CN111673210B

CN111673210B - High-speed electric arc machining device and method adopting resorption type electrode

Info

Publication number: CN111673210B
Application number: CN202010459997.2A
Authority: CN
Inventors: 何国健; 顾琳; 廖阳稷敛
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2021-11-30
Anticipated expiration: 2040-05-27
Also published as: CN111673210A

Abstract

The invention discloses a high-speed electric arc machining device and a machining method adopting a resorption type electrode. The medium liquid circulates among the suction pump, the liquid storage tank, the flushing pump, the rotating spindle and the tool electrode in sequence. The liquid outlet channel and the liquid return channel are integrally arranged on the tool electrode to complete the supply and recovery of the medium liquid during processing, the negative pressure effect of the suction pump can be fully utilized, and a negative pressure environment is formed in a narrow processing gap filled with the medium liquid. The negative pressure environment enables the fluid arc breaking effect of the processing area to be more stable, pressure loss of medium liquid flowing from the liquid outlet channel to the open environment is avoided, the arc breaking effect is more obvious, and the surface quality of the processing area can be effectively improved.

Description

High-speed electric arc machining device and method adopting resorption type electrode

Technical Field

The invention relates to the field of electric discharge machining, in particular to a high-speed electric arc machining device and method adopting a resorption type electrode.

Background

Arc discharge machining is a generic term for a machining method of forming an effective and controllable arc discharge between a tool electrode and a workpiece and etching away the material of the workpiece by the heat of the formed plasma. The arc discharge processing is a nearly steady-state self-sustaining discharge plasma generated under the conditions of large current and long pulse, the arc column of the arc discharge processing has very high energy density, and the temperatures of corresponding electrons and ions are also very high. However, if the discharge arc column stays on the surface of the workpiece, the workpiece and the electrode are burnt, so that the arc column can be effectively moved quickly on the surface of the workpiece and even cut off by utilizing mechanical motion and fluid power to realize arc breaking or simultaneously integrating the arc breaking and the arc breaking, and the arc is prevented from staying at a certain point. Similarly, the workpiece material is rapidly melted or even gasified under the action of the arc plasma with high energy density, and the re-solidified etching particles are easily accumulated on the surface of the workpiece, so that the discharge gap between the tool electrode and the workpiece material is reduced to cause secondary discharge or even short circuit. Effective chip removal by means of high-speed fluid is also advantageous for avoiding surface burns and for ensuring continuity of processing.

Therefore, high-speed arc discharge milling and plunge machining are achieved based on mechanical movement and a hydrodynamic arc breaking mechanism and in combination with a negative pressure environment of a machining area. The device enhances the arc breaking efficiency and the cooling effect of the high-speed arc discharge process through a negative pressure environment, reduces the surface roughness under different processing modes, reduces the thickness of a heat affected zone and improves the quality of a processed surface.

For example, patent document CN201410137565.4, a nondestructive electrode for electric discharge machining, discloses an electric discharge process between a conductive liquid covering a tool electrode and a workpiece, in which an outer layer conductive liquid of a conductive liquid absorber is continuously supplied with an electro-hydraulic fluid by using a negative pressure environment, so as to achieve the effect of nondestructive discharge of the electrode. Although the nondestructive electrode device can discharge by using the conductive liquid instead of a tool electrode, the compensation of electrode loss is not needed, theoretically, the discharge gap between the conductive liquid and a workpiece material is relatively unchanged, but the etched material particles are fine, so that the conductive liquid absorber is possibly blocked, and the relatively stable discharge state between the conductive liquid and the workpiece material is influenced.

For example, patent document CN201610018258.3 entitled "consumable electrode annular negative pressure arc welding method" discloses a device for controlling the degree of arc confinement by adjusting the negative pressure region inside a hollow tubular electrode, and further changing the arc characteristics such as the arc energy density, the arc voltage, and the arc pressure. The device can realize the control of welding heat input and welding seam forming, but cannot realize complex multi-axis servo motion in high-speed arc discharge machining due to the complexity and fixed position of the device. And is used in the field of arc welding, emphasizing the stability of the arc. In high-speed arc discharge machining, arc interruption is assisted by a negative pressure environment.

Another method for arc machining is to perform arc machining on a designated area in a closed chamber. The liquid medium with the pressure intensity of 0.4-0.7Mpa flows in from the side opening of the chamber and flows out from the internal flow passage of the electrode, the external flushing liquid cooling and arc breaking are carried out on the electric arc machining discharge area, and the rest parts are kept sealed. The method adopts a direct current power supply, the duration of the discharge plasma is directly related to the flow rate of the liquid, and the pulse discharge effect with different pulse widths is realized by adjusting the flow rate of the liquid medium. In the processing process, the sealing chamber is fixed around the processing area and is kept static, only the sinking processing of the processing area is realized, and the processing mode is single. In the method, the electrode is only fed in the machining direction, rotary motion does not exist, only a hydrodynamic arc breaking mechanism is relied on, effective cutting of the arc cannot be guaranteed, the machining process is unstable, the machined surface is easily burnt, the problem that the subsequent finish machining is influenced by the fact that the heat affected zone of the material is deep, the surface hardness difference is large and the like is caused. Among the processing parameters, the current is 100-500A, the voltage is 25-35V, the arc processing with small discharge energy is achieved, and the material removal rate is limited.

Disclosure of Invention

In order to overcome the disadvantages of the prior art, the present invention provides a high-speed arc machining apparatus and method using a back-suction electrode, which can solve the above-mentioned problems.

The purpose of the invention is realized by adopting the following technical scheme:

a high-speed electric arc processing device adopting a resorption type electrode comprises a rotating main shaft, a tool electrode, a main shaft shell, a suction pump, a liquid storage tank and a flushing pump, wherein the tool electrode is fixed on the rotating main shaft, the rotating main shaft is connected to a machine tool main shaft in an insulating way and rotates at a high speed along with the machine tool main shaft to realize mechanical motion arc breaking in the processing process; the medium liquid circulates among the suction pump, the liquid storage tank, the flushing pump, the rotating spindle and the tool electrode in sequence. The tool electrode adopts a porous resorption type structure and comprises an electrode body, a joint, an electrode liquid outlet channel and a plurality of electrode liquid return channels; the joint is arranged on the outer wall of the upper part of the electrode body and is used for being connected with the rotating main shaft; a through hole is formed in the axis of the electrode body to form the electrode liquid outlet channel, the upper end of the electrode liquid outlet channel is communicated with the medium flow channel of the rotating main shaft, and the electrode liquid outlet channel is used as an inner flushing liquid flow channel to spray medium liquid to a processing area on the surface of a workpiece; the electrode is characterized in that a plurality of electrode liquid return channels are annularly and uniformly distributed around the electrode liquid outlet channel in the axial direction of the electrode body, annular liquid return channels are formed in the positions, corresponding to the upper ends of the plurality of electrode liquid return channels, of the upper portion of the electrode body, liquid return holes are formed in the circumferential direction of the liquid return channels and are communicated with the suction pump through the liquid return holes, and the electrode liquid return channels are used as outer liquid suction channels for drawing back medium liquid in a machining area.

Preferably, the diameter of the electrode liquid return channel is smaller than the radius of the electrode liquid outlet channel.

Preferably, the flushing pump comprises a pump body and a control valve; the suction pump includes a pump body, a control valve, and a filter.

A processing method adopting the device comprises the following steps.

Preparing for electric arc machining, namely fixing a workpiece material on a workbench of a machine tool in an insulating manner, fixing a tool electrode on a rotating main shaft, and fixedly connecting the rotating main shaft with a main shaft of the machine tool and keeping the rotating main shaft insulated; connecting the workpiece material and the tool electrode to two electrodes of a discharge power supply respectively; then the electrode liquid return channel is communicated with a suction pump through a liquid return ring channel arranged on the rotating main shaft and a liquid return hole arranged on the main shaft shell; the discharge gap between the workpiece material and the tool electrode is set by the machine tool servo system.

High-speed electric arc machining, namely, medium liquid in a liquid storage tank reaches a high-pressure state through a flushing pump and flows through a rotating main shaft and an electrode liquid outlet channel of a tool electrode to provide high-pressure internal flushing liquid for a machining area; the high-pressure internal flushing liquid realizes hydrodynamic arc breaking and quickly flushes the eroded particles away from the processing area; under the negative pressure environment of the machining gap, medium liquid carrying with the corrosion removal particles flows through the electrode liquid return channel, the liquid return loop channel on the rotating main shaft and the liquid return hole on the main shaft shell, is filtered by the suction pump and is pumped back to the liquid storage tank of the machine tool, and a liquid supply circulation system is formed.

After the machining is finished and the discharging is stopped, the main shaft of the machine tool stops rotating, the tool electrode stays at the machining finishing position for a short time, and the liquid medium with the metal corrosion particles is fully pumped away by a suction pump; and then the machine tool is lifted to a safe position through servo motion of the machine tool, and the machine tool is stopped.

Preferably, the discharge power supply adopts a periodic pulse power supply, the voltage value is 30-120V, the peak current is 50-10000A, and the provided pulse width and pulse interval range is 2-20000 mus.

Compared with the prior art, the invention has the beneficial effects that: 1. the tool electrode adopts a porous resorption type structure, the electrode liquid outlet channel and the electrode liquid return channel are arranged tightly, a negative pressure environment is generated in an electric arc machining gap, and the electric arc plasma in the discharge gap can be effectively subjected to negative pressure arc breaking in time. 2. Because the negative pressure area is filled with medium flow and has narrow space, the pressure loss of the negative pressure is small, the instability and the discontinuity of a negative pressure arc breaking mechanism are avoided, and the quality of a processed surface is effectively improved. 3. The corrosion-removed particles of the workpiece material are quickly taken away by the medium liquid under the negative pressure environment, and abnormal discharge states such as short circuit, secondary discharge and the like are avoided. 4. The negative pressure arc breaking effect depends on a liquid supply circulating system consisting of a suction pump, a liquid storage tank, a liquid flushing pump, a rotating main shaft and a tool electrode, additional complex auxiliary equipment cannot be added at the end of the tool electrode, and the negative pressure arc breaking effect can adapt to various processing modes such as sinking type processing, hole processing, curved surface processing on an impeller blade and the like.

Drawings

FIG. 1 is a schematic view of a high speed electric arc machining apparatus using a back suction electrode according to the present invention;

FIG. 2 is an enlarged schematic view at B of FIG. 1;

fig. 3 is a schematic view of a tool electrode used in the embodiment of fig. 1.

In the figure: 1. rotating the main shaft; 11. a liquid return loop; 2. a tool electrode; 21. an electrode body; 22. a joint; 23. an electrode liquid outlet channel; 24. an electrode return channel; 5. a spindle housing; 8. a liquid flushing pump; 9. a suction pump; 10. a liquid storage tank.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Referring to fig. 1-3, an internal flushing liquid negative pressure suction device for high-speed arc discharge machining comprises a rotary main shaft 1, a tool electrode 2, a main shaft shell 5, a suction pump 9, a liquid storage tank 10 and a flushing pump 8, wherein the tool electrode 2 is fixed on the rotary main shaft 1, the rotary main shaft 1 is connected to a machine tool main shaft in an insulating manner and rotates at a high speed along with the machine tool main shaft to realize mechanical motion arc breaking in the machining process; the medium liquid circulates in sequence among the suction pump 9, the liquid storage tank 10, the flushing pump 8, the rotary spindle 1, and the tool electrode 2.

The tool electrode 2 adopts a porous resorption type structure, and the tool electrode 2 comprises an electrode body 21, a joint 22, an electrode liquid outlet channel 23 and a plurality of electrode liquid return channels 24 (see fig. 3). The joint 22 is arranged on the outer wall of the upper part of the electrode body 21 and is used for being connected with the rotating main shaft 1; a through hole is formed in the axis of the electrode body 21 to form the electrode liquid outlet channel 23, the upper end of the electrode liquid outlet channel 23 is communicated with the medium flow channel of the rotating main shaft 1, and the electrode liquid outlet channel 23 is used as an inner flushing flow channel to spray medium liquid to a processing area on the surface of a workpiece; a plurality of electrode liquid return channels 24 are annularly and uniformly distributed on the axial direction of the electrode body 21 around the electrode liquid outlet channel 23, and an annular liquid return loop 11 is arranged on the rotating main shaft 1 and corresponds to the upper ends of the plurality of electrode liquid return channels 24; a circumferential liquid return hole is formed in the spindle shell 5 and corresponds to the liquid return loop 11 (see fig. 1); the electrode return passage 24 is in fluid communication with the suction pump 9 via the return hole, and serves as an external fluid-withdrawal passage for withdrawing the medium fluid from the machining region.

Wherein the joint 22 is preferably a threaded joint.

Alternatively, the electrode outlet channel 23 may be provided in plurality. Preferably centrally disposed within a plurality of electrode return channels 24 arranged in an annular array.

Further, the diameter of the electrode liquid return channel 24 is smaller than the radius of the electrode liquid outlet channel 23.

Alternatively, the liquid return loop 11 and the liquid return holes function to provide a channel for the medium flow to flow back to the liquid storage tank 10 under a negative pressure environment. Preferably on the rotary spindle 1 and the spindle housing 5, respectively.

Processing steps or processes: the tool electrode 2 has an electrode liquid outlet channel 23 (inner flushing liquid channel) and a plurality of electrode liquid return channels 24 (outer liquid suction channels). The tool electrode 2 is fixed on the rotating main shaft 1 and rotates at a high speed along with the rotating main shaft 1, so that the function of mechanical motion arc breaking in the machining process is achieved. The workpiece is fixed on the machine tool workbench. The distance between the tool electrode 2 and the workpiece surface is adjusted to a suitable discharge gap by the machine tool servo motion. During high-speed arc machining, medium liquid in the liquid storage tank 10 reaches a high-pressure state through the liquid-pouring pump 8 and flows through the internal flow channel of the rotating main shaft 1 and the internal flushing flow channel of the tool electrode 2 to provide internal flushing liquid for a machining area, so that the hydrodynamic arc breaking effect is realized. The discharge gap and its surrounding area are filled with the liquid medium due to the action of the flushing liquid in the high-pressure fluid medium. Meanwhile, the external liquid pumping channel of the tool electrode 2 forms negative pressure under the action of the suction pump 9, and liquid media in the discharge gap are pumped away. The final medium liquid is returned to the liquid storage tank 10.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. The high-speed electric arc machining device adopting the resorption type electrode comprises a rotating main shaft (1), a tool electrode (2), a main shaft shell (5), a suction pump (9), a liquid storage tank (10) and a flushing pump (8), wherein the tool electrode (2) is fixed on the rotating main shaft (1), the rotating main shaft (1) is connected to a machine tool main shaft in an insulating way and rotates at a high speed along with the machine tool main shaft to realize mechanical motion arc breaking in the machining process; medium liquid circulates in proper order between suction pump (9), liquid reserve tank (10), towards liquid pump (8), rotatory main shaft (1) and tool electrode (2), its characterized in that:

the tool electrode (2) adopts a porous resorption type structure, and the tool electrode (2) comprises an electrode body (21), a joint (22), an electrode liquid outlet channel (23) and a plurality of electrode liquid return channels (24); the joint (22) is arranged on the outer wall of the upper part of the electrode body (21) and is used for being connected with the rotating main shaft (1); a through hole is formed in the axis of the electrode body (21) to form the electrode liquid outlet channel (23), the upper end of the electrode liquid outlet channel (23) is communicated with the medium flow channel of the rotating main shaft (1), and the electrode liquid outlet channel (23) is used as an inner flushing liquid flow channel to spray medium liquid to a processing area on the surface of a workpiece; the electrode liquid return passage is characterized in that a plurality of electrode liquid return passages (24) are annularly and uniformly distributed around the electrode liquid outlet passage (23) in the axial direction of the electrode body (21), an annular liquid return ring passage (11) is formed in the position, corresponding to the upper ends of the plurality of electrode liquid return passages (24), of the upper portion of the electrode body (21), liquid return holes are formed in the circumferential direction of the liquid return ring passage (11) and are communicated with the suction pump (9) through the liquid return holes, and the electrode liquid return passages (24) are used as outer liquid suction passages to draw back medium liquid in a machining area.

2. The apparatus of claim 1, wherein: the diameter of the electrode liquid return channel (24) is smaller than the radius of the electrode liquid outlet channel (23).

3. The apparatus of claim 1, wherein: the flushing pump (8) comprises a pump body and a control valve; the suction pump (9) comprises a pump body, a control valve and a filter.

4. A method of processing using the apparatus of any of claims 1 to 3, the method comprising:

preparing for electric arc machining, namely fixing a workpiece material on a workbench of a machine tool in an insulating manner, fixing a tool electrode (2) on a rotating main shaft (1), and fixedly connecting the rotating main shaft (1) with a main shaft of the machine tool and keeping the rotating main shaft insulated; connecting the workpiece material and the tool electrode (2) to two poles of a discharge power supply respectively; then the electrode liquid return channel (24) is communicated with the suction pump (9) through a liquid return loop channel (11) arranged on the rotating main shaft (1) and a liquid return hole arranged on the main shaft shell (5); setting a discharge gap between a workpiece material and a tool electrode (2) by a machine tool servo system;

high-speed electric arc machining, wherein medium liquid in a liquid storage tank (10) reaches a high-pressure state through a flushing pump (8) and flows through an electrode liquid outlet channel (23) of a rotating main shaft (1) and a tool electrode (2) to provide high-pressure internal flushing liquid for a machining area; the high-pressure internal flushing liquid realizes hydrodynamic arc breaking and quickly flushes the eroded particles away from the processing area; under the negative pressure environment of a machining gap, medium liquid carrying with corrosion removal particles flows through an electrode liquid return channel (24), a liquid return loop channel (11) on a rotating main shaft (1) and a liquid return hole on a main shaft shell (5) and is filtered by a suction pump (9) and pumped back to a machine tool liquid storage tank (10) to form a liquid supply circulation system;

after the machining is finished and the discharging is stopped, the main shaft of the machine tool stops rotating, the tool electrode (2) stays at the machining finishing position for a short time, and the liquid medium with metal corrosion particles is fully pumped away by a suction pump (9); and then the machine tool is lifted to a safe position through servo motion of the machine tool, and the machine tool is stopped.

5. The method of claim 4, wherein: the discharge power supply adopts a periodic pulse power supply, the voltage value is 30-120V, the peak current is 50-10000A, and the range of the pulse width and the pulse interval is 2-20000 mus.