CN101856753A - Photoelectrochemical three-dimensional processing method and device of laser cavitation - Google Patents

Abstract

A photoelectrochemical three-dimensional processing method and device of laser cavitation, which belong to the field of special composite processing of manufacturing technology. In this method, after the laser beam is irradiated to generate bubbles on the surface of the workpiece in the solution, the cavitation formed by the collapse of the bubbles is combined with the electrochemical reaction, so that the workpiece material is removed under the action of the photoelectrochemical reaction, and the etching process is realized. In the computer, the computer-controlled liquid crystal screen with grayscale graphic display is used as a mask. When the laser beam passes through the liquid crystal mask, an image with grayscale characteristics is generated to spatially modulate the energy distribution in the laser spot. The area with high laser irradiation energy on the workpiece has strong cavitation effect, fast photoelectrochemical reaction, and large erosion amount; the area with low energy, on the contrary, realizes the processing of three-dimensional graphics. The invention is applicable to the removal processing of conductive metal materials, and can remarkably improve the processing efficiency of complex three-dimensional graphics by controlling the grayscale graphic display of the liquid crystal mask by a computer.

Description

Photoelectrochemical three-dimensional processing method and device of laser cavitation

technical field

The invention relates to the field of special composite processing in manufacturing technology, in particular to a photoelectrochemical three-dimensional processing method and device of laser cavitation, which is suitable for non-contact three-dimensional forming processing of conductive metal materials.

Background technique

Electrochemical processing and laser processing are both special processing technologies. Among them, electrochemical machining is a manufacturing technology that uses electrochemical reactions to dissolve and remove workpiece materials to achieve forming processing. Laser processing is a manufacturing technology that uses a laser beam with high energy density to irradiate the surface of a workpiece to change its shape and structure. When the electrochemical reaction is irradiated by high-energy laser, a series of light, heat and nonlinear effects will be generated on the surface of the electrode, which will cause a photoelectrochemical reaction on the surface of the material. Compared with conventional electrochemical reactions, photoelectrochemical reactions have remarkable characteristics:

(1) The electrochemical polarization potential of the laser irradiation area changes, and the equilibrium potential of the electrode shifts positively, so that the activation energy of the electrode reaction is reduced, and the electrochemical reaction is more likely to occur. And the stronger the laser, the greater the positive shift in potential.

(2) Appropriate laser wavelength can cause light energy absorption in the system. Due to the high spatial resolution of the laser, it can only excite and induce photoelectrochemical reactions in the illuminated area on the substrate, so that it can be used in the study of localized electrochemical reactions. Play an important role.

(3) After the electrode material absorbs the laser energy, it converts it into heat energy, forming a temperature gradient at the electrode/solution interface. The closer to the interface, the higher the solution temperature, and vice versa. Thus, strong micro-convection is generated in the solution, and the mass transfer process of electrochemical reaction ions is accelerated, so that the reaction speed is accelerated.

Therefore, the essence of photoelectrochemical processing is that the high-energy laser beam changes the electrode state in the irradiated area, stimulates and induces the electrochemical reaction, controls the action area of the electrochemical reaction, and simultaneously increases the electrochemical reaction current and reaction speed. According to the retrieved information, the research on photoelectrochemical technology at home and abroad is to use the principle of photocathode protection of metals to apply it to the field of corrosion and protection of materials; Removal of similar materials.

Chinese patent "jet liquid beam electrolysis-laser composite processing method and its device", patent number: CN1919514A proposes: while laser processing is combined with a high-speed jet electrolyte beam coaxial with the laser beam, the laser is used under the guidance of the jet liquid beam The photothermal effect removes the material, and the cathode polarized electrolyte beam cools, scours and electrochemically dissolves the laser processing area, and removes the recast layer processed by the laser. In this method, when the laser beam passes through the electrolyte injection cavity, part of the energy of the laser will be absorbed by the electrolyte, and the refraction and scattering of the electrolyte will also affect the conduction of the beam, which will inevitably cause the loss of laser energy, and it is difficult to achieve laser energy. Efficient transport in and electrochemical machining systems.

Contents of the invention

The purpose of the present invention is to solve the above-mentioned problems existing in composite processing by photoelectrochemical reaction, and propose a method that can realize three-dimensional forming processing, has good controllability in the material removal area, and can flexibly change the processing pattern, and is suitable for the processing of metal conductive materials. Methods and devices.

A photoelectrochemical three-dimensional processing method of laser cavitation, characterized in that: when the high-energy nanosecond pulse laser penetrates the solution and irradiates the surface of the metal target, the energy of the laser radiation makes the irradiated area superheated rapidly, and the The optical breakdown of the solution generates bubbles on the target/solution interface. When the bubbles collapse, the pressure gradient on the surface will form a high-speed liquid jet, which will cause pulsating impact of cavitation on the target.

The above photoelectrochemical three-dimensional processing method of laser cavitation is characterized in that a liquid crystal screen capable of graphic display controlled by a computer is used as a mask. The liquid crystal mask can display graphics with grayscale features, and realizes spatial modulation of energy distribution in the laser spot by using the difference in the laser transmittance between the grayscale difference of each area in the graphics. In this way, the transmitted laser beam becomes a light spot that is opposite to the liquid crystal mask pattern, and the laser energy distribution is controlled by the gray scale of the liquid crystal.

The photoelectrochemical three-dimensional processing method of the above-mentioned laser cavitation is characterized in that: in the photoelectrochemical processing system combined with laser and electrochemistry, ITO conductive glass is used as the tool electrode, and it can be used as the tool cathode to form the current loop of the electrochemical reaction , and through the laser beam emitted by the laser, it ensures the efficient recombination of laser energy and electrochemical system. Therefore, when the laser beam emitted by the laser is spatially modulated by the liquid crystal mask, it is focused and irradiated on the metal workpiece through the ITO (indium tin oxide, indium tin oxide) electrode and the electrolyte, the generated cavitation The combined action and electrochemical action make the workpiece material be removed under the action of photoelectrochemical reaction, realizing three-dimensional etching processing.

The device for realizing the photoelectrochemical three-dimensional processing method of laser cavity cavitation includes a laser, a transmission optical path, and a compound processing and detection part. According to the forward direction of the laser beam, the order is laser → beam expander system → liquid crystal mask → focusing system → conductive glass electrode → electrolyte → workpiece. The composite processing and detection part is composed of conductive glass electrodes, workpiece, processing chamber, worktable, electrolyte, voltmeter, ammeter, and electrochemical processing power supply. The negative electrode of the electrochemical processing power supply is connected to the conductive glass as the cathode, and they are connected in series. The ammeter detects the processing current; the positive pole of the power supply is connected to the workpiece as the anode, and the voltmeter is connected in parallel with the workpiece and the conductive glass to detect the processing voltage. Among them, the conductive glass electrode is the key component for the mutual coupling of laser energy and electrochemical action to realize photoelectrochemical reaction.

A photoelectrochemical three-dimensional processing method of laser cavitation is realized according to the following technical scheme:

(1) Use the LCD screen that can be controlled by the computer to display grayscale graphics as a mask, design the control instructions for displaying graphics according to the required forming requirements, and input them into the computer that controls the LCD screen display.

(2) Select laser energy, beam diameter and other process parameters according to the depth of the shape to be processed on the surface of the workpiece and the size of the processing area.

(3) Adjust the focal length of the beam expander system according to the laser energy and the damage threshold of the liquid crystal screen.

(4) Adjust the focal length of the focusing system according to the external dimensions of the workpiece surface processing part.

(5) The laser light emitted by the laser is processed by the beam expander system and then reaches the liquid crystal mask. Since the mask pattern has grayscale characteristics, that is, different parts of the pattern have different grayscales, and the transmittance to the laser beam is also different. Adjustment of beam space energy distribution. The laser beam passing through the liquid crystal mask becomes a light spot with gray-scale pattern characteristics, and the light spot pattern and the image displayed by the liquid crystal mask form an inverse relationship, and finally the laser beam is imaged on the surface of the workpiece by the focusing system.

(6) The workpiece to be processed is installed in the processing chamber, and the ITO conductive glass electrode is installed and fixed above the workpiece. The workpiece is connected to the positive pole of the electrochemical machining power supply, the conductive glass is connected to the negative pole of the power supply, and a voltmeter and an ammeter are added to the circuit to detect the processing status, thus forming an electrochemical machining system.

(7) After the circuit is connected, start the electrolyte pump to fill the processing cavity with electrolyte, completely immerse the workpiece to the glass substrate of the ITO electrode, and keep the electrolyte circulating between the electrodes. The laser beam passes through the ITO conductive glass electrode through the transmission optical path, and irradiates the surface of the workpiece after passing through the electrolyte; the electrochemical processing power supply is energized, and the surface processing area of the workpiece undergoes a photoelectrochemical reaction under the action of laser irradiation. Under the adjustment of the grayscale pattern of the liquid crystal mask, in the area with high laser energy, the cavity cavitation effect is strong, the photoelectrochemical reaction speed is fast, and the ablation amount is large; in the area with low energy, the cavity cavitation effect is weak, and the photoelectrochemical reaction The speed is slow and the amount of ablation is small, and the photoelectrochemical three-dimensional processing of laser cavitation is finally realized.

The present invention has the following technical advantages:

(1) In the transmission optical path of the laser, a liquid crystal screen that can display grayscale graphics is used as a mask, and the transmittance of the laser beam is different by using the grayscale difference of the graphics, so that the spatial adjustment of the energy distribution of the laser beam can be realized, that is, gray The darker the part, the less the energy of the transmitted laser beam, and the lighter the part, the more the transmitted laser beam energy. When the laser beam adjusted by the energy distribution is irradiated on the surface of the workpiece, the area with high energy has a fast reaction speed and a large amount of material ablation; the area with low energy has a slow response speed and a small ablation amount, and three-dimensional graphics with different depths can be processed. Thus, three-dimensional processing of photoelectrochemical reactions can be realized.

(2) Since the graphics displayed by the liquid crystal mask can be controlled by a computer, when the graphics to be processed are changed, it is not necessary to make another mask, and only need to modify the control instructions of the computer to quickly change the mask graphics to achieve Laser electrochemical composite processing of various complex graphics. The processing area is effectively controlled by the high-resolution laser that passes through the liquid crystal mask, so various patterns can be processed conveniently and flexibly, and the processing accuracy and efficiency are guaranteed while shortening the mask production cycle.

(3) The ITO conductive glass electrode is used as the tool cathode for electrochemical processing. After the power is turned on, an electric field can be formed in the electrolyte between the tool and the workpiece; at the same time, it can also pass through the high-energy laser beam with a mask pattern. In this way, the efficient coupling of laser energy and electrochemical action is ensured, and the material removal of the processed area on the workpiece is realized.

Description of drawings

Fig. 1 is a schematic block diagram of a photoelectrochemical three-dimensional processing method of laser cavitation.

Figure 2 is an example of a processed elliptical three-dimensional pit, and the processing depth gradually changes along the long axis of the ellipse.

Label name in Fig. 1: 1, laser device, 2, laser beam 3, beam expander system, 4, liquid crystal mask, 5, focusing system, 6, ITO conductive glass electrode, 7, nonlinear electrolyte, 8, workpiece, 9. Machining chamber, 10. Workbench, 11. Voltmeter, 12. Ammeter, 13. Electrochemical processing power supply, 14. Control signal, 15. Computer.

Detailed ways

Embodiment: below in conjunction with Fig. 1, work situation and embodiment of the present invention are described in detail.

The device for implementing the method includes sequentially connected lasers 1, transmission light paths and compound processing and detection parts. The transmission optical path includes: beam expander system 3, liquid crystal mask 4, focusing system 5 and ITO conductive glass electrode 6; the composite processing and detection part consists of conductive glass electrode 6, workpiece 8, processing chamber 9, workbench 10, voltmeter 11, Ammeter 12 and processing power supply 13 form.

The laser generates a laser beam 2 with an energy of 0.1-1 joule, a pulse time of 5 nanoseconds, and a wavelength of 1064 nanometers, and the mode of the laser spot is fundamental or multi-mode. The role of the laser is to control the active area of the photoelectrochemical reaction, increase the reaction current and reaction speed, so the power density is not required, thereby reducing the equipment cost of the laser and improving the processing efficiency.

The laser beam 2 emitted by the laser is processed by the beam expander system to make its energy density lower than the damage threshold of the liquid crystal screen, which overcomes the defect that the mask is easily damaged after laser irradiation; at the same time, the liquid crystal screen displays an enlarged image of the processed shape, It can avoid the processing shape being blurred due to diffraction when the processing line width is too small. The liquid crystal screen adopts a transmissive twisted nematic liquid crystal display panel, and the damage threshold of the laser beam emitted by the laser to the liquid crystal screen is 2.5J/cm ² . The laser beam is irradiated on the liquid crystal mask 4, and the grayscale pattern displayed on the liquid crystal screen forms an inverse relationship with the processing pattern, that is, the parts that do not need to be processed in the processing pattern appear black on the liquid crystal screen, and the parts that need to be processed are colorless. Parts with a shallow processing depth are displayed in a light color, and parts with a deep processing depth are displayed in a dark color. After the laser beam passes through the liquid crystal mask pattern with different gray levels in each part, a pattern spot with energy density consistent with the surface processing pattern of the workpiece is formed. Then, the focus system 5 is used to converge the laser beam to reduce the diameter of the spot and increase the energy density, and finally irradiate the surface of the workpiece through the ITO conductive glass electrode 6 and the circulating nonlinear electrolyte 7 . The transmittance of the conductive and light-transmitting ITO conductive glass to the laser is greater than 85%, and the resistivity is 1-5×10 ^-4 Ω/cm.

The circuit connection of the electrochemical processing part includes that the workpiece 8 is connected to the positive pole of the processing power supply 13, and an ammeter is connected in series between them to detect the machining current; the conductive glass electrode 6 is connected to the negative pole of the power supply 13, and the distance between the conductive glass and the workpiece is kept 2-3mm The voltmeter is connected in parallel with the workpiece and the conductive glass to detect the processing voltage, and the various states of the processing process can be detected by using the voltmeter and ammeter. The photoelectrochemical reaction solution uses a _NaNO3 electrolyte with a mass concentration of 10% to 15%. The electrolyte completely immerses the workpiece to the glass substrate of the ITO electrode, and keeps the electrolyte circulating between the workpiece and the electrode.

After the electrochemical machining power supply is energized, the surface processing area of the workpiece is removed under the combined action of cavitation and electrochemical reaction caused by laser irradiation, and the photoelectrochemical reaction of the workpiece material is removed, realizing three-dimensional etching processing. The pulse frequency of the processing power supply is 1kHz-10kHz, and the voltage amplitude is 5V. Under the adjustment of the grayscale pattern of the liquid crystal mask, the area with high laser energy has a fast electrochemical reaction and a large amount of workpiece material ablation; the area with low energy has a slow electrochemical reaction speed and a small ablation amount of workpiece material. It can process three-dimensional shapes with different depths in various parts, so as to realize three-dimensional graphics processing of liquid crystal masks based on photoelectrochemical reactions. Figure 2 is an example of the processed elliptical three-dimensional pit. It can be seen that the processing depth gradually changes along the direction of the long axis of the ellipse.

The control part mainly completes the command control of the graphic display of the liquid crystal mask, the motion control of the workbench and the switch control of the electrochemical processing power supply. For graphics with larger dimensions, it can be processed multiple times with larger-diameter spots processed by the beam expander system, or it can be processed by small-diameter and high-energy laser beams in partitions. By controlling the movement of the worktable, it can be processed one by one. , the processed graphics are clear in shape and have three-dimensional features.

Claims (7)

1. the Photoelectrochemicalthree three-dimensional processing method of a laser bubble cavitation, the Optical Electro-Chemistry reaction that utilizes laser to cause at electrode surface irradiation realizes the removal processing of workpiece material, it is characterized in that: the laser beam that laser instrument sent is by seeing through solution irradiation when metal works is surperficial behind the mask plate, cause the solution optical breakdown to produce bubble, the crumble and fall pulse shock effect and the electrochemical reaction that form bubble cavitation of bubble is compound, make workpiece material under the Optical Electro-Chemistry reagentia, be removed, realize etching processing.

2. the Photoelectrochemicalthree three-dimensional processing method of a kind of laser bubble cavitation according to claim 1; it is characterized in that: the optical maser wavelength that laser instrument sent is 1064 nanometers; burst length was 5 nanoseconds, and laser energy is 0.1～erg-ten, and facular model is basic mode or multimode.

3. the Photoelectrochemicalthree three-dimensional processing method of a kind of laser bubble cavitation according to claim 1, it is characterized in that: mask plate adopts can be by the liquid crystal display of computer control gray scale figure demonstration, can utilize in the figure each regional gray scale difference to the difference of laser transmittance, realize spatial modulation the laser facula energy distribution; The high zone of laser irradiation energy on the workpiece, the bubble cavitation effect is strong, and the Optical Electro-Chemistry reaction speed is fast, and the ablation amount is big; The zone that energy is low, a little less than the bubble cavitation effect, the Optical Electro-Chemistry reaction speed is slow, and the ablation amount is little, thereby realizes Photoelectrochemicalthree three-dimensional processing.

4. the Photoelectrochemicalthree three-dimensional processing method of a kind of laser bubble cavitation according to claim 3, used liquid crystal mask is characterised in that: the figure that the liquid crystal display mask shows can be controlled with computer, when the figure of required processing changes, needn't make mask plate in addition, only need to revise the control instruction of computer, just can change mask graph fast, realize the Optical Electro-Chemistry Compound Machining of various complex figures.

5. the Photoelectrochemicalthree three-dimensional processing unit (plant) of a laser bubble cavitation is graded with test section and control part and is formed by laser instrument (1), transmission light path, Compound Machining.It is characterized in that transmitting light path comprises: beam-expanding system (3), liquid crystal mask (4), focusing system (5) and ITO conductive glass electrode (6); Compound Machining and test section are made up of ITO conductive glass electrode (6), workpiece (8), the processing cavity (9) that charges into electrolyte, workbench (10), voltmeter (11), ammeter (12) and processing power source (13).

6. the Photoelectrochemicalthree three-dimensional processing unit (plant) of a kind of laser bubble cavitation according to claim 5, it is characterized in that: intercouple as laser energy and electrochemical action with the ITO electro-conductive glass, realize the critical component of Optical Electro-Chemistry reaction, this electrode forms in electrolyte in the electric field, can also see through to have the high energy laser beam of mask graph.

7. according to the Photoelectrochemicalthree three-dimensional processing unit (plant) of claim 5 or 6 described a kind of laser bubble cavitations, it is characterized in that: greater than 85%, resistivity is 1～5 * 10 to the ITO electro-conductive glass to the transmitance of laser ^-4Ω/cm; The NaNO of the solution service property (quality) concentration 10%～15% of Optical Electro-Chemistry reaction ₃Electrolyte, the pulse frequency of processing power source are 1kHz～10kHz, and voltage magnitude is 5V.

Images