Dual-Stage Laser Scanner for Sharp-Turn Powder Bed Melting
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Solution Overview
Problem
Existing additive manufacturing technologies face challenges in achieving precise control over energy beam scanning in selective laser melting and sintering processes, leading to issues like warping, curling, and elongate melt pools due to limited dynamic response of galvanometers and excessive thermal loads, which affect the accuracy and detail of the solidified objects.
Innovation Solution
A scanner system utilizing a combination of beam steering components with different dynamic responses, where a faster dynamic response component compensates for the slower response of another, allowing for sharper changes in direction and reduced absorption of high-power laser beams, enabling more precise scanning strategies such as pulsed operation and 'hopping' of the energy beam across the powder bed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single beam steering component with large range of movement is used, then the energy beam can be scanned over a wide area, but the dynamic response is slow causing imprecise scanning paths
Solution Approach 1:
The beam steering system is segmented into two independent components: a first beam steering component (galvanometer) providing large angular deflection for wide scan area, and a second beam steering component (acousto-optic deflector) providing fast dynamic response for precise positioning. Each component operates in its optimal performance range to collectively achieve both wide coverage and high precision scanning
Solution Approach 2:
The second beam steering component acts as an intermediary that compensates for the limitations of the first component. The AOD provides rapid beam position adjustments between the coarser galvanometer positions, effectively mediating between the large-range but slow galvanometer and the precision requirement
2Productivity
If continuous mode laser operation is used, then the scanning process is continuous, but elongate melt pools are formed reducing detail accuracy
Solution Approach 1:
The laser operation is converted from continuous to pulsed mode, with pulses synchronized to the beam hopping sequence. This periodic action allows the material to cool between pulses, preventing elongate melt pool formation while maintaining scanning continuity through rapid beam repositioning between pulses
Solution Approach 2:
While the laser operates in pulsed mode, the useful action remains continuous through the hopping mechanism. The beam rapidly moves between exposure points in sequence, maintaining process continuity without forming excessive melt pools, as each pulse is precisely timed and positioned
3Reliability
If galvanometers are used for beam steering, then the system is simple and reliable, but the dynamic response is limited causing curved scan paths instead of sharp angular changes
Solution Approach 1:
The system merges the reliable galvanometer-based first beam steering component with the fast-response acousto-optic deflector second beam steering component. The galvanometer provides stable, reliable coarse positioning while the AOD adds fast response capability for sharp angular changes, combining the strengths of both systems
Solution Approach 2:
The second beam steering component replaces the mechanical galvanometer system with an acousto-optic deflector that uses sound waves to modulate the refractive index of a medium, thereby deflecting the beam. This non-mechanical approach eliminates the inertia and bandwidth limitations of mechanical galvanometers while maintaining system reliability through the complementary first beam steering component
4Productivity
If high-power laser beams are used, then the processing speed and efficiency increase, but the beam is absorbed causing overheating of beam steering components
Solution Approach 1:
The acousto-optic deflector serves as an intermediary that handles the high-power laser beam using sound wave modulation rather than mechanical reflection. This approach reduces direct absorption and overheating issues in the beam steering components, as the AOD uses acoustic fields to control the beam path with minimal energy loss to heat
Solution Approach 2:
The mechanical galvanometer system is supplemented with an acousto-optic deflector that uses acoustic fields instead of mechanical movement to steer the beam. This substitution reduces mechanical friction and heat generation, allowing high-power laser beams to be directed with minimal overheating of the steering components
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 enables the energy beam to be scanned along ideal paths, reducing thermal loads, improving the accuracy and detail of solidified lines, and allowing for the use of high-power lasers without overheating, thereby enhancing the precision and efficiency of the additive manufacturing process.
Implementation Method 1
movement of galvanometer-driven mirrors in a scanner
Implementation Method 2
deflecting the energy beam
Implementation Method 3
movement of acousto-optically-deflected energy beam
Implementation Method 4
laser beam melts or sinters the powder to form a solidified layer
Implementation Method 5
laser beam melts or sinters the powder
Implementation Method 6
laser beam melts or sinters the powder
Data Source
AI summary
An additive manufacturing apparatus including a scanner for directing a laser beam on to layers of flowable material to selectively solidify the material to form an object in a layer-by-layer manner. The scanner includes an optical component operable under the control of a first actuator to reflect the laser beam over a first range of angles in a first dimension and the or a further optical component operable under the control of a second actuator to reflect the laser beam over a second range of angles in the first dimension, wherein the second actuator provides a faster dynamic response but a smaller range of movement of the laser beam than the first actuator.