4) and the tube electrode (11) mentioned above have the same length, and their bottom surfaces are also located on the same horizontal plane, with the same projected area along the feed direction.

3. The electrolytic arc composite / electrolytic integrated milling processing device according to claim 1, characterized in that: The tube electrode (11) is a rotating internal spray electrode, with the liquid outlet hole and liquid outlet groove evenly distributed along its bottom and sidewall circumferentially, respectively, and its material is a copper-tungsten alloy resistant to electrical corrosion.

4. The electrolytic arc composite / electrolytic integrated milling apparatus according to claim 1, characterized in that: The high conductivity electrolyte is a sodium chloride solution with a mass fraction of 20%.

5. The machining method using the electrolytic arc composite / electrolytic integrated milling apparatus according to claim 1, characterized in that... Includes the following steps: (1) Install the tube electrode (11) and the rectangular electrode (4), set a certain cutting depth after synchronous tool setting, and pass electrolyte into the tube electrode (11). Set the first power supply (3) and the second power supply (7) to the same working voltage. (2) While the first power supply (3) and the second power supply (7) are running, the tube electrode (11) cuts into the workpiece (1) in front of the feed direction (8) to perform electrolytic arc composite milling and remove a large amount of workpiece material. The rectangular electrode (4) is fed synchronously from behind, and the electrolyte sprayed by the tube electrode (11) is used for electrolytic milling to remove the residual recast layer (10) on the surface of the tank.

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