Research and application development of compound energy field processing—laser microjet
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-01-07 |
| Journal | Zhongguo kexue. Wulixue Lixue Tianwenxue |
| Authors | Xizhao Lu, Kaiyong Jiang |
| Institutions | Huaqiao University, Xiamen University |
| Citations | 3 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThe research details the development and application of the Laser Microjet (LMJ), a compound energy field processing technique combining high-energy lasers with a stable, low-pressure deionized water microjet.
- Core Mechanism: The water microjet acts as an optical fiber, guiding the laser beam via Total Internal Reflection (TIR) to the workpiece. This mechanism enables flexible extension of the laser focus depth.
- Quality Enhancement: The water jet simultaneously provides cooling and mechanical stripping, drastically reducing the Heat Affected Zone (HAZ), microcracks, and recast layers, leading to superior verticality and inner wall quality compared to traditional laser processing.
- High Aspect Ratio Processing: LMJ significantly improves axial processing capability, achieving high-quality deep holes, slots, and seams with large aspect ratios (typically 10-100) in materials up to 25 mm thick.
- Beam Profile Modification: The coupling system changes the input Gaussian laser energy distribution into a more uniform flat-top profile, enhancing processing consistency over depth.
- Target Materials: Highly effective for hard, brittle, and heat-sensitive materials, including semiconductors (Si, SiC, GaAs), superhard alloys (PCD, cemented carbide), and low-k insulating materials.
- Key Technical Challenge: Successful operation relies critically on the precision of the laser-to-microjet coupling system, requiring high stability of the water jet (laminar flow) and alignment precision (approx. 2 ”m).
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Processing Thickness Range | 5-25 | mm | General application range |
| Deep Hole Aspect Ratio (L/D) | 10-100 | - | High quality deep holes/slots |
| Water Jet Pressure Range | 50-800 | bar | Stable microjet generation |
| Nozzle Diameter Range | 10-300 | ”m | Microjet size |
| Working Distance | 5-50 | mm | Flexible focus extension |
| LMJ Wavelengths | 1064, 532 | nm | Common Nd:YAG and frequency-doubled lasers |
| LMJ Pulse Duration | 20 | ”s | Microsecond regime (LMJ) |
| LMJ Pulse Energy | 9 | mJ | - |
| LMJ Fluence | 2.866 | J/cm2 | - |
| LMJ Peak Power | 450 | Wpeak | - |
| LMJ Repetition Rate | 2000 | Hz | - |
| Alignment Precision (Axial/Radial) | ~2 | ”m | Required for coupling mechanism |
| Optimal Coupling Water Layer Thickness | ~2 | mm | Minimizes Raman scattering loss |
| Typical Debris Particle Size Removed | ~1 | ”m | Slag and vaporized residue |
Key Methodologies
Section titled âKey MethodologiesâThe successful implementation of Laser Microjet (LMJ) processing relies on precise control over fluid dynamics and optical coupling:
- Laminar Microjet Generation: Deionized water is pressurized (50-800 bar) and forced through specialized nozzles (L/D > 10, smooth inner walls) to ensure stable, laminar flow. Jet stability is crucial, as turbulence disrupts Total Internal Reflection (TIR).
- Beam Shaping and Focusing: The input Gaussian laser beam is reshaped, often into a flat-top profile, using optical elements such as axicons or inverted telescope systems. This profile is necessary for uniform energy delivery over the extended focus depth.
- Total Internal Reflection (TIR) Coupling: The shaped laser beam is focused into the stable water microjet within a coupling chamber. The laser must strike the water-air interface at an angle greater than the critical angle to initiate TIR, allowing the water jet to act as an optical waveguide.
- Precision Alignment: Extremely high alignment accuracy (axial and radial precision < 2 ”m) is required between the laser focus point and the nozzle entrance to maximize coupling efficiency and minimize energy loss due to Raman scattering.
- Thermal and Debris Management: The continuous flow of the water jet provides active cooling to the processing zone, controlling thermal accumulation and limiting the HAZ. The jetâs mechanical impact strips away molten material, slag, and vaporized particles (approx. 1 ”m), ensuring a clean, continuously renewed processing surface.
- Process Parameter Optimization: Laser parameters (wavelength, pulse duration, frequency) and water jet parameters (pressure, flow rate) must be tuned based on the materialâs absorption characteristics and thickness to control the balance between thermal ablation and mechanical removal.
Commercial Applications
Section titled âCommercial ApplicationsâThe LMJ technology is primarily suited for high-value, high-precision micro-machining applications where minimizing thermal damage and achieving high aspect ratios are critical.
| Industry Sector | Specific Applications and Materials | Key Benefit |
|---|---|---|
| Semiconductors & Microelectronics | Dicing, scribing, and cutting of Si, 4H-SiC, GaAs, and InP wafers. Processing low-k insulating materials (PVD, CVD diamond). | Minimal microcracking, reduced HAZ, clean cuts, green processing (water removes toxic residues like As). |
| Aerospace & Turbine Manufacturing | Drilling high-quality, deep air film cooling holes in turbine blades (e.g., Ni-Ti alloys). | High aspect ratio (10-100) deep hole drilling with improved verticality and minimal recast layer. |
| Precision Tooling & Hard Materials | Cutting and structuring polycrystalline diamond (PCD), cubic boron nitride (CBN), and cemented carbide. Micro-grooving on precision alloy tool edges. | Effective processing of superhard, heat-sensitive materials with controlled fracture and reduced thermal stress. |
| Medical Devices | Precision cutting and structuring of complex shapes for medical stents (e.g., heart stents). | High precision, minimal thermal deformation required for biocompatible components. |
| Optoelectronics | Processing sapphire and ruby components (e.g., micro-holes in ruby elements). | High precision micro-machining of hard, brittle optical materials. |
| General Manufacturing | Cutting thick metal sheets (e.g., stainless steel, Ti6Al4V) and composite materials. | Increased cutting depth (up to 25 mm) and improved edge quality compared to conventional lasers. |
View Original Abstract
Laser microjet is a kind of compound energy field processing, which combined laser with microjet processing as well. While processing laser couples with stabilize pressure microjet and transfers internal total reflection until it arrives at workpieces surface, and changes the Gauss energy distribution to flat-topped laser beam, as well as cools and brushes the processing cross section. The stable low flow pressure deionized water jet waveguides cutting laser flexible extension processing focus, to improve the laser energy distribution while removing chips and cooling and enhance the axial processing quality and accuracy, and improves the laser axial processing ability. Talking about the research development of LMJ and the key technologies of LMJ equipment which including the angle of laser total reflect inner microjet, laser quality, laser transverse model, focal points, coupling precision of laser with nozzle and the stable work distance of microjet etc. At the same time, this processing method is introduced which is suitable for controlling the heat of laser processing, enhancing the direction of laser processing, high quality deep holes, slot and seam with large aspect ratio (about 10-100) as well. The object of the processing method gradually includes high value-added occasions of insulating materials, low- k materials, semiconductor, cemented carbide, such as SiC, GaAs, polycrystalline diamond and other photoelectrical materials.