Diode Laser Fiber Array for Powder Bed Fabrication
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Solution Overview
Problem
Direct Metal Laser Melting (DMLM) systems face challenges with rapid cooling rates that can lead to cracking of certain alloys and difficulties in achieving desirable grain growth during the additive manufacturing process, particularly in forming complex geometries like airfoils for gas turbine engines.
Innovation Solution
A diode laser fiber array is used to simultaneously melt powder layers in a powder bed, with controlled laser beams and optical fibers, allowing for rapid melting times and precise control over cooling rates and grain structure through preheating and power management, enabling the formation of directionally solidified and single crystal structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam is used to scan a layer of powder to sinter and melt the desired shape, then the component can be fabricated layer by layer, but the scanning time per layer is long (70-100 seconds) and the build process can require days of processing time
Solution Approach 1:
The laser source is divided into multiple independent laser beams arranged in an array, where each beam can independently target and process different regions of the powder bed simultaneously. This segmentation of the processing function allows parallel operation across multiple zones, dramatically increasing the build rate while maintaining geometric precision through individual beam control.
Solution Approach 2:
Multiple laser beams are combined into a single processing system that operates simultaneously on different portions of the powder bed. By merging multiple light sources into one integrated array structure, the system achieves both high productivity through parallel processing and maintains manufacturing precision through coordinated control of all beams.
2Productivity
If a high-power laser is used to melt the powder rapidly, then the build time is reduced, but rapid cooling rates can lead to cracking of certain alloys and difficulties in obtaining desirable grain growth
Solution Approach 1:
The powder bed is preheated to an elevated temperature before the laser melting process begins. This preliminary thermal preparation reduces the temperature differential between the molten pool and surrounding material, thereby reducing cooling rates and preventing thermal shock-induced cracking while still allowing rapid melting when the laser activates.
Solution Approach 2:
The thermal parameters of the processing environment are changed by maintaining an elevated base temperature of the powder bed. This parameter modification transforms the cooling rate profile from rapid to controlled, preventing alloy cracking and enabling desirable grain growth patterns while preserving high melting speeds through efficient heat retention.
3Manufacturing precision
If the laser scans across the powder bed to form band-shaped exposed regions, then the powder can be selectively fused, but the constant speed scanning results in rapid cooling rates that prevent desirable grain growth normal to the layer surface
Solution Approach 1:
The powder bed is preheated before laser processing to establish a thermal environment that promotes controlled cooling. This preliminary thermal conditioning ensures that when the laser creates band-shaped exposed regions, the surrounding hot powder acts as a thermal reservoir, enabling desirable grain growth normal to the layer surface while maintaining precise layer fusion.
Solution Approach 2:
The problem transitions from a one-dimensional scanning approach to a two-dimensional array of simultaneous laser sources. By distributing multiple laser beams across the powder bed surface, the system creates overlapping melt zones that extend vertically into the powder, promoting grain growth normal to the layer surface while maintaining precise fusion control through coordinated beam operation.
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 significantly reduces melting time by two orders of magnitude, prevents cracking, and allows for controlled grain growth, enabling the efficient fabrication and repair of complex components like airfoils with improved structural characteristics.
Implementation Method 1
directs laser beams from the optical fibers into a powder bed
Implementation Method 2
simultaneous melting of all of the desired powder in a layer
Implementation Method 3
A plurality of optical fibers are provided in a bundle between the diode laser array and the free ends thereof
Implementation Method 4
control the cooling rate of a melted region to enable directional solidification and single crystal formation
Implementation Method 5
control the cooling rate of a melted region to enable directional solidification and single crystal formation
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A method of forming a build in a powder bed includes emitting a plurality of laser beams from selected fibers of a diode laser fiber array onto the powder bed, the selected fibers of the array corresponding to a pattern of a layer of the build; and simultaneously melting powder in the powder bed corresponding to the pattern of the layer of the build. An apparatus for forming a build in a powder bed includes a diode laser fiber array including a plurality of diode lasers and a plurality of optical fibers corresponding to the plurality of diode lasers, each optical fiber configured to receive a laser beam from a respective diode laser and configured to emitting the laser beam; a support configured to support a powder bed or a component configured to support the powder bed at a distance from ends of the optical fibers; and a controller configured to control the diode laser fiber array to emit a plurality of laser beams from selected fibers of the diode laser fiber array onto the powder bed, the selected fibers of the array corresponding to a pattern of a layer of the build and simultaneously melt the powder in the powder bed corresponding to the pattern of the layer of the build.