Powder Bed Preheating for Low-Stress Laser Melting
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Solution Overview
Problem
Selective laser melting (SLM) processes face challenges with non-uniform heating, thermal stresses, and high energy requirements due to the instantaneous heating of small areas, leading to issues like thermal shock, deformation, and the need for extensive support structures, which increase costs and complexity.
Innovation Solution
The implementation of a heating lamp to preheat a larger area of the build materials to a temperature just below the melting point, reducing thermal gradients and energy requirements, using a controller to synchronize the heating lamp and laser beam to minimize overheating and sintering, and employing a system with a heating lamp and a laser source to control temperature and energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a high-power laser beam is used to instantaneously heat small areas to melting temperature, then melting and fusion of powder particles is achieved, but non-uniform heating and thermal stresses occur
Solution Approach 1:
The patent applies preliminary heating to a broad area of the powder bed before laser melting. This preheating step raises the baseline temperature of the powder particles in the build area, reducing the thermal gradient when the laser subsequently melts the material. The preliminary action of heating the entire area uniformly prevents the non-uniform heating and thermal stresses that would occur with direct laser melting alone.
2Manufacturing precision
If instantaneous heating of small areas is used, then selective melting is achieved, but thermal shock and deformation occur
Solution Approach 1:
The system performs preliminary heating of the powder bed to a temperature close to the melting point before applying the laser beam. This preheating reduces the temperature differential between the laser-heated zone and surrounding areas, minimizing thermal shock. The harmful thermal shock effect is mitigated by the prior uniform heating action that prepares the material to receive the laser energy more gradually.
3Strength
If high energy laser beam is used to melt powder particles, then fusion is achieved, but extensive support structures are required
Solution Approach 1:
By preheating the powder bed to near melting temperature, the material requires less additional energy from the laser to reach melting point. This reduces the peak energy density needed, allowing for more controlled melting with less reliance on extensive support structures to manage thermal stresses and provide mechanical support during the melting process.
4Productivity
If high-power laser beam is used for melting, then rapid processing is achieved, but high energy requirements increase costs
Solution Approach 1:
The preliminary heating step uses lower power over a broader area to raise the baseline temperature of the powder bed. This pre-conditioning reduces the energy required from the high-power laser subsequently, as less additional energy is needed to reach melting temperature. The total energy consumption is reduced while maintaining processing speed, because the preliminary heating prepares the material to require less intense laser energy.
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 reduces thermal stresses, minimizes energy needed for melting, allows for faster laser progression, and decreases post-processing costs by reducing the need for extensive support structures and improving the control over the 3D printing process.
Implementation Method 1
a heating lamp is to be apply light onto an area of a layer of build materials to heat the area to a temperature that is below but relatively near a melting temperature of the build materials
Implementation Method 2
a high-power laser beam is used to create three-dimensional parts or objects by melting together fine powder particles to each other and to surrounding portions of the powder particles
Implementation Method 3
The SLM process is an additive manufacturing process where a 3D object is built by addition of melted and fused layers of powder
Data Source
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AI summary
According to an example, an apparatus may include a heating lamp to illuminate and heat an area of a layer of build materials, in which the build materials may be one of a metallic and a plastic powder. The apparatus may also include a laser source to generate a laser beam and a controller to control the heating lamp to heat the build materials in the area of the layer of build materials to a temperature that is between about 100 C to about 400 C below a temperature at which the build materials begin to melt and to control the laser source to output a laser beam to melt the build materials in a portion of the heated area of the layer of build materials.