Spherical Polymer Particles via Extrusion Microgranulation
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Solution Overview
Problem
Current methods for producing thermoplastic polymer particles with sizes suitable for powder-based additive manufacturing, such as selective laser sintering, often result in irregularly shaped particles that do not meet the required size and spherical criteria, limiting their effectiveness in these processes.
Innovation Solution
A continuous extrusion process followed by a microgranulation process using a perforated plate with controlled temperature and vibration to produce spherical polymer particles with uniform sizes between 2 μm and 200 μm, ensuring the longest and shortest dimensions differ by no more than a factor of 2.5, and incorporating a cutter head for precise cutting of melt strands into microgranules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional methods (bead polymerization, emulsified milling, precipitation, grinding) are used to produce small polymer particles, then particle size requirements are met, but particle shape becomes irregular and spherical morphology is not achieved
Solution Approach 1:
The invention changes the physical-chemical parameters of the polymer melt by controlling temperature (maintaining above melting point through heated plates and insulation) and applying vibration (10-1000 Hz), which modifies the melt's flow and solidification behavior to produce spherical particles with uniform size distribution
Solution Approach 2:
Vibration is applied to the polymer melt at frequencies between 10-1000 Hz during extrusion through the perforated plate. This vibration prevents premature solidification, ensures uniform melt flow through all holes, and contributes to forming spherical particles with consistent dimensions
2Ease of manufacture
If plastic granules with diameter of 1 mm to 10 mm are used directly, then material is readily available, but particle size is too large for powder-based additive manufacturing processes
Solution Approach 1:
The continuous polymer melt stream is segmented into multiple individual strands as it passes through the perforated plate with multiple holes. Each hole produces a separate melt strand that is then cut into uniform microgranules, achieving particle sizes of 10 μm to 500 μm suitable for additive manufacturing
Solution Approach 2:
A perforated plate with precisely dimensioned holes serves as an intermediary device between the extrusion system and the final powder product. The plate geometry (hole diameter, spacing, arrangement) controls the segmentation and initial shaping of the melt into uniform strands that solidify into spherical particles
3Productivity
If a continuous extrusion process with perforated plate is used, then production efficiency is improved, but achieving spherical shape with uniform size becomes difficult without additional controls
Solution Approach 1:
The system transitions from static extrusion to dynamic extrusion with vibration applied at 10-1000 Hz. This dynamic approach allows continuous production while maintaining spherical particle morphology and uniform size by preventing premature solidification and ensuring consistent melt flow through the perforated plate throughout the continuous process
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 method effectively produces spherical polymer particles that are uniformly sized and shaped, enhancing their suitability for powder-based additive manufacturing processes by ensuring consistent particle size and spherical morphology, which improves the cohesion and accuracy of 3D printing outcomes.
Implementation Method 1
maintaining a temperature of the running plate above a melting point of the thermoplastic polymer(s) so that the thermoplastic polymer(s) do not solidify on the running plate
Implementation Method 2
A continuous extrusion process followed by a microgranulation process using a perforated plate with controlled temperature and vibration to produce spherical polymer particles
Implementation Method 3
A continuous extrusion process followed by a microgranulation process using a perforated plate with controlled temperature and vibration
Data Source
Figure 1
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AI summary
Method and associated apparatus for producing spherical polymer particles suitable as plastic powder for powder-based additive manufacturing processes, wherein the method according to the invention for producing spherical polymer particles with a particle size of 2 µm to 200 µm from thermoplastic polymers comprises a continuous extrusion process and a subsequent microgranulation process, wherein the microgranulation process is carried out with a mean exit velocity at the hole of 0.00000330 m/s to 3 m/s and a cutting frequency at the hole exit of 0.1 kHz to 16 kHz.