Pre-Fusion Laser Sintering to Stabilize Metal Powder Beds
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Solution Overview
Problem
In additive manufacturing systems, thermally driven turbulence in the powder bed leads to inconsistent layer formation due to powder or liquid loss from melt pools, resulting in inconsistent alloy composition and potential flaws like porosity.
Innovation Solution
A dual-beam approach is employed, where a low energy directed energy beam sinters the top surface of the powder layer to form a 'skull' layer, preventing powder loss, while a high energy beam creates molten pools for solidification, ensuring a consistent powder bed before melting, and repeating this process layer by layer to stabilize the powder bed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high energy directed energy beam is used to create molten pools for rapid solidification, then manufacturing precision and layer-by-layer fabrication control are improved, but powder loss and inconsistent layer formation occur due to thermally driven turbulence
Solution Approach 1:
A low energy directed energy beam is applied before the high energy beam to preheat and stabilize the powder bed in the melt pool region. This preliminary action reduces thermally driven turbulence and prevents powder loss before the high energy beam creates the molten pool for rapid solidification.
Solution Approach 2:
The low energy directed energy beam acts as an intermediary between the high energy beam and the powder bed. It prepares the powder bed by reducing turbulence and stabilizing the surface, creating favorable conditions for the subsequent high energy beam processing without directly forming the molten pool.
2Productivity
If a high energy directed energy beam is used to melt powder rapidly, then productivity and fabrication speed are improved, but alloy composition consistency deteriorates due to powder or liquid loss
Solution Approach 1:
The low energy beam is applied in advance to stabilize the powder bed and reduce turbulence before the high energy beam creates the molten pool. This preliminary stabilization prevents powder loss and ensures consistent alloy composition during rapid fabrication.
Solution Approach 2:
The system uses two different energy beam parameters (low energy and high energy) in sequence. The low energy beam changes the thermal state of the powder bed to reduce turbulence, while the high energy beam maintains rapid melting and solidification for high productivity. This parameter switching resolves the contradiction between speed and composition consistency.
3Manufacturing precision
If a focused laser beam is used to selectively melt powder in small localized regions, then manufacturing precision is improved, but thermally driven turbulence causes powder loss from melt pools
Solution Approach 1:
Before the focused high energy laser beam creates the small localized melt pool, a low energy beam is applied to the same region to reduce thermally driven turbulence. This preliminary action prevents powder loss while maintaining the precision of localized melting.
Solution Approach 2:
The heating process is segmented into two distinct stages: first, low energy beam application to stabilize the powder bed and reduce turbulence; second, high energy beam application to create the localized melt pool. This segmentation allows each stage to optimize its function without interfering with the other.
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 method stabilizes the powder bed, reducing powder loss and turbulence, resulting in a more consistent and homogeneous alloy composition with reduced porosity and imperfections in the final product.
Implementation Method 1
heating firstly a first region of a top surface of the first layer with a low energy directed energy beam with a first diameter to a temperature at which the metal powder at or near the top surface is sintered to form a first skull on the first layer
Implementation Method 2
heating secondly a first spot of the first region to a temperature at or above the melting point of the metal powder with a high energy directed energy beam with a second diameter smaller than the first diameter to form a first molten pool
Data Source
AI summary
In an embodiment, an apparatus for forming a metal component from alloy powder includes a powder-based layer-by-layer directed energy beam additive manufacturing system, a primary directed high energy beam, configured to raise a temperature of the alloy powder to or above the melting point of the alloy powder. A secondary directed low energy beam configured to raise the temperature of the alloy powder to or above a sintering point of the alloy powder without reaching the melting point of the alloy powder. The apparatus further includes a sintered region on the surface of an alloy powder layer previously produced by the secondary directed low energy beam and a solid region forming a portion of the metal component that was solidified from a molten pool on the surface of the alloy powder layer adjacent to the first sintered region having been produced by the primary directed high energy beam.