Plastic Ring Fan Geometry to Strengthen Injection Mold Weld Lines
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Solution Overview
Problem
Plastic or fiber reinforced plastic molded ring fans in cooling systems fail due to stress along weld lines or knit lines formed during injection molding, which are weak points under increased rotational speeds and cooling demands.
Innovation Solution
The location of weld or knit lines is moved to less stressed areas by forming meld lines where molten material flows meet at angles other than 180 degrees, and glass fiber reinforcement is improved along these lines through thickness variations and spillover-type reservoirs to prevent direct collisions and impurity accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If injection molding is used to manufacture plastic ring fans, then manufacturing efficiency and cost are improved, but weld lines or knit lines form during the process creating weak points that reduce fan reliability
Solution Approach 1:
The patent changes the geometric parameters of the mold cavity, specifically varying the thickness of the ring in different sections. This parameter change alters the flow pattern of molten material during injection molding, causing flow fronts to meet at angles other than 180 degrees and form meld lines instead of weak knit lines, thereby maintaining manufacturing efficiency while improving reliability
Solution Approach 2:
The patent introduces asymmetry into the previously symmetric ring structure by creating non-uniform thickness variations. The ring thickness is increased in specific sections to control material flow, creating asymmetric flow patterns that prevent direct head-on collision of flow fronts and eliminate weak knit lines while preserving the overall ring fan functionality
2Productivity
If rotational speed and airflow capacity are increased to meet cooling demands, then cooling performance is improved, but stress on the fan ring increases causing failure at weld lines
Solution Approach 1:
The patent modifies the geometric parameters of the ring structure by varying its thickness in different sections. This creates meld lines with improved material intermingling and enhanced structural strength that can withstand the increased centrifugal forces and stress generated at higher rotational speeds, allowing the fan to achieve greater cooling capacity without failing at weak points
Solution Approach 2:
The patent utilizes fiber-reinforced plastic materials with varying fiber orientations and concentrations in different ring sections. The fiber reinforcement, combined with the controlled meld line geometry, creates a composite structure with enhanced strength-to-weight ratio that can handle the increased mechanical loads from high-speed operation while maintaining the required cooling performance
Data Source
AI summary
Injection molded ring fan embodiments and methods for making them. The methods influence material flow during the injection molding process such that a major portion of the materials flowing in opposite directions in the outer rings preferably flow past one another, intermix in a swirling relationship, and/or collide at an angle relative to one another. This results in better material mixing or integration of the flow fronts. In one embodiment, the thickness of the outer ring varies in different portions between adjacent fan blades.