Elliptical Kneading Element for Ceramic Honeycomb Extrusion
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Solution Overview
Problem
Existing ceramic honeycomb extrusion processes face challenges in achieving uniform mixing and flow, leading to defects such as bow variability, end of log tilt, and internal tears due to non-uniform rheology and temperature fluctuations, which affect the quality and consistency of the honeycomb bodies produced.
Innovation Solution
The use of a kneading element with a continuous closed curve elliptical outer surface and a specific screw geometry, including high pitch-to-diameter ratios in the backup length region, balances radial and axial forces to promote uniform mixing and flow, reducing shear and temperature gradients, and optimizing screw configurations to improve extrudate quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional screw elements are used for extruding ceramic batch materials, then the extrusion process can be maintained, but non-uniform mixing and flow occur leading to defects such as bow variability, end of log tilt, and internal tears
Solution Approach 1:
The screw element is divided into multiple distinct functional zones: a pumping section with standard helical geometry for material transport, and a kneading section with intermeshing lobes for intensive mixing. This segmentation allows each zone to perform its specific function optimally, resolving the contradiction between maintaining extrusion capability and achieving uniform mixing.
Solution Approach 2:
The kneading lobes are designed with curved, elliptical cross-sections that continuously vary in shape along the axial direction. This curvature creates progressive shear zones and eliminates dead spots in the mixing chamber, ensuring uniform batch material processing and preventing flow defects that lead to bow variability and end of log tilt.
2Manufacturing precision
If high pitch-to-diameter ratios are used in the backup length region, then radial and axial forces are balanced to promote uniform mixing, but the screw geometry becomes more complex
Solution Approach 1:
The screw element features locally optimized geometry where the pitch-to-diameter ratio is specifically increased in the backup length region (kneading section) while the pumping section maintains conventional dimensions. This local modification balances radial and axial forces precisely where needed for uniform mixing without unnecessarily complicating the entire screw geometry.
Solution Approach 2:
The screw element incorporates variable pitch and variable diameter along its axial length, transitioning from a standard pumping geometry to an optimized kneading geometry. This dynamic variation in geometric parameters allows the screw to adapt its force distribution and mixing intensity to the local process requirements, achieving uniform extrudate with controlled complexity.
3Ease of manufacture
If conventional mixing is used, then the extrusion process is simple, but temperature fluctuations and shear gradients occur affecting extrudate quality
Solution Approach 1:
The kneading element design ensures continuous, progressive mixing action through the backup length region with no dead zones or recirculation areas. The intermeshing lobes create a continuous shear field that uniformly processes the batch material, eliminating temperature fluctuations and shear gradients that would otherwise affect extrudate quality while maintaining process simplicity.
4Ease of operation
If the opening axis is off-center with respect to the geometric center, then the kneading element can be coupled to the shaft, but the geometry becomes asymmetric
Solution Approach 1:
The kneading element deliberately incorporates asymmetric geometry with an off-center opening axis relative to the geometric center of the elliptical cross-section. This asymmetry enables practical shaft coupling and positioning while the overall elliptical shape and lobe configuration maintain balanced hydrodynamics. The asymmetric feature is localized to the mounting interface, not the functional mixing geometry.
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 results in improved uniformity of the ceramic batch, reduced flow defects, and enhanced extrudate quality, including reduced bow variability and end of log tilt, leading to better thermal and shear uniformity, and increased manufacturing efficiency.
Implementation Method 1
reducing shear and temperature gradients
Implementation Method 2
kneading ceramic batch in a screw extruder machine; and extruding the batch through a die
Data Source
AI summary
Kneading elements, extrusion apparatus, and methods of manufacturing honeycomb bodies are described herein. A kneading element (1802) has an inner surface (1804) defining an opening (1806) configured to couple the kneading element (1802) to a shaft (46,48). The kneading element (1802) also has a continuous closed curve elliptical outer surface (1808). The opening (1806) has an axis (1814) that is off-center with respect to a geometric center (1816) of the kneading element (1802) as viewed in a transverse plane perpendicular to the axis.