Pulse-Modulated Additive Layer Fabrication for Distortion Control
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Solution Overview
Problem
Selective laser melting with continuous wave lasers struggles to produce near-net-shape components with close tolerances and high-quality surface finishes, and experiences excessive substrate distortion due to thermal gradients and residual stresses.
Innovation Solution
The use of a pulse-modulated laser beam allows for precise control of heat application, enabling the formation of thinner layers near the substrate and thicker layers further away, reducing distortion by minimizing the number of laser traverses and employing a combination of continuous wave and pulsed laser modes to distribute heat evenly.
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 laser operates in pulsed mode with controlled pulse duration, frequency, and duty cycle to melt powder selectively while avoiding excessive heat accumulation. This periodic action enables precise control of material deposition with layer thicknesses as low as 10μm, achieving near-net-shape components with close tolerances and high surface finish quality while maintaining efficient build rates.
2Productivity
If continuous wave laser is used for selective laser melting, then high material deposition rate is achieved, but substrate distortion increases
Solution Approach 1:
The patent employs periodic pulsed laser operation to deliver heat in controlled intervals rather than continuously. By adjusting pulse frequency and duty cycle, the system allows heat dissipation between pulses, reducing thermal gradient accumulation and compressive plastic yielding in the substrate. This approach maintains high deposition rates while minimizing weld distortion and residual stress-induced buckling.
Solution Approach 2:
The patent applies preliminary heating or pre-melting of the substrate surface before powder deposition. This preliminary action ensures uniform heat distribution and reduces thermal shocks that cause distortion. The laser pre-treats the substrate area where powder will be deposited, creating a controlled thermal field that minimizes subsequent distortion during the main melting process.
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 reduces substrate distortion, achieves finer layer thickness control, and enhances surface finish quality, allowing for the production of complex geometries and reducing manufacturing time while maintaining structural integrity.
Implementation Method 1
a laser beam is used to melt a controlled amount of powdered (usually metallic) material on a substrate
Implementation Method 2
In selective laser melting 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
Modulating the laser beam pulse enables the amount of heat applied to the powder to be accurately and precisely controlled
Implementation Method 4
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 5
the substrate thus is subjected to intense localised heating, creating steep thermal gradients between the molten material and the cold material further away
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.