Axicon Bessel Beam Optics for Stable Direct Metal Laser Melting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional direct metal laser melting (DMLM) machines face challenges in maintaining a consistently sized laser spot across the powder bed due to mechanical variations, temperature changes, and imprecise build plate movements, requiring frequent calibration and adjustments to ensure build quality.
Innovation Solution
The use of a non-diffracting Bessel beam profile generated by superposing collimated beams with axicon optical elements, which provides a stable energy distribution insensitive to positional variations and eliminates the need for extensive calibration, using right circular prisms or axicon lenses to create an optimal peak-to-sidelobe intensity ratio for uniform powder melting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional spherical optics are used to focus laser energy to a Gaussian beam shape, then the laser spot can be focused to a small size, but the stable focal region is limited to only a few millimeters in the beam propagation direction
Solution Approach 1:
The patent changes the optical parameter from conventional spherical focusing to axicon-based Bessel beam generation. This transforms the beam profile from Gaussian with a short waist (2-5mm) to a non-diffracting Bessel beam with an extended stable region (100-500mm), fundamentally altering the focal characteristics to resolve the contradiction between precision and length.
Solution Approach 2:
The patent replaces the mechanical dynamic optics system (movable lenses and mirrors for continuous refocusing) with a static axicon optical element that inherently generates a long-depth-of-field Bessel beam. This substitution eliminates the need for mechanical adjustment mechanisms while achieving the desired extended focal stability.
2Reliability
If dynamic optics are used to refocus the laser beam during scanning, then the focus spot can be maintained on the powder bed, but the system requires frequent calibration and adjustment due to mechanical variations and temperature changes
Solution Approach 1:
The patent extracts and removes the dynamic refocusing subsystem (movable optics, focus control mechanisms) from the system. By using a static axicon element that inherently produces a long-depth-of-field Bessel beam, the system eliminates the components that cause mechanical variations and calibration requirements, thereby improving reliability while reducing complexity.
Solution Approach 2:
The Bessel beam generated by the axicon is self-correcting and maintains its focal properties over a long depth range without requiring active control or calibration. The beam's non-diffracting nature provides inherent stability that is insensitive to mechanical variations and temperature changes, making the system self-regulating.
3Manufacturing precision
If conventional Gaussian beam focusing is used, then the laser energy can be concentrated to a small spot, but extensive calibration and adjustment are required to maintain build quality across the powder bed
Solution Approach 1:
The axicon-generated Bessel beam provides self-calibrating properties with an extended depth of field (100-500mm) that maintains consistent focal characteristics across the entire powder bed without requiring calibration files or manual adjustments. This eliminates the time-consuming calibration process while ensuring uniform build quality.
Solution Approach 2:
The static axicon optical element serves multiple functions simultaneously: it generates the Bessel beam profile, provides extended depth of field, and ensures uniform energy distribution across the powder bed. This multi-functionality in a single component eliminates the need for separate calibration systems and dynamic adjustment mechanisms.
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 solution ensures uniform energy distribution across the build plate, reduces thermal gradients, prevents cracking in alloys, and decreases maintenance costs by eliminating the need for focusing systems, resulting in increased throughput and improved weld quality.
Implementation Method 1
a non-diffracting Bessel beam profile generated by superposing collimated beams with axicon optical elements
Implementation Method 2
generated by superposing collimated beams with axicon optical elements
Implementation Method 3
laser energy to fuse successive layers of powder bed material
Implementation Method 4
laser energy to fuse successive layers of powder bed material
Data Source
AI summary
A system includes a first group of optic lenses within a focusing unit positioned along the propagation direction of a collimated laser beam, the first group of optic lenses separated by a predetermined fixed distance. The first group of optic lenses in conjunction cause the collimated beam to form as an annular beam as it passes through the first group of optic lenses. An axicon lens located distal from the first group of optic lenses along the propagation direction, the axicon lens operable to bifurcate the annular beam into two deflected collimated beam sections, and the axicon lens having a focus that causes the two deflected collimated beam sections to merge at a distance distal from the axicon lens to create an interference pattern region.