WO2016066005A1 - 激光加工头及其应用、激光加工系统及方法 - Google Patents

激光加工头及其应用、激光加工系统及方法 Download PDF

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Publication number
WO2016066005A1
WO2016066005A1 PCT/CN2015/091204 CN2015091204W WO2016066005A1 WO 2016066005 A1 WO2016066005 A1 WO 2016066005A1 CN 2015091204 W CN2015091204 W CN 2015091204W WO 2016066005 A1 WO2016066005 A1 WO 2016066005A1
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Prior art keywords
laser
laser processing
stage nozzle
fluid
processing head
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PCT/CN2015/091204
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English (en)
French (fr)
Inventor
张文武
张天润
郭春海
杨旸
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中国科学院宁波材料技术与工程研究所
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Priority to JP2017522805A priority Critical patent/JP6503063B2/ja
Priority to EP15854454.4A priority patent/EP3213858B1/en
Priority to US15/523,229 priority patent/US11219968B2/en
Publication of WO2016066005A1 publication Critical patent/WO2016066005A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • B23K26/0648—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising lenses
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
    • B23K26/1462—Nozzles; Features related to nozzles
    • B23K26/1464—Supply to, or discharge from, nozzles of media, e.g. gas, powder, wire
    • B23K26/1476—Features inside the nozzle for feeding the fluid stream through the nozzle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
    • B23K26/146—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor the fluid stream containing a liquid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/14—Working by laser beam, e.g. welding, cutting or boring using a fluid stream, e.g. a jet of gas, in conjunction with the laser beam; Nozzles therefor
    • B23K26/1462—Nozzles; Features related to nozzles
    • B23K26/1464—Supply to, or discharge from, nozzles of media, e.g. gas, powder, wire
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • B23K26/382—Removing material by boring or cutting by boring
    • B23K26/389—Removing material by boring or cutting by boring of fluid openings, e.g. nozzles, jets

Definitions

  • the invention relates to the field of laser processing technology, in particular to a laser processing head for high energy laser processing and an application thereof, a laser processing system and a method.
  • High-energy lasers such as multi-kilowatt continuous-wave fiber lasers, carbon dioxide lasers, solid-state lasers, and pulsed high-power lasers
  • the laser When the laser is removed, when the pulse width is large (>10 picoseconds), the removal mechanism is generally coexisting with melting and sublimation. With the help of auxiliary gas, the material is removed from the substrate, and a large amount of heat is generated in the process. , thus affecting the machining of the workpiece. In many cases, such as when processing heat sensitive materials and metal drilling, the effect of heat on the workpiece is minimized.
  • auxiliary fluids such as water streams
  • the laser is coupled into the water stream to combine the water cooling and laser processing effects, both laser-based, material removal, and heat-affected zone limitation by water flow cooling.
  • SYNOVA in Europe invented the micro-jet laser processing system, which forms a fine water jet through the high-pressure chamber and the gem nozzle, and then concentrates the laser into the gem nozzle.
  • the pulsed laser follows a water jet with a diameter of less than 100 ⁇ m.
  • the shot emits a natural light-guide effect in the air (long-distance low-loss transmission by total reflection), and the water jet coupled with the pulsed laser energy can be processed with a nanosecond pulsed laser with minimal thermal influence.
  • the above idea relies on the light guiding effect of the water jet in the air. In theory, once the layered water flow and the air interface are lost, the light guiding effect is no longer present. Therefore, the above water assisted laser processing method is difficult to achieve a large depth (>10 mm). Processing.
  • the hollow tube is made of a special polymer Teflon with a melting point below 400 °C.
  • the light guide system can achieve energy requirements in many laser processing by nanosecond green light with an energy exceeding 4 GW/cm 2 .
  • the hollow tube can be laser processed deep into the water, and in principle can be drilled into the material to realize laser removal processing without depth limitation.
  • the above two laser processing systems and other existing water-assisted laser processing systems all face a technical problem: on the one hand, in order to generate micro-jets, the inner diameter of the nozzle/hollow tube needs to be made small to enhance coupling. The energy density of the post-laser; on the other hand, the damage caused by the laser to the hollow tube at the narrow entrance is strictly avoided.
  • SYNOVA's microfluidic laser processing system as an example, although the system works well when the system is working normally, its reliability is difficult to improve due to the vulnerability of the nozzle.
  • “the vulnerability of the nozzle” is due to the possibility of drift of the spot position during use of the system.
  • the expensive gem nozzle may be directly destroyed; in addition, even if there is no The spot drifts, when there are impurity particles passing through the narrow nozzle portion, the impurity particles are sublimated, generating a high-temperature plasma, corroding the entrance port, thereby causing damage to the nozzle.
  • the current water-assisted laser processing system has a low applicable power.
  • the contradiction between the high energy density coupling of the laser and the system reliability has become an urgent problem to be solved.
  • the invention provides a laser processing head and an application thereof, a laser processing system and a method, and effectively solves the contradiction between the high energy density coupling of the laser and the system reliability in the laser processing process.
  • a laser processing head for transmitting laser light to a workpiece to be processed including:
  • a second stage nozzle disposed in a downstream direction of the first stage nozzle and in communication with the first stage nozzle;
  • the inner diameter of the second stage nozzle gradually decreases along the transmission direction of the laser, and the minimum inner diameter of the first stage nozzle is larger than the inner diameter of the end of the second stage nozzle.
  • the laser processing head further includes a focusing lens disposed in an upward direction of the first stage nozzle.
  • the laser processing head further includes a transparent window disposed in an upward direction of the focus lens.
  • the minimum inner diameter of the first stage nozzle is greater than twice the diameter of the spot after the laser focusing; the inner diameter of the second stage nozzle is smaller than the minimum inner diameter of the first stage nozzle. /2.
  • the second stage nozzle is integrally formed with the first stage nozzle.
  • the first stage nozzle and the second stage nozzle are both metal tubes, glass tubes, ceramic tubes or plastic tubes with smooth inner walls.
  • the laser processing head further includes a first cavity and a second cavity
  • the first cavity is in communication with the first stage nozzle, and the second cavity is in communication with the second stage nozzle.
  • the first cavity is disposed in an upward direction of the first stage nozzle
  • the outer side wall of the first stage nozzle is a curved structure whose diameter gradually decreases, the larger inner diameter portion of the second stage nozzle is disposed outside the first stage nozzle, and the second cavity is disposed at the first stage nozzle Between the outer sidewall and the inner sidewall of the second stage nozzle.
  • a laser processing system comprising:
  • the laser processing head for transmitting the laser to a workpiece to be processed
  • a first supply unit for supplying a first pressure of a certain pressure to the laser processing head, and a second supply unit for providing a certain pressure to the laser processing head Second fluid;
  • control unit for controlling actions of the first supply unit, the second supply unit, and the laser.
  • the refractive index of the first fluid to light is greater than the refractive index of the second fluid to light.
  • the first fluid is a liquid and the second fluid is a gas.
  • the first stage nozzle of the laser processing head has a refractive index to light that is less than a refractive index of the first fluid to light.
  • the laser processing system further includes an optical unit disposed between the laser and the laser processing head.
  • a laser processing method comprising the following steps:
  • the first fluid coupled with the laser flows into the second stage nozzle, and is wrapped by the second fluid in the second stage nozzle;
  • the laser jet acts on the workpiece to be processed for laser processing.
  • the first fluid is a liquid and the second fluid is a gas.
  • the refractive index of the first fluid to light is greater than the refractive index of the second fluid to light.
  • the minimum inner diameter of the first stage nozzle is greater than twice the diameter of the spot after the laser is focused
  • the inner diameter of the second stage nozzle is less than 1/2 of the minimum inner diameter of the first stage nozzle.
  • the diameter of the laser jet passes through the pressure of the first fluid and the second fluid Force to adjust.
  • the laser processing head and the application thereof, the laser processing system and the method provided by the invention solve the contradiction between the high energy density laser and the system reliability by means of step coupling.
  • the laser is first coupled into the first fluid of the first stage nozzle. Since the diameter of the first stage nozzle is larger, the coupling difficulty of the laser is reduced, and the drift of the laser spot or the corrosion of the impurity particles is avoided.
  • the damage caused by the laser processing head increases the reliability of the system; then the diameter of the first fluid is gradually reduced by external constraints, so that the laser jet is finally formed, and the coupling of the first fluid decreases in diameter.
  • the beam of laser light into the first fluid will also gradually shrink, and the energy density of the laser will gradually increase, eventually outputting a high-energy laser beam; this way of outputting laser energy can break through the resolution of conventional laser focusing by producing a very fine laser jet.
  • Limit up to 5 microns or even sub-micron, while maintaining a processing depth that is much greater than the length of the end water flow diameter; finally, due to increased reliability, water-assisted laser processing of kilowatt lasers is possible, compared to current water-assisted lasers Processing greatly increases the processing speed.
  • FIG. 1 is a schematic structural view of an embodiment of a laser processing head according to the present invention.
  • FIG. 2 is a schematic structural view showing an embodiment of processing a laser processing head deep into a workpiece according to the present invention
  • FIG. 3 is a schematic structural view of an embodiment of a laser processing head of the present invention deep into a fluid for processing;
  • FIG. 4 is a schematic view showing the function of an embodiment of a laser processing system according to the present invention.
  • Figure 5 is a screenshot of the fluid constraint simulation.
  • the present invention defines that the transmission direction of the laser is the downward direction, and vice versa.
  • the invention provides a laser processing head for transmitting laser light emitted by a laser to a workpiece to be processed, in particular for transmission of a high energy laser.
  • the laser processing head 100 of the present invention includes a first stage nozzle 110 and a second stage nozzle 120 that are in communication with each other, wherein the second stage nozzle 120 is located in the downstream direction of the first stage nozzle 110, that is, the laser light emitted by the laser
  • the first stage nozzle 110 is entered and the second stage nozzle 120 is entered.
  • the direction indicated by the arrow in the figure is the direction of laser light transmission.
  • the inner diameter of the second stage nozzle 120 gradually decreases along the direction of laser light transmission, and the minimum inner diameter of the first stage nozzle 110 is larger than the inner diameter of the end of the second stage nozzle 120 (the exit end of the laser).
  • the first stage nozzle 110 may have an equal inner diameter structure or a variable inner diameter structure.
  • the first stage nozzles 110 have an equal inner diameter structure, that is, the inner diameters are equal, and at this time, the minimum inner diameter is the inner diameter thereof.
  • the design of the inner diameter facilitates the initial coupling of the laser, which can effectively avoid the loss caused by the laser during the initial coupling process.
  • a first pressure of a certain pressure is introduced into the first stage nozzle 110, and a second fluid of a certain pressure is introduced into the second stage nozzle 120; wherein the first fluid is used for coupling into the first stage nozzle
  • the laser of 110, the second fluid is used to wrap the first fluid to which the laser is coupled.
  • the laser When laser processing is performed, the laser is first coupled into the first fluid; then, the laser coupled to the first fluid enters the second stage nozzle 120 with the first fluid, and in the second stage nozzle 120, the second fluid is coupled
  • the first fluid having the laser is enclosed, since the inner diameter of the second stage nozzle 120 is gradually decreased along the transmission direction of the laser, and at the same time, the second fluid has a certain pressure, and therefore, the diameter of the first fluid coupled with the laser is
  • the second stage nozzle 120 and the second fluid are gradually reduced under the double constraint, the laser spot is gradually reduced, the energy density (laser intensity) of the laser is gradually increased, and the first fluid coupled with the laser is finally in the second.
  • a laser jet formed under the envelopment of the fluid is ejected from the end of the second stage nozzle 120 to act on the workpiece to be processed to achieve high energy laser processing.
  • the laser processing head 100 of the present invention solves the contradiction between high energy laser density and system reliability by means of stepwise coupling. Since the minimum inner diameter of the first stage nozzle 110 is larger than the inner diameter of the end of the second stage nozzle 120, the first fluid has a relatively large inner diameter, and when laser coupling is performed, a larger laser spot can be used, reducing the initiality.
  • the energy density of the laser during coupling reduces the risk of laser damage to the first stage nozzle 110, improves the coupling efficiency of the laser and the reliability of the system, and the first stage nozzle 110 can be made of a low cost and high temperature resistant material.
  • a quartz tube greatly reduces the cost compared to a gemstone nozzle; at the same time, since the diameter of the first fluid is gradually reduced by using a second fluid constraint instead of a solid direct constraint, it is effectively prevented in a region where the laser intensity is increased.
  • the direct contact between the laser and the second stage nozzle 120 further increases the reliability of the system, and can be used for ultra-high power continuous wave laser (above 1000 W) or high average power pulse laser (nanosecond, picosecond, femtosecond over 100 watts).
  • the energy of the laser is coupled into a very fine terminal laser jet, giving the laser a high removal speed and high processing quality.
  • the inner diameter of the tip end of the first stage nozzle 110 is less than or equal to the inner diameter of the initial end of the second stage nozzle 120. This approach helps the second fluid to form a wrap around the first fluid and is effective in avoiding turbulence.
  • the magnitude of the final diameter of the first fluid (the diameter when ejected from the end of the second stage nozzle 120) can be adjusted by adjusting the pressure of the first fluid and the second fluid, or by changing the second stage nozzle 120.
  • the size of the end diameter is adjusted. The basic requirement is to ensure that the first fluid coupled with the laser is laminar and avoid turbulence, so that the laser can be smoothly transmitted.
  • the final diameter of the first fluid is related to the input laser power and the desired laser intensity.
  • the laser intensity required to achieve 2 or more 500MW / cm generally required final diameter 100 ⁇ m or less; 1000W for continuous wave laser in terms of, if needed to reach 5MW / cm 2 or more
  • the final diameter needs to be less than 150 ⁇ m.
  • the laser processing head 100 of the present invention further includes a focus lens 130.
  • the focus lens 130 is disposed in the upward direction of the first stage nozzle 110, that is, the laser light emitted by the laser passes through the focus of the focus lens 130 and then enters the first stage nozzle 110.
  • the focusing lens 130 can function as a converging beam, focusing the energy of the laser into a spot that can be more easily coupled into the first fluid, reducing the energy loss of the laser during transmission and coupling.
  • the focal length and the specific setting position of the focusing lens 130 can be selected according to actual needs.
  • the light guiding structure is not used in the first stage nozzle 110 (ie, the refractive index of the first fluid to the light is less than or equal to the light of the first stage nozzle 110)
  • the focus of the laser can be focused below the exit of the first stage nozzle 110 to reduce the energy loss of the laser;
  • the light guide structure is used in the first stage nozzle 110 (ie, the refractive index of the first fluid to the light is greater than
  • the focus point of the laser may be located at any position of the first stage nozzle 110.
  • the laser processing head 100 described above further includes a transparent window 140.
  • the transparent window 140 is disposed in the upward direction of the focus lens 130 for protecting the focus lens 130, preventing the focus lens 130 from being contaminated and affecting the focusing effect.
  • the transparent window 140 is made of quartz glass.
  • the minimum inner diameter of the first stage nozzle 110 is greater than twice the diameter of the spot after laser focusing, preferably 0.25 mm to 0.75 mm.
  • the minimum inner diameter of the second stage nozzle 120 ie, the inner diameter of the end of the second stage nozzle 120
  • 1/2 of the minimum inner diameter of the first stage nozzle 110 preferably 5 [mu]m - 100 ⁇ m, can be smaller when needed, reaching sub-micron level.
  • the first stage nozzle 110 may use a metal tube, a ceramic tube or a glass tube with a smooth inner wall, and a plastic tube may be used under the premise of satisfying long-term stability.
  • the metal tube includes a stainless steel tube, a copper tube, etc.
  • the glass tube includes a quartz tube or the like.
  • the second stage nozzle 120 can also be the tube described above.
  • the laser processing head 100 described above further includes a first cavity 150 and a second cavity 160.
  • the first cavity 150 is in communication with the first stage nozzle 110
  • the second cavity 160 is in communication with the second stage nozzle 120.
  • the first fluid passes through the first cavity 150 to the first In the stage nozzle 110
  • the second fluid is introduced into the second stage nozzle 120 through the second chamber 160.
  • the first cavity 150 is disposed in the upward direction of the first stage nozzle 110, which is the first orientation in FIG.
  • the cavity 150 is disposed directly above the first stage nozzle 110; in order to facilitate the passage of the second fluid while forming a wrap around the first fluid, the outer side wall of the first stage nozzle 110 is designed to be a curved shape with a decreasing diameter or other The curved structure, and the portion of the second stage nozzle 120 having a larger inner diameter is disposed outside the first stage nozzle 110. At this time, the outer side wall of the first stage nozzle 110 and the inner side wall of the second stage nozzle 120 are formed. In the arcuate region, the second cavity 160 is disposed in the arcuate region. The method increases the uniformity of the second fluid flow, and forms a uniform package for the first fluid coupled with the laser, which facilitates the transmission of the laser.
  • the first stage nozzle and the second stage nozzle are sealingly connected.
  • the first stage nozzle 110 and the second stage nozzle 120 may be coupled together by integral molding, which increases the tightness of the connection between the first stage nozzle 110 and the second stage nozzle 120, and contributes to the pressure inside the chamber. control.
  • the first stage nozzle 110 and the second stage nozzle 120 may be connected by means of welding or screwing or the like. The dispensing method facilitates the replacement of the second stage nozzle 120.
  • the laser processing head 100 of the present invention can realize high-energy laser output, and has the advantages of small heat impact, high processing quality, and high system reliability.
  • the output laser intensity reaches a certain level, it can be used for cleaning, surface scribing, cutting, drilling, laser shock strengthening and other processing. Due to the gradual coupling energy, the damage caused to the first stage nozzle 110 when the laser is incident is avoided, and the direct contact between the solid tube wall and the laser is avoided in the region where the laser intensity is increased, and the double fluid (the first fluid and The second fluid) isolation solves the contradiction between the system reliability and the high energy density coupling that are commonly found in water-assisted laser processing.
  • the controllability adjustment of the terminal laser jet can be realized by adjusting the nozzle model of the laser processing head 100, the pressure parameters of the first fluid and the second fluid, which lays a foundation for optimizing the process and realizing the versatility of the technology.
  • the invention also provides the above-mentioned application of the laser processing head 100 for laser processing deep into the workpiece or the fluid, overcomes the technical problems encountered in the processing in the deep complex environment or the narrow area, and ensures the processing quality.
  • the laser processing head 100 of the present invention is subjected to laser processing in the interior of the workpiece and into the interior of the fluid.
  • the end length of the second stage nozzle 120 can be extended as needed to better penetrate the complex environment and smoothly process.
  • the present invention also provides a laser processing system including a laser processing head 100, a laser 200, a first supply unit 300, a second supply unit 400, and a control unit 500.
  • the laser 200 is used to generate laser light;
  • the laser processing head 100 is used to transmit laser light generated by the laser to the workpiece to be processed;
  • the first supply unit 300 is used to supply the laser processing head 100 with a certain pressure of the first fluid, and the second supply unit 400 is used to supply a second fluid of a certain pressure to the laser processing head 100;
  • the control unit 500 is for controlling the actions of the first supply unit 300, the second supply unit 400, and the laser 200.
  • the laser 200 when laser processing is performed, the laser 200 generates laser light; the first supply unit 300 presses a certain pressure of the first fluid into the first cavity 150, and then the first fluid flows into the first stage nozzle 110; The second supply unit 400 presses the second fluid into the second cavity 160, and then the second fluid flows into the second stage nozzle 120; the laser generated by the laser 200 is first coupled into the first fluid, and then enters with the first fluid In the secondary nozzle 120, the first fluid is wrapped by the second fluid in the second stage nozzle 120; the diameter of the first fluid under the double constraint of the second fluid and the second stage nozzle 120 is gradually reduced, and finally a laser jet is formed. It is emitted from the end of the second stage nozzle 120, acts on the workpiece to be processed, and performs laser processing.
  • the refractive index of the first fluid to the light is greater than the refractive index of the second fluid to the light. Since the first fluid coupled with the laser is finally ejected from the end of the second stage nozzle 120 under the encapsulation of the second fluid, when the refractive index of the first fluid to the light is greater than the refractive index of the second fluid to the light, the first fluid and the second fluid can form a light guiding structure, which greatly reduces the energy loss of the laser during transmission. At the same time, due to the double ductility of the first fluid and the second fluid, the effective working distance of the laser is increased, which contributes to laser processing at a large depth and a large depth.
  • the first fluid is a liquid and the second fluid is a gas.
  • the first fluid is preferably water or other liquid;
  • the second fluid is preferably air, nitrogen, helium or argon that filters out impurities, and may be other gases. Since the gas has a light guiding coefficient of about 1, the water has a refractive index of about 1.334, and the total reflection incident angle of the two is about 48°.
  • the combination of gas and water can form a natural fiber effect, that is, a total reflection effect, and
  • the large total reflection angle is beneficial to shorten the transmission length required for the diameter change, and reduce the energy loss during the laser coupling process.
  • the laser processing process it has good chip evacuation performance under the dual action of airflow and water flow, avoiding the periphery. The secondary accumulation of materials is removed, which improves the quality of laser processing.
  • the second fluid may also be selected to have a lower density than the first fluid.
  • the intensity of the energy transmitted by the laser in pure water is very high.
  • the laser intensity of water destruction is greater than 6000 MW per square.
  • the laser processing system of the present invention can deliver high power lasers, including continuous wave and pulsed lasers.
  • a 25 ⁇ m diameter laminar water column can in principle deliver more than 37.5 kW of 532 ns or 1064 ns of laser light, while a 100 ⁇ m laminar water column can deliver 600 kW of laser power.
  • the inventors have experimentally confirmed the femtosecond 800 nm laser, the picosecond 1064 nm laser and the 532 nm laser, the nanosecond 1064 nm laser and the 532 nm laser, and the continuous wave 1064 nm laser, which prove the reliability of the technical solution of the present invention.
  • the refractive index of the first stage nozzle 110 of the laser processing head 100 to light is smaller than the refractive index of the first fluid to the light, that is, the light guiding structure is employed in the first stage nozzle 110.
  • the first fluid is water
  • the first stage nozzle 110 may be a fluororesin (TEFLON AF)
  • the optical refractive index of the fluororesin is 1.29
  • the optical refractive index of water is 1.334
  • the laser processing system described above further includes an optical unit 600 disposed between the laser and the laser processing head 100.
  • the optical unit 600 includes elements such as a reflecting lens, a lens mount, a beam expander, a grating, and the like for ensuring that laser light emitted from the laser 200 can be accurately incident into the laser processing head 100.
  • the laser emits laser light having a wavelength of 266 nm to 1100 nm, and the laser of the wavelength range has a certain degree of attenuation when transmitted in water, wherein the 532 nm laser has the smallest attenuation amplitude and the effective transmission distance.
  • the distance is more than 20m; the effective transmission distance of the 1064nm laser can also reach 100mm.
  • the laser processing system of the present invention can realize the stepwise coupling of laser energy by using the laser processing head 100 of the invention, has high coupling reliability, high coupling efficiency, does not damage solid devices, has small heat influence, and has high processing quality. A series of advantages such as expanding the processing range and the effectiveness of processing.
  • the laser processing system of the present invention can be directly applied to laser cutting, laser drilling or laser three-dimensional removal processing. It can be used for more other processing techniques, such as underwater cleaning and welding.
  • the present invention also provides a laser processing method comprising the following steps:
  • the first fluid coupled with the laser flows into the second stage nozzle, and is wrapped by the second fluid in the second stage nozzle;
  • a laser jet acts on the workpiece to be processed for laser processing.
  • the first fluid is a liquid and the second fluid is a gas.
  • the refractive index of the first fluid to light is greater than the refractive index of the second fluid to light.
  • the minimum inner diameter of the first stage nozzle is greater than twice the diameter of the spot after laser focusing; the inner diameter of the second stage nozzle is less than 1/2 of the minimum inner diameter of the first stage nozzle.
  • controllability adjustment of the laser jet diameter can be realized by adjusting the nozzle model of the laser processing head, the pressure parameters of the first fluid and the second fluid, and the versatility of the optimization process and the realization technology is laid. basis.
  • the laser processing method provided by the invention solves the contradiction between the high energy density laser and the system reliability by means of stepwise coupling, and can realize high power laser processing. It should be noted that the laser processing method of the present invention can be realized by the laser processing head of the present invention and the laser processing system of the present invention. Further, the laser processing method of the present invention can also be realized by other devices capable of satisfying the conditions.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Engineering (AREA)
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Abstract

一种激光加工头（100），包括：第一级喷嘴（110）、第二级喷嘴（120），两者相连通，第二级喷嘴（120）位于第一级喷嘴（110）下行方向；第二级喷嘴（120）的内径沿着激光传输方向逐渐减小，第一级喷嘴（110）的最小内径大于所述第二级喷嘴（120）的末端内径。激光加工头（100）通过分步耦合解决了高能量密度激光与系统可靠性之间的矛盾。还提供了一种激光加工头的应用、一种激光加工系统以及一种激光加工方法。

Description

激光加工头及其应用、激光加工系统及方法
相关申请
本发明申请要求2014年10月28日申请的，申请号为201410586246.1，名称为“激光加工头及其应用、激光加工系统及方法”的中国专利申请的优先权，在此将其全文引入作为参考。
技术领域
本发明涉及激光加工技术领域，特别是涉及一种用于高能激光加工的激光加工头及其应用、激光加工系统及方法。
背景技术
高能激光器，如数千瓦级的连续波光纤激光器、二氧化碳激光器、固体激光器，以及脉冲型的高功率激光器等，已经被广泛应用于工业制造中的去除类加工。激光去除加工时，当脉冲宽度较大(＞10皮秒)时，去除机理一般是熔化与升华并存，在辅助性气体的帮助下，将材料从基体上去除，该过程中会产生大量的热量，从而对加工工件产生影响。很多情况下，例如在进行热敏感材料的加工及金属钻孔时，要尽量避免热量对加工工件的影响。
为了减小热影响，研究人员在激光加工领域采用了一系列措施。其中之一是使用辅助性流体，如水流，来减少激光加工中的热影响。
相关报道揭示了将激光耦合进水流中，从而将水冷却和激光加工效应复合，既以激光为主，去除材料，又能通过水流冷却限制热影响区。同样的思路，欧洲的SYNOVA公司发明了微射流激光加工系统，通过高压腔体和宝石喷嘴形成微细的水射流，再将激光汇聚入宝石喷嘴，于是，脉冲激光随着直径小于100微米的水射流射出，在空气中形成自然的光导效应(通过全反射实现长距离的低损耗传输)，耦合了脉冲激光能量的水射流可以用纳秒脉冲激光实现热影响极小的加工。
上述思路依赖于空气中水射流的光导效应，理论上，一旦失去层状水流和空气界面，其光导效应就不复存在，所以，上述水助激光加工方法很难高效率实现超大深度(＞10mm)的加工。
美国GE公司发明了液核光纤激光加工系统，其利用了一种光导系数低于水的中空管，该中空管的材质为特种聚合物质特氟隆，熔点低于400℃。当水流过该中空管时，水和管壁就形成了光导系统。实验证实，该光导系统可通过能量超过4GW/cm2的纳秒绿光，达到很多激光加工中的能量要求。并且，上述中空管可深入水下进行激光加工，原理上可以钻入材料中， 实现无深度限制的激光去除加工。
但是，上述两种激光加工系统以及现有的其它水助激光加工系统均面临着一个技术难题，即：一方面为了产生微射流需要将喷嘴/中空管的内径做得很小，以便提升耦合后激光的能量密度；另一方面又要严格避免激光在狭小的入射口对中空管造成的损伤。以SYNOVA公司的微射流激光加工系统为例，尽管该系统正常工作时加工较薄的器件效果良好，但是，其可靠性因为喷嘴的易损性而很难提高。这里，“喷嘴的易损性”是由于系统在使用过程中有可能出现光斑位置的漂移，当高能激光直接打到喷嘴的非空部位时，可能会直接毁坏昂贵的宝石喷嘴；另外，即使没有光斑漂移，当有杂质颗粒通过狭窄的喷嘴部位时，杂质颗粒会被升华，产生高温等离子体，腐蚀入射口，从而对喷嘴造成损伤。
鉴于上述原因，为了保证系统的可靠性，目前的水助激光加工系统的适用功率偏低。为了进一步提升激光加工的能力，激光的高能量密度耦合与系统可靠性之间的矛盾成为急需解决的问题。
发明内容
本发明提供了一种激光加工头及其应用、激光加工系统及方法，有效解决了激光加工过程中激光的高能量密度耦合与系统可靠性之间的矛盾。
为达到上述目的，本发明采用如下技术方案：
一种激光加工头，用于将激光传输至待加工工件，包括：
第一级喷嘴；以及
第二级喷嘴，所述第二级喷嘴设置在所述第一级喷嘴的下行方向并与所述第一级喷嘴相连通；
其中，所述第二级喷嘴的内径沿着所述激光的传输方向逐渐减小，所述第一级喷嘴的最小内径大于所述第二级喷嘴的末端内径。
在其中一个实施例中，所述激光加工头还包括聚焦透镜，所述聚焦透镜设置在所述第一级喷嘴的上行方向。
在其中一个实施例中，所述激光加工头还包括透明窗口，所述透明窗口设置在所述聚焦透镜的上行方向。
在其中一个实施例中，所述第一级喷嘴的最小内径大于所述激光聚焦后的光斑直径的两倍；所述第二级喷嘴的末端内径小于所述第一级喷嘴的最小内径的1/2。
在其中一个实施例中，所述第二级喷嘴与所述第一级喷嘴一体成型。
在其中一个实施例中，所述第一级喷嘴和所述第二级喷嘴均为内壁光滑的金属管、玻璃管、陶瓷管或塑料管。
在其中一个实施例中，所述激光加工头还包括第一腔体和第二腔体；
所述第一腔体和所述第一级喷嘴相连通，所述第二腔体和所述第二级喷嘴相连通。
在其中一个实施例中，所述第一腔体设置在所述第一级喷嘴的上行方向；
第一级喷嘴的外侧壁为直径逐渐减小的曲线结构，第二级喷嘴中内径较大的部分围设在第一级喷嘴的外侧，所述第二腔体设置在所述第一级喷嘴的外侧壁和所述第二级喷嘴的内侧壁之间。
一种激光加工系统，包括：
激光器，所述激光器用于产生激光；
所述的激光加工头，所述激光加工头用于将所述激光传输至待加工工件；
第一供给单元和第二供给单元，所述第一供给单元用于为所述激光加工头提供一定压力的第一流体，所述第二供给单元用于为所述激光加工头提供一定压力的第二流体；以及
控制单元，所述控制单元用于控制所述第一供给单元、第二供给单元和所述激光器的动作。
在其中一个实施例中，所述第一流体对光的折射率大于所述第二流体对光的折射率。
在其中一个实施例中，所述第一流体为液体，所述第二流体为气体。
在其中一个实施例中，所述激光加工头的第一级喷嘴对光的折射率小于所述第一流体对光的折射率。
在其中一个实施例中，所述激光加工系统还包括光学单元，所述光学单元设置在激光器和激光加工头之间。
一种激光加工方法，包括以下步骤：
S100，将激光聚焦后耦合到第一级喷嘴的第一流体中；
S200，所述耦合有激光的第一流体流入第二级喷嘴，并被所述第二级喷嘴中的第二流体包裹；
S300，在所述第二级喷嘴和所述第二流体的双重约束下，所述耦合有激光的第一流体的直径逐渐减小，最终形成激光射流从所述第二级喷嘴的末端射出；
S400，所述激光射流作用于待加工工件上，进行激光加工。
在其中一个实施例中，所述第一流体为液体，所述第二流体为气体。
在其中一个实施例中，所述第一流体对光的折射率大于所述第二流体对光的折射率。
在其中一个实施例中，所述第一级喷嘴的最小内径大于所述激光聚焦后的光斑直径的两倍；
所述第二级喷嘴的末端内径小于所述第一级喷嘴的最小内径的1/2。
在其中一个实施例中，所述激光射流的直径大小通过所述第一流体和所述第二流体的压 力进行调节。
一种所述的激光加工头的应用，用于深入工件或流体内部进行激光加工。
本发明具有如下有益效果：
本发明提供的激光加工头及其应用、激光加工系统及方法，通过分步耦合的方式解决了高能量密度激光与系统可靠性之间的矛盾。工作时，首先将激光耦合进第一级喷嘴的第一流体中，由于第一级喷嘴的直径较大，因此，降低了激光的耦合难度，避免了由于激光光斑的漂移或杂质颗粒的腐蚀对激光加工头造成的损伤，增加了系统的可靠性；然后通过外界约束将第一流体的直径逐渐减小，使其最终形成激光射流射出，在第一流体的直径逐渐减小的过程中，耦合到第一流体中的激光的光束也会逐渐缩小，激光的能量密度逐步增大，最终输出高能激光束；这种输出激光能量的方式可以通过产生极细微的激光射流突破传统激光聚焦的分辨率极限，达到5微米甚至亚微米量级，同时保持远远大于末端水流直径长度的加工深度能力；最后，由于可靠性的提高，千瓦级激光的水助激光加工成为可能，相对目前的水助激光加工大大提高了加工速度。
附图说明
图1为本发明激光加工头一实施例的结构示意图；
图2为本发明激光加工头深入工件进行加工一实施例的结构示意图；
图3为本发明激光加工头深入流体内部进行加工一实施例的结构示意图；
图4为本发明激光加工系统一实施例的功能示意图；
图5为流体约束仿真截图。
具体实施方式
以下对本发明的具体实施方式进行详细说明。应当理解的是，此处所描述的具体实施方式仅用于说明和解释本发明，并不用于限制本发明。为了方便各个部件的位置关系描述，本发明定义激光的传输方向为下行方向，反之即为上行方向。
本发明提供了一种激光加工头，用于将激光器发出的激光传输至待加工工件，尤其适用于高能量激光的传输。
参见图1，本发明的激光加工头100包括相互连通的第一级喷嘴110和第二级喷嘴120，其中，第二级喷嘴120位于第一级喷嘴110的下行方向，即激光器发出的激光先进入第一级喷嘴110，再进入第二级喷嘴120。图中箭头所指示的方向为激光的传输方向。
第二级喷嘴120的内径沿着激光的传输方向逐渐减小，第一级喷嘴110的最小内径大于所述第二级喷嘴120的末端(激光的出射端)内径。
需要说明的是，本发明中，第一级喷嘴110可为等内径结构，也可为变内径结构。较优地，如图1所示，第一级喷嘴110为等内径结构，即内部直径相等，此时，其最小内径即为其内部直径。等内径的设计有利于激光的初步耦合，能够有效避免激光在初步耦合过程中所造成的损耗。
工作时，在第一级喷嘴110中通入一定压力的第一流体，并在第二级喷嘴120中通入一定压力的第二流体；其中，第一流体用于耦合射入第一级喷嘴110的激光，第二流体用于包裹耦合有激光的第一流体。在进行激光加工时，首先将激光耦合到第一流体中；而后，耦合至第一流体的激光随着第一流体进入第二级喷嘴120，在第二级喷嘴120中，第二流体将耦合有激光的第一流体包裹在内，由于第二级喷嘴120的内径沿着激光的传输方向逐渐减小，同时，第二流体具有一定的压力，因此，耦合有激光的第一流体的直径在第二级喷嘴120和第二流体的双重约束下逐渐减小，激光的光斑也随之逐渐减小，激光的能量密度(激光强度)逐渐增大；耦合有激光的第一流体最终在第二流体的包裹下形成激光射流从第二级喷嘴120的末端射出，作用于待加工工件，实现高能量激光加工。
本发明的激光加工头100，通过逐步耦合的方式解决了高能量激光密度和系统可靠性之间的矛盾。由于第一级喷嘴110的最小内径大于所述第二级喷嘴120的末端内径，因此，第一流体具有相对较大的内径，在进行激光耦合时，可以使用较大的激光光斑，降低了初始耦合时激光的能量密度，从而降低了激光对第一级喷嘴110造成损伤的风险，提高了激光的耦合效率及系统的可靠性，而且，第一级喷嘴110可以采用低成本耐高温的材质，如石英管，相比于宝石喷嘴，大大降低了成本；同时，由于采用第二流体约束而非固体直接约束的形式来逐步减小第一流体的直径，在激光强度升高的区域，有效防止了激光和第二级喷嘴120的直接接触，进一步增加了系统的可靠性，可将超大功率连续波激光(1000W以上)或高平均功率脉冲激光(百瓦级以上纳秒、皮秒、飞秒激光器)的能量耦合到非常细的终端激光射流中，从而发挥激光高去除速度和高加工质量的优势。
较佳地，第一级喷嘴110的末端内径小于等于第二级喷嘴120的初始端内径。该方式有助于第二流体对第一流体形成包裹，并能够有效避免紊流。
本发明中，第一流体的最终直径(从第二级喷嘴120末端射出时的直径)的大小可通过调整第一流体和第二流体的压力来进行调节，也可通过改变第二级喷嘴120的末端直径大小来进行调节，基本要求是保证耦合有激光的第一流体为层流状态，避免紊流，从而使得激光能够顺利传输。
在具体的激光加工过程中，第一流体的最终直径的大小与输入的激光功率和所需的激光强度有关。比如，对于纳秒脉冲激光去除加工来说，需要达到500MW/cm2以上的激光强度，一般需要100μm以下的最终直径；而对于1000W的连续波激光来讲，如果需要达到5MW/cm2以 上的激光强度，则最终直径需要达到小于150μm。
较佳地，如图1所示，本发明的激光加工头100还包括聚焦透镜130。聚焦透镜130设置在第一级喷嘴110的上行方向，即激光器发出的激光经过聚焦透镜130的聚焦后再进入第一级喷嘴110。聚焦透镜130能够起到汇聚光束的作用，将激光的能量聚焦为一个光斑，使其能够更容易耦合到第一流体中，减小激光在传输及耦合过程中的能量损耗。
其中，聚焦透镜130的焦距和具体设置位置可根据实际需要进行选择，当第一级喷嘴110中不使用光导结构时(即第一流体对光的折射率小于等于第一级喷嘴110对光的折射率时)，可以使激光的焦点聚焦到第一级喷嘴110的出口下方，以便减少激光的能量损耗；当第一级喷嘴110中使用光导结构时(即第一流体对光的折射率大于第一级喷嘴110对光的折射率时)，激光的聚焦点可以位于第一级喷嘴110的任何位置处。
更佳地，上述的激光加工头100还包括透明窗口140。该透明窗口140设置在聚焦透镜130的上行方向，用于保护聚焦透镜130，防止聚焦透镜130污染而影响聚焦效果。一般地，透明窗口140的材质为石英玻璃。
为了增加激光耦合的可靠性，避免激光在入射时对激光加工头100造成损伤，作为优选，第一级喷嘴110的最小内径大于激光聚焦后的光斑直径的2倍，优选为0.25mm-0.75mm；同时，为了提高最终输出的激光的能量密度，第二级喷嘴120的最小内径(即第二级喷嘴120的末端内径)小于第一级喷嘴110的最小内径的1/2，优选为5μm-100μm,，需要时可以更小，达到亚微米级。
进一步地，为了避免激光对喷嘴的损伤，同时降低成本，第一级喷嘴110可以使用内壁光滑的金属管、陶瓷管或玻璃管，在满足长期稳定性的前提下也可使用塑料管。其中，金属管包括不锈钢管、铜管等，玻璃管包括石英管等。第二级喷嘴120也可为上述的管材。
继续参见图1，上述的激光加工头100还包括第一腔体150和第二腔体160。其中，第一腔体150与第一级喷嘴110相连通，第二腔体160与第二级喷嘴120相连通，在进行激光加工时，第一流体通过第一腔体150通入到第一级喷嘴110中；第二流体通过第二腔体160通入到第二级喷嘴120中。
如图1所示，为了便于第一流体通入，作为一种可实施方式，第一腔体150设置在第一级喷嘴110的上行方向，以图1中的方位来看，即为第一腔体150设置在第一级喷嘴110的正上方；为了便于第二流体的通入，同时对第一流体形成包裹，第一级喷嘴110的外侧壁设计为直径逐渐减小的弧形或其它曲线结构，而第二级喷嘴120的内径较大的部分则围设在第一级喷嘴110的外侧，此时，第一级喷嘴110的外侧壁与第二级喷嘴120的内侧壁之间形成弧形区域，第二腔体160则设置在该弧形区域中。该方式增加了第二流体流动的均匀性，可对耦合有激光的第一流体形成均匀的包裹，利于激光的传输。
较佳地，本发明的激光加工头100中，第一级喷嘴和第二级喷嘴密封连接。第一级喷嘴110和第二级喷嘴120可通过一体成型的方式连接在一起，该方式增加了第一级喷嘴110和第二级喷嘴120之间连接的密封性，有助于腔体内压力的控制。此外，第一级喷嘴110和第二级喷嘴120也可通过焊接或螺纹连接等分装的方式进行连接。分装的方式便于第二级喷嘴120的更换。
本发明的激光加工头100可以实现高能量的激光输出，具有热影响小、加工质量高、系统可靠性高等优点。当输出的激光强度达到一定的水平时，就可以用于清洗、表面刻划、切割、钻孔、激光冲击强化等加工。由于采用逐步耦合能量的方式，避免了激光入射时对第一级喷嘴110造成的损伤，在激光强度升高的区域避免了固体管壁与激光的直接接触，以双层流体(第一流体和第二流体)隔离，解决了目前水助激光加工中普遍存在的系统可靠性与高能量密度耦合之间的矛盾。此外，可通过调整激光加工头100的喷嘴型号、第一流体和第二流体的压力参数，实现终端激光射流的可控性调整，为优化工艺和实现技术的通用性奠定了基础。
同时，本发明还提供了上述激光加工头100在深入工件或流体内部进行激光加工的应用，克服了以往在深入复杂环境或狭窄区域进行加工时遇到的技术难题，并保证了加工质量。参见图2和图3，分别为本发明的激光加工头100在深入工件内部和深入流体内部进行激光加工的结构示意图。较优地，第二级喷嘴120的末端长度可以根据需要进行延伸，以便更好的深入复杂环境，顺利实现加工。
参见图4，本发明还提供了一种激光加工系统，该系统包括激光加工头100、激光器200、第一供给单元300、第二供给单元400和控制单元500。
其中，激光器200用于产生激光；激光加工头100用于将激光器产生的激光传输至待加工工件；第一供给单元300用于为激光加工头100提供一定压力的第一流体，第二供给单元400用于为激光加工头100提供一定压力的第二流体；控制单元500用于控制第一供给单元300、第二供给单元400和激光器200的动作。
结合图1和图4，在进行激光加工时，激光器200产生激光；第一供给单元300将一定压力的第一流体压入第一腔体150，随后，第一流体流入第一级喷嘴110；第二供给单元400将第二流体压入第二腔体160，随后，第二流体流入第二级喷嘴120；激光器200产生的激光首先耦合到第一流体中，然后随着第一流体进入第二级喷嘴120中，第一流体在第二级喷嘴120中被第二流体包裹；在第二流体和第二级喷嘴120的双重约束下的第一流体的直径逐渐减小，最终形成激光射流从第二级喷嘴120的末端射出，作用于待加工工件，进行激光加工。
作为优选，在上述的激光加工系统中，第一流体对光的折射率大于第二流体对光的折射率。由于耦合有激光的第一流体最终是在第二流体的包裹下从第二级喷嘴120末端射出并作 用于待加工工件，当第一流体对光的折射率大于第二流体对光的折射率时，第一流体和第二流体可形成光导结构，大大降低了激光在传输过程中的能量损耗，同时由于第一流体和第二流体的双重延展性，增加了激光的有效作用距离，有助于实现大深度、超大深度的激光加工。
较佳地，在上述的激光加工系统中，第一流体为液体，第二流体为气体。此方式利于激光的耦合，便于形成第二流体包裹的形态，具有更优的可控性。其中，第一流体优选为水，也可为其他液体；第二流体优选为滤掉杂质的空气、氮气、氖气或氩气，也可为其他气体。由于气体的光导系数约为1，水的光折射率约为1.334，二者的全反射入射角约为48°，因此，气体和水的组合可形成自然光纤效应，即全反射效应，且较大的全反射角有利于缩短直径变化所需的传输长度，降低激光耦合过程中的能量损失，同时，激光加工过程中，在气流和水流的双重作用下具有良好的排屑性能，避免了周边去除材料的二次堆积，提高了激光加工的质量。
此外，当第一流体为液体时，第二流体也可选用密度小于第一流体的液体。
当第一流体为水，第二流体为气体时，由于激光在纯净水中传输的能量强度极限很高，如对纳秒级532nm或1064nm的激光，水发生破坏的激光强度大于6000兆瓦每平方厘米，远高于常规的固体光纤(低于1000兆瓦每平方厘米)，加上自然的水冷效应，本发明的激光加工系统可以传输大功率的激光，包括连续波和脉冲激光。例如，25μm直径的层流水柱原则上可以传输超过37.5千瓦的532ns或1064ns的激光，而100μm的层流水柱可以传输600千瓦的激光功率。发明人对飞秒800nm激光，皮秒1064nm激光和532nm激光，纳秒1064nm激光和532nm激光，连续波1064nm激光均进行了实验证实，证明了本发明的技术方案的可靠性。
发明人对利用流体约束来缩小直径进行了仿真和实验研究，均证明了其可行性。参见图5，为利用ANSYS软件得出的空气对水流的约束仿真截图，其中，中间黑色部分为水；外侧颜色较浅的部分为空气。仿真结果表明，可以通过调节水流和气体的相关参数，生成稳态包裹的层流微射流。
进一步地，激光加工头100的第一级喷嘴110对光的折射率小于第一流体对光的折射率，即第一级喷嘴110中采用光导结构。当第一流体为水时，第一级喷嘴110可采用氟树脂(TEFLON AF)，氟树脂的光学折射率为1.29，而水的光学折射率为1.334，因此，二者之间可形成光导结构，降低激光在耦合过程中的能量损失。
作为一种可实施方式，上述的激光加工系统中，还包括设置在激光器和激光加工头100之间的光学单元600。该光学单元600包括反射镜片、镜片调整架、扩束镜、光栅等元件，用于保证激光器200发出的激光能够精确入射到激光加工头100中。
本发明的激光加工系统中，激光器发射的激光的波长可为266nm-1100nm，该波长范围的激光在水中传输时都有一定程度的衰减，其中以532nm的激光的衰减幅度最小，有效传输距 离为20m以上；1064nm的激光的有效传输距离也可达到100mm。
本发明的激光加工系统，由于采用本发明的激光加工头100，可实现激光能量的分步耦合，具有耦合可靠性高、耦合效率高、不损伤固体器件、热影响小、加工质量高、可扩展加工范围和加工的有效性等一系列优点。利用本发明的激光加工系统可直接应用于激光切割、激光打孔或激光三维去除加工。经过改造，可以用于更多其它加工工艺，如水下清洗、焊接等。
此外，本发明还提供了一种激光加工方法，包括以下步骤：
S100，将激光聚焦后耦合到第一级喷嘴的第一流体中；
S200，耦合有激光的第一流体流入第二级喷嘴，并被第二级喷嘴中的第二流体包裹；
S300，在第二级喷嘴和第二流体的双重约束下，耦合有激光的第一流体的直径逐渐减小，最终形成激光射流从第二级喷嘴的末端射出；
S400，激光射流作用于待加工工件上，进行激光加工。
上述激光加工方法中，第一流体为液体，第二流体为气体。优选地，第一流体对光的折射率大于第二流体对光的折射率。更优地，第一级喷嘴的最小内径大于所述激光聚焦后的光斑直径的两倍；第二级喷嘴的末端内径小于所述第一级喷嘴的最小内径的1/2。上述方案的有益效果在激光加工头的部分已经做了详细说明，此处不再赘述。
本发明的激光加工方法中，可通过调整激光加工头的喷嘴型号、第一流体和第二流体的压力参数，实现激光射流直径的可控性调整，为优化工艺和实现技术的通用性奠定了基础。
本发明提供的激光加工方法，通过逐步耦合的方式解决了高能量密度激光与系统可靠性之间的矛盾，可实现大功率的激光加工。需要说明的是，本发明的激光加工方法可通过本发明的激光加工头和本发明的激光加工系统来实现。此外，本发明的激光加工方法也可通过其他能够满足条件的设备来实现。
以上所述实施例仅表达了本发明的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干变形和改进，这些都属于本发明的保护范围。因此，本发明专利的保护范围应以所附权利要求为准。

Claims (19)

  1. 一种激光加工头，用于将激光传输至待加工工件，其特征在于，包括：
    第一级喷嘴；以及
    第二级喷嘴，所述第二级喷嘴设置在所述第一级喷嘴的下行方向并与所述第一级喷嘴相连通；
    其中，所述第二级喷嘴的内径沿着所述激光的传输方向逐渐减小，所述第一级喷嘴的最小内径大于所述第二级喷嘴的末端内径。
  2. 根据权利要求1所述的激光加工头，其特征在于，所述激光加工头还包括聚焦透镜，所述聚焦透镜设置在所述第一级喷嘴的上行方向。
  3. 根据权利要求2所述的激光加工头，其特征在于，所述激光加工头还包括透明窗口，所述透明窗口设置在所述聚焦透镜的上行方向。
  4. 根据权利要求2所述的激光加工头，其特征在于，所述第一级喷嘴的最小内径大于所述激光聚焦后的光斑直径的两倍；所述第二级喷嘴的末端内径小于所述第一级喷嘴的最小内径的1/2。
  5. 根据权利要求1所述的激光加工头，其特征在于，所述第二级喷嘴与所述第一级喷嘴一体成型。
  6. 根据权利要求1所述的激光加工头，其特征在于，所述第一级喷嘴和所述第二级喷嘴均为内壁光滑的金属管、玻璃管、陶瓷管或塑料管。
  7. 根据权利要求1所述的激光加工头，其特征在于，所述激光加工头还包括第一腔体和第二腔体；
    所述第一腔体和所述第一级喷嘴相连通，所述第二腔体和所述第二级喷嘴相连通。
  8. 根据权利要求7所述的激光加工头，其特征在于，所述第一腔体设置在所述第一级喷嘴的上行方向；
    第一级喷嘴的外侧壁为直径逐渐减小的曲线结构，第二级喷嘴中内径较大的部分围设在第一级喷嘴的外侧，所述第二腔体设置在所述第一级喷嘴的外侧壁和所述第二级喷嘴的内侧壁之间。
  9. 一种激光加工系统，其特征在于，包括：
    激光器，所述激光器用于产生激光；
    权利要求1-8任一项所述的激光加工头，所述激光加工头用于将所述激光传输至待加工工件；
    第一供给单元和第二供给单元，所述第一供给单元用于为所述激光加工头提供一定压力 的第一流体，所述第二供给单元用于为所述激光加工头提供一定压力的第二流体；以及
    控制单元，所述控制单元用于控制所述第一供给单元、第二供给单元和所述激光器的动作。
  10. 根据权利要求9所述的激光加工系统，其特征在于，所述第一流体对光的折射率大于所述第二流体对光的折射率。
  11. 根据权利要求9所述的激光加工系统，其特征在于，所述第一流体为液体，所述第二流体为气体。
  12. 根据权利要求9所述的激光加工系统，其特征在于，所述激光加工头的第一级喷嘴对光的折射率小于所述第一流体对光的折射率。
  13. 根据权利要求9所述的激光加工系统，其特征在于，所述激光加工系统还包括光学单元，所述光学单元设置在激光器和激光加工头之间。
  14. 一种激光加工方法，其特征在于，包括以下步骤：
    S100，将激光聚焦后耦合到第一级喷嘴的第一流体中；
    S200，所述耦合有激光的第一流体流入第二级喷嘴，并被所述第二级喷嘴中的第二流体包裹；
    S300，在所述第二级喷嘴和所述第二流体的双重约束下，所述耦合有激光的第一流体的直径逐渐减小，最终形成激光射流从所述第二级喷嘴的末端射出；
    S400，所述激光射流作用于待加工工件上，进行激光加工。
  15. 根据权利要求14所述的激光加工方法，其特征在于，所述第一流体为液体，所述第二流体为气体。
  16. 根据权利要求14所述的激光加工方法，其特征在于，所述第一流体对光的折射率大于所述第二流体对光的折射率。
  17. 根据权利要求14所述的激光加工方法，其特征在于，所述第一级喷嘴的最小内径大于所述激光聚焦后的光斑直径的两倍；
    所述第二级喷嘴的末端内径小于所述第一级喷嘴的最小内径的1/2。
  18. 根据权利要求14-17任一项所述的激光加工方法，其特征在于，所述激光射流的直径大小通过所述第一流体和所述第二流体的压力进行调节。
  19. 一种如权利要求1-8任一项所述的激光加工头的应用，用于深入工件或流体内部进行激光加工。
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US20170320166A1 (en) 2017-11-09
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