Foamed Plastic Static Mixer Injection Molding
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Solution Overview
Problem
Conventional injection molding processes struggle to produce static mixers with wall thicknesses less than 3 mm and length-to-thickness ratios greater than 10 due to high mold cavity pressures and the formation of sink marks, limiting the production of thin-walled mixers with complex geometries.
Innovation Solution
The use of foamed plastic with a blowing agent, such as supercritical CO2, reduces viscosity and allows for lower mold cavity pressures, enabling the production of static mixers with significantly higher length-to-thickness ratios by creating a foamed structure with cell sizes less than 100 μm, which reduces internal mold pressure and prevents premature mold failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional injection molding is used to produce thin-walled static mixers, then manufacturing capability is maintained, but high mold cavity pressures exceed permissible limits causing premature mold failure
Solution Approach 1:
The patent applies parameter changes by modifying the physical state of the polymer material from solid to foamed structure. By introducing a blowing agent that creates foam cells during injection molding, the material parameters change: density decreases, volume increases, and crucially, mold cavity pressure is reduced to permissible levels while maintaining thin wall thicknesses and high length-to-thickness ratios
Solution Approach 2:
The patent uses composite materials by combining polymer with a blowing agent to create a foamed plastic composite. This composite structure consists of polymer matrix with dispersed gas cells, providing both structural integrity and reduced pressure during molding, enabling production of thin-walled mixers with length-to-thickness ratios greater than 10
2Manufacturing precision
If high internal mold pressures are applied to fill thin-walled mixers, then complete filling is achieved, but sink marks form on the mixer surface
Solution Approach 1:
The foamed plastic parameter change resolves the sink mark problem by reducing the density and weight of the material. The foam structure provides internal support that prevents surface collapse during cooling, maintaining smooth surfaces on thin walls without requiring excessive mold cavity pressures that would cause sink marks
3Productivity
If the length-to-thickness ratio is increased beyond conventional limits, then mixing performance improves, but mold pressure exceeds permissible limits
Solution Approach 1:
The foamed plastic composite material enables extended length-to-thickness ratios by providing structural support through the foam cell network. The composite structure maintains rigidity and prevents collapse over longer lengths while keeping wall thicknesses thin, achieving length-to-thickness ratios greater than 10 without exceeding mold pressure limits
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 allows for the economical production of static mixers with wall thicknesses less than 3 mm and length-to-thickness ratios exceeding 50, enabling the manufacture of longer, thinner mixers with improved mixing performance and reduced material costs.
Implementation Method 1
The blowing agent-containing polymer has a lower viscosity than a comparable polymer without a blowing agent, since the viscosity of the polymer is reduced by the blowing agent
Implementation Method 2
the plastic used is a blowing agent-containing polymer, which is foamed during the injection molding process, so that after completion of the injection molding process, an insert is present that consists at least partially of foamed plastic
Implementation Method 3
a polymer melt can be used that contains a physical, especially a supercritical gas such as CO2
Implementation Method 4
The foamed plastic has cells with a cell size of less than 100 μm, whereby a cell density of at least approximately 106 cells/cm3 can be provided. The ratio of flow path to wall thickness is at least 10... The ratio of length to diameter can be greater than 3... In particular, static mixers with a large overall length can be manufactured economically due to the significantly lower mold pressure
Implementation Method 5
The blowing agent is then mixed with the polymer melt in the plasticizing cylinder by the plasticizing screw. This mixing process increases the subsequent diffusion of the blowing agent into the polymer until the polymer is saturated with blowing agent
Implementation Method 6
As long as the plasticizing screw rotates, it generates a two-dimensional shear field in the blowing agent/polymer system being mixed. This stretches the bubbles formed by the blowing agent in the shear direction. The stretched bubbles are then broken up into smaller spherical bubbles by perturbation of the laminar flow
Implementation Method 7
Following diffusion, the solution is rapidly heated, causing nucleation in the saturated solution. Nucleation refers to the formation of nucleated cells, which forms the basis for the development of the foam with a mean cell size of up to 100 μm
Data Source
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AI summary
A process for manufacturing a static mixer by injection molding comprises the following steps: injecting a blowing agent-containing polymer melt into a channel at an injection point at an injection pressure of less than 500 bar, filling the channel with the blowing agent-containing polymer melt, and at least partially foaming the blowing agent-containing polymer melt in the channel, wherein the ratio of flow path to wall thickness is at least 10. A static mixer comprising an insert (1, 101) for installation in a tubular mixer housing is manufactured using an injection mold suitable for the process. The insert (1, 101) has a length dimension (24) and a diameter (36). The ratio of length dimension (24) to diameter is greater than 1, and the insert (1, 101) consists at least partially of foamed plastic. The ratio of length dimension (24) to wall thickness (7) is at least 10.The installation body (1,101) consists at least partially of foamed plastic, with a ratio of flow path to the wall thickness of the installation body (1,101) of at least 10.