Polymer Powder Additive Selection for Laser Sintering
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Solution Overview
Problem
In additive manufacturing, the addition of functional additives and fillers to polymer powders for selective laser sintering often leads to a reduction in the temperature window, poor z-bonding of layers, and increased distortion due to their nucleating effects, which are particularly problematic when using near-infrared (NIR) radiation.
Innovation Solution
A plastic powder comprising a mixture of polymer-based particles and a particulate carbon additive, such as graphite or carbon black, is used, where the additive is selected to minimize the increase in crystallization point by no more than 2.5°C, thereby maintaining a stable process window and reducing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If functional additives and fillers are added to polymer powders for selective laser sintering, then the absorption of NIR radiation is improved, but the crystallization point increases significantly, narrowing the process temperature window
Solution Approach 1:
The patent changes the particle size parameter of the carbon additive, using ultrafine particles (0.5-5 μm) instead of conventional larger particles. This parameter change allows the carbon additive to absorb NIR radiation effectively while minimizing its nucleating effect on polymer crystallization, thus maintaining a wider process temperature window
Solution Approach 2:
The patent creates a composite powder system combining polymer particles with ultrafine carbon additives. This composite approach allows the carbon particles to serve as NIR absorbers without significantly increasing the crystallization point, as the ultrafine particles have reduced nucleating effects compared to larger particles
2Use of energy by moving object
If functional additives and fillers are added to polymer powders, then the energy absorption is enhanced, but the z-bonding of layers deteriorates
Solution Approach 1:
By changing the particle size parameter to ultrafine (0.5-5 μm), the carbon additives become more uniformly distributed and better embedded in the polymer matrix, improving interlayer bonding while maintaining energy absorption capabilities
3Use of energy by moving object
If functional additives and fillers are added to polymer powders, then the energy absorption is improved, but the component distortion increases
Solution Approach 1:
The ultrafine particle size (0.5-5 μm) reduces the nucleating effect on polymer crystallization, leading to more uniform crystallization behavior and reduced internal stresses during cooling, thereby minimizing component distortion while maintaining effective NIR absorption
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 significantly limits the negative influences of additives on the laser sintering process, improving the layer connection and component quality, allowing for efficient NIR laser sintering without adverse effects on the manufacturing process or the final product.
Implementation Method 1
a method for producing a three-dimensional object can be carried out layer by layer by selective sintering using electromagnetic radiation
Implementation Method 2
regions of a respective powder layer are selectively melted and resolidified
Implementation Method 3
the crystallization point of the mixture of the polymer-based particles and the particulate additive is increased by no more than 2.5°C
Implementation Method 4
for the absorption of energy applied during melting, functional additives, fillers, reinforcing fibers, and/or auxiliaries can be added to polymer-based materials
Data Source
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AI summary
Polymer powder for use as build material for additive manufacturing of a three-dimensional object by selective solidification of the build material at the site corresponding to the cross section of the three-dimensional object in the respective layer, especially by the action of radiation, wherein the polymer powder comprises a mixture of polymer-based particles and particles of a particulate additive and wherein the particulate additive is selected such that the crystallization point of the mixture of the polymer-based particles and the particulate additive is essentially not elevated compared to the crystallization point of a mixture of the polymer-based particles without the particulate additive.