Abstract: 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.

Abstract: A method to influence material flow during the injection molding of thermoplastic, polymeric ring type fans such that a major portion of the materials flowing in opposite directions preferably flow past one another, or collide at an angle relative to one another, rather than colliding at an 180 degree angle relative to each other to form weld lines. This flow bypassing results in better material mixing or integrating than merely allowing flow fronts to collide and cool. In one embodiment, a portion of the fan's ring is thickened in the weld line area to minimize the amount of material colliding at a 180-degree angle relative to each. Alternatively, at least one appendage could be added to the ring fan that will influence the material flow during molding conditions. Each appendage will be removed prior to introducing the ring fan to a cooling system.