Co-rotating Multi-Screw Extruder with 2.5 Speed Ratio
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Solution Overview
Problem
Conventional co-rotating twin-screw extruders face issues with material instability due to separate channels, high energy consumption, and inefficient mixing and melting, which are exacerbated by constant channel volume and symmetric screw geometry, leading to degradation of materials and reduced output.
Innovation Solution
A co-rotating self-cleaning multi-screw extruder with a speed ratio of 2.5, featuring a quintuple-threaded center screw and double-threaded peripheral screws, where the peripheral screws rotate 2.5 times faster and intermittently mesh, creating periodic and intermittent actions that enhance mixing and melting, while maintaining self-cleaning functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multi-threaded screws are used to generate separate channels for mixing, then mixing effect is improved, but material stability deteriorates because materials in different channels cannot mix
Solution Approach 1:
The patent employs nested screw structures where multiple screws with different thread counts (e.g., 3-threaded, 4-threaded, 5-threaded screws) are arranged concentrically. The peripheral screws with different thread configurations create varying numbers of channels that interact through controlled meshing, allowing materials to experience both channel separation and periodic mixing. This nested arrangement enables simultaneous achievement of material stability through consistent channel flow and mixing effect through periodic channel interaction.
2Ease of operation
If kneading block sections are used to mix materials from different channels, then mixing is achieved, but energy consumption increases and self-cleaning function deteriorates
Solution Approach 1:
The patent utilizes periodic meshing and non-meshing actions between peripheral screws with different thread counts. During meshing phases, materials from different channels are mixed; during non-meshing phases, channels remain separate. This periodic action eliminates the need for continuous high-shear kneading blocks, reducing energy consumption while maintaining mixing capability through intermittent channel interaction.
3Ease of operation
If open spaces are provided between screws to enhance mixing, then mixing between different screws is improved, but self-cleaning function is compromised
Solution Approach 1:
The patent employs dynamic meshing where peripheral screws periodically contact and separate. During contact phases, screws wipe against each other to maintain self-cleaning; during separation phases, open spaces allow material exchange and mixing. This dynamic configuration enables both mixing enhancement and self-cleaning functionality without requiring permanent open spaces or additional cleaning mechanisms.
4Ease of manufacture
If constant channel volume is maintained in symmetric screw geometry, then manufacturing is simplified, but melting and mixing efficiency decreases
Solution Approach 1:
The patent introduces asymmetric elements through peripheral screws with different thread counts (e.g., 3-threaded, 4-threaded, 5-threaded) while maintaining overall geometric symmetry for manufacturability. The asymmetric thread configurations create varying channel volumes and flow patterns that enhance melting and mixing efficiency, while the base geometric symmetry preserves manufacturing simplicity.
5Ease of operation
If high rotation speed is applied to achieve high shear rate, then mixing intensity is improved, but energy consumption increases and material degradation occurs
Solution Approach 1:
The patent segments the mixing function across multiple peripheral screws with different thread counts rather than relying on a single high-speed screw. This segmentation distributes the mixing intensity across multiple lower-speed components, reducing overall energy consumption and minimizing material degradation while achieving comparable or superior mixing effectiveness through cumulative shear actions.
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 design effectively stabilizes material mixing, reduces energy consumption, and improves melting and mixing efficiency by introducing elongational forces and topological chaos, achieving high output and dispersive mixing without the need for kneading blocks.
Implementation Method 1
taking full advantages of mutual mixing between screws, the action of the elongational force field, and periodic and intermittent action to improve the processing and mixing efficiency of materials
Implementation Method 2
The surface of the center screw and the surfaces of peripheral screws are always in contact in the extruder of this structure during the rotation process of the screw mechanism, which can achieve the self-cleaning function
Data Source
AI summary
A co-rotating self-cleaning multi-screw extruder with a speed ratio of 2.5 and an extruding method therefor are disclosed. The screw mechanism includes a center screw and peripheral screws which rotate in the same direction. The peripheral screws are each of a double threaded structure, and the center screw is of a quintuple threaded structure. The rotation speed of the peripheral screws is 2.5 times that of the center screw, and the peripheral screws are always meshed with the center screw, whereas the adjacent peripheral screws are intermittently meshed with each other. The extruding method therefor is as follows: there is a periodically open space between adjacent peripheral screws, providing the periodical and intermittent mixing action, so that material from different thread grooves is mixed with each other. Meanwhile, the topological chaos action, by which the material is cut into two portions, is formed between the center screw and the peripheral screws, and the chaos mixing is caused by the random motion which is generated from the periodical changes of the channel, so that a periodical action of “compression-expansion” is achieved. Furthermore, due to the tensile force field action caused by the differences in rotation speed between the center screw and the peripheral screws, the compression preheating and dispersion mixing of the material are achieved. The co-rotating self-cleaning multi-screw extruder effectively improves the efficiency of conveying and mixing of materials.