Ultrasonic cavitation and plasma coupling regulation and control liquid auxiliary laser processing device

Abstract

An ultrasonic cavitation and plasma coupling regulation and control liquid auxiliary laser processing device comprises an ultrasonic generator, a laser, a corrugated pipe and a liquid container, the output end of the laser is connected to a collimating mirror through an optical fiber, and the ultrasonic generator transmits an electric signal to an ultrasonic transducer in a working head to convert the electric signal into ultrasonic vibration; the working head comprises a collimating lens, an ultrasonic transducer, an amplitude-change pole, a focusing lens and a corrugated pipe, the working head is fixed on a machine tool spindle through a flange at the section surface of the amplitude-change pole and a bolt, the two ends of the ultrasonic transducer are connected with the collimating lens and the amplitude-change pole respectively, the focusing lens is fixed in the amplitude-change pole through a double-check ring, and the corrugated pipe is connected with the ultrasonic transducer. The other end of the amplitude-change pole is connected with the corrugated pipe, the corrugated pipe is completely immersed in liquid, high-speed directional fluid is formed in the liquid through ultrasonic vibration, cavitation bubbles are effectively reduced, coupling regulation and control are conducted on plasma generated in the laser machining process, shock waves generated by fluid flowing eliminate the shielding effect of the plasma on laser, and the machining quality is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultrasonic vibration composite laser processing devices, and particularly relates to an ultrasonic cavitation and plasma coupling regulated liquid-assisted laser processing device. Background Art

[0002] Laser processing technology is a high-tech that processes materials such as cutting, welding, drilling, and engraving based on the high energy density characteristics of a laser beam. Compared with traditional mechanical processing methods, laser processing technology has the advantages of high precision, high efficiency, high quality, and pollution-free, and has become an important development direction in the field of modern industrial manufacturing. With the continuous development of laser technology, laser processing technology has been widely applied in various fields such as aerospace, automotive manufacturing, electronic information, and medical devices, and has become an indispensable part of modern industrial manufacturing. In recent years, with the continuous innovation and upgrading of laser technology, laser processing technology has also been continuously developed and improved. For example, the power and stability of the laser beam have been significantly improved, and the automation and intelligence levels of laser processing equipment have also been continuously improved. In addition, the combination of laser processing technology with other advanced technologies, such as machine vision and robotics, has further expanded the application fields and processing capabilities of laser processing technology.

[0003] Although laser processing technology has made significant progress, there are still some technical problems and challenges. Since the basic principle of laser processing technology is to use the high energy density of a laser beam to heat, melt, or vaporize materials instantaneously in a local area, thereby realizing processing such as cutting and welding of materials, however, the severe thermal effect causes obvious heat-affected zones and recast layers on the surface of the workpiece to be processed, thus making it impossible to achieve higher-precision surface quality of the processed workpiece. Therefore, by placing the workpiece in a liquid with good specific heat capacity, the heat generated on the surface of the workpiece during the laser processing can be effectively absorbed. At the same time, since the processing process is in the liquid, the influence of various gases on the processing can be isolated, thereby effectively reducing the surface roughness, obtaining a relatively smooth workpiece surface, and improving the processing quality. However, new problems are also introduced, that is, when the laser induces optical breakdown of the liquid, the resulting action process includes three aspects: the generation of plasma, the radiation of shock waves, and the cavitation phenomenon of bubbles. When a high-energy pulsed laser breaks down the liquid, a high-temperature and high-pressure plasma is generated in the processing area. The plasma expands outward and generates shock waves. At the same time, bubbles are generated, which will directly affect the refraction of the laser and cause energy loss. When the bubbles burst, the generated water jet will disturb the liquid flow, further agitating the debris generated during the processing process, thereby affecting the direct irradiation of the laser onto the workpiece and damaging the surface quality. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides an ultrasonic cavitation and plasma coupling-regulated liquid-assisted laser processing device, aiming to improve the efficiency and quality of laser processing. On the basis of the original liquid-assisted laser processing device, ultrasonic vibration is coupled with laser processing, and a corrugated pipe is installed at the front end of the horn. The corrugated pipe is completely immersed in the liquid. Under the action of ultrasonic vibration, the turbulence intensity in the corrugated pipe is relatively high, which is not conducive to ultrasonic cavitation. In addition, each section of the corrugated pipe type is composed of the fitting of two sine function curves, and the diameter of the corrugated pipe changes alternately. The sound pressure therein increases and weakens periodically in a relatively short section of the pipe. When the expansion phase of the sound pressure is inconsistent with the decrease in the pipe diameter, it is not conducive to the formation of the cavitation effect, and the subsequent compression phase and the pressure increase of the pipe itself will force the elimination of a large number of cavitation bubbles. When the bubbles dissipate and collapse, ultrasonic shock waves are generated. Due to the constraint of the pipe, a high-speed directional fluid will be formed in the liquid in the radial direction of the corrugated pipe. At the same time, the semi-closed structure on the front end face of the corrugated pipe continuously promotes the liquid flow under the condition of ultrasonic vibration. Under the coupling impact of the two aspects, the cavitation bubbles can be effectively reduced. Moreover, the impact generated by the fluid flow will also eliminate the shielding effect of the plasma on the laser, thereby further improving the surface quality of the laser-processed workpiece.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An ultrasonic cavitation and plasma coupling-regulated liquid-assisted laser processing device, comprising an ultrasonic generator, a laser, a corrugated pipe and a liquid container. The output end of the laser is connected to a collimating mirror through an optical fiber. The ultrasonic generator transmits an electrical signal to the ultrasonic transducer in the working head to be converted into ultrasonic vibration. The working head includes a collimating mirror, an ultrasonic transducer, a horn, a focusing lens and a corrugated pipe. The working head is fixed on the machine tool spindle by bolts through the flange at the nodal plane of the horn. The two ends of the ultrasonic transducer are respectively connected to the collimating mirror and the horn. The focusing lens is fixed inside the horn through double snap rings. The other end of the horn is connected to the corrugated pipe, and the corrugated pipe is completely immersed in the liquid.

[0007] The ultrasonic transducer mainly consists of a front cover plate, a rear cover plate, 4 piezoelectric ceramic sheets and 6 copper electrode sheets. The piezoelectric ceramic sheets are placed between the front and rear cover plates. The copper electrode sheets are fixed in the middle of the piezoelectric ceramic sheets and filled with epoxy resin. A wiring port is fixed at the end of the copper electrode sheet. The input end of the ultrasonic transducer is connected to the input end of the ultrasonic generator through a wire through the wiring port.

[0008] A through hole is machined in the center of the ultrasonic transducer, and the laser can pass through the center. The piezoelectric ceramic sheets and the copper electrode sheets are both circular rings, and the through hole sizes of the front and rear cover plates are determined according to the diameter of the laser beam.

[0009] A through hole is provided in the middle of the horn, and the laser can irradiate the focusing lens through the through hole. The horn is fixed on the flange through the nodal plane flange, and the flange is connected to the machine tool spindle through bolts. The horn is a second-order Fourier horn. Under the condition of the same resonance frequency and area coefficient, the amplitude amplification coefficient of the second-order Fourier horn is much larger than the corresponding values of the exponential, catenary, and conical horns.

[0010] The tube shape of the bellows, each section of the bellows shape is composed of two sections of sine function curves fitting, and the corrugated pipe diameter changes alternately. The front end face of the bellows is semi-closed, and the laser can pass through the central through hole and irradiate the surface of the workpiece to be processed.

[0011] An ultrasonic cavitation and plasma coupling regulation liquid-assisted laser processing device described includes the following steps:

[0012] Step 1, start the laser, and the generated laser is transmitted through the optical fiber into the laser collimator, passes through the ultrasonic transducer and the horn, is incident on the focusing lens, and then is focused on the workpiece surface through the bellows; at the same time, the ultrasonic generator generates an alternating current signal, which is transmitted to the ultrasonic transducer and converted into mechanical vibration. After the amplitude is increased by the horn, the ultrasonic vibration is transmitted to the bellows. With the assistance of the liquid environment, the bottom of the bellows in ultrasonic vibration pushes the liquid to form a high-speed directional fluid, which inhibits the plasma formed on the workpiece surface. The side structure of the bellows will eliminate the cavitation bubbles formed by the ultrasonic vibration and promote the collapse of the cavitation bubbles formed during the laser processing. Eliminate the influence of plasma, cavitation bubbles, impurity particles, etc. on the laser processing and improve the laser processing quality of the workpiece.

[0013] The beneficial effects of the present invention are as follows:

[0014] 1. On the basis of the original liquid-assisted laser processing device, the present invention couples the ultrasonic vibration composite processing technology. When the workpiece is immersed in the liquid for laser processing, the good specific heat capacity of the liquid can absorb the excess heat generated during the processing, thereby effectively reducing the heat-affected zone on the workpiece surface and reducing the surface roughness of the workpiece to be processed.

[0015] 2. The bellows is completely immersed in the liquid. Under the action of ultrasonic vibration, its special geometric structure has an obvious influence on the propagation characteristics of ultrasonic waves in the tube. The new bellows structure promotes a significant increase in the turbulent intensity in the tube, forming a stable high-speed directional fluid, thereby inhibiting the ultrasonic cavitation effect, reducing cavitation bubbles, and improving the processing quality.

[0016] 3. Under the condition of liquid-assisted laser processing, the plasma generated when the laser induces optical breakdown of the liquid will weaken the energy density incident on the workpiece surface. The stable flowing fluid generated under the action of the ultrasonic vibration bellows can disperse the plasma generated during the laser processing, realize the regulation of the plasma, and eliminate the shielding effect of the plasma on the laser processing.

[0017] 4. The structure of the invention of this patent is simple, the cost is relatively low, the implementation effect is good, it is convenient to realize large-scale production, and it can be promoted to industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a three-dimensional structural schematic diagram of the liquid-assisted laser processing device for ultrasonic cavitation and plasma coupling regulation of the present invention;

[0019] Figure 2 is a half-sectional view of the working head;

[0020] Figure 3 is a half-sectional view of the bellows;

[0021] Figure 4 is a comparison diagram of the processing effects of ordinary liquid-assisted laser processing and liquid-assisted laser processing regulated by ultrasonic vibration bellows.

[0022] 1 - Ultrasonic generator, 2 - Laser, 3 - Collimating mirror, 4 - Ultrasonic transducer, 5 - Amplitude transformer, 6 - Focusing lens mechanism, 7 - Bellows, 8 - Machine tool, 9 - Retaining ring, 10 - Focusing lens, 11 - Front cover plate, 12 - Rear cover plate, 13 - Piezoelectric ceramic, 14 - Copper electrode plate, 15 - Working head, 16 - Liquid container. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0024] As Figures 1-4 shown, a liquid-assisted laser processing device for ultrasonic cavitation and plasma coupling regulation includes an ultrasonic generator 1, a laser 2, a bellows 7 and a liquid container 16. The output end of the laser 2 is connected to a collimating mirror 3 through an optical fiber. The ultrasonic generator 1 transmits an electrical signal to the ultrasonic transducer 4 in the working head 15 to be converted into ultrasonic vibration. The working head includes a collimating mirror 3, an ultrasonic transducer 4, an amplitude transformer 5, a focusing lens 10 and a bellows 7. The working head is fixed on the main shaft of the machine tool by bolts through the flange at the nodal plane of the amplitude transformer. The two ends of the ultrasonic transducer 4 are respectively connected to the collimating mirror 3 and the amplitude transformer 5. The focusing lens 10 is fixed inside the amplitude transformer 5 by double retaining rings 9. The other end of the amplitude transformer 5 is connected to the bellows 7, and the bellows 7 is completely immersed in the liquid.

[0025] Among them Figure 3It is a half-sectional view of the bellows 7 of the ultrasonic vibration laser working head. The bus bar of each section of the bellows 7 is fitted by two sections of sine curves, presenting a corrugated curve as a whole. The front end face of the bellows 7 is semi-closed, and the laser can irradiate the surface of the workpiece to be processed through the central through hole. Figure 4 (a) shows the effect of ordinary liquid-assisted laser processing. When the high-energy pulsed laser breaks through the liquid, high-temperature and high-pressure plasma is generated in the processing area. The plasma expands outward and generates shock waves. At the same time, bubbles are generated, which will directly affect the refraction of the laser and cause energy loss. When the bubbles burst, the generated water jet will disturb the liquid flow and further stir the debris generated during the processing, thus hindering the direct irradiation of the laser onto the workpiece and affecting the surface quality of laser processing. In Figure 4 (b), according to the laws of thermodynamics, when the fluid flows in a changing space, the pressure will change with the size of the space. After introducing ultrasonic vibration, the sound pressure weakens when the pipe diameter becomes smaller, and the change in the internal structure of the pipe forms local cavities, enabling the generation of vaporization nuclei and gradually forming cavitation bubbles. As the pipe diameter increases, the sound pressure gradually returns to its original state, and the generated bubbles will be compressed and collapsed in large numbers, thereby forming a stable directional fluid. At the same time, due to the semi-closed structure of the bellows 7, the front end face of the bellows 7 simultaneously promotes the liquid flow under ultrasonic vibration and impacts the plasma and bubbles generated during the laser processing, reducing the shielding effect of the plasma on the laser and weakening the damage of the bubbles to the surface topography of the workpiece, improving the overall quality of laser processing.

[0026] The ultrasonic transducer 4 mainly consists of a front cover plate 11, a rear cover plate 12, a piezoelectric ceramic sheet 13, and a copper electrode sheet 14. The piezoelectric ceramic sheet 13 is placed between the front cover plate 11 and the rear cover plate 12. The copper electrode sheet 14 is fixed in the middle of the piezoelectric ceramic sheet 13 and filled with epoxy resin. A wiring port is fixed at the end of the copper electrode sheet 14. The input end of the ultrasonic transducer 4 is connected to the input end of the ultrasonic generator 1 through the wiring port with a wire.

[0027] A through hole is machined in the center of the ultrasonic transducer 4, and the laser can pass through the center. Among them, the piezoelectric ceramic sheet 13 and the copper electrode sheet 14 are both circular rings, and the through hole sizes of the front cover plate 11 and the rear cover plate 12 are determined according to the laser beam diameter.

[0028] A through hole is provided in the middle of the horn 5, and the laser can be emitted from the through hole to the focusing lens 10. The horn 5 is fixed on the flange through a nodal plane flange, and the flange is connected to the spindle of the machine tool 8 through bolts. The horn 5 is a second-order Fourier horn. Under the condition of the same resonant frequency and area coefficient, the amplitude amplification coefficient of the second-order Fourier horn is much larger than the corresponding values of the exponential type, catenary type, and conical type.

[0029] The tube shape of the corrugated tube 7 is such that each corrugated section of the corrugated tube is formed by fitting two sections of a sine function curve, and the corrugated tube diameter alternates. The front end face of the corrugated tube 7 is semi-closed, and the laser can be emitted from the central through-hole towards the surface of the workpiece to be processed.

[0030] The described ultrasonic cavitation and plasma coupling regulated liquid-assisted laser processing device comprises the following steps:

[0031] Step 1: Start the laser 2. The generated laser is transmitted through the optical fiber into the laser collimating mirror 3, passes through the ultrasonic transducer 4 and the horn 5, is incident on the focusing lens 10, and then passes through the corrugated tube 7 and is focused on the surface of the workpiece. At the same time, the ultrasonic generator 1 generates an alternating electric signal, which is transmitted to the ultrasonic transducer 4 and converted into mechanical vibration. After the amplitude is amplified by the horn 5, the ultrasonic vibration is transmitted to the corrugated tube 7 and reaches the maximum amplitude. Furthermore, the ultrasonic vibration of the corrugated tube 7 pushes the liquid to form a high-speed directional fluid. The focus of the laser beam is focused on the surface of the workpiece in the liquid, and with the assistance of the liquid environment, the workpiece processing is completed.

Claims

1. An ultrasonic cavitation and plasma coupling regulation liquid-assisted laser processing device, comprising an ultrasonic generator, a laser, a corrugated pipe and a liquid container. The output end of the laser is connected to a collimating mirror through an optical fiber. The ultrasonic generator transmits an electrical signal to an ultrasonic transducer in the working head to be converted into ultrasonic vibration. The working head includes a collimating mirror, an ultrasonic transducer, a horn, a focusing lens and a corrugated pipe. The working head is fixed on the spindle of the machine tool by bolts through a flange at the nodal plane of the horn. The two ends of the ultrasonic transducer are respectively connected to the collimating mirror and the horn. The focusing lens is fixed inside the horn by a double snap ring. The other end of the horn is connected to the corrugated pipe, and the corrugated pipe is completely immersed in the liquid.

2. The liquid-assisted laser processing device with ultrasonic cavitation and plasma coupling regulation according to claim 1, wherein The ultrasonic transducer mainly consists of a front cover plate, a rear cover plate, 4 piezoelectric ceramic sheets and 6 copper electrode sheets. The piezoelectric ceramic sheets are placed between the front and rear cover plates, and the copper electrode sheets are placed in the middle of the piezoelectric ceramic sheets and filled with epoxy resin.

3. The liquid-assisted laser processing device with coupled regulation of ultrasonic cavitation and plasma according to claim 1, characterized in that A through hole is machined in the center of the ultrasonic transducer, and the laser can pass through the center. Both the piezoelectric ceramic sheets and the copper electrode sheets are circular rings, and the through hole sizes of the front and rear cover plates are determined according to the diameter of the laser beam.

4. The liquid-assisted laser processing device with ultrasonic cavitation and plasma coupling regulation according to claim 1, characterized in that A through hole is provided in the middle of the horn, and the laser can irradiate the focusing lens through the through hole. The horn is fixed on the flange plate through a nodal plane flange, and the flange plate is connected to the machine tool by bolts. The horn is a second-order Fourier horn. Under the condition of the same resonance frequency and area coefficient, the amplitude amplification coefficient of the second-order Fourier horn is much larger than the corresponding values of the exponential type, catenary type and conical type.

5. The liquid-assisted laser processing device with ultrasonic cavitation and plasma coupling regulation according to claim 1, characterized in that The pipe type of the corrugated pipe, each section of the corrugated pipe type is composed of the fitting of two sine function curves, and the corrugated pipe diameter changes alternately. The front end face of the corrugated pipe is semi-closed, and the laser can pass through the central through hole and irradiate the surface of the workpiece to be processed.

6. A method for using an ultrasonic cavitation and plasma coupling regulation liquid-assisted laser processing device, which uses an ultrasonic cavitation and plasma coupling regulation liquid-assisted laser processing device as described in claim 1, characterized in that, Including the following steps: Step 1, start the laser. The generated laser is transmitted to the laser collimating mirror through the optical fiber, passes through the ultrasonic transducer and the horn, is incident on the focusing lens, and then is focused on the surface of the workpiece through the corrugated pipe. At the same time, the ultrasonic generator generates an alternating electrical signal, which is transmitted to the ultrasonic transducer and converted into mechanical vibration. After the amplitude is increased by the horn, the ultrasonic vibration is transmitted to the corrugated pipe. With the assistance of the liquid environment, the bottom of the corrugated pipe in ultrasonic vibration pushes the liquid to form a high-speed directional fluid, which inhibits the plasma formed on the surface of the workpiece by the laser. The side structure of the corrugated pipe will eliminate the cavitation bubbles formed by the ultrasonic vibration and promote the collapse of the cavitation bubbles formed during the laser processing. Eliminate the influence of plasma, cavitation bubbles, impurity particles, etc. on the laser processing and improve the laser processing quality of the workpiece.

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