Notched Feed Screw Wedge Design for Resin Pellet Entrapment
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Solution Overview
Problem
In injection molding machines, resin pellets often become entrapped between the screw flight and the cylindrical inner wall of the molding material supply device, causing increased load on the rotating screw, potential crushing or scraping, and defective molding due to the pellets being pushed into the gap, which is not effectively addressed by conventional notches that reduce feeding force and lead to further entrapment issues.
Innovation Solution
A molding material feed screw with a sharp-angled, wedge-shaped portion and a notched region on its outer periphery, where the outer diameter is smaller towards the front and larger towards the rear, is designed to create a large gap between the screw flight and the inner wall, preventing resin pellets from being pushed into the gap and reducing entrapment by pushing them aside.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap between the screw flight and cylindrical inner wall is reduced to ensure stable transport, then transport stability is improved, but resin pellets become entrapped between the screw flight edge and material supply port edge
Solution Approach 1:
The screw flight is segmented into multiple regions along the axial direction, with each region having a different outer diameter. The first region (near the material supply port) has a smaller outer diameter to prevent entrapment, while the second region has a larger outer diameter to ensure stable transport, creating a step-like structure that resolves the contradiction between preventing entrapment and ensuring stable transport.
Solution Approach 2:
Different portions of the screw flight are given different local properties: the first portion near the material supply port has a smaller outer diameter specifically tailored to prevent pellet entrapment in that critical zone, while the second portion has a larger outer diameter optimized for stable transport. This local differentiation allows each region to perform its specific function optimally.
2Object-affected harmful factors
If a notch is formed in the screw flight outer periphery to prevent entrapment, then entrapment is reduced, but feeding force decreases and resin pellets continue to rotate with the screw
Solution Approach 1:
Instead of a static notch that reduces feeding force, the invention uses a dynamic step-like structure where the outer diameter changes along the axial direction. This creates a moving boundary effect during screw rotation, where resin pellets are pushed by the larger-diameter portion and redirected by the step edge, preventing continuous rotation while maintaining strong feeding force.
Solution Approach 2:
The solution moves from a two-dimensional notch (cutting out material in the radial direction) to a three-dimensional step-like structure that varies the outer diameter along the axial dimension. This adds a new dimension to the problem solution, creating a more effective mechanism for preventing pellet rotation while maintaining feeding force.
3Productivity
If the screw flight outer diameter is increased to improve feeding force, then feeding capability is improved, but resin pellets are pushed into the gap and entrapment increases
Solution Approach 1:
The screw flight is divided into axial segments with different outer diameters. The first segment has a smaller outer diameter positioned at the critical entrapment zone near the material supply port, preventing pellets from being pushed into the gap, while the second segment has a larger outer diameter that provides strong feeding force in the transport zone.
Solution Approach 2:
The screw flight exhibits local quality variation along its axial length, with the outer diameter being smaller at the material supply port end and larger at the transport end. This local differentiation allows the screw to simultaneously prevent entrapment at the critical interface while maintaining strong feeding capability in the transport region.
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 design effectively suppresses the entrapment of resin pellets, reducing the load on the screw and preventing foreign objects in the molding process, while maintaining sufficient force for pellet transfer by minimizing the outer diameter of the screw flight in the notched region.
Implementation Method 1
A sharp-angled, wedge-shaped portion is formed in the outer periphery of the screw flight of the molding material feed screw in the vicinity of the location of the front end of the edge of the first molding material supply port
Implementation Method 2
A molding material feed screw 24 driven by a driving device such as a motor 21 is rotatably arranged within the molding material supply device 20. This molding material feed screw 24 has spiral grooves formed therein by providing a screw flight 40.
Data Source
AI summary
A notched region in which the outer periphery of a screw flight is cut out is provided in a molding material feed screw. A wedge-shaped portion is formed by both a front wall surface of the screw flight and a wall surface of the boundary where the outer periphery of the screw flight is cut out. As a result of rotation of the molding material feed screw, since the wedge-shaped portion advances while pushing aside resin pellets located in the front thereof in two lateral directions of the front wall surface of the screw flight and the wall surface of the boundary where the outer diameter of the screw flight is cut out, entrapment of the resin pellets between the edge of a material supply port of a molding material supply device and the outer periphery of the screw flight is avoided as much as possible.