Copper Additive Manufacturing via Double Laser Sweep
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Solution Overview
Problem
Additive manufacturing of copper objects by powder bed deposition and selective fusion is hindered by copper's high reflectivity and thermal conductivity, which reduce energy transmission and heat retention, leading to low material density and poor fusion quality.
Innovation Solution
A method involving a double sweep of the laser beam over each powder layer, with the first sweep creating a nanoparticle film to reduce reflectivity and the second sweep fusing the powder, using a laser beam with a wavelength between 1030 nm and 1100 nm, and employing specific parameters for each sweep to enhance energy absorption and fusion quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper powder is used for additive manufacturing by powder bed deposition and selective fusion, then high electrical conductivity and thermal conductivity are achieved, but strong reflectivity reduces laser energy transmission and high thermal conductivity causes heat dissipation
Solution Approach 1:
The first sweep of the laser beam performs a preliminary action by creating a nanoparticle film on the copper powder surface before the actual fusion process. This nanoparticle film is formed by partial vaporization and condensation of copper during the first laser pass, and it serves to reduce reflectivity for the subsequent second sweep, thereby improving energy absorption during the fusion process
Solution Approach 2:
The strong reflectivity of copper, which initially harms the process by reducing laser energy absorption, is converted into a benefit through the double sweep method. The first sweep utilizes the reflective property to create a nanoparticle film that actually enhances absorption during the second sweep. The high thermal conductivity, which causes heat dissipation, is compensated by the intense localized heating from the second sweep that occurs quickly enough to overcome the conductive losses
2Reliability
If copper powder is used for additive manufacturing by powder bed deposition and selective fusion, then high electrical conductivity is achieved, but heat dissipation by conduction reduces fusion quality
Solution Approach 1:
The first laser sweep performs a preliminary action of creating a nanoparticle film and pre-heating the powder layer. This preparation step is crucial because it modifies the surface properties to enable better energy absorption during the second sweep, and it creates a temperature gradient that helps concentrate heat in the fusion zone despite copper's high thermal conductivity
Solution Approach 2:
The double sweep method implements periodic action by applying the laser beam in two distinct phases: the first sweep at lower power to create the nanoparticle film without complete fusion, and the second sweep at higher power to achieve proper fusion. This periodic application of energy allows the process to overcome the continuous heat dissipation caused by copper's high thermal conductivity
3Manufacturing precision
If a double sweep of laser beam is used over each powder layer, then material density greater than 99% is achieved, but process complexity increases
Solution Approach 1:
The fusion process is segmented into two distinct sweeps with different parameters. The first sweep operates at lower power with a larger spot size to create the nanoparticle film, while the second sweep uses higher power with a smaller spot size for precise fusion. This segmentation allows each sweep to be optimized for its specific function, achieving high density while keeping the overall process manageable through clear parameter differentiation
4Use of energy by moving object
If laser beam wavelength between 1030 nm and 1100 nm is used, then energy absorption is enhanced, but reflectivity reduction effectiveness varies
Solution Approach 1:
The laser wavelength is specifically changed to the 1030-1100 nm range, which corresponds to an absorption peak for copper. This parameter change, combined with the nanoparticle film creation, significantly enhances energy absorption. The nanoparticle film further modifies the optical properties by creating surface roughness and plasmonic effects that reduce reflectivity, and the specific wavelength range maximizes the interaction with these nanoparticles
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 allows for the production of copper objects with a material density greater than 99.6%, significantly improving the mechanical, electrical, and thermal conductivity characteristics by minimizing porosity and enhancing energy transfer during the fusion process.
Implementation Method 1
the first sweep of the laser beam allowing creation of a film of nanoparticles in the surface of the powder present in each fusion zone
Implementation Method 2
this nanoparticle film reduces the reflectivity of the powder in each fusion zone
Implementation Method 3
the second sweep of the laser beam fuses the powder in each fusion zone thanks to the presence of the nanoparticle film created by the first sweep
Implementation Method 4
enhancing energy absorption and fusion quality
Data Source
AI summary
A method for additive manufacturing of a copper object comprises manufacturing the object by selective fusion of powder layers superposed on a support, the selective fusion of a powder layer being obtained by the movement or sweeping of a laser beam over the powder layer, wherein the powder layer is metallic and comprises at least 95% by mass of copper. Each fusion zone of each powder layer is swept at least twice by the laser beam, the first sweep of the laser beam allowing creation of a film of nanoparticles in the surface of the powder present in each fusion zone, wherein this nanoparticle film reduces the reflectivity of the powder in each fusion zone, and the second sweep of the laser beam fusing the powder in each fusion zone due to the presence of the nanoparticle film created by the first sweep.