Spiral Distributor Design for Blown Film Homogeneity
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Solution Overview
Problem
Existing die heads with axial spiral distributors suffer from long sojourn times of the melt in the gusset area due to geometric design, leading to thermal degradation and non-homogeneous foil structures, resulting in flaws like 'spiral strips' and color changes.
Innovation Solution
The spiral distributor design is modified by altering the initial section of the spiral channels to increase flow speed, with features such as angled starts, deviations, and changes in cross-sectional geometry to reduce wall shear stresses and facilitate better melt distribution, including overflow facilitators to enhance melt flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the spiral channels are designed with conventional geometry in the gusset area, then the melt flow is stable, but the sojourn time becomes too long causing thermal degradation and non-homogeneous foil structure
Solution Approach 1:
The patent applies local quality by creating different geometric characteristics at different locations within the spiral channel. Specifically, the initial section of the spiral channel has a different cross-sectional geometry compared to the subsequent sections, with the initial section having larger dimensions to reduce wall shear stresses and shorten sojourn time in the critical gusset area while maintaining stable flow elsewhere.
Solution Approach 2:
The patent changes geometric parameters (cross-sectional dimensions, channel shape) along the length of the spiral channel. The initial section has specific dimensional parameters that differ from the downstream sections, allowing optimization of flow characteristics at different positions to balance stability and reduce sojourn time.
2Device complexity
If the spiral channels have conventional geometry, then the structure is simple, but wall shear stresses are high causing thermal degradation and spiral strips
Solution Approach 1:
The patent applies local quality by creating different geometric characteristics at different locations within the spiral channel. Specifically, the initial section of the spiral channel has a different cross-sectional geometry compared to the subsequent sections, with the initial section having larger dimensions to reduce wall shear stresses in the critical gusset area while maintaining stable flow elsewhere.
3Stability of the object's composition
If the melt sojourn time is extended in the gusset area, then the melt can fully distribute, but thermal degradation occurs leading to color changes and spiral strips
Solution Approach 1:
The patent changes geometric parameters (cross-sectional dimensions, channel shape) along the length of the spiral channel. The initial section has specific dimensional parameters that differ from the downstream sections, allowing optimization of flow characteristics at different positions to balance distribution and reduce sojourn time.
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 modified design reduces sojourn times, improves thermal homogeneity, and prevents flaws like spiral strips, resulting in a more homogeneous foil structure and reduced rinsing time with consistent color.
Implementation Method 1
altering the initial section of the spiral channels to increase flow speed, with features such as angled starts, deviations, and changes in cross-sectional geometry to reduce wall shear stresses
Implementation Method 2
reduces sojourn times, improves thermal homogeneity, and prevents flaws like spiral strips
Data Source
AI summary
Foil extrusion lines use spiral distributors for producing a melt which is as homogeneous as possible during operation. The spiral distributors are mostly available as cylindrical or conical axial spiral distributors or as radial spiral distributors. The spiral distributors have spiral channels that run in a multiple spiral arrangement so that rather flat horizontal edges are formed precisely in initial sections and vertical edges are formed between the beginning of spiral channels and transition sections of adjacent spiral channels. The melt can easily adhere there. To accelerate the melt in critical areas, the course or the cross-section of the channels or the surface are modified.