Dual-Pulse Laser Ablation for Variable Cross-Section Microholes
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Solution Overview
Problem
Current methods for forming non-straight microholes, such as those in diesel engine fuel injectors and aerospace cooling systems, face challenges in varying cross-sectional dimensions along the hole depth, particularly in both conductive and non-conductive substrates, due to limitations in existing techniques like EDM and ECM, which are inefficient and costly, and struggle with arbitrary diameter variations.
Innovation Solution
The dual-pulse laser ablation and plasma amplification (LAPA) process involves directing a first laser beam pulse to form a hole and generate a plasma plume with insufficient thermal energy, followed by a second pulse to amplify the plasma plume's temperature and expansion velocity, allowing controlled etching of the sidewalls to vary the cross-sectional dimensions of the hole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electrical discharge machining (EDM) or micro electrochemical machining (ECM) is used to drill reverse tapered microholes, then the microholes can be formed in conductive materials, but the process is limited to conductive materials only and has low efficiency
Solution Approach 1:
The patent replaces electrical discharge machining and micro electrochemical machining with laser beam technology. The laser beam system uses optical energy instead of electrical current to ablate material, enabling processing of both conductive and non-conductive materials while dramatically increasing drilling speed to hundreds of microholes per minute
Solution Approach 2:
The patent changes the fundamental processing parameter from electrical current (in EDM/ECM) to laser beam energy parameters (wavelength, pulse duration, fluence). By controlling laser parameters such as pulse width and energy density, the system achieves versatile material processing across conductive and non-conductive substrates with high efficiency
2Productivity
If a single laser beam pulse is used to drill microholes, then the process is simple and fast, but the cross-sectional dimensions cannot be controlled or varied along the hole depth
Solution Approach 1:
The patent segments the laser processing into two distinct pulse stages: a first high-energy pulse for rapid hole drilling, and a second lower-energy pulse for controlled sidewall ablation. This segmentation enables both high productivity in hole formation and precise control over cross-sectional dimensions at different depths
Solution Approach 2:
The first laser pulse performs preliminary action by creating the initial hole structure rapidly. Subsequently, the second pulse refines the hole geometry by selectively ablating sidewalls. This preliminary action approach separates the high-speed drilling function from the precision shaping function
3Manufacturing precision
If the plasma plume has high thermal energy to etch sidewalls effectively, then the cross-sectional dimensions can be modified, but the heat-affected zone increases and damages the substrate
Solution Approach 1:
The patent uses periodic pulsed laser action with two distinct pulse characteristics. The first pulse creates plasma for material removal, while the second pulse operates at different timing and energy levels to etch sidewalls. This periodic action with varying parameters achieves sidewall modification while limiting cumulative heat accumulation and heat-affected zone
Solution Approach 2:
The patent dynamically adjusts laser parameters between the two pulses, varying pulse energy, duration, and timing intervals. The first pulse uses higher energy for rapid ablation, while the second pulse uses optimized lower energy for controlled sidewall etching. This dynamic parameter adjustment maintains effective etching while minimizing thermal damage
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables the efficient and cost-effective formation of non-straight microholes with varying cross-sectional dimensions in both conductive and non-conductive substrates, improving fuel efficiency and cooling performance while maintaining high-quality sidewalls and minimizing heat-affected zones.
Implementation Method 1
directing a first laser beam pulse towards a substrate to form a hole in a surface thereof having a cross-sectional dimension at a location along a depth of the hole and to form a plasma plume at least partially within the hole wherein the plasma plume has insufficient thermal energy and expansion velocity to etch a sidewall of the hole
Implementation Method 2
directing a second laser beam pulse into the plasma plume to increase the temperature and expansion velocity of the plasma plume such that the sidewall is etched causing an increase in the cross-sectional dimension at the location in the hole
Implementation Method 3
increase the temperature and expansion velocity of the plasma plume such that the sidewall is etched
Data Source
AI summary
Methods capable of forming holes in, etching the surface of, or otherwise ablating substrates, and substrates formed thereby. A first method includes directing a first laser beam pulse towards a substrate to form a hole in a surface thereof and to form a plasma plume at least partially within the hole wherein the plasma plume has insufficient thermal energy and expansion velocity to etch sidewall of the hole, and directing a second laser beam pulse into the plasma plume to increase the temperature and expansion velocity of the plasma plume such that the sidewall is etched causing an increase in the cross-sectional dimension of the hole. A second method includes applying a liquid to a surface of a substrate, and directing a laser beam pulse into the liquid to create plasma on the surface of the substrate that etches portions of the surface of the substrate.