Selective Laser Melting Beam Steering for Continuous Scan Paths
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Solution Overview
Problem
Conventional additive manufacturing methods using galvanometer type scanners result in discontinuous scanning paths, leading to small areas of unmelted powder and stress risers in the finished part, which are difficult to address with continuous parametric scanning due to the need for precise multi-axis movements controlled by Cartesian coordinates.
Innovation Solution
A beam steering assembly incorporating rotatable Risley prisms, with a first and second wedge prism, allows for continuous parametric or non-linear scanning paths by controlling the relative and absolute rotational velocities and phase-offset of the optical elements, enabling the laser beam to be steered over the build surface without breaking the path into smaller X-Y movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional galvanometer type scanners are used for melting powder layers, then the scanning path can be controlled using Cartesian coordinates, but the scanning path becomes discontinuous resulting in unmelted powder areas and stress risers
Solution Approach 1:
The patent replaces the conventional galvanometer scanner with an acousto-optic modulator (AOM) and acousto-optic deflector (AOD) system. This substitution uses acoustic waves to control laser beam deflection, enabling continuous scanning paths without the mechanical limitations of galvanometer scanners. The acoustic field manipulation allows for smooth, continuous beam movement that eliminates unmelted powder areas and stress risers while maintaining precise control.
2Manufacturing precision
If continuous parametric scanning paths are attempted with conventional equipment, then scanning path continuity improves, but the system requires substantial and highly precise multi-axis movements which increases device complexity
Solution Approach 1:
The patent replaces complex mechanical multi-axis movement systems with an acousto-optic control system. The AOM and AOD use acoustic waves to deflect the laser beam, eliminating the need for substantial mechanical multi-axis movements. This acoustic field-based approach achieves continuous parametric scanning paths with simpler device architecture.
Solution Approach 2:
The patent changes the control parameter from mechanical position coordinates to acoustic frequency and amplitude parameters. By controlling the laser beam through acoustic wave modulation rather than mechanical movement, the system achieves continuous scanning paths while reducing device complexity. The acoustic parameters provide precise control without requiring complex mechanical systems.
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 eliminates unmelted powder and stress risers in the finished part by allowing integrated perimeter and core scanning, improving surface finish and dimensional accuracy without additional processing costs, while maintaining the structural integrity of the manufactured objects.
Implementation Method 1
an acousto-optic modulator to modulate an intensity of the laser beam
Implementation Method 2
an acousto-optic deflector to deflect the laser beam in response to a deflection pattern
Implementation Method 3
selectively melting the powder using a laser
Implementation Method 4
laser powder deposition apparatus... selectively melting the powder using a laser
Data Source
AI summary
An additive manufacturing apparatus comprises a laser beam generator, a build surface spaced apart from the laser beam generator, and first and second adjacent optical elements disposed along a beam travel path between the laser beam generator and the build surface. The first optical element is continuously rotatable about a beam steering axis and the second optical element is continuously rotatable about the beam steering axis independently of the first optical element.