Injection Molding Screw Backflow Mechanism for Fiber Dispersion
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Solution Overview
Problem
Existing injection molding techniques face challenges in uniformly dispersing reinforcing fibers within resin due to excessive shear force, leading to uneven distribution and fiber breakage, especially at high fiber content percentages.
Innovation Solution
A screw design for injection molding machines that incorporates a backflow mechanism in the screw groove, allowing molten resin to flow backward and promote the opening of fiber masses, thereby reducing shear force on the fibers and ensuring uniform dispersion without excessive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If mixing conditions are made severe to strengthen shear force on reinforcing fibers, then uniform dispersion of fibers is improved, but fiber breakage occurs and fiber length is significantly reduced
Solution Approach 1:
The screw groove is divided into a resin storage groove and a fiber mixing groove, separating the functions of resin accumulation and fiber mixing. This segmentation allows the resin to be stored in one region while fibers are mixed in another, reducing excessive shear force on fibers while maintaining dispersion uniformity.
Solution Approach 2:
Different regions of the screw groove are given different functions: the resin storage groove accommodates molten resin with lower shear stress, while the fiber mixing groove provides controlled mixing for fibers. This local differentiation of groove characteristics optimizes both fiber dispersion and fiber length preservation.
2Length of moving object
If shear force is weakened to prevent fiber breakage, then fiber length is maintained, but uniform dispersion of reinforcing fibers cannot be achieved
Solution Approach 1:
By segmenting the screw groove into distinct resin storage and fiber mixing regions, the system provides adequate mixing action in the fiber mixing groove while the resin storage groove protects fibers from excessive shear. This enables both fiber length maintenance and uniform dispersion.
Solution Approach 2:
The resin acting in the fiber mixing groove serves as an intermediary that facilitates fiber dispersion through controlled interaction, while the resin storage groove provides a buffer zone that prevents direct excessive shear on fiber masses, enabling dispersion without breakage.
3Stability of the object's composition
If a feeder mechanism is added to forcibly feed reinforcing fibers, then fiber dispersion is improved, but device complexity increases and mass of fiber aggregates remains
Solution Approach 1:
The screw groove structure performs multiple functions: it stores resin, mixes fibers, and controls fiber feeding all within the existing injection molding mechanism. This multi-functionality achieves improved fiber dispersion without adding separate feeder mechanisms, reducing device complexity.
Solution Approach 2:
The resin and fibers utilize the screw groove structure itself for mixing and dispersion through the natural plasticizing and injection process. The system serves itself by using the existing screw rotation and resin flow to achieve fiber dispersion without requiring additional active feeding mechanisms.
4Strength
If high content of reinforcing fibers (not less than 10%) is used, then strength enhancement is achieved, but uniform dispersion becomes difficult
Solution Approach 1:
The segmented groove structure provides dedicated space for high fiber content mixing in the fiber mixing groove while maintaining resin storage capacity. This allows high fiber concentrations (≥10%) to be uniformly dispersed without compromising the resin matrix, enabling strength enhancement with uniform distribution.
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 solution effectively eliminates uneven distribution of reinforcing fibers, ensuring they are uniformly dispersed within the resin, maintaining fiber length and enhancing the mechanical properties of molded products without excessive shear-induced breakage.
Implementation Method 1
thermoplastic resin is melted by rotation of a screw in a cylinder serving as a plasticizing device
Implementation Method 2
thermoplastic resin is melted by rotation of a screw in a cylinder serving as a plasticizing device
Implementation Method 3
a backflow of the melted resin raw material is generated from a screw groove of a downstream side toward a screw groove of an upstream side of the screw
Implementation Method 4
fibers are mixed in or kneaded with the melted thermoplastic resin
Data Source
AI summary
There is provided a screw of an injection molding machine that can eliminate uneven distribution of reinforcing fibers without giving an excessive shear force to the reinforcing fibers. A screw is provided inside a heating cylinder of an injection molding machine to which a resin pellet is fed on an upstream side in a conveyance direction of resin and to which reinforcing fibers are fed on a downstream side therein, and includes: a first stage at which the resin pellet which is fed is melted; and a second stage that continues to the first stage, and at which molten resin and the reinforcing fibers are mixed with each other. A second flight provided at the second stage includes: a large-diameter flight with a relatively large outer diameter; and a small-diameter flight with a relatively small outer diameter.