Composite Polymer Powder Mix for Curling-Stable Selective Sintering
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Solution Overview
Problem
Existing selective sintering processes for manufacturing three-dimensional objects using thermoplastic polymer materials face issues such as high crystallinity, curling, and warpage due to the addition of reinforcement materials, which increase crystallization tendency and reduce process reliability and efficiency.
Innovation Solution
A powder mixture comprising a first thermoplastic polymer material with reinforcement material and a second thermoplastic polymer material without reinforcement, optimized to have specific bulk density and BET surface area ranges, to reduce crystallization and curling, and enhance mechanical properties and process stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If reinforcement material is added to thermoplastic polymer powder to improve mechanical properties, then strength and stiffness are enhanced, but crystallization tendency increases leading to high crystallinity, curling, and warpage
Solution Approach 1:
The patent uses a composite powder mixture combining reinforced polymer particles (first powder) with unreinforced polymer particles (second powder). This composite approach allows the reinforced particles to provide mechanical strength while the unreinforced particles act as a matrix that reduces overall crystallization tendency, thereby preventing curling and warpage while maintaining enhanced mechanical properties
Solution Approach 2:
The patent optimizes specific parameters of the powder mixture including bulk density (0.3-0.7 g/cm³) and BET surface area (2-10 m²/g). By controlling these parameters, the patent achieves a balance between particle packing efficiency and surface area for sintering, which manages the crystallization process to reduce curling while maintaining mechanical strength from the reinforcement material
2Strength
If reinforcement material is added to enhance mechanical properties, then strength improves, but curling and warpage increase reducing manufacturing precision
Solution Approach 1:
The mixture of reinforced and unreinforced powder particles creates a composite structure where the unreinforced particles serve as a constraint matrix that limits the curling behavior of reinforced particles during crystallization, thereby maintaining dimensional stability while preserving mechanical strength enhancements
Solution Approach 2:
The patent creates local quality variation within the powder bed by distributing reinforced particles among unreinforced particles. This local distribution allows regions with reinforcement to provide strength while adjacent regions with unreinforced particles provide dimensional stability and reduce overall warpage
3Reliability
If laser power and exposure time are increased to improve sintering quality, then layer bonding improves, but energy consumption increases and processing speed decreases
Solution Approach 1:
The patent optimizes the laser sintering parameters (power, speed, exposure time) based on the specific bulk density and BET surface area of the powder mixture. By tailoring these parameters to the optimized powder characteristics, the patent achieves effective layer bonding with reduced energy input compared to conventional sintering parameters
Solution Approach 2:
The patent applies selective sintering where only the necessary portions of each powder layer are exposed to laser energy based on the digital model. This partial action approach, combined with the optimized powder properties, achieves adequate bonding without excessive energy input that would be required if uniform over-sintering were applied
4Reliability
If sintering temperature is increased to reduce crystallinity, then curling decreases, but energy consumption increases and cooling time increases reducing productivity
Solution Approach 1:
The composite powder mixture inherently reduces crystallization tendency through the interaction between reinforced and unreinforced particles, allowing sintering at lower temperatures that maintain adequate curling control while reducing energy consumption and cooling time compared to sintering fully reinforced powder
Solution Approach 2:
The patent determines optimal sintering temperature based on the powder mixture's bulk density and BET surface area characteristics. This parameter optimization enables effective sintering at temperatures that balance curling control with reduced energy input and faster cooling cycles, thereby improving productivity
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
The powder mixture achieves improved mechanical properties, reduced curling and warpage, and increased process window, resulting in safer and more efficient additive manufacturing with better dimensional stability and refreshment rates.
Implementation Method 1
manufacturing a three-dimensional object by solidifying the building material layer by layer at the positions corresponding to the cross-section of the three-dimensional object in the respective layer, in particular by exposure to radiation
Implementation Method 2
The mechanical properties of the manufactured object can be influenced by suitable choice of polymer in the raw material... the crystallisation tendency of the thermoplastic polymer materials
Implementation Method 3
an irradiation device in the form of a laser 7 is arranged above the working plane 6, which emits a directed light beam 8
Data Source
AI summary
Powder mixture for the use as building material in additive manufacturing processes, wherein the powder mixture includes a first powder having powder particles of a first thermoplastic polymer material, and a reinforcement material that is at least partially embedded in the powder particles of the first powder and/or adhered to the surface of the powder particles of the first powder. The second powder includes powder particles of a second thermoplastic polymer material which is the same as or different from the first thermoplastic polymer material. The powder particles of the second powder do not include the reinforcement material or include it only in an amount of at most 50% by weight relative to the amount of the reinforcement material in or on the powder particles of the first powder.