Powder Bed Fusion Pulse Profiles for Beam Steering Inertia
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Solution Overview
Problem
In powder bed fusion, achieving precise control over energy beam exposure, particularly in pulsed mode, is challenging due to inertia in beam steering components, leading to incomplete melting and defects in the final product.
Innovation Solution
The method involves commanding an energy beam source to produce pulses with specific power levels and shapes, including non-rectangular pulse profiles with controlled rise and fall times, to improve material consolidation and reduce defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pulsed exposure is used to improve material consolidation control, then manufacturing precision is improved, but beam positioning accuracy deteriorates due to beam steering component inertia
Solution Approach 1:
The patent applies periodic pulsed exposure instead of continuous scanning. The energy beam is delivered in discrete pulses at predetermined positions, allowing the powder to be melted and consolidated between pulses. This periodic action decouples the beam positioning requirement from continuous motion, reducing the impact of steering component inertia on positioning accuracy while maintaining precise material consolidation control through controlled pulse timing and duration.
2Device complexity
If continuous scanning is used to maintain simple beam control, then device complexity is reduced, but manufacturing precision deteriorates due to incomplete melting and defects
Solution Approach 1:
The patent implements periodic pulsed exposure where the energy beam is delivered in controlled pulses rather than continuous scanning. Each pulse is timed to deliver sufficient energy to completely melt the powder at the target position, with intervals allowing for heat distribution and consolidation. This approach maintains relatively simple beam control mechanisms while significantly improving melting completeness and reducing defects through optimized pulse parameters.
Solution Approach 2:
The patent changes the temporal parameters of energy beam delivery by using pulsed exposure with specific pulse widths, frequencies, and duty cycles. These parameter changes allow sufficient energy delivery for complete melting while managing heat accumulation and distortion. The pulse parameters are optimized to balance between delivering enough energy for complete melting and avoiding excessive heat input that could cause defects.
3Manufacturing precision
If pulse duration is extended to improve material consolidation, then manufacturing precision is improved, but productivity deteriorates due to longer exposure time
Solution Approach 1:
The patent uses periodic pulsed exposure with optimized pulse durations that are long enough to achieve complete melting and good material consolidation, but short enough to maintain acceptable build rates. The pulse frequency and duty cycle are tuned to deliver the necessary energy for quality consolidation while minimizing the total exposure time. Multiple pulses may be used at each position with decreasing energy levels to achieve thorough consolidation without excessive heat input that would slow down the 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 results in improved material properties, such as reduced solidification cracking and enhanced microstructure homogeneity, by controlling the cooling rate and melt pool dynamics.
Implementation Method 1
The energy beam melts the powder to form a solidified layer
Implementation Method 2
an energy beam, such as a laser or electron beam, is scanned across portions of the powder layer
Data Source
AI summary
A powder bed fusion additive manufacturing method including exposing layers of a powder bed to an energy beam to selectively melt at least one area of each layer, wherein the energy beam is progressed along a scan path to melt material of the at least one area using a pulsed exposure. Initial and/or end pulses of the pulsed exposure may have a shorter pulse duration than a pulse duration of a mid-pulse between the initial and end pulses.