Co-rotating Screw Mixing Elements with Segmented Geometry
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Solution Overview
Problem
Existing multi-screw extruders face challenges in achieving optimal dispersion of gaseous, liquid, or solid additives, leading to inhomogeneities in plastic masses and reduced product quality, with current mixing elements requiring increased energy input and reduced throughput to compensate for poor dispersion.
Innovation Solution
The development of mixing elements with an increased number of basic geometry periods per length section, specifically designed for co-rotating multi-screw extruders, featuring a return conveying element with conveying grooves, where the pitch of the grooves is at least 7 times the outer diameter, enhancing dispersion efficiency with reduced energy input and increased throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mixing elements with fewer basic geometry periods per length section are used, then device complexity is reduced, but dispersion quality deteriorates leading to inhomogeneous plastic masses
Solution Approach 1:
The mixing element is divided into multiple basic geometry periods (at least 5.5 periods per outer diameter length section) along the axial direction. Each period contributes to the overall dispersion function, creating a segmented approach to achieving homogeneous mixing without requiring excessive complexity in any single geometric feature.
Solution Approach 2:
The invention increases the number of basic geometry periods along the axial dimension while maintaining appropriate groove pitch ratios. This dimensional approach allows improved dispersion quality by distributing mixing action throughout the length of the mixing element, rather than relying solely on increased groove density or larger element size.
2Manufacturing precision
If mixing elements with increased number of basic geometry periods are used, then dispersion quality improves, but energy consumption increases
Solution Approach 1:
The invention optimizes the groove pitch parameter to be at least 7 times the outer diameter of the mixing element. This specific parameter ratio creates an efficient mixing action that achieves superior dispersion quality while minimizing the energy required for the mixing process, balancing performance with energy consumption.
Solution Approach 2:
The multiple basic geometry periods (≥5.5 per outer diameter length) create continuous mixing action along the axial direction. This continuous useful action ensures that dispersion occurs progressively throughout the mixing element length, achieving homogeneous plastic masses without requiring excessive energy input at any single point.
3Manufacturing precision
If conventional mixing elements are used, then throughput is maintained, but dispersion quality deteriorates requiring speed reduction to compensate
Solution Approach 1:
The mixing element is segmented into at least 5.5 basic geometry periods per outer diameter length section, with each period contributing to the dispersion process. This segmentation allows the mixing action to be distributed efficiently, achieving homogeneous plastic masses at higher throughput rates without requiring speed reductions.
Solution Approach 2:
By setting the groove pitch to at least 7 times the outer diameter, the invention creates optimal mixing conditions that maintain high throughput capability. This parameter optimization ensures that dispersion quality improves while productivity is preserved, eliminating the need to reduce operating speed to achieve homogeneity.
Data Source
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AI summary
The invention relates to mixing elements that have a larger number of basic geometric periods per longitudinal section and an improved dispersing effect for multi-shaft screw extruders comprising screw shafts that co-rotate in pairs. The invention further relates to the use of the mixing elements in multi-shaft screw extruders, a corresponding screw extruder comprising the mixing elements, and a method for extruding kneadable materials.