Plastic fans having improved fan ring weld line strength

A method for improving outer ring strength of a fan used in a fan drive system, the fan having a plurality of fan blades coupled between the outer ring and an inner ring, the method comprising:

• forming a prototype mold having an interior, said interior corresponding to the size and shape of the fan, wherein the thickness of the outer ring is constant, said mold having a plurality of gates located around the inner ring, one of the plurality of gates closely coupled to the inner ring at a position corresponding to one of the plurality of fan blades;
• introducing to said prototype mold a quantity of a molten plastic material simultaneously through each of the plurality of gates and within said interior at a desired temperature and pressure;
• cooling said quantity of molten plastic material within said prototype mold to form a prototype fan;
• and
• determining a location of a weld line along the outer ring between each respective adjacent pair of the plurality of fan blades within said prototype fan, said weld line corresponding to a weakest portion of the outer ring of said prototype fan between each respective adjacent pair of the plurality of fan blades, wherein said weakest portion of the outer ring is formed at a position wherein a first flow front of a portion of said quantity of molten raw material collides with a second flow front of a second portion of said quantity of molten plastic material, said first flow front flowing substantially in a first direction along the outer ring from one of the adjacent pair of the plurality of fan blades towards an other of the adjacent pair of the plurality of fan blades and wherein said second flow front flowing substantially in a second direction along the outer ring from said an other of the adjacent pair of the plurality of fan blades to said one of said adjacent pair of the plurality of fan blades;
• reshaping said interior between at least one of the respective adjacent pair of the plurality of fan blades of said prototype mold to form a mold;
• introducing to said mold a second quantity of a molten plastic material simultaneously through each of the plurality of gates and within said interior at a desired temperature and pressure, wherein a third portion of said second quantity of molten plastic material flows between said one of said respective adjacent pair of the plurality of fan blades and said other of said respective adjacent pair of the plurality of fan blades in substantially a third direction and a fourth portion of said second quantity of molten plastic material flows between said other of said respective adjacent pair of the plurality of fan blades and said one of said respective adjacent pair of fan blades in substantially a fourth direction, said third portion colliding with said fourth portion with the outer ring between said adjacent pair of the plurality of fan blades at an angle A defined as the angle between said third direction and said fourth direction;
• cooling said quantity of molten raw material within said mold to form the fan;
• and
• removing the fan from said mold.