阅读说明：本技术 一种皮秒激光辅助电火花加工装置及方法 (Picosecond laser-assisted electric spark machining device and method ) 是由 张臻 张意 吴杰 薛涛 张国军 胡麟 于 2020-05-20 设计创作，主要内容包括：本发明公开了一种皮秒激光辅助电火花加工装置及方法,属于特种加工中激光加工与电火花加工复合技术领域,包括：磁场调控单元、皮秒激光诱导等离子体单元和电火花加工单元；磁场调控单元用于在通电后利用磁场调控等离子体羽流与等离子通道外形膨胀与收缩；皮秒激光诱导等离子体单元中皮秒激光器发出的激光经过可调光路转换组件后入射到待加工材料表面诱导产生等离子体；电火花加工单元中通过工作平台用于实现待加工材料沿X轴、Y轴、Z轴平移运动,工作电极在电机驱动下沿Z轴平移和旋转运动,并调节电极间隙,在电极间隙间施加电压触发电火花放电,对待加工材料进行加工。本发明可实现高效低损伤微细加工。(The invention discloses a picosecond laser-assisted electric spark machining device and method, which belong to the technical field of laser machining and electric spark machining in special machining, and comprise the following steps: the device comprises a magnetic field regulation and control unit, a picosecond laser induction plasma unit and an electric spark machining unit; the magnetic field regulating unit is used for regulating and controlling the expansion and contraction of the plasma plume and the plasma channel by utilizing a magnetic field after the power is on; laser emitted by a picosecond laser in the picosecond laser induction plasma unit passes through the adjustable light path conversion component and then is incident to the surface of a material to be processed to generate plasma through induction; the electric spark machining unit is used for realizing the translational motion of a material to be machined along an X axis, a Y axis and a Z axis through a working platform, the working electrode is driven by a motor to perform translational motion and rotary motion along the Z axis, the electrode gap is adjusted, voltage is applied between the electrode gaps to trigger electric spark discharge, and the material to be machined is machined. The invention can realize high-efficiency low-damage micro machining.)

1. A picosecond laser assisted electrical discharge machining apparatus, comprising: the device comprises a magnetic field regulation and control unit, a picosecond laser induction plasma unit and an electric spark machining unit;

the magnetic field regulation and control unit comprises a plurality of pairs of electromagnets (3) and is used for regulating and controlling the expansion and contraction of the plasma plume and the plasma channel appearance by utilizing the magnetic field after the electrification, so that the electric spark discharge points are uniformly distributed;

the picosecond laser induction plasma unit comprises a picosecond laser (5) and an adjustable light path conversion component, and laser emitted by the picosecond laser (5) passes through the adjustable light path conversion component and then is incident to the surface of the material (1) to be processed to generate plasma through induction;

the electric spark machining unit comprises a working platform (4) and working electrodes (10), wherein a plurality of pairs of electromagnets (3) are uniformly distributed above the working platform (4), the working platform (4) is used for realizing the translation motion of the material (1) to be machined along an X axis, a Y axis and a z axis, the working electrodes (10) are used for the translation motion and the rotation motion along the z axis under the drive of a motor and adjusting electrode gaps, voltage is applied between the electrode gaps to trigger electric spark discharge, and the material (1) to be machined is machined.

2. The picosecond laser-assisted electric discharge machining apparatus according to claim 1, wherein the material to be machined is zirconia-type ceramic, titanium alloy, or aluminum-based silicon carbide.

3. The picosecond laser-assisted electric discharge machining device according to claim 1 or 2, wherein the magnetic field regulation and control unit further comprises a direct current power supply bipolar converter and a direct current excitation power supply, wherein the direct current power supply bipolar converter and the direct current excitation power supply are both positioned in a case outside the working platform and are connected with the plurality of pairs of electromagnets through cables;

the direct-current power supply bipolar converter is used for receiving a positive value signal or a negative value signal and then controlling the current direction of a coil in the electromagnet so as to change the polarity of the electromagnet; the direct-current excitation power supply is used for changing the magnetic field intensity by adjusting the current; the electromagnets are combined to form a unidirectional or mutual exclusion magnetic field when the polarity and the magnetic field intensity are changed, the plasma expands under the action of the unidirectional magnetic field, and the plasma contracts under the action of the mutual exclusion magnetic field.

4. A picosecond laser-assisted electric discharge machining apparatus according to claim 1 or 2, wherein the tunable optical path switching assembly comprises a primary reflector (6), a beam expander (7), a final reflector (8) and a focusing prism (9), wherein laser light emitted from the picosecond laser (5) passes through the primary reflector (6) and enters the beam expander (7) to expand the radius, the laser light with the expanded radius enters the final reflector (8) and enters the surface of the material to be machined (1) from an oblique upper direction through the focusing prism (9), and an angle formed by the incident direction of the laser light and the vertical direction of the working electrode (10) is controlled by controlling the angle of the final reflector (8) and the orientation of the focusing prism (9).

5. The picosecond laser assisted electrical discharge machining apparatus of claim 1 or 2, wherein the electrical discharge machining unit further comprises a watershed control module, the watershed control module comprising: a jet pump, a discharge hose and a nozzle, the nozzle is positioned at the lower part of the jet pump,

the jet pump is used for discharging the dielectric medium to a vessel above the working platform (4) for storing the material (1) to be processed through the nozzle, the discharge hose is used for discharging the dielectric medium to realize circulation of the dielectric medium, and the injection direction and the pressure of the jet pump are controlled by adjusting the direction of the nozzle and the size of an internal flow passage of the jet pump.

6. The picosecond laser-assisted electric discharge machining device according to claim 1 or 2, wherein the device further comprises a multi-time scale machining process monitoring unit, the multi-time scale machining process monitoring unit comprises an ICCD high-speed camera (18), a schlieren system (23) and a trigger shutter opening module (17), the trigger shutter opening module (17) is used for controlling the shutter shooting moment of the ICCD high-speed camera (18), and the schlieren system (23) is used for converting the plasma energy density gradient change into the plane relative light intensity change, so that the ICCD high-speed camera (18) shoots the plasma energy density change image, and each development process of the multi-time scale observation machining is realized.

7. A picosecond laser assisted electro-discharge machining apparatus according to claim 6, wherein the trigger shutter opening module (17) is used to control shutter shooting time of the ICCD high speed camera (18) to realize picosecond-nanosecond, nanosecond-microsecond and microsecond-millisecond scale observation.

8. A picosecond laser assisted electric discharge machining apparatus according to claim 6, wherein the apparatus further comprises a temperature monitoring module, the temperature monitoring module comprising an infrared imager (12) and a temperature sensor (13), the infrared imager (12) being adapted to monitor and feed back the temperature distribution of the plasma in real time, and the temperature sensor (13) being adapted to monitor and feed back the temperature distribution of the material (1) to be machined in real time.

9. The picosecond laser-assisted electric discharge machining apparatus according to claim 8, wherein the apparatus further comprises a PC (14), a high speed acquisition card (19) and a control box (20),

one end of the PC (14) is connected with the ICCD high-speed camera (18), and the other end of the PC is connected with the infrared imager (12) and used for receiving a plasma energy density change image shot by the ICCD high-speed camera (18) and the temperature distribution of the plasma fed back by the infrared imager (12) so as to judge the processing state;

one end of the high-speed acquisition card (19) is connected with the PC (14), and the other end is connected with the control box (20) and used for data transmission between the PC (14) and the control box (20);

the control box (20) is internally provided with a magnetic field parameter controller, a picosecond laser parameter controller and an electric spark parameter controller and is used for selecting an optimal magnetic field parameter, an optimal picosecond laser parameter and an optimal electric spark parameter according to the machining state judged by the PC (14), adjusting the time interval between laser pulse and electric spark discharge and obtaining the optimal electric spark discharge time.

10. Picosecond laser assisted electro discharge machining method for machining a material to be machined using a picosecond laser assisted electro discharge machining device according to any of claims 1-9, comprising the steps of:

the picosecond laser emits laser which is transmitted and focused through the adjustable light path conversion component, and finally the laser is incident to the surface of a material to be processed at an inclined angle relative to the working electrode to cause optical breakdown to form plasma, the plasma further absorbs the radiant energy of the incident laser to expand and continuously transfers heat to a processing area, when the temperature of the material to be processed exceeds the conductive threshold temperature of the material to be processed, the material to be processed meets the electrode characteristics, voltage is applied between electrode gaps to trigger electric spark discharge, the processing form and position precision and the processing efficiency are improved, the magnetic field regulating and controlling unit regulates and controls the plasma plume and the plasma channel appearance expansion and contraction by utilizing a magnetic field after being electrified, so that electric spark discharge points are uniformly distributed, and the three-dimensional microstructure manufacturing is realized.

Technical Field

The invention belongs to the technical field of laser machining and electric spark machining in special machining, and particularly relates to a picosecond laser-assisted electric spark machining device and method.

Background

The precision and high-efficiency processing of the high-performance ceramic material is one of the most competitive advanced manufacturing fields in the world at present, and the zirconia type ceramic as a class of advanced functional ceramic taking pure zirconia as a main component has the characteristics of high melting point, low thermal conductivity, low thermal expansion coefficient, corrosion resistance, chemical inertness, good mechanical strength and the like, and has wide application prospect in the military and civil field. However, zirconia-type ceramics have high hardness, large brittleness and non-conductivity at normal temperature, so that complex three-dimensional microstructures such as an air film hole outlet of a aviation blade, micropores of a cover plate of an intelligent terminal and the like are difficult to process by using a traditional method.

The electric discharge machining is a non-contact machining method, in which a voltage is applied between a working electrode and a minute gap of a conductive material to form an ultra-high electric field strength, thereby inducing plasma, and the surface of the material is melted and vaporized by an electro-thermal mechanism having high-temperature plasma. The working principle of the method determines that the electric spark machining is not limited by the hardness of the material, just avoids the brittle defect of the ceramic, but puts certain requirements on the conductivity of the material. Although the zirconia type ceramic is not conductive at normal temperature, the zirconia type ceramic has conductivity when the temperature exceeds 600 ℃, the conductivity is increased along with the temperature rise, and the zirconia type ceramic is a good conductor when the temperature reaches 1000 ℃, so that the zirconia type ceramic is pretreated to reach the conductive critical temperature by adopting a proper auxiliary method, and the realization of an electric spark processing method is facilitated. It is common to use auxiliary conductive electrodes or doping a proper amount of conductive phase inside the ceramic material to realize electric discharge machining, but there are many challenges, including the selection of coating material and coating thickness, the effectiveness of conductive material, etc. all of which have certain limitations.

Therefore, a more targeted and universal method is urgently needed to be developed to assist the electric spark to efficiently machine the zirconia type ceramics and solve the problems that the electric spark machining precision is easily affected by electrode loss, the efficiency is low and the like.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides a picosecond laser auxiliary electric spark machining device and method, so that the technical problems that the electric spark machining precision is easily influenced by electrode loss and the efficiency is low in the prior art are solved.

To achieve the above object, according to one aspect of the present invention, there is provided a picosecond laser-assisted electric discharge machining apparatus comprising: the device comprises a magnetic field regulation and control unit, a picosecond laser induction plasma unit and an electric spark machining unit;

the magnetic field regulation and control unit comprises a plurality of pairs of electromagnets and is used for regulating and controlling the expansion and contraction of the plasma plume and the plasma channel by utilizing the magnetic field after the electromagnets are electrified so as to ensure that the electric spark discharge points are uniformly distributed;

the picosecond laser induced plasma unit comprises a picosecond laser and an adjustable light path conversion component, and laser emitted by the picosecond laser passes through the adjustable light path conversion component and then is incident to the surface of a material to be processed to generate plasma through induction;

the electric spark machining unit comprises a working platform and a working electrode, a plurality of pairs of electromagnets are uniformly distributed above the working platform, the working platform is used for realizing the translational motion of the material to be machined along an X axis, a Y axis and a z axis, the working electrode is used for performing the translational motion and the rotational motion along the z axis under the driving of a motor and adjusting the electrode gap, voltage is applied between the electrode gaps to trigger electric spark discharge, and the material to be machined is machined.

Further, the material to be processed is zirconia-type ceramics, titanium alloy, or aluminum-based silicon carbide.

Furthermore, the magnetic field regulation and control unit also comprises a direct-current power supply bipolar converter and a direct-current excitation power supply, wherein the direct-current power supply bipolar converter and the direct-current excitation power supply are both positioned in a case outside the working platform and are connected with the plurality of pairs of electromagnets through cables;

the direct-current power supply bipolar converter is used for receiving a positive value signal or a negative value signal and then controlling the current direction of a coil in the electromagnet so as to change the polarity of the electromagnet; the direct-current excitation power supply is used for changing the magnetic field intensity by adjusting the current; the electromagnets are combined to form a unidirectional or mutual exclusion magnetic field when the polarity and the magnetic field intensity are changed, the plasma expands under the action of the unidirectional magnetic field, and the plasma contracts under the action of the mutual exclusion magnetic field.

Furthermore, the adjustable light path conversion assembly comprises an initial reflector, a beam expander, a tail end reflector and a focusing prism, laser emitted by the picosecond laser enters the beam expander through the initial reflector to enlarge the radius, the laser with the enlarged radius enters the surface of a material to be processed from the oblique upper side through the focusing prism after reaching the tail end reflector, and the angle formed by the incident direction of the laser and the vertical direction of the working electrode is controlled by controlling the angle of the tail end reflector and the direction of the focusing prism.

Further, the electric discharge machining unit further includes a watershed control module, and the watershed control module includes: a jet pump, a discharge hose and a nozzle, the nozzle is positioned at the lower part of the jet pump,

the jet pump is used for discharging the dielectric medium to a vessel above a working platform for storing materials to be processed through a nozzle, the discharge hose is used for discharging the dielectric medium to realize circulation of the dielectric medium, and the injection direction and the pressure of the jet pump are controlled by adjusting the direction of the nozzle and the size of an internal flow passage of the jet pump. Deionized water, spark oil and other dielectrics can be used as the dielectric to ensure the required processing quality and performance of the finished workpiece.

Furthermore, the device also comprises a multi-time scale processing process monitoring unit, wherein the multi-time scale processing process monitoring unit comprises an ICCD high-speed camera, a schlieren system and a trigger shutter opening module, the trigger shutter opening module is used for controlling the shutter shooting time of the ICCD high-speed camera, and the schlieren system is used for converting the plasma energy density gradient change into the plane relative light intensity change, so that the ICCD high-speed camera shoots the plasma energy density change image, and each development process of the multi-time scale observation processing is realized.

Further, a shutter opening module is triggered and used for controlling the shutter shooting time of the ICCD high-speed camera to realize picosecond-nanosecond, nanosecond-microsecond and microsecond-millisecond scale observation.

Furthermore, the plasma evolution process comprises two aspects, namely a laser-induced plasma and an electric spark plasma evolution process, wherein the single-pulse laser-induced plasma exists about dozens of picoseconds, the observation time span of continuous pulses is generally within ten nanoseconds, the electric spark plasma is rapidly formed within fifty nanoseconds, the plasma is relatively stable and has no obvious change within hundreds of nanoseconds, and the whole time of the electric spark plasma evolution process is in the microsecond level. The multi-time scale processing process monitoring unit is used for accurately observing the evolution process of a plasma aiming at the phenomenon that the development time of each process is different, the flexible configuration of an ICCD high-speed camera and a non-intrusive imaging schlieren system is convenient to be used for observing the composite micro-processing process of 'magnetic field-picosecond laser-electric spark' in a multi-time scale manner, clearly tracking the space-time evolution of the plasma and the removal characteristics of a material to be processed, a trigger shutter opening module is the most important part of the multi-time scale observation unit, the control on a shutter is divided into two branches, one branch comprises a delay element and an enhancement module, when a laser sends pulse laser, a trigger pulse signal is sent to the delay element at the same time, then delay pulses are transmitted to the enhancement module, the control on the shooting time of the camera shutter is realized, and the appearance and energy distribution change of the plasma in the process from generation to the attenuation are, the method is helpful for qualitatively and quantitatively describing the time-space evolution process of the laser-induced plasma under the coupling action of the magnetic field-optical field-electric field. The other branch comprises a closed open-loop current sensor, an oscilloscope and a trigger shutter opening module, wherein the current sensor is used for detecting the current in a loop under the action of the micro electric spark and simultaneously triggering the oscilloscope to act, the oscilloscope rapidly sends a trigger signal to the ICCD high-speed camera through the trigger shutter opening module to control the opening and closing of the shutter of the camera, and the trigger shutter opening module is used for realizing the whole evolution process from formation to stabilization and dissipation of the plasma channel of the electric spark in a nanosecond-microsecond scale observation mode so as to be beneficial to qualitatively and quantitatively describing the plasma channel evolution process under the action of a multi-physical field.

Furthermore, aiming at the time scale of the removal process of the material to be processed, the pulse trigger shutter opening strategy of two branches in the multi-time scale observation unit is adjusted, the shooting interval time is changed, the whole process of material removal caused by melting and vaporization of the material to be processed, the formation process of recasting and the liquid medium back-streaming caused by bubble generation, growth, rupture and plasma collapse is observed in a microsecond-millisecond scale mode, the motion track and the microstructure formation process of the material to be processed in the fluid are captured, and the motion track and the microstructure formation process of the material to be processed under the coupling action of a magnetic field, an optical field and an electric field are qualitatively and quantitatively described.

Further, the device still includes the temperature monitoring module, the temperature monitoring module includes infrared imager and temperature sensor, infrared imager is used for real-time supervision and feedback plasma's temperature distribution, temperature sensor is used for real-time supervision and feedback waiting to process the temperature distribution of material.

Furthermore, the device also comprises a PC machine, a high-speed acquisition card and a control box,

one end of the PC is connected with the ICCD high-speed camera, and the other end of the PC is connected with the infrared imager and used for receiving the plasma energy density change image shot by the ICCD high-speed camera and the temperature distribution of the plasma fed back by the infrared imager so as to judge the processing state;

one end of the high-speed acquisition card is connected with the PC, and the other end of the high-speed acquisition card is connected with the control box and is used for data transmission between the PC and the control box;

the control box is internally provided with a magnetic field parameter controller, a picosecond laser parameter controller and an electric spark parameter controller and is used for selecting an optimal magnetic field parameter, an optimal picosecond laser parameter and an optimal electric spark parameter according to the machining state judged by the PC, adjusting the time interval between laser pulse and electric spark discharge and obtaining the optimal electric spark discharge time.

According to another aspect of the present invention, there is provided a picosecond laser-assisted electric discharge machining method, wherein the method uses a picosecond laser-assisted electric discharge machining apparatus for machining a material to be machined, comprising the steps of:

the picosecond laser emits laser which is transmitted and focused through the adjustable light path conversion component, and finally the laser is incident to the surface of a material to be processed at an inclined angle relative to the working electrode to cause optical breakdown to form plasma, the plasma further absorbs the radiant energy of the incident laser to expand and continuously transfers heat to a processing area, when the temperature of the material to be processed exceeds the conductive threshold temperature of the material to be processed, the material to be processed meets the electrode characteristics, voltage is applied between electrode gaps to trigger electric spark discharge, the processing form and position precision and the processing efficiency are improved, the magnetic field regulating and controlling unit regulates and controls the plasma plume and the plasma channel appearance expansion and contraction by utilizing a magnetic field after being electrified, so that electric spark discharge points are uniformly distributed, and the three-dimensional microstructure manufacturing is realized.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

(1) the device organically combines the magnetic field regulation and control unit, the picosecond laser induced plasma processing unit and the electric spark processing unit together, solves the problems that the normal-temperature non-conductive zirconia type ceramic material is difficult to process and the processing precision and the processing efficiency are not high enough in the micro electric spark processing technology, is favorable for popularizing the zirconia type ceramic to the high-precision manufacturing field and applying the zirconia type ceramic to the processing of wider materials, and the method is effective to the materials which are not conductive at normal temperature but have conductivity at high temperature, such as zirconia type ceramic, titanium alloy and aluminum-based silicon carbide.

(2) The picosecond laser beam generated by the laser passes through the adjustable light path conversion component, transmits the laser beam and focuses the laser beam to the processing area, the incident direction and the electrode vertical direction form a certain angle, the angle is adjustable, the laser can be focused at different positions of a workpiece, the high-power picosecond laser induces the liquid medium or the material to be processed to generate plasma to trigger electric spark discharge processing, the advantages of high precision and efficiency of picosecond laser processing and high stability of micro electric spark processing are integrated, and the problem that the material to be processed cannot be directly processed by electric sparks due to non-conduction at normal temperature is solved.

(3) In the process of the picosecond laser machining and micro electric spark machining combined process, the magnetic field is introduced to conveniently regulate and control the appearance and energy density distribution of the plasma plume and the plasma channel, so that the plasma expands or contracts, the machining efficiency is improved, and the three-dimensional structure with complex shape is favorably machined.

(4) The flexible configuration of the ICCD high-speed camera and the non-intrusive optical imaging schlieren system can capture weak plasma energy, a shot high-resolution image can reflect the energy distribution of plasma plumes and plasma channels more truly, and the energy distribution and the shape evolution of the plasma in the multi-time scale monitoring composite processing process and the removal process of a material to be processed in an immersion environment can be realized by using a pulse trigger mechanism in cooperation with a trigger shutter opening module.

(5) The infrared imager and the wireless temperature sensor are matched with each other, so that the temperature distribution of the workpiece can be accurately monitored, the normal operation of the composite processing process of the material to be processed is ensured, and the action time of laser pulse and electric pulse in a processing area is determined.

(6) The invention connects the control box for regulating and controlling the magnetic field, the laser and the electric spark parameters with the high-speed acquisition card, combines the image data received by the PC port from the ICCD high-speed camera, can be used for identifying and evaluating the processing state, feeds back and adjusts the technological parameters of the multiple physical fields, optimizes the composite processing technology and improves the processing performance and quality.

Drawings

Fig. 1 is a structural diagram of a picosecond laser-assisted electric discharge machining apparatus according to an embodiment of the present invention;

FIG. 2 is a diagram illustrating the deployment and control of a working platform according to an embodiment of the present invention;

FIG. 3 is an elevation view of an electrical discharge machining unit and a watershed control module provided in an embodiment of the present invention;

FIG. 4 is a three-dimensional view of an electrical discharge machining unit and a watershed control module provided in an embodiment of the present invention;

FIG. 5 is a schematic diagram of a magnetic field regulation mechanism provided in an embodiment of the present invention;

FIG. 6 is a plan view of an electromagnet deployment control provided in an embodiment of the present invention;

FIG. 7 is a three-dimensional view of an electromagnet from a perspective provided by an embodiment of the present invention;

FIG. 8 is a three-dimensional view of an electromagnet from another perspective provided by an embodiment of the present invention;

FIG. 9 is a schematic diagram of a high resolution observation and camera shutter control flow path provided by an embodiment of the present invention;

FIG. 10 is a schematic diagram of the time control of a fully trapped plasma provided by an embodiment of the present invention;

FIG. 11 is a schematic diagram of an adjustable optical path conversion assembly according to an embodiment of the present invention;

FIG. 12 is a diagram illustrating a multi-physics process parameter control architecture according to an embodiment of the present invention;

the same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein:

1 is a material to be processed, 2 is a transparent high-temperature glassware, 3 is an electromagnet, 4 is a working platform, 5 is a picosecond laser, 6 is an initial reflector, 7 is a beam expander, 8 is a tail reflector, 9 is a focusing prism, 10 is a working electrode, 11 is an electrode clamp, 12 is an infrared imager, 13 is a temperature sensor, 14 is a PC, 15 is a closed open-loop current sensor, 16 is an oscilloscope, 17 is a trigger shutter opening module, 18 is an ICCD high-speed camera, 19 is a high-speed acquisition card, 20 is a control box, 21 is a direct current power supply bipolar converter, 22 is a direct current excitation power supply, 23 is a schlieren system, 24 is a delay element, 25 is an enhancement module, 26 is a tube shell, 27 is a hinged support, 28 is a hydraulic rod, 29 is a temperature monitoring module, 30 is a jet pump, 31 is a discharge hose, 32 is a circular slide rail, 33 is a linear slide rail, 34 is a cable hole, a laser beam, 35 is a slide block, 36 is a nozzle, and 37 is a hinged support.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In special machining, electric spark machining and picosecond laser-induced plasma machining are widely applied to various fields such as aerospace, 3C intelligent terminals and the like, and micropores with large depth ratio can be machined, so that the micro-holes can be used for manufacturing cooling layer films of turbine blades, thermal protection coatings on the surfaces of airplanes and various types of dies. However, both of the two special processing methods have respective advantages and limitations, and the stability in electric spark processing is good, but the processing precision and efficiency are low compared with laser-induced plasma processing, and the most important thing is that the object of electric spark processing needs to be a material with higher conductivity, picosecond laser-induced plasma processing is not limited by the conductivity of the material, the efficiency and the precision are high, the heat affected zone is small, but the processing process is easily affected by bubbles and impurities, and the stability is insufficient. The zirconia type ceramic is an advanced functional ceramic taking pure zirconia (ZrO2) as a main component, has the excellent characteristics of high melting point, low thermal conductivity, low thermal expansion coefficient, corrosion resistance, chemical inertness, good mechanical strength and the like, has lower density than metals such as titanium alloy and the like, can greatly reduce the whole weight of an aircraft once being widely applied to the field of aerospace, and is non-conductive at normal temperature and conductive when being heated to 600 ℃. The core concept of the invention is to organically combine two special processing methods together, and make full use of the advantages of a magnetic field on the regulation and control capability of the plasma plume and the plasma channel appearance and energy density distribution, the magnetic field, picosecond laser induced plasma and the micro electric spark, so as to provide a process and a device for picosecond laser assisted electric spark micro processing of zirconia ceramics.

In the invention, a picosecond laser beam firstly induces the surface of a medium or a workpiece to generate plasma by using a high-power laser, after the action of a multi-pulse laser, the surface of the zirconia type ceramic material is rapidly heated to the conductive threshold temperature thereof through the heat accumulation temperature to meet the conductive condition of an electrode, and then voltage is applied to a gap between a tool electrode and the surface of the workpiece to generate a discharge plasma channel, so that the material is further corroded and removed under the action of continuous pulse discharge. In the processing process, a high-resolution observation system consisting of a schlieren system and an ICCD high-speed camera is used for observing the plasma evolution and material removal conditions in a processing area, and the change rule of each processing stage is monitored in a multi-time scale mode by matching with a trigger shutter strategy. The infrared imager and the wireless temperature sensor monitor the temperature distribution of the processing area together so as to ensure the effective and safe work of the processing process. The image data output by the observation system and the process parameter data acquired by the high-speed acquisition card are evaluated by the built-in analysis system of the PC, and then fed back to the control box to adjust the magnetic field parameters, the laser parameters and the electric spark parameters, optimize the process and improve the processing performance and quality.

The process of the present invention will be described in further detail below with reference to the drawings by taking the example of processing zirconia-type ceramics.

As shown in figure 1, a material (namely zirconia type ceramic) 1 to be processed is placed in a transparent high-temperature glass vessel 2 filled with a dielectric medium, the type of the dielectric medium in the glass vessel 2 can be changed, paired electromagnets 3 are arranged on the periphery of the glass vessel, the glass vessel 2 and the electromagnets 3 are tightly attached to a working platform 4, the working platform 4 can move along an X axis and a Y axis under the drive of a motor, in addition, a flow domain control module is arranged on the working platform to assist the dielectric medium to generate different fluid dynamics states inside, the cooling and cavitation impact effects of the process are strengthened, a picosecond laser 5 enters a beam expander 7 through an initial reflector 6, a laser beam with enlarged radius enters a tail end reflector 8 and then enters the surface of the zirconia type ceramic from the oblique upper part through a focusing prism 9, and the incident direction of the laser beam forms a certain angle with the vertical direction of an electric spark working electrode 10, the electrode holder 11 is controlled by a motor to rotate and move the working electrode 10 along the z-axis. The infrared imager 12 and the wireless temperature sensor 13 monitor the temperature condition of the zirconia type ceramic processing area in real time, and output the temperature data to the PC 14 in time, and the PC 14 analyzes the temperature distribution, thereby avoiding the conditions of overhigh temperature and overlow temperature and giving an alarm when the temperature is abnormal. A closed open-loop current sensor 15 is installed in a micro electric spark loop and connected with an oscilloscope 16, an ICCD high-speed camera 18 is enabled to act by triggering a shutter opening module 17, appearance and energy distribution changes of plasmas in the processes from generation to attenuation are observed in a picosecond-nanosecond scale, the space-time evolution process of laser-induced plasmas under the coupling action of a magnetic field, an optical field and an electric field is described qualitatively and quantitatively, a high-speed acquisition card 19 is connected with a control box 20, electric spark parameters, laser parameters and magnetic field parameter data are transmitted to a PC 14, an intelligent analysis system is arranged in the PC 14, process parameter data and image data shot by the ICCD high-speed camera 18 are evaluated and fed back to the control box 20, and machining process parameters are regulated and controlled.

Fig. 2 is a layout and control diagram of a processing working platform in an embodiment of the invention, and it can be known from the diagram that a high temperature resistant transparent circular vessel 2 is installed on the inner layer of the surface of a working platform 4, a circular slide rail 32 and a linear slide rail 33 are installed on the periphery of the working platform, six electromagnets 3 are respectively installed on the six linear slide rails 33, and an electric spark processing unit and a watershed control module are installed on the upper part of the working platform 4.

Fig. 3 and 4 are a front view and a three-dimensional view of an electric discharge machining unit and a watershed control module according to an embodiment of the present invention, respectively, and it can be seen from the drawings that the movable electrode holder 11 is used for fastening the electric discharge working electrode 10, the electrode type can be changed at will, only the size requirement of the electrode holder 11 needs to be met, a watershed control module is arranged beside the electric discharge machining unit, the upper part of the jet pump 30 is an internal flow channel, the lower nozzle 36 can rotate in a half plane under the drive of the hinged support 37, the pressure control of the rotary nozzle 36 and the jet pump 30 cooperate to change the watershed state of the material to be machined, and the dielectric ejected by the jet pump 30 is discharged from the discharge hose 31 to realize the circulation of the dielectric.

Fig. 5 is a schematic diagram of a mechanism for regulating and controlling a magnetic field in an embodiment of the present invention, fig. 6 is a plan view of arrangement and control of an electromagnet in an embodiment of the present invention, and fig. 7 and 8 are three-dimensional diagrams of an electromagnet in an embodiment of the present invention. The electromagnet 3 is arranged on a sliding block 35, the sliding block 35 can move back and forth on a linear sliding rail 33, the linear sliding rail 33 is arranged on a circular sliding rail 32, six linear sliding rails 33 can rotate around the circle center of the circular sliding rail 32, and a cable hole 34 is formed in the back of the electromagnet and used for being connected with an external direct-current excitation power supply 22. The combination of the magnetic field intensity and the magnetic field direction forms different magnetic field configurations, and when a unidirectional two-dimensional magnetic field is formed, the plasma expands; when a closed mutual exclusion magnetic field is formed, the plasma is compressed, the shape structure of the plasma is changed by the magnetic field regulation and control technology of the process, different shapes such as a spherical shape, an ellipsoid shape, a crescent shape, a groove shape, an annular shape and the like are generated, and a complex three-dimensional structure can be processed. In addition, the ICCD high-speed camera 18 and the schlieren system 23 form a high-resolution observation system, and the appearance and energy distribution evolution of the plasma are observed on a ps-ns time scale by matching with a trigger camera shutter control strategy.

Fig. 9 is a schematic diagram of a high-resolution observation and camera shutter control process in the embodiment of the present invention, and fig. 10 is a schematic diagram of a time control principle of completely capturing plasma in the embodiment of the present invention, from which it can be seen that a plasma plume is generated by the laser induction generated by the picosecond laser 5, and the plasma plume passes through the high-speed schlieren system 23 to convert the plasma energy density gradient change into a planar relative light intensity change, so that the plasma plume is located at a side far from the camera, and the effective imaging precision is concentrated in the plume region, and the plasma energy can be captured and finally imaged on the ICCD high-speed camera 18, so as to truly reflect the state change of the processing region. At the moment when the picosecond laser 5 emits a laser pulse, a trigger pulse is simultaneously sent to the delay element 24, and immediately after the delay element 24 sends a delay pulse to the enhancement module 25, the opening or closing of the shutter of the ICCD high speed camera 18 is controlled. The delay time is changed by controlling the delay element 24, so that the ICCD high-speed camera 18 can be ensured to completely capture the peak intensity of the plasma plume, and the whole evolution process from formation to stabilization and dissipation of the electric spark plasma is observed on a nanosecond-microsecond scale.

The trigger shutter control branch for observing the micro electric spark discharge plasma channel and the laser-induced plasma plume is shown in fig. 1 and fig. 9 respectively, and the shooting interval time is changed by adjusting a trigger shutter opening module in the electric spark branch and a delay element 24 in the laser-induced plasma processing branch in the multi-time scale observation unit, so that the microsecond-millisecond scale observation of the material removal process of the zirconia-type ceramic under the action of thermal energy or mechanical energy is realized, and the motion track and the microstructure forming process of ceramic particles in fluid are captured.

Fig. 11 is a schematic diagram of an adjustable optical path conversion component in an embodiment of the present invention, and it can be seen from the diagram that a picosecond laser 5 and the adjustable optical path conversion component are both packaged in the same square housing, the adjustable optical path conversion component is composed of reflection mirrors 6 and 8, a beam expander 7, and a focusing prism 9, the initial reflection mirror 6 and the beam expander are both fixed in the housing, the focusing prism 9 is fixed in a cylindrical tube housing 26, the reflection mirror 8 is a terminal reflection mirror, and is mounted on a hinged support 27, an angle θ of the reflection mirror 8 is controlled by a control box 20, and at the same time, a hydraulic rod 28 is controlled to act, so as to drive the focusing prism 9 in the tube housing 26 to change its orientation, and it is ensured that laser emitted from the reflection mirror 8 always passes through the focusing prism 9 and enters a workpiece processing area from an oblique.

FIG. 12 is a diagram of a control structure of multiple physical field process parameters in an embodiment of the present invention, and it is known from the figure that a magnetic field parameter controller, a picosecond laser parameter controller and an electric spark parameter controller are all packaged in the same control box 20, the control box 20 and a temperature monitoring module 29 are all connected to a high-speed acquisition card 19, the high-speed acquisition card 19 is simultaneously connected to a PC 14, the other end of the PC 14 is connected to an ICCD high-speed camera 18, the PC 14 is used for receiving image data of plasma energy evolution and material removal captured by the ICCD high-speed camera 19, the high-speed acquisition card 19 is used for acquiring data of magnetic field parameters, laser parameters, electric spark parameters and external parameters in the control box 20 and transmitting the data to the PC 14, the PC firstly sets initial processing process parameters according to user processing requirements, and as the processing continues, an intelligent analysis system built in the PC 14 analyzes temperature data in the temperature monitoring module 29, in case of over-high or over-low temperature, the PC 14 gives an alarm in time when a fault occurs, and evaluates received process parameter data and image data, judges whether the current processing state is the optimal processing state, and feeds the optimal processing state back to the control box 20, each process parameter controller in the control box 20 drives a lower-level execution mechanism, such as an electric spark working platform 4, a picosecond laser 5, a hydraulic push rod 28 and the like to rapidly act, so that the optimal magnetic field parameter, the picosecond laser parameter, the electric spark parameter and auxiliary parameters are selected, the time interval between the laser pulse and electric spark discharge is adjusted according to the analysis result, the optimal electric spark discharge time is obtained, the real-time monitoring and feedback mechanism ensures that the processing is always in an efficient working state, and the process parameters are at the optimal level.

When the zirconia ceramic is processed, under the action of regulating and controlling the plasma by a magnetic field, the plasma is induced by using laser, so that the breakdown voltage of an electrode gap can be effectively reduced, the high-temperature plasma heat conduction enables the zirconia ceramic material to locally reach the conductive threshold temperature, and then voltage is applied between the electrode gaps to trigger electrode discharge, so that the micro electric spark processing can effectively act, and the processing performance and quality are improved.

The invention solves the problem that the electric spark processing technology can not be used for directly processing the normal temperature zirconia ceramic based on the high temperature conductive characteristic of the zirconia ceramic, integrates the advantages of good stability of micro electric spark processing and high processing precision and efficiency of picosecond laser induced plasma, simultaneously utilizes the good regulation and control capability of a magnetic field to the appearance and energy density distribution of the plasma, can improve the surface quality, the processing precision and the processing efficiency of workpieces, can be used for processing three-dimensional structures with complex appearance, has wide application prospect in the field of aerospace, realizes the multi-time scale processing process monitoring device for observing the evolution of plasma plumes and plasma channels and the removal process of the zirconia ceramic material, regulates and controls multiple process parameters through a set of parameter feedback control mechanism, optimizes the processing technology and further improves the processing performance and quality, the introduction of the temperature detection module also ensures the effectiveness and safety of processing the zirconia type ceramic, and besides processing the zirconia type ceramic, the process can also be applied to processing other materials, so that good processing quality can be obtained.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.