Water-jet Guided Laser Processing Research Articles

Efficient computation of heat distribution of processed workpiece with coupling to bottom water vapor in water-jet guided laser machining.

In this paper, we present a novel approach for calculating the heat distribution within a processed workpiece subjected to laser irradiation while accounting for the influence of bottom water vapor. A comprehensive mathematical model is introduced and numerical techniques using difference approximation are employed. Initially, the three-dimensional heat equation, originally defined in the rectangular coordinate system, is transformed into a corresponding model within the cylindrical coordinate system, incorporating a nonlinear boundary condition to account for coupling effects. Subsequently, leveraging the axial symmetry of the heat distribution, the three-dimensional model is simplified into a two-dimensional one. This simplified model is solved using the alternating direction implicit scheme coupled with the Crank-Nicolson method. Moreover, we develop a high-precision numerical treatment for the nonlinear boundary condition within the cylindrical coordinate system. To validate our methodology, simulation experiments are conducted on three distinct samples. Our comparative results demonstrate the feasibility and efficiency of the proposed approach in the context of water-jet guided laser processing.

Study on fluid flow characteristics and laser transmission mode of water jet–guided laser processing in blind hole

Study on fluid flow characteristics and laser transmission mode of water jet–guided laser processing in blind hole

Experimental Research and Optimization of Ti-6Al-4V Alloy Microgroove Machining Based on Waterjet-Guided High-Power Laser.

In order to improve the tribological properties of Ti-6Al-4V alloy and further broaden the application scope of titanium alloy materials in the industrial field, a preparation method of a waterjet-guided high-power laser processing surface microgroove was studied. In this paper, a multifocus coupling lens was innovatively designed to replace the spherical lens in the traditional waterjet-guided laser coupling device, which avoids the gas explosion phenomenon in the coupling of the high-power laser and waterjet, and realizes the high-quality coupling of the high-power laser and water beam fiber. Then, with the microgroove morphology as the response target, the single-factor test and response surface test of the water-guided laser processing microgroove were carried out. Based on the experimental results, an approximate mathematical model of the response surface between the process parameters and the microgroove topography target was constructed, and the quantitative relationship between the waterjet-guided laser processing parameters and the target response was studied. At the same time, the optimal combination of process parameters was obtained by multiobjective optimization, so as to effectively improve the microgroove morphology. This technology provides method guidance and a decision-making reference for subsequent waterjet-guided laser processing of titanium alloy surface functional microstructures.

Study on reducing burrs of super alloy through structures in water jet guided laser ablation

With the increase of thrust-weight ratio of aero-engine, the working temperature of core parts is becoming higher and higher. In order to improve the service life of core parts, many high-precision micro holes are machined on those core parts. To realize the fabrication of micro hole with less burrs on super alloy substrates, a novel water jet guided laser processing method is proposed in this paper. A material removal principle based on plasma detonation assistant machining is proposed and proved to be valid through experiments. Then a laser-induced plasma assisted ablation method using sacrificial layer in the machining of through holes and grooves on super alloy is approved. This method can get higher machining efficiency and avoid longtime trimming in subsequent experiments. The size of burrs in through hole decreases 57.89%, while the area of burrs decreases 42.32% after using 304 stainless steel as sacrificial layer in the machining of through hole. Grooves with fewer burrs are also achieved on super alloy with this method. That method can also be used to fabricate a variety of functional structures.

Numerical simulation of the stability of water fiber-optic in water jet-guided laser machining

Water jet-guided laser machining is a new compound machining technology, which has been widely used in many fields due to its better processing effect. In this technology, the coupling of laser beam and micro-water jet directly determines the machining effect, and the prerequisite for successful coupling is the steady flow of the water jet, so ensuring the stability of the micro-water jet is the key to the stable machining of water jet-guided laser. Therefore, it is of great significance to studying the stability of the water fiber-optic in water jet-guided laser processing. In this paper, aiming at the problem that the stability of the water fiber-optic is difficult to control, a finite element model of the water fiber-optic is established. The convection model is vortex gas-phase flow “enveloped” water fiber-optic which is used to explain the interaction mechanism, and the flow field distribution of gas-phase flow and water fiber-optic convection was obtained. The results show that water fiber-optic is refined under the constraint of gas-phase flow, and the maximum processing distance can increase by three times. At the same time, the gas-phase flow can accelerate the removal of processing debris, and the processing accuracy and efficiency are improved.

Experimental Research of CFRP Cutting by Using Water Jet Guided Laser Processing#br#

Experimental Research of CFRP Cutting by Using Water Jet Guided Laser Processing#br#

The cutting process and damage mechanism of large thickness CFRP based on water jet guided laser processing

Carbon fiber-reinforced polymer composites (CFRP) is a composite material with resin as matrix and carbon fiber as reinforcement. It has been widely used in aerospace, military products, and automotive industries. However, CFRP is prone to damage because of its complex anisotropy and low interlayer strength, so it is a typical difficult-to-process material. Water jet guided laser processing technology is a combination of laser and water jet processing technology, which has the characteristics of no wear, no contact, flexible processing, and potential advantages of reducing HAZ and increasing cutting depth. In this paper, the water jet guided laser processing technology is used to perform cutting experiment for CFRP processing of low damage and large depth. In the experiment, the influencing law of the process parameters such as laser power, CFRP feed speed and water jet speed on the cutting results is obtained; then the cutting thickness of 1 mm, 2 mm, 4 mm and 10 mm CFRP is realized by adopting the parallel path layered scanning method. Moreover, the influences of carbon fiber arrangement direction and laser cutting path on the CFRP cutting damage mechanism are analyzed for the first time, and three damage mechanisms (exposing, falling-off and pulling-out) are summarized, which will provide the reference for the high precision cutting of large thickness CFRP.

Research on water jet-guided laser micro-hole machining of 6061 aluminum alloy

With the rapid development of the information age, electronic components are developing toward miniaturization, which makes the manufacturing of chips more and more difficult. Water jet-guided laser processing technology (WJGL) is a composite processing technology that combines pulsed laser and water jet, which can ensure the accuracy and efficiency of processing while small size parts machining. This paper is based on the “element birth and death” technique in the finite element method and the three-dimensional transient temperature field and subsequent material removal model of 6061 aluminum alloy are established. The effects of laser average power, pulse repetition frequency, and pulse action time on the transient thermal distribution, aperture, taper, and other forming qualities with the two technologies of fixed-point drilling and spiral drilling, respectively, are studied. Combining the experimental process, the general rule of morphology change of the micro-hole is obtained. The results show that WJGL of micro-hole is based on the combined effect of thermal ablation and real-time cooling. Spiral drilling can maintain a better hole shape but fixed-point drilling can achieve a smaller hole taper. With the increase of laser power, the hole taper increases, reaching saturation at 8 W. The repetition frequency is between 50 and 70 kHz to obtain better hole morphology while maintaining better processing efficiency, and the minimum hole taper is 8.21°.

Micromorphology of metallic surfaces for hydrophobicity by waterjet-guided laser processing

Waterjet-guided laser processing is a novel machining technique for metallic materials. To investigate and analyse the effects of processing parameters on surface topography change, micro-texturing evolution, and hydrophobicity, micromorphology machining experiments were conducted on stainless steel using self-developed waterjet-guided laser processing equipment. Nd:DPSS laser system with repetition frequency of 20–120 kHz and maximum power of 50W is used in the equipment. A scanning electron microscope (SEM) is used to measure surface topography. Energy-dispersive spectrometer (EDS) is used to evaluate the material composition of processing zone and no processing zone. The effects of grid spacing and laser power coupled into the jet are examined and processing conditions for hydrophobicity are provided. There was oxidation and no crack on the kerf edge. The surface contact angle dramatically increases from 92.94 to 138.41° with the decreasing of the grid size. It has been shown that waterjet-guided laser processing yields textures with a hydrophobic surface and is suit for micro-texture micro-machining.

Numerical simulation of water jet–guided laser micromachining of CFRP

Carbon fiber-reinforced plastics (CFRP) composites are increasingly used in the aerospace and automotive industries due to their excellent properties, which require higher processing accuracy to ensure their performance. Water jet-guided laser processing technology is a modern processing method, which can effectively reduce the thermal damage caused by laser processing. In order to understand the transient thermal effect of water jet-guided laser processing on CFRP materials and its removal mechanism and the influence of the duty cycle of laser pulse on the temperature field distribution of materials, this paper is based on the “element birth and death” technique in the finite element method, the three-dimensional transient temperature field of heterogeneous fiber matrix and the subsequent material removal model are established. The results show that the CFRP composites processed by water jet-guided laser processing can obtain better processing results over traditional laser processing. Adjusting the duty cycle of laser pulses can significantly affects the shape and temperature distribution of the composites after drilling.

Electrodynamic simulation of laser beam propagation in waterjet-guided laser processing

Waterjet-guided material processing is a technique that combines the capabilities of laser material processing with water jetting. In this study, we have investigated laser beam propagation in a waterjet column by numerically solving the Maxwell equations and the heat equation. A 1064 nm laser and its frequency-doubled 532 nm laser were chosen for the simulations, and the finite-difference time-domain (FDTD) method was employed for solving the Maxwell equations. The coupling effect of the laser and waterjet was simulated with different numerical apertures and different waterjet column diameters. Extensive investigations on laser absorption phenomena regarding the outer surface geometries of the waterjet (cylindrical shape with and without sinusoidal perturbation), and temperature distributions were also conducted. To the best of the authors' knowledge, this is the first electrodynamic simulation of laser beam propagation and interaction with a water column in waterjet-guided laser processing. Some interesting findings concerning laser beam absorption characteristics inside a waterjet column were revealed.

Texturing of metallic surfaces for superhydrophobicity by water jet guided laser micro-machining

This experimental work demonstrates a new cost-effective way of achieving superhydrophobicity on metallic surfaces by micro-texturing with a novel water jet guided laser process. Compared to conventional pure laser texturing by nanosecond, picosecond and femtosecond lasers, water jet guided laser processing yields textures with an almost zero heat affected zone while the debris on the textured surface is simultaneously cleaned by the jet during the process. The effects of grid spacing, laser power coupled into the jet and water jet diameter are examined and processing conditions for achieving superhydrophobicity are provided. Changes in the wetting of the surface over time under ambient conditions from hydrophilic to superhydrophobic, due to changes in surface chemistry, were explored. It has been shown that the surface contact angle dramatically increases within the first couple of days after texturing when exposed to air. After around 20 days, the contact angle stabilized at 150°, 130° and 129° on textured 304 stainless steel, titanium and 6061 aluminum surfaces, respectively.

The stability of 30-μm-diameter water jet for jet-guided laser machining

Combined water-jet process and laser machining, the water jet-guided laser processing is suitable in processing a thin and sensitive material with a high degree of precision required. Given that there are many uncertainties of the jet with lower than a 50-μm-diameter nozzle and lower velocities in the stability field of water jet-guided laser machining, a numerical model of a 30-μm water jet, considering the number of grids and the influence of meshes, has been studied to meet the requirements of micrometer order precision machining. Furthermore, the critical Reynolds number and the critical jet exit velocity of the case with a 30-μm-diameter nozzle have been presented to make a comparison between turbulence flow and laminar flow in air with different jet exit velocities from 0.2 to 500 m/s. Hence, the optimal jet exit velocity to achieve the longest stable length of water jet was found. Besides, three cases of 15 m/s jet exit velocity are simulated in different degrees of vacuum, which suggest water jets in vacuum are much more stable than those in atmospheric environment. Finally, a conjecture about water-jet simulation with a smaller diameter of nozzle is proposed as a future work.

Experimental Study on Water-Jet Guided Laser Machining Magnesium Alloy

Drilling and cutting experiments in magnesium alloy sheet were conducted using water-jet guided laser. Morphology characteristics in processing areas were analyzed and compared with that of the conventional laser processing. The results show the processing areas are clean, with almost no molten residues attached and negligible heat damage in water-jet guided laser processing. The hole walls and cut surfaces are smooth and have some degree of slope, and are completely covered with dense protruding particles at microcosmic scale. However, with conventional laser, the processed areas are attached with a large number of residues, and obvious secondary solidified layers.

Simulation on Drilling with Water-Jet Guided Laser

Water-jet guided laser processing is a kind of material processing technology using variable-length water jet optical waveguide. In this paper, by means of the finite element method (FEM), the simulation on drilling with water-jet guided laser was carried out based on thermal effect of laser and mechanical effect origining from shock pressure of shock wave caused by heat-induced explosion and impact of high-speeds water jet. The results show that evaporation and mechanical ablation of molten material is the main form of the material removal, the mechanical effect only contributes the slight deformation to the material with temperature gradient, the rapid water jet cooling after laser pulse played a quenching role in the processing area. In addition, the paper also analyzed the variable tendency of the impact of water jet to workpiece and clarified the scope and trend of the role of water jet.

A Research on Surface Morphology of Cutting of Titanium Sheet with Water-Jet Guided Laser and Conventional Laser

Titanium is a class of material difficult to common machine. Laser processing is a feasible method for machining of titanium. This paper presents cutting investigation of industry pure titanium sheet with conventional laser and water-jet guided laser, and analyses their processing features by means of the surface morphology of kerf obtained from Scanning Electron Microscope. The result shows that the machining quality and cleanliness of water-jet guided laser processing is much better than conventional laser processing. The impact and cool effects of the high-speeds water jet are more effective to trim the cut surface and remove molten waster.

Modelling of heat transfer in waterjet guided laser drilling of silicon

Waterjet guided laser processing is an internationally patented technique based on guiding a laser beam inside a thin, high-speed waterjet. The process combines the advantages of laser processing with those of waterjet cutting. It is very suitable in processing thin and heat-sensitive materials with a high degree of precision required. A model and simulation method for waterjet guided laser drilling on a silicon substrate are presented in this study. A finite difference method has been developed to simulate the thermal field and phase changes involved. The model represents the thermal process in detail. The simulation results predict the main characteristics of waterjet guided laser drilling. The study gives insight into the interactions between the laser beam, waterjet and workpiece material during drilling of a silicon substrate.

Modeling of waterjet guided laser grooving of silicon

Waterjet guided laser processing is an internationally patented technique based on guiding a laser inside a thin, high-speed waterjet. The process combines the advantages of laser processing with those of waterjet cutting and offers promise as a method for processing thin and heat sensitive materials with a high degree of precision. An improved understanding of the complex interaction between laser, waterjet, and workpiece is required to enable the process to achieve its potential. A model for waterjet guided laser grooving of silicon is presented that treats the energy input of the laser, the cooling effect of the waterjet, and the melting and removal of the silicon. The thermal process is represented in detail in the new method. The model is validated by comparisons of simulation and experimental results, and the simulation provides insight regarding the details of the interactions among laser, waterjet, and workpiece.