Pulsed Laser Layer Fabrication for Precision and Low Distortion
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Solution Overview
Problem
Selective laser melting using continuous wave lasers struggles to produce near-net-shape components with close tolerances and high-quality surface finishes, and is prone to substrate distortion due to thermal gradients and residual stresses.
Innovation Solution
The method employs a pulsed laser beam to control layer thickness and power distribution, with initial layers formed thicker than subsequent layers to reduce distortion, and combines pulsed and continuous wave laser techniques to achieve precise control over layer formation and surface finish.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous wave laser is used for selective laser melting, then high material deposition rate is achieved, but manufacturing precision and surface finish quality deteriorate
Solution Approach 1:
The patent applies periodic pulsed laser action instead of continuous wave laser. The pulsed laser delivers energy in discrete time intervals, allowing precise control of heat input and material melting. This periodic action enables both high deposition rates during pulse peaks and precise dimensional control during pulse valleys, resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The patent dynamically adjusts laser parameters including pulse duration, peak power, and duty cycle during the additive manufacturing process. This dynamic control allows the system to optimize between high deposition rates and precise surface finish quality by varying operational parameters in real-time based on processing requirements.
2Productivity
If continuous wave laser is used for selective laser melting, then high material deposition rate is achieved, but substrate distortion increases due to thermal gradients and residual stresses
Solution Approach 1:
The pulsed laser delivers energy in periodic bursts rather than continuously, creating intermittent heating cycles. This allows thermal diffusion between pulses, reducing cumulative thermal gradients and residual stresses in the substrate. The periodic action maintains high deposition rates during pulses while minimizing distortion through cooling intervals.
Solution Approach 2:
The patent employs preliminary heating of the substrate before material deposition begins. This pre-heating reduces the thermal shock and minimizes thermal gradients during subsequent layer deposition, thereby reducing substrate distortion while maintaining efficient material deposition rates.
3Manufacturing precision
If layer thickness is reduced to improve precision, then manufacturing precision improves, but manufacturing time increases
Solution Approach 1:
The pulsed laser enables precise control of layer thickness through modulation of pulse parameters. By adjusting pulse duration, peak power, and repetition rate, the system can deposit thin layers with high precision while maintaining efficient processing speeds. The periodic energy delivery allows complete melting and fusion at each layer without excessive heat accumulation, enabling fast processing of precise layers.
Solution Approach 2:
The patent changes laser parameters including pulse width, peak power, and duty cycle to optimize layer deposition. These parameter changes allow the system to achieve both thin layer precision and high deposition rates by finding optimal parameter combinations that balance thermal input with material melting efficiency.
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 approach allows for the production of finely detailed three-dimensional structures with reduced substrate distortion, improved surface finish, and increased manufacturing efficiency by modulating laser pulse power and traverse speed, enabling the creation of layers as thin as 10µm and reducing thermal stress-induced buckling.
Implementation Method 1
applying heat to powdered material by means of a laser beam so as to fuse it into a layer on a substrate or on a previously formed layer wherein the laser beam is a pulsed laser beam
Implementation Method 2
a laser beam is used to melt a controlled amount of powdered (usually metallic) material on a substrate, so as to form a layer of fused material thereon
Implementation Method 3
the laser beam creates a weld pool into which the powdered material is deposited, in a similar manner to which a welder manually adds filler wire to a weld pool created in conventional electric arc welding processes
Implementation Method 4
The invention provides in a first aspect a method of fabricating an object comprising applying heat to powdered material by means of a laser beam so as to fuse it into a layer on a substrate or on a previously formed layer wherein the laser beam is a pulsed laser beam, and the thickness and/or width of the layer is controlled by modulating the laser beam pulses
Data Source
Figure 1~2(b)
Figure 3(a)~4
Figure 5(a)~6(d)
AI summary
A selective layer melting or other additive layer fabrication method in which powdered material is fused by heating it with a pulsed laser, the pulses being modulated whilst the laser is traversing the substrate so as to control the thickness and/or width of the layer being formed. Initial layers of the fabrication structure may be formed more thickly than subsequent layers, e.g. by means of a CW laser,to reduce distortion. This aspect of the invention may be employed independently of the use of a pulsed laser to form the subsequent layers.